High Adsorption Efficiency Research Articles

Construction of −SO3H and Zn2+ dual active sites over silica aerogel for NH3 adsorption: Collaborative efficiency enhancement performance and mechanism

The inherently corrosive and explosive nature of ammonia presents significant environmental and health hazards, highlighting the critical challenge of developing high-efficiency adsorbents for its removal. In this study, a dual-active site-modified silica aerogel containing Brønsted acid (−SO3H) and metal ions (Zn2+) was synthesized using both sol–gel and physical deposition methods for ammonia adsorbent. The optimally modified 3SO3H@SA aerogel displayed an adsorption capacity of 2.38 mmol·g−1. The incorporation of nanosized Zn2+ active sites boosted this capacity to 5.14 mmol·g−1, making a 210 % enhancement over the unmodified aerogel. Kinetic and NH3-TPD analyses underscored the increasing importance of chemical adsorption with the rise in active site abundance. Quantum chemical simulations elucidated the molecular-level adsorption mechanism, corroborating experimental results. The synergy between metal ions and acidic functionalities in this dual-modified aerogel demonstrates its efficacy and potential in NH3 adsorption applications, offering convincing insights for the development of high-capacity ammonia adsorbents.

Petroleum residue-based ultrathin-wall graphitized mesoporous carbon and its high-efficiency adsorption mechanism

Creating petroleum residue-based new functional materials are vital for the sustainable development of petroleum residues. This study developed a method to prepare a petroleum residue-based ultrathin-wall graphitized mesoporous carbon (PGMC) with high specific surface area by the carbonization of a composite of the petroleum residue uniformly mixed with aluminium isopropoxide. Results show that the PGMC possesses a highly fluffy ultrathin-wall mesoporous structure with a high degree of graphitization. It had a high specific surface area of 1174 m2 g−1 with a high pore volume of 4.57 cm3 g−1 and a narrow pore size distribution at 8.09 nm. These unique features endow the PGMC with excellent adsorption properties for Congo red, Malachite green, and Methylene blue removal. The experimental data were better described with Freundlich isotherm and Quasi-second-order kinetic models. Thermodynamic analysis indicated a spontaneous and endothermic adsorption process. The adsorption mechanisms proposed that pore-filling effect, π-π conjugation, and electrostatic interaction were the main interactions between the PGMC and dyestuff, followed by functional groups and hydrogen bonding. Moreover, the PGMC could maintain good adsorption rates after five cycles, proving that it is an effective adsorbent with good adsorption ability and cycling stability.

External surface hydrophilic 3D-POSS-COF@GDL for the direct adsorption of bisphenols in milk samples

In case of organic frameworks (COFs) as adsorbents in the pretreatment of complex food matrices, challenges such as poor dispersion and non-specific adsorption of interfering macromolecules like proteins are often encountered. To address this issue, this work prepared a three-dimensional covalent organic framework (3D-COF) with a novel bcu topology based on polyhedral oligomeric silsesquioxane (POSS). Subsequently, gluconolactone (GDL) was modified onto the external surface of the material via the reaction with the exposed reactive residues. The resulting POSS-COF@GDL adsorbent has an enhanced hydrophilicity in the external surface, thereby significantly improves the dispersion of materials in aqueous solution and reduces the adsorption ability toward protein. Whereas, the inner of material retains hydrophobic pores that exhibit high adsorption efficiency to small hydrophobic molecules. Compared with the traditional pretreatment methods, POSS-COF@GDL can directly extract bisphenols (BPs) in milk samples without any additional treatment. The established sample pretreatment method is coupled with high-performance liquid chromatography-ultraviolet detection (HPLC-UV), resulting in recoveries of 71.8 to 93.6%, intra- and inter-day relative standard deviations (RSDs) of <8.3%, and limits of detection (LODs) of 0.042–0.16 ng∙mL−1 for four BPs.

Evaluation and optimization of six adsorbents for removal of tetracycline from swine wastewater: Experiments and response surface analysis

The removal of tetracycline antibiotics using adsorbents is becoming an environmentally friendly and cost-effective method. This study systematically analyzed the stability, structure, morphology, and chemical properties of various adsorbents. Batch adsorption experiments (pH, time, temperature, tetracycline concentration, and adsorbent dosage) were conducted to compare the adsorption capacity of the six adsorbents (biochar, activated carbon, montmorillonite, zeolite, chitosan, and polymerized aluminum chloride) for tetracycline removal. The results indicated that montmorillonite had the highest adsorption efficiency, followed by biochar, with chitosan showing the lowest efficiency. At an adsorbent dose of 25 g/L and an initial tetracycline concentration of 120 mg/L, the removal rates of tetracycline by montmorillonite, biochar, and chitosan were 97.6%, 69.3%, and 12.2%, respectively. Furthermore, the removal rate of tetracycline by biochar, following the response surface methodology optimal mode, increased by 5.5%. The Elovich model was better suited to explain the adsorption process of tetracycline compared to the conventional pseudo-first kinetic model and second-order kinetic model. The isothermal adsorption model suggested that both chemisorption and physisorption occurred in all removal processes, in which chemisorption dominated. Tetracycline was efficiently adsorbed through the combined effects of pore filling, electrostatic attraction, π-π interactions, and complexation reactions of surface functional groups. Additionally, montmorillonite demonstrated superior performance as an adsorbent for tetracycline removal from swine wastewater compared to the other adsorbents studied.

Synthesis of nitrogen enriched porous carbon sponge with the assistance of hard template and physical activation for highly efficient CO2 adsorption

Porous carbons are attractive materials for CO2 capture due to their unique properties. In the current work, N-doped porous carbon sponge (NDPCS) was synthesized with a combined hard template and CO2 activation method, and the applications in CO2 adsorption were also studied. Correlations between synthesis parameters and the product’s morphology were revealed, and effects of the activation conditions on N content and textural properties were analyzed. CO2 adsorption performances of the NDPCS were also thoroughly investigated. The influences of various physicochemical properties on adsorption properties were discussed. CO2 uptake at 25 °C and 1 bar was relatively low (2.16–2.50 mmol/g). However, NDPCS-3–3 showed impressively high adsorption efficiency of 1.63 (mmol/g)/(100 m2/g), much better than some of the best performing samples from reported works. The superior performances were attributed to the combined effects of abundant ultramicropores and enriched N-doping. The current work showed that the NDPCS had great potential for applications in CO2 capture.

Machine-Learning-Assisted Material Discovery of Pyridine-Based Polymers for Efficient Removal of ReO4.

Efficient capture of 99TcO4- is the focus in nuclear waste management. For laboratory operation, ReO4- is used as a nonradioactive alternative to 99TcO4- to develop high-performance adsorbents for the treatment. However, the traditional design of new adsorbents is primarily driven by the chemical intuition of scientists and experimental methods, which are inefficient. Herein, a machine learning (ML)-assisted material genome approach (MGA) is proposed to precisely design high-efficiency adsorbents. ML models were developed to accurately predict adsorption capacity from adsorbent structures and solvent environment, thus predicting and screening the 2450 virtual pyridine polymers obtained by MGA, and it was found that halogen functionalization can enhance its adsorption efficiency. Two halogenated functional pyridine polymers (F-C-CTF and Cl-C-CTF) predicted by this approach were synthesized that exhibited excellent acid/alkali resistance and selectivity for ReO4-. The adsorption capacity reached 940.13 (F-C-CTF) and 732.74 mg g-1 (Cl-C-CTF), which were better than those of most reported adsorbents. The adsorption mechanism is comprehensively elucidated by experiment and density functional theory calculation, showing that halogen functionalization can form halogen-bonding interactions with 99TcO4-, which further justified the theoretical plausibility of the screening results. Our findings demonstrate that ML-assisted MGA represents a paradigm shift for next-generation adsorbent design.

Fabrication of Porous Adsorbents Templated from Capillary Foam Stabilized with Chlorella for Highly Efficient Removal of Cationic Dyes.

The thermodynamic instability of conventional aqueous foam-stabilized surfactants is a critical bottleneck in the construction of porous materials. Herein, a novel strategy is proposed for preparing a capillary foam based on Chlorella and utilizing it as a template for constructing porous materials with high-efficiency adsorption. The capillary foam was stabilized by Chlorella particles enclosed within a gel network of oil bridges connecting the particles (capillary suspension). Chlorella particles, which act as stable particles, form oil bridges and are distributed at the phase interface of the capillary foam. These particles exhibited resistance to shear forces, allowing the formation of a long-term stable capillary foam. Using this foam as a template, a porous material with outstanding adsorption performance for Methylene Blue (MB) and Brilliant Green (BG) dyes was successfully constructed. Additionally, the material exhibited a sustained high adsorption performance even after five thermal regeneration-adsorption cycles. In conclusion, this study presents a green and straightforward method for constructing capillary foams with high stability, which is a promising approach for developing porous materials with exceptional adsorption and regeneration properties for dyes.

Enhanced adsorption of Congo red dye by CS/PEG/ZnO composite hydrogel: Synthesis, characterization, and performance evaluation

Hydrogels are 3D interconnected network polymer chains that are hydrophilic, swell in water and imbibe a significant amount of water. When hydrogel absorb water, dye molecules transfer to their surface, aiding adsorption. Adsorption is efficient, cheap, and versatile technique to remove dye from aqueous media. In this study, high-performance adsorbents from chitosan/polyethylene glycol (CS/PEG) hydrogel cross-linked with intermolecular H-bonds and chitosan/polyethylene glycol/ZnO (CS/PEG/ZnO) composite hydrogel cross-linked with Zn2+ were developed by an instantaneous gelation method. The prepared composite hydrogels were characterized by Fourier transform infrared (FTIR) spectroscopy, Scanning electron microscopy (SEM), X-ray diffraction (XRD), thermo-gravimetric analysis (TGA), transmission electron microscopy (TEM) and Zeta-sizer. The developed composite hydrogels effectively adsorbed Congo red (CR) dye from aqueous media. CR adsorption efficiency using adsorbent dosage, contact time, pH and temperature factors were conducted by batch adsorption experiments. The obtained results for CR adsorption equilibrium were compatible with the Langmuir model with maximum adsorption capacity (qmax) of 212.76 mg/g for CS/PEG and 256.41 mg/g for CS/PEG/ZnO composite hydrogel. The qmax was measured at pH 3 and 25 min and kinetic study confirmed that pseudo 2nd order kinetic model was best followed. Thermodynamic study indicated that the nature of the adsorption phenomena was physical, endothermic and spontaneous. The high adsorption efficiency is mainly ascribed to the protonation of –NH2 groups present in CS/PEG and CS/PEG/ZnO composite hydrogels which enhanced its electropositivity. Hydrogen bond formation and electrostatic attraction among adsorbent and dye govern the adsorption mechanism. It can be concluded that CS/PEG hydrogel and CS/PEG/ZnO composite hydrogels could be considered as efficient, beneficial and potential adsorbents for environmental remediation.

Enhanced Removal of Cd(II) Ions from Aqueous Media via Adsorption on Facilely Synthesized Copper Ferrite Nanoparticles.

In this study, magnetic copper ferrite (CuFe2O4) nanoparticles were synthesized via the Pechini sol-gel method and evaluated for the removal of Cd(II) ions from aqueous solutions. PF600 and PF800 refer to the samples that were synthesized at 600 °C and 800 °C, respectively. Comprehensive characterization using FTIR, XRD, FE-SEM, HR-TEM, and EDX confirmed the successful formation of CuFe2O4 spinel structures, with crystallite sizes of 22.64 nm (PF600) and 30.13 nm (PF800). FE-SEM analysis revealed particle diameters of 154.98 nm (PF600) and 230.05 nm (PF800), exhibiting spherical and irregular shapes. HR-TEM analysis further confirmed the presence of aggregated nanoparticles with average diameters of 52.26 nm (PF600) and 98.32 nm (PF800). The PF600 and PF800 nanoparticles exhibited exceptional adsorption capacities of 377.36 mg/g and 322.58 mg/g, respectively, significantly outperforming many materials reported in the literature. Adsorption followed the Langmuir isotherm model and pseudo-second-order kinetics, indicating monolayer adsorption and strong physisorption. The process was spontaneous, exothermic, and predominantly physical. Reusability tests demonstrated high adsorption efficiency across multiple cycles when desorbed with a 0.5 M ethylenediaminetetraacetic acid (EDTA) solution, emphasizing the practical applicability of these nanoparticles. The inherent magnetic properties of CuFe2O4 facilitated easy separation from the aqueous medium using a magnet, enabling efficient and cost-effective recovery of the adsorbent. These findings highlight the potential of CuFe2O4 nanoparticles, particularly PF600, for the effective and sustainable removal of Cd(II) ions from water.

Efficient removal of diclofenac sodium from aqueous environments by magnetic ionic covalent organic frameworks based on polydopamine: Adsorption performance and mechanism study

In recent years, ion covalent organic frameworks (iCOFs) have shown excellent adsorption performance in the removal of non-steroidal anti-inflammatory drugs (NSAIDs), but powdered iCOFs are faced with problems in separation and recovering from solution and are prone to environmental pollution. In this work, polydopamine (PDA) was used as the mediated coating, Fe3O4 as the magnetic nucleus, and iCOFs consisting of benzene-1,3,5-triscarbaldehyde (BT) and 1,3-diaminoguanidine hydrochloride (DGCl) as organic ligands were in-situ grown on the surface of the PDA coating by Schiff base reaction, resulting in a magnetic nanocomposite (Fe3O4@PDA@BT-DGCl) with a coral-like structure. The adsorption kinetics and adsorption isotherms showed that the adsorption behavior of diclofenac sodium (DS) on Fe3O4@PDA@BT-DGCl followed the pseudo-second-order kinetic model and Langmuir model, and the maximum adsorption capacity could reach up to 420.17 mg g−1 (25 ℃, pH 5). The adsorption of DS on Fe3O4@PDA@BT-DGCl was dominated by electrostatic interactions, along with hydrogen bonding, π-π interactions, and ion exchange, according to the analysis of the adsorption mechanism. The Fe3O4@PDA@BT-DGCl consistently maintained high adsorption efficiency after six adsorption–desorption cycles, making it an efficient adsorbent for the removal of NSAIDs in complex water environments.

Self-supporting and hierarchical porous membrane of bacterial nanocellulose@metal-organic framework for ultra-high adsorption of Congo red

The widespread use of synthetic dyes has serious implications for both the environment and human health. Therefore, there is an urgent need for the development of novel, high-efficiency adsorbents for these dyes. In this study, a Zirconium-based metal-organic framework (MOF) with controllable morphology was in-situ grown on bacterial nanocellulose (BC) via a solvothermal method. The resulting BC@MOF composite nanofibers have a high specific surface area of 651 m2/g and can be assembled into a self-supported porous membrane (BMMCa) through vacuum filtration with the assistance of calcium ions. The addition of Ca(II) significantly enhanced the mechanical properties of the membrane through dispersion effect and electrostatic interactions, as well as enhancing its adsorption performance through the salting-out effect. The BMMCa membrane, with its hierarchical porous structure and high flux, exhibits high selectivity for Congo red (CR) with an ultra-high adsorption capacity of 3518.6 mg/g. Furthermore, the self-supporting membrane achieved rapid and convenient removal of CR through circulating filtration adsorption. The adsorption mechanism and selectivity were verified through the molecular dynamics simulation calculations by Materials Studio (MS) software. This membrane-based adsorbent, with its ultra-high adsorption capacity, good selectivity, and recycling ability, has great potential for practical wastewater treatment applications.

Adsorptive removal of microplastics from aquatic environments using coal gasification slag-based adsorbent in a liquid–solid fluidized bed

Microplastics (MPs) are emerging pollutants in aquatic environments that threaten ecological health. This study investigated the adsorption process and mechanism of a coal gasification slag-based adsorbent in a liquid–solid fluidized bed to remove MPs from an aquatic environment. The results showed that the coal gasification slag-based adsorbent had high MP adsorptive removal efficiency of up to 1400 mg/g and adsorption-removal efficiency of 99.2 %. The adsorption process was mainly dominated by electrostatic attraction, π-π absorption, and surface complexation, supplemented by partial physical adsorption. The adsorbent dosage mo was the dominant factor affecting the adsorption performance of the liquid–solid fluidized bed for the continuous adsorption of MPs, followed by the initial MP concentration co and ascending water velocity vt. At a suitable combination of operating parameters (co = 250 mg/L; mo = 2.5 g; vt = 0.11 m/s), the adsorption saturation level of the liquid–solid fluidized bed reached 0.95, which was higher than that of the traditional fixed bed (0.91), indicating good MP adsorption performance. This study provides a new technical approach for MP removal from aquatic environments that is conducive to the industrial application of fluidized beds in the field of wastewater treatment.

Application of Modified Polyether Sulfone Microspheres in Hyperbilirubinemia

To design and prepare a high efficiency bilirubin adsorbent with good mechanical properties and biocompatibility. In this study, quaternary ammonium pyridine was designed and synthesized, and then modified polyether sulfone microspheres, or PES/p(4-VP-co-N-VP)@6 microspheres, were prepared by phase conversion and electrostatic spraying. The morphology of the polymer components and the microspheres were studied by means of nuclear magnetic resonance (NMR) spectroscopy and scanning electron microscopy. The basic properties of the microspheres and their bilirubin adsorption efficiency were tested, and the adsorption mechanism was further explored. Blood cell counts and the clotting time of the microspheres were also measured. The diameter of the modified polyether sulfone microspheres prepared in the study was approximately 700-800 μm. Compared with the original PES microspheres, the surface and internal structure of PES/p(4-VP-co-N-VP)@6 microspheres did not change significantly, and they also had a loose porous structure, with some micropores scattered around in addition to irregular large pores. Compared with the control group, the bilirubin removal effect of the modified microspheres was (94.91±0.73)% after static adsorption in bilirubin PBS buffer solution for 180 min, with the difference being statistically significant (P<0.0001). According to the findings for the clotting time, the activated partial thromboplastin time (APTT) of the blank plasma group, the control PES group, and the modified PES microsphere group were (27.57±1.25) s, (28.47±0.45) s, and (30.4±0.872) s, respectively, and the difference between the experimental group and the other two groups was statistically significant (P<0.01, P<0.05). There was no significant change in red blood cell and white blood cell counts. The microspheres prepared in the study have high efficiency in bilirubin adsorption, excellent mechanical properties and thermal stability, and good blood biocompatibility, and are expected to be used in the clinical treatment of patients with liver failure.

Chelator-impregnated polydimethylsiloxane beads for the separation of medical radionuclides

Chelator-impregnated resins have been studied earlier for the chemical separation of elements in aqueous solutions, but issues with their chemical stability have limited their use in the separation of (medical) radionuclides from their respective irradiated targets. We developed a polydimethylsiloxane (PDMS)-based chelator-impregnated resin that showed a high chemical stability against leaching. Several different chelators were tested in this study. After impregnation of the PDMS beads with the di-2-ethylhexylphosphoric acid (D2EHPA) chelator, an in-flow separation study with various radionuclides (Y-90, La-140, and Ac-225) was conducted. These three radionuclides have potential use in nuclear medicine and a production route through irradiation of Sr-, Ba-, and Ra-targets respectively, necessitating their chemical separation. The D2EHPA-impregnated beads achieved high adsorption efficiencies of 99.89% ± 0.14%, 99.50% ± 0.10%, and 98.51% ± 0.25%, for Y-90, La-140, and Ac-225, respectively, while co-adsorption of minor amounts (<3%) of the targets were reported. These results, together with the high chemical stability of the PDMS-based resin, highlight the potential of chelator-impregnated resins in the rapidly growing field of (medical) radionuclide production.

Development and characterization of novel CS-ZnO-Alg polyelectrolyte complex for enhanced removal of Cd(II), Cu(II), and Ni(II) from simulated paint industrial wastewater

In this study, we developed and characterized a novel chitosan-alginate-based polyelectrolyte complex impregnated with zinc oxide nanoparticles (CS-ZnO-Alg PEC) for the enhanced removal of Cd(II), Cu(II), and Ni(II) from simulated paint industrial wastewater. The prepared PEC was characterized by X-ray Diffraction (XRD), Fourier-Transform Infrared (FTIR) Spectroscopy, Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM/EDS), X-ray Photoelectron Spectroscopy (XPS), Brunauer-Emmett-Teller (BET), and Thermogravimetric analysis/Differential Thermal Analysis (TGA/DTA). The equilibrium data for said metal ions was best appropriated by Freundlich isotherm with maximum adsorption capacity of 217.72 mg/g for Cd(II), 130.41 mg/g Cu(II), and 159.06 mg/g for Ni(II), illustrating the multilayer adsorption of metal ions on the heterogeneous surface sites of the adsorbent. The kinetics of all three metal ions adsorption process onto discussed PEC was consistent with pseudo-second-order model. The thermodynamics results illustrate exothermic and spontaneous processes for Cd(II) (ΔH° = −3.57 KJ/mol, ΔS° = 0.009 KJ/mol*K, ΔG° = −6.42 to −6.61 KJ/mol) and Cu(II) (ΔH° = −3.32 KJ/mol, ΔS° = 0.006 KJ/mol*K, ΔG° = −5.25 to −5.37 KJ/mol), and spontaneous but less favorable adsorption for Ni(II) (ΔH° = −0.82 KJ/mol, ΔS° = −0.001 KJ/mol*K, ΔG° = −0.39 to −0.36 KJ/mol). Notably, the PEC could be easily recycled and regenerated, maintaining adsorption efficiency after five cycles. Overall, the CS-ZnO-Alg PEC, due to its amphoteric nature, high adsorption efficiency, cost-effectiveness, excellent recyclability, and biodegradability, could be a promising adsorbent for paint industrial wastewater.

Efficacious sensing and elimination of iron ions from aqueous medium by polyethylenimine functionalized carbon dot

In the present work, Iron (Fe) ions are detected and removed from an aqueous medium using a green emissive polyethylenimine functionalized carbon dots (GPC), which are produced hydrothermally and have high adsorption efficiency and sensitivity. As prepared, GPC uses an adsorption approach to remove iron ions and a Turn-Off mechanism to detect iron ions. A UV-Vis and photoluminescence spectroscopy are used to evaluate the results of several experiments, including those involving the interference of other ions, changing the concentration of metal ions, pH, reaction time, and the dosage of adsorbent in the sensor, in an attempt to achieve high sensitivity (with a lower limit of detection of 0.08 ppm) and high adsorption efficiency of approximately 98 % (8 µM of Fe and 1 ppm of GPC) towards iron ions. The isotherm and kinetic analyses of adsorption show that pseudo-second-order kinetics and Freundlich isotherm suits the experimental data better. With a removal percentage of roughly 89 percent after three cycles, desorption analysis highlights its regeneration efficiency. The mechanism of adsorption and quenching are extensively investigated; The static and dynamic quenching mechanisms are supported by high static constant value of approximately 23.5 ×103 M and the lifetime decay declination of 2.42 ns, respectively. Zeta potential measurements and XPS analysis are used to examine the electrostatic interaction between GPC and Fe in the adsorption mechanism. Ultimately, the prepared material's contentment results illustrate its potential for practical applicability with five actual water samples.

Selective extraction of captafol from blood and river water samples using molecularly imprinted polymers

In this study, the captafol molecularly imprinted polymers were first prepared using the precipitation polymerization method, using captafol as the template molecule and acrylamide (Am) as the functional monomer. The synthesized polymers have spherical particles with a loose, porous surface, as determined through scanning electron microscopy. The polymer was analyzed using BET, Thermogravimetric Analysis (TGA), Scanning Electron Microscopy (SEM), and Fourier Transform Infrared Spectroscopy (FTIR). The polymers demonstrated a high adsorption efficiency of up to 90 % and specific recognition ability towards captafol, based on the results of the dynamic and static adsorption assays. The factors affecting MIPs’ binding efficiency were carefully optimized. Studies were established to analyze captafol in water and human blood serum samples under optimal conditions. Through adsorption kinetics, adsorption isotherms, and selectivity tests, this suggested approach demonstrated good MIP adsorption characteristics for captafol. The resulting Cap-MIPs showed notable selectivity for captafol as compared to folpet, high adsorption capacity (90 %), and good reusability, with the ability to reach adsorption equilibrium in less than 60 min. The results showed that the Cap-MIPs strategy exhibited high selectivity, good consistency, and high sensitivity, making it an efficient way to enrich and recognize captafol in a complex blood serum matrix.

Role of Co and Ni ferrites in the fabrication of Saccharum officinarum bioadsorbents for removing As(III)

Removal of arsenic from drinking water is one of the most significant worldwide concerns. Adsorptive removal of arsenic is highly practical and efficient among the various methods. The green synthesis using sugarcane extract was eco-friendly, and cost-effective and resulted in adsorbents having magnetic behavior and a high capacity for arsenic. In the present study, activated carbon (ACs) of sugarcane and its surface, functionalized with nickel ferrite (AC/NFO) and cobalt ferrite (AC/CFO) were used as biosorbents for the removal of As(III) from aqueous medium. The functionalization was undertaken in a controlled hydrothermal method using Saccharum officinarum (sugarcane) extract as a green source. The morphology, functionality, thermal stability, structure, magnetic behavior, surface area and porosity of adsorbents were confirmed by SEM, FTIR, TGA, XRD, VSM, BJH and AFM. The sorption behavior was determined with the effect of pH, time, concentration, temperature and dose. Pseudo-second order and Langmuir models were found suitable to validate the sorption data. Thermodynamics of the sorption process and the desorption studies suggested that the governing mechanism is chemisorption. The adsorption capacities for AC2, AC2C2 and AC2N2 were 961 µg/g, 1103 µg/g and 1000 µg/g respectively. Among the studied samples, AC2C2 was found as a potential candidate due to its high adsorptive efficiency of 97 % for As(III).

Sulfonated modified rice straw for selective adsorption and extraction of gold ions from highly acidic solutions

In this study, a novel and cost-effective adsorbent, sulfonated modified rice straw (SRS), was developed for the selective adsorption and extraction of gold ions from acidic solutions. The SRS was synthesized through a simple and environmentally friendly sulfonation crosslinking modification process, leveraging the abundant and low-cost agricultural waste, rice straw. The surface of SRS was functionalized with sulfonic acid groups, which, under acidic conditions, exhibited positive charges that facilitated the electrostatic adsorption of negatively charged AuCl4- ions. Concurrently, the hydroxyl groups within the adsorbent structure donated electrons, reducing the adsorbed AuCl4- ions to metallic gold. SRS showed excellent adsorption selectivity and high adsorption efficiency for gold under different experimental conditions. The adsorption kinetics and isotherms of SRS for gold were well-described by pseudo-second-order and Langmuir models, respectively, indicating a chemisorption process predominantly governed by the electronic interactions and active sites on the SRS surface. The maximum adsorption capacity of SRS for gold was determined to be 88.81 mg/g in a 1 M HCl medium, showing its superior performance compared to other reported adsorbents under similar acidic conditions. An economic evaluation revealed that the SRS-based gold recovery process is financially viable, with a potential net profit of $71 per cubic meter of degoldized solution processed. Sulfonated modified rice straw adsorbent presents a promising and sustainable approach for the selective recovery of gold ions from complex acidic solutions, offering significant potential for application in the gold extraction industry.

Indigenous microbial influence on REE enrichment and fractionation in South China weathering crusts: Insights from experimental simulations

The activity of microorganism plays an important role on the enrichment, migration and fractionation of rare earth elements (REEs) in the supergene environment. To investigate the characteristics of indigenous microorganisms on the enrichment and fractionation of REEs, we studied the adsorption efficiencies of REEs by 30 indigenous microbial strains that were isolated and cultured from the weathering profile of a regolith-hosted REE deposit in South China. Most microbial strains exhibited high adsorption efficiencies for REEs, ranging from 2.3 to 42.9 mg g−1. Notably, the taxonomic classification of microorganisms significantly influenced the adsorption selectivity. Gram-positive bacteria exhibited a pronounced enrichment of the heavy REEs, while gram-negative bacteria showed no obvious adsorption preference. The tetrad effects were observed in REE adsorption patterns of gram-negative bacteria and fungi; however, fungi demonstrated a much higher affinity for light and medium REEs. Chemically modified microbial cells were employed to investigate the adsorption mechanism, revealing that distinct functional groups of microbial cells corresponded to the adsorption preference of microorganisms towards REE. Carboxyl and phosphate groups contributed to a relatively high adsorption capacity for light REEs and heavy REEs, respectively. The findings of our study suggest that the distinct composition of microbial groups may exert a significant influence on the biogeochemical cycle of REE in weathering profiles.