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The goethite (α-FeOOH) nanoparticles were wrapped on the reduced graphene oxide (rGO) to synthesize the α-FeOOH/rGO nanocomposites. The nanocomposites (NCs) were initially examined for their optical, structural, and morphological properties. The XRD data obtained the crystallite size of the α-FeOOH, showed that the average crystal size for pristine α-FeOOH and α-FeOOH/rGO nanocomposites were about 85 and 90 nm, respectively. The transmission electron microscope confirmed the nanoparticles (NPs) were evenly distributed throughout the reduced graphene oxide sheets. The nanocomposites improved glassy carbon electrodes (GCE), making them efficient sensors for detecting the arsenic(III) (As+3) in a pH 5 phosphate buffer solution with an Ag/AgCl reference electrode. The detection limit for As+3 was 0.07 μgL−1 and the resulting sensitivity was 0.39 μA−1 μgL−1 in the linear dynamic range of 0.1–10 μgL−1. The α-FeOOH/rGO/GCE was more sensitive than its original and showed a synergistic effect due to the influence of α-FeOOH on the properties of rGO. The α-FeOOH/rGO NCs-modified GCE electrode performed as a promising sensor, by separating the common interfering ions. Moreover, the modified electrode exhibited remarkable stability, repeatability, and potential real-time application towards the detection of arsenic(III). Additionally, the proposed approach has been successfully applied to the detection of As+3 in the real water sample. [ABSTRACT FROM AUTHOR]

We report copper(II) arsenite-encapsulated ferritin nanoparticles (CuAS-FNs) as oxidative stress-amplifying anticancer agents. The CuAS-FNs were fabricated through CuAS mineralization in the cavity of the FNs. The formation of crystalline CuAS complex minerals in the FNs was systematically identified using various analytical tools, including X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM)-associated energy-dispersive X-ray spectroscopy (TEM-EDS). The CuAS-FNs showed pH-dependent release behavior, in which the CuAS mineral was effectively retained at physiological pH, in contrast, at lysosomal pH, the CuAS complex was dissociated to release arsenite and Cu2+ ions. At lysosomal pH, the release rate of arsenite (HAsO 3 2−) and Cu2+ ions from the CuAS-FNs more accelerated than at physiological pH. Upon transferrin receptor-1-mediated endocytosis, the CuAS-FNs simultaneously released arsenite and Cu2+ ions in cells. The released arsenite ions can increase the intracellular concentration of hydrogen peroxide (H 2 O 2), with which the Cu2+ ions can elevate the level of hydroxyl radicals (·OH) via Fenton-like reaction. Thus, the CuAS-FNs could target cancer cell through the recognizing ability of FNs and kill cancer cells by amplifying the ·OH level through the synergistic activity of Cu2+ and arsenic ions. Importantly, MCF-7 tumors were effectively suppressed by CuAS-FNs without systemic in vivo toxicity. Therefore, the CuAS-FNs is a promising class of Fenton-like catalytic nanosystem for cancer treatment. Copper(II) arsenite-encapsulated ferritin nanoparticles (CuAS-FNs) were developed as targeted and oxidative stress-amplifying anticancer agents. The CuAS-FNs were rationally designed by combining the TfR-1-mediated endocytosis of the FNs and the oxidative stress amplification of the CuAS. This study paves a way for a wide range of novel cancer-specific therapeutics by systematically modulating the oxidative stress in cancer cells. [Display omitted] [ABSTRACT FROM AUTHOR]

Poorly-crystalline ferrihydrite is ubiquitous in the environment and contributes to controlling the fate of arsenic in sediments and soils. Although there is evidence that ferrihydrite has a higher affinity towards As(III) relative to As(V), little is known about how and why As(III) is readily immobilized by ferrihydrite. In this study, ferrihydrite was employed to evaluate the As(III) and As(V) adsorption behavior. The properties of ferrihydrite such as morphology, pore size distribution, arsenic adsorption species, and adsorption energies of arsenic at different sites were carefully examined using TEM-EDS mapping, positron annihilation lifetime (PAL) spectroscopy, X-ray absorption spectroscopy (XAS), N 2 adsorption isotherms, and theoretical calculations of density function theory (DFT). Batch adsorption experiments revealed that the maximum adsorption of As(III) (839.7 μmol g−1) on ferrihydrite, fitted by Langmuir model, was considerably larger than that of As(V) (372.4 μmol g−1). PAL characterization and pore size distribution analysis demonstrated that ferrihydrite had an abundance of vacancy cluster-like micropores, which consisted of 10–20 atom deficiencies (V 10-20). The calculated hydrated ion size of As(III) species (4.22 Å) at pH 6.0 was smaller than the size of As(V) (5.90 Å). The higher As(III) adsorption to ferrihydrite was attributed to its surface adsorption sites as well as its abundant micropore adsorption sites, which are available only to As(III) due to their size matching well with the size of the ferrihydrite micropores, thus significantly contributing to greater As(III) immobilization. [ABSTRACT FROM AUTHOR]

[Display omitted] • Selective colorimetric detection of arsenite using N5R3 and N5R4. • N5R3 showed LOD of 7.41 ppb and binding constant of 2.9976 × 106 M−1 for arsenite. • Validation of experimental results using DFT studies. • The fabricated test strips can quantitatively detect arsenite anion and arsenite detection was done in milk, honey and water samples. • Demonstration of molecular logic gates. Millions of people are exposed to dangerous arsenic levels in drinking water, highlighting the urgent need for affordable, continuous on-site arsenic monitoring methods. It is crucial to specifically detect arsenite among inorganic arsenic anions because it is more poisonous than arsenate. Addressing these concerns, the present study developed 5-(4-nitrophenyl)-2-furaldehyde based two colorimetric chemosensors, N5R3 and N5R4, with different signaling groups for the selective detection of arsenite anions over arsenate in DMSO/H 2 O (6:4, v/v). The red-shift in the UV–Vis absorption spectra supported the distinct color changes of sensors N5R3 and N5R4 displayed upon binding with arsenite. Sensors demonstrated stability over a pH range of 6 to 12 and exhibited stability over a considerable time period. Among the chemosensors, N5R3 exhibited the lowest detection limit of 7.41 ppb with a high binding constant of 2.9976 × 106 M−1 for arsenite. The 1:1 binding interactions between the chemosensors and arsenite were confirmed using B-H plot and Job's plot analysis. The intramolecular charge transfer (ICT) mechanism for detecting arsenite was proposed through UV and 1H NMR titrations, electrochemical studies, mass spectral analysis and DFT calculations. The interactions between the sensor and arsenite anions were further analyzed using global reactivity parameters (GRPs). Practical applications were demonstrated through the utilization of test strips and molecular logic gates. Both chemosensors efficiently recognized arsenite in real water, honey, and milk samples. [ABSTRACT FROM AUTHOR]

Arsenic is one of the most dangerous groundwater contaminants whose effective removal is a major challenge for environmental scientists. Herein, several cellulose triacetate-based hybrid membranes are synthesized by adding different dosages (10, 30, and 50 wt%) of chitosan or chitosan-stabilized iron nanosheets. The fabricated membranes are characterized by advanced analytical tools such as AFM, SEM, FTIR, BET, TGA, zeta potential, and XRD. The enhancement in hydrophilicity and improved antifouling are evaluated by porosity, water uptake, contact angle, permeability tests, and bovine serum albumin (BSA) studies. At neutral pH, the cellulose triacetate-chitosan 50 % (CTA-CH 50 %) removed 85.13 % As(III) and 87.20 % As(V) at 67.23 L.m−2.h−1 permeability. On the other hand, cellulose triacetate-chitosan iron nanosheets 50 % (CTA-CIN 50 %) removed 91.30 % As(III) and 84.24 % As(V) at 62.35 L.m−2.h−1 permeability. The synthesized membranes efficiently removed arsenic from real groundwater taken from different Pakistani cities. The membranes are synthesized through a low-cost and scalable method, making it convenient for industrial-level applications. [Display omitted] • Synthesis of novel cellulose triacetate-based membranes. • Membranes are doped with chitosan or chitosan-stabilized iron nanosheets. • CTA-based hybrid membranes show great mechanical strength. • CTA hybrid membranes removed Arsenate and Arsenite from groundwater. • Hybrid membranes showed >95% Arsenic removal in real samples. [ABSTRACT FROM AUTHOR]

Water contamination by arsenic (As) poses a significant threat to millions of people worldwide. The development of an effective, affordable, and decentralized system for As removal remains a critical need, particularly to treat As at environmentally relevant concentrations. In this study, a self-standing electrode composed of an engineered interface of CuBi 2 O 4 /CuO/Fe 2 O 3 was synthesized on fluorine-doped tin oxide (FTO) substrate using electrodeposition and dip-coating techniques. Each layer Bi 2 O 3 , CuBi 2 O 4 , CuO, and Fe 2 O 3 was characterized photochemically and electrochemically to identify their light harvesting and electron transfer capacities. The efficacy of the CuBi 2 O 4 /CuO/Fe 2 O 3 electrode for removing 0.5 mg L−1 As (III) was evaluated under various treatment conditions, including adsorption, photocatalysis (PC), electrocatalysis (EC), and photoelectrocatalysis (PEC). The PEC treatment at 1.0 V vs Ag/AgCl under visible light irradiation exhibited outstanding As removal efficiency of 96.8 %, surpassing PC (40.4 %) and EC (54.5 %). Fundamental evaluation of the removal mechanism revealed that CuBi 2 O 4 /CuO/Fe 2 O 3 oxidizes As (III) to As (V) for enhanced adsorption onto iron oxide sites, as confirmed by X-ray photoelectron spectroscopy (XPS), which identified both As (III) and As (V) adsorbed on the surface. These findings underscore the importance of a rational design approach for photoanodes in As adsorption, highlighting the significant role of individual layers. [Display omitted] • Synergistic enhancement due to the p - n heterojunction in CuBi 2 O 4 /CuO/Fe 2 O 3. • Interlayer electrode enhances charge carrier accumulation under visible light. • Photoelectrocatalysis significantly increases As removal rate. • Oxidation/Adsorption dual mechanism revealed by XPS analysis. [ABSTRACT FROM AUTHOR]

We explain here that the authors of the article cited in the title have misrepresented the species of As(III) and As(V) in solutions and, in particular, have neglected their speciation as a function of pH. Their discussion of (ad)sorption mechanisms is therefore unsatisfactory, especially since organic matter (flower waste) and the presence of iron oxyhydroxides should be taken into account. Furthermore, the modeling of (ad)sorption kinetics and isotherms was based on linearized equations, whereas the corresponding nonlinear equations should have been used. Therefore, we believe that the authors of the original article should make corrections and additions to it. This Letter to the Editor is motivated by a concern to avoid the dissemination of approximate or even incorrect concepts in the scientific literature, which could mislead novice researchers. [Display omitted] • As shares some similarities with N and P (belonging to Group 15 elements). • NaAsO 2 and NaH 2 AsO 4 are covalent compounds (not ionic compounds). • Oxidation state of elements: writing As(III) and As(V) rather than As3+ and As5+. • PFO model: r 2 = 0.992, but q e,experiment (4.98 mg/g) is very different from q e,PFO (71.4 mg/g), which results from applying linear method. • IUPAC recommends symbol (⇌) for chemical equilibria. Symbol (↔) is used for resonance structures. [ABSTRACT FROM AUTHOR]

Schwertmannite (Sch) holds a great promise as an iron material for remediating Arsenic (As)-contaminated paddy soils, due to its extremely high immobilization capacities for both arsenate [As(V)] and arsenite [As(III)]. However, there is still limited knowledge on the mineral phase transformation of this metastable iron-oxyhydroxysulfate mineral in paddy soils, particularly under different water management regimes including aerobic, intermittent flooding, and continuous flooding, and how its phase transformation impacts the migration of As in paddy soils. In this study, a membrane coated with schwertmannite was first developed to directly reflect the phase transformation of bulk schwertmannite applied to paddy soils. A soil incubation experiment was then conducted to investigate the mineral phase transformation of schwertmannite in paddy soils under different water management regimes and its impact on the migration of As in paddy soil. Our findings revealed that schwertmannite can persist in the paddy soil for 90 days in the aerobic group, whereas in the continuous flooding and intermittent flooding groups, schwertmannite transformed into goethite, with the degree or rate of mineral phase transformation being 5% Sch >1% Sch > control. These results indicated that water management practices and the amount of schwertmannite applied were the primary factors determining the occurrence and degree of mineral transformation of schwertmannite in paddy soil. Moreover, despite undergoing phase transformation, schwertmannite still significantly reduced the porewater As (As(III) and As(V)), and facilitated the transfer of non-specifically adsorbed As (F1) and specifically adsorbed As (F2) to amorphous iron oxide-bound As (F3), effectively reducing the bioavailability of soil As. These findings contribute to a better understanding of the mineralogical transformation of schwertmannite in paddy soils and the impact of mineral phase transformation on the retention of As in soil, which carry important implications for the application of schwertmannite in remediating As-contaminated paddy soils. [Display omitted] • A novel method was developed to reflect schwertmannite transformation in soil. • Water management controlled schwertmannite transformation in paddy soil. • Schwertmannite exhibited a strong stability under aerobic conditions. • Schwertmannite transformed to goethite under continuous or intermittent flooding. • Schwertmannite reduced As mobility despite undergoing phase transformation. [ABSTRACT FROM AUTHOR]

Arsenite (As) and fluoride (F), both of which are linked to a variety of human ailments, are regularly found in underground drinking water. Numerous studies have shown that As and/or F have negative impacts on testicular function and fertility. For this purpose, mouse Leydig cells, the main cells responsible for the generation and regulation of steroid hormones such as testosterone, were used to reveal the effects of individual and combined exposure of As and F on the steroidogenic pathway in the male reproductive system. Leydig cells were treated with 0.39 μM (50 ppb) As and 0.0476 mM (2 ppm) F alone and in combination for 24 h. The findings revealed that As and/or F exposure induced oxidative stress and apoptosis in Leydig cells and altered antioxidant equilibrium of the cells by reducing superoxide dismutase, catalase, glutathione peroxidase. Additionally, individual and combined administration of As and/or F significantly supressed the expression of both steroidogenic enzymes and the genes encoding these enzymes. In conclusion, this study showed that exposure to As and F at environmentally relevant concentrations dispersed by water decreased testosterone production in Leydig cells, an important cell of the male reproductive system. The deleterious effects of even the lowest concentrations of As and F elements that can reach humans from the environment on the Leydig cell, and therefore on male infertility, emphasize necessity new safe limits for these elements. • GA reduced cell viability and increased LDH activity in mouse Leydig cells. • GA led to increased expression levels of apoptotic genes in mouse Leydig cells. • GA induced oxidative stress in mouse Leydig cells. • Hes may play a protective role in GA-induced toxicity in mouse Leydig cells. [ABSTRACT FROM AUTHOR]

Arsenic contamination at high concentration frequently occurs in nature water environments and poses a great risk to human health. In this study, a cerium oxide/hydroxide-modified activated carbon was synthesized via a simple co-precipitation process as an adsorbent for the removal of arsenic from aqueous systems. Analysis of the cerium oxide/hydroxide-modified activated carbon by field emission scanning electron microscopy and X-ray photoelectron spectroscopy showed that cerium was mainly coated on the surface of activated carbon as cerium (IV) hydroxide. The arsenic adsorption performance of the adsorbent was investigated via batchwise adsorption and using a chromatographic system with a fixed bed column. Neutral pH conditions were optimal for removal of arsenic. Kinetic experiment data were described by a diffusion–chemisorption model. The adsorption isotherm followed the Langmuir model, and the maximum adsorption capacity of cerium oxide/hydroxide-modified activated carbon was 0.220 and 0.284 mmol g−1 for As(V) and As(III), respectively. Regeneration trials showed that cerium oxide/hydroxide-modified activated carbon could be regenerated with 0.1 mol L−1 NaOH solution as regenerant. During adsorption, redox reactions occurred in the aqueous and solid phases. As(III) was oxidized to As(V) by reduction of surface functional groups (C O, C-O, and cerium oxide/hydroxide) in the solid phase and by dissolved organic matters and surface functional groups in the aqueous phase. Chromatographic treatment with a fixed bed column of cerium oxide/hydroxide-modified activated carbon showed high arsenic adsorption efficiency. The repeated use of cerium oxide/hydroxide-modified activated carbon by chromatographic operation was also achieved. [Display omitted] • CeO 2 /(OH) x -modified activated carbon has high efficiency for removal of arsenic. • As(III) was oxidized to As(V) in both aqueous and solid phases during adsorption. • CeO 2 /(OH) x -modified activated carbon is easily regenerated. • Adsorptive removal of arsenic was achieved by chromatographic operation. [ABSTRACT FROM AUTHOR]

A thorough understanding of the complex redox coupling among manganese, arsenic, sulfur and oxygen in subsurface environments is still obscured by their metastable intermediate valances and speciation. Arsenic sulfide minerals may be disturbed by natural or anthropogenic activities, and encounter oxidants such as oxygen and reactive trivalent Mn species, and how these abiotic interactions impact the mineral dissolution and transformation of arsenic and sulfur species, remains unknown. In this study, we investigated the effects of dissolved Mn(III) and manganite (γ-MnIIIOOH) on the dissolution behaviors of orpiment (As 2 S 3) and realgar (AsS) under anoxic and oxic conditions. Complementary control experiments were also performed with dissolved arsenite without reduced sulfur. Oxygen, dissolved Mn(III) or manganite did not induce the oxidation of dissolved arsenite within several weeks. Orpiment's initial dissolution is a non-redox process releasing of arsenite and sulfide, and the three above oxidants promoted the dissolution of orpiment by rapid oxidation of dissolved sulfide. However, only when both dissolved Mn(III) and dissolved oxygen were present, substantial accumulation of arsenate and sulfate were observed. These results suggested the critical role of sulfur species in abiotic arsenic transformation and a synergetic effect of Mn and oxygen on sulfur oxidation. In contrast to orpiment, the dissolution of realgar was a redox reaction that involved the oxidation of As(II) to As(III) and the direct releasing of sulfide, which could be promoted by both dissolved oxygen and manganite. The effect of dissolved Mn(III) and oxygen on the formation of arsenate and sulfate was also clearly observed during the dissolution of realgar. Despite of the slow abiotic oxidation of dissolved arsenite to arsenate in the presence dissolved Mn(III) and oxygen, the coexistence of sulfide could enable rapid accumulation of arsenate, accompanied by substantial transformation to sulfate. The evidence of thioarsenic species in these experiments provided a plausible explanation as an alternative pathway for the oxidation of the two elements by dissolved Mn(III). These results provide new insights for the Mn-As-S cycling in redox transition environments. [ABSTRACT FROM AUTHOR]

In the present study, two chromogenic probes, N7R2 and N7R3, each containing two binding sites, were designed and synthesized for the selective detection of arsenite in DMSO/H 2 O (1:1, v /v). The probes exhibited stability across a pH range spanning from 5 to 12. The lower detection limits of 2.01 ppb (18.86 nM) for N7R2 and 1.79 ppb (16.75 nM) for N7R3, which are much lower than the WHO recommended permissible limit of arsenite, confirmed the superior efficiency of the probes in detecting arsenite. The detection mechanism for arsenite was proposed through UV and 1H NMR titrations, electrochemical studies, and DFT calculations. Practical applications were demonstrated through the fabrication of test strips and molecular logic gates. The probes efficiently recognized arsenite in real water, honey, milk samples, and fruit/vegetable juices. Both N7R2 and N7R3 exhibited excellent recovery rates in the analysis of food samples, demonstrating the probes' usefulness in real sample analysis. [Display omitted] • Selective colorimetric detection of arsenite over arsenate using N7R2 and N7R3. • N7R3 showed LOD of 1.79 ppb and binding constant of 1.6296 × 1013 M−2 for arsenite. • Validation of experimental results using DFT studies. • Practical applications by fabricating test strips and molecular logic gates. • Arsenite detection was done in milk, honey and water samples and fruit/vegetable juices with high recoveries and precision. [ABSTRACT FROM AUTHOR]

Red mud (RM), an industrial solid waste generated by the alumina industry, is rich in Fe 2 O 3 , Al 2 O 3 , and SiO 2 , and has excellent potential for use as a cheap and economical support and as an adsorbent. In this work, a co-precipitation method was used to load MnO 2 on RM as an adsorbent (MnRM) to remove As(V) and As(III) from water. The aim was to fully utilize the oxidative properties of MnO 2 and the adsorption capacity of Fe-Al oxides/hydroxides in RM to enhance the As(V) and As(III) capacity in water. The experimental data proved that the adsorption performance of MnRM was much better with adsorption capacities of 31.57 mg/g and 39.32 mg/g for As(V) and As(III), which were 11.29 and 5.71 times higher than that of the raw RM, respectively. Meanwhile, the adsorption capacities of MnRM were also much higher than that of MnO 2 for As(V) (18.90 mg/g) and As(III) (27.97 mg/g). The excellent adsorption performance of MnRM makes it ideal for the treatment of As(V) and As(III) contaminated wastewater. [Display omitted] [ABSTRACT FROM AUTHOR]

Contamination of ground water and soil with toxic metalloids like arsenic (As) poses a serious hazard to the global agricultural food production. One of the best ways to restrict entry of As into the food chain is selection of germplasms which accrue extremely low level of As in grains. Here, we screened diverse maize genotypes under high arsenite (100 μM AsIII) stress and identified PMI-PV-9 and PMI-PV-3 as AsIII-tolerant and -sensitive maize genotype respectively. Expression of genes associated with As uptake, vacuolar sequestration, biosynthesis of phytochelatins, root-to-shoot translocation, in vivo ROS generation, fine tuning of antioxidant defense system, DNA and membrane damage, H 2 O 2 and superoxide anion (O 2 •-) levels were compared among the selected genotypes. PMI-PV-9 plants performed much better than PMI-PV-3 in terms of plant growth with no visible symptom of As toxicity. Susceptibility of PMI-PV-3 to AsIII stress may be attributed to comparatively low expression of genes involved in phytochelatins (PCs) biosynthesis. Concomitant decrease in ABCC1 expression might be another key factor for futile sequestration of AsIII into root vacuoles. Moreover, up-regulation of ZmNIP3; 1 might contribute in high root-to-leaf As translocation. Substantial spike in H 2 O 2 , O 2 •- and MDA levels indicates that PMI-PV-3 plants have experienced more oxidative stress than PMI-PV-9 plants. Appearance of prominent deep brown and dark blue spots/stripes on leaves as revealed after DAB and NBT staining respectively suggest severe oxidative burst in PMI-PV-3 plants. Marked reduction in DHAR and MDAR activity rendered PMI-PV-3 cells to recycle ascorbate pool ineffectively, which might have exacerbated their susceptibility to AsIII stress. In a nutshell, incompetent PCs mediated detoxification system and disruption of cellular redox homeostasis owing to feeble antioxidant defence system resulting oxidative burst might be the prime reasons behind reduced performance of PMI-PV-3 plants under AsIII stress. [Display omitted] • Present study demonstrates arsenite (AsIII) stress tolerance mechanism in maize. • Up-regulation of NIPs resulting high AsIII uptake by root leads to sensitivity. • Inefficient PC mediated detoxification system contributes to AsIII susceptibility. • High AsIII sequestration in root vacuole leads to low root-to-shoot As translocation. • AsIII induced deregulation of cellular redox homeostasis results in oxidative burst. [ABSTRACT FROM AUTHOR]

• A novel porous Fe-Mn chitosan bead (PFMB) was synthesized for arsenite removal. • Freeze-drying technique created a porous structure for better adsorption performance. • Arsenite was oxidized to arsenate and then adsorbed by PFMB. • The PFMB exhibited promising arsenite removal in potential applications. A novel porous Fe-Mn chitosan bead (PFMB) was fabricated through the freeze-drying technique for the enhanced oxidation and adsorption of arsenite (As(Ⅲ)) from aqueous solution. The porous internal structure of PFMB provided a significantly higher As(Ⅲ) oxidation and adsorption rate than solid Fe-Mn chitosan bead (FMB). The experimental results showed that FMB and PFMB exhibited the theoretical maximum As(Ⅲ) adsorption capacities of 27.42 and 49.80 mg/g, respectively. The real-time oxidation and adsorption progress of As(Ⅲ) onto PFMB was deeply evaluated: PFMB effectively oxidized As(Ⅲ) to As(Ⅴ) and the generated As(Ⅴ) was subsequently adsorbed. The operational parameters (initial pH, adsorbent dosage, ionic strength, and HA concentration) were thoroughly investigated and had no significant influence on As(Ⅲ) removal by PFMB. Finally, the regeneration experiment showed that PFMB can be easily regenerated and the recycled PFMB can successfully remove As(Ⅲ) in the following 5 cycles. Column experiments suggested that the column device could effectively remove the As(Ⅲ) in more than 3830 bed volume with the influent velocity at 0.5 mL/min before effluent concentration reached 0.05 mg/L. These results revealed the enhanced oxidation and adsorption performance of As(Ⅲ) onto PFMB and provided a reference for the future application of PFMB in arsenic-contaminated water treatment. [Display omitted] [ABSTRACT FROM AUTHOR]

The terrestrial fern Pityrogramma calomelanos, a cosmopolitan tropical species, is one of the strongest known arsenic (As) hyperaccumulator plants. This study aimed to determine whether P. calomelanos preferentially forages for arsenite (As3+) or arsenate (As5+) in As-contaminated soils, and whether a positive root response to As enhances accumulation in P. calomelanos. Therefore, an experiment using rhizoboxes divided in two halves were constructed with a control soil (C) and As3+ or As5+ dosed soil at either 50 and 100 μg g−1 As. Micro-X-ray Fluorescence elemental mapping (μXRF) was employed to analyze the distribution of As in roots and fronds, and Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS) was used to determine As distribution in the reproductive tissues of P. calomelanos. The results showed that Pityrogramma roots do not specifically forage for As-contaminated soil; the area based on pixel counts was similar across all the treatments with no statistical differences. However, frond biomass was slightly higher in the treatments C ǀ As3+ and C ǀ As5+, and the highest accumulation of As in fronds was in the As5+ ǀ As3+ (100 μg g−1) treatment, with 3418 and 2370 μg g−1 in old and young fronds respectively. Arsenic cycling across the roots was observed by the μXRF mapping; in C ǀ As5+ (100) the As was higher and evenly distributed in both sections, whilst in C ǀ As3+ (50), the As was higher in the As3+ side. The μXRF mapping showed a broader As distribution in older fronds, where As was highest in the rachis and extended into the pinnule through the midrib. Pityrogramma calomelanos does not specifically root forage for As-enriched zones in the soil and grows healthily without signs of toxicity at lower (50 μg g−1) and higher (100 μg g−1) concentrations of As3+ and As5+ in the soil. [Display omitted] [ABSTRACT FROM AUTHOR]

Cadmium (Cd) and arsenic (As) are two highly toxic heavy metals and metalloids that coexist in many situations posing severe threats to plants. Our investigation was conducted to explore the different regulatory mechanisms of ryegrass (Lolium perenne L.) responding to individual and combined Cd and As stresses in hydroponics. Results showed that the ryegrass well-growth phenotype was not affected by Cd stress of 10 mg·L-1. However, As of 10 mg·L-1 caused rapid water loss, proline surge, and chlorosis in shoots, suggesting that ryegrass was highly sensitive to As. Transcriptomic analysis revealed that the transcription factor LpIRO2 mediated the upregulation of ZIP1 and YSL6 that played an important role in Cd tolerance. We found that the presence of As caused the overexpression of LpSWT12 , a process potentially regulated by bHLH14, to mitigate hyperosmolarity. Indoleacetic acid (IAA) and abscisic acid (ABA) contents and expression of their signaling-related genes were significantly affected by As stress rather than Cd. We predict a regulatory network to illustrate the interaction between transporters, transcription factors, and signaling transduction, and explain the antagonism of Cd and As toxicity. This present work provides a research basis for plant protection from Cd and As pollution. [Display omitted] • The physiological response of ryegrass suggests its adaptability to Cd, and sensitivity to As. • Cd substitute Fe intake would be mediated by LpIRO2. • Overexpressed LpSWT12 and bHLH14 participates in regulating hyperosmosis induced by As stress. • IAA and ABA signaling is involved in Cd and As stresses resistance. • We establish ryegrass regulatory network in response to combined As and Cd stresses. [ABSTRACT FROM AUTHOR]

Globally, over 200 million people are at risk of exposure to high levels of arsenic due to increasing environmental pollution; thus, there is high demand for detection methods to monitor arsenic contamination in the natural environment. In this study, we developed a cost-effective method for detecting arsenite [As(III)] ions using sodium dodecyl sulfate (SDS)-coated gold nanoparticles (AuNPs) and Tris. Positively charged Tris molecules induce aggregation of AuNPs by neutralizing the negative charge of SDS; however, this is prevented by the presence of As(III), which has a high affinity for AuNPs. This proposed method is able to detect 5 parts per billion (ppb) and 1.85 ppb of As(III) through naked eye and spectrophotometric measurements, respectively. Furthermore, a chitosan-based lateral flow (LF) strip was devised to enhance the visual signal intensity by concentrating AuNPs on its test zone, since AuNPs of lower concentration were more effective for detecting low As(III) concentrations. As a result, As(III) was detected at 500 parts per trillion (ppt) without any interference from other metal ions, which is a 10-fold improvement from solution-based assays. Importantly, the colorimetric signal amplification strategy (using the chitosan-based LF strip) is versatile and can be applied to many other AuNP- or nanomaterial-based technologies. The proposed system enables the detection of As(III) in facility-limited or point-of-care settings, making it ideal for use in underdeveloped countries because it requires a small sample volume (approximately 20–30 µL) with a small amount of AuNPs, and takes only 10 min to generate colorimetric results. • Cost-effective, colorimetric detection of arsenite [As(III)] using SDS-coated AuNPs and Tris. • Visual detection of As(III) down to a concentration of 5 ppb and 1.85 ppb with the naked eye and spectrophotometer. • Visual signal enhancement of AuNPs using chitosan-based lateral flow strip. • Visual detection of As(III) down to a concentration of 500 ppt in LF strips with the naked eye. • High specificity to As(III) without any interference from other metal ions including As(V). [ABSTRACT FROM AUTHOR]

In this study, nanoplastic (NPs) at environmentally relevant concentration (0.001% w/w) had no effect on the growth of rice, while significantly elevated the phytotoxicity of As (III) by 9.4–22.8% based on the endpoints of biomass and photosynthesis. Mechanistically, NPs at 0.001% w/w enhanced As accumulation in the rice shoots and roots by 70.9% and 24.5%, respectively. Reasons of this finding can was that (1) the co-exposure with As and NPs significantly decreased abscisic acid content by 16.0% in rice, with subsequent increasing the expression of aquaporin related genes by 2.1- to 2.7-folds as compared with As alone treatment; (2) the presence of NPs significantly inhibited iron plaque formation on rice root surface by 22.5%. We firstly demonstrated that "Trojan horse effect" had no contribution to the enhancement of As accumulation by NPs exposure. Additionally, NPs disrupted the salicylic acid, jasmonic acid, and glutathione metabolism, which subsequently enhancing the oxidation (7.0%) and translocation (37.0%) of in planta As, and reducing arsenic detoxification pathways (e.g., antioxidative system (28.6–37.1%), As vacuolar sequestration (36.1%), and As efflux (18.7%)). Our findings reveal that the combined toxicity of NPs and traditional contaminations should be considered for realistic evaluations of NPs. [Display omitted] • NPs at environmentally relevant concentration elevated the phytotoxicity of As (III). • NPs enhanced As accumulation by inhibiting ABA content and iron plaque formation. • NPs disrupted the SA, JA, and GSH metabolism in rice. • NPs inhibited the antioxidative system, As vacuolar sequestration, and As efflux. [ABSTRACT FROM AUTHOR]

[Display omitted] • {2 0 1} TiO 2 was developed for Se(IV) and As(III) removal for the first time. • High adsorption capacity for Se (0.25 mmol/g) and As (0.32 mmol/g) was achieved. • Se(IV)/As(III) formed bidentate binuclear complexes at bridge-Ti 4C of {2 0 1} TiO 2. • Cd(II) enhanced Se/As adsorption on {2 0 1} TiO 2 by forming ternary complexes. • Change in hybrid orbital energy drives the antagonistic and synergistic adsorption. Arsenic (As) and Selenium (Se) contaminations present an urgent environmental concern, whereas its removal remains a significant challenge due to the lack of fundamental knowledge of the adsorption mechanism and effective adsorbents. Herein, {2 0 1} TiO 2 exhibited the application potential for As(III) and Se(IV) removal, and the antagonistic effect was examined at the molecular level using X-ray absorption spectroscopy and density functional theory calculations. The Langmuir adsorption capacity of As(III) and Se(IV) on {2 0 1} TiO 2 was 0.32 mmol/g and 0.25 mmol/g, respectively. The rate constant k for Se(IV) adsorption was 5.46 g/(mmol/h), which was 10.2 times higher than that of As(III) (0.48 g/(mmol/h)). EXAFS and CD-MUSIC results demonstrated that both As(III) and Se(IV) formed bidentate binuclear inner-sphere complexes at the bridge-Ti 4C of {2 0 1} TiO 2. The pd hybrid orbital energy of Ti-O bonds in Ti 2 O 2 SeO complex (−2.42 eV) was lower than that in Ti 2 O 2 AsO- complex (−2.26 eV), indicating the better adsorption stability and stronger affinity of Se(IV) adsorbed on {2 0 1} TiO 2. The coexisting Cd(II) formed ternary complexes with As(III)/Se(IV) on {2 0 1} TiO 2 , enhancing the Freundlich adsorption of Se(IV) to 0.69 mmol/g and As(III) to 0.43 mmol/g. The introduction of Cd(II) altered the orbital hybridization interaction, and the charge transfer from Ti-3 d to Cd-5 s orbitals improved the adsorption energies of As(III)/Se(IV) on {2 0 1} TiO 2. The ICOHP value of the Se-O-Cd bond was higher than that of the As-O-Cd bond, indicating the stronger affinity of Cd(II) and Se-O dangling bond. Gaining insights into the surface complexation modeling at the molecular and electronic level reveals the nature of coexisting ions adsorption behaviors. [ABSTRACT FROM AUTHOR]

N6-methyladenosine (m6A), a high-profile RNA epigenetic modification, responds to oxidative stress and temporal-specifically mediates arsenic carcinogenesis. However, how m6A affects aberrant redox homeostasis required for arsenic carcinogenesis is poorly understood. Here, we established arsenic-carcinogenic models of different stages, including As-treated, As-transformed, and As-tumorigenic cell models. We found that arsenic-induced reactive oxygen species (ROS) elevated m6A levels, thus triggering m6A-dependent antioxidant defenses. During arsenic-induced cell transformation, METTL3-upregulated m6A on the mRNAs of SOD1, SOD2, CAT, TXN, and GPX1 promoted the mRNA translation and protein expressions of these antioxidant enzymes by increasing YTHDF1-mediated mRNA stability. Meanwhile, FTO-downregulated m6A on PRDX5 mRNA increased PRDX5 translation and expression by reducing YTHDF2-mediated mRNA decay. After upregulated antioxidant defenses balanced with high levels of ROS induced by arsenic, the m6A balance formed in mRNAs of six key antioxidant enzymes (SOD1, SOD2, CAT, TXN, GPX1, and PRDX5) and promoted high expressions of these antioxidant enzymes to maintain aberrant redox homeostasis. METTL3 inhibitor STM2457, FTO inhibitor FB23–2, or YTHDF1 knockdown disturbed the aberrant redox homeostasis by breaking the m6A balance, causing cell death in arsenic-induced tumors. Our results demonstrated that m6A promotes the formation and maintenance of aberrant redox homeostasis required for arsenic carcinogenesis by time-dependently orchestrating the adaptive expressions of six key m6A-targeted antioxidant enzymes. This study advances our understanding of arsenic carcinogenicity from the novel aspect of m6A-dependent adaptation to arsenic-induced oxidative stress. [Display omitted] • Arsenite-induced oxidative stress (OS) triggers m6A-dependent antioxidant defenses. • METTL3-catalyzed m6A upregulates SOD, CAT, TXN, GPX1 by YTHDF1-mediated mRNA stability. • FTO-reduced m6A upregulates peroxiredoxin PRDX5 by inhibiting YTHDF2-mediated mRNA decay. • m6A balance of antioxidant enzymes maintains redox homeostasis after cells adapt to OS. • Inhibiting METTL3, FTO, or YTHDF1 breaks m6A-maintained aberrant redox homeostasis. [ABSTRACT FROM AUTHOR]

[Display omitted] • Gestational iAsⅢ exposure via drinking induces hepatic developmental toxicity. • iAsⅢ evokes hepatic lipid deposition in adulthood via α-KG collapse. • α-KG reshapes lipid profile to relieve hepatic lipid deposition in later life. • α-KG restores the hepatic β-oxidation process by epigenetic reprogramming. • Hepatic damage partially arises from hypohydroxymethylation of Cpt1a at fetal stage. Inorganic trivalent arsenic (iAsⅢ) at environmentally relevant levels has been found to cause developmental toxicity. Maternal exposure to iAsⅢ leads to enduring hepatic lipid deposition in later adult life. However, the exact mechanism in iAsⅢ induced hepatic developmental hazards is still unclear. In this study, we initially found that gestational exposure to iAsⅢ at an environmentally relevant concentration disturbs lipid metabolism and reduces levels of alpha-ketoglutaric acid (α-KG), an important mitochondrial metabolite during the citric acid cycle, in fetal livers. Further, gestational supplementation of α-KG alleviated hepatic lipid deposition caused by early-life exposure to iAsⅢ. This beneficial effect was particularly pronounced in female offspring. α-KG partially restored the β-oxidation process in hepatic tissues by hydroxymethylation modifications of carnitine palmitoyltransferase 1a (Cpt1a) gene during fetal development. Insufficient β-oxidation capacities probably play a crucial role in hepatic lipid deposition in adulthood following in utero arsenite exposure, which can be efficiently counterbalanced by replenishing α-KG. These results suggest that gestational administration of α-KG can ameliorate hepatic lipid deposition caused by iAsⅢ in female adult offspring partially through epigenetic reprogramming of the β-oxidation pathway. Furthermore, α-KG shows potential as an interventive target to mitigate the harmful effects of arsenic-induced hepatic developmental toxicity. [ABSTRACT FROM AUTHOR]

• With No Lysine (WNK) kinase confers heavy metal tolerance in plants. • Overexpression of rice OsWNK9 increased the arsenite stress tolerance in transgenic Arabidopsis. • Transgenic Overexpressed lines exhibited increased antioxidant capacity, proline and reduced levels of hydrogen peroxide. • Co-expression analysis predicted OsWNK9 co-expressed with protein kinase and oxidative stress responsive protein. Protein kinases are involved in the transfer of phosphate group to serine, threonine, and tyrosine residues of a target protein. With No Lysine (WNK) kinase is a member of the serine/threonine protein kinase family, which has conserved catalytic lysine (K) residue in subdomain I instead of being in subdomain II.The WNKs family members in plants are stress inducible and have been validated for their role in abiotic stress tolerance. In the present study, we have characterized Arabidopsis overexpressed lines of OsWNK9 regulated by the constitutive promoter under arsenite stress. Moreover, we have performed In silico expression analysis of OsWNK9 under nutrient deficiency and heavy metal stress. Three independent transgenic Arabidopsis (OsWNK9 -OX T 11 , T 12 ,andT 13) lines showed tolerance to arsenite stress compared to wild-type (WT) plants. Under arsenite stress, transgenic lines T 11 , T 12 and T 13 showed 56.46, 57.8 and 51.66 % increased biomass respectively, as compared to WT plants. All three ArabidopsisOsWNK9 -OX lines exhibited higher proline content, increased antioxidant enzyme activities and lower hydrogen peroxide levels under arsenite stress. Besides, the total antioxidant capacity in terms of DPPH (2, 2-diphenyl-1-picrylhydrazyl) free radical scavenging percentage was increased by 8–15 % in three independent OsWNK9 -OX lines compared with those of WT plants. Protein-protein interaction analysis of OsWNK9 predicted interaction partners with protein kinase and oxidative stress-responsive protein. Co-expression analysis of OsWNK9 in phosphate deficiency and arsenate stress condition predicted various proteins including membrane transporter and transcription factors. Taken together, our results, for the first time, provide evidence that OsWNK9 could positively mediate arsenite stress tolerance in plants. [ABSTRACT FROM AUTHOR]

The removal of arsenite using biochar (BC) and biochar-CuO nanocomposite (BC-CuO-NC) from cypress cones biomass was systematically investigated. The copper oxide (CuO) nanoparticles (NP's) were synthesized using aqueous cypress cones extract. The BC was obtained by the pyrolysis of cypress cones biomass at 550°C and then impregnated with CuO-NP's to produce BC-CuO-NC. Arsenite adsorption into BC and BC-CuO-NC was studied using the batch technique at different pH, contact time, adsorbent dose, and temperature conditions. BC-CuO-NC demonstrated better adsorption efficiency than BC to 5-6 pH arsenite with a 55.58% removal percentage and a 10 min balance period. Compared with the Dubinin-Radushkevich isotherm equation, the Langmuir and Freundlich isotherm equations fit well with the experimental results. According to the Langmuir model, the saturated adsorption capacity of BC and BC-CuO-NC for arsenite can reach 22.831 and 36.765 mg/g, respectively. Kinetic studies have shown that the adsorption arsenite on BC and BC-CuO-NC was defined in pseudo-second-order. The determined thermodynamic parameters of the adsorption cycle were spontaneous, exothermic, and the random increase was observed. [ABSTRACT FROM AUTHOR]

Arsenite regulates the uptake and detoxification of arsenate in plants under low-phosphate conditions by governing the stability of PHOSPHATE STARVATION RESPONSE 1, as reported in a recent study by Navarro and colleagues. This finding opens new opportunities for research into developing mitigation strategies to deal with arsenic toxicity in plants. [ABSTRACT FROM AUTHOR]

The multiple metal resistant Staphylococcus sp. strain AS6, isolated from wastewater of Pakistan, was able to resist 25 mM arsenite and 150 mM arsenate. SEM analysis showed that no significant change in bacterial morphology under arsenite exposure was observed while EDX and FTIR analyses confirmed the surface adsorption and uptake of arsenite into the bacterial cells exposed to 15 mM arsenite. The GSH/GSSG ratio and NPSHs were increased 45.0 and 76.50% in 15 mM arsenite stress while antioxidant enzymes (SOD, CAT, POX, and APX) showed varied response in arsenic presence. The genome of strain AS6 was sequenced through Illumina NextSeq 550 sequencer and the genes confer resistance to arsenic such as arsR , arsB , and arsC were identified. The bacterial stain AS6 was able to oxidize arsenite 91%/8h and removed 93%/10 h arsenite through its inactivated biomass from the medium. The strain AS6 has great potential, due to its hyper-metal resistance and high arsenite oxidation ability, to be used as a bioresource for green chemistry to eliminate toxic arsenite from the environment. [ABSTRACT FROM AUTHOR]

The dominant arsenic oxidation state in groundwater as As(III) is more difficult to remove than As(V). To achieve higher As(III) removal, ceria (CeO2) nanorods characterized by Brunauer-Emmett- Teller, X-ray diffraction, scanning electron microscopy, Fourier transform infrared, and X-ray absorption spectroscopy were successfully used to combine oxidation and adsorption processes. Results showed that when calcination temperature increased surface area decreased, whereas crystallite size increased. Batch experiments indicated that the arsenic removal process was accurately described by a pseudo-second-order kinetic model with maximum removal capacities of 21.27 mg/g. X-ray absorption near-edge structure (XANES) of the solid-phase confirmed that CeO2 adsorbed As(III) with partial As(III) oxidization to As(V) on the surface. Further evidence of the mechanisms for As(III) removal was demonstrated by the hydroxyl group in the sorption and As(III) forming inner-sphere monodentate and bidentate complexes on the interface of the CeO2 solid phase. As(III) oxidization to As(V) during the sorption process suggested that CeO2 had high potential to remove As(III) from contaminated water. [ABSTRACT FROM AUTHOR]

• A new adsorbent, δ-MnO 2 modified activated carbon, has been prepared. • Solution pH remarkably affects arsenic adsorption. • The Langmuir model fits better than the Freundlich model. • Adsorption and oxidation of As(III) occurred simultaneously. • The removal mechanism was investigated by XPS analysis and kinetic experiments. The ubiquitous arsenic in groundwater poses a great risk to human health due to its environmental toxicity and carcinogenicity. In the present work, a new adsorbent, δ-MnO 2 modified activated carbon, was prepared, and its performance for the uptake of arsenate and arsenite species from aqueous solutions was investigated by batch experiments. Various techniques, including FESEM-EDX, p-XRD, XPS and BET surface area analysis, were employed to characterize the properties of the adsorbent and the arsenic adsorption mechanisms. The results showed that δ-MnO 2 covered on the surface and padded in the pores of the activated carbon. Adsorption kinetic studies revealed that approximately 90.1% and 76.8% of As(III) and As(V), respectively, were removed by the adsorbent in the first 9 hr, and adsorption achieved equilibrium within 48 hr. The maximum adsorption capacities of As(V) and As(III) at pH 4.0 calculated from Langmuir adsorption isotherms were 13.30 and 12.56 mg/g, respectively. The effect of pH on As(V) and As(III) removal was similar, and the removal efficiency significantly reduced with the increase of solution pH. Arsenite oxidation and adsorption kinetics showed that the As(V) concentration in solution due to As(III) oxidation and reductive dissolution of MnO 2 increased rapidly during the first 12 min, and then gradually decreased. Based on the XPS analysis, nearly 93.3% of As(III) had been oxidized to As(V) on the adsorbent surface and around 38.9% of Mn(IV) had been reduced to Mn(II) after As(III) adsorption. This approach provides a possible method for the purification of arsenic-contaminated groundwater. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Millions of people in the world are exposed to arsenic-contaminated groundwater. To decrease the concentration of arsenic in water, adsorption of arsenic was performed on a simple and easily available material, that is, eggshell. Powdered eggshell (ES) was prepared and was characterized by using Brunauer–Emmett–Teller, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy, and energy-dispersive X-ray spectroscopy (EDX). It was revealed from FTIR and EDX that the presence of CaCO3 in ES is the major reason for arsenic adsorption. Removal of As(III) and As(V) as a function of the adsorbent dose, pH, contact time, and agitation speed were studied. The adsorption capacity is strongly influenced by the pH of the solution. ES removed 68.54% of As(III) and 72.01% of As(V) under optimum conditions from 2 mg/L As(III) and As(V) solutions. ES was also carbonized at 700°C, and it could remove 70.09% of As(III) and 76.44% of As(V) under similar conditions. Adsorption isotherms and kinetics were determined for As(III) and As(V). As(III) adsorption followed the Langmuir isotherm, revealing monolayer adsorption. As(V) adsorption followed the Freundlich isotherm, revealing multilayer adsorption. Similarly, adsorption of As(III) and As(V) on carbonized eggshell followed pseudo-second-order kinetics and on ES followed Elovich kinetics, both suggesting that the adsorption process is a chemisorption process. Also, the study of the intraparticle diffusion model concluded that there was surface adsorption along with an intraparticle diffusion mechanism during the adsorption of arsenic. The best isotherm and kinetic models were selected, based on the error values using the chi-square test, root mean square error, and average percentage error. [ABSTRACT FROM AUTHOR]

In this study, Pinus roxburghii cones were used for the removal of arsenite from aqueous solutions. Activated carbon was prepared from these cones with further activation of it with H3PO4 (1:1), KOH (1:3) and 0.5 M FeSO4. Preliminary experiments show that no significant removal of arsenite took place by using raw carbon and its activation with H3PO4 and KOH while activated carbon modified with 0.5 M FeSO4 gives maximum removal of arsenite (99%). So further experiments were carried out by using activated carbon with 0.5 M FeSO4 (Fe-GAC). Its surface properties were investigated in terms of surface area, particle size, moisture, ash contents, cation exchange capacity, pHPZC, and elemental analysis through. The removal experiments of arsenite were carried out by the sorption technique in a batch system. Competitive sorption of arsenite in the presence of various metals like V, Cr, Co, Cu, Se, Cd, Ba, Tl, Be, Pb, and Ni was also investigated with an adsorbent dosage range of 0.2–1.5 g. Hydride generation-atomic fluorescence spectrometry and inductively coupled plasma-mass spectrometry technique was used for the analysis of arsenite and other metals in aqueous solutions. The adsorption of arsenite was pH-dependent. The kinetics of adsorption was examined in terms of the pseudo-first-order and pseudo-second-order. The adsorption data were applied to the well-known Langmuir, Freundlich, and Temkin isotherm models. Thermodynamic parameters (∆H°, ∆S°, and ∆G°) were calculated from the slope and intercept of plots of lnKD vs. 1/T at different temperatures of 298, 313 and 323 K. [ABSTRACT FROM AUTHOR]

Arsenic contamination has been considered as one of the serious environmental issues around the world. In this study, the conventional chemical coagulation was applied as pretreatment of the nanofiltration process to enhance the removal efficiency of arsenite (As(III)) and arsenate (As(V)) and mitigate the membrane fouling. Three types of coagulants including aluminum chloride (AlCl3), polyaluminium chloride and ferric chloride (FeCl3) were compared. More than 80% of As(V) could be removed by coagulation, nanofiltration, and their combined process, whereas nanofiltration or coagulation using aluminium-based coagulants only achieved approximately 10% of removal efficiency of As(III). FeCl3 was proven to be the most effective coagulant to remove both As(V) and As(III) with the removal efficiency of 99% and 95%, respectively. The coagulation pretreatment was able to significantly reduce the declining trend of water flux. The formed fouling layer on the membrane surface after the treatment was investigated by a field-emission scanning electron microscopy. Compared to the case of direct filtration of humic acid solution, a more loose and permeable fouling layer could be formed when coagulation was used as a pretreatment process. [ABSTRACT FROM AUTHOR]

Ligands may increase the yields of reactive oxygen species (ROS) in zero-valent iron (ZVI)/O 2 systems. To clarify the relationship between the properties of ligands and their effects on the oxidative removal of contaminants, five common ligands (formate, acetate, oxalate, ethylenediaminetetraacetic acid (EDTA), and phosphate) as well as acetylacetone (AA) were investigated with arsenite (As(III)) as the target contaminant at three initial pH values (3.0, 5.0, and 7.0). The addition of these ligands to the ZVI/O 2 system resulted in quite different effects on As(III) removal. EDTA enhanced the oxidation of As(III) to arsenate (As(V)) but inhibited the removal of As(V). Oxalate was the only ligand in this work that accelerated both the removal of As(III) and As(V). By analyzing the ligand effects from the four aspects: dissolution of surface iron (hydr)oxides, corrosion of ZVI, reaction with ROS, and interference with precipitation, the following properties of ligands were believed to be important: ability to provide dissociable protons, complexation ability with iron, and reactivity with ROS. The complexation ability is a double-edged sword. It could enhance the generation of ROS by reducing the reduction potential of the Fe(III)/Fe(II) redox couple, but also could inhibit the removal of arsenic by coprecipitation. The elucidated relationship between the key property parameters of ligands and their effects on the ZVI/O 2 system is helpful for the rational design of effective ZVI/ligand/O 2 systems. Unlabelled Image [ABSTRACT FROM AUTHOR]

Arsenic contamination is widespread in water bodies and poses a significant risk to human health, thus developing a rapid and inexpensive in situ method for the detection of arsenic is urgently needed. In this study, a chitosan-catechol carbon paper electrode was fabricated by electrodeposition of chitosan on a conductive carbon paper and subsequential electro-oxidative grafting of catechol. This chitosan-catechol modified electrode demonstrated good performance in detecting trace amounts of arsenic, which is mainly due to the significantly amplification of oxidation signals generated by ferrocene (Fc) on chitosan-catechol hydrogel. The interaction of As(III) with quinone and semiquinone radicals results in the decrease of electronic transmission nodes. The modified electrode exhibited a good detection capability of low concentration As(III) with a detection limit 0.82 ppb by differential pulse voltammetry (DPV). In addition, the chitosan-catechol modified sensor has the merits of high reproducibility, durability and strong resistance to ionic interference. Further successful detection of As(III) in actual rice and soil samples suggests its good potential in the field of in situ detection. [Display omitted] • Modified paper sensor was constructed by catechol grafting without gold modification. • The redox of catechol allows a significant amplification of oxdation signals. • Modified paper sensor achieves a LOD of 0.82 ppb for As(III) detection. • Actual rice and soil samples can be analyzed by the modified paper sensors. [ABSTRACT FROM AUTHOR]

The persistent and photo-induced free radicals of biochar play significant roles in the transformation or degradation of inorganic and organic pollutants. However, the redox capacity of biochar for arsenite (As(III)) photochemistry under different pH conditions remains unclear. In this study, we discovered that solar radiation primarily expedited the oxidation of As(III) by biochar by augmenting the production of reactive oxygen species (ROS). Biochar demonstrated a strong pH reliance on the photooxidation of As(III). Under acidic and neutral conditions, solar radiation amplified the generation of •OH (hydroxyl radicals) by BC-P (phenolic −OH of biochar) and semiquinone-type BC-PFRs (persistent free radicals of biochar) by 4.9 and 2.0 times, respectively, resulting in enhanced As(III) oxidation. Under alkaline conditions, BC-P and BC-Q (quinoid C O of biochar) facilitated the production of H 2 O 2 (hydrogen peroxide) by 2.1 times through the spontaneous formation of semiquinone-type BC-PFRs via an anti-disproportionation reaction, promoting approximately 88.2% of As(III) photooxidation. Furthermore, solar radiation elevated around 11.8% As(III) oxidation driven by BC-Q and semiquinone-type BC-PFRs. This study provides a crucial theoretical foundation for using biochar to treat arsenic pollution in aquatic systems and understanding the migration and transformation of arsenic in different environments. [Display omitted] • Simulated solar lights greatly increased As(III) oxidation by biochar. • Solar lights increased ROS production by stimulating phenolic −OH and PFRs on biochar. • •OH and H 2 O 2 were critical in As(III) photooxidation by biochar. • The photooxidation mechanism of As(III) by biochar at varying pHs was proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Three-dimensional porous MIL-88A-Fe/gelatin aerogel (PMGA) was prepared. • The PMGA/H 2 O 2 system has dual functions of oxidation and adsorption. • Surface •OH and surface •OOH are the main oxide species of As(III). • The Fenton-like catalytic activity of PMGA originates from the exposed (1 0 0) facet. • PMGA can effectively repair the arsenic pollution in different real water samples. Metal-organic frameworks (MOFs) are considered a reliable adsorbent for controlling arsenic contamination. However, developing rapid and efficient MOF adsorbents with the capability of easy recovery is still challenging. Herein, we prepared a three-dimensional porous MIL-88A-Fe/gelatin aerogel (PMGA) with macroscopic size and coupled it with H 2 O 2 to fabricate a heterogeneous catalytic oxidation adsorption system to remove As(III) in water. The green synthesis strategy of this catalyst by foaming and low-temperature carbonization not only avoided the use of toxic chemical crosslinkers but also endowed PMGA with a rich hierarchical porous structure and exposed more active sites. Thus, the PMGA/H 2 O 2 system was able to reduce the concentration of As(III) from 1106 to below 10 µg/L and simultaneously realize the complete oxidation of As(III) to As(V) in only 120 min. Meanwhile, the system exhibited an excellent saturation adsorption capacity (24.863 mg/g) for As(III), superior to most similar bio-based or iron-based materials. Quenching experiments, EPR and DFT calculations showed that the active species (surface •OOH and surface •OH) generated by the Fenton-like interaction between the exposed (1 0 0) facet of MIL-88A-Fe in PMGA and H 2 O 2 played an essential role in promoting the oxidative removal of As(III). Moreover, the reaction system could work efficiently for As(III) in a wide pH range and was hardly affected by other substances such as chlorides, sulfates, carbonates, silicates, and humic acids. Simultaneously, the fixed bed column filled with PMGA could stably and continuously treat As(III) in groundwater. Therefore, this study not only broadens the horizon for the development and design of 3D functional materials but also provides a new strategy in water purification to eliminate arsenic pollutants using Fe-MOF aerogels. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fine-grained CoFe 2 O 4 nanoparticles are facilely anchored on porous carbon. • Porous carbon boosts the mass transfer efficiency and prevents Co and Fe leaching. • CoFe 2 O 4 @PC facilitates the simultaneous removal of TC and As(III) via PMS activation. • Radical and nonradical pathways contribute to the oxidation of TC. • The degradation pathways and toxicity analysis of TC are proposed. The coexistence of tetracycline (TC) and arsenite (As(III)) in livestock wastewater threatens public health, and the heterogeneous Fenton-like system is a practical approach for the simultaneous removal of TC and As(III). In this work, fine CoFe 2 O 4 nanoparticles are facilely anchored on heretically porous carbon (CoFe 2 O 4 @PC) via a microwave-assisted calcination method and used for eliminating TC and As(III) via peroxymonosulfate (PMS) activation. The CoFe 2 O 4 @PC/PMS system exhibits excellent performance in the simultaneous removal of 96% of 10 mg/L TC and 86% of 50 μM As(III) within 30 min, whereas the porous carbon can boost the mass transfer efficiency and protect CoFe 2 O 4 against Co and Fe ions leaching. The CoFe 2 O 4 @PC/PMS system maintains satisfactory activity and stability in a broad pH range (3–11) and anti-interference capacity (anions, humic acid and water matrices). Meanwhile, the CoFe 2 O 4 @PC with the strong magnetic property was readily recovered from the reaction solution. Moreover, the cooperation of radical (·OH, ·SO 4 - and ·O 2 –) and nonradical (1O 2) pathways was documented to play critical roles in enhancing the oxidation of TC and As(III), which effectively reduces the toxicity of degradation intermediates. This work offers a facile strategy for constructing spinel-based catalysts and opens a broad prospect for removing TC and As(III) in livestock wastewater. [ABSTRACT FROM AUTHOR]

• Synergetic interactions between ZVI and Sch during premixing process existed. • Premixing time and mass ratio played essential roles in As(III) removal. • Mass and electron transfer occurred between Sch and ZVI during the premixing. • Recrystallization of Sch and the corrosion process of ZVI were accelerated. • As(III) removal capacity of ZVI/Sch mixtures improved by premixing. Although the enhanced removal of heavy metals using zero valent iron (ZVI) assisted by schwertmannite (Sch) was achieved in previous studies, their interactions between Sch and ZVI seems to be bidirectional and impact on the As(III) removal by ZVI/Sch mixture remains elusive. This study investigated As(III) removal in the mixed suspensions of ZVI and Sch with various premixing times and mass ratios. Batch experiments demonstrated that ZVI/Sch mixture with the premixing time of 3 h and mass ratio of 2:1 exhibited excellent performance in As(III) removal. The results indicated that synergetic interactions between ZVI and Sch during premixing process played crucial roles, particularly in terms of morphological variations. Results of FTIR and XPS revealed the mass and electron transfer occurred between Sch and ZVI during the premixing process, resulting in the accelerated recrystallization of Sch and the corrosion process of ZVI. Furthermore, the premixing process was found to significantly improve the As(III) removal capacity of ZVI/Sch mixture without altering the As(III) removal pathway, including the adsorption/precipitation/oxidation processes of ZVI and surface complexation/ion exchange/channels inlay of Sch. These findings shed light on the complex interactions between ZVI and Sch in As(III) removal and offer promising opportunities for the development of efficient treatment strategies in As(III)-contaminated environments. [ABSTRACT FROM AUTHOR]

• Arsenite increases the levels of MALAT1 during arsenite-induced liver fibrosis in mice. • MALAT1 is shuttled from arsenite-treated liver cells to hepatic stellate cells via exosomes. • Exosomal MALAT1 promotes the activation of hepatic stellate cells via miR-26b regulation of COL1A2 in hepatic stellate cells. In the liver microenvironment, interactions among diverse types of hepatic cells are involved in liver fibrosis. In fibrotic tissues, exosomes act as transporters in intercellular communication. Long non-coding RNAs (lncRNAs) are involved in the activation of hepatic stellate cells (HSCs), which are participants in liver fibrosis. However, the functions of exosomal lncRNAs in liver fibrosis induced by arsenite are undefined. The purposes of the present study were (a) to determine if lncRNAs secreted from human hepatic (L-02) cells exposed to arsenite are shuttled to hepatic stellate LX-2 cells and (b) to establish their effects on LX-2 cells. In mice, MALAT1 was overexpressed in the progression of liver fibrosis induced by arsenite as well as in L-02 cells exposed to arsenite. Co-cultures with arsenite-treated L-02 cells induced the activation of LX-2 cells and overexpression of MALAT1. Arsenite-treated L-02 cells transported MALAT1 into LX-2 cells. Downregulation of MALAT1, which reduced the MALAT1 levels in exosomes derived from arsenite-treated L-02 cells, inhibited the activation of LX-2 cells. Additionally, exosomal MALAT1 derived from arsenite-treated L-02 cells promoted the activation of LX-2 cells via microRNA-26b regulation of COL1A2. Furthermore, circulating exosomal MALAT1 was up-regulated in people exposed to arsenite. In sum, exosomes derived from arsenite-treated hepatic cells transferred MALAT1 to HSCs, which induced their activation. These findings support the concept that, during liver fibrosis induced by arsenite, exosomal lncRNAs are involved in cell-cell communication. [ABSTRACT FROM AUTHOR]

• In utero and early life exposure to As and F affects kidney ultrastructure. • Exposure to As and F alone or combined causes oxidative stress in kidney tissue. • As exposure but not F alters the Nrf2 pathway-related signaling molecules. • Concurrent As and F exposure may produce a joint action on the toxicity of kidney. Unlabelled Image Underground drinking water is commonly contaminated with arsenite (As) and fluoride (F) associated with chronic kidney diseases in humans; however, the combined renal toxicity of these pollutants and the underlying mechanisms are still unclear. The aim of the present study was to investigate the interaction between As and F regarding toxic effects on the kidney of rat offspring exposed to pollutants during prenatal and postnatal development. Pregnant rats were randomly divided into four groups that received NaAsO 2 (50 mg/L), NaF (100 mg/L), NaAsO 2 (50 mg/L) and NaF (100 mg/L) in drinking water, or clean water, respectively, during gestation and lactation. After weaning, six male pups were randomly selected from each group and continued on the same treatment as their mothers for up to three months. The results revealed that subchronic exposure to high-dose As and/or F decreased the organ coefficient of the kidneys and disrupted kidney ultrastructure, moreover inhibited the activity of antioxidant enzymes and increased the generation of malondialdehyde in the kidney. As exposure alone or combined with F led to an upregulation of nuclear factor erythroid 2-related factor-2 (Nrf2) and its regulatory targets (Ho-1, Gclc, and Nqo1), whereas the effect of F alone was not significant. These results suggest that the renal toxicity of As and F is associated with the induction of mitochondrial damage and oxidative stress, and alters the expression of Nrf2 and its regulatory targets. Furthermore, variance analysis results showed that an interaction between As and F in the toxicity process. [ABSTRACT FROM AUTHOR]

The measurement of arsenic has received considerable attention due to its contaminant to environment and harm on human safety. This paper provides an overview of optical methods on the measurement of inorganic arsenic (arsenite and arsenate). We present and discuss the colorimetric, scattering, and fluorimetric strategies for inorganic arsenic detection based on the organic/biological molecules and their coupling with inorganic nanomaterials. The detection mechanism for arsenite and arsenate is summarized and the advantages/limitations are highlighted in the present review. In addition, prospects and future developments of optical sensors for arsenic analysis are also proposed. • Different optical methods for arsenics were reviewed. • The detection mechanism of optical methods was summarized. • The sensors with organic/biological molecules and nanomaterials were described. • The challenges and prospects in arsenic analysis were discussed. [ABSTRACT FROM AUTHOR]

A new set of chromogenic anion receptors R1-R4 have been synthesized with a different substituent, including electron withdrawing (nitro moiety in R1), conjugated group (naphthyl in R2), and electron donating (methyl in R3), respectively. The receptors R1-R4 exhibited very good sensitivity towards the F− and AcO− anions in the DMSO. In addition, R1 showed selectivity towards H 2 PO 4 − ions over other tested anions. R1 especially acted as an effective sensor for sodium salts of F−, AcO−, AsO 2 −, and AsO 4 2− ions in an aqueous medium due to the presence of two electron-withdrawing nitro substituents, which showed hydrogen bond donor tendency and acidity of the OH proton. This result indicates that R1 is highly capable of competing with an aqueous medium to detect anions without counter Na+ ion interference. Interestingly, R1 displays solvatochromic property in the presence of AcO− ions in different aprotic solvents. Additionally, the receptor R1 shows high binding affinity towards AcO− ions in the buffer medium (DMSO: HEPES, 9:1 v /v), which displayed remarkable colour change from pale yellow to blue with a large ∆λ red shift of 170 nm. The CV studies reveal the deprotonation of the -NH proton upon interaction with the AcO− ions. The receptor R1 is subjected to practical application to sense F− and AsO 2 − ions using the test strip. In addition, the receptor R1 proves itself as a potential applicant for the detection of F− ions quantitatively in commercially available mouthwash. Unlabelled Image • R1-R4 prepared for the detection of biologically important anions. • Synthesized receptor R1-R4 characterized by 1HNMR, 13CNMR, FTIR, and MS. • R1 showed LOD for Na +F− 0.392 ppm which is a far lower than WHO guideline (1 ppm). • R1 demonstrated real-life application for qualitative detection of F− in mouthwash. • Binding mode of R1 analyzed by UV–vis, 1H NMR titration, and CV studies. [ABSTRACT FROM AUTHOR]

Arsenic (As) tends to mobilize in flooded paddy soil due to the reductive dissolution of the iron (oxyhydr)oxides to which As sorbs, resulting in elevated As accumulation in rice that poses a potential risk to the food safety and human health. Microbial sulfate reduction is an important biogeochemical process in paddy soils, but its impact on As mobilization remains poorly understood. In this study, we incubated eight As-contaminated paddy soils under flooded conditions to investigate the effect of sulfate addition on As mobility. Porewater Fe and As concentrations and As species were determined. Among the eight soils, an addition of 50 mg S kg−1 as sodium sulfate decreased porewater arsenite only in two soils, which also showed a high mobilization of Fe2+. Further experiments showed that the addition of sulfate to these two soils stimulated microbial sulfate reduction but decreased porewater concentrations of both arsenite and Fe2+. Additionally, the supply of sulfate increased the fractions of As associated with acid volatile sulfides in the solid phase and decreased As uptake by rice in pot experiments under similar conditions. The effect of sulfate addition on porewater As was diminished by the addition of molybdate, an inhibitor of sulfate reducing bacteria. These results suggest the formation of secondary FeS minerals which co-precipitate or sorb arsenite as a likely mechanism of As immobilization, which was also supported by thermodynamic modeling of the pore water. Thus, sulfate additions can immobilize As and reduce its availability to rice plants in paddy soils containing a high potential for microbial Fe reduction, providing an efficient way to mitigate the As transfer to the food chain. Image 1 • Sulfate addition decreased soluble As(III) in paddy soils with high soluble Fe2+. • Inhibition of sulfate reduction diminished the decrease in soluble As(III). • The decrease in soluble As(III) was due to the adsorption to secondary FeS. • Sulfate addition to paddy soils with high reducible Fe reduced rice grain As. Sulfate addition can reduce As mobility in paddy soils containing a high potential of microbial Fe reduction, offering a potential strategy to mitigate grain As accumulation in these soils. [ABSTRACT FROM AUTHOR]

• To the best of our knowledge, it is the first report about the adsorption kinetics of arsenic on β-MnO 2 surface. • Based on the new discovery in the present study, a new oxidation mechanism has been suggested. • Two kinds of β-MnO 2 with high potential of decrease arsenic are suggested in the present study. MnO 2 is one of the most widespread and cheapest materials in nature that can both adsorb arsenic and oxidize arsenite [As(III)] to arsenate [As(V)]. In this study, column β-MnO 2 [CM] with the main facet of {110} and pincer β-MnO 2 [PM] with the facets of {110} and {101} are synthesized and used to remove arsenic in water under different conditions. For the adsorption process, the experimental data are fitted well with the pseudo second-order kinetic model; the Langmuir model is better than the Freundlich model to describe the adsorption equilibrium isotherms. Furthermore, the As(III) oxidation rate can be denoted by the pseudo zero-order kinetic model and is related to the O 2 concentration, the pH value, the light source and the initial concentration of As(III). Finally, the oxidation mechanism is investigated, and the oxidant should be related to O 2. It is interesting to find that these two kinds of β-MnO 2 exhibit different pH effects for both adsorption and oxidation. For As(III), the adsorption and oxidation abilities of CM follow the order pH 9 > pH 7 > pH 4, whereas the adsorption and oxidation orders of PM are pH 4 > pH 7 > pH 9. [ABSTRACT FROM AUTHOR]