Recovery Of Metal Ions Research Articles

Tactfully introducing amphoteric group into electroactive membrane motivates highly efficient H2O splitting for reversible removal and recovery of nickel(II)

Membrane-based electro-deposition (MED) is an original process promising for reversible removal and recovery of toxic heavy metal ions from wastewater. The removal efficiency of heavy metal ions, however, was limited by the poor membrane surface H2O splitting in the conventional ion exchange membrane (IEM). Inspired by the amphoteric interface-triggered ion exchange resin regeneration phenomenon in electro-deionization, herein we subtly introduced the amphoteric group into IEM as a proof of concept to solve the above bottleneck. By virtue of the “electronic porter” role of the amphoteric -3OS-R-N(CH3)3+, the electron extraction from adsorbed H2O could be accelerated, extending the H2O splitting from the conventional membrane surface to the bulk membrane interior. Such an H2O splitting extension favorably produced an intensified and well-modeled OH- production region at the anodic side of IEM, enhancing the Ni2+ basic deposition accordingly. This special characteristic allowed our MED to realize a super-eminent metal ion removal rate (10.5 mol·h−1·m−2) along with an ultra-low specific energy consumption (0.1 kWh·mol−1) for Ni2+ removal, which considerably surpassed those of state-of-the-art heavy metal ion removal processes reported yet. Further, the deposited Ni2+ could be in situ recovered in conjunction with the facile polarity reversal method. The amphoteric electroactive membrane with high H2O splitting activity is expected to pave the path to engineering MED for efficient heavy metal ion removal and recovery.

Enrichment of lithium ions for battery application by electrolysis through a nanoporous membrane

In recent years, lithium (Li) has become a valuable commodity widely used in rechargeable batteries. The present study aims to extract battery-grade lithium-ion, as lithium hydroxide (LiOH), from lithium chloride (LiCl) solution by the membrane electrolysis process. Experiments are performed using a commercial cation exchange membrane and an indigenous High flux-Nanofiltration 300 alkali resistant (HF-NF 300 AR) nanoporous membrane. The dual-chamber electrolytic cell incorporates a selective membrane to separate the feed and concentrate chambers containing LiCl solution and deionized water. These two chambers are connected with titanium electrodes through the external circuit. The in-situ design of the compact two-chambered acrylic electrolytic cell helps to separate metal ions from ionizable salts of sodium, lithium, magnesium, potassium, etc. The experiment is conducted on a laboratory scale by varying the LiCl concentration at voltages of 24 V and 36 V. The feed and concentrate solutions are analyzed for pH, conductivity, and total dissolved solids. Inductively coupled plasma-optical emission spectrometry evaluates the presence of metal ions in the solution. The study shows effective metal ion recovery and separation to achieve battery-grade Li.

Evaluation of a triethylenetetramine-chitosan derivative for the removal of palladium ion from an intricate adsorbate system

Palladium (Pd), a well-known noble metal for its exceptional physical and chemical properties, finds widespread applications in sectors including automotive, hydrogen purification, dentistry, coinage, and jewelry. The growing demand for Pd has led to resource scarcity. This feature necessitated upon the economically and environmentally viable means for the reclamation of the precious metal ions from secondary sources. This article delves into the Pd adsorptive-desorption trends associated with the triethylenetetramine cross-linked chitosan (CH-TETA) derivative in moderately complex solutions. The effect of moderate solution chemistry complexity, incorporating ammonium hydroxide (NH4OH) and ethylenediaminetetraacetic acid (EDTA), within the synthetic electroless plating (ELP) solutions was investigated. Batch adsorption experiments were conducted through a variation of process parameters namely solution pH, CH-TETA dosage, adsorption duration, initial Pd concentration, and temperature. CH-TETA demonstrates an impressive Pd adsorption capacity ranging from 43.53 to 117.08 mg g⁻¹ and is correspondingly accompanied by the metal removal efficiency range of 87.05 % to 39.03 %. Such promising performance has been ascertained for an initial Pd constitution of 50 to 300 mg L⁻¹. Despite constituting other additives in the adsorbate system, utilizing simple acidic and basic eluents, the CH-TETA derivative exhibited a reasonable recovery efficacy of 39.68 %. Thereafter, recovery of Pd can be further enhanced into two approaches. In these, the first refers to the utilization of various other methods such as thermal, electrochemical, ultrasound, and microwave-assisted regeneration from spent adsorbents. Secondly, a pre-treatment method can be adopted to remove the additives prior to the adsorption process. In summary, the recovery of precious metal ions from the spent adsorbents has been a challenging task. Based on the discussion, further improvements based on the findings of this article are possible by targeting relevant research methodologies in resin chemistry and regeneration methods.

Preliminary studies on ion-pair extractions of Zr, Hf, Nb, and Ta using extractants having tertiary N atom from H2SO4 and HF

Abstract Ion-pair extraction enables the recovery of anionic metal ions, such as pertechnetate and chlorinated rhodium ions, by protonated extractants with tertiary amino N atom in their structures. We expand this technique for other anionic species dissolved in different mineral acids. Extractions of Zr, Hf, Nb, and Ta, metal anions present in sulfuric and hydrofluoric acids (H2SO4 and HF), are examined. Zr and Hf in H2SO4, and Zr, Hf, Nb, and Ta in HF can be extracted by ion-pair extraction using NTAamide (nitrilotriacetamide), methylimino-N, N’-dioctylacetamide (MIDOA), and trioctylamine (TOA). Basic information about their extraction behavior was obtained through this study.

Removal of Heavy Metals by Pseudomonas sp. - Model Fitting and Interpretation.

Industrial and urban modernization processes generate significant amounts of heavy metal wastewater, which brings great harm to human production and health. The biotechnology developed in recent years has gained increasing attention in the field of wastewater treatment due to its repeatable regeneration and lack of secondary pollutants. Pseudomonas, being among the several bacterial biosorbents, possesses notable benefits in the removal of heavy metals. These advantages encompass its extensive adsorption capacity, broad adaptability, capacity for biotransformation, potential for genetic engineering transformation, cost-effectiveness, and environmentally sustainable nature. The process of bacterial adsorption is a complex phenomenon involving several physical and chemical processes, including adsorption, ion exchange, and surface and contact phenomena. A comprehensive investigation of parameters is necessary in order to develop a mathematical model that effectively measures metal ion recovery and process performance. The aim of this study was to explore the latest advancements in high-tolerance Pseudomonas isolated from natural environments and evaluate its potential as a biological adsorbent. The study investigated the adsorption process of this bacterium, examining key factors such as strain type, contact time, initial metal concentration, and pH that influenced its effectiveness. By utilizing dynamic mathematical models, the research summarized the biosorption process, including adsorption kinetics, equilibrium, and thermodynamics. The findings indicated that Pseudomonas can effectively purify water contaminated with heavy metals and future research will aim to enhance its adsorption performance and expand its application scope for broader environmental purification purposes.

In situ self-assembly of ZIF-8@sodium alginate composite hydrogels for enhanced adsorption of Cu2+ Ions

With the advancement of science and technology, the issue of wastewater pollution has escalated, necessitating urgent attention to wastewater treatment. In this study, a highly efficient adsorbent for Cu2+ was successfully synthesized through in situ self-assembly using Ca2+ as the cross-linking agent in ZIF-8@ALG composite hydrogel. The results demonstrated that the incorporation of Ca2+ as the cross-linker enhanced both adsorption capacity and swelling properties of ZIF-8@ALG composite hydrogel. Adsorption performance evaluation revealed that the hydrogel followed pseudo-second-order kinetic model for Cu2+ adsorption and Freundlich isotherm model with a theoretical maximum adsorption capacity of 309.57 m g−1. Thermodynamic analysis indicated that Cu2+ adsorption onto the hydrogel occurred spontaneously with heat absorption. Furthermore, excellent reusability was observed after five cycles of usage without significant loss in adsorption efficiency. Overall, these findings highlight the potential application of ZIF-8@ALG composite hydrogel as an effective solution for wastewater remediation and recovery of heavy metal ions.

A hydrometallurgical process for the recovery of copper metal and nickel hydroxide from the aqua regia leaching solutions of printed circuit boards

Leaching solutions of printed circuit boards (PCBs) contain noble and base metal ions. The precious metal ions present in the leaching solutions of PCBs could be separated by cementation with copper metal. After recovery of precious metal ions by cementation, the filtrate contains Cu(II) together with base metal ions like Al(III), Fe(III), Fe(II), Ni(II), Sn(II), and Zn(II). In this work, separation experiments were conducted to recover Cu(II) and Ni(II) from the filtrate. First, copper ions were completely separated from the filtrate by chemical reduction with hydrazine at the following conditions: a molar ratio of 8 for hydrazine to Cu(II), 20°C, 500 rpm, and 20 mins. By adding sodium oxalate to the solution after separation of Cu(II), most of the Ni(II) and 38% of the Zn(II) were co-precipitated at 20°C, 60 mins, 500 rpm, and a molar ratio of 20 for sodium oxalate to nickel. After dissolving the co-precipitates of Ni(II) and Zn(II) oxalates in a 0.5 M HCl solution, the Zn(II) was completely removed from the solution by a five-stage cross-current extraction with 2.5 M Cyanex 272. Nickel hydroxides were then recovered from the raffinate by precipitation with NaOH. The purity of the copper metal and nickel hydroxides was higher than 99%. A process was proposed to recover Au(III), Pd(II), Cu(II), and Ni(II) from the leaching solutions of PCBs.

Research Progress on Metal Ion Recovery Based on Membrane Technology and Adsorption Synergy.

The development of modern industry will generate more and more waste containing metal ions. It is necessary to take appropriate measures to recover these ions, whether from the perspective of environmental protection or improving economic benefits. So far, scientists have studied many methods for recovering metal ions. Among these methods, adsorption and membrane separation have received widespread attention due to their own characteristics. Combining adsorption and membrane separation methods can better leverage their respective advantages to improve the ability of recovering metal ions. This review, therefore, focuses on the synergistic recovery of metal ions by adsorption and membrane separation methods. This article first briefly explains the theoretical principles of membrane separation and adsorption synergy, and then focuses on several technologies that have received attention in different chapters. In these chapters, membrane technology is briefly introduced, followed by the situation and progress of synergistic application with adsorption technology. Then, the article compares and elaborates on the advantages and disadvantages of the above technologies, and finally summarizes and looks forward to these technologies being used to solve the difficulties and challenges in industrial application.

High energy-efficiency decomplexation of metal-complexes by H*-mediated electro-reduction on hydroxyphenyl Co-porphyrin catalysts

Electrochemical reduction of metal-organic complex pollutants has been recognized as an environmental benign method that operates at mild condition. However, the selective reduction of metal complexes and energy consumption in cathodic process are still a big challenge. Herein, we found that hydroxyphenyl Co-porphyrin catalyst (CoTH@NG) realizes the highly selective decomplexation of metal-organic complexes by H* -mediated reduction, and simultaneously the impressive recovery efficiency of metal ions. Density functional theory (DFT) confirms the generation and capturing ability of H* on CoTH@NG, verifying the dominant role of H* -mediated reduction in the selective decomplexation of Cu-EDTA. CoTH@NG realizes the superior energy efficiency for Cu-EDTA removal (279.3 g kWh−1 of EEOCu-EDTA) and Cu recovery (48.6 g kWh−1 of EEOCu), which are remarkably 3.3 × 102 and 9.7 × 102 times higher than traditional carbon cloth electrode. Moreover, the recovered Cu0(s) nanowires on the electrode surface can be efficiently regenerated in HCOOH by a galvanic reaction through the electron channel of CoTH@NG, regenerating catalytic electrode. This is one of the pioneer studies on H* -mediated electro-reduction decomplexation of metal-complexes, metal recovery, and electrode regeneration on CoTH@NG, which providing a technical strategy for developing efficient electrocatalytic system for pollution control.Environmental ImplicationMetal complexes is a dramatic increase in the electroplating and mining industries, and seriously affect both public health and environmental sustainability. Our work reported a new hydroxyphenyl Co-porphyrin catalyst (CoTH@NG) which achieves the selective decomplexation of metal-organic complexes, and simultaneously the recovery of metal ions. CoTH@NG realizes the superior energy efficiency for Cu-EDTA removal (279.3 g kWh−1) and Cu0(s) recovery (48.6 g kWh−1), which are remarkably 3.3 × 102 and 9.7 × 102 times higher than traditional carbon cloth electrode. Moreover, the recovered Cu0(s) can be efficiently regenerated in HCOOH by a galvanic reaction through the electron channel of CoTH@NG, regenerating catalytic electrode.

Modern Rare Earth Imprinted Membranes for the Recovery of Rare Earth Metal Ions from Coal Fly Ash Extracts.

The need to identify secondary sources of REEs and their recovery has led to the search for new methods and materials. In this study, a novel type of ion-imprinted adsorption membranes based on modified chitosan was synthesized. Their application for the recovery of chosen REEs from synthetic coal fly ash extracts was analyzed. The examined membranes were analyzed in terms of adsorption kinetics, isotherms, selectivity, reuse, and their separation abilities. The experimental data obtained were analyzed with two applications, namely, REE 2.0 and REE_isotherm. It was found that the adsorption of Nd3+ and Y3+ ions in the obtained membranes took place according to the chemisorption mechanism and was significantly controlled by film diffusion. The binding sites on the adsorbent surface were uniformly distributed; the examined ions showed the features of regular monolayer adsorption; and the adsorbents showed a strong affinity to the REE ions. The high values of Kd (900-1472.8 mL/g) demonstrate their high efficiency in the recovery of REEs. After five subsequent adsorption-desorption processes, approximately 85% of the value of one cycle was reached. The synthesized membranes showed a high rejection of the matrix components (Na, Mg, Ca, Al, Fe, and Si) in the extracts of the coal fly ashes, and the retention ratio for these Nd and Y ions was 90.11% and 80.95%, respectively.

Magnetic sodium titanate nanotubes for simultaneous recovery of multiple low-level heavy and radioactive metal ions

Heavy and radioactive metal ions pollutants in water are a serious environmental problem and cause various health issues which lead to fetal human diseases. Herein, magnetic sodium titanate nanotubes (Fe3O4/NaTNTs) as magnetically separable nanostructure composite material were synthesized and used as adsorbent for simultaneous removal of multiple metal ions contaminants. HRTEM, SEM, FTIR, EDX, XRF, XRD, thermal gravimetric analysis (TGA), and zeta potential analysis were used for Fe3O4/NaTNT characterization. Thirteen metal cations including Th4+ and U4+, have been tested for competitive and simultaneous sorption on Fe3O4/NaTNTs nanostructure. In the mixed metal ions system, the removal efficiency of Co2+ and Pb2+ is the highest (Co2+; 95.9 %, Pb2+; 94.2 %). The relative selectivity for the removal of Cs+ ions (32 %) is more than that of Sr2+ ions (25 %). Thus, the data indicates the potential of Fe3O4/NaTNTs to be used in wastewater treatment, especially to simultaneously remove multiple heavy metal ions. Fe3O4/NaTNTs sorbent can be used for the rapid removal of heavy elements to mitigate large quantities of water pollution in emergencies, such as nuclear accidents and leaks.

Recovery of Metal Ions (Cd2+, Co2+, and Ni2+) from Nitrate and Sulfate on Laser-Induced Graphene Film Using Applied Voltage and Its Application.

The urgent removal of Cd, Co, and Ni from nitrate and sulfate is essential to mitigate the potential risk of chemical pollution from large volumes of industrial wastewater. In this study, these metal ions were rapidly recovered through applying voltage on nitrate and sulfate, utilizing laser-induced graphene/polyimide (LIG/PI) film as the electrode. Following the application of external voltage, both the pH value and conductivity of the solution undergo changes. Compared to Co2+ and Ni2+, Cd2+ exhibits a lower standard electrode potential and stronger reducibility. Consequently, in both nitrate and sulfate solutions, the reaction sequence follows the order of Cd2+ > Co2+ > Ni2+, with the corresponding electrode adsorption quantities in the order of Cd2+ > Co2+ ~ Ni2+. Additionally, using the recovered Co(OH)2 as the raw material, a LiCoO2 composite was prepared. The assembled battery with this composite exhibited a specific capacity of 122.8 mAh g-1, meeting practical application requirements. This research has significance for fostering green development.

Hybrid copper-polyelectrolyte nanoaggregates obtained with smart block copolymers based on 4-[(hydroxyimino)aldehyde]butyl methacrylate (HIABMA) in water and acetonitrile

The AB multi-stimuli-responsive block copolymer pTEGMA-b-pHIABMA (TEGMA: tetra(ethyleneglycol) methyl ether methacrylate; HIABMA: 4-[(hydroxyimino)aldehyde]butyl methacrylate) comprises a hydrophilic and thermoresponsive PTEGMA block linked to the hydrophobic PHIABMA chain. The latter is endowed with slightly acidic oxime groups that potentially form complexes with metal ions. Here we investigate the formation of hybrid Cu(II)-polymer nanoaggregates both in water and in acetonitrile. Cu(II) ions are quantitatively and rapidly incorporated, in the presence of a base, into pre-formed polymeric core-shell micelles (30 nm diameter by DLS) in water up to 1:2 metal-to-ligand stoichiometry. The pKa of the polymer is decreased from ≅11.2 to 4.65 due to interaction with Cu(II) and the complex is shown to involve oximate ions. The thermoresponsivity of the polymeric micelles remains unchanged with Cu(II) complexation and allows an easy separation by flocculation of the hybrid complex. Moreover, nanoaggregates (D = 20 nm) form in acetonitrile from the fully solubilized copolymer interacting with Cu(OAc)2. The 1:2 Cu(II)/ligand stoichiometry is confirmed with the Job graphical method. Characterization of the hybrid micelles was carried out by UV–Vis spectrometry, DLS, TEM, STEM and SAXS. Quantitative release of Cu(II) in acidic conditions is demonstrated both in water and in acetonitrile. Full recovery of the free metal ions and of intact polymeric micelles is achieved through centrifugal filtration of the aqueous preparation, as a proof-of-concept for a recyclable system for metal uptake and release. Furthermore, Cu0 nanoparticles of 5–10 nm are obtained through reduction of Cu(II) within the micelles with ascorbic acid in aqueous solution.

Characterization and application of synthesized calcium alginate-graphene oxide for the removal of Cr3+, Cu2+ and Cd2+ ions from tannery effluents

Environmental sustainability has gained acceptance to achieving the goal of a secure ecosystem with a reliable management system. Heavy metal remediation of aqueous streams is of special concern due to the intractability and persistence in the environment. Adsorption is a potential alternative to the existing inefficient conventional technologies for the removal and recovery of metal ions from aqueous solutions and becomes vital to align with the Sustainable Development Goals (SDGs) and mitigate the adverse environmental and social impacts. Calcium Alginate-Graphene oxide (CA-GO) composite has been synthesized for the adsorption of heavy metals including Cr3+, Cu2+, and Cd2+ ions from tannery effluents. Graphene oxide is prepared from commercial graphite powder and reacted with sodium alginate and calcium chloride to form the beads of CA-GO composite. The developed composite was characterized by FTIR, elemental analysis, SEM, XRD analysis, and Raman spectroscopy. Moreover, the effect of pH, adsorbent dosage, contact time, and initial concentration of metal ions on the adsorption capacity were investigated through batch experiments. At a pH>3.0 (pHzpc), the carboxyl group of CA-GO was deprotonated to make the surface negatively charged and facilitate metal adsorption. The optimum pH and maximum adsorption capacity of CA-GO for removal of Cr(III), Cu(II), and Cd(II) were 4.5, 6.0, and 7.0, and 90.58, 108.57, and 134.77 mg g−1, respectively. The kinetics, adsorption isotherms, and thermodynamics were studied to determine the adsorption mechanism. The kinetic of adsorption adopted the second-order model. Thermodynamic parameter were calculated and the adsorption process was determined to be exothermic and spontaneous at room temperature. The developed composite has been efficaciously applied for the removal of metal ions and pollution from real tannery effluents.

Valorization of battery manufacturing wastewater: Recovery of high-value metal ions through reaction-enhanced membrane cascade

Leveraging the latent value within battery manufacturing wastewater holds considerable potential for promoting the sustainability of the water-energy nexus. This study presents an efficient method for recovering transition metal ions (Ni2+, Co2+, Cu2+, and Cd2+) from highly saline battery wastewater (Na+, Li+, K+, or Mg2+). Our approach involves the effective utilization of a reaction-enhanced membrane cascade (REMC), comprising a meticulously orchestrated series of selective complexation-decomplexation steps involving polyethyleneimine (PEI) and various transition metal ions. This strategic intervention effectively segregates transition metal ions from salt ions during the fractionation process using an ultrafiltration membrane in a diafiltration process, overcoming osmotic pressure limitations. The ensuing concentration step via nanofiltration achieves an impressive 99 % yield and an extraordinary 215-fold concentration of transition metal ions (>99.8 % purity). The proposed method was validated with 16 different ion pairs to demonstrate its versatility, offering a pragmatic pathway for recycling various transition metal ions from industrial wastewater.

Dopamine inspired lignin-derived green emissive carbon dots for pH sensing and metal ions separation

Lignin is the most abundant, but underutilization polyphenolic material on the earth. In this paper, an integrated platform for pH sensing and ions separation was prepared from lignin to make use of this abundant bioresource. Demethylation of enzymatic hydrolysis lignin was first achieved to mimic the catechol structure of dopamine. The demethylated lignin was then converted into carbon dots by a facile hydrothermal treatment. The as-prepared carbon dots emit green fluorescence with enhanced quantum yield, and exhibited pH-responsive color changes from yellow-green to blue. When incorporated into a chitosan aerogel, the pH-responsive property of the carbon dots was intact, whereas the adsorption capacity of the aerogel for Cu2+ ions was noticeably improved, which was owed to the abundant oxygen containing functional groups and unique optical properties of the as-prepared carbon dots. This study provides a feasible approach to convert lignin into fluorescent nanomaterials for pH sensing and metal ions recovery from wastewater.

Interfacial self-assembled of covalent organic framework onto MXenes for efficient enrichment and recovery of Au(III) and Pd(II) from aqueous solution

Recovery of precious metal ions in wastewater could not only improve resource utilization, but also could reduce environmental pollution. Herein, a composite of TpPa@Nb2C was constructed by an interfacial self-assembled method and explored the synergistic adsorption effects for precious metals. The structure and morphology of the composites were analyzed by advanced characterization techniques, followed by parametric analysis of Au(III)/Pd(II) adsorption from the simulated wastewater. The results showed that the grafting of COFs with abundant reducing active sites on the MXenes could significantly improve the selectivity and adsorption capacity. Meanwhile, the interaction was found as monolayer way and controlled by chemistry process, and the maximum equilibrium Au(III) and Pd(II) uptake reached up to 910.1 and 386.2 mg/g, respectively. The competitive adsorption study showed that the co-existence of impurities had little effect on the removal rate. The mechanism analysis demonstrated that the precious metal ions were reduced to elemental gold/palladium on the network of TpPa@Nb2C, and they got three electrons or two electrons from the hydroxyl groups through redox reaction, respectively. Thus, this study provided an excellent material for enrichment and recovery of precious metals in waste liquid and the treatment of e-waste.

Electric-field enhanced three-dimensional flexible carbon felt as a host for Pt4+ ions extraction

The extraction of the precious metal Pt4+ ions from aqueous solution are of great importance for both economic development and environmental protection. In this study, an electric field assisted adsorption process with high efficiency and recyclability was explored in a self-made device using three-dimensional (3D) flexible carbon felt (FCF) as the adsorbent without using conductive adhesive. Under the aid of an electric field (0.4 V), 3D pristine FCF (p-FCF) showed a considerable adsorption capacity for Pt4+ (82 mg/g). As high as 203 mg/g was obtained when o-NFCF adsorbents modified with N doping and surface oxygen-containing groups was used. Kinetic and thermodynamic studies show that the electric field would enhance the interactions between the adsorbent and Pt4+ ions, and improve the intraparticle diffusions. Mechanism study showed that the synergistic effect between N doping and oxygen-containing groups might efficiently tune the electrochemical properties of 3D FCF materials, which significantly contributed to the enhanced adsorption of Pt4+. The electroadsorption technology developed in this study provides a simple and efficient method for industrial recovery of precious metal ions.

Highly efficient Mn2+, Mg2+, and NH4+ recovery from electrolytic manganese residue via leaching, solvent extraction, coprecipitation, and atmospheric oxidation

Electrolytic manganese residue (EMR), a solid waste generated during electrolytic manganese production, exhibits substantial leaching toxicity owing to its elevated levels of soluble Mn2+ and NH4+. The leaching and recovery of valuable metal ions and NH4+ from EMR are key to the hazard-free treatment and resource utilization of EMR. In this study, two-stage countercurrent leaching with water was used to leach Mn2+, Mg2+, and NH4+ from EMR. Subsequently, two-stage countercurrent extraction was conducted using α-hydroxy-2-ethylhexyl phosphinic acid (α-H-2-EHA) as an extractant to enrich Mn2+, and Mg2+, and NH4+ were recovered via coprecipitation. Based on the calculations for a single leaching-extraction process, the recoveries of Mn2+, Mg2+, and NH4+ ions exceeded 80%, 99%, and 90%, respectively. In addition, high-purity Mn3O4 with an Mn content of 71.61% and struvite were produced. This process represents a win-win strategy that facilitates the hazard-free treatment of EMR while simultaneously recovering valuable Mn2+, Mg2+, and NH4+ resources from waste. Thus, this study provides a novel approach to the hazard-free and resourceful management of solid waste. Environmental implicationElectrolytic manganese residue (EMR), a solid waste generated during electrolytic manganese production, poses significant environmental risks due to its soluble heavy metals and ammonia nitrogen content. Efforts have been made to address this issue, but there has been no mature industrial application due to cost or processing capacity constraints. In this work, solvent extraction was first used to enrich Mn2+ from EMR leachate, and a novel α‑hydroxy‑2‑ethylhexyl phosphinic acid was used as extractant. High purity Mn3O4 and struvite was synthesized through this process. The win‑win strategy offers a novel approach for the hazard‑free and resourceful utilization of solid waste.

Efficient separation of Cd2+ and Pb2+ by Tetradesmus obliquus: Insights from cultivation conditions with competitive adsorption modeling

Microalgae serve as efficient biosorbents for the removal of heavy metals. This study investigates the adsorption and desorption behavior of Tetradesmus obliquus FACHB-14 (T. obliquus) under various culture conditions. Glucose cultivation enhances adsorption, with Pb2+ exhibiting higher capacity than Cd2+, reaching a maximum of 80.24 mg/g at an initial heavy metal ion concentration of 64 mg/L. Kinetic modeling favors the pseudo-second-order kinetics. The Langmuir model is more suitable for describing the adsorption process of Cd2+ in BG11 and Pb2+ in glucose, with maximum adsorption capacities of 6.48 mg/g and 86.29 mg/g, respectively. The Temkin model is more suitable for describing the adsorption process of Pb2+ in BG11 and Cd2+ in glucose. Competitive adsorption reduces the maximum capacity by 42.60 % for Cd2+ and 55.61 % for Pb2+. The Extended Freundlich model fits competitive behavior. Analysis reveals increased extracellular polymer secretion under glucose conditions, which aids adsorption. Na2EDTA achieves up to 97.37 % recovery of heavy metal ions. Overall, T. obliquus cultured with glucose shows promise for heavy metal removal, especially in mixed systems.