Search Results (106)

To achieve efficient separation of Sr²⁺ under complex ionic-strength conditions, porous geopolymer particles (PGs) were used as a support to construct a K₂SbPO₆-loaded porous geopolymer composite, denoted as K₂SbPO₆@PGs, via in situ loading of one-dimensional K₂SbPO₆ by a high-temperature solid-state route. Its adsorption performance and mechanism were systematically compared with those of pristine PGs. Structural characterization (SEM/EDS, XRD, FTIR, XPS, and BET) confirmed that the K₂SbPO₆ crystalline phase was uniformly anchored onto the PGs framework while preserving interconnected mesoporous channels. K₂SbPO₆@PGs exhibited excellent Sr²⁺ removal over a wide pH range (3–12), with a removal efficiency of approximately 92% at pH 3, which was significantly higher than that of PGs (approximately 5%). The isotherm data were better fitted by the Sips model (R² = 0.982), and the maximum adsorption capacity reached 189.35 mg·g⁻¹ (theoretical qm = 201.14 mg·g⁻¹). Kinetic fitting showed that PGs followed the pseudo-first-order model, whereas K₂SbPO₆@PGs were better described by the pseudo-second-order model, indicating that chemical adsorption dominated the process through K⁺/Sr²⁺ exchange and surface complexation. Coexisting-ion experiments demonstrated strong resistance to monovalent ions, whereas Ca²⁺ and Mg²⁺ caused more pronounced competitive effects. The results indicate that PGs mainly provide interconnected mass-transfer pathways and granular structural support, whereas K₂SbPO₆ provides selective exchange sites with high affinity for Sr²⁺. The synergy between these two components endows the composite with good pH adaptability and enhanced adsorption performance and suggests its potential for subsequent continuous-flow separation studies. Full article

Although amorphous calcium phosphate (ACP) has been extensively employed as a biomaterial in dental and orthopedic fields, its exploration for environmental applications—particularly in potentially toxic element remediation—remains notably limited in the scientific literature. This study reports the rational design of a multifunctional adsorbent by integrating sodium citrate-stabilized ACP (Cit-ACP) nanoparticles into calcium-crosslinked sodium alginate (SA) hydrogel beads for selective Cu²⁺ sequestration from aqueous systems. Comprehensive sorption assessments revealed that equilibrium uptake aligned with the Freundlich isotherm (indicating heterogeneous surface interactions), while kinetic profiles adhered to pseudo-second-order behavior, characteristic of chemisorption-driven processes. Under optimized operational parameters (pH 5.0, 45 °C), the Cit-ACP/SA composite attained an exceptional maximum adsorption amount of 307.76 mg/g. Thermodynamic analysis further confirmed the spontaneity (ΔG° < 0) and endothermic nature (ΔH° > 0) of the process. Multi-technique characterization (XPS, FTIR, XRD, pH trajectory) elucidated a dual-mode adsorption mechanism: (i) ion exchange between aqueous Cu²⁺ and structural Ca²⁺ within both the alginate matrix and ACP framework; and (ii) in situ surface precipitation yielding copper-substituted hydroxyapatite. Owing to its facile aqueous-phase synthesis, superior adsorption performance, biodegradability, macroscopic bead morphology enabling rapid separation, and robust selectivity in complex matrices, the Cit-ACP/SA composite presents a sustainable, scalable, and eco-compatible platform for practical remediation of copper-contaminated wastewater. Full article

A sustainable strategy was developed to valorize rabbit manure waste by synthesizing a porous quaternary Ni-Co-Zn-Fe layered double hydroxide/biochar nanocomposite (QL-RMB) for the efficient removal of Mn(VII) in the form of permanganate (MnO₄⁻) from aqueous solutions. The QL-RMB adsorbent exhibited a well-developed mesoporous structure with uniformly dispersed nanoparticles, achieving 73% MnO₄⁻ removal within 60 min under optimized conditions (pH 3.0; dosage 0.5 g L⁻¹). Adsorption followed pseudo-second-order kinetics and was best described by the Freundlich isotherm model (R² > 0.98), yielding a maximum Langmuir adsorption capacity (q_max) of 45.13 mg g⁻¹. Statistical physics modeling confirmed a multi-ionic, vertically oriented adsorption configuration, while thermodynamic analysis demonstrated that the process was spontaneous and exothermic, governed by electrostatic attraction, anion exchange, and surface complexation. The QL-RMB composite exhibited excellent MnO₄⁻ selectivity in the presence of competing ions (selectivity coefficients: 24.96 for Fe³⁺, 31.59 for Ni²⁺, 23.56 for Zn²⁺) and retained significant removal efficiency (73.96%) after five regeneration cycles. In a circular economy approach, the Mn (VII)-spent adsorbent (QL-RMB/Mn) was valorized as an electrocatalyst for urea electro-oxidation, achieving a current density of ~127.19 mA cm⁻² for pristine QL-RMB, which increased to ~217.07 mA cm⁻² after Mn(VII) adsorption (QL-RMB/Mn) in 1 M KOH/1 M urea. Batch scale-up studies revealed an efficiency of 42.55 g or 95% MnO₄⁻ removal from 50 L water, with a low estimated production cost of 0.0602 USD g⁻¹. Environmental sustainability was confirmed by the National Environmental Methods Index (NEMI), modified Green Analytical Procedure Index (Mo-GAPI), Eco-scale (score: 77), and Analytical GREEness (AGREE) assessment frameworks. Full article

Recycling spent lithium-ion batteries (LIBs) is critical for resource sustainability and carbon neutrality. This work presents a green strategy in which NaA zeolite is used to preferentially recover lithium from leachate of spent NCM111 batteries, combined with temperature-regulated stepwise separation of transition metals. Benefiting from the distinct hydrated ionic radii and charge density between Li⁺ and divalent metal ions, NaA zeolite selectively adsorbs Ni²⁺, Co²⁺ and Mn²⁺, leaving Li⁺ in the raffinate. Under optimized conditions, two-stage adsorption achieves 95.6%, 96.7% and 99.7% removal of Ni²⁺, Co²⁺ and Mn²⁺, respectively, with 11% Li⁺ co-adsorption. Thermodynamic analysis reveals that the adsorption process is endothermic and thermodynamically spontaneous. The interaction strength between metal ions and NaA zeolite follows the order Ni²⁺ > Co²⁺ > Mn²⁺, and ion exchange is identified as the dominant mechanism. It is determined that 96.8% of Mn²⁺ can be recovered at 0 °C, followed by the desorption of 93.5% of Co²⁺ at 90 °C, and the sequential separation of Mn, Co and Ni is realized. Three consecutive adsorption–desorption cycles demonstrate the acceptable reusability of the Ni-loaded NaA adsorbent. High-purity Li₂CO₃ (purity 96.7%, yield 93.5%), MnO₂ (purity 99.3%, yield 98.4%) and Co₃O₄ (purity 98.8%, yield 97.6%) are obtained from the corresponding solutions. This approach provides a scalable closed-loop pathway for full-component recovery of valuable metals from spent LIBs. Full article

In this work, iron–phosphorus-based composite biochar (FPBC) was prepared by modification with the leachate of spent LiFePO₄ batteries. The effects of solution pH, dosage, adsorption time, initial concentration, and temperature on the adsorption performance of FPBC were investigated by batch adsorption experiments with Pb(II) and Sb(III) as the target pollutants, and the adsorption mechanism was explored using SEM, BET, XPS, FTIR and XRD characterization. The results indicated that as the initial pH of the solution increased, the removal efficiency of FPBC for Pb(II) gradually increased, while the removal efficiency for Sb(III) remained largely unchanged. The removal of Pb(II) and Sb(III) by FPBC fitted the pseudo-second-order kinetic model and the three-step intraparticle diffusion model, indicating that their removal was primarily controlled by chemical adsorption. Isothermal adsorption studies revealed that FPBC adsorption of Pb(II) better fitted the Langmuir and D-R models, suggesting a monolayer-dominated adsorption process. In contrast, adsorption of Sb(III) fitted the Langmuir, Freundlich, and Temkin models, suggesting a combination of monolayer and multilayer adsorption characteristics. The maximum adsorption capacities of FPBC for Pb(II) and Sb(III) were 312.54 mg·g⁻¹ and 219.20 mg·g⁻¹ at 30 °C, which were approximately 12.85 and 3.37 times those of commercial corn stalk biochar (BC). Thermodynamic analysis confirmed that the removal of Pb(II) and Sb(III) by FPBC was a spontaneous and endothermic process. In addition, FPBC demonstrated strong selective adsorption of Pb(II) in the binary co-adsorption system of Pb(II) and Sb(III). Mechanism studies indicated that Pb(II) removal primarily occurred through co-precipitation, complexation, ion exchange, and electrostatic adsorption, while Sb(III) was mainly adsorbed by FPBC via redox reactions and complexation. Therefore, this work not only provides a low-cost, high-performance adsorbent for the remediation of water contaminated with Pb(II) and Sb(III), but also opens up new avenues for the resource recovery of the leachate of spent LiFePO₄ batteries. Full article

Addressing the need for efficient separation of critical elements from NdFeB magnets, this study introduces, for the first time, a D001 cation exchange resin for the selective separation Co(II) from Nd(III) and Dy(III). At pH 5, the resin adsorbs Nd and Dy with high capacities (97.57 and 86.38 mg/g, respectively) and efficiencies (over 98%), but shows low affinity for Co (26.6% efficiency). The resin exhibits excellent stability across a wide pH range of 2–7 and maintains high adsorption performance over five consecutive cycles. The process follows pseudo-second-order kinetics and the Langmuir model. Co(II) is effectively desorbed with high purity (>99%) using 2.5 M H₂SO₄. Characterization confirms that adsorption occurs via ion exchange on –SO₃Na groups. This method successfully separates Co, providing a high-purity stream for further rare earth purification and demonstrating strong industrial potential. Full article

This study explores the effect of cation adsorption on the shear strength and mineralogical characteristics of smectite-rich landslide clay collected from the Nishinotani landslide in Ehime Prefecture, Japan. Laboratory experiments were conducted using aqueous solutions of calcium, magnesium, and potassium chlorides at concentrations of 1000, 6000, and 12,000 mg/L. Ion chromatography, X-ray diffraction (XRD), and ring shear tests were conducted to evaluate the interaction between ion uptake and its influence on the change in shear strength. The results showed that calcium and potassium ion adsorption increased with both concentration and time, leading to enhanced residual shear strength and crystallinity, primarily due to stronger Coulombic interactions and favorable ionic size compatibility with smectite. Conversely, magnesium ions exhibited adverse effects, including reduced strength and mineral ordering, attributed to calcium leaching and weaker interparticle bonding. The findings indicate that selective cation exchange can be an effective, sustainable alternative to conventional landslide stabilization methods, especially in fine-grained, expansive clay systems. This work contributes to the development of geochemically engineered landslide mitigation strategies based on microstructural and mineralogical reinforcement. Full article

A comparative sorption dependence was carried out between the Dowex HCR-S/S″ industrial ion-exchange sorbent and the synthesized ion-exchange sorbent based on dibenzylamine, epichlorohydrin and polyethylenimine in relation to copper and silver ions. The sorption of copper and silver was studied by ionometry and the dependences of the sorption of copper and silver ions in the static mode were established depending on the concentration of metal ions and the duration of ionite contact with solutions of copper and silver nitrates. It was found that the maximum sorption capacity of the synthesized ion exchanger is 672.4 mg/g for copper ions and 721.0 mg/g for silver ions, and 626.3 mg/g and 679.7 mg/g for industrial Dowex HCR-S/S″ ionite, respectively. It is shown that the sorption of copper and silver is described by various kinetic models: for copper, the best correspondence is demonstrated by a pseudo second order kinetic model, whereas for silver, the Elovich kinetic model the different nature of the interaction of ions with active centers. It has been revealed that the synthesized ion exchanger is superior to an industrial sorbent in terms of sorption rate and degree of extraction of valuable metals, especially in concentrated solutions, which indicates the prospects of its use in the processes of selective extraction of copper and silver. Full article

This study investigated the potential of a commercially available birch biochar, previously used as a soil amendment, for the adsorption of Pb²⁺ ions from aqueous solutions. For the first time, direct potentiometry with a lead ion-selective electrode was used for continuous in situ real-time monitoring of the adsorption process. The biochar demonstrated a maximum adsorption capacity of 14.21 mg/g (Langmuir model) and a high affinity for Pb²⁺. Kinetic analysis revealed a two-stage process limited by intraparticle diffusion. A significant decrease in pH and power-law dependencies between the adsorption parameters and the liquid/solid ratio confirmed ion exchange as the primary mechanism. Additionally, the biochar’s surface characteristics and accessibility for large molecules were evaluated by methylene blue adsorption, yielding a specific surface area of 4.0–6.6 m²/g. This value, being an order of magnitude lower than the BET surface area, highlighted the microporous nature of the biochar and its limited accessibility for bulky organic cations, providing crucial context for interpreting the lead adsorption mechanisms. The biochar effectively reduced the lead concentration to levels meeting the standards for irrigation water, demonstrating its dual application not only as an amendment but also as an effective and stable sorbent for water purification, while direct potentiometry proved to be a promising method for studying such processes. Full article

Graft copolymers of polysaccharides with side chains of carbon-chain monomers have significant potential for a variety of practical applications. In this work, the effect of the N,N-methylenebisacrylamide (MBA) introduction stage and acrylamide concentration in microwave-assisted radical copolymerization with xanthan gum on the structure and sorption properties of the cross-linked graft copolymer was studied. It has been found that the spatial network density and average molecular weight of interstitial fragments can be controlled by varying these factors. Moderate crystallinity (<50%) and a highly developed surface of our synthesized samples were revealed using XRD and SEM. The graft copolymer exhibits the Schroeder effect; its liquid water sorption obeys Fick’s law and increases with MBA introduction at later stages and with increasing grafting degree, reaching 17.2 g/g. Studying the methylene blue sorption kinetics using pseudo-first/pseudo-second order models, a combined model and an average pseudo-order model have shown that the lower the monomer concentration in the reaction mixture and the earlier (from the onset of the reaction) the cross-linking agent is introduced, the higher the equilibrium sorption. The observed “equilibrium degree of sorption on xanthan gum vs. pseudo-order” relationship, which passes through a minimum, is explained by chemisorption and the sorbate consumption effect. An assumption is made about the prospects of using our synthesized copolymers for designing selective sorbents and ion-exchange membranes. Full article

Lithium (Li) ion sieve is considered to have great potential in the selective extraction of Li⁺ from complex Li⁺-containing brine owing to its cost-effectiveness, excellent adsorption performance, and environmental friendliness. Nevertheless, the defects of complex regulation and control of technological parameters in the preparation process of Li ion sieve and poor recycling efficiency limit its application. In this study, spinel-type H₄Ti₅O₁₂ ion sieves (HTO) were successfully prepared through a high-temperature solid-state method for recovering Li⁺ from aqueous resources. Through the experiment of optimizing the key preparation process parameters of HTO, it was found that the optimum preparation conditions were as follows: lithium ion source of CH₃COOLi‧H₂O, calcination temperature of 800 °C, and acid (HCl) washing concentration of 0.3 mol/L. The uptake of Li⁺ by HTO aligned with the pseudo-second-order kinetic model, which was a chemical adsorption process controlled by reversible Li–H ion exchange reaction. HTO exhibited extremely high regeneration cycle characteristics, and after five cycles, it retained 96.06% of its initial adsorption capacity. The present work highlighted that spinel-type HTO has high industrial application potential in the field of Li⁺ recovery from oilfield brine. Full article

High-alumina fly ash may potentially be a valuable source of Ga with a concentration of Ga at 80 mg/kg. Direct adsorption and enrichment of Ga from sulfuric acid leach liquor of high-alumina fly ash is developed in this study. The H-type chelating resin with two carboxy groups exhibited the best adsorption capacity for Ga. The maximum adsorption capacity for Ga was 55 mg/g resin with an adsorption time of 24 h, an initial Ga concentration of 500 mg/L, an adsorption temperature of 55 °C, and an initial acid concentration of 0.1 mol/L. The adsorption process of Ga was in good fit with the Langmuir isotherm and pseudo-second-order reaction kinetics model. The chemical adsorption rate was controlled by an internal diffusion mechanism. The resin had a high selectivity for Ga³⁺ with a K_d over 3600 compared with Fe²⁺, Al³⁺, K⁺, Ca²⁺, and Mg²⁺. The adsorption mechanism was found to be the ion exchange reaction between Ga and H of carboxy and hydroxyl groups. The concentration of Ga in sulfuric acid leach liquor from high-alumina fly ash achieved enrichment from 200 mg/L to 2 g/L. It is an attractive medium for large-scale Ga extraction from high-alumina fly ash. Full article

Through the use of heterogeneous catalysts, catalytic ozone oxidation technology, an effective and eco-friendly advanced oxidation process (AOP), facilitates the breakdown of ozone into reactive oxygen species (like ·OH) and greatly increases the mineralization efficiency of pollutants. This study examines the development of heterogeneous ozone catalysts through a critical evaluation of the five primary preparation techniques: ion exchange, sol–gel, coprecipitation, impregnation, and hydrothermal synthesis. Each preparation method’s inherent qualities, benefits, drawbacks, and performance variations are methodically investigated, with an emphasis on how they affect the breakdown of different resistant organic compounds. Even though heterogeneous catalysts are more stable and reusable than homogeneous catalysts, they continue to face issues like active component leaching, restricted mass transfer, and ambiguous mechanisms. In order to determine the key paths for catalyst selection in catalytic ozone treatment going forward, the main goal of this review is to provide an overview of the accomplishments in the field of the heterogeneous ozone catalyst treatment of wastewater that is difficult to degrade. Full article

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

Phosphate and fluoride ions are common water pollutants whose presence and excessive discharge cause potential hazards to the environment and human health. MOF materials commonly used to remove phosphate and fluoride ions are usually in powder form, with low recovery during regeneration. Herein, to address these issues, Fe₃O₄@La-Zr-MOFs magnetic composites for phosphate and fluoride removal were fabricated by means of the hydrothermal method. The adsorption properties of the adsorbent were systematically assessed by means of adsorption experiments. The magnetic Fe₃O₄@La-Zr-MOFs exhibited a magnetic recovery efficiency of 93%, and they could maintain outstanding adsorption performance at a broad range of pH values and superior selectivity for phosphate and fluoride ions. The adsorption process conformed to the Langmuir isotherm and pseudo-second-order models, indicating that it was dominated by monomolecular chemisorption. Further characterization of the Fe₃O₄@La-Zr-MOFs before and after adsorption and kinetic thermodynamic investigation revealed that the elimination mechanism of phosphate and fluoride ions by Fe₃O₄@La-Zr-MOFs includes ion exchange, electrostatic interactions, and surface complexation. This study demonstrates that magnetic reusable Fe₃O₄@La-Zr-MOFs composites have great promise for phosphate and fluoride removal and recovery. Full article