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Search Results (269)

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Keywords = liquid adsorption isotherms

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25 pages, 2545 KiB  
Article
Kinetic, Isotherm, and Thermodynamic Modeling of Methylene Blue Adsorption Using Natural Rice Husk: A Sustainable Approach
by Yu-Ting Huang and Ming-Cheng Shih
Separations 2025, 12(8), 189; https://doi.org/10.3390/separations12080189 - 22 Jul 2025
Viewed by 254
Abstract
The discharge of synthetic dyes in industrial wastewaters poses a serious environmental threat as they are difficult to degrade naturally and are harmful to aquatic organisms. This study aimed to evaluate the feasibility of using clean untreated rice husk (CRH) as a sustainable [...] Read more.
The discharge of synthetic dyes in industrial wastewaters poses a serious environmental threat as they are difficult to degrade naturally and are harmful to aquatic organisms. This study aimed to evaluate the feasibility of using clean untreated rice husk (CRH) as a sustainable and low-cost adsorbent for the removal of methylene blue (MB) from synthetic wastewater. This approach effectively avoids the energy-intensive grinding process by directly using whole unprocessed rice husk, highlighting its potential as a sustainable and cost-effective alternative to activated carbon. A series of batch adsorption experiments were conducted to evaluate the effects of key operating parameters such as initial dye concentration, contact time, pH, ionic strength, and temperature on the adsorption performance. Adsorption kinetics, isotherm models, and thermodynamic analysis were applied to elucidate the adsorption mechanism and behavior. The results showed that the maximum adsorption capacity of CRH for MB was 5.72 mg/g. The adsorption capacity was stable and efficient between pH 4 and 10, and reached the highest value at pH 12. The presence of sodium ions (Na+) and calcium ions (Ca2+) inhibited the adsorption efficiency, with calcium ions having a more significant effect. Kinetic analysis confirmed that the adsorption process mainly followed a pseudo-second-order model, suggesting the involvement of a chemisorption mechanism; notably, in the presence of ions, the Elovich model provided better predictions of the data. Thermodynamic evaluation showed that the adsorption was endothermic (ΔH° > 0) and spontaneous (ΔG° < 0), accompanied by an increase in the disorder of the solid–liquid interface (ΔS° > 0). The calculated activation energy (Ea) was 17.42 kJ/mol, further supporting the involvement of chemisorption. The equilibrium adsorption data were well matched to the Langmuir model at high concentrations (monolayer adsorption), while they were accurately described by the Freundlich model at lower concentrations (surface heterogeneity). The dimensionless separation factor (RL) confirmed that the adsorption process was favorable at all initial MB concentrations. The results of this study provide insights into the application of agricultural waste in environmental remediation and highlight the potential of untreated whole rice husk as a sustainable and economically viable alternative to activated carbon, which can help promote resource recovery and pollution control. Full article
(This article belongs to the Section Environmental Separations)
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22 pages, 3937 KiB  
Article
Selective Ammonium Recovery from Livestock and Organic Solid Waste Digestates Using Zeolite Tuff: Efficiency and Farm-Scale Prospects
by Matteo Alberghini, Giacomo Ferretti, Giulio Galamini, Cristina Botezatu and Barbara Faccini
Recycling 2025, 10(4), 137; https://doi.org/10.3390/recycling10040137 - 8 Jul 2025
Viewed by 284
Abstract
Implementing efficient strategies for the circular recovery and reuse of nutrients from wastewaters is mandatory to meet the Green Deal objectives and Sustainable Development Goals. In this context we investigated the use of zeolitic tuff (containing chabazite and phillipsite) in the selective recovery [...] Read more.
Implementing efficient strategies for the circular recovery and reuse of nutrients from wastewaters is mandatory to meet the Green Deal objectives and Sustainable Development Goals. In this context we investigated the use of zeolitic tuff (containing chabazite and phillipsite) in the selective recovery and reuse of N from various anaerobic liquid digestates in view of their implementation in farm-scale treatment plants. We tested the method on three livestock digestates and two municipal organic solid waste digestates. Adsorption isotherms and kinetics were assessed on each digestate, and a large set of parameters, including (i) contact time, (ii) initial NH4+ concentration, (iii) presence of competing ions, (iv) total solids content, and (vi) separation methods (microfiltration and clarification), were considered in the experimental design. Our results showed that the adsorption mechanism can be explained by the Freundlich model (R2 up to 0.97), indicating a multilayer and heterogeneous adsorption, while the kinetic of adsorption can be explained by the pseudo-second-order model, indicating chemical adsorption and ion exchange. The efficiency in the removal of NH4+ was indirectly related to the K+ and total solids content of the digestate. Maximum NH4+ removal exceeded 90% in MSW-derived digestates and 80% within 60 min in livestock-derived digestates at a 5% solid/liquid ratio. Thermodynamic parameters confirmed favorable and spontaneous adsorption (ΔG up to −7 kJ⋅mol−1). Farm-scale projections estimate a nitrogen recovery potential of 1.2 to 16 kg N⋅day−1, depending on digestate type and process conditions. These findings support the application of natural zeolitic tuffs as a low-cost, chemical-free solution for ammonium recovery, contributing to sustainable agriculture and circular economy objectives. Full article
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28 pages, 9583 KiB  
Article
Eco-Engineered Biopolymer–Clay Composite for Phosphate IonRemoval: Synergistic Insights from Statistical and AI Modeling
by Rachid Aziam, Daniela Simina Stefan, Safa Nouaa, Mohamed Chiban and Mircea Stefan
Polymers 2025, 17(13), 1805; https://doi.org/10.3390/polym17131805 - 28 Jun 2025
Viewed by 359
Abstract
This research aims to synthesize a novel hydrogel bio-composite based on natural clay, sodium alginate (Na-AL), and iota-carrageenan as adsorbents to remove phosphate ions from aqueous solutions. The adsorbents were characterized by a variety of techniques, such as Fourier-transform infrared (FTIR) spectroscopy, scanning [...] Read more.
This research aims to synthesize a novel hydrogel bio-composite based on natural clay, sodium alginate (Na-AL), and iota-carrageenan as adsorbents to remove phosphate ions from aqueous solutions. The adsorbents were characterized by a variety of techniques, such as Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy coupled with energy dispersive X-rays (SEM-EDX), and the determination of point zero charge (PZC). This research investigated how the adsorption process is influenced by parameters such as adsorbent dose, contact time, solution pH, and temperature. In this study, we used four isotherms and four kinetic models to investigate phosphate ion removal on the prepared bio-composite. The results showed that the second-order kinetic (PSO) model is the best model for describing the adsorption process. The findings demonstrate that the R2 values are highly significant in both the Langmuir and Freundlich models (very close to 1). This suggests that Langmuir and Freundlich models, with a diversity of adsorption sites, promote the adsorption of phosphate ions. The maximum adsorbed amounts of phosphate ions by the bio-composite used were 140.84 mg/g for H2PO4 ions and 105.26 mg/g for HPO42− ions from the batch system. The positive ∆H° confirms the endothermic and physical nature of adsorption, in agreement with experimental results. Negative ∆G° values indicate spontaneity, while the positive ∆S° reflects increased disorder at the solid–liquid interface during phosphate uptake. The main parameters, including adsorbent dosage (mg), contact time (min), and initial concentration (mg/L), were tuned using the Box–Behnken design of the response surface methodology (BBD-RSM) to achieve the optimum conditions. The reliability of the constructed models is demonstrated by their high correlation coefficients (R2). An R2 value of 0.9714 suggests that the model explains 97.14% of the variability in adsorption efficiency (%), which reflects its strong predictive capability and reliability. Finally, the adsorption behavior of phosphate ions on the prepared bio-composite beads was analyzed using an artificial neural network (ANN) to predict the process efficiency. The ANN model accurately predicted the adsorption of phosphate ions onto the bio-composite, with a strong correlation (R2 = 0.974) between the predicted and experimental results. Full article
(This article belongs to the Special Issue Advances in Polymer Composites II)
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20 pages, 3805 KiB  
Article
Structure–Activity Relationship of Ionic Liquids for Acid Corrosion Inhibition
by Aymane Omari Alaoui, Mouslim Messali, Walid Elfalleh, Belkheir Hammouti, Abderrahim Titi and Fadoua El-Hajjaji
Int. J. Mol. Sci. 2025, 26(12), 5750; https://doi.org/10.3390/ijms26125750 - 16 Jun 2025
Viewed by 473
Abstract
Novel derivatives of imidazolium-based ionic liquids with varying alkyl chains, IL-1, IL-2, and IL-3, were evaluated as corrosion inhibitors for mild steel in 1 M HCl solution. The experimental investigations used Electrochemical Impedance Spectroscopy (EIS) and potentiodynamic polarization (PDP) techniques. The results demonstrated [...] Read more.
Novel derivatives of imidazolium-based ionic liquids with varying alkyl chains, IL-1, IL-2, and IL-3, were evaluated as corrosion inhibitors for mild steel in 1 M HCl solution. The experimental investigations used Electrochemical Impedance Spectroscopy (EIS) and potentiodynamic polarization (PDP) techniques. The results demonstrated exceptional corrosion inhibition efficiency (>90%), as classified by electrochemical analyses, which identified these corrosion inhibitor compounds as mixed-type. The ionic liquids’ adsorption complied with the Langmuir adsorption isotherm. The characterization of the surface via SEM and EDX confirmed the development of a protective adsorbed inhibitor layer on the steel substrate. Furthermore, the theoretical DFT method (at B3LYP/6-311G (d, p)) was conducted to describe the electronic properties and reactivity of the molecules. The Monte Carlo simulation on the surface of Fe(1 1 0) was assessed to provide in-depth understanding of the adsorption mechanisms and interactions responsible for the corrosion inhibition between the molecules and the surface of the mild steel. Full article
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21 pages, 5124 KiB  
Article
Full-Scale Pore Structure and Gas Adsorption Characteristics of the Medium-Rank Coals from Qinshui Basin, North China
by Yingchun Hu, Shan He, Feng Qiu, Yidong Cai, Haipeng Wei and Bin Li
Processes 2025, 13(6), 1862; https://doi.org/10.3390/pr13061862 - 12 Jun 2025
Viewed by 507
Abstract
To elucidate the gas adsorption characteristics of medium-rank coal, this study collected samples from fresh mining faces in the Qinshui Basin. A series of experiments were conducted, including low-temperature carbon dioxide adsorption, low-temperature liquid nitrogen adsorption, mercury intrusion, and methane isothermal adsorption experiments, [...] Read more.
To elucidate the gas adsorption characteristics of medium-rank coal, this study collected samples from fresh mining faces in the Qinshui Basin. A series of experiments were conducted, including low-temperature carbon dioxide adsorption, low-temperature liquid nitrogen adsorption, mercury intrusion, and methane isothermal adsorption experiments, which clarify the pore structure characteristics of medium-rank coals, reveal the gas adsorption behavior in medium-rank coal, and identify the control mechanism. The results demonstrate that the modified Dubinin–Radushkevich (D-R) isothermal adsorption model accurately describes the gas adsorption in medium-rank coal, with fitting errors remaining below 1%. Comprehensive pore structure analysis reveals that the coal pore volume consists primarily of absorption pores (<2 nm), transitional pores (10–100 nm), and seepage pores (>100 nm), while the specific surface area is predominantly contributed by absorption pores (<2 nm). At low pressures, gas molecules form monolayer adsorption on absorption pore (<2 nm) and adsorption pore (2–10 nm) surfaces. With increasing pressure, multilayer adsorption dominates. As pore filling approaches the maximum capacity, the adsorption rate decreases progressively until reaching an equilibrium, at which point the adsorption capacity attains its saturation limit. The adsorption data of the gas in medium-rank coal can be explained by the improved D-R isothermal adsorption model. The priority of gas filling in pores is different, and the absorption pore is normally better than the adsorption pore. The results provide a new idea and understanding for the further study of the coalbed gas adsorption mechanism. Full article
(This article belongs to the Section Energy Systems)
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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 650
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, 1751 KiB  
Article
Purification of Flavonoids from an Aqueous Cocoa (Theobroma cocoa L.) Extract Using Macroporous Adsorption Resins
by Nicole Beeler, Tilo Hühn, Sascha Rohn and Renato Colombi
Molecules 2025, 30(11), 2336; https://doi.org/10.3390/molecules30112336 - 27 May 2025
Viewed by 451
Abstract
Cocoa is a rich source of health-promoting polyphenols such as flavanols. These compounds can be separated from other matrix constituents using various adsorbents or resins. Seven different macroporous resins (Amberlite® XAD-2, XAD-4, XAD-7, XAD-7HP, XAD-16, SepabeadsTM SP207, and Diaion® HP2-MG) [...] Read more.
Cocoa is a rich source of health-promoting polyphenols such as flavanols. These compounds can be separated from other matrix constituents using various adsorbents or resins. Seven different macroporous resins (Amberlite® XAD-2, XAD-4, XAD-7, XAD-7HP, XAD-16, SepabeadsTM SP207, and Diaion® HP2-MG) were evaluated for their adsorption and desorption properties for the enrichment of flavonoids from an aqueous cocoa (Theobroma cacao L.) extract. The influence of adsorption and desorption temperatures and the concentration of the desorption solvent (a hydroalcoholic solution) were investigated by static adsorption and desorption methods. The results of the resin comparison showed that the adsorbent XAD-7HP had the best adsorption characteristics, with an adsorption capacity of 39.8 mg ECE/g. XAD-7HP was found to be the most suitable adsorbent, and 70% ethanol was the best desorbing solvent, based on static experiments. In addition, the optimal conditions for the adsorption of flavonoids were obtained at a temperature of 30 °C, where equilibrium was reached after 80 min. The static adsorption process was well-described by a pseudo-second-order kinetics model, while the adsorption isotherm data were fitted well by the Freundlich isotherm model. Further dynamic adsorption and desorption characteristics were evaluated on a packed glass column, and it was shown that XAD-7HP could enrich the flavanol content by 5.03-fold, with a dry matter content of 456.05 mg/mL (as estimated by the degree of DP1–DP7 procyanidin polymers using ultra-pressure liquid chromatography). Full article
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15 pages, 1574 KiB  
Article
Simulation and Parametric Evaluation of Pb (II) Adsorption in a Biomass-Packed Bed Using Isothermal Freundlich–LDF and Langmuir II–LDF Models
by Angel Villabona-Ortíz, Oscar E. Coronado-Hernández and Candelaria Tejada-Tovar
Processes 2025, 13(6), 1655; https://doi.org/10.3390/pr13061655 - 24 May 2025
Viewed by 535
Abstract
The objective of this study was to model an adsorption column bed with biomass residues using computational software to remove Pb (II) at the industrial level and analyse the effects of parametric variation. For this purpose, several simulations of the adsorption column were [...] Read more.
The objective of this study was to model an adsorption column bed with biomass residues using computational software to remove Pb (II) at the industrial level and analyse the effects of parametric variation. For this purpose, several simulations of the adsorption column were performed using Aspen Adsorption software, evaluating the effects of varied height, inlet flow rate, and initial concentration on the adsorption process performance. The Langmuir II and Freundlich models are established as isotherm models, and the linear driving force (LDF) model is established as the kinetic model. The findings showed that Freundlich–LDF obtained efficiencies of up to 99.9% and Langmuir II–LDF efficiencies of up to 99.7%. The optimal simulation conditions were a column height of 4 m, an initial Pb (II) concentration of 3000 mg/L, and an inlet flow rate of 250 m3/d. This study presents a novel engineering approach to predict the potential performance of columns packed with organic waste-derived biomasses in multi-scale Pb (II) removal using computer-aided engineering tools. Full article
(This article belongs to the Special Issue Modeling and Optimization for Multi-scale Integration)
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14 pages, 1557 KiB  
Article
Lignin Extracted from Green Coconut Waste Impregnated with Sodium Octanoate for Removal of Cu2+ in Aqueous Solution
by Jéssyca E. S. Pereira, Eduardo L. Barros Neto, Lindemberg J. N. Duarte, Ruan L. S. Ferreira, Ricardo P. F. Melo and Paula F. P. Nascimento
Processes 2025, 13(5), 1590; https://doi.org/10.3390/pr13051590 - 20 May 2025
Viewed by 638
Abstract
Investigating viable processes for the use of lignocellulosic biomass in clean fuels and high-value-added chemical products is essential for sustainable development. Large amounts of lignin are available every year as by-products of the paper and biorefinery industries, causing a series of problems, particularly [...] Read more.
Investigating viable processes for the use of lignocellulosic biomass in clean fuels and high-value-added chemical products is essential for sustainable development. Large amounts of lignin are available every year as by-products of the paper and biorefinery industries, causing a series of problems, particularly environmental ones. Its structure and composition make lignin compatible with the concept of sustainability, since it can be used to produce new chemical products with high added value. As such, this study aims to extract lignin from green coconut fiber (LIG), with the subsequent impregnation of a sodium-octanoate-based surfactant (LIG-SUR), and determine its applicability as an adsorbent for removing copper ions from synthetic waste. To this end, the green coconut fiber lignocellulosic biomass was initially subjected to alkaline pre-treatment with 2% (w/v) sodium hydroxide in an autoclave. Next, the surface of the lignin was modified by impregnating it with sodium octanoate, synthesized from the reaction of octanoic acid and NaOH. The physical and chemical traits of the lignin were studied before and after surfactant impregnation, as well as after copper ion adsorption. The lignin was analyzed by X-ray fluorescence (XRF), Fourier transform infrared (FTIR) and scanning electron microscopy (SEM). The adsorption tests were carried out using lignin pre-treated with surfactant in a batch system, where the effects of pH and adsorbent concentration were investigated. XRF and SEM analyses confirmed surfactant impregnation, with Na2O partially replaced by CuO after Cu2+ adsorption. FTIR analysis revealed shifts in O–H, C–H, C=O, and C=C bands, indicating electrostatic interactions with lignin. Adsorption kinetics followed the pseudo-second-order model, suggesting chemisorption, with equilibrium reached in approximately 10 and 60 min for LIG-SUR and LIG, respectively. The Langmuir model best described the isotherm data, indicating monolayer adsorption. LIG-SUR removed 91.57% of Cu2+ and reached a maximum capacity of 30.7 mg·g−1 at 25 °C and a pH of 6. The results of this research showed that pre-treatment with NaOH, followed by impregnation with surfactant, significantly increased the adsorption capacity of copper ions in solution. This technique is a viable and sustainable alternative to the traditional adsorbents used to treat liquid waste. In addition, by using green coconut fiber lignin more efficiently, the research contributes to adding value to this material and strengthening practices in line with the circular economy and environmental preservation. Full article
(This article belongs to the Special Issue Emerging Technologies in Solid Waste Recycling and Reuse)
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21 pages, 1985 KiB  
Article
Antimony- and Bismuth-Based Ionic Liquids as Efficient Adsorbents for the Removal of Dyes
by Anham Zafar, Nouman Rafique, Saadia Batool, Muhammad Saleem, Aiyeshah Alhodaib and Amir Waseem
Catalysts 2025, 15(5), 492; https://doi.org/10.3390/catal15050492 - 19 May 2025
Viewed by 658
Abstract
A series of ionic liquids consisting of anilinium cations with varying alkyl chains and metallic (Sb and Bi) halides as anions have been synthesized and thoroughly characterized by using multinuclear (1H and 13C) NMR, FT-IR, Raman and XPS techniques. They [...] Read more.
A series of ionic liquids consisting of anilinium cations with varying alkyl chains and metallic (Sb and Bi) halides as anions have been synthesized and thoroughly characterized by using multinuclear (1H and 13C) NMR, FT-IR, Raman and XPS techniques. They have been exploited as adsorbents for the dye’s removal, such as malachite green, rhodamine B and Sudan II, from the aqueous solution. Various parameters like the effect of stirring rate, pH, reaction time, adsorbent amount and initial dye concentration have been optimized. Both antimony- and bismuth-based ionic liquids exhibit high adsorption efficiencies and have comparable performance for each dye. Kinetic data have been analyzed by applying kinetic models, and the best-fitted model was found to be pseudo-second order with an R2 value greater than 0.98. Adsorption capacity has been determined by analyzing the sorption data using the Langmuir and Freundlich equations, and the Langmuir isotherm model has been found to be the best fitting. The maximum adsorption capacities (qmax) derived from the Langmuir isotherm for malachite green, Sudan II and rhodamine B by M-Sb ILs were 217.36, 162.10 and 62.94 mg·g−1, whereas by M-Bi ILs, the adsorption capacities were slightly higher, at 230.18, 170.00 and 64.21 mg·g−1, respectively. Kinetic studies indicated pseudo-second-order behavior (R2 > 0.98), while thermodynamic analysis demonstrated an endothermic adsorption, and a spontaneous reaction was carried out by a physisorption process. These findings accentuate the potential of Sb- and Bi-based ionic liquids as efficient and reusable adsorbents for removing dyes from wastewater. Full article
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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 1446
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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32 pages, 16345 KiB  
Article
Surface Ion-Imprinted Polypropylene Fibers for Selective and Rapid Adsorption of Borate Ions: Preparation, Characterization, and Performance Study
by Hui Jiang, Xinchi Zong, Zhengwei Luo, Wenhua Geng and Jianliang Zhu
Polymers 2025, 17(10), 1368; https://doi.org/10.3390/polym17101368 - 16 May 2025
Viewed by 324
Abstract
This study presents a novel ion-imprinted fiber material, I-(PP-g-GMA-NMDG), designed for the rapid and selective adsorption of borate ions. Leveraging low-temperature plasma graft polymerization, polypropylene (PP) melt-blown fibers were functionalized with glycidyl methacrylate (GMA) and N-methyl-D-glucamine (NMDG) to introduce tailored [...] Read more.
This study presents a novel ion-imprinted fiber material, I-(PP-g-GMA-NMDG), designed for the rapid and selective adsorption of borate ions. Leveraging low-temperature plasma graft polymerization, polypropylene (PP) melt-blown fibers were functionalized with glycidyl methacrylate (GMA) and N-methyl-D-glucamine (NMDG) to introduce tailored recognition sites. Systematic optimization of plasma parameters (100 W discharge power, O2 atmosphere) and liquid-phase grafting conditions (28.5% GMA, 85 °C, 2.5 h) achieved a grafting rate of 203.26%. The imprinted fibers exhibited exceptional adsorption performance, with a maximum capacity of 35.85 mg/g at pH 9, reaching 90% saturation within 60 min. Adsorption kinetics adhered to a pseudo-second-order model, while the Freundlich isotherm indicated multilayer adsorption. Competitive ion experiments demonstrated high selectivity for B(OH)4 over anions (SO42− and Cl) and cations (Na+, K+, Ca2+, and Mg2+), which was attributed to the precise spatial and charge complementarity of the imprinted cavities. Characterization via FT-IR, XRD, and SEM confirmed successful synthesis and structural stability. The material retained 78.1% adsorption efficiency after five regeneration cycles, showcasing its practicality for boron recovery from wastewater. This work advances boron-selective adsorption technology by combining plasma modification with ion imprinting, offering a sustainable solution for industrial and environmental applications. Full article
(This article belongs to the Section Polymer Chemistry)
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18 pages, 4815 KiB  
Article
Functionalization of Rice Husk for High Selective Extraction of Germanium
by Qunshan Wei, Wei Zeng, Siyi Ding, Zhemin Shen, Xinshan Song, Yuhui Wang, Charles Nzila and Christopher W. K. Chow
Processes 2025, 13(5), 1367; https://doi.org/10.3390/pr13051367 - 29 Apr 2025
Viewed by 551
Abstract
It is of strategic significance to extract germanium (Ge) in an ecological way for sustainable development. Adsorbents that already adsorb Ge have disadvantages such as poor selectivity and low adsorption capacity. In this study, a novel adsorbent material based on rice husk functionalized [...] Read more.
It is of strategic significance to extract germanium (Ge) in an ecological way for sustainable development. Adsorbents that already adsorb Ge have disadvantages such as poor selectivity and low adsorption capacity. In this study, a novel adsorbent material based on rice husk functionalized with tannic acid was developed for the efficient extraction of Ge from simulated coal fly ash leachate. The adsorption capacity of tannic acid-functionalized rice husk (TA-EPI-ORH) for Ge was 19.9 times higher than that of untreated rice husk, demonstrating significantly improved performance. The results showed that the adsorption process of Ge by TA-EPI-ORH is consistent with pseudo-second-order kinetic and Freundlich isotherm model. TA-EPI-ORH had excellent selective adsorption properties, with adsorption of 1.40 mg L−1 Ge exceeding 95% and solid-liquid partition coefficients of 4380 mL g−1, even in the presence of nine impurity metal ions (average concentration: 479.08 mg L−1). When compared with the two main coexistence ions—aluminum (Al) and calcium (Ca)—both of which have the relatively highest concentrations (Al: 1594.20 mg L−1, Ca: 1740.13 mg L−1), the separation factors for Ge still maintain relatively high level with SF(Ge/Al) = 42.57 and SF(Ge/Ca) = 39.93. Compared to existing studies, TA-EPI-ORH exhibits superior selective adsorption performance even with the presence of more interfering ions. After elution of the adsorbed Ge from TA-EPI-ORH, the extraction rate of Ge with low initial concentration (1.40 mg L−1) reached 85.17%, while the extraction rates of Al and Ca were only 1.02% and 1.18%, respectively. Further research revealed that the catechol groups on the surface of TA-EPI-ORH formed stable complexes with Ge, whereas the complexes with coexisting ions (e.g., Ca and Al) were unstable, thereby ensuring high selectivity for Ge. This green chemistry-based functionalization of rice husk not only enables high-value utilization of agricultural waste but also provides a sustainable and eco-friendly strategy for efficient Ge separation and recovery. Full article
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22 pages, 15367 KiB  
Article
Investigation of Liquid Oils Obtained by Thermo-Catalytic Degradation of Plastic Wastes in Energy Recovery
by Mihaela Vlassa, Miuța Filip, Simion Beldean-Galea, Didier Thiébaut, Jerôme Vial and Ioan Petean
Molecules 2025, 30(9), 1959; https://doi.org/10.3390/molecules30091959 - 28 Apr 2025
Cited by 1 | Viewed by 408
Abstract
The most efficient technique for resolving the issue of plastic waste disposal is by converting the wastes into high-quality liquid oils through thermal and catalytic pyrolysis. The objective of this work was to study the composition of liquid oils obtained by thermal and [...] Read more.
The most efficient technique for resolving the issue of plastic waste disposal is by converting the wastes into high-quality liquid oils through thermal and catalytic pyrolysis. The objective of this work was to study the composition of liquid oils obtained by thermal and catalytic degradation of plastic wastes containing polystyrene (PS), polyvinyl chloride (PVC), and polyethylene terephthalate (PET). The clay catalysts were characterized by N2 adsorption–desorption isotherms (BET), Scanning Electron Microscopy (SEM) and Fourier transform Infrared Spectrometry (FTIR), Polarized Optical Microscopy (POM), Atomic Force Microscopy (AFM). The effect of temperature and clay catalyst type on the yields of the end-products resulting in thermo-catalytic degradation of PS has been evaluated. Degradation of PS showed the highest liquid oil production at 86.85% in comparison to other plastic types. The characterization of the liquid oils was performed by comprehensive two-dimensional gas chromatography coupled with single quadrupole mass spectrometry (GC × GC-qMS). In liquid oils of PS, eighteen principal compounds (of groups: linear hydrocarbons, mono-aromatics, and di-aromatics) were identified. In the liquid oils of the plastic waste mixture, twenty-four principal compounds (of groups: linear hydrocarbons, mono-aromatics, oxygen-containing aromatic, di-aromatics, and tri-aromatics) were identified. The liquid oils were investigated in order to reconvert them as styrene monomers or other chemicals in energy recovery. Full article
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21 pages, 6049 KiB  
Article
Sustainable Treatment of Amoxicillin-Contaminated Wastewater Using Fe2+/H2O2/AC: Performance, Stability, and Environmental Impact
by Sumita, Jibran Ali Ghumro, Jingzhen Su, Cong Li, Zhengming He and Jieming Yuan
Processes 2025, 13(4), 1054; https://doi.org/10.3390/pr13041054 - 1 Apr 2025
Viewed by 741
Abstract
This study investigates the activation mechanisms of hydrogen peroxide (H2O2) using iron-activated carbon (Fe2+/H2O2/AC) for the efficient degradation of amoxicillin (AM) in wastewater. The system achieved a high degradation efficiency of 90% under [...] Read more.
This study investigates the activation mechanisms of hydrogen peroxide (H2O2) using iron-activated carbon (Fe2+/H2O2/AC) for the efficient degradation of amoxicillin (AM) in wastewater. The system achieved a high degradation efficiency of 90% under alkaline conditions (pH 9), with singlet oxygen (1O2) and hydroxyl radicals (OH) identified as the dominant reactive species through scavenger experiments. High-performance liquid chromatography–mass spectrometry (HPLC-MS) analysis revealed degradation by-products and proposed reaction pathways, including the loss of amine groups, ring-opening oxidation, and bond cleavage. The structural and morphological properties of Fe2+/H2O2/AC were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET) analysis. The BET surface area of Fe2+/H2O2/AC was determined to be 128.36 m2/g, with a mesoporous structure facilitating efficient mass transfer and adsorption. The system was systematically evaluated under varying conditions, including H2O2 concentration (25–250 mg/L), catalyst dosage (0.05–1.0 mg/L), and pH (3–10). Kinetic analysis revealed that the degradation process follows pseudo-second-order kinetics (R2 = 0.966), while adsorption isotherms were best described by the Langmuir model (R2 = 0.98). Ecotoxicity tests indicated that the degradation products are less harmful to aquatic organisms. The system demonstrated excellent stability over three consecutive cycles, highlighting its potential for long-term application in treating pharmaceutical-contaminated wastewater. Full article
(This article belongs to the Section Environmental and Green Processes)
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