Cooperative Adsorption Research Articles

Cooperative lattice theory for CO2 adsorption in diamine-appended metal-organic framework at humid direct air capture conditions.

The effect of humidity on the cooperative adsorption of CO2 from the air on amine-appended metal-organic frameworks is studied both experimentally and theoretically. Breakthrough experiments show that, at low relative humidities, there is an anomalous induction effect, where the kinetics at short times are slower than kinetics at long times. The induction effect gradually vanishes as relative humidity is increased, corresponding to an increase in CO2 adsorption rate. A new theory is proposed based on the lattice kinetic theory (LKT), which explains these experimental results. LKT can accurately represent the measured data over the full range of humidities by postulating that the presence of adsorbed water shifts the equilibrium clusters from cooperatively bound chains to non-cooperatively bound CO2. A consequence of this transition is that CO2 exhibits step adsorption isotherm in dry air and a standard Langmuir adsorption isotherm in high humidity air.

Octanuclear Zinc Clusters in Microporous Organic Polymers: Network-Enhanced Reductive CO2 Fixation to Formamides at Room Temperature.

A building block containing eight zincs and eight iodo groups (8Zn) is obtained by the Zn complexation of a salen ligand bearing two additional hydroxy groups. Through the Sonogashira-Hagihara coupling of 8Zn with 1,3,5,7-tetra(4-ethynylphenyl) adamantane, microporous organic polymers bearing octanuclear zinc clusters (MOP-8Zn) are prepared, exhibiting a high surface area of 562 m2g-1, microporosity, and a particulate morphology with an average diameter of 249nm. The MOP-8Zn exhibits significantly enhanced catalytic performance, compared to molecular counterparts, in the reductive carbon dioxide fixation to formamides, possibly due to the cooperative adsorption and confinement effect of networks on substrates.

Unveiling the versatile performance of transition metal sulfides in peroxymonosulfate activation

Advanced oxidation processes (AOPs) are promising treatment options for environmental remediation to reduce chemical oxygen demand (COD) and emerging contaminants. Transition metal sulfides (TMSs) are a class of common catalysts in AOPs, but actually, they also widely exist in the environment in the form of sulfide minerals and seriously contaminated water bodies as black-odorous substances. Therefore, it is crucial to find out their roles during water decontamination using AOPs. This study investigated different mechanisms and performance of four common TMSs (FeS, CuS, CoS and MnS) in peroxymonosulfate (PMS)-based AOPs for the removal of a representative micropollutant tetracycline (TC). The results showed that CoS/PMS was the most efficient with 100 % TC removal within 1 min, followed by FeS/PMS (100 %, 10 min) with the apparent rate constant (kobs) of 0.45 min−1. TC removal by CuS (kobs = 0.10 min−1) and MnS (kobs = 0.02 min−1) took 30 min with 96 % and 82 % removal, respectively. Interestingly, the dominant reactive species were different in these systems, i.e., high-valent iron (Fe(IV)) in FeS/PMS, mainly radicals (•OH, SO4•−, O2•−) and singlet oxygen (1O2) in CuS/PMS, and Co(IV) and 1O2 in CoS/PMS. In comparison, TC was removed in MnS/PMS mainly through cooperative adsorption, reduction and oxidation by MnS. Low valent sulfur species, such as S2− and S22−, may participate in the valence cycles of metals or TC reduction. The above four systems had a wide pH (3.6–11.1) adaptability and a strong anti-interference ability to co-existing Cl−, SO42− and NO3−, but could be hindered by CO32−, PO43− and humic acid. This study provides novel insights into the TMS-based catalysts in AOPs, which will pave the way for advancing AOP technology.

Cooperative Adsorption and Diffusion of Small Alcohols in Metal-Organic Framework ZIF-8 and Intrinsically Microporous Polymer PTMSP.

Fundamental understanding of molecular interactions and transport within microporous materials displaying cooperative Type V adsorption is challenged by the unique features of this isotherm type. In order to capture a broad understanding of this uncommon, yet industrially relevant, behavior in microporous materials, this investigation examines the adsorption equilibria and kinetics of methanol and ethanol in both a metal-organic framework (MOF) material, ZIF-8, and a high free volume polymer of intrinsic microporosity, poly[1-(trimethylsilyl)-1-propyne] (PTMSP). A novel formulation that can capture the cooperative effects of small alcohols in its description of adsorption equilibria and kinetics is proposed. It is subsequently applied to successfully capture some previously uncharacterized or semiempirically characterized data for equilibria and the loading dependence of the diffusivity in both ZIF-8 and PTMSP, which are materials chosen for their industrial relevance. Finally, it is anticipated that the results of this study can fill the current void that exists in meaningful mechanistic and analytical descriptions of cooperative equilibrium and diffusion phenomena in microporous materials.

Graphene Oxide Covalently Functionalized with 5-Methyl-1,3,4-thiadiazol-2-amine for pH-Sensitive Ga3+ Recovery in Aqueous Solutions.

A novel graphene-based composite, 5-methyl-1,3,4-thiadiazol-2-amine (MTA) covalently functionalized graphene oxide (GO-MTA), was rationally developed and used for the selective sorption of Ga3+ from aqueous solutions, showing a higher adsorption capacity (48.20 mg g-1) toward Ga3+ than In3+ (15.41 mg g-1) and Sc3+ (~0 mg g-1). The adsorption experiment's parameters, such as the contact time, temperature, initial Ga3+ concentration, solution pH, and desorption solvent, were investigated. Under optimized conditions, the GO-MTA composite displayed the highest adsorption capacity of 55.6 mg g-1 toward Ga3+. Moreover, a possible adsorption mechanism was proposed using various characterization methods, including scanning electron microscopy (SEM) equipped with X-ray energy-dispersive spectroscopy (EDS), elemental mapping analysis, Fourier transform infrared (FT-IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). Ga3+ adsorption with the GO-MTA composite could be better described by the linear pseudo-second-order kinetic model (R2 = 0.962), suggesting that the rate-limiting step may be chemical sorption or chemisorption through the sharing or exchange of electrons between the adsorbent and the adsorbate. Importantly, the calculated qe value (55.066 mg g-1) is closer to the experimental result (55.60 mg g-1). The well-fitted linear Langmuir isothermal model (R2 = 0.972~0.997) confirmed that an interfacial monolayer and cooperative adsorption occur on a heterogeneous surface. The results showed that the GO-MTA composite might be a potential adsorbent for the enrichment and/or separation of Ga3+ at low or ultra-low concentrations in aqueous solutions.

Experimental design of polymer synthesis applied to the removal of Cd2+ ions from water via adsorption

Cadmium is a highly toxic metal, and its presence can have adverse effects on both human health and aquatic ecosystems. The efficient removal of cadmium from wastewater is therefore of crucial importance, but traditional methods have proved to be inadequate. Thus, technologies for the treatment of wastewater containing cadmium, including adsorption, have been developed. The aim of this study was the preparation of a polymeric material by the grafting reaction of κ-carrageenan and its use as an adsorbent for cadmium removal. This was performed to study the removal capacity of cadmium ions in synthetic solutions, as well as the effects of pH and ions on adsorption capacity, adsorption kinetics, isotherms, and reusability. Additionally, the disinfectant potential of the solution was evaluated for the inactivation of total coliforms and E. coli in river water. The best adsorption capacity was 75.52 ± 1.325 mg g−1, with the kinetics described by the pseudo-second order model. Maximum adsorption capacity (127.6 ± 1.833 mg g−1) and RL (0.0113) were determined using the Langmuir model, the Freundlich model was the one that best fits the experimental data and indicated cooperative adsorption, and the Dubinin-Radushkevich isotherm was used to obtain the adsorption energy and identify that it is physical. The presence of ions K+, Na+, Mg2+, and Ca2+ in a concentration of 0.5% decreased the adsorption capacity, and that at pH 2.0, the adsorption capacity was drastically reduced. The study indicates that the polymer has potential as an adsorbent for removing cadmium from aqueous solutions and exhibits self-disinfecting properties.

One-step rapid removal of Cu(II) complexes via dual-active-site MOF catalysis with Peroxymonosulfate: Cooperative oxidation and adsorption

The removal of heavy metal complexes (HMCs) from wastewater is challenging due to their structural stability. Traditional methods require advanced oxidation processes (AOPs) for decomplexation, followed by chemical precipitation or adsorption. This study proposes a one-step approach using Co-imidazolate zeolitic framework-67 (ZIF-67) for simultaneous oxidation-decomplexation and in-situ adsorption of HMCs. The ZIF-67/peroxymonosulfate (PMS) system achieves 97.8 % removal of Cu(II)-citric acid complex (Cu-CA) in 60 mins, even under alkaline conditions, and demonstrates strong selectivity against ions like Ca, Mg, Na, and humic acid (HA). It effectively treats various contaminated water sources, achieving over 90 % removal efficiency for Cu(II) complexes such as oxalic acid (OA) and ethylenediaminetetraacetic acid (EDTA). The mechanism involves sulfate radicals (SO4•−) and singlet oxygen (1O2) for decomplexation, followed by amine groups in MOFs capturing Cu(II) ions through coordination interactions. This work offers a straightforward one-step method for HMCs contamination mitigation.

Constructing the synergistic active sites of nickel bicarbonate supported Pt hierarchical nanostructure for efficient hydrogen evolution reaction

Constructing synergistic active sites and optimizing the cooperative adsorption energies for hydrogen and hydroxyl based intermediates are two essential strategies to improve the sluggish kinetics of hydrogen evolution reaction (HER) in alkaline medium. However, it is still in its infancy to simultaneously achieve these goals, especially for designing a well-defined carrier with multiple hydroxyl adsorption sites. Herein, the Ni(HCO3)2 nanoplates (NHC) with horizontal interfaces sites of Ni-terminated NiO, NiOOH, NiCOO, and Ni(OH)2 were employed as the hydroxyl adsorption active sites, which could anchor Pt particles with hydrogen adsorption active sites, constructing the synergistic active sites (NHC-Pt) for HER catalysis. Evidenced by X-ray photoelectron spectroscopy (XPS) and extended X-ray absorption fine structure (EXAFS), the NHC could affect the chemical state and electronic structure of Pt particles by forming bond of Pt-O which could reduce the reaction energy barriers, facilitate the adsorption of hydrogen and establishment of H–H bond. Furthermore, density functional theory (DFT) theoretical calculation revealed that the related process of hydroxide was the rate-determining step. It is demonstrated the hydroxyl group presents the lowest energy barrier for desorption in the process of HER when the gradual desorption process could be described as a migration from Ni(HCO3)2·OH directly or via other Ni-based systems formed after partial decomposition of nickel hydrocarbonate to Ni(OH)2···OH with following desorption. As a result, the NHC-Pt hierarchical nanostructure demonstrated superior activity towards HER in a pH-universal solution. This enhancement can be attributed to the optimized electronic structure of Pt, the migration of hydroxyl group on NHC substrates, and the synergistic effects between the NHC carrier and Pt particles.

Interaction of phenolic compounds with functionalized TiO2: Enhanced catechol adsorption and cooperative phenol adsorption

A commercial TiO2 sample functionalized with 3-aminopropyltrimethoxysilane (APTMS) and 4-carboxyphenylboronic acid (CPBA), has been previously proposed as a suitable photocatalyst to perform selective photocatalytic degradation of pollutants in aqueous streams, while avoiding the oxidation of valuable catechol simultaneously present in the reacting medium. In the present study, we highlight the adsorption mechanisms underlying the higher affinity of catechol, compared to phenol, with the surface of modified TiO2, quantitatively justifying the photocatalytic selective degradation results previously obtained. Moreover, a cooperative adsorption mechanism of phenol onto the TiO2 sample modified with APTMS has been for the first time observed. The resulting sigmoidal adsorption isotherms, satisfactorily fitted with the Hill model, could be attributed to the enhanced surface hydrophobicity and, more importantly, to alterations of the folding of APTMS molecules on the TiO2 surface occurring upon increasing the concentration of the phenolic compounds.Photocatalytic tests revealed that the existence of boronate groups on the surface of TiO2 hinders the photocatalytic degradation of catechol and facilitates a swifter oxidation of phenol. These findings confirm the potential for selective photocatalytic degradation, in line with modern conceptions of innovative and environmentally sustainable wastewater treatments.

Azadirachta indica leaf extract based green-synthesized ZnO nanoparticles coated on spent tea waste activated carbon for pharmaceuticals and personal care products removal

Pharmaceuticals and personal care products (PPCPs) are emerging contaminants in aqueous systems, posing threat to both human health and environment. In prior research, predominant focus has been on examining various adsorbents for removing PPCPs from single-pollutant systems. However, no study has delved into simultaneous adsorption of PPCPs multi-pollutant mixture. This study evaluates performance of Azadirachta indica leaf extract-based green-synthesized ZnO nanoparticles coated on spent tea waste activated carbon (ZTAC) for removing sulfadiazine (SZN) and acetaminophen (ACN). Adsorption investigations were conducted in single-component (ACN/SZN) and binary-component (ACN + SZN) systems. The synthesized ZTAC was characterized using SEM, XRD, FTIR, EDX, porosimetry and pHpzc analysis. The study examines impact of time (1–60 min), dose (0.2–4 g/L), pH (2–12) and PPCPs concentration (1–100 mg/L) on ACN and SZN removal. Various kinetic and isotherm models were employed to elucidate mechanisms involved in sorption of PPCPs. Furthermore, synergistic and antagonistic aspects of sorption process in multi-component system were investigated. ZTAC, characterized by its crystalline nature and surface area of 980.85 m2/g, exhibited maximum adsorption capacity of 47.39 mg/g for ACN and 34.01 mg/g for SZN under optimal conditions of 15 min, 3 g/L and pH 7. Langmuir isotherm and pseudo-second-order kinetic model best-fitted the experimental data indicating chemisorption mechanism. Removal of ACN and SZN on ZTAC demonstrated synergistic nature, signifying cooperative adsorption. Overall, valorization of ZTAC offers effective and efficient adsorbent for elimination of PPCPs from wastewater.

A Porphyrinic Metal-Organic Framework with Cooperative Adsorption Domains for PFAS Removal from Water.

The removal of toxic poly- and perfluoroalkyl substances (PFAS) as persistent pollutants from wastewater is imperative but challenging for water remediation. Many adsorbents including activated carbon, biochar, and clay minerals have been investigated for PFAS removal, but most of these materials are faced with high cost or/and low efficiency. The use of metal-organic frameworks (MOFs) as sorbents is attractive for efficient removal of PFAS due to their tailor-made structures and high surface areas. Herein, we synthesized, characterized a water stable Zr-based porphyrinic MOF (PCN-224) with cooperative adsorption domains, and demonstrated its excellent capture performance toward perfluorooctane sulfonate (PFOS), perfluorohexane sulfonate (PFHxS) and perfluorobutane sulfonate (PFBS). PCN-224 has maximum uptake capacities of 963, 517, and 395 mg g-1 for PFOS, PFHxS, and PFBS, respectively, which are much higher than that of granular activated carbon. Moreover, coexistent anions (Cl-, SO4 2-) and humic acid have negligible effects on PFOS adsorption. The excellent adsorption performance of PCN-224 toward PFOS is due to the orthogonal cationic channel pores with a diameter of 1.9 nm, the hydrophobic porphyrin units, and the Zr6 clusters with acidic sites. PCN-224 can be readily regenerated and reused. This work highlights the potential of MOFs with multiple adsorption domains for water remediation.

Revealing the Origin of Cooperative Adsorption of Chains on Nanoparticle Surfaces through Coarse-Grained Simulations.

This work aims to deepen our understanding of the molecular origin of the recently observed phenomenon of polymer cooperative adsorption onto faceted nanoparticle (NP) surfaces. By exploring a large parameter space for polymer/NP interactions through coarse-grained (CG) molecular dynamics (MD) simulations, it is found that consistent with experiments the presence or absence of cooperativity is related to solvent quality and relative interaction strengths between the polymer and the adsorbent. Specifically, positive cooperativity is associated with stronger polymer-polymer interaction than polymer-surface interactions and vice versa for negative cooperativity. This contrast in interaction energies manifests in positive cooperativity (i.e., increased affinity) and negative cooperativity (i.e., decreased affinity) as concentration increases. It is also found that increasing chain length strengthens cooperativity effects and that the nanoscale confinement of polymer chains to the adsorbing facet (due to weaker affinity to corners and edges) enhances positive cooperativity but weakens negative cooperativity. Moreover, adsorption onto a spherical NP shows stronger positive cooperativity but weaker negative cooperativity compared with adsorption onto a cubic NP of equal surface area. It was further found that as polymer bulk concentration increases, the free energy of adsorption decreases in positive cooperativity, increases in negative cooperativity, and is independent of concentration in noncooperative systems consistent with the phenomenological explanation of cooperativity. We further found that positive cooperativity is associated with growing fluctuations in the adsorption density at critical bulk polymer concentrations. This behavior can be attributed to the competition between enthalpic gains and entropic losses upon adsorption. Overall, our results shed light on the microscopic origin of cooperative adsorption and the role of solvent quality, which can be leveraged in, for example, controlling NP growth into target shapes and designing NP catalysts with improved performance.

The effects of co-existing acridine on adsorption-desorption behavior of carbazole in soils: Co-sorption and mechanism insight

Carbazole (CBZ) and acridine (ACR) are polycyclic aromatic nitrogen heterocycles (PANHs) widely found in combined contaminated soils, while investigations on organic-organic interactions have been very limited. In this study, batch experiments were carried out on five soils with different properties, taking CBZ as a representative of PANHs and ACR as a co-existing contaminant. The adsorption isotherms of CBZ (50–1000 μg/L) were nonlinear. Soil organic matter (SOM) and cation exchange capacity (CEC) showed positive correlations with CBZ adsorption-desorption coefficients. The adsorption mechanisms of CBZ involved hydrogen bonding, π-π interaction, and cation-π bonding. Different concentrations of ACR had varying effects on CBZ. The adsorption of CBZ was inhibited with 250 μg/L ACR. The cooperative adsorption was observed on three soils with increasing ACR concentration (1000 μg/L) and led to more pronounced nonlinear isotherms. The S-shaped isotherms of ACR indicated that ACR was adsorbed to the soil surface in a perpendicular configuration. New adsorption sites were created allowing for increased CBZ adsorption through π-π interaction with ACR. Therefore, variations in soil properties and potential impacts of co-existing contaminants should be well considered when assessing the combined pollution of site soil. This will contribute to a more accurate estimation of environmental and health risks.

Efficient C2H2/CO2 separation in two 2-fold interpenetrating metal-organic frameworks with ultrahigh C2H2 packing density

Adsorptive separation of C2H2/CO2 is industrially important and feasible but the design of highly efficient adsorbents remains very challenging owing to the almost identical physicochemical properties of the two gases. Herein, we constructed two new microporous metal–organic frameworks (MOFs), termed CTGU-39/40 (CTGU = China Three Gorges University), with 2-fold interpenetrating frameworks and unique pore geometry/chemistry for C2H2/CO2 separation. Both the activated MOFs (CTGU-39/40-a) can preferentially adsorb C2H2 over CO2 with excellent selectivity of 8.4 and 3.3 at 298 K and 100 kPa, respectively, as verified by static adsorption measurements. More importantly, attributed to the suitable pore aperture size (∼5 Å) and abundant adsorption sites, CTGU-39-a combines exceptionally high packing density of C2H2 (0.41 g mL−1) and moderate isosteric heat of adsorption (Qst) for C2H2 (26.8 kJ mol−1), outperforming most previously reported adsorbents. Theoretical calculations reveal that the preferential adsorption of C2H2 within two MOFs is driven by cooperative adsorption behavior through multiple H-bonding and Coulomb interactions. Experimental breakthrough results further confirmed their practical separation ability and recyclability toward an equimolar C2H2/CO2 mixture at different feeding rates. This work may offer new insights into the design of advanced porous materials for C2H2 purification and potentially other gas separations.

Interplay of α-synuclein with Lipid Membranes: Cooperative Adsorption, Membrane Remodeling and Coaggregation.

α-Synuclein is a small neuronal protein enriched at presynaptic termini. It is hypothesized to play a role in neurotransmitter release and synaptic vesicle cycling, while the formation of α-synuclein amyloid fibrils is associated with several neurodegenerative diseases, most notably Parkinson's Disease. The molecular mechanisms of both the physiological and pathological functions of α-synuclein remain to be fully understood, but in both cases, interactions with membranes play an important role. In this Perspective, we discuss several aspects of α-synuclein interactions with lipid membranes including cooperative adsorption, membrane remodeling and α-synuclein amyloid fibril formation in the presence of lipid membranes. We highlight the coupling between the different phenomena and their interplay in the context of physiological and pathological functions of α-synuclein.

Assessment of Sorption of Anthocyanins from Red Cabbage onto Bentonites from Patagonia (Argentina)

In the northern Patagonian region of Argentina, some of the largest bentonite deposits exist. Four bentonite samples (B1, B2, B3, and B4) from two deposits were thoroughly characterised and evaluated as potential adsorbents of anthocyanins extracted from red cabbage. Anthocyanins (ACys) are natural colourants obtained from fruits and plants and have shown excellent antioxidant properties that have promising applications in health. The adsorption of ACys onto bentonites enhances their stability relative to that observed in aqueous solutions. Material characterisation showed that three of the samples are soFdium bentonites (Na-bentonites: B2, B3, and B4), while the fourth exhibits a large quantity of magnesium and calcium in its interlayer, classifying it as a Mg-Ca-Na-bentonite (B1). Na-bentonites demonstrated higher ACy adsorption capacities, occurring through cation exchange, while Mg-Ca-Na-bentonite adsorption occurs by another type of interaction and a cooperative adsorption mechanism, resulting in the lowest ACy adsorption. The highest adsorption capacity was noted for B3, characterised by the highest smectite content, cation exchange capacity, and proportion of monovalent cations in its interlayer. Under the conditions studied, sodium smectites proved to be capable of retaining red cabbage ACys, thereby introducing a novel avenue for potential applications of regional materials with potential implications for health-related uses.

Entropic Effects on Diamine Dynamics and CO2 Capture in Diamine-Appended Mg2(dopbdc) Metal-Organic Frameworks.

Recent measurements [Xu, J.; J. Phys. Chem. Lett. 2019, 10 (22), 7044-7049] have reported temperature-dependent rates of detachment of diamine from Mg sites in diamine-appended Mg2(dobpdc) [dobpdc4- = 4,4'-dihydroxy(1,1'-biphenyl)-3,3'-dicarboxylic] metal-organic frameworks, a process hypothesized to be a precursor for cooperative CO2 adsorption, leading to step-shaped isotherms or isobars. Here, we compute the rate of diamine exchange in this system for different diamines using metadynamics simulations based on a density functional theory-derived neural network potential. Reanalyzing recent measurements accounting for entropic effects, we find a positive correlation between the previously reported CO2 adsorption step pressure and the free energy at room temperature and show that the experiments and simulations are in good qualitative and quantitative agreement. The rates obtained here provide new insight into the chemical dynamics of CO2 adsorption in a class of materials that are promising for carbon capture and a lower bound on the time scale of cooperative adsorption.

Mobility and transport of pharmaceuticals nalidixic acid and niflumic acid in saturated soil columns

Pharmaceutical compounds often coexist in mixtures rather than as individual entities. However, little is known about their co-adsorption and co-mobility in soil and groundwater. In this study, we investigated the adsorption of a quinolone antibiotic (nalidixic acid, NA) and an anti-inflammatory agent (niflumic acid, NFA) onto two soils from France and Sweden in water-saturated soil columns. Despite its lower hydrophobicity, adsorption of NA is much greater than NFA, which can be ascribed to the presence of both carbonyl and carboxylic groups in NA molecule. The data suggest that chemical adsorption to soil components can mainly take place through hydrogen bonding and surface complexation mechanisms, prevailing over hydrophobic interactions. Accordingly, more sorption of NA and NFA was observed in the Swedish soil because it contains more clay content, and much greater Al and Fe contents than the French soil. Injection of NA/NFA mixture in the column did not modify the breakthrough behavior compared to single systems, although cooperative adsorption was observed under static batch conditions. Ca2+ inhibited NA adsorption by forming a soluble NA-Ca2+ complex but promoted NFA adsorption both in single and binary systems. Their mobility in soil columns was well predicted using a new transport model that accounts for both kinetics and binding reactions of NA and NFA to soil constituents. This work will help in accurately predicting the mobility of coexisting pharmaceutical compounds in soils.

Rapid and selective removal of radioactive iodide ions from wastewater via bismuth-based metal-organic frameworks

As one of the main components of the nuclear wastewater discharged from Fukushima, the efficient and safe disposal of radioactive 129I- is very urgent. Here, the trapping ability of water-soluble iodine anions is studied through a metal-organic framework of bismuth (Bi-MOF, select CAU-17 as the representative). It is found that CAU-17 achieves efficient capture of I- ions through chemical and physical cooperative adsorption, with a maximum adsorption capacity of up to 268.9 mg g-1. In addition, the adsorbent also exhibits superior adsorption kinetics and selectivity for I- ions and works stably over a wide pH range of 2–12. Density functional theory (DFT) calculations indicate that most I- ions are immobilized by attacking the Bi3+ sites of the CAU-17 ternary channel to form BiOI compounds. Compared with silver-based adsorbent, the prepared Bi-based adsorbent CAU-17 is more economical and practical. In summary, this work demonstrates the promising application of Bi-MOFs for purifying industrial water-soluble radioactive iodide ions.

Cooperative adsorption of Sb(V) in water by magnetic MgFe2O4-biochar composite beads

As the major form of antimony in the aqueous environment, the adsorption for the removal of Sb(OH)6- is a meaningful task. In this study, MgFe2O4-doped and iron(Ⅲ) alginate cross-linked biochar ternary composite adsorbents, Fe/(MgFeO-BC) beads, were synthesized. The typical characterization analysis showed the successful synthesis of Fe/(MgFeO-BC) beads with the significant synergistic effect on the adsorption activity of MgFe2O4, the foaming effect of BC and the dispersing effect of the bead skeleton. The adsorption experiments showed significantly increased adsorption capacity of Fe/(MgFeO-BC) compared to the comparative adsorbent with Qm= 125.65 mg/g. The adsorption was able to reach equilibrium within 350 min. At low initial Sb(OH)6- concentration, the adsorption of Fe/(MgFeO-BC) can still achieve the standard antimony concentration (≤0.02 mg/L), giving potential for practical applications. The introduction of MgFe2O4 enhanced the adsorption capacity while imparting magnetic properties of composite beads, resulting in significant improvement in separation efficiency. The -OH in the structure of MgFe2O4 is the adsorption active site of Fe/(MgFeO-BC), and the adsorption of Sb(OH)6- is accomplished mainly through ligand exchange and inner-sphere complexation. These results suggest that Fe/(MgFeO-BC) is a kind of promising Sb(OH)6- adsorbent with safe, green and recyclable properties, which provides a reference for the removal of Sb(OH)6- from wastewater, even at low concentrations.