Adsorption behavior of arsenicals on MIL-101(Fe): The role of arsenic chemical structures

Highly sensitive determination of trace arsenic(III) onto carbon paste electrode modified with graphitic carbon nitride decorated Fe-MOF

An effective electrochemical sensor was developed to detect and determine of the As(III) by modifying the carbon paste electrode (CPE) with graphitic carbon nitride decorated with iron-based metal-organic frameworks (Fe-MOF/g-C3N5). The differential pulse anodic stripping voltammetry (DPASV) method was used to analyze As(III) ions in a phosphate buffer solution (0.10 M, pH = 5). Fe-MOF/g-C3N5/CPE showed high sensitivity (4.24 μA μg-1 L), satisfactory linear range (0.50 μg L-1-5.00 μg L-1 and 5.00 μg L-1-30.00 μg L-1), and low detection limit (LOD, 0.013 μg L-1). The prepared sensor was showed an excellent repeatability and selectivity, and successfully used for determination of the As(III) ion in ambient waters and apple juice samples.

A label-free electrochemical biosensor based on a bimetallic organic framework for the detection of carbohydrate antigen 19-9

Carbohydrate antigen 19-9 (CA19-9) is an important marker for pancreatic cancer, ovarian cancer and other tumors, and its rapid and stable detection is the basis for early diagnosis and treatment. In this paper, a label-free electrochemical immunosensor for the sensitive detection of CA19-9 has been developed. First, the synthesis of two novel core-shell bimetallic nanomaterials, namely Ce-MOF-on-Fe-MOF and Fe-MOF-on-Ce-MOF, was accomplished using the MOF-on-MOF approach. The poor electrical conductivity of MOF materials was addressed by incorporating polyethylenimide (PEI) functionalized rGO with Ce-MOF-on-Fe-MOF and Fe-MOF-on-Ce-MOF nanomaterials. Simultaneously, toluidine blue (Tb) was employed as a redox probe and physically adsorbed onto the synthesized materials, resulting in the formation of two nanomaterials: rGO@Ce-MOF-on-Fe-MOF@Tb and rGO@Fe-MOF-on-Ce-MOF@Tb. The fundamental characterization reveals that the sensing performance of the rGO@Ce-MOF-on-Fe-MOF@TB-based immune sensor surpasses that of the rGO@Fe-MOF-on-Ce-MOF@TB-based immune sensor, which is attributed to the fact that, unlike the interlayer-constrained structure of Fe-MOF-on-Ce-MOF, in Ce-MOF-on-Fe-MOF, Ce-MOF penetrates into Fe-MOF to form a heterogeneous structure due to the relatively large pore size of Fe-MOF, which better combines the excellent biocompatibility and strong anchoring effect of Fe MOFs on antibodies, as well as the high electrochemical activity and conductivity of Ce-MOF, to enhance sensing performance. The proposed label-free immunosensor based on rGO@Ce-MOF-on-Fe-MOF@Tb has a wide linear range (1-100 000 mU mL-1), a low detection limit (0.34 mU mL-1), good stability, reproducibility, and repeatability, and satisfactory applicability, which provides a potential platform for clinical applications.

Enhanced degradation of 2,4-dichlorophenol in groundwater by defective iron-based metal-organic frameworks: Role of SO3- and electron transfer

The purposeful formation of crystal defects was regarded as an attractive strategy to enhance the catalytic activity of Fe-MOFs. In this study, the pyrolytic hydrochloric acid-modulated MIL-101-NH2 (P250HMN-2) was fabricated for the first time, and the important role of pyrolysis in the formation of crystal defects was confirmed. PDS was introduced as an enhancer for the P250HMN-2/Na2SO3 system. Without pH adjustment, 99.7 % of 2,4-DCP was removed by the P250HMN-2/Na2SO3/PDS system in 180 min. The catalytic performance of P250HMN-2 improved 2.5-fold than that of MIL-101-NH2. It was found that the high density of Fe-CUSs on P250HMN-2 were the major active sites, which could efficiently react with SO32- to generate ROS through electron transfer. The results of quenching experiments, probe tests, and EPR tests indicated that SO3-, SO4-, 1O2, OH, and SO5- were involved in the 2,4-DCP degradation process, with SO3-, SO4-, and 1O2 playing major roles. Moreover, P250HMN-2 could effectively degrade 2,4-DCP for 148 h in a fixed-bed reactor with excellent stability and reusability, indicating a promising catalyst for practical applications.

Tuning strategies of MIL metal organic frameworks for adsorptive removal of formaldehyde in air

Materials Institute Lavoisier (MIL) metal organic frameworks (MOFs) are known for their potential to adsorb gaseous organic pollutants. This study explores the synergistic effects between the selection of central metals (e.g., titanium, iron, and aluminum) and the incorporation of -NH2 groups in terms of adsorption efficiency against gaseous formaldehyde (FA). A group of the pristine MIL MOFs is synthesized using three different metals (i.e., titanium, iron, and aluminum) and terephthalic acid along with their NH2 derivatives using 2-aminoterephthalic acid. Among the pristine forms, MIL-125(Ti) achieves the highest FA adsorption capacity (Q) of 26.96 mg g-1 and a partition coefficient (PC) of 0.0898 mol kg-1 Pa-1. Further, amination significantly improves the FA adsorption potential of NH2-MIL-125(Ti) with a Q value of 91.22 mg g-1 (PC = 0.3038 mol kg-1 Pa-1). In situ diffuse reflectance infrared Fourier-transform spectroscopy reveals that the FA adsorption of plain MILs should be governed primarily by physisorption. In contrast, FA adsorption of NH2-MILs appears to be regulated by both physisorption and chemisorption, while the latter being affected mainly through FA-NH2 interactions (Schiff base reactions). These findings provide valuable insights into the utility of aminated MIL sorbents, possibly toward the efficient management of indoor air quality.

Integrated Solution for As(III) Contamination in Water Based on Crystalline Porous Organic Salts

A stable crystalline organic porous salt (CPOSs-NXU-1) with 1D apertures has been assembled by the solvothermal method, which shows high-sensitivity "turn-on" fluorescence detection and large-capacity adsorption of As(III) ions in water. The detection limits, saturated adsorption capacity, and removal rate of CPOSs-NXU-1 for As(III) ions in an aqueous solution can reach 74.34 nm (5.57 ppb), 451.01 mg g-1, and 99.6%, respectively, at pH = 7 and room temperature. With the aid of XPS, IR, Raman, and DFT theoretical calculations, it is determined that CPOSs-NXU-1 adsorbed As(III) ions in the form of H2AsO3 - and H3AsO3 through hydrogen bonding between the host and guest. The mechanism for fluorescence sensitization of As(III) ions to CPOSs-NXU-1 is mainly to increase the energy level difference between the ground state and excited state investigated by UV-vis absorption spectra, UV-vis diffuse reflectance spectra, and theoretical calculations. By constructing fluorescent CPOSs, an integrated solution has been achieved to treating As(III) contamination in the water that is equipped with detection and removal. These results blaze a promising path for addressing trivalent arsenic contamination in water efficiently, rapidly, and economically.

Low-temperature subcritical water dechlorination composites of waste PVC/coal fly ash with powerful sensing activity for chemiluminescent detection of acetamiprid and imidacloprid

Pesticide residues in agricultural products are serious threat to people's health. Real-time monitoring of pesticides residues in the environment and agricultural products posed challenges to sustainable methods with high analytical performance for pesticide detection. Herein, waste PVC/coal fly ash (the mass ratio of PVC and coal fly ash was 4:1) was dechlorinated in subcritical water at low temperature to achieve nearly 100 % dechlorination of PVC and obtain carbon-based composite materials (CM-Fe/Al/Si-dPVC) with strong sening activity. For CM-Fe/Al/Si-dPVC, CFe bonding resulted in strong electron migration, and nano/μm SiO2 and Al2O3 doping in the layered polyene C matrix provided large specific surface area, and silicon hydroxyl created good heterogeneous catalytic interfaces. CM-Fe/Al/Si-dPVC could strongly trigger luminol chemiluminescence (CL) reaction and produce intense CL signals. Neonicotinoid pesticides (acetamiprid and imidacloprid) bonded with CM-Fe/Al/Si-dPVC through coordination chelation and hydrogen bonding, which shielded the catalytic active site and increased the Fermi level of system, thus quenching CL reaction. Inspired by these, a cheap CL assay was constructed for detecting neonicotinoids combinations of acetamiprid and imidacloprid (NICs). The detection limits of NICs were 0.7 ng/L. Satisfactory recoveries were obtained for real agricultural products and environmental samples. The results of life cycle evaluation (LCA) revealed that the strategy had significantly small global warming potential (GWP). This work presented a sustainable method with environmental benefits for the detection of neonicotinoids, and also opened up new way for the recycling of organic solid wastes.

Pyrazine-based iron metal organic frameworks (Fe-MOFs) with modulated O-Fe-N coordination for enhanced hydroxyl radical generation in Fenton-like process

Rational design of coordination environment of Fe-based metal-organic frameworks (Fe-MOFs) is still a challenge in achieving enhanced catalytic activity for Fenten-like advanced oxidation process. Here in, novel porous Fe-MOFs with modulated O-Fe-N coordination was developed by configurating amino terephthalic acid (H2ATA) and pyrazine-dicarboxylic acid (PzDC) (Fe-ATA/PzDC-7:3). PzDC ligands introduce pyridine-N sites to form O-Fe-N coordination with lower binding energy, which affect the local electronic environment of Fe-clusters in Fe-ATA, thus decreased its interfacial H2O2 activation barrier. O-Fe-N coordination also accelerate Fe(II)/Fe(III) cycling of Fe-clusters by triggering the reactive oxidant species mediated Fe(III) reduction. As such, Fe-ATA/PzDC-7:3/H2O2 system exhibited excellent degradation performance for typical antibiotic sulfamethoxazole (SMX), in which the steady-state concentration of hydroxyl radical (OH) was 1.6 times higher than that of unregulated Fe-ATA. Overall, this study highlights the role of O-Fe-N coordination and the electronic environment of Fe-clusters on regulating Fenton-like catalytic performance, and provides a platform for precise engineering of Fe-MOFs.

Using Quercetin to Construct Molecularly Imprinting Polymer in the Preparation and Enrichment of Flavonol and Flavonoid Compounds

Flavonol and flavonoid compounds are important natural compounds with various biomedical activities. Therefore, it is of great significance to develop a strategy for the specific extraction of flavonol and flavonoid compounds. Quercetin is a well-studied flavonoid possessing many health benefits. This compound is a versatile antioxidant known to possess protective abilities against body tissue injury induced by pathological situations and various drug toxicities. Although quercetin is widely distributed in many plants, its content generally is not very high. Therefore, the specific extraction of quercetin as well as other flavonol and flavonoid compounds has profound significance. In this work, the quercetin molecularly imprinting polymer (QMIP) was successfully prepared, in which a typical flavonol quercetin was selected as the template molecule. QMIP was synthesized by performing the surface molecular imprinting technology on the surface of NH2-MIL-101(Fe). Our study results showed that QMIP exhibited quick binding kinetic behavior, a high adsorption capacity (57.04[Formula: see text]mg/g), and the specific recognition ability toward quercetin compared with structurally distinct compounds (selective [Formula: see text]). The specific adsorption ability of quercetin by QMIP was further explained using computation simulation that molecules with non-planar 3D conformations hardly entered the molecularly imprinted cavities on QMIP. Finally, QMIP was successfully used for the specific extraction of quercetin and five other flavonol and flavonoid compounds in the crude extracts from Sapium sebiferum. This study proposes a new strategy to synthesize the molecularly imprinted polymer based on a single template for enriching and loading a certain class of active ingredients with similar core structures from variable botanicals.

Fe-based MOFs as promising adsorbents and photocatalysts for re-use water contained arsenic: Strategies and challenges

Arsenic (As) contaminated water, especially groundwater reservoirs, is a major issue worldwide owing to its hazardous consequences on human health and the global environment issues. Also, irrigating agricultural fields with As-contaminated water not only produces an accumulation of As in the soil but also compromises food safety due to As entering into agricultural products. Hence, there is an urgent need to develop an efficient method for As removal in water. Fe-based MOFs have attained special attention due to their low toxicity, high water stability, better physical and chemical properties, and high abundance of iron. The arsenic species removal by Fe-MOF follows the adsorption and oxidation mechanism where As (III) converts into As (V). Moreover, the adsorption mechanism is facilitated by electrostatic interactions, H-bonding, acid-base interaction, hydrophobic interactions, van der Waals forces, π-π stacking interactions, and coordinative bindings responsible for Fe-O-As bond generation. This review thoroughly recapitulates and analyses recent advancements in the facile synthesis and potential application of Fe-based MOF adsorbents for the elimination of As ions. The most commonly employed hydro/solvothermal, ultrasonic, microwave-assisted, mechanochemical, and electrochemical synthesis for Fe-MOF has been discussed along with their adsorptive and oxidative mechanisms involved in arsenic removal. The effects of factors like pH and coexisting ions have also been discussed. Lastly, the article also proposed the prospects for developing the application of Fe-based MOF in treating As-contaminated water.

Effective removal of acetamiprid and eosin Y by adsorption on pristine and modified MIL-101(Fe)

In this work, the efficacy of two metal-organic frameworks (MIL-101(Fe) and NH2-MIL-101(Fe)) in eliminating acetamiprid (ATP) insecticide and eosin Y (EY) dye from aqueous solution is tested. An analysis was conducted on the developed nanocomposite's optical, morphological, and structural characteristics. The adsorption isotherm, kinetics, thermodynamics, reusability, and mechanisms for ATP and EY dye removal were assessed. NH2-MIL-101(Fe) adsorbed 76% and 90% of ATP pesticide and EY dye, respectively after 10 to 15 min in optimum conditions. For both adsorbents, with regard to explaining the isotherm data, the Langmuir model offered the most accurate description. Moreover, the adsorption of ATP and EY dye is described by the pseudo-second-order kinetic model. The maximum adsorption capacities of ATP and EY dye on MIL-101(Fe) were 57.6 and 48.9 mg/g compared to 70.5 and 97.8 mg/g using NH2-MIL-101(Fe). The greatest amount of ATP and EY dye clearance was obtained at a neutral medium for both adsorbents. The results of this investigation demonstrate the effectiveness of MIL-101(Fe) and NH2-MIL-101(Fe) as effective substances in the adsorption process for removing pesticides and dyes from aqueous solution.

Design and application of metal organic frameworks for heavy metals adsorption in water: a review

The growing apprehension surrounding heavy metal pollution in both environmental and industrial contexts has spurred extensive research into adsorption materials aimed at efficient remediation. Among these materials, Metal-Organic Frameworks (MOFs) have risen as versatile and promising contenders due to their adjustable properties, expansive surface areas, and sustainable characteristics, compared to traditional options like activated carbon and zeolites. This exhaustive review delves into the synthesis techniques, structural diversity, and adsorption capabilities of MOFs for the effective removal of heavy metals. The article explores the evolution of MOF design and fabrication methods, highlighting pivotal parameters influencing their adsorption performance, such as pore size, surface area, and the presence of functional groups. In this perspective review, a thorough analysis of various MOFs is presented, emphasizing the crucial role of ligands and metal nodes in adapting MOF properties for heavy metal removal. Moreover, the review delves into recent advancements in MOF-based composites and hybrid materials, shedding light on their heightened adsorption capacities, recyclability, and potential for regeneration. Challenges for optimization, regeneration efficiency and minimizing costs for large-scale applications are discussed.

Nanoconfinement boosts affinity of hydrated zirconium oxides to arsenate: Surface complexation modeling study

Nanoscale hydrated zirconium oxide (HZO) holds great potential in groundwater purification due to its ability to form inner-sphere coordination with arsenate. Despite being frequently used, especially as encapsulations in host materials for practical application in water treatment, the adsorption mechanisms of solutes on HZO are not appropriately explored, in particular for arsenate adsorption. In this study, we investigated the Zr-As coordination configuration and identified the most credible Zr-As configuration using surface complexation modeling (SCM), XPS and FT-IR analysis. The corresponding intrinsic coordination constants (Kintr) values was calculated by SCM, and the nanoconfinement effects were distinguished by comparing bare HZO with the HZO nanoparticles (NPs) encapsulated inside the strongly basic anion exchanger D201. Potentiometric titration suggests that the surface Zirconium hydroxyl groups (≡ZrOH) mainly exist in protonated form (≡ZrOH2+). Batch adsorption experiments demonstrate that the D201 hosts could adsorb As(V) through ion exchange by the quaternary ammonium groups under the low ionic strength (≤0.01 M NaNO3) and at pH > 6. The nanocomposite (HZO@D201) exhibits a higher adsorption capacity in a wide range of pH (3-10) and ionic strength (0.001-0.1 M NaNO3) than bare HZO. SCM simulations reveal that the coordination configuration of diprotonated monodentate mononuclear (MM-H2) dominates at pH 3-6, while deprotonated bidentate binuclear (BB-H0) dominates at pH > 7. For each configuration, the intrinsic coordination constants (Kintr) of HZO@D201 (10-0.66 and 10-16.10, respectively) are significantly higher than those of bare HZO (10-12.24 and 10-44.42, respectively), indicating a superior chemical bonding affinity caused by nanoconfinement. The obtained Kintr values are used to predict arsenate adsorption isotherms in pH 3 and 9, and the results align with the SCM simulation outcomes. This study may offer a feasible method for investigating the nanoconfinement effect of emerging nanocomposite adsorbents from a thermodynamic perspective, and provide reference coordination equilibrium constants of HZO for research and practical application.

Water-stable metal-organic frameworks (MOFs): rational construction and carbon dioxide capture

Metal-organic frameworks (MOFs) are considered to be a promising porous material due to their excellent porosity and chemical tailorability. However, due to the relatively weak strength of coordination bonds, the stability (e.g., water stability) of MOFs is usually poor, which severely inhibits their practical applications. To prepare water-stable MOFs, several important strategies such as increasing the bonding strength of building units and introducing hydrophobic units have been proposed, and many MOFs with excellent water stability have been prepared. Carbon dioxide not only causes a range of climate and health problems but also is a by-product of some important chemicals (e.g., natural gas). Due to their excellent adsorption performances, MOFs are considered as a promising adsorbent that can capture carbon dioxide efficiently and energetically, and many water-stable MOFs have been used to capture carbon dioxide in various scenarios, including flue gas decarbonization, direct air capture, and purified crude natural gas. In this review, we first introduce the design and synthesis of water-stable MOFs and then describe their applications in carbon dioxide capture, and finally provide some personal comments on the challenges facing these areas.

Adsorption behavior and mechanism of modified Fe-based metal-organic framework for different kinds of arsenic pollutants

Arsenic in water environment can present significant threats to human health, and eliminating arsenic pollutants from wastewater is crucial. Based on our previously reported work, this study delved into the adsorption behavior and mechanism of different arsenic contaminants (p-ASA, ROX, As(V), and DMA) on the activated Fe-based metal-organic framework (activated MIL-88A). The results show that activated MIL-88A exhibits exceptional adsorption capabilities toward diverse arsenic pollutants. The adsorption process is endothermic, spontaneous, and viable, and chemical adsorption plays a leading role. The remarkable adsorption capacity of activated MIL-88A to various arsenic pollutants is primarily attributed to coordination, while hydrogen bonding also assumes a significant role in the elimination of p-ASA and ROX. Additionally, we investigated the impact of arsenic molecule shape and size, solution pH, and the existence of specific anions and dissolved organic matter (DOM) on the adsorption of different arsenic pollutants. This study can provide valuable insights for further exploring the selective adsorption of different kinds of arsenic species by Fe-based MOF materials and improving the adsorption efficiency of MOFs.

PolyMOF nanoparticles constructed from intrinsically microporous polymer ligand towards scalable composite membranes for CO2 separation

Integrating different modification strategies into a single step to achieve the desired properties of metal-organic frameworks (MOFs) has been very synthetically challenging, especially in developing advanced MOF/polymer mixed matrix membranes (MMMs). Herein, we report a polymer-MOF (polyMOF) system constructed from a carboxylated polymer with intrinsic microporosity (cPIM-1) ligand. This intrinsically microporous ligand could coordinate with metals, leading to ~100 nm-sized polyMOF nanoparticles. Compared to control MOFs, these polyMOFs exhibit enhanced ultramicroporosity for efficient molecular sieving, and they have better dispersion properties in casting solutions to prepare MMMs. Ultimately, integrating coordination chemistries through the cPIM-1 and polymer-based functionality into porous materials results in polyMOF/PIM-1 MMMs that display excellent CO2 separation performance (surpassing the CO2/N2 and CO2/CH4 upper bounds). In addition to exploring the physicochemical and transport properties of this polyMOF system, scalability has been demonstrated by converting the developed MMM material into large-area (400 cm2) thin-film nanocomposite (TFN) membranes.

Prediction of arsenic adsorption onto metal organic frameworks and adsorption mechanisms interpretation by machine learning

Metal-organic frameworks (MOFs) are promising adsorbents for the removal of arsenic (As) from wastewater. The As removal efficiency is influenced by several factors, such as the textural properties of MOFs, adsorption conditions, and As species. Examining all of the relevant factors through traditional experiments is challenging. To predict the As adsorption capacities of MOFs toward organic, inorganic, and total As and reveal the adsorption mechanisms, four machine learning-based models were developed, with the adsorption conditions, MOF properties, and characteristics of different As species as inputs. The results demonstrated that the extreme gradient boosting (XGBoost) model exhibited the best predictive performance (test R2 = 0.93-0.96). The validation experiments demonstrated the high accuracy of the inorganic As-based XGBoost model. The feature importance analysis showed that the concentration of As, the surface area of MOFs, and the pH of the solution were the three key factors governing inorganic-As adsorption, while those governing organic-As adsorption were the concentration of As, the pHpzc value of MOFs, and the oxidation state of the metal clusters. The formation of coordination complexes between As and MOFs is possibly the major adsorption mechanism for both inorganic and organic As. However, electrostatic interaction may have a greater effect on organic-As adsorption than on inorganic-As adsorption. Overall, this study provides a new strategy for evaluating As adsorption on MOFs and discovering the underlying decisive factors and adsorption mechanisms, thereby facilitating the investigation of As wastewater treatment.

MIL-101(Fe)/WS2 composites activated Na2S2O8 with visible light for removal of tetracycline

MIL-101(Fe)/WS2 catalyst was composited using a solvothermal method. To study the physical and chemical properties of the composite material, a series of characterizations such as scanning electron microscope (SEM), X-ray diffraction (XRD), and catalytic experiments were carried out. The photocatalysis of the prepared catalyst in the degradation of tetracycline was investigated using persulfate (PS, Na2S2O8) as a cocatalyst under visible light illumination. The above system can remove about 80% of tetracycline within 40 min. After three cyclic experiments, the material showed good recycling. According to material characterization and various experimental results, the enhanced performance of the material was attributed to the reduction of the recombination efficiency of photogenerated e- and h+, and activated persulfate to produce a large number of free radicals such as O2•-, SO4•- and 1O2 produced by the active sites provided by the catalyst's high specific surface area.

3D-Printed MOFs/Polymer Composite as a Separatable Adsorbent for the Removal of Phenylarsenic Acid in the Aqueous Solution

Metal-organic frameworks (MOFs) are emerging as advanced nanoporous materials to remove phenylarsenic acid, p-arsanilic acid (p-ASA), and roxarsone (ROX) in the aqueous solution, while MOFs are often present as powder state and encounter difficulties in recovery after adsorption, which greatly limit their practical application in the aqueous environments. Herein, MIL-101 (Fe), a typical MOF, was mixed with sodium alginate and gelatin to prepare MIL-101@CAGE by three-dimensional (3D) printing technology, which was then used as a separatable adsorbent to remove phenylarsenic acid in the aqueous solution. The structure of 3D-printed MIL-101@CAGE was first characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR), and thermogravimetry and differential thermogravimetry (TG-DTG). The octahedral morphology of MIL-101 (Fe) was found unchanged during the 3D printing process. Then, the adsorption process of MIL-101@CAGE on phenylarsenic acids was systematically investigated by adsorption kinetics, adsorption isotherms, adsorption thermodynamics, condition experiments, and cyclic regeneration experiments. Finally, the adsorption mechanism between MIL-101@CAGE and phenylarsenic acid was further investigated. The results showed that the Langmuir, Freundlich, and Temkin isotherms were well fit, and according to the Langmuir fitting results, the maximum adsorption amounts of MIL-101@CAGE on p-ASA and ROX at 25 °C were 106.98 and 120.28 mg/g, respectively. The removal of p-ASA and ROX by MIL-101@CAGE remained stable over a wide pH range and in the presence of various coexisting ions. The regeneration experiments showed that the 3D-printed MIL-101@CAGE could still maintain a more than 90% removal rate after five cycles. The adsorption mechanism of this system might include π-π stacking interactions between the benzene ring on the phenylarsenic acids and the organic ligands in MIL-101@CAGE, hydrogen-bonding, and ligand-bonding interactions (Fe-O-As). This study provides a new idea for the scale preparation of a separatable and recyclable adsorbent based on MOF material for the efficient removal of phenylarsenic acid in the aqueous solution.

Sodium-alginate-laden MXene and MOF systems and their composite hydrogel beads for batch and fixed-bed adsorption of naproxen with electrochemical regeneration

Sodium alginate (SA)-laden two-dimensional (2D) Ti3C2Tx MXene (MX) and MIL-101(Fe) (a type of metal-organic framework (MOF)) composites were prepared and used for the removal of naproxen (NPX), following the adsorption and electrochemical regeneration processes. The fixed-bed adsorption column studies were also conducted to study the process of removal of NPX by hydrogels. The number of interactions via which the MX-embedded SA (MX@SA) could adsorb NPX was higher than the number of pathways associated with NPX adsorption on the MIL-101(Fe)-embedded SA (MIL-101(Fe)@SA), and the MX and MIL-101(Fe) composite embedded SA (MX/MIL-101(Fe)@SA). The optimum parameters for the electrochemical regeneration process were determined: charge passed and current density values were 169.3 C g-1 and 10 mA cm-2, respectively, for MX@SA, and the charge passed and current density values were 16.7 C g-1 and 5 mA cm-2, respectively, for both MIL-101(Fe)@SA and MX/MIL-101(Fe)@SA. These parameters enabled excellent regeneration, consistent over multiple adsorption and electrochemical regeneration cycles. The mechanism for the regeneration of the materials was proposed that the regeneration of MX@SA and MIL-101(Fe)@SA involved the indirect electrooxidation process in the presence of OH radicals, and the regeneration of MX/MIL-101(Fe)@SA involved the indirect oxidation process in the presence of active chlorine species.

Current advances in the detection and removal of organic arsenic by metal-organic frameworks

Arsenic (As) is a highly toxic heavy metal and has been widely concerned for its hazardous environmental impact. Aromatic organic arsenic (AOCs) has been frequently used as an animal supplement to enhance feed utilization and prevent dysentery. The majority of organic arsenic could be discharged from the body and evolve as highly toxic inorganic arsenic that is hazardous to the environment and human health via biological conversion, photodegradation, and photo-oxidation. Current environmental issues necessitate the development and application of multifunctional porous materials in environmental remediation. Compared to the conventional adsorbent, such as activated carbon and zeolite, metal-organic frameworks (MOFs) exhibit a number of advantages, including simple synthesis, wide variety, simple modulation of pore size, large specific surface area, excellent chemical stability, and easy modification. In recent years, numerous scientists have investigated MOFs related materials involved with organic arsenic. These studies can be divided into three categories: detection of organic arsenic by MOFs, adsorption to remove organic arsenic by MOFs, and catalytic removal of organic arsenic by MOFs. Here, we conduct a critical analysis of current research findings and knowledge pertaining to the structural characteristics, application methods, removal properties, interaction mechanisms, and spectral analysis of MOFs. We summarized the application of MOFs in organic arsenic detection, adsorption, and catalytic degradation. Other arsenic removal technologies and conventional substances are also being investigated. This review will provide relevant scientific researchers with references.

A cage-on-MOF strategy to coordinatively functionalize mesoporous MOFs for manipulating selectivity in adsorption and catalysis

Functionalizing porous materials with capping agents generates hybrid materials with enhanced properties, while the challenge is how to improve the selectivity and maintain the porosity of the parent framework. Herein, we developed a "Cage-on-MOF" strategy to tune the recognition and catalytic properties of MOFs without impairing their porosity. Two types of porous coordination cages (PCCs) of opposite charges containing secondary binding groups were developed to coordinatively functionalize two distinct porous MOFs, namely MOF@PCC nanocomposites. We demonstrated that the surface-capped PCCs can act as "modulators" to effectively tune the surface charge, stability, and adsorption behavior of different host MOF particles. More importantly, the MOF@PCCs can serve as selective heterogeneous catalysts for condensation reactions to achieve reversed product selectivity and excellent recyclability. This work sets the foundation for using molecular cages as porous surface-capping agents to functionalize and manipulate another porous material, without affecting the intrinsic properties of the parent framework.

A magnetic porous carbon material derived from an MIL-101(Fe) complex for efficient magnetic solid phase extraction of fluoroquinolone antibiotics

Extraction and determination of trace hazardous components from complex matrices continue to attract public attention. In this work, magnetic porous carbon (MPC) was prepared for efficient magnetic solid phase extraction (MSPE) of fluoroquinolone (FQ) antibiotics in food and water samples. To prepare the MPC, an Fe-based metal-organic framework (MIL-101(Fe)) was grown on a network of graphene oxide and multi-walled carbon nanotubes through a hydrothermal method, and then a carbonization process under a nitrogen atmosphere was carried out to obtain the MPC with high specific surface area and good magnetism. Four target FQs including ciprofloxacin (CIP), enrofloxacin (ENO), lomefloxacin (LOM) and ofloxacin (OFX) were enriched using the as-prepared MPC and determined by coupled high-performance liquid chromatography. Under the optimal conditions, the established MSPE-HPLC-UV detection method exhibited a linear range of 0.5-800 μg L-1 and detection limits of 0.11-0.18 μg L-1 with relative standard deviations (RSDs) of 0.5-4.8%. When applied in the determination of the above four FQs in real samples such as lake water, milk and pork, good recoveries between 85.2 and 103.7% were obtained, and the RSDs were less than 4.8%. This work indicates that the MPC material can be a good adsorption material and has good application prospects in antibiotics enrichment and/or removal from complex samples.

Construction of hexagonal spindle-shaped Fe-MOFs induced by cationic copolymer and its application for effective wastewater treatment

The environment and human health are in danger due to the long-term enrichment and buildup of organic pesticides, dyes, and harmful microbes in wastewater. The development of functional materials that are efficient for treating wastewater remains a significant problem. Eco-friendly hexagonal spindle-shaped Fe-MOFs (Hs-FeMOFs) were created in this study under the influence of cationic copolymer (PMSt). The mechanism of crystal growth and development of its unique morphology were described after looking into impact factors for the ideal circumstances and being characterized by XRD, TEM, XPS, and other techniques. It revealed that Hs-FeMOFs possess an enormous supply of adsorption active sites, a strong electropositivity, and the nanometer tip. Then, typical organic pollutants, such as herbicides and mixed dyes, as well as biological pollutants bacteria, were chosen to assess its efficacy in wastewater treatment. It was discovered that the pendimethalin could be quickly removed in wastewater and the removal rate reached 100% within 10 min. In separation of mixed dyes, the retention rate of malachite green (MG) reached 92.3% in 5 min and with a minimum inhibitory concentration of 0.8 mg/mL and demonstrated strong activity due to the presence of cationic copolymers. In actual water matrix, Hs-FeMOF could also play excellent adsorption and antibacterial activity. In summary, a novel, environmentally friendly MOF material with good activity was successfully created by cationic copolymer induction. It offers a fresh approach to develop functional materials in wastewater treatment.

Fe-Cu bimetal metal-organic framework for efficient decontamination via Fenton-like process: Synthesis, performance and mechanism

Constructing Fe-Cu bimetal catalysts is an efficient strategy to promote Fe(III)/Fe(II) cycle, whereas there is still a long way to go before fully understanding the role of the Cu in the catalysts. Herein, a new Fe-MOF namely BUC-96(Fe) was fabricated from FeSO₄·7H₂O, 4,4'-bipyridine (bpy) and 2,5-dihydroxyterephthalic acid (H₄dhtp) by both hydrothermal reaction and microwave-assisted method. Also, bimetal BUC-96(FeCu-x) were obtained when the CuSO₄ was added into the system identical to the synthesis process of BUC-96(Fe). Series BUC-96 MOFs showed good organics elimination performance via Fenton-like process, where 88.1% (k = 0.0672 min^-1) of chloroquine phosphate (CQ, 20 mg/L) was decomposed over pristine BUC-96(Fe) within 30 min. Interestingly, nearly 100% CQ was degraded over BUC-96(FeCu-5) as catalyst under the identical conditions within 5 min, whose reaction rate (1.3527 min^-1) was 20.1-fold higher than that of BUC-96. Additionally, BUC-96(FeCu-5) exhibited excellent Fenton-like oxidation degradation performance for 10 selected emerging organic pollutants. The reaction mechanism was studied in detail by experiments, and density functional theory (DFT) calculation. The results revealed that the introduced Cu not only accelerated Fe(III)/Fe(II) cycles, hydroxyl radical (·OH) generation, electron transfer, but also lowered H₂O₂ dissociated energy barrier. This work advanced the bimetal MOFs construction and application in wastewater treatment via Fenton-like process.

Facile fabrication of Fe/Zr binary MOFs for arsenic removal in water: High capacity, fast kinetics and good reusability

A water-stable bimetallic Fe/Zr metal-organic framework [UiO-66(Fe/Zr)] for exceptional decontamination of arsenic in water was fabricated through a facile one-step strategy. The batch adsorption experiments revealed the excellent performances with ultrafast adsorption kinetics due to the synergistic effects of two functional centers and large surface area (498.33 m²/g). The absorption capacity of UiO-66(Fe/Zr) for arsenate [As(V)] and arsenite [As(III)] reached as high as 204.1 mg/g and 101.7 mg/g, respectively. Langmuir model was suitable to describe the adsorption behaviors of arsenic on UiO-66(Fe/Zr). The fast kinetics (adsorption equilibrium in 30 min, 10 mg/L As) and pseudo-second-order model implied the strong chemisorption between arsenic ions and UiO-66(Fe/Zr), which was further confirmed by DFT theoretical calculations. The results of FT-IR, XPS analysis and TCLP test demonstrated that arsenic was immobilized on the surface of UiO-66(Fe/Zr) through Fe/Zr-O-As bonds, and the leaching rates of the adsorbed As(III) and As(V) from the spent adsorbent were only 5.6% and 1.4%, respectively. UiO-66(Fe/Zr) can be regenerated for five cycles without obvious removal efficiency decrease. The original arsenic (1.0 mg/L) in lake and tap water was effectively removed in 2.0 hr [99.0% of As(III) and 99.8% of As(V)]. The bimetallic UiO-66(Fe/Zr) has great potentials in water deep purification of arsenic with fast kinetics and high capacity.

Arsenic removal and stabilization behavior of schwertmannite@BC (Sch@BC) in contaminated dual media (water/soil): Via sulfate exchange and chemical complexation

Arsenic (As) is extremely harmful to the ecological environment and human health owing to its high toxicity. The composite that biochar (BC) modified by Schwertmannite (Sch), marked as Sch@BC, were prepared to remediate As-contaminated water and soil with a high efficiency. The characterization results showed that the Sch particles were successfully loaded on the BC, providing more active sites for As(V) adsorption. Compared with the pristine BC, the adsorption capacity of Sch@BC-1 was significantly improved (50.00 mg/g), of which the adsorption capacity kept stable over a wide pH range (pH = 2-8). The adsorption process conformed to pseudo-second-order kinetics and Langmuir isotherm model, which indicated that chemical adsorption was the dominant mechanism and the adsorption rate was controlled by intraparticle diffusion. Sch@BC could adsorb As(V) through electrostatic interaction and ion exchange, forming a FeAsO₄ complex and removing As(V). The 5-week soil incubation experiment showed that 3% Sch@BC showed the optimal stabilization effect, while the proportion of stable crystalline Fe/Mn-bound fractionation (F4) increased. Moreover, the results of microbial community diversity showed that Sch@BC interacted with As-resistant dominant microorganisms such as Proteobacteria in soil, promoted their growth and reproduction, and improved the stability of As in soil. In summary, Sch@BC is an excellent agent with broad application prospects for remediating As-contaminated water and soil.

Synthesis of PMIA/MIL-101(Cr) composite separators with high Li+ transmission for boosting safety and electrochemical performance of lithium-ion batteries

Energy storage devices require separators with sufficient lithium-ion transfer and restrained lithium dendrite growth. Herein, PMIA separators tuned using MIL-101(Cr) (PMIA/MIL-101) were designed and fabricated by a one-step casting process. At 150 °C, the Cr³⁺ in the MIL-101(Cr) framework sheds two water molecules to form an active metal site that complexes with PF₆^- in the electrolyte on the solid/liquid interface, leading to improved Li⁺ transport. The Li⁺ transference number of the PMIA/MIL-101 composite separator was found to be 0.65, which is about 3 times higher than that of the pure PMIA separator (0.23). Additionally, MIL-101(Cr) can modulate the pore size and porosity of the PMIA separator, while its porous structure also functions as additional storage space for the electrolyte, enhancing the electrochemical performance of the PMIA separator. After 50 charge/discharge cycles, batteries assembled using the PMIA/MIL-101 composite separator and the PMIA separator presented a discharge specific capacity of 120.4 and 108.6 mAh/g, respectively. The battery assembled using PMIA/MIL-101 composite separator significantly outperformed both the batteries assembled from pure PMIA and commercial PP separators in terms of cycling performance at 2 C, displaying a discharge specific capacity of 1.5 times that of the battery assembled from PP separators. The chemical complexation of Cr³⁺ and PF₆^- plays a critical role to improve the electrochemical performance of the PMIA/MIL-101 composite separator. The tunability and enhanced properties of the PMIA/MIL-101 composite separator make it a promising candidate for use in energy storage devices.

Review on arsenic environment behaviors in aqueous solution and soil

Arsenic pollution in environment has always been an important environmental problem that has attracted wide attention in recent years. Adsorption is one of the main methods of treatment for arsenic in the aqueous solution and soil because of the advantages of high efficiency, low cost and wide application. Firstly, this report summarizes the commonly and widely used adsorbent materials such as metal-organic frameworks, layered bimetallic hydroxides, chitosan, biochar and their derivatives. The adsorption effects and mechanisms of these materials are further discussed, and the application prospects of these adsorbents are considered. Meanwhile, the gaps and deficiencies in the study of adsorption mechanism was pointed out. Then, this study comprehensively evaluated the effects of various factors on arsenic transport, including (i) the effects of pH and redox potential on the existing form of As; (ii) complexation mechanism of dissolved organic matter and As; (iii) factors affecting the plant enrichment of As. Finally, the latest scientific researches on microbial remediation of arsenic and the mechanisms were summarized. The review finally enlightens the subsequent development of more efficient and practical adsorption material.

Enhanced degradation of tetracycline under natural sunlight through the synergistic effect of Ag3PO4/MIL-101(Fe) photocatalysis and Fenton catalysis: Mechanism, pathway, and toxicity assessment

Here, we show that the adverse environmental and health effects of tetracycline (TC) can be efficiently reduced by encapsulating Ag₃PO₄ into MIL-101(Fe) to construct a Ag₃PO₄/MIL-101(Fe) heterojunction composite through advanced oxidation processes, such as Fenton catalysis, photocatalysis, and photo-Fenton catalysis. Notably, the reaction can be driven by natural sunlight and does not require any artificial energy source. Remarkably, the optimal degradation of TC can be achieved under different compositions of the composite system through photocatalysis and photo-Fenton catalysis. For photo-Fenton catalysis, the maximum degradation rate of TC (2.5730 min^-1) is achieved when the mass ratio of MIL-101(Fe) to Ag₃PO₄ in the composite is 5:1, which is 31.65- and 3.12-fold of that in the Ag₃PO₄ + PDS + Sunlight and MIL-101(Fe) + PDS+ Sunlight catalyst systems, respectively. Moreover, the internal conversion of matrix during photocatalysis and Fenton catalysis processes inhibits the photocorrosion of Ag₃PO₄ and improves the reusability of the composite. Furthermore, it is found that both radical and non-radical species participate in the TC degradation. Besides, the degradation products and catalytic mechanism of Ag₃PO₄ and Ag₃PO₄/MIL-101(Fe) systems are explored. The toxicity evaluation results suggest that the intermediates produced during Ag₃PO₄/MIL-101(Fe) catalysis have a lower biotoxicity than those produced during Ag₃PO₄ catalysis. Overall, this work provides an effective strategy to inhibit the inherent photocorrosion of Ag₃PO₄ and establishes an efficient catalytic system for the treatment of organic-contaminated wastewater under natural sunlight conditions.

Photo-aged non-biodegradable and biodegradable mulching film microplastics alter the interfacial behaviors between agricultural soil and inorganic arsenic

The impacts of microplastics (MPs) prevalent in soil on the transport of pollutants were urged to be addressed, which has important implications for ecological risk assessment. Therefore, we investigated the influence of virgin/photo-aged biodegradable polylactic acid (PLA) and non-biodegradable black polyethylene (BPE) mulching films MPs on arsenic (As) transport behaviors in agricultural soil. Results showed that both virgin PLA (VPLA) and aged PLA (APLA) enhanced the adsorption of As(Ⅲ) (9.5%, 13.3%) and As(Ⅴ) (22.0%, 6.8%) due to the formation of abundant H-bonds. Conversely, virgin BPE (VBPE) reduced the adsorption of As(Ⅲ) (11.0%) and As(Ⅴ) (7.4%) in soil owing to the "dilution effect", while aged BPE (ABPE) improved arsenic adsorption amount to the level of pure soil due to newly generated O-containing functional groups being feasible to form H-bonds with arsenic. Site energy distribution analysis indicated that the dominant adsorption mechanism of arsenic, chemisorption, was not impacted by MPs. The occurrence of biodegradable VPLA/APLA MPs rather than non-biodegradable VBPE/ABPE MPs resulted in an increased risk of soil accumulating As(Ⅲ) (moderate) and As(Ⅴ) (considerable). This work uncovers the role of biodegradable/non-biodegradable mulching film MPs in arsenic migration and potential risks in the soil ecosystem, depending on the types and aging of MPs.

Alkaline etched hydrochar-based magnetic adsorbents produced from pharmaceutical industry waste for organic dye removal

A large amount of pharmaceutical industry waste (PIW) was inevitably produced every year, and the PIW can be degraded by high temperature reaction to form porous structures. The study proposed an innovative pathway to valorize PIW with hydrothermal carbonization (HTC) coupled with alkali etching (AE). Without adding any additives, magnetic hydrochar could be generated with rough surface topography and suitable specific surface area (S_BET) by this method. Effects of HTC conditions and alkaline solution concentrations on the physicochemical and adsorption properties of PIW were investigated, and adsorption mechanism was explored. Based on evaluations of the magnetism, cyclic regeneration, and heavy metal leaching properties of the products, the feasibility of preparing magnetic adsorbents with solid waste by HTC coupled AE was established. The alkaline etching pharmaceutical industry waste (AEPIW) hydrochar showed the highest S_BET (54.64 m²/g) after the PIW was treated by 260 °C for 2 h plus 1 mol/L KOH. The removal rate of methylene blue (MB) could exceed 90% and the saturated magnetization was ~8 emu/g. The proposed new method was able to convert the low-value solid industrial waste into high-performance hydrochar-based magnetic adsorbents, which was tested to have a capability to efficiently and sustainably remove organic pollutants from water.

Simple Co-Precipitation of Iron Minerals for the Removal of Phenylarsonic Acid: Insights into the Adsorption Performance and Mechanism

In this study, three kinds of iron minerals, ferrihydrite, hematite, and goethite, were prepared by a simple coprecipitation method for the adsorption and removal of phenylarsonic acid (PAA). The adsorption of PAA was explored, and the influences of ambient temperature, pH, and co-existing anions on adsorption were evaluated. The experimental results show that rapid adsorption of PAA occurs within 180 min in the presence of iron minerals, and the adsorption process conforms to a pseudo-second-order kinetic model. The isothermal adsorption of PAA by ferrihydrite, goethite, and hematite agrees with the Redlich-Peterson model. The maximum adsorption capacities of PAA are 63.44 mg/g, 19.03 mg/g, and 26.27 mg/g for ferrihydrite, goethite, and hematite, respectively. Environmental factor experiments illustrated that an alkaline environment will significantly inhibit the adsorption of PAA by iron minerals. CO₃^2-, SiO₃^2-, and PO₄^3- in the environment will also significantly reduce the adsorption performance of the three iron minerals. The adsorption mechanism was analyzed by FTIR and XPS, which indicated that ligand exchange between the surface hydroxyl group and the arsine group leads to the formation of an Fe-O-As bond, and electrostatic attraction between the iron minerals and PAA played an important role in the adsorption.

Enhanced arsenite removal from water using zirconium-ferrocene MOFs coupled with peroxymonosulfate:oxidation and multi-sites adsorption mechanism

The efficient removal of arsenite (As(III)) poses a significant challenge to traditional water treatment technologies due to its high toxicity and mobility. In this work, multifunctional Zirconium-Ferrocene Metal Organic Framework (ZrFc-MOF) fabricated with redox-active 1,1-ferrocene dicarboxylic acid ligands and Zr⁴⁺ precursors were elaborated to achieve remarkably enhanced As(III) removal via activation by peroxymonosulfate (PMS). The adsorption affinity coefficient increased from 0.097 to 2.035 L mg^-1 and the maximum adsorption capacity increased from 59.79 to 111.34 mg g^-1 compared with that without PMS. Besides the conventional homogeneous PMS oxidation and the following adsorption through Zr-O clusters of ZrFc-MOFs, the enhanced As(III) removal synergistic combines the oxidation mechanism of As(III) by reactive oxygen species (•OH, SO₄^•-, O₂^•- and ¹O₂) formed in Ferrocene (Fc) activating PMS process with the simultaneous formed extra adsorption sites of Ferrocenium (Fc⁺). PMS also help ZrFc-MOF to avoid destruction in harsh alkaline condition, making the effluent in this advanced treatment meet the World Health Organization (WHO) threshold of 10 μg L^-1 over a wide range of initial pH (2-11) with high selectivity and durability. These results indicate that this novel Fc-based MOFs activating PMS system has potential applicability for As(III) in oxidation and selectively capturing in the water environment.

Application of infrared spectroscopy and its theoretical simulation to arsenic adsorption processes

Accurate detection and analysis of arsenic pollutants are an important means to enhance the ability to manage arsenic pollution. Infrared (IR) spectroscopy technology has the advantages of fast analysis speed, high resolution, and high sensitivity and can be monitored by real-time in situ analysis. This paper reviews the application of IR spectroscopy in the qualitative and quantitative analysis of inorganic and organic arsenic acid adsorbed by major minerals such as ferrihydrite (FH), hematite, goethite, and titanium dioxide. The IR spectroscopy technique cannot only identify different arsenic contaminants but also obtain the content and adsorption rate of arsenic contaminants in the solid phase. The reaction equilibrium constants and the degree of reaction conversion can be determined by constructing adsorption isotherms or combining them with modeling techniques. Theoretical calculations of IR spectra of mineral adsorbed arsenic pollutant systems based on density functional theory (DFT) and analysis and comparison of the measured and theoretically calculated characteristic peaks of IR spectra can reveal the microscopic mechanism and surface chemical morphology of the arsenic adsorption process. This paper systematically summarizes the qualitative and quantitative studies and theoretical calculations of IR spectroscopy in inorganic and organic arsenic pollutant adsorption systems, which provides new insights for accurate detection and analysis of arsenic pollutants and arsenic pollution control. PRACTITIONER POINTS: This paper reviews the application of infrared spectroscopy in the qualitative and quantitative analyses of inorganic and organic arsenic acid adsorbed by major minerals such as ferrihydrite, hematite, goethite, and titanium dioxide, which can help identify and evaluate the type and concentration of arsenic pollutants in water bodies. In this paper, theoretical calculations of infrared spectra of mineral adsorbed arsenic pollutant systems based on density functional theory reveal the adsorption mechanism of arsenic pollutants in water at the solid-liquid interface and help to develop targeted arsenic pollution control technologies. This paper provides a new and reliable analytical detection technique for the study of arsenic contaminants in water bodies.

Fabrication of a metal organic framework (MOF)-modified Au nanoparticle array for sensitive and stable SERS sensing of paraquat in cereals

A high-performance Au@MIL-101/PMMA/DT surface-enhanced Raman scattering (SERS) substrate was fabricated for sensitive and stable detection of paraquat by self-assembling metal organic framework-modified Au nanoparticles (Au@MIL-101) on a poly(methyl methacrylate) (PMMA) film and then immobilizing the formed substrate onto a duct tape (DT). The highly closely packed Au@MIL-101 array provided intensive hotspots for SERS sensing. The MIL-101 layer modified on the surface of Au nanoparticles could absorb paraquat to the electromagnetic enhancement area of Au nanoparticles. The DT on the bottom made the substrate smoother, which is beneficial for achieving a more stable detection performance. As a result, the constructed substrate exhibited outstanding uniformity with relative standard deviations of 9.47% and storage stability for 2 months. For detecting paraquat, the substrate showed a low detection limit of 7.1 × 10^-9  M (1.83 µg/kg) and wide linear range from 10^-8 to 10^-2  M. Furthermore, the substrate showed good detection performance in real cereal samples with desirable recovery rates from 91.57% to 102.32%.

The effects of UiO-66 ultrafine particles on the rapid detection of sulfonamides in milk: Adsorption performance and mechanism

Nanoscale MOFs particles possess both excellent adsorption and dispersion properties. In this study, ultrafine particles UiO-66 (UP/UiO-66) with a particle size below 50 nm were synthesised by a template-controlled method. UP/UiO-66 was able to achieve a maximum adsorption capacity of 139.64 mg/g for 5 methoxylated sulfonamides. Adsorption studies showed that UP/UiO-66 adsorption of sulfonamides can be classified as a pseudo-secondary kinetic adsorption model for single molecular layer adsorption. ELISA (validated by Raman and molecular docking) showed that the sulfonamide molecule was still immunoreactive with antibodies after adsorption by UP/UiO-66. In 15 min, UP/UiO-66 could be used directly in the ELISA test for sulfonamides in milk without elution and separation. The LOQ (IC₂₀) of UP/UiO-66-ELISA for sulfonamides in milk was 0.21-2.05 ng/mL. The ultrafine particle strategy of UiO-66 is expected to be applied to other MOFs and used as a general pretreatment material for residue monitoring in complex matrices.

Characterizing spatial dependence of boron, arsenic, and other trace elements for Permian groundwater in Northern Anhui plain coal mining area, China, using spatial autocorrelation index and geostatistics

Anthropogenic and geological factors play an essential role in the variability of groundwater quality, resulting in a weak spatial dependence of groundwater trace elements. Thus, it is an essential study to investigate the factors affecting groundwater quality and its spatial abundance of trace elements (including As, B, and other metalloids). In this study, samples are obtained from a Permian sandstone fracture aquifer in a coal mining area. A multivariate statistical analysis, hydrogeochemistry modeling, and spatial autocorrelation analysis were used to analyze the data. The results showed that Moran index was positive for all trace elements, which had good spatial autocorrelation. The Local indicators of spatial association (LISA) indicated that trace elements were clustered. The hydrogeochemical modeling results indicated that the precipitation and stability of iron-phase minerals, such as rhodochrosite and arsenic (As) absorption on the surface of iron-phase minerals in the aquifer, may limit concentrations in the southern region. The spatial autocorrelations of both As and Boron (B) were positive (high-high) in the western areas, indicating that As contamination occurred from both natural geological causes and human coal mining activities. In contrast, B contamination was mainly linked to the influence of human agricultural or industrial activities. Over 96% of the groundwater concentrations of As (10 μg/L) and B (300 μg/L) in the study area exceeded World Health Organization (WHO) limits. Overall, the results of this work could help decision-makers involved in regional water quality management visualize disperse zones where specific anthropogenic and geological processes may threaten groundwater quality.

Synthesis and physicochemical evaluations of a novel MIL-101(Fe)-PMA-Biochar triple composite photocatalyst activated through visible-light and utilized toward degradation of organic pollutants: optimal operations and kinetics investigations

A triple photocatalytic composite of biochar, metal-organic framework, and phosphomolybdic acid was prepared through hydrothermal treatment of iron (III) chloride hexahydrate, terephthalic acid, lavandulifolia-derived biochar, and phosphomolybdic acid. It was characterized and utilized for photodegradation of Rhodamine-B (RhB) dye under visible-light irradiation. Investigations of reaction variables confirmed that, the highest yield of 96.2% was achieved at ambient temperature using 0.07 g of catalyst at pH of 7, and a dye concentration of 10 ppm. Under these optimum conditions, Methyl Orange (MO) dye was also degraded to yield 93% removal. In addition, the kinetic and thermodynamic parameters for RhB were determined. It was revealed that the photodegradation of RhB followed a pseudo-first-order kinetics with no mass transfer limitations. A corresponding chemical mechanism for this process was also suggested. Adsorption isotherms were investigated for rate of adsorption as well as adsorption capacity of the catalyst under dark conditions. Notably, the catalyst could have been reused for five cycles with a loss of around 20% activity.

Efficient wastewater disinfection by raised 1O2 yield through enhanced electron transfer and intersystem crossing via photocatalysis of peroxymonosulfate with CuS quantum dots modified MIL-101(Fe)

Peroxymonosulfate (PMS)-based photocatalysis is a promising alternative approach for wastewater disinfection. Singlet oxygen (¹O₂) is sensitive and efficient for bacterial inactivation. This study developed a ¹O₂-predominated PMS disinfection technique under visible light with CuS quantum dots (QDs) modified MIL-101(Fe) (CSQDs@MF). CuS QDs modification greatly enhanced the ¹O₂ quantum yield by 80% than that of MIL-101(Fe). Photoelectricity and photoluminescence tests demonstrated that both the enhanced electron transfer and energy transfer were responsible for improved ¹O₂ generation in Vis/PMS/CSQDs@MF system. The system took 60 min to inactivate 7.5-log E. coli, and it could be applied in a broad pH and dissolve oxygen range. Bacterial inactivation mechanism suggested that ¹O₂ attacked cell membrane first, then induced oxidative stress, up-regulated intracellular ROS level, eventually broke DNA strand. The system showed good disinfection performance on Gram-positive B. subtilis and fecal coliforms in practical wastewater, implying it is a promising alternative disinfection technology for wastewater treatment.

Boosting electron transport process over multiple channels induced by S-doped carbon and Fe7S8 NPs interface toward high-efficiency antibiotics removal

The enhancement of electron transport process on multiple channels of C-Fe and C-S-Fe bonds between dual-reaction centres was investigated for stimulating the antibiotics degradation in Fenton-like processes. Herein, multiple channels structure of sulfur-doped carbon coupled Fe₇S₈ cluster through C-Fe bond and C-S-Fe bond was constructed through density functional theory (DFT), and S-doped carbon framework coated Fe₇S₈ nanoparticles (Fe₇S₈/SC) Fenton-like catalyst was prepared through hydrothermal and subsequent sulfuration process. The DFT calculations revealed that electrons are thermodynamically transferred from carbon to iron along both C-Fe and C-S-Fe bonds. The optimized Fe₇S₈/SC catalyst exhibited desirable catalytic property for Fenton-like degradation for various antibiotics, the removal of amoxicillin, norfloxacin, and tetracycline hydrochloride reach 98.9%, 97.8%, and 99.3% respectively within 40 min under neutral pH, and catalyst also demonstrated excellent cycle stability after five runs. The excellent degradation effect of antibiotics by Fenton-like catalyst was attributed to the intensified electron transport process by multiple electron transfer channels between dual reaction centres, making Fe^II easier to regenerate. This study spreads a new route for the enhancement of electron transport process in Fenton-like catalysts by constructing multiple channels.

The interfacial behaviors of different arsenic species on polyethylene mulching film microplastics: Roles of the plastic additives

Plastic additives widely existed in plastic mulching films, but their roles in microplastics (MPs) derived from these plastics as vectors of pollutants were not clear. This work clarified the role of plastic additives on the sorption-desorption behaviors of four arsenic species (arsenite (As(Ⅲ)), arsenate (As(Ⅴ)), roxarsone (ROX), and p-arsanilic acid (p-ASA)) on/from virgin polyethylene (V-PE), white PE mulching film (W-PE, with Si-containing additives), and black PE mulching film (B-PE, with CaCO₃ and TiO₂ additives) MPs. The maximum sorption amounts of arsenic species on V-PE (3.33-20.10 mg/kg) and W-PE MPs (4.78-21.93 mg/kg) had no significant difference, while those on B-PE (43.02-252.19 mg/kg) facilitated by its additives were up to one order of magnitude greater than V-PE or W-PE (p < 0.05). Desorption hysteresis index (HI) indicated the irreversible arsenic sorption on three PE MPs, especially for B-PE containing additives that can co-precipitate and complex with arsenicals. The effects of pH, humic substances, and coexisting anions on arsenic sorption by B-PE were more obvious than that by V-PE or W-PE MPs, attributing to electrostatic interaction enhanced by CaCO₃ and TiO₂ additives. This work provides theoretical basis for migration of arsenic species on MPs containing plastic additives and their potential environmental risk assessment.

Iron-doped hydroxyapatite for the simultaneous remediation of lead-, cadmium- and arsenic-co-contaminated soil

Since lead, cadmium and arsenic have completely opposite chemical behaviors, it is very difficult to stabilize all these three heavy metals simultaneously. Herein, a novel iron-doped hydroxyapatite composite (Fe-HAP) was developed via an ultrasonic-assisted microwave hydrothermal method for the simultaneous remediation of lead-, cadmium-, and arsenic-co-contaminated soil in Hunan Province, South China. Using DTPA/sodium bicarbonate extractant to extract bioavailable Pb, Cd and As in soil after Fe-HAP remediation for 60 days, the immobilization efficiencies were 79.77%, 51.3% and 37.5% for Pb, Cd and As, respectively. The soil extractable and exchangeable fractions of Pb, Cd and As decreased significantly. In batch experiments, the adsorption kinetics of Pb, Cd and As on Fe-HAP were well described by pseudo-second-order models, indicating that the adsorption is controlled by chemisorption. In the Langmuir adsorption isotherm, the maximum adsorption capacities of Cd²⁺ and As(V) were 476.2 mg g^-1 and 195.69 mg g^-1, respectively, while Pb²⁺ fit the Freundlich model better. The XRD, SEM and XPS analyses indicated that Fe-HAP formed stable minerals of Pb₅(PO₄)₃OH, Cd₃(PO₄)₂·4H₂O, Cd(OH)₂ and Fe₃(AsO₄)₂·6H₂O with Pb, Cd and As. Overall, its facile and efficient immobilization performance indicate that Fe-HAP has potential for practical applications in integrative remediation of Pb-, Cd-, and As- co-contaminated soil.

Determination and speciation of trace inorganic arsenic species in water samples by using metal organic framework mixed-matrix membrane and EDXRF spectrometry

A facile method to selectively determine trace As(V) species in the existence of As(III) one in water samples was developed, which was based on the batch adsorption process by using a miniaturized MIL-101(Fe) mixed-matrix membrane (MOF-MMM) followed by a direct determination through energy dispersive X-ray fluorescence (EDXRF) spectrometry. The quantitative adsorption of As(V) was achieved at pH (3-6) from 30 mL sample in 120 min of equilibrium time by employing the membrane with a monolayer adsorption capacity of Q_o = 1.953 mg g^-1. The direct determination of As(V) adsorbed on the membrane by EDXRF spectroscopy provided a method, not only easy-to-use and operable without elution stage, but also cost effective due to low gas consumption during the analysis. With a limit of detection of 0.094 μg L^-1, analytical performance of the method, which was evaluated on fortified real water samples with three levels of As(V) (5, 10 and 50 μg L^-1), demonstrated good recoveries in the range of 98(±3)-105(±10)%. Furthermore, the speciation of As(III) and As(V) in the fortified real samples containing other ionic species was also successfully achieved by described approach with characteristics of simple, cheap, viable and reproducible.