ChemEngineering, Volume 8, Issue 4 (August 2024) – 19 articles

Soil restoration by exploiting the principles and basics of electrokinetic (EK) has been extended to involve several categories, such as electrokinetic remediation in soil (SEKR), soil consolidation, the prevention of soil pollution, reclaiming salt-affected soil, the dewatering/dryness of wet soils, water reuse, seed germination, sedimentation, etc. As an extension of our recently published review articles on the soil electrokinetic (SEK) process intensification/optimization, the present review illustrates the effect of a reverse-polarity mode (RPM) on the efficiency of the SEK. Based on several searches of six database search engines, we did not find any relevant reviews focused on SEK improvements using the RPM. The influences of the RPM are described by various features, including (a) pollutant removal (organic, inorganic, and mixed pollutants) and (b) integration with other processes (phyto/bioremediation and Fenton oxidation), geosynthetics (consolidation, stabilization, and sedimentation), SEK operation conditions, and soil properties. Most of the RPM studies have focused on the remediation of organic pollutants. Several benefits can be gained from applying the RPM, such as (a) controlling the soil’s temperature, pH, and moisture values at desirable levels, (b) reducing a large number of chemical additives, (c) high remediation efficiency, (d) maintaining the indigenous fungal community’s appropriate diversity and abundance, (e) a stable and higher electric current, (f) enhancing microbial growth, etc. However, the hindrances to applying the RPM are (a) reducing the electroosmosis flow, (b) relatively high energy consumption, (c) reducing the diversity of soil microbes with a prolonged experiment period, (d) providing oxygen for a microbial community that may not be desirable for anaerobic bacteria, etc. Finally, the RPM is considered an important process for improving the performance of the SEK, according to experimental endeavors. Full article

This study investigates the microstructure and first hydrogenation properties of Fe₅₂Ti₄₀Zr₃V₅ and Fe₃₇Ti₄₄Zr₉V₁₀ alloys, which are individual phases present in the as-cast TiFe + 12 wt.% ZrV₂ alloy (parent alloy). The parent alloy exhibited fast first hydrogenation kinetics due to the interplay of these two phases. Our objective is to study the hydrogen storage behavior of these individual phases. The samples were synthesized by arc melting and characterized by X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy. The results show that when these alloys are melted separately, they do not exhibit the same phase composition as in the parent alloy, indicating a metastable state under our synthesis conditions, which significantly impacts their hydrogen storage behavior. Hydrogenation capacity was measured using a homemade Sieverts apparatus. Both alloys demonstrated excellent first hydrogenation kinetics, with an absorption capacity of 0.9 wt.% for the Fe₅₂Ti₄₀Zr₃V₅ alloy and 2.3 wt.% for Fe₃₇Ti₄₄Zr₉V₁₀ alloy. Our key finding is that the final crystal structure of multi-element alloys is highly dependent on the synthesis method. Full article

This study investigates nitrogen-doped carbon synthesis and electrochemical properties as electrode material for energy storage devices, an additional focus of the work is on the electrochemical exfoliation synthesis of nitrogen-doped carbon using various precursors and doping methods. The physical properties of the synthesized sample are characterized using X-ray photoelectron spectroscopy, scanning electron microscopy, and Raman spectroscopy. The electrochemical properties of the N-doped carbons are studied using cyclic voltammetry and galvanostatic charge-discharge cycling. Finally, the work explores the potential application of the N-doped carbons as electrode material for energy storage devices, such as supercapacitors. The results show that N-doped carbons exhibit electrochemical performance superior to that of graphene oxide, with higher electrical capacitance. The results demonstrate the potential of N-doped carbons as high-performance electrode materials for electrochemical energy storage applications. This paper aims to explain the advantages of N-doping in carbon materials more precisely in graphene and the use of these materials in creating electrodes for application in supercapacitors and batteries. Full article

The role of dopants (Sm, Tb and Pr) on the water–gas shift performance of CeO₂-based materials was studied. Modification of CeO₂ with Sm significantly improved the water–gas shift performance. The catalytic activities of doped CeO₂ were increased when compared with the catalytic activities of pure ceria (65% conversion at 600 °C for Ce5%SmO and 50% conversion at 600 °C for CeO₂). The key factors driving the water–gas shift performance were reduction behavior and oxygen vacancy concentration. In the redox mechanism of the WGS reaction, CeO₂ plays a crucial role in transferring oxygen to CO through changes in the oxidation state. Therefore, Sm is effective in catalyzing the water–gas shift activity because the addition of Sm into CeO₂ decreases the surface reduction temperature and alters the oxygen transportation ability through the redox mechanism. XRD results suggested that Mⁿ⁺ (M = Sm, Tb and Pr) incorporate into ceria lattice to form a solid solution resulting in unit cell enlargement. The defect structure inside the CeO₂ lattice generates a strain on the oxide lattice and facilitates the generation of oxygen vacancies. XANES analysis revealed that Sm reduced CeO₂ easily by transporting its electron into the d-orbitals of Ce, thus giving rise to more Ce³⁺ at the CeO₂ surface. The presence of Ce³⁺ is a result of oxygen vacancy. Therefore, the high content of Ce³⁺ provides more oxygen vacancies. The oxygen vacancy formation results in easy oxygen exchange. Thus, reactive oxygen species can be generated and easily reduced by CO reactant, which enhances the WGS activity. Full article

Arsenic, the 20th most common element in Earth’s crust and historically regarded as the King of Poisons, occurs naturally in two oxidation states, Arsenate (V) and Arsenite (III), and is prevalent worldwide through natural and anthropogenic means. The cations of the metalloid exhibit unique chemical behaviour in water and are found to be components of approximately 245 natural minerals, making its occurrence in drinking water a compelling challenge, especially in groundwater. This comprehensive review collates information regarding the prevalence of arsenic contamination in water worldwide and its impact on human health, its chemical behaviour, methods for detection and quantification, and treatment strategies. A comprehensive search was conducted, and the selection of eligible studies was carried out using the PRISMA (the preferred reporting items for systematic reviews and meta-analyses) guidelines. Essential characteristics of eligible research studies were extracted based on geographical areas, origins, concentration levels and the magnitude of populations vulnerable to arsenic contamination in groundwater sources. Arsenic contamination of water affects over 100 countries including Canada, the United States, Pakistan, China, India, Brazil and Bangladesh, where hydrogeological conditions favour prevalence and groundwater is the primary water source for food preparation, irrigation of food crops and drinking water. This leads to human exposure through absorption, ingestion and inhalation, causing numerous health disorders affecting nearly all systems within the human body, with acute and chronic toxicity including cancers. The presence of arsenic in water poses a considerable challenge to humanity, prompting scientists to devise diverse mitigation approaches categorized as (a) oxidation processes, (b) precipitation methods, (c) membrane technologies, (d) adsorption and ion exchange methods, and (e) social interventions. This comprehensive review is expected to be a valuable source for professionals in the water industry, public management, and policymaking, aiding their ongoing and future research and development efforts. Full article

A microwave technique was used to prepare a superabsorbent polymer (SAP) by grafting two hydrophilic monomers onto a polysaccharide substrate. The monomers used were acrylic acid (AA) or acrylamide (AM) and were grafted onto a pullulan (PUL) substrate to form PUL-g-AA (SAP₁) and PUL-g-AM (SAP₂), respectively. The monomers (AM/AA) were grafted together onto a PUL substrate to form PUL-g-(AM/AA) (SAP₃). Grafting parameters such as grafting efficiency with the percentage, the conversion of monomer into polymer, gel content, water retention, water adsorption capacity, and swelling kinetics were determined. Additionally, the effect of environmental pH (2, 4, 7, 9, and 12) and sodium dodecylbenzene sulfonate (SDBS) surfactant was evaluated, where 1, 2, 3, 4, and 5 mM of SDBS was added to form SAP₄ to SAP₈. The FTIR results show that AM was grafted onto PUL through an aliphatic C-N bond, while AA grafting occurred through a single C-C bond. The grafting efficiency with AM was higher than with AA, as well as showing a superior gel content. Water absorbance capacity and water retention increased with the grafting of AA and AM together for SAP₃. The highest absorbent capacity, water retention, gel content, and grafting parameters values were obtained with a 3 mM SDBS content and a pH of 7. The swelling kinetics showed that the increases in the theoretical and experimental swelling equilibriums were 72% and 82%, respectively, for SAP₆ compared to the values of these parameters for SAP_3. The water absorption capacity of the hydrogel increases upon increasing the pH to 7 and then gradually decreases. XRD demonstrated the improved crystallinity and crystalline size of the hydrogel after grafting polymerization of AM/AA onto PUL, in addition to enhanced thermal stability. On the contrary, FE-SEM demonstrated that SDBS improves the porosity and pore size of the hydrogel surface with SAP₆. Full article

Real textile wastewater (RTWW) poses significant environmental challenges. RTWW typically contains high levels of organic compounds, such as dyes, as well as inorganic substances like salts. These contaminants can harm aquatic life when released into water bodies without appropriate treatment. RTWW was subjected to a series of sequential treatments: exchange resins for removing ions, advanced oxidation with bicarbonate-activated peroxide to degrade organic matter, and a biological treatment based on the Zahn–Wellens test to remove remaining chemical oxygen demand (COD) The advanced oxidation process based on the activation of H₂O₂ with NaHCO₃ (catalyzed with cobalt impregnated on a pillared clay, Co/Al–PILC)) was optimized using central composite design (CCD) and response surface methodology (RSM). After the process integration, reductions in ion concentrations, chemical oxygen demand (COD), and total organic carbon content (TOC) were achieved. Reduced hardness (99.94%) and ions (SO₄²⁻ and acid black 194 dye of 99.88 and 99.46%, respectively), COD (96.64%), and TOC (96.89%), guaranteeing complete treatment of RTWW, were achieved. Additionally, the biodegradability index of RTWW increased from 0.28 ± 0.01 to 0.90 ± 0.01, and phytotoxicity was reduced, going from a phytotoxic that inhibited the germination of lettuce seeds to a phytostimulant after biological treatment with activated sludge. Full article

Photocatalytic methods have been popular in energy production and environmental remediation. Designing high-efficiency photocatalysts is still challenging in converting solar energy into chemical fuels. Herein, a series of surfactant-assisted ZnIn₂S₄ (ZIS) photocatalysts were synthesized by utilizing the one-pot hydrothermal method. Photocatalytic methane production from an acetic acid solution was carried out under LED light (450 nm) irradiation, and the evolved gas was analyzed by the GC-FID system. Reaction factors (surfactant amount, catalyst dose, reaction temperature, substrate concentration, and reaction pH) were optimized for photocatalytic production. With the increase in cetyltrimethylammonium bromide (CTAB) amount, CH₄ production gradually increased. The ZIS-3.75 photocatalyst exhibited the highest photocatalytic CH₄ production rate (0.102 µmol g⁻¹·h⁻¹), which was approximately 1.8 times better than that of pure ZIS (0.058 µmol g⁻¹·h⁻¹). The presence of CTAB reduced the charge transfer resistance and improved photocurrent response efficiency. Structure and morphology were characterized by XRD, FTIR, SEM, TEM, and N₂ adsorption–desorption isotherm analysis. Optical properties were investigated by UV-DRS and PL spectroscopic techniques. The electrochemical evaluation was measured through EIS, Mott–Schottky, and transient photocurrent response analysis. The CTAB-modified catalyst showed excellent stability and reusability, even after five irradiation cycles. Methane production was enhanced by lowering the photogenerated charge transfer resistance and boosting the dispersion of ZIS-3.75 under visible light (450 nm) irradiation. Full article

Under the umbrella of Blue Economy, research interest is focused on harnessing the potential of macroalgae biomass, known as third-generation feedstock, from which multiple products can be extracted. As many of these exploitation pathways are not yet feasible for large-scale implementation, a significant number of publications adopt LCA as a tool to assess the sustainability of the proposed value chains. However, the complexity of such systems and the broad spectrum of alternative routes render a vague perspective on the sustainability of such applications. This study provides a critical review of previous research employing LCA to evaluate different pathways of macroalgae utilization. Ethanol, energy (biogas), and nutrition products were found to be among the most studied outputs in the past ten years from an LCA perspective. Different pathways leading to these products were mapped and analyzed, documenting their critical points and proposing measures to mitigate their environmental impact. A thorough SWOT analysis compiles for the first time the scattered information available in the literature, giving insights into the current state of macroalgae use and motives for further research. Insufficient or outdated inventory data for LCA, coupled with technical and technological struggles, were found to be the main barriers to large-scale applications. Full article

The production of polyhydroxyalkanoates using submerged cultures of Cupriavidus necator DSM 428 was evaluated using low-cost substrates from agroindustry: (i) dextrose from cassava starch and (ii) a mixture of sugarcane vinasse from the bioethanol industry and dextrose from cassava starch. The effects of vinasse composition (2.5, 5.0, 7.5, 25, 50, and 75% v/v) and the use of raw and activated carbon-pre-treated vinasse were assessed. The results indicate that cultivations using only cassava starch dextrose reached 4.33 g/L of biomass as the dry cell weight and a poly(3-hydroxybutyrate) (PHB) production of 47.1%. Raw vinasse proportions of 25, 50, and 75% in the culture medium resulted in total inhibition. Vinasse treated at the same ratios led to biomass production in the range 1.7–4.44 g/L. The higher PHB production scenario was obtained in a medium containing dextrose and treated vinasse (7.5%), yielding 5.9 g/L of biomass and 51% of PHB accumulation. The produced PHB was characterized by XRD and FTIR for an analysis of crystalline structure and chemical functional groups, respectively. EDS was employed for a semi-quantitative analysis of the chemical composition, and SEM was used to analyze the morphology of the microgranules. The results of DSC and TGA analyses demonstrated the thermal stability of the obtained PHB. Full article

One interesting method for environmental remediation is the use of ZnO/ZrO₂ composites in the photocatalytic degradation of lead (Pb) in wastewater. Several studies have investigated different types of composites for the removal of heavy metals from wastewater. However, the efficiency of these composites in removing the heavy metals remains debatable. Hence, this study investigated the potential of using a ZnO/ZrO₂ composite for the removal of Pb from wastewater. Response surface methodology (RSM) was utilized in this work to maximize the Pb photocatalytic removal over ZnO/ZrO₂ in simulated wastewater. Based on a central composite design (CCD), the experimental design included adjusting critical process parameters such as catalyst dosage, initial Pb concentration, and pH. The ZnO/ZrO₂ composite was synthesized using a physical mixing technique, and its physicochemical properties were studied by field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), Fourier transform infra-red (FTIR), and X-ray diffraction (XRD). Under visible light irradiation, photocatalytic Pb removal tests were carried out in a batch reactor. The findings showed that a ZnO/ZrO₂ dose of 100 mg/L, a pH of 10, and an initial Pb content of 15 ppm were the optimal conditions for maximal Pb removal (above 91.2%). The actual Pb removal obtained from the experimental runs was highly correlated with that predicted using the RSM quadratic model. The usefulness of ZnO/ZrO₂ composites for photocatalytic Pb removal is demonstrated in this work, which also emphasizes the significance of RSM in process parameter optimization for improved pollutant degradation. The models that have been proposed offer significant perspectives for the development and scalability of effective photocatalytic systems intended to remove heavy metals from wastewater. Full article

The study examined the chemical structure of azo-based liquid crystalline compounds that were altered to form a branch of cyclotriphosphazene. Moreover, the research explored the interplay between their mesomorphic and dielectric properties. The structures of the compounds were defined by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, and CHN elemental analysis. Only intermediates 2a–e and cyclotriphosphazene compounds 4d–e were mesogenic with smectic A (SmA) and smectic C (SmC) phases, respectively. Intermediate 2d and compound 4d were used as representative samples to determine the type of liquid crystal, which was confirmed through X-ray diffraction (XRD). The calculated d/L ratios for both compounds were 1.69 and 0.76, respectively, indicating that d was approximately equal to L (d ≈ L ≈ 1). This finding suggests that the SmA and SmC phases observed under polarized optical microscope (POM) are arranged in a monolayer. For the dielectric study, only compounds 2d–e and 4d–e were proceeded and compared for dielectric characteristics testing. The dielectric constants and dielectric loss factors of these four compounds were measured over the frequency range of 100 Hz to 0.1 MHz at room temperature. The dielectric constant trend decreased with the increasing frequency. Meanwhile, the dielectric loss showed two types of trends. The first trend was identical to the dielectric constant trend, in which the dielectric loss decreased as the frequency increased. However, in the second trend, the dielectric loss began to rise with the increase in frequency and then began to fall gradually after reaching a certain peak. Meanwhile, compounds 4d and 4e had low dielectric constants and losses due to the effect of hexasubstituted cyclotriphosphazene that had been attached as a core. Full article

Cu–Be alloys are renowned for their exceptional mechanical and electrical properties, making them highly sought after for various industrial applications. This study presents a comprehensive approach to predicting the compositions of various types of Cu–Be alloys, integrating a Random Forest Regressor within a machine learning (ML) framework to analyze an extensive dataset of chemical and thermo-mechanical parameters. The research process incorporated data preprocessing, model training and validation, and robust analysis to discern feature significance. Cluster analysis was also conducted to illuminate the data’s intrinsic groupings and to identify underlying metallurgical patterns. The model’s predictive power was confirmed by high R² values, indicative of its capability to capture and explain the variance in the dataset for both testing (R² = 0.99375) and training (R² = 0.99858). Distinct groupings within the alloy data were uncovered, revealing significant correlations between composition, processing conditions, and alloy properties. The findings underscore the potential of ML techniques in advancing the material design and optimization of Cu–Be alloys, providing valuable insights for the field of material science. Full article

Natural compounds are becoming increasingly popular in the fields of pharmaceuticals and cosmetics. One such compound is lignin, a plant-derived aromatic polymer that serves as a natural anti-ultraviolet agent. Conventional methods for extracting lignin from plant materials typically involve performing procedures in harsh environments, such as dissolving it in highly alkaline solutions or subjecting it to treatment in acidic conditions. In this study, lignin was extracted from coconut husk under milder conditions, using neutral solvents and ultrasonic treatment, which allowed us to obtain lignin with significantly improved properties. The developed method facilitated the creation of light-colored lignin, which was employed as a natural ingredient in sunblock cream. Furthermore, for the sake of comparison, lignin was extracted under more rigorous conditions using the traditional method. The research findings confirm that the light-colored lignin sample exhibits a higher level of UV absorption. Furthermore, light-colored lignin demonstrates a synergistic effect when combined with commercial moisturizing creams and sunscreens, leading to a significant enhancement in their SPF performance against both UVA and direct sunlight exposure. This study highlights the potential value of incorporating lignin as a valuable natural ingredient in sunblock and cosmetic products. Full article

Consumers’ growing knowledge of healthy, environmentally friendly flavors and scents drives the demand for vanillin bioproduction. To save costs on nitrogen during the bioproduction of vanillin, this study investigated the feasibility of using corn steep as a substitute. Using the response surface methodology (RSM) model, the synergistic effects of three variables on vanillin yield were evaluated using Box–Behnken design (BBD). When corn steep liquid, ferulic acid concentration, and pH were 7.72 g/L, 2.33 g/L, and 9.34, respectively, the highest vanillin production of 386 mg/L was achieved. The findings indicated that a maximum overall desirability (D) of 1.0 and a significant (p < 0.05) quadratic model with a regression coefficient (R²) of 0.995 can be used to establish ideal circumstances for the bioproduction of vanillin. This study demonstrated the effectiveness of using corn steep liquor as a low-cost nitrogen source in the medium formulation for the extraction and production of vanillin. Full article

Textile industry effluents contain several hazardous substances, such as dye-containing effluents, which pose environmental and aesthetic challenges. Presently, the microbial-based remediation process is in use. This study investigated the application of ferrous–ferric oxide (Fe₃O₄) nanoparticles, a readily formulated nanoadsorbent, to remove scattered dye molecules from industrial effluents. The ferrous–ferric oxide nanoparticles were prepared using a chemical co-precipitation method. The nanoparticles had 26.93 emu g⁻¹ magnetization, with sizes smaller than 20 nm, and possessed a highly purified cubic spinel crystallite structure. The catalytic activity of the iron oxide depended on the dose, photocatalytic enhancer, i.e., H₂O₂ level, pH of the reaction medium, and dye concentration. We optimized the Fenton-like reaction to work best using 1.0 g/L of ferrous–ferric oxide nanoparticles, 60 mM oxalic acid at pH 7.0, and 60 ppm of dye. Iron oxides act as photocatalysts, and oxalic acid generates electron–hole pairs. Consequently, higher amounts of super-radicals cause the rapid degradation of dye and pseudo-first-order reactions. Liquid chromatography–mass spectrometry (LC-MS) analysis revealed the ferrous–ferric oxide nanoparticles decolorized and destroyed Disperse Red 277 in 180 min under visible light. Hence, complete demineralization is observed using a photo-Fenton-like reaction within 3 h under visible light. These high-capacity, easy-to-separate next-generation adsorption systems are suggested to be suitable for industrial-scale use. Ferrous–ferric oxide nanoparticles with increased adsorption and magnetic properties could be utilized to clean environmental pollution. Full article

Supramolecular chemistry is a relatively new field of study that utilizes conventional chemical knowledge to produce new edges of smart materials. One such material use of supramolecular chemistry is the development of sensing platforms. Biologically relevant molecules need frequent assessment both qualitatively and quantitatively to explore several biological processes. In this review, we have discussed supramolecular sensing techniques with key examples of sensing several kinds of bio-analytes and tried to cast light on how molecular design can help in making smart materials. Moreover, how these smart materials have been finally used as sensing platforms has been discussed as well. Several useful spectroscopic, microscopic, visible, and electronic outcomes of sensor materials have been discussed, with a special emphasis on device-based applications. This kind of comprehensive discussion is necessary to widen the scope of sensing technology. Full article

This study aims to investigate the thermohydraulic performance of silver nanofluids with different surface modifications (citrate, lipoic acid, and silica) in turbulent convective heat transfer applications. Three silver nanofluids were prepared, each modified with citrate, lipoic acid, or silica coatings. The nanofluids were characterized for stability using zeta potential measurements and evaluated in a smooth brass tube under turbulent flow conditions. The experimental setup involved measuring the temperature, pressure, and flow rate to assess heat transfer coefficients, pressure drops, and friction factors. The results were compared with distilled water as the base fluid and validated against theoretical models. The silica-shelled nanofluid (Ag/S) exhibited a significant 35% increase in the average heat transfer coefficient compared to distilled water, while the citrate-coated (Ag/C) and lipoic acid-coated (Ag/L) nanofluids showed slight decreases of approximately 0.2% and 2%, respectively. The Ag/S nanofluid demonstrated a 9% increase in the mean Nusselt number, indicating enhanced heat transfer capabilities. However, all modified nanofluids experienced higher pressure drops and friction factors than the base fluid, with the Ag/S nanofluid showing the highest increase in viscosity (11.9%). Surface modifications significantly influence the thermohydraulic performance of silver nanofluids. The silica-shelled nanofluid shows the most substantial enhancement in heat transfer, making it a promising candidate for applications requiring efficient thermal management. However, the increased hydraulic costs associated with higher-pressure drops and friction factors must be carefully managed. Further research is needed to optimize these nanofluids for specific industrial applications, considering long-term stability and the effects of different nanoparticle concentrations and geometries. Full article

The increasing global focus on green nanotechnology research has spurred the development of environmentally and biologically safe applications for various nanomaterials. Nanotechnology involves crafting diverse nanoparticles in terms of shapes and sizes, with a particular emphasis on environmentally friendly synthesis routes. Among these, biogenic approaches, including plant-based synthesis, are favored for their safety, simplicity, and sustainability. Silver nanoparticles, in particular, have garnered significant attention due to their exceptional effectiveness, biocompatibility, and eco-friendliness. Cannabis (Cannabis sativa L.) has emerged as a promising candidate for aiding in the green synthesis of silver nanoparticles. Leveraging the phytochemical constituents of Cannabis, researchers have successfully tailored silver nanoparticles for a wide array of applications, spanning from biomedicine to environmental remediation. This review explores the properties, synthesis mechanisms, and applications of silver nanoparticles obtained from Cannabis. Additionally, it delves into the recent advancements in green synthesis techniques and elucidates the optical properties of these nanoparticles. By shedding light on plant-based fabrication methods for silver nanoparticles and their diverse bionanotechnology applications, this review aims to contribute to the growing body of knowledge in the field of green nanotechnology. Through a comprehensive examination of the synthesis processes, mechanistic aspects, and potential applications, this review underscores the importance of sustainable approaches in nanoparticle synthesis and highlights the potential of Cannabis-derived silver nanoparticles in addressing various societal and environmental challenges. Full article