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22 pages, 2605 KiB  
Article
Production of Bioadsorbents via Low-Temperature Pyrolysis of Exhausted Olive Pomace for the Removal of Methylene Blue from Aqueous Media
by Safae Chafi, Manuel Cuevas-Aranda, Mª Lourdes Martínez-Cartas and Sebastián Sánchez
Molecules 2025, 30(15), 3254; https://doi.org/10.3390/molecules30153254 - 3 Aug 2025
Viewed by 56
Abstract
In this work, biochars were produced by pyrolysis of exhausted olive pomace and evaluated as low-cost adsorbents for the removal of methylene blue (MB) from aqueous solutions. The biochar obtained at 400 °C for 1 h, which exhibited the best adsorption performance, was [...] Read more.
In this work, biochars were produced by pyrolysis of exhausted olive pomace and evaluated as low-cost adsorbents for the removal of methylene blue (MB) from aqueous solutions. The biochar obtained at 400 °C for 1 h, which exhibited the best adsorption performance, was characterized by FTIR, N2 adsorption–desorption isotherms, SEM-EDX, and proximate analysis, revealing a mesoporous structure with a relatively low specific surface area but enriched in surface functional groups, likely due to the partial degradation of lignocellulosic components. Adsorption experiments were conducted to optimize operational parameters such as solid particle size (2–3 mm), agitation speed (75 rpm), and bioadsorbent dosage (1 g per 0.05 L of MB solution), which allowed for dye removal efficiencies close to 100%. Kinetic studies showed that MB adsorption followed a pseudo-second-order model, while equilibrium data at 30 °C were best described by the Langmuir isotherm (R2 = 0.999; SE = 4.25%), suggesting monolayer coverage and strong adsorbate–adsorbent affinity. Desorption trials using water, ethanol, and their mixtures resulted in low MB recovery, whereas the addition of 10% acetic acid significantly improved desorption performance. Under optimal conditions, up to 52% of the retained dye was recovered. Full article
(This article belongs to the Special Issue Advances in Biomass Chemicals: Transformation and Valorization)
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20 pages, 2360 KiB  
Article
Enhanced Ammonium Removal from Wastewater Using FAU-Type and BEA-Type Zeolites and Potential Application on Seedling Growth: Towards Closing the Waste-to-Resource Cycle
by Matiara S. C. Amaral, Marcella A. da Silva, Giovanna da S. Cidade, Diêgo N. Faria, Daniel F. Cipriano, Jair C. C. Freitas, Fabiana Soares dos Santos, Mendelssolm K. Pietre and André M. dos Santos
Processes 2025, 13(8), 2426; https://doi.org/10.3390/pr13082426 - 31 Jul 2025
Viewed by 271
Abstract
This work focuses on the effectiveness of removing ammonium from real municipal wastewater using synthetic faujasite (FAU-type) and β (BEA-type) zeolites and a commercial β (BEA-type) sample. The results demonstrated that synthetic samples presented enhanced performance on ammonium removal in comparison with commercial [...] Read more.
This work focuses on the effectiveness of removing ammonium from real municipal wastewater using synthetic faujasite (FAU-type) and β (BEA-type) zeolites and a commercial β (BEA-type) sample. The results demonstrated that synthetic samples presented enhanced performance on ammonium removal in comparison with commercial zeolite due to higher Al content and larger specific surface area, promoting better accessibility to active adsorption sites of the adsorbents. Synthetic FAU-type and BEA-type zeolites achieved a maximum adsorption capacity of 28.87 and 12.62 mg·g−1, respectively, outperforming commercial BEA-type zeolite (6.50 mg·g−1). Adsorption assays, associated with kinetic studies and adsorption isotherms, were better fitted using the pseudo-second order model and the Langmuir model, respectively, suggesting that chemisorption, involving ion exchange, and monolayer formation at the zeolite surface, was the main mechanism involved in the NH4+ adsorption process. After ammonium adsorption, the NH4+-loaded zeolite samples were used to stimulate the growth of tomato seedlings; the results revealed a change in the biomass production for seedlings grown in vitro, especially when the BEA_C_NH4 sample was employed, leading to a 15% increase in the fresh mass in comparison with the control sample. In contrast, the excess of ammonium adsorbed over the BEA_S_NH4 and FAU_NH4 samples probably caused a toxic effect on seedling growth. The elemental analysis results supported the hypothesis that the presence of NH4+-loaded zeolite into the culture medium was important for the release of nitrogen. The obtained results show then that the investigated zeolites are promising both as efficient adsorbents to mitigate the environmental impact of ammonium-contaminated water bodies and as nitrogen-rich fertilizers. Full article
(This article belongs to the Special Issue Novel Applications of Zeolites in Adsorption Processes)
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13 pages, 4712 KiB  
Article
Adsorptive Removal Behavior of Two Activated Carbons for Bis(2-ethylhexyl) Phosphate Dissolved in Water
by Lifeng Chen, Jing Tang, Zhuo Wang, Hongling Wang, Wannian Feng, Junjie Chen, Qingqing Yan, Shunyan Ning, Wenlong Li, Yuezhou Wei and Di Wu
Toxics 2025, 13(8), 624; https://doi.org/10.3390/toxics13080624 - 25 Jul 2025
Viewed by 290
Abstract
Bis(2-ethylhexyl) phosphate (P204) is widely used in extraction processes in the nuclear and rare earth industries. However, its high solubility in water results in high levels of total organic carbon and phosphorus in aqueous environments, and may also lead to radioactive contamination when [...] Read more.
Bis(2-ethylhexyl) phosphate (P204) is widely used in extraction processes in the nuclear and rare earth industries. However, its high solubility in water results in high levels of total organic carbon and phosphorus in aqueous environments, and may also lead to radioactive contamination when it is used to combine with radionuclides. In this paper, we characterized a coconut shell activated carbon (CSAC) and a coal-based activated carbon (CBAC) for the adsorption of P204 and then evaluated their adsorption performance through batch and column experiments. The results found that, except for the main carbon matrix, CSAC and CBAC carried rich oxygen-containing functional groups and a small amount of inorganic substances. Both adsorbents had porous structures with pore diameters less than 4 nm. CSAC and CBAC showed good removal performance for P204 under low pH conditions, with removal efficiencies significantly higher than those of commonly used adsorption resins (XAD-4 and IRA900). The adsorption kinetics of P204 conformed to the pseudo-second-order kinetic model, and the adsorption isotherms conformed to the Langmuir model, indicating a monolayer chemical reaction mechanism. Both adsorbents exhibited strong anti-interference capabilities; their adsorption performance for P204 did not change greatly with the ambient temperature or the concentrations of common interfering ions. Column experiments demonstrated that CSAC could effectively fix dissolved P204 with a removal efficiency exceeding 90%. The fixed P204 could be desorbed with acetone. The findings provide an effective method for the recovery of P204 and the regeneration of spent activated carbon, which shows promise for practical applications in the future. Full article
(This article belongs to the Section Toxicity Reduction and Environmental Remediation)
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27 pages, 4623 KiB  
Article
Preparation and Application of Wetland-Plant-Derived Biochar for Tetracycline Antibiotic Adsorption in Water
by Qingyun Chen, Hao Tong, Xing Gao, Peng Li, Jiaqi Li, Haifeng Zhuang and Suqing Wu
Sustainability 2025, 17(14), 6625; https://doi.org/10.3390/su17146625 - 20 Jul 2025
Viewed by 329
Abstract
Every year, a large amount of antibiotics enter aquatic environments globally through discharging of pharmaceutical wastewater and domestic sewage, emissions from agriculture, and livestock, posing a severe threat to ecosystems and human health. Therefore, it is essential to develop efficient adsorption materials for [...] Read more.
Every year, a large amount of antibiotics enter aquatic environments globally through discharging of pharmaceutical wastewater and domestic sewage, emissions from agriculture, and livestock, posing a severe threat to ecosystems and human health. Therefore, it is essential to develop efficient adsorption materials for rapid removal of antibiotics in water. In this study, abundant and renewable wetland plants (lotus leaves, Arundo donax, and canna lilies) were utilized as raw materials to prepare biochar through slow pyrolysis combined with KOH chemical activation. The prepared biochar was employed to adsorb typical tetracycline (TC) antibiotics (TC-HCl, CTC-HCl, OTC-HCl) from water. The results showed that the optimum biochar (LBC-600 (1:3)) was prepared at a pyrolysis temperature of 600 °C with the mass ratio of KOH to lotus leaf of 1:3. The optimum pH for the adsorption of the three antibiotics were 5, 4, and 3, respectively. The highest adsorption rates reached 93.32%, 81.44%, and 83.76% for TC-HCl, CTC-HCl, and OTC-HCl with 0.6 g/L of biochar, respectively. At an initial antibiotic concentration of 80 mg·L−1, the maximum adsorption capacities achieved 40.17, 27.76, and 24.6 mg·g−1 for TC-HCl, CTC-HCl, and OTC-HCl, respectively. The adsorption process conformed to the pseudo-second-order kinetic and Langmuir isotherm models, indicating that it was a spontaneous endothermic process and primarily involved monolayer chemical adsorption. This study transformed wetland plant waste into adsorbent and applied it for antibiotic removal, providing a valuable resource utilization strategy and technical support for recycling wetland plant residues and antibiotic removal from water environments. Full article
(This article belongs to the Section Sustainable Water Management)
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17 pages, 2219 KiB  
Article
Oil Spill Recovery of Petroleum-Derived Fuels Using a Bio-Based Flexible Polyurethane Foam
by Fabrizio Olivito, Zul Ilham, Wan Abd Al Qadr Imad Wan-Mohtar, Goldie Oza, Antonio Procopio and Monica Nardi
Polymers 2025, 17(14), 1959; https://doi.org/10.3390/polym17141959 - 17 Jul 2025
Viewed by 359
Abstract
In this study, we tested a flexible polyurethane (PU) foam, synthesized from bio-based components, for the removal of petroleum-derived fuels from water samples. The PU was synthesized via the prepolymer method through the reaction of PEG 400 with L-lysine ethyl ester diisocyanate (L-LDI), [...] Read more.
In this study, we tested a flexible polyurethane (PU) foam, synthesized from bio-based components, for the removal of petroleum-derived fuels from water samples. The PU was synthesized via the prepolymer method through the reaction of PEG 400 with L-lysine ethyl ester diisocyanate (L-LDI), followed by chain extension with 2,5-bis(hydroxymethyl)furan (BHMF), a renewable platform molecule derived from carbohydrates. Freshwater and seawater samples were artificially contaminated with commercial diesel, gasoline, and kerosene. Batch adsorption experiments revealed that the total sorption capacity (S, g/g) of the PU was slightly higher for diesel in both water types, with values of 67 g/g in freshwater and 70 g/g in seawater. Sorption kinetic analysis indicated that the process follows a pseudo-second-order kinetic model, suggesting strong chemical interactions. Equilibrium data were fitted using Langmuir and Freundlich isotherm models, with the best fit achieved by the Langmuir model, supporting a monolayer adsorption mechanism on homogeneous surfaces. The PU foam can be regenerated up to 50 times by centrifugation, maintaining excellent performance. This study demonstrates a promising application of this sustainable and bio-based polyurethane foam for environmental remediation. Full article
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14 pages, 2683 KiB  
Article
Study on the Adsorption Behavior of a Cellulose Nanofibril/Tannic Acid/Polyvinyl Alcohol Aerogel for Cu(II), Cd(II), and Pb(II) Heavy Metal Ions
by Xuejin Zhang, Yulong Tian, Huanhuan Chen, Ying Liu, Shuaichuang Han, Minmin Chang, Jingshun Zhuang and Qingzhi Ma
Nanomaterials 2025, 15(14), 1063; https://doi.org/10.3390/nano15141063 - 9 Jul 2025
Viewed by 320
Abstract
Nanocellulose-based composite aerogels have the advantages of high porosity, biodegradability, and biocompatibility, with wide applications in many fields, such as adsorption, separation, energy storage, and heat insulation. In this study, a nanocellulose-based composite aerogel (NCA) was prepared using the one-pot method with cellulose [...] Read more.
Nanocellulose-based composite aerogels have the advantages of high porosity, biodegradability, and biocompatibility, with wide applications in many fields, such as adsorption, separation, energy storage, and heat insulation. In this study, a nanocellulose-based composite aerogel (NCA) was prepared using the one-pot method with cellulose nanofibrils (CNFs), tannic acid (TA), and polyvinyl alcohol (PVA) as raw materials. The adsorption behaviors of Pb2+, Cd2+, and Cu2+ were also studied. FT-IR analysis confirmed that TA successfully solidified on the nanocellulose, while SEM analysis revealed that the prepared NCA exhibited significantly higher porosity compared with the cellulose nanofibril-only aerogel. The results of the adsorption experiment demonstrated that the adsorption behavior of heavy metal ions using the prepared NCA followed pseudo-second-order kinetics. The adsorption isotherms fit well with the Langmuir adsorption model, indicating that the process of aerogels adsorbing heavy metal ions is that of monolayer adsorption. Under conditions of pH 6 and an initial heavy metal ion concentration of 100 mg/L, the maximum adsorption capacity calculated for the prepared NCA was up to 196.850 mg/g, 181.488 mg/g, and 151.515 mg/g for Cu2+, Cd2+, and Pb2+, respectively. Furthermore, the prepared NCA exhibited excellent reusability, with more than 90% efficiency retained after three cycles. NCAs have the potential to become an efficient material for absorbing heavy metal ions in water. Full article
(This article belongs to the Section Nanocomposite Materials)
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22 pages, 8657 KiB  
Article
Synergistic Enhancement of Rhodamine B Adsorption by Coffee Shell Biochar Through High-Temperature Pyrolysis and Water Washing
by Xurundong Kan, Yao Suo, Bingfei Shi, Yan Zheng, Zaiqiong Liu, Wenhui Ma, Xianghong Li and Jianqiang Zhang
Molecules 2025, 30(13), 2769; https://doi.org/10.3390/molecules30132769 - 27 Jun 2025
Viewed by 413
Abstract
Biochar-based adsorbents synthesized from agricultural wastes have emerged as economical and environmentally sustainable materials for water purification. In this study, coffee shell-derived biochars were synthesized via pyrolysis at 500 and 700 °C, with and without water washing, and comprehensively characterized to evaluate their [...] Read more.
Biochar-based adsorbents synthesized from agricultural wastes have emerged as economical and environmentally sustainable materials for water purification. In this study, coffee shell-derived biochars were synthesized via pyrolysis at 500 and 700 °C, with and without water washing, and comprehensively characterized to evaluate their potential for removing Rhodamine B (RhB) from aqueous solution. Structural and surface analyses indicated that a higher pyrolysis temperature enhanced pore development and aromaticity, whereas water washing effectively removed inorganic ash, thereby exposing additional active sites. Among all samples, water-washed biochar pyrolyzed at 700 °C (WCB700) exhibited the highest surface area (273.6 m2/g) and adsorption capacity (193.5 mg/g). The adsorption kinetics conformed to a pseudo-second-order model, indicating chemisorption, and the equilibrium data fit the Langmuir model, suggesting monolayer coverage. Mechanism analysis highlighted the roles of π–π stacking, hydrogen bonding, electrostatic interaction, and pore filling. Additionally, WCB700 retained more than 85% of its original capacity after five regeneration cycles, demonstrating excellent stability and reusability. This study presents an economical approach to valorizing coffee waste as well as provides mechanistic insights into optimizing biochar surface chemistry for enhanced dye removal. These findings support the application of engineered biochar in scalable and sustainable wastewater treatment technologies. Full article
(This article belongs to the Special Issue Emerging Multifunctional Materials for Next-Generation Energy Systems)
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24 pages, 6924 KiB  
Article
Application of Ulva intestinalis Linnaeus Biomass-Derived Biosorbents for Eco-Friendly Removal of Metal Contaminants from Water
by Alaa M. Younis and Ghada M. Almutairi
Processes 2025, 13(6), 1928; https://doi.org/10.3390/pr13061928 - 18 Jun 2025
Viewed by 505
Abstract
The study examines the biosorption potential of Ulva intestinalis (UI) and calcium oxide-modified Ulva intestinalis (CaO-UI) for the environmentally favorable removal of cadmium (Cd2+), nickel (Ni2+), and lead (Pb2+) from aqueous solutions. This research addresses the critical [...] Read more.
The study examines the biosorption potential of Ulva intestinalis (UI) and calcium oxide-modified Ulva intestinalis (CaO-UI) for the environmentally favorable removal of cadmium (Cd2+), nickel (Ni2+), and lead (Pb2+) from aqueous solutions. This research addresses the critical need for sustainable water treatment solutions by developing a green-synthesized biosorbent that combines renewable biomass with enhanced adsorption properties. The adsorption properties of the biomass were improved by preparing calcium oxide (CaO) using Ulva intestinalis extract by green synthesis. Langmuir, Freundlich, and Temkin isotherms were employed to model the results of adsorption experiments that were conducted under a variety of conditions, such as contact time, biosorbent dose, and initial metal ion concentration. Langmuir (R2 = 0.999) and Freundlich (R2 = 0.999) models both provided an exceptionally well-fitted model for the adsorption isotherms, suggesting a hybrid mechanism that integrates monolayer chemisorption at CaO-active sites and multilayer adsorption on the heterogeneous algal matrix. Key findings demonstrate that the maximum adsorption capacity (qm) of CaO-UI was substantially higher than that of UI, with values of 571.21 mg/g for Cd2+, 665.51 mg/g for Ni2+, and 577.87 mg/g for Pb2+, respectively, in comparison to 432.47 mg/g, 335.75 mg/g, and 446.65 mg/g for UI. The adsorption process was dominated by pseudo-second-order (PSO) chemisorption, as evidenced by kinetic studies (R2 = 0.949–0.993). CaO-UI exhibited substantially higher rate constants (k2 = 9.00–10.15 mg/mg·min) than raw UI (k2 = 4.72–5.71 mg/mg·min). The green synthesis of calcium oxide has resulted in an increase in surface area, porosity, and functional group density, which is responsible for the enhanced performance of CaO-UI. The adsorption efficacy of Pb2+ was the highest, followed by Cd2+ and Ni2+, which was indicative of the differences in metal ion affinity and hydration energy. These results underscore the potential of CaO-UI as a biosorbent that is both cost-effective and sustainable for the removal of heavy metals in wastewater treatment applications. Full article
(This article belongs to the Special Issue Natural Low-Cost Adsorbents in Water Purification Processes)
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20 pages, 23356 KiB  
Article
Counterion-Mediated Assembly of Fluorocarbon–Hydrocarbon Surfactant Mixtures at the Air–Liquid Interface: A Molecular Dynamics Study
by Xiaolong Quan, Tong Tong, Tao Li, Dawei Han, Baolong Cui, Jing Xiong, Zekai Cui, Hao Guo, Jinqing Jiao and Yuechang Wei
Molecules 2025, 30(12), 2592; https://doi.org/10.3390/molecules30122592 - 14 Jun 2025
Viewed by 503
Abstract
This study employs molecular dynamics simulations to investigate counterion effects (Li+, Na+, K+) on the interfacial aggregation of mixed short-chain fluorocarbon, Perfluorohexanoic acid (PFHXA), and Sodium dodecyl sulfate (SDS) surfactants. Motivated by the need for [...] Read more.
This study employs molecular dynamics simulations to investigate counterion effects (Li+, Na+, K+) on the interfacial aggregation of mixed short-chain fluorocarbon, Perfluorohexanoic acid (PFHXA), and Sodium dodecyl sulfate (SDS) surfactants. Motivated by the need for greener surfactant alternatives and a fundamental understanding of molecular interactions governing their behavior, we demonstrate that counterion hydration radius critically modulates system organization. K+ ions induce superior monolayer condensation and interfacial performance compared to Li+ and Na+ counterparts, as evidenced by threefold analysis: (1) RMSD/MSD-confirmed equilibrium attainment ensures data reliability; (2) 1D/2D density profiles and surface tension measurements reveal K+-enhanced packing density (lower solvent-accessible surface area versus Na+ and Li+ systems); (3) Electrostatic potential analysis identifies synergistic complementarity between SDS’s hydrophobic stabilization via dodecyl chain interactions and PFHXA’s charge uniformity, optimizing molecular-level charge screening. Radial distribution function analysis demonstrates K+’s stronger affinity for SDS head groups, with preferential sulfate coordination reducing surfactant-water hydration interactions. This behavior correlates with hydrogen-bond population reduction, attributed to SDS groups functioning as multidentate ligands—their tetrahedral oxygen arrangement facilitates cooperative hydrogen-bond networks, while counterion-specific charge screening competitively modulates bond formation. The resultant interfacial restructuring enables ordered molecular arrangements with lower system curvature than those observed in Li+ and Na+-containing systems. These findings elucidate counterion-mediated interfacial modulation mechanisms and establish K+ as an optimal candidate for enhancing PFHXA/SDS mixture performance through hydration-radius screening. The work provides molecular-level guidelines for designing eco-friendly surfactant systems with tailored interfacial properties. Full article
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21 pages, 3081 KiB  
Article
Efficient Removal of Micro-Sized Degradable PHBV Microplastics from Wastewater by a Functionalized Magnetic Nano Iron Oxides-Biochar Composite: Performance, Mechanisms, and Material Regeneration
by Huaguo Xia, Nini Duan, Beisi Song, Yuan Li, Hongbin Xu, Ying Geng and Xin Wang
Nanomaterials 2025, 15(12), 915; https://doi.org/10.3390/nano15120915 - 12 Jun 2025
Viewed by 596
Abstract
The co-occurrence of the synthesis of a functionalized magnetic nano iron oxides–biochar composite (MFe@BC) via impregnation–thermal pyrolysis and its use to remove micro-sized poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) microplastics from simulated wastewater was demonstrated in this study. The results showed that PHBV removal efficiency correlated [...] Read more.
The co-occurrence of the synthesis of a functionalized magnetic nano iron oxides–biochar composite (MFe@BC) via impregnation–thermal pyrolysis and its use to remove micro-sized poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) microplastics from simulated wastewater was demonstrated in this study. The results showed that PHBV removal efficiency correlated positively with MFe@BC dosage, achieving an adsorption capacity of 13.14 mg/g and a removal efficiency of 98.53% at an optimal dosage of 1.5 g/L. Adsorption kinetics fit a pseudo-second-order model (R2 = 0.9999), and the isotherm followed the Langmuir model (R2 = 0.8440), yielding a theoretical maximum capacity of 31.96 mg/g. Characterization indicated chemisorption-driven monolayer adsorption via surface complexation and hydrogen bonding. Magnetic nano-iron transfer from MFe@BC to the PHBV surface imparted magnetic properties to PHBV, enabling synergistic adsorption and magnetic separation. Removal efficiency remained above 95% across pH 4–9 and COD 0–500 mg/L. Regeneration experiments indicated that the MFe@BC showed robust reusability, maintaining >92% PHBV removal efficiency after four adsorption–regeneration cycles. The results of this study may provide a feasible pathway for PHBV microplastic removal from secondary effluent, indicating that MFe@BC prepared in this study can be used for the removal of PHBV microplastics in a wide range of water bodies. Full article
(This article belongs to the Special Issue Nanoscale Materials for Detection and Remediation of Water Pollutants)
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17 pages, 3101 KiB  
Article
Enhanced Removal of Hexavalent Chromium from Water by Nitrogen-Doped Wheat Straw Biochar Loaded with Nanoscale Zero-Valent Iron: Adsorption Characteristics and Mechanisms
by Hansheng Li, Ahmad Razali Ishak, Mohd Shukri Mohd Aris, Siti Norashikin Mohamad Shaifuddin, Su Ding and Tiantian Deng
Processes 2025, 13(6), 1714; https://doi.org/10.3390/pr13061714 - 30 May 2025
Viewed by 661
Abstract
The widespread industrial use of chromium has exacerbated water contamination issues globally. In this study, a nitrogen-doped wheat straw biochar loaded with nanoscale zero-valent iron composite (nZVI/N-KBC) was synthesized via a liquid-phase reduction method, and its adsorption properties for hexavalent chromium (Cr(VI)) in [...] Read more.
The widespread industrial use of chromium has exacerbated water contamination issues globally. In this study, a nitrogen-doped wheat straw biochar loaded with nanoscale zero-valent iron composite (nZVI/N-KBC) was synthesized via a liquid-phase reduction method, and its adsorption properties for hexavalent chromium (Cr(VI)) in aqueous solutions were systematically investigated. The material was characterized using SEM, XRD, Raman spectroscopy, FTIR, and XPS. Experimental results demonstrated that under optimal conditions (pH 2, 0.05 g adsorbent dosage, and 50 mg/L initial Cr(VI) concentration), the adsorption capacity reached 41.29 mg/g. Isothermal adsorption analysis revealed that the process followed the Langmuir model, indicating monolayer adsorption with a maximum capacity of 100.9 mg/g. Kinetic studies show that the adsorption conforms to the pseudo-second-order kinetic model, and thermodynamic and XPS analyses jointly prove that chemical adsorption is dominant. Thermodynamic analyses confirmed the endothermic and entropy-driven nature of adsorption. Mechanistic studies via XPS and FTIR revealed a dual mechanism: (1) partial adsorption of Cr(VI) onto the nZVI/N-KBC surface, and (2) predominant reduction in Cr(VI) to Cr(III) mediated by Fe0 and Fe2+. This study highlights the synergistic role of nitrogen doping and nZVI loading in enhancing Cr(VI) removal, offering a promising approach for remediating chromium-contaminated water. Full article
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19 pages, 6811 KiB  
Article
Application of Fe2O3 Catalytic Sludge Ceramics in the Control of Eutrophication in Water Bodies
by Xiangyu Song, Gang Meng, Jiacheng Cui, Haoyan Yuan, Siyi Luo and Zongliang Zuo
Catalysts 2025, 15(6), 540; https://doi.org/10.3390/catal15060540 - 29 May 2025
Viewed by 550
Abstract
The excessive input of nitrogen and phosphorus pollutants into surface water bodies poses a serious threat to the aquatic ecosystem. As an efficient porous adsorbent material, ceramsite shows remarkable potential in the field of simultaneous nitrogen and phosphorus removal. In this study, Fe [...] Read more.
The excessive input of nitrogen and phosphorus pollutants into surface water bodies poses a serious threat to the aquatic ecosystem. As an efficient porous adsorbent material, ceramsite shows remarkable potential in the field of simultaneous nitrogen and phosphorus removal. In this study, Fe2O3 catalyzed the decomposition of K2CO3 to generate CO and CO2 gases, leading to the formation of a large number of pore structures in the composite ceramsite. Subsequently, adsorption experiments were conducted on the obtained ceramsite. The regulatory mechanisms of the ceramsite dosage and solution pH on its adsorption performance were revealed. The experiments show that as the ceramsite dosage increased from 2.1 g/L to 9.6 g/L, the adsorption capacities of ammonia–nitrogen and phosphorus decreased from 0.4521 mg/g and 0.4280 mg/g to 0.1430 mg/g and 0.1819 mg/g, respectively, while the removal rates increased to 68.66% and 58.22%, respectively. This indicates that the competition between the utilization efficiency of adsorption sites and the mass-transfer limitation between particles dominates this process. An analysis of the pH effect reveals that the adsorption of ammonia–nitrogen reached a peak at pH = 10 (adsorption capacity of 0.4429 mg/g and removal rate of 81.58%), while the optimal adsorption of phosphorus occurred at pH = 7 (adsorption capacity of 0.3446 mg/g and removal rate of 86.40%). This phenomenon is closely related to the interaction between the existing forms of pollutants and the surface charge. Kinetic and thermodynamic studies show that the pseudo-second-order kinetic model (R2 > 0.99) and the Langmuir isothermal model can accurately describe the adsorption behavior of the ceramsite for ammonia–nitrogen and phosphorus, confirming that the adsorption is dominated by a monolayer chemical adsorption mechanism. This study explores the dosage–efficiency relationship and pH response mechanism of Fe2O3-catalyzed porous ceramsite for nitrogen and phosphorus adsorption, revealing the interface reaction pathway dominated by Fe2O3 catalysis and chemical adsorption. It provides theoretical support for the construction of porous ceramsite and the development of an efficient technology system for the synergistic removal of nitrogen and phosphorus. Full article
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16 pages, 2741 KiB  
Article
Preparation of Highly Antibacterial MXene Nanofiltration Membranes and Investigation of Their Separation Performance
by Na Meng, Jinxin Liu, Jialing Mi, Xuan Chen, Rong Rong, Junjie Hang and Zihan Jiang
Polymers 2025, 17(11), 1493; https://doi.org/10.3390/polym17111493 - 27 May 2025
Cited by 1 | Viewed by 469
Abstract
In this study, polyethersulfone (PES)/sulfonated polyethersulfone (SPES) composite nanofiltration membranes doped with different contents of monolayer titanium carbide nanosheets (Ti3C2TX) were prepared by the nonsolvent induced phase inversion (NIPS) method. The effects of Ti3C2 [...] Read more.
In this study, polyethersulfone (PES)/sulfonated polyethersulfone (SPES) composite nanofiltration membranes doped with different contents of monolayer titanium carbide nanosheets (Ti3C2TX) were prepared by the nonsolvent induced phase inversion (NIPS) method. The effects of Ti3C2TX on membrane structure, separation performance and antibacterial activity were investigated systematically. The results demonstrated that the viscosity of the casting solution increased significantly with the increasing content of Ti3C2TX. In addition, the pore size of the membrane surface first decreased and then increased; porosity and hydrophilicity were optimized synchronously; and the density of negative charges on the surface increased. The M2 membrane showed a rejection rate of more than 90% for Metanil yellow (MY) and methylene blue (MEB). The order of salt ion rejection rates was magnesium sulfate (MgSO4) > sodium sulfate (Na2SO4) > sodium chloride (NaCl), and water flux reached the peak (18.5 L/m2·h·bar). The antibacterial activity of the M2 membrane was significantly enhanced, and its antibacterial rate against Bacillus subtilis increased from 15% (M0) to 58%. This phenomenon was attributed to the synergistic mechanism of the Ti3C2TX physical capture effect, reactive oxygen species (ROS) generation and sharp edge damage to bacterial cell membranes. This study provides theoretical support and a technical path for the development of MXene composite membranes with high separation efficiency and excellent antibacterial properties. Full article
(This article belongs to the Special Issue Polymer-Based Membranes: Innovation in Separation Technology)
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17 pages, 3217 KiB  
Article
Robust Adsorption of Pb(II) and Cd(II) by GLDA-Intercalated ZnAl-LDH: Structural Engineering, Mechanistic Insights, and Environmental Applications
by Kai Zheng, Zhengkai Guang, Zihan Wang, Yangu Liu, Xiaoling Cheng and Yuan Liu
Coatings 2025, 15(5), 613; https://doi.org/10.3390/coatings15050613 - 21 May 2025
Viewed by 628
Abstract
The rapid pace of industrialization has led to widespread heavy metal contamination in water and soil, highlighting the need for efficient remediation strategies. Among various approaches, adsorption has proven to be an effective method for treating contaminated environments. Layered double hydroxide (LDH) is [...] Read more.
The rapid pace of industrialization has led to widespread heavy metal contamination in water and soil, highlighting the need for efficient remediation strategies. Among various approaches, adsorption has proven to be an effective method for treating contaminated environments. Layered double hydroxide (LDH) is frequently used in such applications. However, its adsorption efficiency remains limited. In this study, glutamic acid diacetate tetrasodium salt (GLDA) was incorporated into ZnAl LDH via a straightforward co-precipitation and ion exchange method, yielding a modified material, GLDA-LDH, which was subsequently applied for the adsorption of Pb(II) and Cd(II). Adsorption behavior was investigated through kinetic and isothermal models, with results indicating that the process followed pseudo-second-order kinetics and fit well with the Langmuir isotherm, suggesting chemisorption onto monolayer surface. The maximum adsorption capacities reached 219.2 mg/g for Pb(II) and 121.9 mg/g for Cd(II). Furthermore, GLDA-LDH exhibited a strong retention capability for metal ions with minimal desorption and remained effective in the presence of hard water and contaminated soils. XPS analysis revealed distinct interaction mechanisms; surface oxygen and carboxyl groups played a key role in Pb(II) adsorption, whereas nitrogen coordination was involved in Cd(II) uptake. These results point to the potential of GLDA-LDH as a reliable material for addressing heavy metal pollution and provide insights into the design of enhanced LDH-based adsorbents. Full article
(This article belongs to the Section Environmental Aspects in Colloid and Interface Science)
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31 pages, 6141 KiB  
Article
Fe3O4/SiO2 Nanocomposite Derived from Coal Fly Ash and Acid Mine Drainage for the Adsorptive Removal of Diclofenac in Wastewater
by Dance Mabu, Ngwako Joseas Waleng, Tshimangadzo S. Munonde, Azile Nqombolo and Philiswa Nosizo Nomngongo
Recycling 2025, 10(3), 99; https://doi.org/10.3390/recycling10030099 - 16 May 2025
Viewed by 1455
Abstract
The ubiquity of diclofenac (DCF) in the environment has raised significant concerns. Diclofenac is a non-steroidal anti-inflammatory drug that has been found in various environmental matrices at minimum concentrations that are harmful to aquatic and terrestrial organisms. Traditional wastewater treatment plants (WWTPs) are [...] Read more.
The ubiquity of diclofenac (DCF) in the environment has raised significant concerns. Diclofenac is a non-steroidal anti-inflammatory drug that has been found in various environmental matrices at minimum concentrations that are harmful to aquatic and terrestrial organisms. Traditional wastewater treatment plants (WWTPs) are not fully equipped to remove a range of pharmaceuticals, and that explains the continued ubiquity of DCF in surface waters. In this study, an Fe3O4/SiO2 nanocomposite prepared from acid mine drainage and coal fly ash was applied for the removal of DCF from wastewater. Major functional groups (Si–O–Si and Fe–O) were discovered from FTIR. TEM revealed uniform SiO2 nanoparticle rod-like structures with embedded dark spherical nanoparticles. SEM-EDS analysis discovered a sponge-like structure fused with Fe3O4 nanoparticles that had significant Si, O, and Fe content. XRD demonstrated the crystalline nature of the nanocomposite. The surface properties of the nanocomposite were evaluated using BET and were 67.8 m2/g, 0.39 cm3/g, and 23.2 nm for surface area, pore volume, and pore size, respectively. Parameters that were suspected to be affecting the removal process were evaluated, including pH, nanocomposite dosage, and sample volume. The detection of DCF was conducted on high-performance liquid chromatography with diode-array detection (HPLC-DAD). Under optimum conditions, the adsorption process was monolayer, and physisorption was described using the Langmuir and Dubinin-Radushkevich (D-R) isotherm models. The kinetic data best fitted the pseudo-first order kinetic model, indicating a physisorption adsorption process. The thermodynamic experimental data confirmed that the adsorption process was spontaneous. The results obtained from real water samples showed 95.28% and 97.44% removal efficiencies from influent and effluent: 94.83% and 88.61% from raw sewage and final sewage, respectively. Overall, this work demonstrated that an Fe3O4/SiO2 nanocomposite could be successfully prepared from coal fly ash and acid mine drainage and could be used to remove DCF in wastewater. Full article
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