Search Results (4,427)

Water pollution has escalated to critical levels in recent years as evident by the multiplicity of contaminants found in potable water sources. A point-source major contributor is the textile industry, which discharges substantial amounts of dye into rivers and lakes. Bacterial cellulose (BC), a renewable and low-cost nanocellulose material, has emerged as a potential solution addressing dye removal from these contaminated waters. Methylene Blue (MB) was selected as a representative dye for our adsorption studies. As a baseline for evaluating efficacy, BC was dried using three different methods: freeze-drying, oven-drying, and room-temperature drying. The adsorptive behavior of these dried BC samples toward MB in an aqueous environment was evaluated. Furthermore, to elucidate the structure–property relationship of dried BC, several characterization techniques were employed. Our studies revealed that freeze-dried BC exhibited the highest initial adsorption rate, while oven-dried BC demonstrated the overall highest adsorption capacity. Moreover, the adsorption data corresponded well with pseudo-second-order and Freundlich isotherm models. This investigation provides a comprehensive understanding of how BC, dried through different methods, performs in the adsorption of MB by establishing a baseline for future research. Full article

The distribution characteristics of adsorbed CH₄ across pores of various sizes underpin coal mine gas disaster prevention, resource assessment, and efficient coalbed methane (CBM) extraction. Utilizing Grand Canonical Monte Carlo (GCMC) simulations as a theoretical framework, this study establishes a mathematical model linking microscopic pore structure to macroscopic CH₄ adsorption thermodynamics in coal. Results reveal that micropores (0.38–1.5 nm) dominate pore structures in coal. For micropores (0.419–1.466 nm), CH₄ adsorption follows the Dubinin-Astakhov (DA) equation. The adsorption parameters change significantly as pore diameter increases, indicating that micropore size distribution predominantly governs CH₄ adsorption in coal. For larger pores (1.619–4.040 nm), Langmuir equation analysis reveals no significant changes in CH₄ adsorption parameters with increasing pore size, suggesting that the CH₄ adsorption behavior in pore structures larger than 1.5 nm is relatively consistent and does not vary substantially with respect to pore size. The accuracy of the mathematical model improves with coal rank, reducing prediction errors from 35.371% to 11.044%. Decomposed CH₄ adsorption isotherms reveal that while CH₄ adsorption capacity increases with equilibrium pressure for all pores, smaller pores achieve saturation at lower pressures. The proportion of total adsorption attributed to smaller pores peaks before declining with further pressure increases. Full article

In this study, we developed a tapered optical fiber sensor enhanced with carbon quantum dots (CQDs) for the detection of 17-α-ethinylestradiol (EE2). The sensor operates on the changes in refractive index induced by the interaction between EE2 and antibodies on its surface. The incorporation of CQDs significantly increased the available surface area for receptor–analyte interactions, leading to enhanced sensor performance. The sensor demonstrated high sensitivity of 2.4925 nm/(ng/L) within a detection range of 1 to 10 ng/L, with a strong correlation coefficient (R² = 0.998). A detection limit as low as 0.0426 ng/L (0.144 pM) was achieved, along with a low dissociation constant of 2.19 × 10⁻¹¹ M as determined by the Langmuir isotherm model. These findings highlight the potential of the CQD-functionalized optical fiber sensors as a promising tool for sensitive and selective EE2 detection in environmental monitoring applications. Full article

Manganese (Mn) has emerged as a contaminant of concern due to its occurrence at concentrations exceeding regulatory limits in various environmental matrices, driven by both anthropogenic activities and natural geochemical processes. Although Mn is an essential micronutrient, excessive exposure poses risks to human health and ecosystems. This study investigates the potential application of Moringa oleifera seed pods, an agro-industrial byproduct, as low-cost biosorbents for Mn ion removal from aqueous solutions. Biosorbents were prepared from raw seed pods and chemically modified using NaOH and HCl. Surface characterization was performed using SEM, EDS, and FTIR techniques. Kinetic analysis indicated that Mn ion adsorption by all biosorbents followed a pseudo-second-order model, with equilibrium reached within 30 min. Among the tested materials, the alkali-treated biosorbent exhibited the highest removal efficiency (94%) under optimal conditions (288 K, pH 6.0, 60 min). Equilibrium data fitted both Langmuir and the Freundlich isotherms, with a maximum adsorption capacity of 7.64 mg g⁻¹ for alkali-treated pods and 6.00 mg g⁻¹ for the unmodified pods. Thermodynamic analysis revealed negative Gibbs free energy values, confirming the spontaneous nature of the biosorption process. Enthalpy values below 40 kJ mol⁻¹ (Pod_NA: 11.88 kJ mol⁻¹; Pod_AC: 1.08 kJ mol⁻¹; Pod_BA: 8.94 kJ mol⁻¹) suggest that physisorption is the predominant mechanism. These findings demonstrate the viability of Moringa oleifera pods as effective biosorbents for Mn ion remediation, supporting the valorization of agricultural waste within sustainable water treatment strategies. Full article

Sodium magadiite (Na-Mgd) was hydrothermally prepared and converted to its protonic (H-Mgd) form by reaction with hydrochloric (HCl) solution. The obtained products were studied as adsorbents for basic blue 41 (BB-41) removal from polluted aqueous solution. Na-Mgd and H-Mgd were characterized by different techniques. Powder X-ray (PXRD) diffraction data confirmed a pure Na-Mag phase and its conversion to acidic form (H-Mgd) with shift in d₀₀₁ value from 1.54 nm to 1.12 nm. X-ray fluorescence (XRF) data supported the exchange of Na cations by protons for H-Mag. ²⁹Si magic angle spinning nuclear magnetic resonance (MAS-NMR) indicated a change in the local environment of silicon nucleus when Na-Mgd was treated with HCl solution. The BB-41 removal dyes were investigated throughout the batch process. Effects of selected parameters, for example, the adsorbent dosage, pH of the BB-41 solution, pH of the H-Mag solid, and starting concentration, were explored. The equilibrium data were fitted to the Langmuir and Freundlich isotherm models. The maxima removal capacities of Na-Mgd and H-Mgd were 219 mg/g and 114 mg/g, respectively. The regeneration and reusability tests were performed using initial concentrations of 50 mg/L and 200 mg/L for seven cycles. The efficiency was maintained for 5 to 6 cycles with a decline of 10% using low initial concentration; however, a decline of efficiency to 30 to 50% was achieved when a higher initial concentration was employed after 3 to 4 regeneration tests for Na-Mgd and H-Mgd samples. Adsorber batch design using the Langmuir and Freundlich isotherm parameters was used to predict its performance for commercial usage. The predicted masses of H-Mgd were higher than those of Na-Mgd to treat different effluent volumes contaminated with 200 mg/L of BB-41 dyes at desired removal percentages. Full article

The optimization of polymer extrusion processes is crucial for improving product quality and manufacturing efficiency in plastic industries. This study aims to investigate the viscoelastic flow behavior of high-density polyethylene (HDPE) through an extrusion die with an internal mandrel, focusing on the effects of die geometry and flow parameters. A two-dimensional (2D) numerical model is developed in COMSOL Multiphysics using the Oldroyd-B constitutive equation, solved using the Galerkin/least-square finite element method. The simulation results indicate that the Weissenberg number (Wi) and die geometry significantly influence the dimensionless drag coefficient (Cd) and viscoelastic stress distribution along the die wall. Furthermore, filleting sharp edges of the die wall surface effectively reduces stress oscillations, enhancing flow uniformity. These findings provide valuable insights for optimizing die design and improving polymer extrusion efficiency. Full article

This study developed a novel adsorbent for Cr (VI) removal from wastewater by grafting N-[(dimethylamino)methylene]thiourea (TUFA) onto lignin. The resulting TUFA-functionalized lignin adsorbent AL was comprehensively characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), and X-ray photoelectron spectroscopy (XPS). Batch adsorption experiments systematically evaluated the influence of solution pH, contact time, temperature, initial Cr (VI) concentration, and adsorbent dosage. AL exhibited high adsorption capacity (593.9 mg g⁻¹ at 40 °C), attributed to its abundant nitrogen and sulfur-containing functional groups. Kinetic analysis revealed that the adsorption process followed pseudo-second-order kinetics. Equilibrium isotherm data were best described by the Langmuir model, indicating predominant monolayer chemisorption. Thermodynamic parameters demonstrated that Cr (VI) adsorption onto AL is spontaneous, endothermic, and entropy-driven. The adsorption mechanism involves membrane diffusion and intra-particle diffusion processes. This work successfully synthesized a stable, effective, and low-cost adsorbent (AL) using an amine agent incorporating both nitrogen and sulfur functional groups, offering a promising approach for treating Cr (VI)-contaminated wastewater. Full article

Phosphorus pollution represents a persistent and significant threat to aquatic ecosystems, particularly within the Mediterranean region, where ongoing eutrophication continues to compromise both water quality and biodiversity. Concurrently, the accumulation of Posidonia oceanica residues along coastal areas presents a biomass management challenge. This study explores the sustainable use of thermally treated Posidonia ash as a low-cost, bio-based adsorbent for phosphate removal from water. Batch experiments under varying phosphate concentrations, pH, hardness, and alkalinity revealed high removal capacities (33.5–58.7 mg/g). A novel surface complexation model (SCM) was developed and validated using spectroscopic techniques to elucidate the mechanisms of phosphate retention. The SCM outperformed conventional isotherm models by providing mechanistic insights into adsorption behavior. Phosphate adsorption was found to be pH-dependent, occurring via surface complexation to neutral and basic surface sites. The release of Ca²⁺ and Mg²⁺ ions facilitated ternary complex formation and precipitation. Under alkaline conditions, competitive adsorption between phosphate and carbonate ions was observed. This study demonstrates the dual benefit of Posidonia oceanica ash: efficient phosphate removal and its reuse as a phosphorus reservoir, offering a circular strategy for tackling nutrient pollution and promoting coastal biomass valorization. Full article

Practical applications such as solar power energy systems, electronic cooling, and the convective drying of vented enclosures require continuous developments to enhance fluid and heat flow. Numerous studies have investigated the enhancement of heat transfer in L-formed vented cavities by inserting heat-generating components, filling the cavity with nanofluids, providing an inner rotating cylinder and a phase-change packed system, etc. Contemporary work has examined the thermal performance of L-shaped porous vented enclosures, which can be augmented by using metal foam, using nanofluids as a saturated fluid, and increasing the wall surface area by corrugating the cavity’s heating wall. These features are not discussed in published articles, and their exploration can be considered a novelty point in this work. In this study, a vented cavity was occupied by a copper metal foam with $PPI=10$ and saturated with a copper–water nanofluid. The cavity walls were well insulated except for the left wall, which was kept at a hot isothermal temperature and was either non-corrugated or corrugated with rectangular waves. The Darcy–Brinkman–Forchheimer model and local thermal non-equilibrium models were adopted in momentum and energy-governing equations and solved numerically by utilizing commercial software. The influences of various effective parameters, including the Reynolds number ($20\le Re\le 1000$), the nanoparticle volume fraction ($0\%\le \phi \le 20\%$), the inflow and outflow vent aspect ratios ($0.1\le D/H\le 0.4$), the rectangular wave corrugation number ($N=5$ and $N=10$), and the corrugation dimension ratio ($CR=1$ and $CR=0.5$) were determined. The results indicate that the flow field and heat transfer were affected mainly by variations in $Re$, $D/H$, and $\phi$ for a non-corrugated left wall; they were additionally influenced by $N$ and $CR$ when the wall was corrugated. The fluid- and solid-phase temperatures of the metal foam increased with an increase in $Re$ and $D/H$. The fluid-phase Nusselt number near the hot left sidewall increased with an increase in $\phi$ by $\left(25–60\right)\%$, while the solid-phase Nusselt number decreased by $\left(10–30\right)\%$, and these numbers rose by around $3.5$ times when the Reynolds number increased from $20$ to $1000$. For the corrugated hot wall, the Nusselt numbers of the two metal foam phases increased with an increase in $Re$ and decreased with an increase in $D/H$, $CR$, or $N$ by $10\%$, $19\%$, and $37\%$. The original aspect of this study is its use of a thermal, non-equilibrium, nanofluid-saturated metal foam in a corrugated L-shaped vented cavity. We aimed to investigate the thermal performance of this system in order to reinforce the viability of applying this material in thermal engineering systems. Full article

Soil contamination with heavy metals often resulting from industrial activities and wastewater discharge is a major ecological problem. Bone meal, a by-product of the agri-food industry, is a promising material for remediating soils affected by heavy metal pollution. Bone meal, rich in phosphorus, calcium, and other essential minerals, provides advantages both in immobilizing inorganic pollutants and in improving soil fertility. This study explores the potential of bone meal as an ecological and sustainable solution for the retention of zinc from soils polluted with wastewater. This study analyzes the physicochemical properties of bone meal, the mechanisms of its interaction with metal ions through adsorption processes as revealed by equilibrium and kinetic studies, and its effects on plant germination. The results indicate a maximum adsorption capacity of 2375.33 mg/kg at pH = 6, according to the Langmuir model, while the pseudo-second-order kinetic model showed a coefficient of R² > 0.99, confirming the chemical nature of the adsorption. At pH 12, the retention capacity increased to 2937.53 mg/kg; however, parameter instability suggests interference from precipitation phenomena. At pH 12, zinc retention is dominated by precipitation (Zn(OH)₂ and Zn–phosphates), which invalidates the Langmuir assumptions; accordingly, the Freundlich isotherm provides a more adequate description. Germination tests revealed species-specific responses to Zn contamination and bone meal amendment. In untreated contaminated soil, germination rates were 84% for cress, 42% for wheat, and 50% for mustard. Relative to the soil + bone meal treatment (100% performance), the extent of inhibition reached 19–21% in cress, 24–29% in wheat, and 12% in mustard. Bone meal mitigated Zn-induced inhibition most effectively in wheat (+31% vs. soil; +40% vs. control), followed by cress (+23–27%) and mustard (+14%), highlighting its species-dependent ameliorative potential. Thus, the experimental results confirm bone meal’s capacity to reduce the mobility of zinc ions and improve the quality of the agricultural substrate. By transforming an animal waste product into a material with agronomic value, this study supports the integration of bone meal into modern soil remediation strategies, aligned with the principles of bioeconomy and sustainable development. Full article

Addressing the challenge of sulfonated lignite (SL) removal from oilfield wastewater, this study introduces a novel hierarchical MgFe-layered double hydroxide (LDH) adsorbent. The material was fabricated via in situ co-precipitation, utilizing a template formed by the NaCl-induced co-assembly of oleylaminopropyl betaine (OAPB) and sodium dodecyl sulfate (SLS) into zwitterionic, anionic, shear-responsive viscoelastic gels. This gel-templating approach yielded an LDH structure featuring a hierarchical pore network spanning 1–80 nm and a notably high specific surface area of 199.82 m²/g, as characterized by SEM and BET. The resulting MgFe-LDH demonstrated exceptional efficacy, achieving a SL removal efficiency exceeding 96% and a maximum adsorption capacity of 90.68 mg/g at neutral pH. Adsorption kinetics were best described by a pseudo-second-order model (R² > 0.99), with intra-particle diffusion identified as the rate-determining step. Equilibrium adsorption data conformed to the Langmuir isotherm, signifying monolayer uptake. Thermodynamic analysis confirmed the process was spontaneous (ΔG < 0) and exothermic (ΔH = −20.09 kJ/mol), driven primarily by electrostatic interactions and ion exchange. The adsorbent exhibited robust recyclability, maintaining over 79% of its initial capacity after three adsorption–desorption cycles. This gel-directed synthesis presents a sustainable pathway for developing high-performance adsorbents targeting complex contaminants in oilfield effluents. Full article

Excessive phosphorus emissions are a significant driver of severe eutrophication in water bodies, and developing an efficient and cost-effective adsorbent for phosphorus removal is imperative. In this study, a Na-type zeolite was synthesized from coal gangue sourced from an open-pit mine in Xinjiang province, China. The synthesis process involved drying, crushing, alkali activation, aging, hydrothermal crystallization, and Na⁺ ion exchange. Orthogonal design identified the optimal synthesis parameters: an alkali-to-ash ratio of 1:1, aging at 20 °C for 12 h, and crystallization at 130 °C for 12 h. Aging time exerted the greatest influence on the phosphate removal efficiency. The optimized zeolite exhibited excellent phosphate adsorption performance, achieving a removal efficiency of up to 96% and a capacity of 16 mg/g. The adsorption kinetics followed both pseudo-first-order and pseudo-second-order models, indicating processes governed by combined physical and chemical mechanisms. Isotherm data fitting with Freundlich and Langmuir models suggested the presence of both homogeneous and heterogeneous active sites. Thermodynamic studies confirmed a spontaneous and endothermic process, increasingly favorable at higher temperatures. Characterizations via scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray fluorescence (XRF) spectroscopy, and Fourier transform infrared (FTIR) spectroscopy confirmed the formation of Na-type zeolite and revealed structural and compositional changes following phosphate adsorption. Aluminum and calcium binding played key roles in the chemical adsorption mechanisms. This work not only offers a high-efficiency, low-cost solution for phosphorus removal from wastewater but also provides a sustainable pathway for the valorization of coal gangue in the Zhundong area of Xinjiang, China. Full article

Phenol and its derivatives in water and wastewater are highly toxic and challenging to degrade, posing serious environmental and health risks. Therefore, this research focuses on the removal of phenol from aqueous solutions using activated carbon made from Catha edulis stems. The activation process involved impregnating the Catha edulis stems with phosphoric acid followed by thermal treatment at 500 °C for 2 h. The resulting adsorbent was extensively characterized using various techniques, including Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), Brunauer–Emmett–Teller (BET) surface area analysis, and proximate analysis. Batch adsorption experiments were designed using a full factorial approach with four factors at two levels, resulting in 16 different experimental conditions. The characterization results showed that the activated carbon has a high surface area of 1323 m²/g, a porous and heterogeneous structure, and an amorphous surface with multiple functional groups. Under optimal conditions of pH 2, a contact time of 60 min, an adsorbent dosage of 0.1 g/100 mL, and an initial phenol concentration of 100 mg/L, the adsorbent achieved a phenol removal efficiency of 99.9%. Isotherm and kinetics analyses revealed that phenol adsorption fits the Langmuir model and pseudo-second-order kinetics, indicating a uniform interaction and chemisorptive process. This study highlights the effectiveness of Catha edulis stem-based activated carbon as a promising material for phenol removal in water treatment applications. Full article

In the context of circular economy, waste generated by fruit processing can be used to produce new materials with a wide range of uses. This study presents a method to synthesize biochar from peach kernel or grape pit waste. The adsorbents were tested in the removal of hexavalent chromium from synthetic wastewater with Cr⁶⁺ concentrations specific to plating processes. Characterization by BET, SEM, FTIR, and TG-DTG confirmed the formation of porous structures, and a well-functionalized surface. The effects of contact time, initial Cr⁶⁺ concentration, and adsorbent dose were investigated in static conditions. Both materials are efficient in hexavalent chromium removal, with sorption equilibrium achieved within 180 min. Kinetic studies indicated that the removal process follows a pseudo-second-order model. Equilibrium studies showed that optimal sorption occurred at pH = 6, with sorption capacities of 78.54 mg/g for biochar from peach kernels and 67.57 mg/g for biochar from grape pits. Hexavalent chromium followed a Sips adsorption isotherm for both biochars. Following the reusability study, it can be concluded that biochar from peach kernels maintains removal efficiency higher than 75% after four cycles. Full article

This study systematically investigated the dissolution equilibrium of lithium carbonate (Li₂CO₃) in mixed Na₂CO₃-NaCl aqueous solutions through isothermal dissolution experiments spanning 283.15–353.15 K. Precise solubility determinations were conducted using a gravimetric analysis under controlled thermodynamic conditions. The obtained solubility data were successfully correlated with the Extended Debye–Hückel (E-DH) model, yielding residual standard deviations below 0.09, which validates the model’s applicability in this ternary system. Both experimental observations and theoretical predictions confirmed that increasing the salt molality enhances the synergistic suppression of the Li₂CO₃ solubility through combined common-ion and salt effects. The thermodynamic analysis revealed the dissolution process to be exothermic (ΔH_d < 0), and entropy change dominates (ξ_S ≈ 78%), with negative entropy changes (ΔS_d < 0) indicating predominant hydration ordering effects. These mechanistic insights establish critical thermodynamic benchmarks for optimizing lithium carbonate precipitation processes in brine lithium extraction operations. Full article