Liquid Nanoclay: Synthesis and Applications to Transform an Arid Desert into Fertile Land

Abstract

Nanoclay, a processed clay, is utilized in numerous high-performance cement nanocomposites. This clay consists of minerals such as kaolinite, illite, chlorite, and smectite, which are the primary components of raw clay materials formed in the presence of water. In addition to silica, alumina, and water, it also contains various concentrations of inorganic ions like Mg²⁺, Na⁺, and Ca²⁺. These are categorized as hydrous phyllosilicates and can be located either in interlayer spaces or on the planetary surface. Clay minerals are distinguished by their two-dimensional sheets and tetrahedral (SiO₄) and octahedral (Al₂O₃) crystal structures. Different clay minerals are classified based on the presence of tetrahedral and octahedral layers in their structure. These include kaolinite, which has a 1:1 ratio of tetrahedral to octahedral layers, the smectite group of clay minerals and chlorite with a 2:1 ratio. Clay minerals are unique due to their small size, distinct crystal structure, and properties such as high cation exchange capacity, adsorption capacity, specific surface area, and swelling behavior. These characteristics are discussed in this review. The use of nanoclays as nanocarriers for fertilizers boasts a diverse array of materials available in both anionic and cationic variations. Layered double hydroxides (LDH) possess a distinctive capacity for exchanging anions, making them suitable for facilitating the transport of borate, phosphate, and nitrate ions. Liquid nanoclays are used extensively in agriculture, specifically as fertilizers, insecticides, herbicides, and nutrients. These novel nanomaterials have numerous benefits, including improved nutrient use, controlled nutrient release, targeted nutrient delivery, and increased agricultural productivity. Arid regions face distinct challenges like limited water availability, poor soil quality, and reduced productivity. The addition of liquid nanoclay to sandy soil offers a range of benefits that contribute to improved soil quality and environmental sustainability. Liquid nanoclay is being proposed for water management in arid regions, which will necessitate a detailed examination of soil, water availability, and hydrological conditions. Small-scale trial initiatives, engagement with local governments, and regular monitoring are required to fully comprehend its benefits and drawbacks. These developments would increase the practicality and effectiveness of using liquid nanoclay in desert agriculture.

1. Introduction

Clays are classified into several classes such as kaolinite, halloysite, chlorite, smectite, and illite, depending on their chemical composition and particle morphology [1]. Nanoclays have been extensively researched and developed for various applications due to their wide availability, relatively low cost, and minimal environmental impact [2]. The swift progress of nanotechnology has resulted in an increased use of clay minerals as natural nanomaterials [3]. Nanoclays are nanoparticles made up of layered mineral silicates. These can create intricate clay crystallites through the process of layer stacking [4]. Each layer consists of either octahedral or tetrahedral sheets [5]. A plane of aluminum or magnesium ions lies in between the two planes of hydroxyl ions, which are octahedrally coordinated by hydroxyl sheets. When these octahedrons are arranged in a hexagonal pattern, they are called octahedral sheets [6]. The tetrahedral sheets are composed of silicon–oxygen tetrahedra and connect to neighboring tetrahedra by sharing three corners. Each tetrahedron in the sheet links its fourth corner to an adjacent octahedral sheet through a covalent bond [7]. The arrangement of these sheets significantly influences the defining and distinguishing characteristics of nanoclays. Around 30 different types of nanoclays exist, each possessing unique properties based on their mineralogical composition. These properties determine their specific applications [8]. Common nanoclay materials exhibit two major sheet arrangements: 1:1 and 2:1. In a 1:1 structure, each tetrahedral structure is linked to one octahedral sheet. Conversely, in a 2:1 structure, each octahedral sheet is linked to two tetrahedral sheets, situated on both sides [9,10].

Nanoclay is an innovative nanomaterial that has shown potential in reducing porosity and pore size in cement matrices, as well as improving their strength [11]. It offers numerous benefits, including enhanced flame resistance, tensile strength, modulus, and structural and thermal properties. It is also considered to be a sustainable material due to its fascinating properties. The platelet size of nanoclays, which ranges from 10 to 100 nm, allows them to act as reinforcements in rubbers and other polymers, making them less flammable [12,13]. These versatile materials are composed of phyllosilicates, compounds that contain silicon, oxygen, and other elements. After further processing, nanoclays are incorporated into various products due to their unique properties. Their layered structure enables them to swell or shrink as water is either absorbed or withdrawn between the layers. This can increase their volume by up to six times, forming stable gels. The global market for nanoclays is steadily increasing and was projected to be valued at over USD 3.3 billion by 2023 [14].

Nanoclays possess unique properties that make them useful in various sectors, including transforming desert sand into fertile land [15]. They play a significant role in the creation of new materials, particularly polymer/nanoclay composites [16]. Furthermore, nanoclay reinforcement is employed in green polymeric nanocomposites to achieve specific characteristics [12]. Nanoclay and its nanocomposites have good adsorption capacity and have been modified to separate the pollutants, notably, heavy metals (Cd, Pd, Co, Cu, As, Hg, Ni, Zn, and Cr), ammonia, nitrate, fluoride, dyes, bacteria, and other emerging pollutants (personal care products, pharmaceuticals, and pesticides) [17]. It plays a crucial role in various sectors including environmental remediation, biomedicine, water treatment, COVID-19 antibody development, cancer therapy, tissue engineering, electrochemical energy production, energy storage and conversion, automotive industry, photocatalysis, nanorobotics, nanocatalysis, and 3D printing, as well as showing remarkable results against biotic and abiotic stress conditions [14,18,19]. It is used to stabilize problematic soils due to their low specific gravity, high surface area, and fine particles, making them an ideal eco-friendly stabilizer and helpful for geotechnical engineers [19,20]. It is also utilized in food packaging and to enhance mechanical and barrier properties. However, concerns regarding nanoclay migration, toxicity levels, and associated legislation need to be addressed [14]. Montmorillonite, bentonite, halloysite nanoclays, and organoclays are incorporated into polymer–clay nanocomposites. Natural nanoclays are found in soil fractions, with montmorillonite and allophane being the most significant species [21].

Nanostructures based on nanoclay display substantial structural, morphological, thermal, mechanical, and barrier properties [18]. Owing to their distinctive nano-scale structure, nanoclays function as superior nanofillers in polymeric matrices for the development of nanomaterials [22]. To improve the compatibility of inorganic nanoclays with organic polymers, layered silicates are commonly modified using alkyl cations. This process leads to the formation of organoclays [23]. These polymer/nanoclay nanocomposites exhibit characteristics like mechanical strength, thermal stability, and flame resistance.

Research in the field of nanocomposites has largely focused on integrating organic or inorganic nanofillers into polymeric matrices [24]. Nanoclay, a unique inorganic nanofiller, is recognized as beneficial for hybrid polymer nanocomposites [25]. The standard structure of nanoclay consists of two-dimensional silica tetrahedral nanosheets connected to alumina octahedral nanosheets. In these nanoclays, a single silicate layer is about 0.7 nm thick, while a double layer is roughly 1 nm thick. The distance between the nanoclay platelets suggests relatively weak van der Waals interactions based on the clay [26]. Layered silicates typically have limited interaction with polymer chains due to their hydrophilic nature [27].

To improve the organophilic nature of nanoclays, adjustments are often made to the interlayer spacing using exchangeable ions, organic molecules, or surfactants. The nanoclay nanosheet surface carries a negative charge due to its inherent silicate structure, which aids in accommodating an exchangeable cation layer (Na⁺, K⁺, Mg²⁺, and Ca²⁺ etc.) within the interlayer spacing. Consequently, the charge exchange capacity of these layered silicates has been extensively studied [28]. The layered silicate nanosheets, also known as nanoclays, exhibit an electrical conductivity range of 25–100 mSm⁻¹ due to their surface charge [29,30]. In nanoclays, the interlayer spacing can be expanded for improved compatibility with polymeric chains. This is accomplished by inserting organic cations (aliphatic chains attached to -NH₃⁺) into the nanoclay galleries [31,32]. Various synthetic polymers, including polystyrene, epoxy, polyurethane, and polyamide have been utilized as matrices for nanoclay nanofillers [33]. The major goal of this article is to show how to synthesize, describe, and deploy liquid nanoclay for preventing desertification and enhancing agricultural output in dry areas. It will discuss the various benefits, applications, and challenges of using liquid nanoclay for desert restoration, such as its ability to retain water, enhance soil structure, and encourage plant growth. The essay might also go over the environmental and financial implications of employing this technology for long-term arid land restoration.

2. Properties and Structure of Nanoclay and Clay

Structure of Nanoclay

Clay materials are formed from the weathering of feldspar rocks and consist of alkaline earth, alkali metals, iron, magnesium, and various cations. They are categorized as 1:1 (kaolinite) and 2:1 (montmorillonite, vermiculite, mica, and chlorite) comprised of alternative sheets of SiO₂ and AlO₆ units. They have thin, plate-like crystals with aspect ratios of 100 to 1000 and nanometer-scale thickness. Weak van der Waals and electrostatic forces bind these nano-platelets together, creating an “Interlayer” with negative charges balanced by cations such as Na⁺, K⁺, Mg²⁺, or Ca²⁺ [34].

3. Characteristics of Cement-Based Materials Utilizing Calcined Nanoclay and Nanoclay

3.1. Workability

The incorporation of nanoclay or calcined nanoclay into cement-based materials has a significant impact [35,36,37]. It decreases the fluidity of the cement paste, particularly when higher amounts of nanoclay are used [38]. This is due to the high specific surface area of nanoclay, which necessitates more water for standard consistency, resulting in a drier mixture and significantly reduced flowability. Furthermore, the addition of nanoclay or calcined nanoclay shortens the setting times of cement pastes. This can be attributed to the enhancement of cement hydration and the formation of a considerable amount of hydrates. The introduction of nanoclay materials significantly alters the flow properties and setting times of cement-based materials [38,39].

3.2. Mechanical Properties

3.2.1. Strength Enhancement

Research indicates that incorporating nanoclays or calcined nanoclays substantially improves the strength of cement-based materials. The enhancement is due to their ultra-fine particle size, high pozzolanic activity, and nucleation effects [37,40,41]. Optimal content ranges exist for different types of nanoclay particles, such as 5–10% for nano-kaolin and 0.5–3% for nanomontmorillonite, ensuring the highest strength.

3.2.2. Elastic Modulus

Incorporating an optimal amount of nanoclay or calcined nanoclay improves the elastic modulus of cement-based materials. This enhanced stiffness results from the filling and pozzolanic effects of the nanoparticles, leading to increased elasticity [42,43].

3.2.3. Toughness Improvement

The inclusion of nanoclay or calcined nanoclay significantly improves the toughness of cement-based materials [11,38,44]. Particularly, calcined nanoclay is highly effective in enhancing toughness. It promotes better flexural strength, fracture toughness, and interfacial bonding in fiber-reinforced cement composites, but excessive content can reduce toughness due to agglomeration and poor dispersion of nanoclay particles [45].

3.2.4. Resistance to Chloride Penetration

Incorporating nanoclay into concrete reduces the chloride migration coefficient, especially at a 3% nanoclay content [46]. As nanoclay content increases, there are exponential reductions in the chloride diffusion coefficient, significantly enhancing resistance to chloride penetration. Nanoclay surpasses other nanomaterials in decreasing the chloride diffusion coefficient in mortar. This enhancement is due to the combined impact of filling, pozzolanic activity, nucleation, and the establishment of a stable framework by nanoclay, resulting in a reduction in chloride ion penetration [38].

3.2.5. Frost Resistance

Incorporating nanoclay significantly improves frost resistance in cement-based materials [47,48]. Concrete with nanoclay suffers less damage during freeze–thaw cycles than control samples. The improvement is particularly noticeable at 5% nanoclay concentration, which results in a higher compressive strength and a more favorable dynamic elasticity modulus. The enhancement is due to the advantageous impacts of nanoclay, such as pozzolanic reactions and filling properties, which reduce total porosity and subsequently increase the overall frost resistance of the material [46].

3.2.6. Acid and Sulfate Resistance

The application of calcined nanoclay significantly minimizes surface damage, mass loss, and the weakening of mortar strength upon exposure to acid deposits [38,49]. The microstructure becomes denser due to the filling effect and pozzolanic reaction of the calcined nanoclay, which helps mitigate the impact of acid exposure. Similarly, when faced with a sulfate or acid attack, calcined nanoclay aids in slowing down the rate of compressive strength loss, expansion strain, and mass loss in concrete. The decrease in concrete permeability as a result of the influence of calcined nanoclay contributes to its resistance against harmful ions [50].

3.2.7. High-Temperature Resistance

Calcined nanoclay significantly enhances the high-temperature resistance of cement-based materials [51,52,53]. The residual mechanical properties of mortar modified with nanoclay see a substantial increase, particularly at temperatures above 400 °C. This improvement is due to the additional C-S-H generated in the presence of nanoclay at high temperatures. Nanoclay’s ability to produce additional hydrates, bridge pores within the matrix, and reduce thermal stresses, coupled with a decrease in micro-cracks, bolsters the resilience of cement-based materials to high temperatures [47].

3.2.8. Structure and Crystallization

Polymers are classified into amorphous and semicrystalline types, and nanocomposites feature spherical semicrystalline regions within linear polymers, joined by cross-linked chains of constitutional repeating units (CRU). Various factors, such as CRU chemistry, linkages, macromolecular arrangement, and tacticity, influence nanocomposite structure, phase formation, and mobility. Thermal properties such as melting temperature (T_m) and glass transition temperature (T_g) of polymers, along with clay properties, significantly impact the intercalation/exfoliation in nanocomposites [54]. Clay dispersion varies based on nanoparticle incorporation and processing methods. Parameters like clay modification, processing conditions, compatibilizers, and viscosity influence delamination. High-speed mixing and extruder temperature disrupt clay’s layered structure, facilitating intercalation [55,56]. Supercritical carbon dioxide (sc-CO₂) can be used as a processing aid to produce exfoliated clay particles, although foaming may inhibit this exfoliation process. Intragallery polymerization, resin diffusion, and intercalation determine exfoliation, while expanded interlayer galleries suggest intercalated hybrids [57]. To achieve useful nanocomposite materials, selecting appropriate processes, materials, and conditions is crucial. Melt blending with roll mill or screw extrusion is preferred for achieving better dispersion and exfoliated/intercalated nanoclay structures due to improved interactions between the polymer matrix and layered silicates. The thermodynamic analysis, where the change in Gibbs free energy (ΔG) indicates exfoliation, is a key consideration. The crystalline phases in high molecular weight polymers like PVDF are influenced by processing conditions and nanoclay nature, and the crystallization pressure affects nucleation and growth processes, ultimately impacting nanocomposite properties [58].

4. Properties of Nanoclay Composite

Nanocomposite materials can be made with as little as 5% weight of nano-filler. Improvements occur in flame retardance, dimensional stability, gas and liquid impermeability, mechanical, thermal and electrical properties. None of these advantages come at the expense of composite density or matrix resins’ ability to transmit light [59].

4.1. Nanoclay Chemical Structure and Modification Methods

Nanoclays are a subset of clay minerals, distinguished by having at least one dimension at the nanoscale. They belong to the broader category of clay minerals, primarily falling under the classification of phyllosilicates. Phyllosilicates are layered aluminosilicates, comprising sheets composed of aluminum and silicon oxides that are arranged in stacked layers [1,60]. Phyllosilicates are classified based on their structural features: (i) sheet types (i.e., trioctahedral or dioctahedral) and (ii) layer stacking (1:1 or 2:1). The 1:1 (or TO; Figure 1A) layer stacking is assembled with one tetrahedral sheet and one octahedral sheet. The 2:1 (or TOT; Figure 1B) layer stacking is built with two tetrahedral sheets sandwiching an octahedral sheet. In summary, two distinct types of phyllosilicates are recognized: 1:1 and 2:1 (Figure 1) [1].

Type 1:1 phyllosilicates are distinguished by their structure, which includes a tetrahedral and an octahedral layer. Minerals such as halloysite and kaolinite exemplify this composition. However, these nanoclays are less utilized for incorporating active compounds due to certain limitations. Kaolinite lacks the ability to expand the separation between its layers (non-expandable), while halloysite possesses a tubular shape. Despite this, halloysite is intriguing because its internal and external surfaces carry opposite electrical charges when in contact with water (at a pH between 3 and 8). This phenomenon has been exploited for the transportation of various substances [62,63].

Type 2:1 phyllosilicates are characterized by sheets that consist of two alternating tetrahedral layers and one octahedral layer. Among these, the most prominent are used as carriers for active compounds. This category includes nanoclays such as vermiculite, pyrophyllite, mica, smectite and chlorite (Figure 2). In this scenario, two octahedral layers are situated adjacent to each other, sandwiched between a pair of tetrahedral layers [1].

Clay minerals are widely used because of their exceptional versatility and broad range of applications. Among them, montmorillonite (MMT) is particularly notable for its abundant availability and high aspect ratio (the ratio of length to thickness of its sheets) [1,64]. Layered clay minerals among the different types of inorganic nanoparticles have garnered increased interest due to their commercial accessibility, cost effectiveness, relatively straightforward processing methods, and notable improvements in properties [65]. MMT, a prevalent type of nanoclay, falls under the category of magnesium aluminum silicate and exhibits a sheet-like morphology. These sheets, also referred to as platelets, possess a permanent negative charge and are bound together by cations such as Na⁺ and [66]. The MMT exhibits an extensive total surface area, reaching up to 750 m² g⁻¹, combined with a notable aspect ratio ranging from 70 to 150 [67]. Carboxymethyl cellulose hydrogels produced by using MMT depicted better results in the field compared to the vermiculite as MMT did not alter the structure of hydrogel due to its low compatibility with carboxymethyl cellulose that enhances the water absorption capacity and make it suitable for agricultural application [68].

Nanoclay, known for its cost effectiveness and ready availability, can enhance the flexural modulus and reduce the coefficient of linear thermal expansion in the polymer matrix when added in a small proportion (1–5 wt%) [62,63]. Due to its high aspect ratio, nanoclay forms a complex pathway that impedes the flow of gases and vapors, thereby enhancing barrier properties against gasoline, nitrogen, oxygen, water vapor, and carbon dioxide. The benefits of polymer–clay nanocomposites have been thoroughly outlined by Alamri and Low [69]. They emphasized their superior physical properties such as shrinkage, optics, dielectric properties, and permeability. They also underscored their mechanical characteristics including toughness, strength, and modulus. Additionally, they noted their thermal attributes like decomposition, thermal expansion coefficient, thermal stability, and flammability [69]. Figure 3 focuses on utilizing the nanoclay-based pickering emulsions to develop stable, functional, and eco-friendly formulations for applications in the agri-food sector, cosmetics, pharmaceuticals, and various other industries [70].

4.2. Synthesis of Liquid Nanoclay

Desert Control, a Norwegian startup, has introduced an innovative solution, liquid nanoclay (LNC), to counter desertification by converting barren sandy deserts into productive farmland. This technology combines clay with irrigation water to create liquid nanoclay (LNC) on-site. The application is then performed on sandy soil using traditional irrigation systems like sprinklers or water wagons. The individual clay flakes bind to sand particles through Van der Waals forces, allowing the mixture to penetrate the soil up to root depth, typically 30–60 cm. Liquid nanoclay is the result of a patented process that involves mixing irrigation water with clay (Figure 4). This mixing is conducted directly on the site, and the resulting LNC is utilized on sandy soil. The soil is irrigated until the mixture has fully saturated the soil down to the depth of the roots, typically accomplished within a short span of 7 h. Impressively, the LNC application process takes only 7 h, a remarkable improvement compared to the natural regeneration timeline, which generally spans 7 to 15 years for the transformation of dry to arable land as the latter is slow and time taking compared to the earlier one [71].

The recommended clay flakes for this production have a diameter of the surface ranges from 25 to 2000 nm, with a thickness between 1 and 10 nm. This method relies on the negative charge on nanoclay particles’ surfaces, which attracts positively charged water molecules, ensuring dispersion stability. Incorporating air into the dispersion as tiny bubbles enhances stability, creating weak interactions with the negatively charged clay particles, effectively enveloping the nanoclay particles in a cloud of air ions. Experimental findings recommended a 1.5% suspended clay concentration, which translates to approximately 40 L of water and 1 kg of clay per square meter of land. To create a stable dispersion, a process involving consecutive laminar and turbulent flows at changing angles (45–135 degrees) was employed [71].

4.3. Synthesis of Nanoclay

4.3.1. Solution-Blending Method

This process involves solvents in which both the polymer and prepolymer are soluble, resulting in the swelling of clay layers [72]. The clay layers disperse and exfoliate into single layers when mixed with a suitable solvent, such as chloroform, toluene, or water. The process typically includes clay dispersion, solvent removal, and casting composite films. Ultrasonication, which breaks up nanoclay clusters, has become efficient in improving dispersion.

4.3.2. Melt-Blending Method

In this method, intercalated nanoclay particles are combined with polymers above their softening point, in an inert gas environment [73,74,75,76]. Batch and continuous melt mixers are used, each with its advantages and drawbacks. Recent advancements include using supercritical carbon dioxide (scCO₂) to enhance nanoclay dispersion following melt blending [77].

4.3.3. In Situ Polymerization Method

This approach effectively forms composites, circumventing the thermodynamic requirements related to polymer intercalation. In situ polymerization facilitates a versatile molecular design of the polymer matrix, expanding the property range and enabling tailored interface design between nanoclays and polymers. Various in situ polymerization techniques exist, including photopolymerization, controlled/living radical polymerization, emulsion polymerization, and click coupling chemistry, are used for tailored surface modifications and grafting [78].

The procedure involved the preparation of various nanocomposite polymers (NCPCs) using a series of samples with different types of clays. This synthesis was based on a method described by Liang and Liu. Initially, acrylic acid (AA) and acrylamide (Am) were dissolved in distilled water, and ammonia was added to partially neutralize the mixture. The clay was then dispersed in this solution. Under a nitrogen atmosphere, a crosslinker (N, N’-methylene bisacrylamide) was introduced, and the solution was stirred at room temperature for 30 min. The temperature gradually rose to 70 °C with continuous stirring, and ammonium persulfate was added as the radical initiator. After the polymerization reaction was completed, the resulting product was washed, dried, and milled to a particle size of less than 1 mm in diameter [79].

Nanoclays have garnered significant interest for their reinforcing properties in polymer nanocomposites, use as rheological modifiers in paints and inks, and their ability to act as sorbents for pollutants in wastewater. The effectiveness of nanoclays in these applications depends on the organic modifiers used during synthesis. The interlayer space of MMT with quaternary alkyl ammonium salts exchanged cations and produced the commercial nanoclays. However, the use of organoclays in high-temperature engineering plastics is limited because of thermal stability issues, whereas the thermal stability issue can be resolved by using quaternary phosphonium salts [48]

4.3.4. Use of Ammonium Salts in Nanoclay Synthesis

The quaternary ammonium salts are added to the MMT slurry at a higher temperature along with different organic modifiers to prepare organoclays followed by continuous stirring. A similar process is followed to synthesize the nanoclays using different phosphonium salts to develop variations in the nanoclays. The properties of nanoclays can be modified using different organic modifiers that expand their usage in various fields [80].

5. Nanoclay Application as a Soil Modifier

5.1. Nanoclay as a Soil Properties Modifier

5.1.1. Improved Water Retention and Drainage

The modified clay-based nanoclay polymer composite (NCPC) depicted increased water retention, greater water absorbency, and gradual water release compared to the pure clay-based NCPC. The water stress issues in rainfed agriculture applications has been addressed using P-coated nanoclay polymers that serve as a suitable superabsorbent [81]. The developed superabsorbent polymers aim to enhance soil water retention, facilitating seed germination and fostering plant growth [82].

Due to its ability to diminish irrigation water requirements, enhance fertilizer effectiveness in soil, decrease plant mortality, and promote plant growth, superabsorbent polymers have recently gained significant traction. These polymers are being increasingly recognized as a valuable water management solution for revitalizing arid and desert environments [83,84]. The substantial contribution of superabsorbent polymeric materials, when combined with clay minerals, lies in their capacity to enhance water retention capabilities [85]. Clay minerals can manifest characteristics like the formation of thixotropic gels with water, significant water absorption, and a notable cation-exchange capacity, which are key features [60]. It has been reported that the introduction of modified montmorillonite nanoclay into clay soils resulted in heightened liquid limit and plasticity index values, along with a significant enhancement in the context of soil’s unconfined compressive strength [86]. The treatment with nanoparticles also impacts the shrinkage characteristics of clays, offering the potential for nanoparticles to serve as soil amendments that reduce soil contraction during the desiccation process [87].

The application of nanomaterials in soil treatment has proven to be cost effective by requiring only a small quantity of agents. These materials also serve as long-term water barriers and maintain soil strength. The study evaluates how nanomaterial-treated soils’ permeability and compressibility impact their strength. Soil particle sizes ranging from 90 mm to 100 nm exhibit weaknesses in terms of strength, settlement, and stability due to the development of pores, leading to notable swelling and shrinkage characteristics [88]. The soil samples within the compact small core samplers were dampened through capillary action. Water retention at 300 kPa was determined by employing a pressure plate apparatus [89].

5.1.2. Soil Stabilization

Soil stabilization refers to the enhancement of the engineering characteristics of soil layers. This process involves combining different mineral materials, soil types, or suitable chemical additives with the pulverized soil, which is subsequently compacted. The goal of soil stabilization is to increase soil density, improve cohesion, strengthen friction resistance, and reduce the plasticity index [90]. The extensive surface area of nanoparticles promotes numerous interactions among blended materials, as seen in nanocomposites. These interactions contribute to unique properties, including heightened material strength [91]. A study was undertaken to showcase the effectiveness of incorporating nanoclay in enhancing the various geotechnical characteristics of stabilized soft soil. The outcomes demonstrated that the inclusion of nanoclay particles yielded improvements, particularly in terms of soil strength and effective shear strength.

The addition of nanoclay amplified the available surface area for interaction with the clay soil, ultimately leading to enhanced engineering properties. This improvement was ascribed to the consistent reaction with nanoclay, resulting in a smoother surface formation. Figure 4 illustrates the relationship between axial strain and deviator stress for both pure soft soils and soft soils mixed with 3% nanoclay, revealing that the introduction of 3% nanoclay elevated the maximum shear strength while concurrently reducing axial strain compared to the sole soft soil (control) sample [92]. The combination of soft soil and 3% nanoclay showcased the most favorable outcome concerning effective strength. This was attributed to the strong internal bonding between soil particles, contributing to a substantial increase in effective shear strength. Incorporating 3% nanoclay into the stabilization of soft soil yielded a significant enhancement, resulting in an approximate 15% increase in compressive strength compared to the unstabilized soft soil [92].

5.1.3. Reduced Erosion

Wind erosion is acknowledged as a significant soil degradation phenomenon in arid and semiarid zones. It has the potential to impede agricultural productivity, deplete nutrients and diminish soil fertility, lead to plant loss, contribute to landslide occurrences, and exacerbate air pollution, thereby negatively impacting the environment and human well-being, particularly health [34,93,94,95]. Notably, the control treatment exhibited substantially greater soil erosion compared to the nanoclay treatment. Employing nanoclay on the soil surface proved effective in fortifying the soil’s ability to mitigate wind erosion, consequently leading to a reduction in the quantity of easily erodible material [96,97]. The clay content within soil significantly influences soil aggregation, resulting in higher clay content contributing to more stable aggregates. This, in turn, can enhance the soil’s resistance against wind erosion. Research demonstrated that the effective control of wind erosion could be achieved by applying 2 gm⁻² polyacrylamides to the surfaces of loam and sandy loam soils. Soils with low water content and minimal organic matter are highly prone to wind erosion, particularly during windy, dry fallow periods [98]. Nanoclay acts as a binding agent that brings together surface particles, resulting in the formation of a cohesive crust. This thin layer, generated by nanoclay, effectively enhances the soil’s ability to withstand wind forces. The nanoclay-treated surface layer of sandy soil exhibits uniformity, notable firmness, and remains crack-free upon drying, while remaining permeable to water [99]. Enhanced soil aggregate stability corresponds to a reduction in soil degradation, thereby establishing a reciprocal relationship between aggregate stability and soil degradation [96]. Nanoclay’s presence increased the soil’s volumetric water content at 300 kPa, notably enhancing water retention compared to the control. This incorporation elevated moisture storage in sandy soil. Moreover, nanoclay’s usage could potentially impact pore size distribution equilibrium and soil surface area. Its hydrophilic nature causes changes in soil properties, including increased moisture levels and the formation of micro-porosity [97].

Introducing nanoclay into soil holds significant promise for fortifying its resistance to wind erosion. Particularly, nanoclay at 2000 ppm exhibited superior wind erosion control compared to water alone. Nanoclay demonstrates a favorable capacity for shaping and maintaining aggregate structure, contributing to notable aggregate stability when introduced to soils [97]. This property plays a key role in wind erosion control via nanoclay application. The results also indicated heightened water retention in sandy soil when treated with nanoclay, compared to untreated soil. In arid landscapes, the water-holding capacities of nanoclay and its controlled release play an essential role.

5.1.4. Enhanced Seed Germination

The use of nanotechnology in seed treatment is an emerging area of research. Nanoagrochemicals used for seed treatment are gaining prominence due to their heightened effectiveness in comparison to traditional agrochemicals, rendering them both economically feasible and ecologically sound. Empirical evidence has indicated that nanoparticles have the capacity to elevate both seed germination rates and biomass yields. Additionally, nanoparticles have demonstrated an ability to enhance seed resilience against various biotic and abiotic stressors. The biological functions of seeds depend on molecular processes [100]. In the past ten years, nanomaterials have demonstrated significant and beneficial chemical interactions in agricultural seed systems. These interactions encompass a wide spectrum of applications, including seed disease control, yield enhancement, and environmental preservation [93,101,102,103,104].

Recent research has indicated that the application of nanomaterials to seeds can trigger the activation of numerous genes during the germination process. Evidence suggests that nanomaterials facilitate seed germination through mechanisms; for example, processes include creating nanopores in seed coats, generating reactive oxygen species (ROS), enhancing enzyme activity at locations involved in starch degradation, and introducing ROS to the seed coat [105,106,107]. Research indicates that nanoparticles could induce the production of •OH radicals, generating ROS. When seeds are soaked in nanomaterial solutions, bound nanoparticles release •OH radicals, which loosen cell walls, ultimately promoting seedling growth [108]. The utilization of nanomaterials on seeds offers the potential to safeguard them during storage, elevate germination rates, synchronize germination processes, enhance early-stage growth, and substantially diminish the necessity for pesticides and fertilizers [109].

5.1.5. Nanoclays as Fertilizers for Sandy Soils

Nanoclays are extensively employed as nanocarriers for fertilizers, boasting a diverse array of materials available in both anionic and cationic variations. Anionic clays or hydrotalcite-like compound, alternatively known as layered double hydroxides (LDH), possess a distinctive capacity for exchanging anions. This property makes them exceptionally well-suited for facilitating the transport of phosphate, borate, and nitrate ions [110,111]. The addition of liquid nanoclay to sand soil offers a range of benefits that contribute to improved soil quality, increased plant productivity, and environmental sustainability (Figure 5). The illustration describes how the improved soil structure with liquid nanoclay (LNC) can lead to improved soil stability, nutrient and water retention, reduced erosion, increased soil fertility, improved seed germination, and increased environmental sustainability. It binds to nutrients, limiting their loss, and increases water retention, lowering the need for regular watering. In coastal locations and high-rainfall zones, LNC also lessens soil erosion, improving soil cohesiveness. It also increases the rates at which seeds germinate by giving the soil a sturdy structure and retaining moisture around the seeds. LNC is widely accessible and simple to use due to its affordability. Additionally, it prolongs the times during which plants develop, increasing their resistance to climate change in their surroundings [71].

5.1.6. Using Nanotechnology for the Efficient Delivery of Fertilizers, Chemicals, Herbicides, Pesticides, and Plant Growth Regulators

Nanoformulations encompassing nanocapsules, nanocarriers, nanocomposites, nanofibers, nanoemulsions, and nanogels are employed to convey diverse substances within different segments of plant systems. These nanomaterials exhibit distinct attributes like precise nanoscale dimensions, advantageous surface-to-volume ratios, biodegradability, and biocompatibility. These properties enable the materials to adeptly store and release compounds in a controlled manner, thereby fostering plant growth, augmenting crop yield, enhancing plant protection, and mitigating environmental pollutants. The nano-scale delivery systems utilized in these formulations offer enhanced biocompatibility, biodegradability, and stability, rendering them eco-friendly technological solutions [112].

Under various conditions including soil type and growth stages, treatments involving Zinc Nanoclay Polymer Complex (ZNCPC) consistently exhibited higher soil zinc content (measured through DTPA extraction). Nanoclay-incorporating ZNCPC formulations displayed a reduced release of DTPA-extractable zinc compared to clay-containing ZNCPC [113]. This can be attributed to the greater aspect ratio of nanoclay compared to regular clay, leading to enhanced diffusion barrier properties. This, in turn, resulted in a controlled and gradual release of zinc into the soil. The absence of the typical bentonite peak indicated that the nanocomposites were exfoliated in nature. Nano-sized clay particles (sized below 100 nm) within ZNCPC interacted with monomer functional groups, effectively acting as diffusion barriers [113,114]. The ZNCPC served as a controlled-release zinc formulation, with zinc release mediated by mechanisms involving microbial enzyme hydrolysis and diffusion control. Prior research has also reported the degradation of Nanoclay Polymers Complexes (NCPCs) within the soil. The carrier of zinc within ZNCPC, citrate, was simultaneously released into the soil solution along with zinc. Elevated citrate levels in the rhizosphere soil facilitated the mobilization of native or applied zinc. Citrate, a commonly found low molecular weight organic acid in the rhizosphere, plays a vital role in solubilizing zinc and facilitating its internal transfer [115,116]

5.1.7. Impact of Different Zinc Carriers on Zinc Fractions

The application of Zinc Nanoclay Polymer Complex (ZNCPC) led to an increase in various fractions of zinc availability in the soil. This included exchangeable, water-soluble, organically bound, and amorphous iron oxide-bound forms of zinc. As ZNCPC degraded in the soil, citric acid was released, effectively solubilizing the initially fixed form of zinc [117] As a controlled-release formulation, ZNCPC slowly releases zinc, thus sustaining higher levels of water-soluble and exchangeable zinc content. The phytoavailable zinc pool includes not only the water-soluble and exchangeable forms, but also the initially bound zinc and zinc attached to amorphous iron oxides [118]. The treatments involving ZNCPC showed a higher content of available zinc (sum of water-soluble and exchangeable forms), representing an 8% increase, while the maximum residual zinc was observed in treatments with ZnSO₄•7H₂O, reaching 54%. The decrease in soil pH due to ZNCPC applications also contributed to an increased amount of phytoavailable zinc [118]. Irrespective of the zinc carriers, the largest quantity of zinc was present in residual fractions. Spectroscopic identification of residual fraction using XAS showed the incorporation of zinc into the hydroxy–Al interlayers of phyllosilicates in subsurface samples and franklinite, a cubic zinc–iron oxide in surface samples of highly acidic soil contaminated by nearby sphalerite-smelter operations [119]. Incorporating ZNCPC resulted in higher levels of DTPA-extractable zinc, DTPA-extractable iron, and Olsen-phosphorus, as well as biological parameters like dehydrogenase activity (DHA), alkaline phosphatase (ALP), and microbial biomass carbon (MBC) activity. These enhancements significantly contributed to increased yield-related characteristics [117]. The application of fertilizer resulted in a 13% increase in green gram yields and a 38% increase in black gram yields compared to the control group. Data demonstrate that fertilizer formulations based on nanoclay, capable of releasing nitrogen over approximately 1000 h, exhibit comparable effects to conventional fertilizers that release nitrogen over only 500 h. The utilization of nanotechnology holds potential for enhancing food production. The incorporation of nanoporous zeolites in agricultural inputs has gained prominence over time due to the growing societal concern about the adverse impacts of chemical fertilizers on the agro-ecosystem.

5.1.8. Improving Nutrient Use Efficiency with Nano-Fertilizers

Nano-fertilizers possess distinct attributes that contribute to their enhanced effectiveness in nutrient uptake:

• The diminutive size of nano-fertilizers creates sites for plant nutrient metabolism, while their extensive surface area amplifies their impact. This synergy leads to heightened plant growth while requiring less essential nutrient consumption.
• With particle sizes below 100 nm, nano-fertilizers exhibit an accelerated penetration rate within the plant system.
• Nano-fertilizer particles, due to their smaller size and greater surface area compared to plant leaves and roots, facilitate superior penetration into plants from applied surfaces. This leads to increased utilization and bioavailability of the nano-fertilizers.
• Reduced particle size leads to increased surface area and a higher particle count per volume. This advantage is harnessed by those applying the chemicals, enhancing efficacy.
• Integrating micro-particles with fertilizers enhances the absorption and delivery of nutrients to crops [120].

5.1.9. Nutrients and Fertilizers

Various nanomaterials can serve as fertilizers, encompassing those composed of the specific nutrient (e.g., hydroxyapatite nanoparticles for supplying phosphorus) and those carrying the nutrient of interest through loading [121]. Zeolites, nanocomposites, and clay minerals are commonly employed in the production of the latter category, yielding slow-release fertilizers [122]. The details of various nanoclays utilized for the gradual release of fertilizers and plant nutrients are given in

Table 1. Utilization of nanoclays for the gradual release of various plant nutrients and fertilizers.

Clay	Nutrient/Fertilizer	Refs.
Layered double hydroxides	Zinc	[123]
Layered double hydroxides	Boron (Na2B4O7•10H2O) and Zinc (Zn(NO3)2•6H2O)	[111]
Montmorillonite	CuSO4	[124]
Montmorillonite	NH4-N	[28]
Montmorillonite	Nitrate	[125]
Montmorillonite-hydroxyapatite nanohybrid	Urea	[126]
Phlogopite	K	[127]

.

Extensive research on nanoclay has been carried out for the development of polymer nanocomposites. These are intended for a variety of applications such as paints, cosmetics, water purification, drug delivery, and controlled release of fertilizers [128]. The text presents examples of various nanoclay polymer composites used in slow-release fertilizers. These nanocomposites are generally formulated with acrylamide, acrylic acid, and natural biopolymers such as sodium alginate and chitosan. The inclusion of clay in the polymer matrix enhances the cross-linking density. As this cross-linking becomes more intense, the space available for water ingress decreases; hence, the addition of clay reduces the mesh size within the densely cross-linked polymer network. This results in a restriction to nutrient diffusion, facilitating a gradual release of nutrients [122].

5.1.10. Nanoclay as a Carriers and Delivery System for Agrochemicals and Bioactive Molecules

Nanotechnology is demonstrating remarkable promise in addressing food security challenges by increasing food availability and delivering enhanced products that offer substantial benefits across agriculture, water management, environmental preservation, drug innovation, and healthcare [129]. Enhancements in nanotechnology research have the potential to enhance fundamental elements of food security, including agricultural efficiency, soil enhancement, responsible water utilization, efficient food distribution, and food quality [130,131]. Over the past few years, the field of agricultural nanotechnology has been dedicated to researching and implementing solutions for sustainable agriculture and environmental challenges, as well as enhancing crop quality and overall productivity. The domain of agricultural nanotechnology holds significant promise, particularly for developing nations, as it has the potential to address issues related to hunger, malnutrition, and child mortality rates [132]. The potential application of nanoscale agrochemicals, including nanoformulations, nanosensors, nanopesticides, and nanofertilizers has revolutionized conventional agricultural methods, rendering them more sustainable and effective.

Globally, an estimated 20–40% of annual crop losses are attributed to plant pests and pathogens. Contemporary agricultural methods primarily combat these issues through the extensive utilization of pesticides, encompassing insecticides, fungicides, and herbicides [101]. Nanotechnology-based traditional herbicides and pesticides contribute to a controlled, gradual release of nutrients and agricultural compounds to plants [133,134]. Polysaccharides like alginates, chitosan, polyesters, and starch have been explored to produce nano-insecticides [133,134]. Agrochemicals hold a crucial function in agricultural production. Nevertheless, their conventional application can lead to their breakdown or elimination through climatic elements such as rainfall, sunlight, and wind [97].

A notable portion of agrochemicals fail to reach their intended target species, necessitating repeated applications. Employing agrochemicals multiple times not only escalates expenses but also gives rise to unfavorable repercussions on plants, the environment, and the health of individuals who encounter them through the food chain [135].

6. Nanoclay for Improving Plant Performance

6.1. Nanoclays and Their Expanding Horizons

The potential applications of nanomaterials have captivated researchers. Among these, natural nanomaterials like nanoclays found in soils can be combined with polymers to enhance the properties of the latter. Particularly, polymer–nanoclay composites have gained significant attention in recent times due to their remarkable engineering attributes, including high damping, low density, strong specific stiffness and strength, improved thermal behavior, and elevated fatigue endurance. This has resulted in a swift rise in the utilization of innovative polymer–nanoclay composites across various sectors. This section offers an in-depth examination of nanoclay composites and their diverse applications. The use of nanoclay-based materials is a rapidly expanding research field. Modified nanocomposite materials are anticipated to be ideal for a wide range of applications [78,136,137].

Nanomaterials derived from nanoclays find diverse utility in sectors spanning optoelectronic devices, gas adsorption, agriculture, and industries like battery and automotive manufacturing. In the realm of agriculture, nanoclays are swiftly gaining traction as effective agents for transferring and transporting agrochemicals within agricultural domains. Notably, nanoclays laden with herbicides have demonstrated a notable impact on promoting sustainable agricultural practices [138]. A nanoclay of MgAl-layered double hydroxide loaded with the herbicide 2, 4-dichlorophenoxyacetic acid (2, 4-D) was developed. This nanoclay–herbicide composite was applied to Arabidopsis thaliana plants at doses relevant to agriculture. To evaluate potential cell damage or stress in the plants, a specific stress marker known as callose (a β-1, 3 glucan) was used [138]. Treated plants did not exhibit any induced physiological stress. In vitro investigations demonstrated a gradual release of 2, 4-D from the preloaded nanoclay over a span of 18 h. This controlled release exhibited a prolonged and irreversible herbicidal impact on the tested plants. Hence, these nanoclay materials offer distinct advantages compared to conventional agrochemical spray applications reliant on surfactants [138]. This advantage arises as the nanoclays adhere to the leaf surfaces and enhance the electrical characteristics, rendering them an optimal choice. The decomposed elements of the clay, like Mg and Al, enhance plant nutrient levels. Meanwhile, the robust electrostatic interaction between nanoclay and 2, 4-D contributes to reducing contamination of soil and groundwater. Biodegradable films exhibit appealing attributes in contrast to petroleum-based polymers such as polyvinyl chloride and polyethylene [61].

The utilization of nanoclays can be extended to various fields by tailoring their physical and chemical attributes. These attributes include particle size distribution, zeta potential, surface area, and hydrophilicity/hydrophobicity, type of exchangeable cations, porosity, and interlayer space. This customization can be achieved through functionalization using a range of additives, including polymers, organic and inorganic compounds, or even nanoparticles [139]. Composite substrates based on nanoclay exhibit remarkable compatibility with various tissues and organs, offering a convenient means to control drug release in a sustained manner by manipulating morphologies like intercalated and exfoliated structures. Additionally, these substrates promote rapid bone regeneration and revascularization, owing to the abundant minerals present within the clay [139].

6.2. Toxicity and Environmental Impacts

In the realm of nanotechnology, discussions surrounding the toxicity and environmental consequences of nanoscale-based formulations persist. These concerns can be addressed through comprehensive scientific experiments, backed by their pivotal findings [139]. However, certain points of contention necessitate further clarification, particularly in regard to the potential environmental or bioaccumulative effects of nanoclay-based fertilizers, herbicides, and pesticides within soil, surface water, and groundwater. Additionally, the impact on non-target organisms warrants examination. Similarly, it has been noted that the effectiveness of nano-bound active ingredients is heavily influenced by environmental factors like pH, ionic strength, and the presence of dissolved molecules [140]. To address this issue, the specialized nutrient composite based on nanoclay can be subjected to organic, inorganic, or polymer modifications. Another approach involves allowing these nanoclays to release the nutrients gradually and precisely from their carriers [61]. Clay minerals inherently possess an array of positive charges, which hold benefits for enhancing crops and soil. The potential toxicity of nanoclays appears to be shaped by factors like particle size, clay composition, intercalating compounds used limited solubility at low pH levels, surface reactivity, hydrophobic properties, and the duration of particle exposure, among various other factors [141]. A schematic overview of nanoclay vehiculization shows considerable potential for improving soil quality, nutrient management, insect control, seed performance, water efficiency, and soil remediation in sustainable agriculture. It has the potential to help build eco-friendly and economically viable agriculture techniques. The advantages of vehicle-based delivery of active ingredients are described in Figure 6 [142].

Encapsulating phytoactive substances within nanoclays can yield several advantages. These inorganic materials provide a shield against rapid deterioration caused by environmental factors, and intermolecular forces ensure a controlled and prolonged release, enabling extended treatment periods while using the same quantities of active ingredients [143].

7. Global Climate Change Mitigation

Carbon Dioxide (CO₂) Capture and Storage

The disclosed approach for carbon dioxide gas capture involves directing a gas containing carbon dioxide from an effluent process stream through the solid sorbent based on nanoclay. This results in the carbon dioxide gas being captured both on the surface and within the nanoclay-based solid sorbent. The solid sorbent based on nanoclay, which has captured carbon dioxide gas, goes through a regeneration process involving one or more cycles of desorbing the captured carbon dioxide from the nanoclay. Following this, the rejuvenated solid sorbent derived from nanoclay can be utilized once again [144]. This research delved into how the CO₂ adsorption capacity of the nanoclay adsorbent is influenced by its surface activation and modification. The favorable fit of the CO₂ adsorption experimental data to the Elovich model suggests that the modified sample establishes chemical bonds with CO₂, likely due to its elevated surface energy. Thermodynamic analysis revealed that the adsorption process occurs spontaneously and releases energy (exothermic) [145]. A cost-effective and readily accessible bulk material, montmorillonite nanoclay, served as the foundation for creating a solid sorbent designed for carbon dioxide capture.

The nanoclay has a high specific surface area and is characterized by a platelet-like structure with hydroxyl groups on its edges, was treated with aminopropyltrimethoxysilane and polyethylenimine to introduce active sites for CO₂ capture. CO₂ sorption experiments showed fast kinetics and impressive capture capacities, achieving up to 7.5 wt % at standard atmospheric pressure and roughly 17 wt % at 2.07 MPa pressure within the temperature range of 75–85 °C. The regeneration of these nanoclays was possible using nitrogen at 100 °C or dry/humid CO₂ at 155 °C as sweep gases. Moreover, a pressure swing process involving a vacuum at 85 °C also effectively regenerated the sorbent. This study underscores the potential of amine-modified montmorillonite nanoclay as a highly efficient solid sorbent for CO₂ capture [146]. CO₂, a crucial element within greenhouse gases, has exerted a notable impact on the rising temperatures. Consequently, the reduction in CO₂ emissions has garnered paramount importance [147,148]. Liquid nanoclay can save up to 50% of irrigation water while increasing yields while putting less burden on scarce resources. Using LNC to restore and improve soil allows land areas to better endure the harsh effects of climate change and over-exploitation.

8. Limitation of Nanoclay in Desert Agriculture

8.1. Limited Availability

Cultivating under suboptimal conditions demands extra funding to enhance soil quality. The existing infrastructure, including high-quality seeds, irrigation systems, and transportation routes, is frequently insufficient. Sustaining farming in unfavorable land conditions requires ongoing research into feasible and economical technologies. This research should concentrate on understanding the consequences of agro-ecological management across various cultural and environmental contexts, leading to the advancement of reliable and sustainable production methods [149]. This should be linked to the constrained accessibility of energy for absorption [150] to be generated using the restricted resources at hand [18].

8.2. Environmental Concerns

Assessing risks specific to nanotechnology presents a complex challenge, as the conventional assumptions applied in risk evaluations of regular chemicals may not align with the unique characteristics of nano-enabled products. Furthermore, the methodologies for testing and modeling their behavior in the environment and potential human exposure might not be suitable in this context [151]. When identifying hazards related to nano-formulations, it is crucial to center on both the properties of the active ingredient concentration and the nano-components. A comprehensive examination of the existing literature concerning the potential environmental and health risks associated with nanoparticles highlights the difficulty in interpreting findings for the specific goal of hazard identification [152].

When the role of the nano-component is primarily to safeguard the active ingredient from degradation, the destiny and conduct of this nano-component might mirror that of conventional pesticide formulations. The deliberate and augmented incorporation of nanomaterials into agricultural ecosystems raises several inquiries concerning the environmental destiny and dissemination of these substances within the environment, questions that remain to be addressed [153]. Such uncertainties encompass factors like the yet-to-be-understood impact of naturally existing ultrafine particles on the destiny of nanoagrochemicals, the ambiguities surrounding changes induced by aging, soil, and water attributes, and those brought about by the array of operational methods employed. Additionally, the challenges of incorporating all these variables into a comprehensive risk assessment process further compound the situation. Hence, the evaluation of risks presented by nanomaterials in agriculture might surpass the typical approaches employed to appraise the perilous characteristics of regular chemicals or even of the identical nanomaterials deployed in distinct contexts. The potential risks associated with unique contaminations involving “aged” nanomaterials resulting from waste treatment transformations remain inadequately studied. These contaminants could act as additional sources of nanoscale micronutrients or nanobiocidal substances, potentially interacting with intentionally introduced nanomaterials and changing the risks to both human and ecosystem well-being. Moreover, the extent to which nanomaterials originating from biosolids might enter food chains or cause direct/indirect harm to plants, microbes, or other soil organisms is not well understood. These effects might impact the agricultural ecosystem where nanomaterials are used, potentially affecting their behavior and efficacy in the environment [153].

Research into the adverse characteristics of nano-based agricultural chemicals should take into account the potential interplay between nanoscale chemicals and the various stressors presents within agro-ecosystems. These interactions could lead to a complex combination of antagonistic, synergistic, and additive effects, altering the toxicity levels caused by individual substances. This, in turn, might impact vulnerabilities to detrimental environmental and health outcomes [133,134,154,155,156]. In the context of comprehending the environmental and human health ramifications of deliberately formulated and utilized nano-solutions in agriculture, the complexity deepens due to the potential supplementary hazards stemming from “nano-emerging” contamination linked to biosolids.

8.3. Economic Feasibility

Insufficient investment in research infrastructure stands as a primary factor constraining the advancement of nanotechnology within agriculture and its associated applications [157]. Limited returns from the agricultural sector, elevated production costs, and inadequate technology transfer within the realm of agriculture contribute to these challenges [158].

8.4. Cost Analysis

The cost analysis of nanoclay was founded on utilizing natural, economically viable bentonite through a highly promising and efficient approach. As a result, an economic evaluation was conducted to determine the construction expenses, drawing from industrial-scale practices and extrapolating them to a practical scenario of large-scale production. The study provides accurate data on the estimated capital expenditure, yearly operational costs, and an inclusive summary of the expenses associated with purifying nanoclay from exposed bentonite. Specifically, the projected capital cost for nanoclay from bentonite is USD 2950 (Figure 7a) while the annual operational cost stands at USD 2825.25 (Figure 7b) [159].

The conditions of bentonite mining in Iran and the obstacles linked to exporting this mineral to other nations, along with factors like the economic expenses tied to mineral processing, prompted us to initiate a modest endeavor aimed at enhancing and addressing this issue [159]. The elevated production cost of nanoclay is attributed to its intricate manufacturing process, which necessitates the use of expensive chemicals and machinery [160]. The restricted access to and from the production fields’ location contributes to an escalation in the price of the resultant commodity, owing to the elevated production expenses [149]. Investing in suboptimal land for agriculture demands greater financial resources compared to cultivating arable areas. Ensuring sustainability necessitates the adoption of cost-effective methods to enhance crop yield while preserving environmental quality [161].

8.5. Long-Term Effect of Liquid Nanoclay on Soil Health and Fertility

Fertilizers are pivotal for enhancing crop productivity. Nanofertilizers offer controlled nutrient release, leading to prolonged response sustainability in comparison to conventional counterparts. This extended nutrient retention considerably diminishes nutrient loss, thereby fostering environmental safety and sustaining plant productivity. The use of organic polymers, intercalated within nanoclay layers, functions as a binding agent that controls the slow release of plant nutrients. The physicochemical attributes of clay nanoparticles facilitate nutrient absorption by plants, holding the potential to elevate performance and productivity rates substantially [162].

The continuous buildup of such materials within the environment poses a potential hazard. This concern extends beyond potential harm to soil and plants, encompassing the possibility of these materials entering the human food chain. Given these factors, it becomes imperative to comprehensively evaluate the distinct risks associated with each type of nanomaterial for plants, the environment, and human well-being. This assessment should leverage existing test methods and employ a wide range of assessment approaches to ensure a comprehensive understanding [38]. The debate on the toxicity and environmental impact of nanoscale-based formulations continues to be a significant topic in the field of nanotechnology. These concerns can be mitigated through thorough scientific experimentation, coupled with the identification of key findings. However, certain points of contention persist, necessitating clarification regarding the potential environmental effects and bioaccumulation of nanoclay-based pesticides, herbicides, fertilizers, and within soil, groundwater, and surface water. Concurrently, the potential impact on non-target organisms warrants further elucidation. Moreover, it has been observed that the efficacy of nano-bound active ingredients is intricately tied to environmental factors such as ionic strength, pH, and the presence of dissolved molecules [18]. Liquid nanoclay (LNC) is a soil amendment used in agriculture, consisting of clay particles ground to nanoscale. When applied to soils, LNC enhances soil structure, boosts water retention, reduces nutrient leaching, boosts agricultural production, and contributes to sustainable farming practices (Figure 8). The treatment involves spraying LNC suspensions or mixing them into irrigation water for direct soil application. Due to the small particle size of LNC, it can penetrate deeper into the soil. The clay particles may bond with soil particles, enhancing soil aggregation. Further research is needed, however, to fully understand the long-term impacts, potential hazards, and appropriate application methods of LNC in various soil types and agricultural systems.

9. Future Directions and Recommendations

9.1. Discussion of the Potential for Further Research and Development of Liquid Nanoclay

Mineral clays used in agrochemical formulations serve therapeutic and nutritional purposes, enhancing crop yield and productivity. However, these clay minerals can also negatively affect the plants and soils where they are applied, with the impact influenced by various biological, chemical, and physical parameters. They can trigger a variety of cytological changes in plants and microorganisms. Generally, the toxicity of these minerals is linked to the presence of external intercalated compounds. Numerous attempts to analyze nanomaterials’ safety have been made, yet more studies are required, especially concerning the lifecycle framework and field usage. Future research should prioritize understanding the mechanistic aspects of nanoclay toxicity, its interactions with cellular components, and associated risks [61]. The era of nanotechnology is swiftly unfolding, with its applications in sustainable agriculture becoming increasingly prevalent. Nanotechnology has significantly advanced the agricultural sector, particularly in weed control, fertilization, disease management, and pest control. This progress is crucial given the worldwide and well-documented misuse of agricultural chemicals. Conversely, the excessive use of agrochemicals to enhance agricultural production has caused pollution in both the topsoil and groundwater systems, subsequently affecting our food supply [163]. The increasing interest in optimizing suboptimal land stems from the understanding that enhancing agricultural productivity has become agronomically challenging and economically less viable. This heightened interest has led to sustainable methods for food production in suboptimal lands [62]. Nanotechnology can enhance the efficiency of seeds, minimize environmental pollution, support agricultural sustainability, and boost food security through its application in nanoagrochemical delivery. By decreasing the amount of pesticides and fertilizers used on crops, nanoagrochemical seed treatments improve the precision and effectiveness of seed protection products. Nanocarriers with controlled delivery in agro-seed treatment provide numerous benefits for sustainable agriculture compared to traditional chemical delivery systems. These advantages include biosorption rate, biocompatibility, reduced synthesis costs, easy biodegradation, and thermo-plasticity. Mineral clays in agrochemical formulations are used for therapeutic and nutritional purposes, enhancing crop yield and productivity. However, depending on various biological, chemical, and physical parameters, these clay minerals can also have adverse effects on the plants and soils where they are applied [61]. Nanoclay composites play a vital role in wastewater and water treatment, efficiently eliminating pollutants such as pesticides, poly and perfluoroalkyl substances, nitrates, dyes, pharmaceuticals, microorganisms, fluorides, toxic metals, and other emerging contaminants. However, the majority of research conducted to date has been on a laboratory scale in batch mode or on a smaller production scale [162]. The advancement in nanoscale material synthesis, including nanofibers, nanosuspensions, nanocapsules, nanogels, and nanoclay, could be useful for next-generation seed treatment strategies. There is a need to establish national and international risk assessment and management strategies for implementation of nanomaterials. Conclusively, the use of nanoscale formulations for seed treatment is imperative for crop growth and it would play an imperative role in sustainable crop production [50]. Agricultural systems like mitigation of soil erosion, regulation of nutrients availability and soil quality enhancement can be carried out by liquid nanoclay (LNC). It serves as a protective barrier against erosion, reducing the necessity for regular fertilization. Additionally, LNC inhibits harmful bacteria, promoting environmentally friendly practices. It contributes to sustainable land management and conservation by restoring degraded soils and maintaining soil fertility. The use of LNC in agricultural systems provides various benefits, including enhanced water and nutrient conservation, erosion reduction, plant growth, and soil fertility improvement with economic feasibility. Complete exfoliation of nanoclays within a polypropylene (PP) matrix is a pivotal topic of discussion, as there has not been any reported instance of achieving full exfoliation of nanoclay in a PP matrix, with previous reports indicating only partial intercalation and exfoliation. The exfoliation of nanoclays can potentially be realized through surface modification of MMT using dual organic modifiers or by modifying the PP itself [80]. The future forecasts mentioned in the review encompass the utilization of this nanotechnology in diverse polymer systems and various methods of clay modification, which will likely require the adoption of innovative strategies [13].

The Freedonia Group estimates that by 2020, the demand for innovative composite materials will increase to roughly 3.2 million tons, costing around USD 15 billion annually. Future applications of novel polymer–nanoclay composites are projected to include environmental concerns (biodegradable materials), safety (food packaging), and healthcare (biomedical applications) [78]. Kristian P. Olesen, Founder and Chief Technical Officer of Desert Control, asserts that liquid nanoclay could revolutionize agriculture in arid regions. He further explains that this technology can transform poor-quality sandy soils into highly productive agricultural land within just seven hours. An innovative technology, Desert Control, has been introduced in Norway as a startup and it is being used to convert arid deserts into fertile agricultural land and this solution involves liquid nanoclay [164].

9.2. Recommendations for Liquid Nanoclay Implementation in Arid Regions

Arid regions, which encompass a significant area of the Earth’s surface, face distinct challenges such as poor soil quality, limited water availability, and reduced land productivity. Liquid nanoclay has surfaced as an innovative solution to these issues. This article offers a detailed guide for the successful application of liquid nanoclay in arid areas, detailing essential actions and factors to fully realize its transformative capabilities.

9.3. Advanced Formulations

Further research and development could lead to more advanced liquid nanoclay formulations. Scientists may explore modifications to the clay particles and the addition of components that improve water retention, nutrient capacity, and performance in arid soils. Such innovations could significantly enhance liquid nanoclay’s effectiveness for desert farming.

9.4. Precision Application Systems and Technological Advancements

Technological advancements should aim to develop precision application systems tailored for liquid nanoclay. These systems would utilize specialized equipment, sensors, and automation to distribute the nanoclay solution accurately and efficiently over large-scale farming areas. Such precision application systems would guarantee even coverage and enhance the efficacy of liquid nanoclay for water retention and soil enhancement in arid agricultural settings.

10. Conclusions

With the increasing world population and the need to meet the increasing demand for food, the use of available arable land for agricultural production is necessary. Deserts are around one-third of the total earth’s land area, the conversion of desert land to fertile land not only opens up the opportunity for economic development but also contributes to job creation. Desert land faces several challenges including poor soil quality and limited water availability which result in reduced production. Nanoclay is a processed clay that is being extensively used in agriculture to mitigate soil erosion, soil quality enhancement, and nutrient management with economic feasibility. A thorough analysis of soil qualities, water availability, and hydrological conditions is required before using liquid nanoclay for water management in arid environments. Small-scale pilot projects are proposed to assess the technology’s effectiveness under various settings. Collaboration and education with local governments, academic institutions, and communities are critical for understanding the technology’s benefits and limitations. Knowledge-sharing platforms among stakeholders can facilitate knowledge exchange and collaboration.