Selective Adsorption Capacity Research Articles

Untwisting Strategy of MOF Nanosheets in Ultrathin Film Membrane for High Molecular Separation Performance.

Oriented 2D metal-organic framework (MOF) membranes hold considerable promise for industrial separation processes. Nevertheless, the lattice misalignment caused by the twisted stacking of 2D nanosheets reduces the in-plane pore size and exerts a significant impact on the membrane separation performance. Precisely regulating the stacking pattern of oriented 2D MOF membranes remains a significant challenge. Here, a scalable scrape-coating technique supplemented by a vapor untwisting strategy is proposed to directly construct non-twisted and ultrathin Zr-BTB membranes (Zr-BTB-M) on polyvinylidene fluoride (PVDF) substrates. The Zr-BTB nanosheets are induced to undergo lattice reorganization during the coating process, resulting in highly overlapped lattices and the largest in-plane pore channels. The exceptional butyl acetate selective adsorption capacity of non-twisted Zr-BTB, combined with its provision of highly ordered vertical penetrating pathways, significantly enhances molecular transport. After facile polydimethylsiloxane (PDMS) coating, the pervaporation separation index of the PDMS/Zr-BTB-M/PVDF membrane is found to be 9.74 times higher than that of conventional PDMS/PVDF membranes, paving the way for innovative, high-efficiency, energy-saving membrane separation technologies.

Selective extraction and determination of chlorpyrifos residues from aqueous samples using biochar-functionalized molecularly imprinted polymer combined with high-performance liquid chromatography.

The concentration of chlorpyrifos (CPF) in aqueous samples was determined using a novel molecularly imprinted dispersive solid-phase extraction (MISPE) approach that was presented in this research. Using a non-covalent molecular imprinting technique, a biochar (BC)-functionalized molecularly imprinted polymers (MIPs) (BC-MIPs) was created. These MIPs were used in dispersive solid-phase extraction (DSPE) in conjunction with high-performance liquid chromatography with photodiode array detection (HPLC-PDA) to detect CPF in aqueous samples with high sensitivity. Using methacrylic acid (MAA) as the monomer and ethylene glycol dimethacrylate (EGDMA) as the cross-linker, BC-MIPs were created using CPF as a template. By using the suggested dispersive solid-phase extraction (DSPE) approach, the efficiency of the synthesized BC-MIPs granules was evaluated. Analytical performance of the devised DSPE-HPLC-PDA technique was assessed under optimal settings. The optimized parameters included extraction time, aqueous sample pH, desorption time and desorption reagents. Compared with the traditional method, the established method has better selective adsorption capacity, reusability and sensitivity for CPF. The suggested method presented that limit of detection and limit of quantification were 1.0 ng/mL and 4.0 ng/mL, along with excellent linear range (4.0-1500 ng/mL) with coefficients of determination (R2=0.9982). The established method was successfully used to determination CPF in aqueous samples from the Baisha River in Qingdao, with the advantages of accuracy (recoveries: 81.2 %-103.6 %, RSDs≤9.2 %), speed (CPF-BC-MIPs-DSPE time: 75 min; HPLC-PDA time: 12 min), selectivity (imprinting factor: 4.24), and economy (50 mg of adsorbent synthesized using cheap straw and 1 mL of solvents), which partially conform to the current advanced principle of "3S+2A" in analytical chemistry. The BC-MIPs granules shown potential for CPF preconcentration in complicated samples and were effective carriers for the selective adsorption of CPF.

Preparation of Porous Novel QuEChERS Adsorbent ZIF‐67/PAA/PES Composite Microspheres and Their Application for Rapid Adsorption of Triphenylmethane Dyes in Wastewater and Fish

ABSTRACTTriphenylmethane dyes have a wide range of applications in textiles, pharmaceuticals, food, and other fields. Malachite green (MG), fuchsin acid (FA), and crystalline violet (CV) were typical representatives of triphenylmethane dyes, and they are carcinogenic and mutagenic to aquatic organisms and environment. However, they need to be separated and enriched for their accurate quantification due to their low content. Therefore, it is important to develop a rapid and accurate enrichment method to monitor these dyes in aquatic systems for human health. In this paper, a novel QuEChERS adsorbent porous ZIF67/PAA/PES composite microspheres were prepared and applied for the rapid adsorption of triphenylmethane dyes in wastewater and fish samples, which improved the adsorption capacity and the analytical sensitivity of the targets. The experimental results demonstrated that the porous ZIF‐67/PAA/PES composite microspheres exhibited excellent selective adsorption capacity of MG, FA, and CV, and after six adsorption–desorption cycles, the material adsorption amount can reach more than 90% of its original adsorption amount in wastewater. In addition, the porous ZIF67/PAA/PES composite microspheres were applied as QuEChERS adsorbents for the enrichment of MG and CV dyes in fish, and the adsorption rates of the dyes were 99.11% and 99.03%, with the RSDs of 1.58% and 1.27%, respectively. The limits of detection were 0.0093 and 0.0127 mg/L for MG and CV. Through the Langmuir adsorption isotherm models to predict the MG, FA, and CV of the maximum adsorption capacity were 5417.3622, 2119.9011, and 1654.1026 mg/g, respectively. Thus, the novel porous ZIF67/PAA/PES composite microspheres are more advantageous as QuEChERS adsorbents for sample pre‐treatment and have very important research significance.

Preparation of High‐Selectivity Li+ Adsorbents Based on Bauxite via Liquid‐Phase Alkaline Thermal Activation

ABSTRACTBauxite, as the main aluminium‐bearing mineral in China, is a crucial resource for the industrial production of aluminium and aluminium‐related products. In this study, bauxite‐based aluminium composite Li+ adsorbents were prepared using a liquid‐phase alkaline thermal activation—acid in situ method. The effects of various factors on Li+ adsorption from brine were investigated through single‐factor experiments. Multiple techniques, such as scanning electron microscopy (SEM), energy dispersive x‐ray spectroscopy (EDS), x‐ray diffraction (XRD), Brunauer–Emmett–Teller (BET) method, Fourier transform infrared spectroscopy (FT‐IR), and x‐ray photoelectron spectroscopy (XPS), were employed to characterise and analyse the microstructure, pore size distribution, chemical element distribution, and mineral structure of the adsorbents. In addition, the changes in bauxite structure and properties before and after functionalization were investigated. Results indicate that the adsorption capacity of LATA‐AIS‐LDH‐BX adsorbent prepared by the acid in situ method reached 1.15 mg/g at pH = 7; the adsorption capacity of LATA‐Al‐LDH‐BX adsorbent prepared by the aluminium salt conversion method reached 2.16 mg/g. The adsorption behaviour of both adsorbents followed the pseudo‐second‐order kinetic model and the Langmuir model. In the presence of interfering ions (Na+, K+, SO24+, Mg2+), the composite adsorbents showcased strong selective adsorption capacity for Li+. After five cycles of adsorption–desorption, the adsorption rates decreased by 12.19% and 11.48%, respectively, demonstrating good recycling stability. Furthermore, the Li+ adsorption capacities in salt lake brine reached 0.82 mg/g and 1.48 mg/g, indicating promising potential for industrial application.

Application of bifunctional monomer surface MIP with MOFs nanocomposite for efficient trapping and analysis of luteolin in compound Anoectochilus roxburghii (Wall.) Lindl. oral liquid

Luteolin is one of the bioactive components from the compound Anoectochilus roxburghii (Wall.) Lindl. oral liquid (CAROL), which was reported to have excellent hepatoprotective and anti-inflammatory activities. However, the enrichment and quantitation of luteolin from CAROL is challenging due to the low content and complex aqueous matrix. In this study, a bifunctional monomer surface molecularly imprinted polymer (MIP) with metal–organic frameworks (MOFs) as cores was prepared for the selective adsorption of luteolin from the aqueous system CAROL. Compared with conventional MIPs, this unique nanocomposite adsorbent (MOF@MIPs) has the advantages of short kinetic equilibrium time, good selectivity, and high adsorption capacity in aqueous solution. The theoretical maximum adsorption capacity of MOF@MIPs for luteolin was 36.99 mg/g. After adsorption enrichment of luteolin from CAROL using MOF@MIPs, liquid chromatography–tandem mass spectrometry was applied to analyze the target. The corresponding linearity range for analyte was 10–6000 ng/mL with good linearity (R2 =0.9992), and the added recoveries varied from 85.70 % to 99.25 %. The present method has been successfully employed for the analysis of luteolin in five different batches of CAROL. Notably, we found no significant difference in the content of luteolin between these batches, which proved that the composition was stable between batches. The novel structure MIPs are suitable for the specific recognition of template molecules in aqueous solution. Therefore, this study provides a technical reference for the special identification and determination of trace components in complex samples, while the novel MOF@MIP nanocomposite can also provide valuable references for the extraction and purification methods of specific substances in traditional Chinese medicine and expand the application environment of MIPs material.

Removal of Phosphate from Water by Iron/Calcium Oxide-Modified Biochar: Removal Mechanisms and Adsorption Modeling

Phosphorus (P) pollution is a leading cause of water eutrophication, and metal-modified biochar is an effective adsorbent with the ability to alter the migration capacity of phosphorus. This study uses bamboo as the raw material to prepare metal-modified biochar (ZFCO-BC) loaded with Fe and Ca under N2 conditions at 900 °C, and investigates its adsorption characteristics for phosphate. Batch experimental results show the adsorption capacity of the ZFCO-BC gradually increases (from 4.0 to 69.1 mg/g) as the initial phosphate concentration increases (from 2 to 900 mg/L), mainly through multilayer adsorption. Additionally, as the pH increases from 1 to 7, the adsorption capacity of the ZFCO-BC climbs to reach its maximum value of 48.4 mg/g with an initial phosphate concentration of 150 mg/L. At this pH, phosphate primarily exists as H2PO4− and HPO42−, which both readily react with Fe3+ and Ca2+ in the biochar. Furthermore, the addition of CO32−, HCO3−, NO3−, SO42−, F−, and Cl− each affect the removal rate of phosphate by less than 10%, indicating the ZFCO-BC has a highly efficient and selective phosphate adsorption capacity. A multi-column adsorption experiment designed to achieve long-term and efficient phosphorus removal treated 275.5 pore volumes (PVs) of water over 366 h. The cyclic adsorption–desorption experiment results show that 0.5 M NaOH can effectively leach phosphate from the ZFCO-BC. Observations at the molecular level from P K-edge XANES spectra confirm the removal of low-concentration phosphate is primarily dominated by electrostatic attraction, while the main removal mechanism for high-concentration phosphate is chemical precipitation. This study demonstrates that ZFCO-BC has broad application prospects for phosphate removal from wastewater and as a potential slow-release fertilizer in agriculture.

The top-down construction of cornstalk-based columns as self-adaptive bio-adsorbents for selective dye adsorption from wastewater

High chemical stability, biological toxicity, and chromaticity of synthetic dyes lead to the problems such as excessive oxidant dosage, microbial anaerobic retardation, and difficult photocatalytic degradation during their wastewater treatment. The technology of selective adsorption makes it possible to recycle or reuse dyes for the purpose of achieving low energy-consumptive and eco-benign strategy in dye effluent purification. Based on the inherent structure of corn stalk pith (CSP), we prepared carbohydrate columns (CSPC) and dimethyldiallylammonium chloride-CSPC (D-CSPC) via in-situ delignification followed by surface cationization. Our study illustrates that these adsorbents retain the original anisotropic three-dimensional structure of CSP, providing highly-developed channels and pores for efficient mass transfer. In cationic/anionic dye binary system, D-CSPC shows controllable selective adsorption capacity by changing its surface N+(CH3)2 density. The selectivity factor of D-CSPC for MO (methyl orange) and AR (alizarin red) increased from 0.13 to 6.17 and 0.17 to 4.73, respectively, as the cationization degree of CSPC was elevated. Both adsorbents have been also confirmed to be effectively recycled, while maintaining over 80% of the dye adsorption capability after five cycles. Moreover, the adsorbent demonstrated significant potential for practical industrial applications, as evidenced by its successful performance to treat the high ionic strength solution and simulated textile wastewater. The approach of current study provides a new, facile, and green-synthesis route toward the exploration of natural and biodegradable agricultural waste integrated into a simple process for the production of cheap, selective, and recyclable adsorbent.

Composite of Hydrolyzed PAN and β-Cyclodextrin Forms a Nanofiber Membrane with an Excellent Removal Effect on Various Cationic Dyes and Copper Ions.

The presence of dyes and heavy metals in wastewater represents a significant environmental and public health hazard, necessitating the development of efficient materials for their removal. In this study, we modified hydrolyzed polyacrylonitrile (PAN-H) and combined it with β-cyclodextrin (β-CD) by using an electrostatic spinning technique to fabricate composite nanofibrous membranes for water treatment applications. The resulting PAN-H/β-CD nanofiber membranes exhibit spindle-shaped fibers and porous structures with a high density of charged functional groups, which significantly enhance their selective adsorption capacity compared to pure PAN fibers. Furthermore, post-treatment with a sodium bicarbonate solution further improved this capacity, resulting in the membranes demonstrating a remarkable adsorption efficiency for cationic dyes. The adsorption process conformed to the Langmuir and pseudo-second-order kinetic models, with maximum adsorption capacities of 216.94 mg/g for methylene blue (MB), 471.59 mg/g for malachite green (MG), 299 mg/g for crystal violet (CV), and 43.95 mg/g for copper ions. The selective adsorption of these positively charged contaminants, particularly cationic dyes and metallic copper, indicates that PAN-H/β-CD membranes have significant potential for the treatment of wastewater containing similar pollutants.

Imprinted Fe–Ni double hydroxide nanorods with high selective protein adsorption capacity

Imprinted Fe–Ni double hydroxide nanorods with high selective protein adsorption capacity

Enhanced Propylene/Propane Separation via Aniline-Decorated ZIF-8 Membrane: Lattice Rigidity Adjustment and Adsorption Site Introduction.

Metal-organic framework (MOF)-based membranes excel in molecular separation, attracting significant research interest. The crystallographic microstructure and selective adsorption capacity of MOFs closely correlate with their gas separation performance. Here, aniline was added to the ZIF-8 synthesis in varying concentrations. Aniline, encapsulated within ZIF-8 cavities, interacts strongly with the 2-methylimidazole linker, resulting in both a shift in crystallographic phase from I_43 m to Cm in Rietveld refinement of X-ray diffraction (XRD) patterns and the selective adsorption behavior between propylene and propane. Consequently, an aniline decorative ZIF-8 (Anix-ZIF-8) membrane was prepared using a fast current-driven synthesis method, which exhibits good propylene/propane separation selectivity of up to 85. Calculation of the interaction energy between aniline and the various crystallographic phases of ZIF-8 using density functional theory (DFT) further verifies that aniline not only promotes the formation of crystallographic Cm phase, but also enhances the adsorption selectivity of propylene over propane. Aniline modification effectively tunes the crystallographic microstructure of ZIF-8, thereby, improving molecular sieving capabilities.

Mechanism of selective uranium adsorption using polyvinyl alcohol /Cyphos IL-101 / reduced graphene oxide composites

A novel composite material for uranium extraction from seawater, APGO, was prepared by crosslinking reduced graphene oxide (rGO) loaded with trihexyl(tetradecyl)phosphonium chloride (Cyphos IL-101) with polyvinyl alcohol. The experimental results indicate that the surface of APGO contains functional groups, such as carboxyl, hydroxyl, and phosphate, that have adsorption properties for uranium. APGO exhibits excellent hydrophilicity and stability while preserving the intact two-dimensional network structure of rGO. The specific surface area of APGO was 9.23 m2/g with an average pore size of 27.50 nm. Furthermore, the optimal pH range for APGO to adsorb uranium is 6–8, making it more suitable for extracting uranium from seawater. Notably, the selective adsorption capacity of APGO for uranium is significantly enhanced compared to that of AGO, with a Kd value approximately 4.6 times higher than that of AGO. The theoretical adsorption capacity is 467mg/g at 318 K (pH = 6). The process of uranium adsorption by APGO is a spontaneous endothermic reaction. The adsorption performance of APGO is noteworthy because it exhibits only a 2 % decrease after five adsorption–desorption cycles. Furthermore, APGO demonstrates commendable recyclability. Overall, APGO demonstrates a remarkable affinity for uranium and promising potential for efficiently extracting uranium from seawater.

Recent Developments in the Adsorption of Heavy Metal Ions from Aqueous Solutions Using Various Nanomaterials.

Water pollution is caused by heavy metals, minerals, and dyes. It has become a global environmental problem. There are numerous methods for removing different types of pollutants from wastewater. Adsorption is viewed as the most promising and financially viable option. Nanostructured materials are used as effective materials for adsorption techniques to extract metal ions from wastewater. Many types of nanomaterials, such as zero-valent metals, metal oxides, carbon nanomaterials, and magnetic nanocomposites, are used as adsorbents. Magnetic nanocomposites as adsorbents have magnetic properties and abundant active functional groups, and unique nanomaterials endow them with better properties than nonmagnetic materials (classic adsorbents). Nonmagnetic materials (classic adsorbents) typically have limitations such as limited adsorption capacity, adsorbent recovery, poor selective adsorption, and secondary treatment. Magnetic nanocomposites are easy to recover, have strong selectivity and high adsorption capacity, are safe and economical, and have always been a hotspot for research. A large amount of data has been collected in this review, which is based on an extensive study of the synthesis, characterization, and adsorption capacity for the elimination of ions from wastewater and their separation from water. The effects of several experimental parameters on metal ion removal, including contact duration, temperature, adsorbent dose, pH, starting ion concentration, and ionic strength, have also been investigated. In addition, a variety of illustrations are used to describe the various adsorption kinetics and adsorption isotherm models, providing insight into the adsorption process.

Selective single-atom adsorption for precision separation of lead ions in tap water via capacitive deionization

Capacitive deionization (CDI) offers a cost-effective and low-energy method for selective removal of Pb2+ from drinking water. Modifying CDI electrode surfaces with functional groups presents a versatile approach to enhancing selective ion adsorption capacity. However, a comprehensive understanding of the selectivity and removal efficiency of Pb2+ among diverse functional groups remains unexplored. Here, we investigated the effects of different functional groups (-SH, -COOH, and -NH2) attached to the graphene oxide (GO) electrode surfaces on Pb2+ selectivity and removal efficiency. Surprisingly, GO-COOH demonstrated single-atom adsorption of Pb2+, displaying superior removal efficiency and selectivity compared with -SH and -NH2, although -SH possesses significant chelation capability for Pb2+. Both density functional theory (DFT) calculations and X-ray pair distribution function (PDF) analyses confirmed that Pb2+ exhibits a theoretically higher affinity to -COOH. This research deepens our understanding of the interactions between functional groups and heavy metal ions, enabling selective and rapid separation of target cations for water purification.

Improvement of tetracycline removal using amino acid ionic liquid modified magnetic biochar based on theoretical design

In current research, biochar is widely used to remove antibiotic contamination from the environment. However, original biochar produced through direct pyrolysis has significant limitations in removing antibiotics. In this paper, response surface methodology provided the laudable choice for magnetic poplar biochar (MPBC) considering the synergistic effect of multi-factors as well as the restrictions abundance experiments during the preparation of MPBC. Amino acid ionic liquids (AAILs) are a class of ionic liquids in which amino acids act as the anionic component, combining the tunable properties of ionic liquids with the biocompatibility and functionality of amino acids. To ameliorate adsorption capacity of MPBC, tetra-ethylammonium glycinate ([TEA][Gly]) with the best affinity for tetracycline (TC) were screened from 600 AAILs based on theoretical predictions using the conductor-like screening model for real solvents (COSMO-RS) without extensive experimental. Furthermore, AAILs-modified magnetic biochar (MPBC-AAIL) was synthesized chemically for the first time. Adsorption kinetics, isotherms, and thermodynamic analyses revealed that TC adsorption by both MPBC and MPBC-AAIL is a monolayer, spontaneous, and exothermic chemical process. Moreover, MPBC-AAIL exhibited a maximum adsorption capacity of 305.9 mg·g−1. Meanwhile, MPBC-AAIL maintains superior adsorption performance for TC in different impurity solutions as well as in real water samples. The excellent reusability and selective adsorption capacity of the material demonstrate the superiority of the theoretical based design. The characterization reveals that the adsorption mechanisms include pore filling, π-π interactions, surface complexation, hydrogen bonding, and electrostatic interactions. In addition, theoretical calculations showed that ionic liquid modification altered the adsorption sites between TC and MPBC-AAIL, leading to enhanced adsorption. This comprehensive study introduces an innovative modification of biochar, providing a novel approach to designing biochar composites and promoting their application in the remediation of complex environmental pollution.

Beryllium adsorption from beryllium mining wastewater with novel porous lotus leaf biochar modified with PO43−/NH4+ multifunctional groups (MLLB)

Wastewater produced in beryllium mining seriously affects ecological balance and causes great environmental pressure. We designed a novel porous lotus leaf biochar modified with PO43−/NH4+ multifunctional groups (MLLB) and used it for beryllium(Be) removal from beryllium mining wastewater. Kinetic and thermodynamic experiments showed that the adsorption capacity (Qe) of Be with MLLB from the simulated beryllium mining wastewater could reach 40.38 g kg−1 (35 °C, pH = 5.5), and the adsorption process was spontaneous and endothermic. The dispersion coefficient Kd of Be with MLLB was 2.6 × 104 mL g−1, which proved that MLLB had strong selective adsorption capacity for Be. Phosphoric acid, ammonia, and hydroxyl groups on the MLLB surface would complex with Be to form Be(OH)2 and Be(NH4)PO4 complexation products, which implied that surface complexation and precipitation reactions might co-existed in the adsorption process. The above results showed that MLLB could effectively adsorb Be and prevent beryllium exposure in a beryllium mining process.Graphical

Crosslinking assembly of Propenyl-Calix[4]-Crown-6 interpenetrating functional mesoporous carbon Spheres: High selectivity and stability to Remove Cs(I) from high acid solution

The calix[4]-crown-6 ligand shows high selectivity for Cs(I) over other alkali and alkaline earth metal cations, making it a promising candidate for radiocesium separation. However, its high viscosity and poor adhesion limit its practical use and stability. In this study, an alkenyl-functionalized calix[4]-crown-6 (p-C[4]C6) was developed. Using a mesoporous structure and post-assembly techniques, a composite (p-C[4]C6/MMCs) was created via crosslinking within mesoporous matrix channels. The p-C[4]C6/MMCs exhibited high stability and practicality. The p-C[4]C6/MMCs demonstrated high selectivity, good reusability, and significant adsorption capacity (47.76 mg/g) for Cs(I) in 3.0 M HNO3. Kinetic, isotherm, and thermodynamic studies suggest a spontaneous chemical adsorption mechanism. This research provides insights into the design of calix[4]-crown-6 based materials and offers a viable approach for Cs(I) separation from high-level liquid waste (HLW).

Molecularly imprinted polymer gel with superior recognition and adsorption capacity for amphenicol antibiotics in food matrices

A molecular-imprinted polymer (MIP) gel with high effective recognition of amphenicol antibiotics was synthesized for the first time based on layered double hydroxide (LDH) as the support and initiator, and functionalized β-cyclodextrin (β-CD) as the functional monomer. The synergistic effect of molecular imprinting recognition and β-CD host-guest affinity enabled MIP gel to exhibit excellent selectivity (imprinted factors: 3.9–9.4) and high adsorption capacity (28.9–75.4 mg g−1) for amphenicol antibiotics. Different adsorption isotherms and kinetics models were followed, suggesting heterogeneous single-layer recognition and chemical adsorption. After 5 cycles of adsorption and desorption, the adsorption capacity of MIP gel retained above 83.6 %, demonstrating favorable reproducibility and stability. Under optimal conditions, the method validation showed a satisfactory limit of detection (5–10 μg L−1), good correlation (r2 > 0.9967), and respectable recovery (82.6–105.3 %). The MIP gel was applied to extract amphenicol antibiotics from food matrices, achieving recoveries in the range of 78.3–104.5 %. Importantly, the recognition mechanism was studied in detail using density functional theory. Therefore, the established method demonstrates high sensitivity and can be applied as a new tactic for detecting amphenicol antibiotics in food matrices.

Fabrication of a cost-effective metal oxide-based adsorbent from industrial waste slag for efficient CO2 separation under flue gas conditions

Efficient and affordable adsorbents for CO2 capture are essential in implementing carbon capture technology to mitigate the negative impact of greenhouse gas emissions. This study focuses on synthesizing new nanoporous adsorbents from industrial waste slag using a simple and cost-effective coprecipitation method. In this method, raw slag was milled for 48 h and used as a benchmark for comparing two newly synthesized adsorbents. Selectivity and pure gas isotherm experiments were conducted for all adsorbents in the 25–65°C temperature range and under harsh industrial conditions of 65°C and 15 % CO2. This study utilized the response surface methodology (RSM) to optimize the CO2 adsorption parameters. Specifically, the optimized adsorption conditions were determined for the 15/85 % CO2/N2 condition, and the optimal values for pressure and temperature were found to be 5 bar and 45°C, resulting in CO2/N2 selectivity of 5.65. The NH3-slag adsorbent was identified as the superior choice based on its selectivity and maximum adsorption capacity. The maximum adsorption capacity and cyclic efficiency were determined to be 4.15 mmol/g and 98.1 %, respectively, at a temperature, pressure, and composition of 45°C, 5 bar, and 15 % CO2. Isotherm and thermodynamic models were employed to further investigate the adsorption process. The isotherm results indicated that the adsorption of CO2 by adsorbents occurred heterogeneously in patch-wise sites. Meanwhile, the thermodynamic parameters showed that the process was exothermic and spontaneous, with ΔH° falling below 20 (kJ/mol), showing physisorption phenomena.

The Role of Fe(III) in Selective Adsorption of Pullulan on Calcite Surfaces: Experimental Investigation and Molecular Dynamics Simulation.

The floatability of fluorite and calcite exhibit similar properties, rendering their flotation separation challenging. Macromolecular polysaccharide reagents containing the polyhydroxyl group have shown broad promising application. The selectivity of polysaccharide is relatively low. In this study, the introduction of Fe3+ was employed to enhance the selective adsorption capacity of Pullulan polysaccharide towards fluorite and calcite minerals, thereby achieving effective flotation separation. Furthermore, the mechanism underlying intramolecular interactions was elucidated. The DFT calculation and XPS analysis revealed that the adsorption of Fe3+ on the calcite surface was more favorable, leading to the formation of a Ca-O-Fe structure. The MD simulation, XPS analysis, and Zeta potential analysis revealed that the Fe-OH groups on the surface of calcite reacted with the -OH groups in Pullulan and formed bonds, resulting in the formation of a Calcite-Fe-Pullulan structure. This facilitated the attachment of a significant number of Pullulan molecules to the calcite surface. The formation of a hydrophilic layer on the outer surface of calcite by Pullulan, in contrast to the absence of such layer on fluorite's surface, results in an increased disparity in surface floatability between these two minerals, thereby enhancing the efficiency of flotation separation.

Novel nitrogen-rich hydrogel adsorbent for selective extraction of rare earth elements from wastewater

Efficient recovery of rare earth elements (REEs) from wastewater is crucial for advancing resource utilization and environmental protection. Herein, a novel nitrogen-rich hydrogel adsorbent (PEI-ALG@KLN) was synthesized by modifying coated kaolinite-alginate composite hydrogels with polyethylenimine through polyelectrolyte interactions and Schiff’s base reaction. Various characterizations revealed that the high selective adsorption capacity of Ho (155 mg/g) and Nd (125 mg/g) on PEI-ALG@KLN is due to a combination of REEs (Lewis acids) via coordination interactions with nitrogen-containing functional groups (Lewis bases) and electrostatic interactions; its adsorption capacity remains more than 85 % after five adsorption-desorption cycles. In waste NdFeB magnet hydrometallurgical wastewater, the recovery rate of PEI-ALG@KLN for Nd and Dy can reach more than 93 %, whereas that of Fe is only 5.04 %. Machine learning prediction was used to evaluate adsorbent properties via different predictive models, with the random forest (RF) model showing superior predictive accuracy. The order of significance for adsorption capacity was pH > time > initial concentration > electronegativity > ion radius, as indicated by the RF model feature importance analysis and SHapley Additive exPlanations values. These results confirm that PEI-ALG@KLN has considerable potential in the selective extraction of REEs from wastewater.