Search Results (2,214)

The uncontrolled discharge of synthetic azo dyes such as methyl orange (MO) into water bodies has become a major environmental concern because of their strong chemical stability, limited biodegradability, and harmful effects on aquatic ecosystems. In this study, MgNiFe layered double hydroxides (LDHs) were synthesized through a co-precipitation route using a molar ratio of (Mg + Ni)/Fe equal to 3, and their adsorption ability toward MO in aqueous media was investigated. The prepared materials were characterized by X-ray diffraction (XRD), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM–EDX), Fourier-transform infrared spectroscopy (FTIR), and inductively coupled plasma atomic emission spectroscopy (ICP-AES). The characterization results revealed the successful formation of a hydrotalcite-like layered structure with good crystallinity, a relatively uniform distribution of metallic species, and the incorporation of carbonate anions within the interlayer galleries. In addition, the adsorption performance was evaluated by studying the effects of several operational factors, namely adsorbent dosage, initial pH, and contact time. To better understand the interaction between these parameters and identify the optimum operating conditions, a Box–Behnken response surface design was applied. The results indicate solution pH is the most influential parameter in the adsorption process. Under optimized conditions, a maximum removal efficiency of 86.86% was obtained, corresponding to an adsorption capacity of approximately ~86.86 mg·g⁻¹ (based on 100 mL solution volume). The enhanced adsorption performance may be attributed to the combined effect of the multivalent metal cations (Mg²⁺, Ni²⁺, and Fe³⁺), likely increases the surface positive charge density of the LDH and promotes interactions with anionic dye molecules. These interactions are suggested to involve electrostatic attraction and possible surface adsorption processes. However, in the absence of post-adsorption characterization, the exact adsorption mechanism remains hypothetical. Overall, the results demonstrate the promising potential of MgNiFe LDHs as efficient adsorbent materials for the treatment of dye-contaminated wastewater. Full article

This study presents the synthesis and use of a novel bamboo-derived magnetic activated carbon (BMAC) for the effective removal of cationic and anionic dyes, specifically methylene blue (MB), methyl orange (MO), and sunset yellow (SY), from aqueous solutions. The adsorbent was synthesized using thermal carbonization and subsequent inclusion of magnetic oxide, yielding a porous structure with improved adsorption and magnetic separation properties. Thorough characterization utilizing SEM, EDX, BET, FTIR, XRD, and TGA/DTA validated the creation of a highly porous material including uniformly dispersed magnetic particles and several surface functional groups. Batch adsorption tests were performed to examine the influences of contact time, adsorbent dosage, initial dye concentration, pH, and temperature. The findings indicated rapid adsorption kinetics, with equilibrium reached in around 60–70 min, and adsorption capacity ranked as MB > MO > SY. Augmenting adsorbent dosage enhanced removal efficiency but diminished adsorption capacity per unit mass due to site unsaturation. The maximum adsorption capacities (q_m) of BMAC were 58.9, 56.3, and 32.7 mg/g for MB, MO, and SY, respectively, as determined from the Langmuir isotherm model, indicating superior performance compared with other reported magnetic activated carbon. The adsorption process was determined to be exothermic and spontaneous, as evidenced by thermodynamic characteristics. The equilibrium data were optimally characterized by the Langmuir isotherm model, indicating monolayer adsorption, whereas the kinetic studies conformed to the pseudo-second-order model, signifying that chemisorption is predominant. The adsorption mechanism encompasses electrostatic interactions, π–π stacking, hydrogen bonding, van der Waals forces, pore filling, and surface complexation with magnetic oxides. The findings indicate that BMAC is an efficient, sustainable, and magnetically recoverable adsorbent for the elimination of both cationic and anionic dyes from wastewater. Full article

A major challenge in wastewater treatment lies in developing cost-effective and sustainable adsorbent materials for efficient dye removal. In this study, a novel biochar functionalized with MgO nanoparticles derived from palm leaf waste (MgO/PLB nanoparticles) was synthesized and evaluated for the removal of Congo red (CR) from aqueous solutions. FTIR, SEM, BET, and TGA investigations were used to thoroughly analyze the produced nanocomposite’s physicochemical properties. FTIR analysis verified the successful incorporation of MgO nanoparticles, as evidenced by the presence of characteristic Mg–O vibrations and noticeable changes in surface functional groups. SEM analysis revealed a transformation from a compact structure to a rough, particle-decorated morphology, indicating increased surface heterogeneity. BET analysis indicated the development of mesoporous structures, accompanied by a substantial increase in specific surface area from 2 to 178 m²/g. TGA results further confirmed enhanced thermal stability, indicating the formation of a structurally robust adsorbent. Batch adsorption tests showed that CR removal depends on pH, dosage, concentration, and contact time, with maximum efficiency (~99%) achieved at pH 4 using 0.03 g of adsorbent. The adsorption followed pseudo second order kinetics and was best described by the Langmuir isotherm, with a maximum capacity of 23.4 mg/g. The regenerated nanomaterial retained more than 89% of its adsorption capacity after four successive cycles, demonstrating good reusability and stability. The developed MgO/PLB nanoparticles exhibit efficient adsorption performance, combined with low-cost synthesis and the utilization of abundant agricultural waste, making it an affordable and long-lasting adsorbent for applications involving wastewater treatment. Full article

The development of adsorbents with high adsorption capacity, easy separation, and good reusability is critical for the treatment of dye-contaminated wastewater. Herein, a novel magnetic composite hydrogel, P(AA-AM)/SA-BC-Fe₃O₄, was synthesized via free radical polymerization, integrating acrylic acid (AA), acrylamide (AM), sodium alginate (SA), biochar (BC), and magnetic Fe₃O₄ nanoparticles. The material was systematically characterized by FTIR, XRD, SEM, BET, and VSM, which confirmed the successful formation of a three-dimensional porous network with well-dispersed Fe₃O₄ nanoparticles and BC, endowing the hydrogel with superparamagnetic properties. The adsorption performance of the hydrogel towards methylene blue (MB) was evaluated under various conditions. The results demonstrated that the adsorption process followed the pseudo-second-order kinetic model and the Langmuir isotherm, indicating that chemisorption is an important mechanism in the monolayer adsorption process. The hydrogel exhibited excellent swelling properties and remarkable pH-dependent adsorption behavior, with optimal performance in weakly alkaline environments. Notably, the incorporation of BC enhanced the adsorption capacity, while Fe₃O₄ enabled rapid magnetic separation, with the adsorbent retaining approximately 77% of its initial capacity after five regeneration cycles. This work presents a promising strategy for constructing magnetic hydrogel adsorbents that synergistically combine high adsorption efficiency, facile separability, and good reusability for practical wastewater treatment applications. Full article

The adsorption and desorption behavior of the azo dye Orange II (OII) was investigated using composite beads prepared from shrimp shell–derived chitosan (50 wt%) and montmorillonite-rich clay. The structural and morphological properties of the synthesized beads were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and FT-IR (Fourier Transform Infrared Spectroscopy). Batch adsorption experiments were performed to evaluate the removal efficiency of OII from aqueous solutions under various conditions, revealing that a low adsorbent dosage (0.5 g L⁻¹) and an acidic medium (pH 4) provided optimal adsorption performance. Adsorption kinetics and equilibrium isotherms were analyzed to elucidate the adsorption mechanism. Thermodynamic parameters indicated that the adsorption process was spontaneous (ΔG° < 0) and endothermic (ΔH° > 0). Equilibrium data were fitted to both Langmuir and Freundlich isotherm models, with the Freundlich model providing the best correlation (R² = 0.99), suggesting multilayer adsorption on a heterogeneous surface. The adsorption capacity increased significantly with temperature, rising from 98.35 mg g⁻¹ at 298 K to 182.57 mg g⁻¹ at 318 K, further confirming the endothermic nature of the process. Kinetic analysis revealed relatively rapid adsorption, with maximum adsorption capacities increasing from approximately 100 mg g⁻¹ at 25 °C to 123 mg g⁻¹ at 45 °C. Regeneration and reusability tests demonstrated that the composite beads could be reused through adsorption–desorption cycles; however, a gradual decline in removal efficiency was observed, decreasing from 97% in the first cycle to 25% after the fifth cycle. This decrease is likely associated with partial structural degradation or the detachment of bead components during repeated regeneration. Overall, the results highlight the potential of chitosan–clay composite beads as promising and sustainable adsorbents for the removal of azo dyes from aqueous media. Full article

In this study, a polyvinyl alcohol/carboxymethyl chitosan (PVA/CCTS) hydrogel was synthesized via free radical polymerization and employed for the adsorption of Rhodamine B (RhB) from aqueous solution. The hydrogel was systematically characterized by FTIR, SEM, XPS, and BET analyses, confirming its interconnected porous network and functional group composition. Under optimized conditions (adsorbent dosage = 0.1 g, pH = 6, RhB concentration = 65 mg·L⁻¹, and T = 298.15 ± 2 K), the maximum adsorption capacity reached 15.88 mg·g⁻¹. Kinetic analysis showed that the pseudo-second-order model best described the adsorption behavior under optimal conditions, indicating that the uptake of RhB is governed by multiple interaction mechanisms rather than simple physisorption alone. The equilibrium data were best fitted by the Freundlich isotherm (R² = 0.976), indicating surface heterogeneity of the hydrogel. Thermodynamic evaluation revealed an endothermic (ΔH = 28.38 ± 4.40 kJ·mol⁻¹), with adsorption efficiency improving at elevated temperatures. The hydrogel retained appreciable adsorption capacity after three adsorption–desorption cycles (5.78 mg·g⁻¹ at the third cycle). Density functional theory (DFT) calculations identified -COOH and -NH₂ groups as the primary active sites, and molecular electrostatic potential analysis confirmed that electrostatic interactions between the negatively charged hydrogel surface and cationic RhB drive the initial adsorption. Molecular dynamics (MD) simulations over 100 ns further demonstrated that van der Waals forces constitute the dominant driving force, supplemented by electrostatic interactions and hydrogen bonding, with the hydrogel’s cross-linked network stabilizing adsorbed RhB molecules. The integrated experimental computational approach provides a comprehensive mechanistic understanding of RhB adsorption on PVA/CCTS hydrogel, offering guidance for the rational design of polysaccharide-based adsorbents for dye-contaminated wastewater treatment. Full article

Hexagonal boron nitride (h-BN) is a chemically stable two-dimensional material whose wide band gap and low surface reactivity limit its performance in adsorption and photocatalysis, motivating strategies to tailor its structure. In this work, a mechanochemical approach combining high-energy ball milling with NaOH-assisted treatment was used to induce simultaneous exfoliation and hydroxylation of h-BN, promoting defect generation, reduced crystallinity, interlayer expansion, and incorporation of oxygen-containing groups (B-OH and B-O). These modifications led to band gap narrowing, increased surface polarity, and improved dispersion, enabling the formation of heterogeneous active sites. The hydroxylated material (BN-OH) exhibited high adsorption capacities of 248 mg/g for methylene blue (MB) and 215 mg/g for rhodamine 6G (R6G), following Freundlich behavior, indicative of heterogeneous adsorption governed by electrostatic interactions, π–π stacking, hydrogen bonding, and defect-mediated sites. Under solar irradiation, BN-OH achieved up to 99% degradation of both dyes, following predominantly pseudo-first-order kinetics and outperforming pristine BN; additionally, the kinetic behavior under solar conditions was successfully described using the Behnajady–Modirshahla–Ghanbary (BMG) model, which accurately predicts the two-stage degradation process. Scavenger experiments revealed that ⦁OH radicals dominate MB degradation, while ⦁OH, O₂⦁⁻, and h⁺ contribute to R6G removal. Overall, defect engineering and hydroxyl functionalization synergistically enhance photocatalytic performance, providing a scalable strategy for wastewater treatment. Full article

This work presents a novel one-step plasma–solution synthesis of Prussian Blue (PB) and copper hexacyanoferrate (Cu-PBA) nanoparticles via underwater pulsed DC discharge. For the first time, the direct plasma-assisted formation of these coordination polymers is reported. The obtained materials were examined by X-ray diffraction, Fourier-transform infrared spectroscopy, Raman spectroscopy, and scanning electron microscopy (SEM). These analyses confirmed that the desired phases had formed, along with small amounts of oxide byproducts (α-Fe₂O₃, CuO) arising from the erosion of the electrodes. Photocatalytic activity was evaluated through the degradation of organic dyes (Reactive Red 6C, Rhodamine B, and Methylene Blue) under UV-light irradiation. Both catalysts achieved complete dye degradation within 90 min of UV irradiation (after an initial 30 min dark adsorption step, total experiment time 120 min). Notably, selective performance was observed: PB exhibited higher activity toward the cationic dye Methylene Blue, while Cu-PBA was more effective for the anionic dye Reactive Red 6C. This selectivity is attributed to the specific oxide impurities forming heterojunctions that facilitate charge separation and generate distinct reactive oxygen species. The plasma–liquid method offers a rapid and environmentally benign route to functional PBA-based composites, with potentially scalable characteristics pending further engineering optimization. These findings highlight the potential of utilizing synthesis-induced impurities to tailor photocatalytic selectivity for water purification applications. Full article

Cyclic pollutants such as dyes, antibiotics, phenols and VOCs in water and atmosphere feature stable structures and are difficult to mineralize, which constitutes the core problem in current environmental governance. Semiconductor photocatalysis provides a green strategy for the advanced treatment of such pollutants. Electrospun black TiO₂/Ag-loaded SiO₂ nanofiber membranes have become a research hotspot owing to their multi-component synergistic advantages. This paper systematically reviews the preparation processes and structure regulation methods of electrospun SiO₂ nanofiber membranes; expounds the loading strategies of black TiO₂ and Ag nanoparticles, the interface regulation mechanisms and the synergistic photocatalytic mechanism of the ternary composite system; summarizes the application progress in the degradation of cyclic pollutants in water and atmospheric VOCs; and emphatically analyzes the performance characteristics and key issues in the ring-opening degradation of cyclic pollutants. Studies show that the high specific surface area and porous structure of SiO₂ nanofiber membranes offer excellent support for catalytic reactions. In addition, black TiO₂ achieves a full-spectrum response through defect engineering; the SPR effect and Schottky barrier of Ag significantly improve carrier separation efficiency; and the synergistic effect of the three components enhances the adsorption–catalytic degradation capacity. Current challenges remain in ring-opening efficiency and stability, requiring multi-method breakthroughs to overcome bottlenecks, clarify mechanisms and promote engineering applications. This paper provides theoretical references for the development of high-performance fiber-based photocatalytic materials and lays a foundation for the practical application of electrospun inorganic nanofiber membranes in the field of environmental catalysis. Full article

Covalent organic framework materials (COFs) are promising for pollutant adsorption owing to their high specific surface area, tunable pores and functional designability, but their microcrystalline powder form leads to poor mechanical strength and processability, limiting practical applications. This study presents a mild, eco-friendly strategy using polysulfonamide fiber (PSA) with excellent mechanical and thermal stability as the core matrix, and room-temperature-synthesized sulfonic acid-functionalized TFP-DABA-COFs as the shell layer. Via coaxial wet spinning, core–shell structured PSA-COF composite fibers were fabricated without harsh solvothermal conditions, improving COF dispersion and interfacial bonding. Characterizations revealed the fibers possessed favorable comprehensive properties: fracture strength of 14.97 MPa, elongation at break of 32.84%, specific surface area of 8 m²/g, and hierarchical porous structures dominated by micropores, with enhanced hydrophilicity beneficial to aqueous adsorption. Adsorption experiments on woven fabrics showed 93.6% methylene blue removal in 40 min and 98.9% in 120 min, following the quasi-second-order kinetics, indicating chemisorption (electrostatic attraction) as the main mechanism. This work provides a mild, green approach to prepare PSA-COFs core–shell fibers, effectively solving the formability and processing issues of COFs. Full article

This review analyzes the advances over a five-year period in the development of polymeric sorbents for the purification of aqueous media from key classes of pollutants: hydrocarbons (crude oil, diesel fuel), organic dyes, pharmaceuticals (antibiotics), pesticides, herbicides, volatile organic compounds, and polycyclic aromatic hydrocarbons. Attention is paid to the analysis of structure-property-performance relationships, with an emphasis on comparing materials derived from renewable natural feedstocks (such as cellulose, chitosan, terpenes, vegetable oils, and aloe vera) with synthetic polymers. The analysis reveals that biopolymer-based sorbents exhibit comparable or superior sorption capacities combined with environmental safety, biodegradability, and low cost. The key sorption mechanisms include physical adsorption, hydrophobic interactions, and electrostatic interactions. Despite persisting challenges related to scalability, stability in real-world environments, and the need for efficient regeneration protocols, a convergent approach that combines the advantages of modified natural polymers and functional synthetic components appears to be the most promising strategy for developing cost-effective and sustainable technologies for the restoration of water quality. Full article

Water contamination by arsenic(V) [As(V)] and Congo red (CR) dye poses concurrent threats to public health and aquatic ecosystems, particularly in regions where metallurgical and textile industries coexist. Developing a single adsorbent capable of simultaneously addressing these chemically distinct pollutants, while recovering value from the spent material remains an open challenge in sustainable water treatment. This study reports the synthesis and evaluation of a novel ternary MgZnFe-LDH/1,2,4-triazole composite (TM-LDH/TZ), engineered for the concurrent adsorptive removal of As(V) and CR, and the subsequent repurposing of the pollutant-loaded material as an electrocatalyst for the urea oxidation reaction (UOR). The composite was prepared via co-precipitation and triazole surface grafting, then characterized by FTIR, XRD, BET, TGA, FESEM, and HRTEM. Batch adsorption experiments examined the influence of pH, adsorbent dose, initial concentration, and temperature, with equilibrium data modeled through Langmuir, Freundlich, Temkin, and the statistically grounded Advanced Monolayer Model (AMM); kinetics were assessed using pseudo-first/second-order and Elovich models. Maximum Langmuir adsorption capacities reached 204.75 mg g⁻¹ for As(V) and 499.72 mg g⁻¹ for CR simultaneously at pH 5 and 25 °C, surpassing the majority of previously reported single-pollutant adsorbents. Elovich and pseudo-second-order kinetics confirmed chemisorption as the governing pathway for As(V) and CR, respectively, while AMM thermodynamic analysis verified spontaneous adsorption across all experimental conditions. The spent composite delivered a UOR peak current density of 184.67 mA cm⁻² that is nearly twice that of the fresh material, with a reduced charge-transfer resistance of 1.19 Ω, and removal efficiency remained above 85% through three successive regeneration cycles. The bifunctional design, coupling high-capacity dual-pollutant removal with catalytic valorization of waste, positions TM-LDH/TZ as a circular-economy-aligned platform for advanced water remediation. Full article

Emerging compounds in water, ranging from dyes to pharmaceuticals, negatively impact living organisms and challenge the industries responsible for their release. These pollutants exhibit chemical persistence and resistance to conventional treatment processes. Adsorption is considered an effective and accessible approach, particularly when low-cost and renewable materials are employed. The Problem-Intervention-Comparison-Outcome (PICO) framework and Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidelines were followed. A structured search of Scopus was conducted to identify English-language original peer-reviewed articles published between 2016 and 2025 addressing the use of fruit waste (FW)-derived adsorbents for water decontamination. After independent screening, 528 studies were included. Risk of bias was assessed qualitatively. Due to substantial heterogeneity in materials, contaminants, and experimental designs, findings were synthesized narratively. FW-derived adsorbents were evaluated in terms of synthesis routes, physicochemical characteristics, adsorption mechanisms, kinetic and equilibrium behavior, process optimization and regeneration performance. Correlations were observed between surface functionalization, material properties and contaminant-specific removal efficiency, while limitations were noted for multi-component systems, regeneration stability, standardization and scale-up. By integrating material design with process-level considerations, this review outlines priorities for advancing FW valorization toward practical and sustainable water treatment applications. Full article

The aim of this study was to produce and characterize a magnetic biocomposite based on aspen biochar, sodium alginate, and Phaffia rhodozyma yeast biomass, as well as to evaluate its suitability for removing methylene blue (MB) from aqueous solutions. The sorbent structure was confirmed by FTIR, XRD, and SEM, demonstrating successful immobilization of biotic components in an amorphous polymer matrix. Kinetic studies demonstrated a rapid process, with dynamic equilibrium established after 180 min. Experimental data from equilibrium studies (3 h and 24 h) were analyzed using the Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich models. The theoretical maximum sorption capacity (q_d) determined was 39.31 mg/g, with higher sorption values observed for 24 h confirming the contribution of intrapore diffusion and yeast biosorption activity. In temperature-effect studies, the highest process efficiency (q_e = 1.43 mg/g) was observed at 25 °C, while its decrease at 35 °C indicated the exothermic nature of the phenomenon and the thermal sensitivity of the biological structure. VSM analysis revealed superparamagnetic properties of the composite (Ms = 9.3 A·m²/kg), which enabled full phase separation. Regeneration studies demonstrated that despite the high efficiency of mineral acids, the use of ethanol as an eluent allows for maintaining the structural integrity of the sorbent and its effective use in at least four cycles. The results indicate that the developed biocomposite is a promising, low-cost, and easily recoverable alternative to conventional sorbents in industrial wastewater treatment technologies. Full article

Agricultural byproducts cellulose-rich (~40%) sugarcane bagasse (SCB) and rice husk (RH) wastes may be used as fiber sources in biomaterials manufacturing. The hybrid biomass fibers are two kinds of fibers that should generate a biocomposite according to the functions and physical, chemical, and mechanical properties of materials. The biocomposite was synthesized using the solvothermal method. The FeCl₃.6H₂O was dissolved in C₂H₃NaO₂ and C₆H₆O₂ and later heated at 60 °C. The SCB and RH fiber (1:1) are added with HDMA into the mixture, then placed in a Teflon stainless steel autoclave at 200 °C for 6 h. The biocomposite was employed as a green adsorbent to treat wastewater through simultaneous adsorption. The biocomposite had 2.637 mmol g⁻¹ of amine groups, which makes smaller magnetic particles and a high surface area of up to 79%. The pseudo-second-order kinetic model followed the Cu(II) and Pb(II) ions adsorption for 4 h (240 min), and the maximum adsorption capacities were 35.042 mg g⁻¹ and 67.127 mg g⁻¹, respectively, at the pH of 5. The biocomposite not only got rid of metal ions, but it also worked well to get rid of dye, total suspended solids (TSSs), and chemical oxygen demand (COD) as pollutants in wastewater. The biocomposite still worked well after being used four times. Full article