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• Ferrihydrite-biochar composite simultaneously removed Cd(II) and As(V). • As(V) presence promoted Cd(II) retention in the ferrihydrite-biochar composite. • The distribution of Cd(II)/As(V) in single system is different in the ferrihydrite-biochar composite. • Cd(II) and As(V) were closely associated with ferrihydrite in the mixed Cd&As system. The coexistence of cadmium (Cd(II)) and arsenate (As(V)) pollution has long been an environmental problem. Biochar, a porous carbonaceous material with tunable functionality, has been used for the remediation of contaminated soils. However, it is still challenging for the dynamic quantification and mechanistic understanding of the simultaneous sequestration of multi-metals in biochar-engineered environment, especially in the presence of anions. In this study, ferrihydrite was coprecipitated with biochar to investigate how ferrihydrite-biochar composite affects the fate of heavy metals, especially in the coexistence of Cd(II) and As(V). In the solution system containing both Cd(II) and As(V), the maximum adsorption capacities of ferrihydrite-biochar composite for Cd(II) and As(V) reached 82.03 µmol/g and 531.53 µmol/g, respectively, much higher than those of the pure biochar (26.90 µmol/g for Cd(II), and 40.24 µmol/g for As(V)) and ferrihydrite (42.26 µmol/g for Cd(II), and 248.25 µmol/g for As(V)). Cd(II) adsorption increased in the presence of As(V), possibly due to the changes in composite surface charge in the presence of As(V), and the increased dispersion of ferrihydrite by biochar. Further microscopic and mechanistic results showed that Cd(II) complexed with both biochar and ferrihydrite, while As(V) was mainly complexed by ferrihydrite in the Cd(II) and As(V) coexistence system. Ferrihydrite posed vital importance for the co-adsorption of Cd(II) and As(V). The different distribution patterns revealed by this study help to a deeper understanding of the behaviors of cations and anions in the natural environment. [Display omitted] [ABSTRACT FROM AUTHOR]

Current models for inorganic ion transport in porous media describe the adsorption–desorption processes mostly based on empirical adsorption isotherms or simple thermodynamic mechanisms, often overlooking the adsorption kinetics. This study introduces a novel unified reactive solute transport model framework that incorporates well-established surface complexation models to describe the adsorption–desorption of ions in the transport process and takes into full consideration the non-equilibrium adsorption, enabling the use of the same set of thermodynamic-kinetic parameters to accurately describe ion transport under different chemical conditions. To evaluate the constructed model, Cr(VI), P(V), and As(V) column transport experiments were carried out using goethite-coated sand as the porous medium. Kinetic constants derived from single-ion transport experiments accurately predicted the cotransport behaviors of Cr(VI), P(V), and As(V) under various flow chemistry conditions, especially the overshooting phenomena of Cr(VI) under P(V) and As(V) competition. The model framework can be easily incorporated into solute transport models with various surface complexation reactions to predict the fate and transport of ions under complexed chemical conditions without extensive parameterization, and thus is a useful complement to the current reactive transport model. [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]

Little information is available on influences of the conversion of dissolved organic phosphorus (DOP) to inorganic phosphorus (IP) on algal growth and subsequent behaviors of arsenate (As(V)) in Microcystis aeruginosa (M. aeruginosa). In this study, the influences factors on the conversion of three typical DOP types including adenosine-5-triphosphate disodium salt (ATP), β-glycerophosphate sodium (βP) and D-glucose-6-phosphate disodium salt (GP) were investigated under different extracellular polymeric secretions (EPS) ratios from M. aeruginosa , and As(V) levels. Thus, algal growth, As(V) biotransformation and microcystins (MCs) release of M. aeruginosa were explored in the different converted DOP conditions compared with IP. Results showed that the three DOP to IP without EPS addition became in favor of algal growth during their conversion. Compared with IP, M. aeruginosa growth was thus facilitated in the three converted DOP conditions, subsequently resulting in potential algal bloom particularly at arsenic (As) contaminated water environment. Additionally, DOP after conversion could inhibit As accumulation in M. aeruginosa , thus intracellular As accumulation was lower in the converted DOP conditions than that in IP condition. As(V) biotransformation and MCs release in M. aeruginosa was impacted by different converted DOP with their different types. Specifically, DMA concentrations in media and As(III) ratios in algal cells were promoted in converted βP condition, indicating that the observed dissolved organic compositions from βP conversion could enhance As(V) reduction in M. aeruginosa and then accelerate DMA release. The obtained findings can provide better understanding of cyanobacteria blooms and As biotransformation in different DOP as the main phosphorus source. Graphical Abstract [Display omitted]. [ABSTRACT FROM AUTHOR]

The abiotic reactions of Fe(II) oxidation and nitrite (NO 2 –) reduction (chemodenitrification) are a vital geochemical processes at the interface of anoxic sediments and water. Chemodenitrification leads to the formation of secondary iron (Fe)-bearing minerals, which can influence the dynamic behavior of arsenate (As(V)). However, the coupled mechanism and pH effect of chemodenitrification and As(V) sequestration are not well understood. Here, immobilization of As(V) was investigated at pH 5.5, 6.5, and 8.0 during chemodenitrification. Kinetics of 9 mM Fe(II) oxidation and 3 mM nitrite reduction increased with increasing pH but decreased in the presence of 0.5 mM As(V). The results of X-ray diffraction and linear combination fitting of the Fe K-edge EXAFS spectra together showed that high pH and low As(V) were favorable for the formation of secondary crystalline Fe oxides, such as lath-like lepidocrocite, rod-like goethite, and nano-magnetite. Despite efficient removal, the retention of As(V) species on the newly-formed secondary Fe minerals varied substantially at different pH values. Microscopic and spectroscopic analyses at nano- and molecular-scales revealed that As(V) was mainly adsorbed onto poorly crystalline Fe minerals at pH 5.5, while it was partially incorporated into the lattice structure of crystalline Fe minerals through isomorphic substitution at pH 6.5 and 8.0. The amount of As(V) sequestration was positively correlated with newly-formed crystalline Fe minerals. A model was established by integrating Fe mineral transformation and nonlinear As(V) binding to various Fe minerals, which could accurately predict distribution of adsorbed As(V). The pH increase during chemodenitrification promoted immobilization of As(V) in newly-formed crystalline Fe minerals. The findings on pH-dependent chemodenitrification with As have significant implications for understanding the long-term solubility and migration of As(V), and could provide a potential strategy for As immobilization in sediments. [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]

Iron oxide minerals control the environmental behavior of trace elements. However, the potential effects of electron transfer directions by iron oxides between organic acids and trace elements remain unclear. This study investigates the redox capacity of tartaric acid (TA) with chromate (Cr(Ⅵ)) or arsenate (As(V)) on lepidocrocite (Lep) from the perspective of electron transfer. The results demonstrated the configurations of TA (bidentate binuclear (BB)), As(V) (BB), and Cr(Ⅵ) (BB and protonated monodentate binuclear (HMB)) on Lep. Frontier molecular orbital calculations and X-ray photoelectron spectroscopy (XPS) binding energy shifts further indicated different electron transfer directions between TA and the oxyanions on Lep. The iron of Lep might act as electron acceptors when TA is adsorbed, whereas the iron and oxygen of Lep act as electron donors when As(V) is adsorbed. The iron of Lep might accept electrons from its oxygen and subsequently transfer these electrons to Cr(Ⅵ). Macroscopic validation experiments showed the reduction of Cr(VI), whereas no reduction of As(V). The XPS analysis showed a peak shift, with the possible formation of As–Fe–TA ternary complexes and electron transfer on Lep. These findings indicate that mineral interfacial electron transfer considerably influences the transport and transformation of oxyanions. [Display omitted] • Interfacial interactions between Lep and oxyanions (As(V) or Cr(VI)) in the presence of TA were studied. • Lep acts as an electron acceptor when TA is adsorbed. • Lep acts as an electron donor with different pathways when only Cr(Ⅵ) or As(V) is adsorbed. • The Lep–TA + Cr(VI) system reduced Cr(VI) to 30 % compared to 9 % in the presence of only TA. [ABSTRACT FROM AUTHOR]

Arsenic is widely present in the environment in trivalent and pentavalent forms; long-term arsenic exposure due to environmental pollution has become a problem. Previous reports have shown that 24-h exposure to arsenate (as pentavalent arsenic) potentiates erythropoietin (EPO) production via reactive oxygen species (ROS) in EPO-producing HepG2 cells. However, the effects of long-term arsenate exposure on EPO production remain unclear. In HepG2 cells subcultured for 3 weeks in the presence of arsenate, EPO mRNA levels were lower than those in untreated cells. Levels of ARSENITE METHYLTRANSFERASE mRNA, as well as those of Nuclear factor erythroid 2-related factor 2, glutathione, and superoxide dismutase proteins, were increased compared to untreated cells, but levels of malondialdehyde were not significantly altered. Thus, long-term exposure to arsenate enhances ROS scavenging, suggesting that the ROS-induced accumulation of EPO mRNA is attenuated by arsenate exposure. The induction of EPO accumulation by hypoxia also was attenuated by long-term arsenate exposure, suggesting an impairment in responsivity of EPO production. Furthermore, mRNA levels of SIRTUIN-1 , which affects EPO transcription, were potentiated by long-term arsenate exposure. These results suggest that long-term arsenate exposure has multiple, distinct effects on EPO production in vitro. [Display omitted] • Long-term arsenate exposure suppresses EPO production in HepG2 cells. • Long-term arsenate exposure leads to oxidative stress. • Long-term arsenate exposure leads to a sustained increase in ROS scavenging. • Promotion of EPO production by hypoxia is impeded by arsenate treatment. • Arsenate-mediated upregulation of SIRT1 attenuates EPO production. [ABSTRACT FROM AUTHOR]

Arsenic and cadmium contamination, along with their associated environmental risks, is a global concern, and the synergistic stabilization of cations and oxyanions in contaminated environments is challenging. In this study, goethite-modified biochar (BC-Gt) was synthesized and investigated for its remediation potential in co-contamination of cadmium (Cd) and arsenic (As), compared to pristine reed-straw biochar (BC) and goethite (Gt). BC-Gt exhibited the highest maximum adsorption capacities in the binary As and Cd solution (As: 126.02 mg·g−1, Cd: 125.12 mg·g−1). BET-SSA, SEM-EDS, XRD, FTIR and XPS analyses revealed various mechanisms of co-adsorption of As and Cd on BC-Gt, including ion exchange, electrostatic interaction, surface precipitation and complexation. Moreover, the specific adsorption of Cd(II) involved cation-π interaction, while limited oxidation-reduction of As(V) occurred during adsorption. BC-Gt also displayed profound stabilization effects in As, Cd and lead (Pb) co-contaminated soils, with maximum removal efficiencies of 63.98 %, 83.67 % and 83.92 %, respectively. BC-Gt outperformed BC and Gt in transforming the exchangeable fraction (Exc) into reducible (Red), oxidizable (Oxi) and residual (Res) fractions of As, Cd and Pb. This study provides evidence in the potential of BC-Gt for remediating co-contamination of As and Cd in water, as well as As, Cd and Pb in soil. [Display omitted] • Goethite-modified biochar (BC-Gt) adsorbing mixed As(V) and Cd(II) solution was tested. • Ion exchange, electrostatic interaction, and precipitation were the common mechanisms. • Cd(II) involved in cation-π interaction while As(V) had reduction. • BC-Gt effectively immobilized As, Cd and Pb from the co-contaminated soils. • BC-Gt transformed exchangeable into other relatively immobile fractions of As, Cd and Pb. [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]

[Display omitted] • A new method for the synthesis of Nd-doped MIL at room temperature. • Nd-MIL-100 as a novel adsorbent for the simultaneous capture of P/As(V). • Nd doping enhances the electronic structure and surface properties of MIL-100. • Electrochemical characterization reveals the charge transfer mechanism. • The adsorption mechanism of 0.5Nd-MIL-100 on P/As(V) was revealed by DFT. Although they are effective adsorbents for removing phosphorus and arsenic, metal–organic frameworks are limited by their harsh synthesis conditions, slow adsorption kinetics, and low adsorption capacities. Herein, a Nd-doped, chemically-active MIL-100(Fe) was developed using a room-temperature rare-earth doping strategy and then used to adsorb phosphate and As(V). Room-temperature rare-earth doping was carried out in water using mild synthesis conditions, which reduced the energy consumption and environmental pollution. Electrochemical tests showed that Nd doping provided additional electron transfer pathways that increased the conductivity of the material and its number of surface active sites. Thermodynamic calculations and isotherm analyses revealed that Nd-MIL-100 exhibited favorable adsorption characteristics for phosphate and As(V) and that the adsorption process was endothermic and spontaneous at various temperatures. The adsorption data were fitted by the Langmuir isotherm and pseudo-second-order model, and the maximum adsorption capacities of Nd-MIL-100 for phosphate and As(V) were 256.72 mg/g and 177.28 mg/g, respectively. The Nd-MIL-100 adsorbent maintained a high selectivity for As(V) and phosphate in both simulated and actual water samples. The Boyd monovalent ion exchange model, which considers variations in adsorption energy and equilibrium concentrations while maintaining charge neutrality, provided a better understanding of the adsorption behavior. Density functional theory (DFT) calculations showed that Nd doping significantly changed the electronic structure of MIL-100, leading to the spin polarization of electronic states and enhanced chemical activity. Spectroscopy, electrochemical tests, and DFT calculations confirmed that the adsorption of As(V) and phosphate by Nd-MIL-100 involved multiple mechanisms. This study explores a new way to improve the practicability of environmental remediation materials. [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]

• A biocompatible UiO-66- g - q P4VP/PAN nanofiber membrane was prepared. • Abundant quaternary ammonium groups provides a large number of adsorption sites. • The membrane could potentially maintain its functionality across a broad pH range. • The nanofiber membrane possesses superior adsorption capacity for arsenate removal. In this work, the metal–organic framework (MOF) particles (i.e., UiO-66-NH 2) was covalently modified with poly(4-vinylpyridine) (P4VP) through surface-initiated atom transfer radical polymerization (SI-ATRP) method. The hair MOF product, referred to as UiO-66- g -P4VP, was then subjected to quaternization with 1-bromoethane, resulting in UiO-66-g- q P4VP (quaternized P4VP is denoted as q P4VP). Finally, these UiO-66-g- q P4VP particles were incorporated into a polymer matrix made of polyacrylonitrile (PAN) to develop a nanofibrous composite membrane using the electrospinning technique. After modification of quaternized P4VP, the surface of the MOFs carry strong positive charges. Therefore, the electrospun UiO-66- g - q P4VP/PAN nanofiber membrane can serve as an adsorbent in efficient removal of negatively charged arsenate through strong electrostatic interactions. The adsorptive efficacy of the nanofiber membrane exhibited considerable stability within the pH spectrum extending from 4 to 10, indicating that the membrane could potentially maintain its functionality across a broad range of pH conditions. Our developed approach opens up an avenue for manufacturing of polyelectrolyte-functionalized MOF nanofiber membranes, which hold great promise for application in water remediation. [ABSTRACT FROM AUTHOR]

• Surface species content was used to construct species-informed model. • The equilibrium and kinetic data were used to train species-informed model. • The optimal species-informed model showed excellent predictability. • LIME values helped explain species-informed model's surface species content. • Species-informed modeling framework could be applied to other adsorption systems. This study aimed to develop surface complexation modeling-machine learning (SCM-ML) hybrid model for chromate and arsenate adsorption on goethite. The feasibility of two SCM-ML hybrid modeling approaches was investigated. Firstly, we attempted to utilize ML algorithms and establish the parameter model, to link factors influencing the adsorption amount of oxyanions with optimized surface complexation constants. However, the results revealed the optimized chromate or arsenate surface complexation constants might fall into local extrema, making it unable to establish a reasonable mapping relationship between adsorption conditions and surface complexation constants by ML algorithms. In contrast, species-informed models were successfully obtained, by incorporating the surface species information calculated from the unoptimized SCM with the adsorption condition as input features. Compared with the optimized SCM, the species-informed model could make more accurate predictions on pH edges, isotherms, and kinetic data for various input conditions (for chromate: root mean square error (RMSE) on test set = 5.90 %; for arsenate: RMSE on test set = 4.84 %). Furthermore, the utilization of the interpretable formula based on Local Interpretable Model-Agnostic Explanations (LIME) enabled the species-informed model to provide surface species information like SCM. The species-informed SCM-ML hybrid modeling method proposed in this study has great practicality and application potential, and is expected to become a new paradigm in surface adsorption model. [Display omitted] [ABSTRACT FROM AUTHOR]

Fe(III)-alginate (IA) and layered aluminum oxyhydroxide (LAO) assisted hydro ceramsite (HC) composite named HC@LAO-IA was constructed to enhance the removal of Se(IV), Se(VI) and As(V) from high-concentration sulfate wastewater. [Display omitted] • HC@LAO-IA was fabricated by layered aluminum oxyhydroxide, iron(III)-alginate and hydro ceramsite. • HC@LAO-IA showed superior removal of Se(IV), Se(VI) and As(V) under simulated and actual wastewater. • HC@LAO-IA was stable against coexisting ions, particularly excelling in high-concentration sulfate. In this work, hydro ceramsite (HC) was coated by layered aluminum oxyhydroxide (LAO) with the assistance of Iron(III)-alginate (IA) to obtain HC@LAO-IA. Iron(III)-alginate (IA) and layered aluminum oxyhydroxide (LAO) assist in the improvement of the adsorption capacity of hydro ceramsite (HC) for Se(IV), Se(VI), and As(V) via hydrogen bonding, electrostatic adsorption, and inner sphere complexation, respectively. HC@LAO-IA showed superior removal of Se(IV), Se(VI), and As(V) under simulated and actual environmental conditions in the presence of multiple competing anions (Cl−, NO 3 –, CO 3 2–, PO 4 3− and SO 4 2−), particularly excelling in high-concentration sulfate wastewater, and also has a wide pH application range of 3–10. After four reuse cycles, HC@LAO-IA still exhibits satisfactory performance. Sand column experiments also demonstrated that HC@LAO-IA has excellent capabilities for the removal of Se(IV), Se(VI), and As(V) from real wastewater obtained from a metallurgical process plant. This work provides a promising, low-cost approach to remove Se and As from aqueous solutions and a new route for ceramsite recycling. [ABSTRACT FROM AUTHOR]

Toxic metals and Antibiotics appear in water sources have potential threat or adverse effect on health of human being and other living species. The present paper reports a novel micellar-enhanced ultrafiltration process could efficiently remove the toxic metals like arsenate and antibiotics like Levofloxacin and Sulfamethazine from water. Contaminants removal by conventional ultrafiltration membrane is very low. Removal up to 92.8 %, 84.1 % and 95.3 % of Arsenate (AsO43-), Levofloxacin (LF) and Sulfamethazine (SMT) respectively was achieved by micellar-enhanced ultrafiltration with cationic surfactant Benzalkonium chloride as compared to conventional ultrafiltration, which rejected 91.4 %, 8.2 % and 7.9 % of Arsenate, LF, and SMT respectively. Hydrodynamic size of the molecule trapped by micelle enhances significantly helping the separation. The ultrafiltration membrane was modified with copper-chitosan supramolecular assembly and found that molecular weight cut-off decreased because of supramolecular assembly formation. Mechanical properties such as tensile stress and elongation at break were evaluate and it was found that the membrane had significantly higher tensile strength viz. up to 60.9 MPa as compared to virgin Polysulfone membrane 12.7 MPa. Thus, the present work paves the way for future work in the area for removal different contaminants. by micellar-enhanced ultrafiltration. • A novel micellar-enhanced ultrafiltration has been reported along with membrane modification. • Upto 92.8 %, 84.1 % and 95.3 % removal of Arsenate (AsO43−), Levofloxacin (LF) and Sulfamethazine (SMT) respectively • Hydrodynamic size of Levofloxacin increased by micelle formation with cationic surfactant benzalkonium chloride • Membrane modification with Chitosan-Copper supramolecular assembly • Ultimate tensile stress increased with membrane modification [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]

[Display omitted] • A novel sulfate intercalated and self-doping LDHs was derived from the field AMD. • Effects of Mg2+/Fe3+ molar ratios and coexisting ions on the characteristics of LDHs synthesized from AMD were evaluated. • The LDHs exhibit superior capacity for immobilization As(V) under a wide range of pH values. • Anion exchange and complexation play crucial roles in As(V) removal. • The quality of AMD was improved after being utilized as a source of metal and sulfate precursors for the formation of LDHs. A novel approach was investigated for the synthesis of sulfate intercalated iron based layered double hydroxides (LDHs) from field acid mine drainage (AMD) by co-precipitating Fe3+, Mg2+ and SO 4 2− ions. By strategically controlling the Mg2+/Fe3+ molar ratios in AMD, the structural and interfacial properties of LDHs were effectively regulated. Compared to LDHs synthesized from chemical reagents, which had charge density of 3.99 e/nm2 and basal spacing of 0.816 nm, the AMD-synthesized LDHs exhibited higher charge density of 5.34 e/nm2 and larger interlayer d-spacing (0.872 nm) due to the incorporation of co-existing Al3+ and Ca2+ in AMD. The LDHs synthesized from AMD displayed a higher adsorption capacity of 80.16 mg/g and demonstrated strong anti-interference ability, with the removal efficiency of As(V) being maintained at approximately 96% across a pH range of 2.0 to 9.0. The effective capture of arsenate was attributed to the anion exchange of arsenate ions with interlayer sulfate, as well as the strong metalloid binding affinities between the -OH active sites and arsenate. This study revealed that the self-doping LDHs derived from AMD were superior for As(V) removal and the adverse impacts of AMD were alleviated. [ABSTRACT FROM AUTHOR]

Hematite is an iron oxide commonly found in terrestrial environments and plays an essential role in controlling the migration of heavy metal(loid)s in groundwater and sediments. Although defects were shown to exist both in naturally occurring and laboratory-synthesized hematite, their influences on the immobilization of heavy metal(loid)s remain poorly understood. In this study, hematite samples with tunable vacancy defect concentrations were synthesized to evaluate their adsorption capacities for the cation Pb(II) and for the oxyanion As(V). The defects in hematite were characterized using XRD, TEM-EDS mapping, position annihilation lifetime spectroscopy, and XAS. The surface charge characteristics in defective hematite were investigated using zeta potential measurements. We found that Fe vacancies were the primary defect type in the hematite structure. Batch experiments confirmed that Fe vacancies in hematite promoted As(V) adsorption, while they decreased Pb(II) adsorption. The reason for the opposite effects of Fe vacancies on Pb(II) and As(V) immobilization was investigated using DFT calculations and EXAFS analysis. The results revealed that Fe vacancies altered As–Fe coordination from a monodentate to a bidentate complex and increased the length of the Pb–Fe bond on the hematite surface, thereby leading to an increase in As(V) bonding strength, while decreasing Pb(II) adsorption affinity. In addition, the zeta potential analysis demonstrated that the presence of Fe vacancies led to an increase in the isoelectric point (IEP) of hematite samples, which therefore decreased the attraction for the cation Pb(II) and increased the attraction for the oxyanion As(V). The combination of these two effects caused by defects contributed to the contrasting difference between cation Pb(II) and oxyanion As(V) immobilization by defective hematite. Our study therefore provides new insights into the migration and fate of toxic heavy metal(loid)s controlled by iron minerals. [Display omitted] • Hematite with tunable vacancy defects were obtained by ball-milling treatment of well-crystallized hematite. • Fe vacancies were the primary defect type existing in the defective hematite samples. • Increasing Fe vacancy defects led to an increase in oxyanion As(V) adsorption on hematite. • Fe vacancies was detrimental to the immobilization of cation Pb(II) on hematite. • Fe vacancies altered affinity of hematite to As(V) and Pb(II) due to the change of coordination environments. [ABSTRACT FROM AUTHOR]

The adsorption of arsenate and phosphate onto natural or synthetic layered double hydroxides (LDHs) has emerged as a promising solution to minimize the environmental effects of these compounds in soils and waters. In the present work, the adsorption of these oxyanions onto Mg-Fe LDHs in both single-ion and competitive systems was studied through wet chemistry experiments, solid-state analyses, and advanced surface complexation modeling (SCM). The Mg-Fe LDH showed a good efficiency to remove both As and P, being the pH of the system a major driver for the adsorption levels observed. Adsorption results for competitive systems showed a decrease for both oxyanions compared to the single-ion adsorption systems. The adsorption behavior is mechanistically described using two types of SCM, namely the diffusion layer model (DLM) and the charge-distribution multisite complexation model (CD-MUSIC). The later model captures better the influence of pH and ionic strength on the adsorption of arsenate and phosphate onto LDH in both single-ion and multicomponent systems. The best description of the experimental results was obtained when combining two types of surface complexes, namely monodentate inner-sphere complex at lower pH values and monodentate outer-sphere complex at higher pH values. This model approach provides more detailed information about the surface properties of LDHs, which may be beneficial for future studies dealing with LDHs as reactive phases influencing metal(loid) mobility in water or soil systems. [Display omitted] • A higher affinity for phosphate compared to arsenate was observed for LDHs. • A decrease in pH and an increase in As/P concentration led to LDH destabilization. • The CD-MUSIC model adequately describes proton and As/P binding on LDHs. • Inner- and outer-sphere complexes are formed on the LDH surface. • Fe-phosphates/arsenates are formed at higher concentrations and lower pH values. [ABSTRACT FROM AUTHOR]

The coexistence of microplastics (MPs) and arsenic (As) in terrestrial ecosystems presents challenges to controlling soil pollution and performing environmental risk assessments. In this study, the interactions among As, polystyrene MPs, and goethite in porous media were investigated and the individual and combined toxicities of MPs and As on wheat germination were evaluated. An additional experiment was conducted to assess the mitigating effect of goethite on the toxicity of the two contaminants. The results showed that the presence of MPs reduced As accumulation in wheat and decreased the acute lethal toxicity of As pollutants (the half-lethal concentration of As during wheat germination increased by 68.21%). However, MPs exhibited inhibitory effects on wheat germination and served as carriers to promote the migration of As within the plant body. The addition of goethite mitigated both individual and combined toxicities and further increased the half-lethal concentration for the combined pollution of As and MPs by 39.48%. This was primarily attributed to the adsorption and immobilization of arsenate and MPs on the medium and root surfaces. In our study, goethite reduced soluble As by 48.29% under the combined pollution scenarios and formed iron plaques on wheat roots, effectively obstructing pollutant entry. Thus, iron minerals serve as pioneering barriers to combined toxicity. Our findings contribute to the understanding of the combined toxicity of MPs and As in crops and offer potential strategies for managing combined pollution. [Display omitted] • The combined toxicity mechanisms of As and MPs on wheat seed were revealed. • MPs migration in wheat were visualized, quantified, and correlated with As. • Iron plaque acted as a barrier to prevent As and MPs from entering wheat. • Iron minerals could effectively against the combined toxicity of As and MPs. [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]

• 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]

The dynamic interactions among iron (Fe) oxides, organic matter (OM) and heavy metals/metalloids play crucial roles in controlling the geochemical cycling of carbon (C) and heavy metals/metalloids in natural environments. Although the inhibitory effects of arsenate (As(V)) or OM on the ferrihydrite transformation process have been studied previously, there is still a lack of mechanistic and quantitative understanding on the kinetics of As(V) and C sequestration during the Fe(II)-induced ferrihydrite transformation. In this study, we employed a suite of techniques to elucidate the underlying mechanisms accounting for the temporal changes of As(V) and C distributions and speciation on Fe oxides during the Fe(II)-induced ferrihydrite transformation process. Characterizations with X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), and the spherical aberration corrected scanning transmission electron microscopy (Cs-STEM) at different times indicated that the presence of As and/or FA resulted in the formation of more lepidocrocite than goethite. Besides surface adsorption, a portion of As(V) may be incorporated into the lattice structures of newly formed crystalline Fe oxides, and the amount of As(V) sequestration within Fe oxides were correlated with the formation of crystalline Fe oxides. In comparison, FA molecules were either adsorbed on the surfaces of goethite or diffused into the defects or nano pore spaces of lepidocrocite. Our results shed the light on different nanoscale mechanisms accounting for the sequestration of C and As(V) on Fe oxides. The defects or nano pore spaces formed in the structures of lepidocrocite may provide an effective way to sequester C through physical isolation, while the crystal structures of Fe oxides may sequester As(V) through isomorphic substitution. The knowledge on the dynamic coupling between Fe oxide transformation and C/As(V) sequestration provided the basis for accurately predicting the geochemical cycling of trace elements and OM. [ABSTRACT FROM AUTHOR]

Assessment of inorganic arsenate (As(V)) is critical for ensuring a sustainable environment because of its adverse effects on humans and ecosystems. This study is the first to attempt to predict As(V) toxicity to the bioluminescent bacterium Aliivibrio fischeri exposed to varying As(V) dosages and environmental factors (pH and phosphate concentration) using six machine learning (ML)-guided models. The predicted toxicity values were compared with those predicted using the extended biotic ligand model (BLM) we previously developed to evaluate the toxic effect of oxyanion (i.e., As(V)). The relationship between the variables (input features) and toxicity (output) was found to play an important role in the prediction accuracy of each ML-guided model. The results indicated that the extended BLM had the highest prediction accuracy, with a root mean square error (RMSE) of 12.997. However, with an RMSE of 14.361, the multilayer perceptron (MLP) model exhibited quasi-accurate prediction, despite having been trained with a relatively small dataset (n = 256). In view of simplicity, an MLP model is compatible with an extended BLM and does not require expert knowledge for the derivation of specific parameters, such as binding fraction and binding constant values. Furthermore, with the development and employment of reliable in-situ sensing techniques, monitoring data are expected to be augmented faster to provide sufficient training data for the improvement of prediction accuracy which may, thus, allow it to outperform the extended BLM after obtaining sufficient data. [Display omitted] • Environmental factors (pH and phosphate) affect arsenate toxicity. • Arsenate toxicity to Aliivibrio fischeri was predicted using six machine learning. • The multilayer perceptron (MLP) model exhibited quasi-accuracy compared with a BLM. [ABSTRACT FROM AUTHOR]

Assessing the adsorption competition between arsenate (As(V)) and phosphate (P(V)) is crucial due to their coexistence in water. This paper studied the competitive adsorption processes of As(V) and P(V) on magnetic iron-based alginate-chitosan beads by beaker experiments, simultaneously using XRD and FTIR techniques for characterization. In the single system, both As(V) and P(V) adsorption on M-IACBs followed the Langmuir model, with maximum adsorption capacities of 14.2 ± 0.4 mg g−1 and 18.5 ± 0.4 mg g−1, respectively. In the binary system, the competitive adsorption of As(V) and P(V) is a multilevel heterogeneous process well evaluated by the extended Freundlich and pseudo-second-order models. When loaded simultaneously, the adsorption of As(V) was more significant than that of P(V) (2.72 mg g−1 vs. 1.71 mg g−1). The desorption of P(V) was favored over As(V) during sequential loading, and the adsorption of P(V) was more influenced by pH compared to As(V). The adsorption affinity of the composites follows the order: As(V) < P(V) (for the single system) and As(V) > P(V) (for the binary system). Finally, changes in arsenic species were studied under anoxic aqueous solutions and oxygen-enriched air. In aqueous solutions, As(V) is reduced to the more toxic and mobile As(III) by Fe(II), and As(III) exhibits desorption-readsorption behavior. In oxygen-enriched air, As(V) undergoes electron transfer with Fe(II) and O 2 , resulting in the appearance of As(III), which can also be oxidized back to As(V). This study provides an objective and critical evaluation of the data regarding the use of Fe-based adsorbents in removing As(V), offering novel insights for designing such adsorbents. [Display omitted] • The adsorption affinity follows: arsenate < phosphate (single system) and arsenate phosphate > phosphate (binary system). • In anaerobic aqueous solution, As(V) is reduced to t As(III) by Fe (II) and is subject to desorption-readsorption. • In oxygen air, Fe(II) oxidizes, creating vacancies for Fe(II) (Fe(III) and an electron) to move, reducing As(V) to As(III). [ABSTRACT FROM AUTHOR]

Perfluorooctanoic acid (PFOA) is a type of toxic per- and poly-fluoroalkyl substance (PFAS) commonly found in groundwater due to its use in firefighting and industrial applications. The main purpose of this study was to investigate the influence of PFOA shock on the biological performance of a hydrogen-driven bioreactor for nitrate and arsenate removal. Four hydrogen-driven removal reactors (HdBRs) used for the simultaneous removal of nitrate and arsenal were operated with concentrations of either 0, 1, 5, and 10 mg/L of PFOA to induce shock on the systems and examine the corresponding bacterial response. Our results showed that PFOA shock inhibited and decreased the maximum hydrogen-driven arsenate removal rate. Principal Component Analysis (PCA) confirmed that this performance decrease occurred due to a bacterial strike triggered by PFOA shock. PFOA toxicity also led to protein secretion and sludge density decreases. Bacterial analyses showed shifts in the community population due to PFOA shock. The dominant bacteria phylum Proteobacteria became more abundant, from 41.24% originally to 48.29% after exposure to 10 mg/L of PFOA. Other phyla, such as Euryarchaeota and Bacteroidetes, were more tolerant to PFOA shock. Although some of the predominant species within the sludge of each HdBR exhibited a decline, other species with similar functions persisted and assumed the functional responsibilities previously held by the dominant species. [Display omitted] • PFOA possess negative impacts on H 2 -driven biological nitrate and arsenate removal. • PFOA caused significant protein secretion and sludge particle size increases. • PFOA shock led to noticeable microbial population shifts within the HdBRs. • Members of Euryarchaeota and Bacteroidetes phyla could better tolerate PFOA shock. [ABSTRACT FROM AUTHOR]

The controlled removal of hazardous ionizable compounds ranging from organic dyes from the textile industry to inorganic anions such as fluoride, sulfate or arsenate in aqueous media presents challenges to this day. This study devised a synthetic strategy to enable anion selective or simultaneous adsorption of anionic and cationic species. Therefore, versatile ternary metal composites (TMCs) were prepared with variable aluminum salt precursors: TMC-S for Al 2 (SO 4) 3 and TMC-N for Al(NO 3) 3 with variable Al3+ content from high to low values (S1>S2>S3>S4; N1≫N3) for the respective TMCs. Characterization was achieved through complementary methods: pH PZC , TGA, PXRD, XPS, 27Al/13C NMR and IR spectroscopy. The TMC surface properties were assessed via dye adsorption with methylene blue (MB) as a model cation, whereas methyl orange (MO) and reactive Black 5 (RB5) served as model anion systems. Sulfate, fluoride and arsenate represented a variety of inorganic anion target pollutant species. The maximum equilibrium adsorption capacity of MO decreased (TMC-S1 to TMC-S4; 0.67 to 0.41 mmol/g), whereas the MB adsorption capacity increased from 0.03 to 0.47 mmol/g. The arsenate adsorption capacity also decreased with decreased aluminum concentration during synthesis from 0.71 mmol/g (TMC-S1) to 0.46 mmol/g (TMC-S4). Arsenate and fluoride were chemisorbed onto the Al-centers, in contrast to the dye probes, which undergo physisorption. Additionally, arsenate was selectively removed from saline samples of groundwater with up to 6000 mg/L sulfate species, which contributes to salinity without altering the adsorption properties. This study hereby highlights the unique role of variable aluminum salt during synthesis to enable facile tailoring of the adsorbent structure and selective anion adsorption (TMC-S1) versus a more general (less selective) adsorption of ionic species (TMC-S4) for multi-component pollutant removal. [Display omitted] • Versatile ternary biocomposite (alginate + chitosan + Al(III)) adsorbents were prepared. • Variation in aluminium loading enabled switchable contaminant adsorption properties. • Improved adsorption properties toward a range of organic and inorganic anion pollutants. • Biopolymer and metal sites play a cooperative role in the adsorption process. • Remarkably selective arsenate adsorption occurs under highly saline (sulfate) conditions. [ABSTRACT FROM AUTHOR]

Routine monitoring of inorganic arsenic in groundwater using sensitive, reliable, easy-to-use and affordable analytical methods is integral to identifying sources, and delivering appropriate remediation solutions, to the widespread global issue of arsenic pollution. Voltammetry has many advantages over other analytical techniques, but the low electroactivity of arsenic(V) requires the use of either reducing agents or relatively strong acidic conditions, which both complicate the analytical procedures, and require more complex material handling by skilled operators. Here, we present the voltammetric determination of total inorganic arsenic in conditions of near-neutral pH using a new commercially available 25 μm diameter gold microwire (called the Gold Wirebond), which is described here for the first time. The method is based on the addition of low concentrations of permanganate (10 μM MnO 4 −) which fulfils two roles: (1) to ensure that all inorganic arsenic is present as arsenate by chemically oxidising arsenite to arsenate and, (2) to provide a source of manganese allowing the sensitive detection of arsenate by anodic stripping voltammetry at a gold electrode. Tests were carried out in synthetic solutions of various pH (ranging from 4.7 to 9) in presence/absence of chloride. The best response was obtained in 0.25 M chloride-containing acetate buffer resulting in analytical parameters (limit of detection of 0.28 μg L−1 for 10 s deposition time, linear range up to 20 μg L−1 and a sensitivity of 63.5 nA ppb−1. s−1) better than those obtained in acidic conditions. We used this new method to measure arsenic concentrations in contrasting groundwaters: the reducing, arsenite-rich groundwaters of India (West Bengal and Bihar regions) and the oxidising, arsenate-rich groundwaters of Mexico (Guanajuato region). Very good agreement was obtained in all groundwaters with arsenic concentrations measured by inductively coupled plasma-mass spectrometry (slope = +1.029, R2 = 0.99). The voltammetric method is sensitive, faster than other voltammetric techniques for detection of arsenic (typically 10 min per sample including triplicate measurements and 2 standard additions), easier to implement than previous methods (no acidic conditions, no chemical reduction required, reproducible sensor, can be used by non-voltammetric experts) and could enable cheaper groundwater surveying campaigns with in-the-field analysis for quick data reporting, even in remote communities. [Display omitted] • Novel methodology for detection of inorganic arsenic at various pH. • Arsenic analysis in reduced groundwaters of West Bengal and oxidised groundwater of Central Mexico. • Comparison study between voltammetric determination in acidic conditions vs. near-neutral pH. • Validation study between voltammetric methods with inductively coupled plasma mass spectrometry (ICP-MS). • Scanning electron microscope image of gold microwire surface. [ABSTRACT FROM AUTHOR]

Researchers worldwide have extensively studied metal organic framework (MOF) for its adsorption capabilities. Despite its potential, challenges such as particle agglomeration, low porosity and low surface area persist. This study aims to enhance the performance of MIL-100(Fe) for As(V) adsorption using a feasible and straightforward technique. To achieve this, benzoic acid was introduced as a modulator for ligand exchange, creating vacancy defects within the MIL-100(Fe) structure, resulting in defective MIL-100(Fe)-BA1. Through TEM imaging, visible deformations were observed on the surface of the adsorbent, with an average particle size of approximately 200 nm. XRD spectrum analysis revealed a reduction in peak intensity at 2–5°, indicating reduced crystallinity in the MIL-100(Fe) due to the presence of defects. Meanwhile, BET analysis demonstrated a significantly larger surface area for defective MIL-100(Fe) at 1081.09 m2/g, compared to the pristine MIL-100(Fe) with a surface area of 844.00 m2/g. Regarding adsorptive performance, the defective MIL-100(Fe) exhibited higher As(V) adsorption capacity (173.82 mg/g at pH8) than the pristine form (70 mg/g). This improvement can be attributed to the larger pore size of the particles and the exceptional affinity of As(V) anions towards the bulk Lewis Acid sites present on the surface of defective MIL-100(Fe). However, it is important to note that for effective As(V) adsorption by defective MIL-100(Fe)-BA1, it is crucial to eliminate competing compounds such as carbonate and phosphate anions from the water sources. Addressing these challenges will further enhance the efficacy of the adsorption process [Display omitted] • Benzoic acid can induce defect within MIL-100(Fe) and develop more cavities. • Surface area of defective MIL-100(Fe) is 30.82% higher than pristine MIL-100(Fe). • Defective MIL-100(Fe) achieves 173.82 mg/g As (V) adsorption at pH 8. • Defective MIL-100(Fe) retains 72% of its adsorption capacity after regeneration. [ABSTRACT FROM AUTHOR]

Only limited information is available on the effects of dissolved organic phosphorus (DOP) on arsenate (As (V)) bioaccumulation and biotransformation in organisms. In this study, we examined the influence of three different DOP forms (β-sodium glycerophosphate (βP), adenosine 5′-triphosphate (ATP), and D-Glucose-6-phosphate disodium (GP) salts) and inorganic phosphate (IP) on As (V) toxicity, accumulation, and biotransformation in Microcystis aeruginosa. Results showed that M. aeruginosa utilized the three DOP forms to sustain its growth. At a subcellular level, the higher phosphorus (P) distribution in metal-sensitive fractions (MSF) observed in the IP treatments could explain the comparatively lower toxic stress of algae compared to the DOP treatments. Meanwhile, the higher MSF distribution of arsenic (As) in M. aeruginosa in the presence of DOP could explain the higher toxicity with lower 96-h half maximal effective concentration (EC 50) values. Although we observed As (V) and P discrimination in M. aeruginosa under IP treatments with high intracellular P/ As , we did not find this discrimination under the DOP treatments. As accumulation in algal cells was therefore greatly enhanced by DOP, especially βP, given its lower transformation rate to phosphate compared to ATP and GP in media. Additionally, As (V) reduction and, subsequently, As (III) methylation were greatly facilitated in M. aeruginosa by the presence of DOP, particularly GP, which was confirmed by the higher relative expression of its two functional genes (arsC and arsM). Our findings indicate that As (V) accumulation and its subsequent biotransformation were enhanced by organic P forms, which provides new insight into how DOP modulates As metabolism in algae. Image 1 • M. aeruginosa could utilize the three DOP to sustain its growth. • As(V) and P aren't discriminated by M. aeruginosa under DOP conditions. • Arsenic accumulation were enhanced under DOP conditions especially βP. • As (V) reduction and subsequent methylation was facilitated by DOP, particularly GP. • Higher MSF of As can explain higher toxicity on algae under DOP conditions. [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]

• Natural tuff (T), 0.6–1.9 mm fraction, was coated with magnetite (MMT). • Batch data proved MMT 5 times more efficient in removal of phosphates/arsenates. • Fixed-bed column data confirmed MMT superior in adsorption than T. • MMT filtration ability was unchanged, capacity for PO 4 3−/As(V) removal developed. Natural filtration material tuff (T) was modified by coating with nano-sized magnetite. The grain fraction of 0.6–1.9 mm was submitted to hydrothermal synthesis of magnetite. Thus formed magnetite modified tuff (MMT) was characterized in terms of Fe-content, N2 adsorption- desorption isotherm, SEM, zeta potential-pH analyses and adsorption behavior towards phosphates/arsenates in batch and column conditions. Elemental analysis showed that 36.54 mg g−1 of magnetite was attached to the porous tuff grains. This modification changed pore structure and specific surface area. An increase of cca 35% in Sp value was obtained. Batch experiments proved that MMT was 4-5 times more efficient in removal of phosphates/arsenates than non-modified T. The maximum sorption capacities of phosphates calculated based on Langmuir equation were 0.45 and 1.91 mg g−1, while those for arsenate were 0.551 m g−1 and 2.36 mg g−1 for T and MMT, respectively. The intra-particle diffusion model was the most suited for describing the adsorption process of phosphate and arsenate onto MMT. Fixed-bed column data corroborated batch results, i.e. MMT was 6 times superior in contaminant adsorption than T. Modification with magnetite improved T potential for usage in water treatment applications: its filtration ability remained unchanged, while adsorption capacity for phosphates/arsenates removal was improved. [ABSTRACT FROM AUTHOR]

Algae accumulate and metabolize arsenic (As) and facilitate cycling and speciation of As in seawater. The laboratory-controlled macroalgal cultures were exposed to different molar ratios of As(V) and phosphate (P) in seawater for evaluating the uptake and metabolism of As, as a function of As(V) detoxification through biotransformation. Chlorophyll fluorescence of algal species was not significantly affected by the culture conditions (p > 0.05). Addition of 10 μM P positively reduce As stress, but different As(V)/P ratios significantly affect the growth rate (p < 0.05). Algae readily accumulated As(V) after the inoculation, transformed intracellularly, and released gradually into the medium along the incubation period, depending on As(V)/P molar ratios. Reduction and methylation were the leading processes of As(V) metabolism by Pyropia yezoensis , whereas Sargassum patens showed only the reduction. Sargassum horneri reduced As(V) under low level (0.1 μM), but both reduction and methylation were observed under a high level (1 μM). At the end of incubation, 0.17, 0.15, 0.1 μM of reduced metabolite (As[III]) were recorded from 1 μM of As(V)/P containing cultures of Sargassum horneri , Sargassum patens , and Pyropia yezoensis , respectively. On the other hand, 0.024 and 0.28 μM of methylated metabolite (DMAA[V]) were detected under the same culture conditions from Sargassum horneri and Pyropia yezoensis , respectively. The results also indicated that P in medium inhibits the intracellular uptake of As(V) and subsequent extrusion of biotransformed metabolites into the medium. These findings can help to understand the metabolic diversity of macroalgae species on As biogeochemistry in the marine environment. Image 1 • Chlorophyll fluorescence of algae unchanged up to 7 d under As(V) stress. • Sargassum horneri and Pyropia yezoensis reduce and methylate As(V). • Detoxification of As(V) by Sargassum patens coupled with only reduction. • Low levels of P enhance cellular uptake of As(V) and excretion process. • Fe-plaque leads to adsorb As and P on the surface of algae. [ABSTRACT FROM AUTHOR]

The removals of arsenic and selenium pollutants are always urgent desires for the water security. In this study, both sorption and catalysis strategies were combined for the effective removals of As(V) and Se(VI) over magnetic graphene oxide sheets (GOs)-oxidized carbon nanotubes (OCNTs) hydrogels. The sorption behavior facilitated the operation of catalysis reactions, meanwhile, the catalytic reduction promoted the release of occupied sorption sites and then restarted a new sorption-catalysis cycle. The synergic effect of sorption and catalysis realized 258.2 mg g−1 for As(V) enrichment capacity on MPG2T1, and ultra-fast sorption and catalysis equilibriums were identified within 9 min. In the case of Se(VI), a moderate enrichment performance was observed to be 46.2 mg g−1. Similarly, the ultra-fast sorption and reduction of Se(VI) were realized within 2 min. In the competition experiments, only SO 4 2−, SO 3 2−, and HPO 4 2− showed interference for As(V) and Se(VI) removals. These results testified the superiority of the synergy effect of sorption and catalysis, and the feasibility of 3D magnetic GOs-OCNTs hydrogel in practical implementations. The effective removals of As(V) and Se(VI) were realized on the 3D GOs-OCNTs hydrogel based on ultra-fast sorption and catalysis behaviors within a few minutes. Image 1 • The synergistic effects of sorption and catalysis demonstrated the effective removals of As(V) and Se(VI). • Ultra-fast sorption was realized within 9 min for As(V) removal, and 2 min for Se(VI), respectively. • Effective catalysis was achieved within 2 min for the reductions of As(V) and Se(VI). [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]

• Mesoporous Zirconia Nanostructures (MZN) were synthesized via hydrothermal method. • As(III) and As(V) removal capacities of the MZN were 105 and 110 mg/g, at pH 7. • The MZN demonstrated good anti-interference ability to common co-existing ions. • The MZN showed excellent treatment of simulated real arsenic contaminated water. • Adsorption mechanism involved electrostatic interaction and surface complexation. Mesoporous zirconia nanostructures (MZN) were synthesized by hydrothermal method to efficiently remove highly mobile and toxic arsenite (As(III)) and arsenate (As(V)) from aqueous solutions. The as-synthesized MZN were characterized by Brunauer–Emmett–Teller (BET), X-Ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscope (HRTEM), and Energy-dispersive X-ray spectroscopy (EDX) techniques. The batch adsorption experimental results showed that the As(III) and As(V) removal capacities of the MZN were 105.03 and 110.29 mg/g, respectively, under neutral pH conditions, which were better than many recently reported adsorbents. The adsorption behavior of As(III) and As(V) on the MZN could be well described by pseudo-second-order and Langmuir isotherms models. Moreover, As(III) and As(V) adsorption on the MZN was spontaneous and endothermic. Some of the common co-existing ions had slightly affected the arsenic removal proficiency of MZN. Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to investigate the adsorption mechanism of As(III) and As(V) on the as-synthesized MZN. The as-synthesized MZN demonstrated quite fast and good treatment of simulated real arsenic (As(III,V)) contaminated water. This study suggested that the as-synthesized MZN are potential candidate for practical applications of As(III) and As(V) removal from the aqueous solutions. [ABSTRACT FROM AUTHOR]

As a problematic element in water systems, arsenic exists as As(III) and As(V). Adsorption techniques can be used to remove anionic As(V) as it is present as a polyatomic anion. In the case of As(III) which exists in zero-valent state under neutral pH, it can be also removed by adsorption after being converted into As(V). Many inorganic and organic materials have been examined as potential adsorbents for anionic As(V) removal. However, most exhibit relatively low adsorption capacities (<10 mg/g). The objective of this study is to examine As(V)-removal mechanism and practical potential of a PEI-coated bacterial biosorbent prepared from fermentation biowaste. The maximum As(V) uptake of the biosorbent was determined to be 62.99 mg/g by Langmuir model. The effects of various parameters including pH, biosorbent dosage, ionic strength and temperature were also examined. Kinetic and equilibrium models were used to interpret the experimental data mathematically. A 0.01 M NaOH solution was chosen as an effective As(V)-desorbing eluent for biosorbent regeneration. The adsorption capacity of the biosorbent remained above 85% over three successive cycles of adsorption and desorption. In conclusion, the biowaste-driven biosorbent is a promising anion adsorbent for treatment of As(V)-contaminated wasters. • Anion biosorbent prepared from fermentation biowaste was used for As(V) removal. • The biosorbent had 62.99 mg/g of As(V) uptake, which were higher than others. • Solution pH was the most important parameter which affected As(V) removal. • 0.01 M NaOH solution was chosen as As(V)-desorbing eluant. [ABSTRACT FROM AUTHOR]

Abstract In this study, amorphous Mn oxides (AMOs) and their composites with biochar (BC) were synthesized using different sugars (glucose, sucrose, and molasses), and their sorption efficiency toward Zn(II), Cd(II), and As(V) was tested. Additionally, detailed characterization of synthesized materials using various solid-state analysis methods (e.g. XRD, FTIR-ATR, and/or SEM-EDX) was also performed. Despite glucose-based AMOs presented higher sorption efficiency for As(V), i.e., 0.73 mmol g−1 (glucose) > 0.27 mmol g−1 (sucrose and molasses), similar sorption efficiency toward Zn(II), i.e., 0.80 mmol g−1 (glucose and molasses) > 0.66 (sucrose) and Cd(II) (0.71–0.74 mmol g−1 (sucrose and molasses) > 0.36 mmol g−1 (glucose), was observed for sucrose- and molasses-based AMOs under the given conditions. Next, the sorption efficiency of all AMO/BC composites was proportional to their AMO content. Finally, Mn(II) leaching from the structure of the new AMOs was negligible compared to that observed for the glucose-based AMOs, in this study as well as in other similar studies. Moreover, using molasses as reducing agent during AMO synthesis dramatically decreased the total cost of the final materials, which suggested that these new AMOs could represent interesting alternatives for standard remediation technologies. The AMOs synthesized using low-cost sugars could, therefore, be promising materials for real field applications, since the main disadvantages of using standard AMOs are mitigated. Nevertheless, the efficiency and stability of these composites under real-life conditions must be tested prior to their direct application for remediation technologies. Graphical abstract Unlabelled Image Highlights • Amorphous Mn oxides were synthesized using low-cost sugars. • Composites of amorphous Mn oxides and biochar were prepared. • All materials effectively removed Zn(II), Cd(II), and As(V) from aqueous solutions. • Amorphous Mn oxides synthesized from sucrose and molasses were highly stable. • Mn As precipitates were detected on the material surface at high As(V) loadings. [ABSTRACT FROM AUTHOR]

Abstract A new arsenate, NaH 2 AsO 4 ·(C 12 H 8 N 2)·1.5H 2 O (1) is discussed with respect to its molecular structure derived by single-crystal X-ray diffraction, Hirshfeld surface analysis, and DFT calculations of electronic as well as spectral properties. The arsenate is synthesized from reacting Na 2 HAsO 4 ·7H 2 O with 1,10-phenantroline. The structure of compound 1 crystallizes in the monoclinic crystal system with C 2/ c space group and unit cell parameters: a = 20.4402(17) Å, b = 6.7392(3) Å, c = 20.3528(17) Å, β = 96.007(4)°. The study of intermolecular interactions using Hirshfeld surfaces analysis has confirmed that the hydrogen bonding interactions play the dominating role in the stability of the compound. The analysis of electronic structure allowed classifying this compound among the semiconductors. The study of the reactivity using molecular modelling confirms the good electrophilic and nucleophilic reactivity. Calculated energies and thermodynamic functions for the compound revealed significant evolution with temperature. An important evolution of potential energy, kinetic energy and the total energy of 1 was confirmed by the molecular dynamics simulation. Graphical abstract Image 1 Highlights • Synthesis of new arsenate, Na 2 (H 2 O) 3 (C 12 H 8 N 2) 2 [H 2 AsO 4 ] 2. • Crystal structure study of the new compound. • Theoretical study of the interactions of Na 2 (H 2 O) 3 (C 12 H 8 N 2) 2 [H 2 AsO 4 ] 2. • Electronic properties and Reactivity studies of the compound. • Thermodynamic properties and Molecular dynamics studies of the compound. [ABSTRACT FROM AUTHOR]

Among natural organic matter (NOM), oxyanions and metal (hydr)oxides, a complicated interaction exists in natural aquatic and terrestrial systems and in waste waters. Effects of seven types of NOM (four humic acids (HA), three fulvic acids (FA)) that vary in properties on the adsorption of oxyanions, including phosphate, arsenate and arsenite, at goethite-water interface were quantitatively studied. Results show that the adsorption of oxyanions to goethite is decreased by the presence of NOM, especially for phosphate and arsenate at low pH. In general, the effects of the three FA are similar, which are more effective than HA in reducing oxyanion adsorption at low pH (<6). Differences were observed between the four HA in their competition with oxyanions. The adsorption of phosphate, arsenate and arsenite in the presence of NOM are well described with both the NOM-CD (CD: Charge Distribution) and LCD (Ligand and Charge Distribution) model. The NOM-CD model is relatively simple to use, whereas the LCD model can better reveal different factors in the interaction, including the spatial distribution of adsorbed NOM on oxide surface. According to these two models: site density of carboxylic groups, protonation constant of carboxylic groups, and particle size of NOM are major properties of NOM determining its effect on oxyanion adsorption to oxides. At relatively low loadings, morphological change of adsorbed NOM takes place, and the degree of morphological change of adsorbed NOM depends on the particle size, site density of carboxylic groups and aromaticity of NOM. The influence of particle size on the interaction becomes more important at higher NOM loadings. The results suggested that the fixation or removal efficiency of phosphate, arsenate and arsenite with iron oxides (e.g. goethite) can be significantly decreased by the presence of NOM, especially when NOM rich in acidic and aromatic groups. Image 1 • Properties of NOM affecting oxyanion adsorption are identified. • Two advanced models, i.e. NOM-CD and LCD model are compared for the first time. • NOM decreases phosphate and arsenate adsorption especially under acidic pH. • Site density of carboxylic groups on NOM strongly affects oxyanion adsorption. • Particle size becomes more important at higher NOM loading on oxides. [ABSTRACT FROM AUTHOR]

Highlights • A gas-diffusion flow analysis method for As(V) in drinking water was developed. • As(V) is preconcentrated by on-line separation using a polymer inclusion membrane. • The membrane consists of PVDF-HFP as base polymer and Aliquat 336 as extractant. • The method offers a limit of detection of 3 μg L−1. • As(V) was successfully determined in drinking water samples. Abstract The sequential application of a polymer inclusion membrane (PIM), composed of poly(vinylidenefluoride-co-hexafluoropropylene) and the anionic extractant Aliquat 336, and a microporous polytetrafluoroethylene (PTFE) gas-permeable membrane was utilized for the first time to develop a flow analysis (FA) system, for the automatic determination of trace levels of arsenate (As(V)) in drinking water as arsine. The system incorporated a flow-through extraction cell for separation and preconcentration of arsenate and a gas-diffusion cell for the separation of arsine prior to its spectrophotometric determination based on the discoloration of a potassium permanganate solution. Under optimal conditions the FA system is characterized by a limit of detection of 3.0 μg L−1 As(V) and repeatability of 1.8% (n = 5, 25 μg L−1 As(V)) and 2.8% (n = 5, 50 μg L−1 As(V)). The newly developed FA method was successfully applied to the determination of arsenate in drinking water samples in the μg L−1 concentration range. [ABSTRACT FROM AUTHOR]

p -Arsanilic acid (p -ASA) and roxarsone (ROX) are two major phenylarsenic feed additives that are still widely used in many countries, and the land application of animal waste containing these compounds could introduce large quantities of arsenic into the environment. In this study, we proposed a treatment scheme for animal waste that involves leaching of p -ASA/ROX out of the manure first by water, then oxidation by ferrate (Fe(VI)) and removal of the arsenate released by in situ formed Fe(III) oxide-hydroxide. The effects of solution pH, dosage of Fe(VI), solution ionic strength, and matrix species on the treatment performance were systematically evaluated. Initial solution pH values of 4.1 and 2.0 were chosen for the oxidation of p -ASA and ROX, respectively, while efficient arsenate removal could be achieved with relatively small adjustment of the final solution pH (to 4.0). The pH-dependent second-order rate constants for the reactions between ferrate and p -ASA and ROX over the pH range of 2.0–12.0 were estimated to be 7.13 × 105–2.01 × 10−1 and 8.91 × 103–1.65 × 10−1 M−1 s−1, respectively. The degradation pathways of p -ASA/ROX during ferrate oxidation were proposed based on the inorganic and organic intermediates identified. Depending on the levels of p -ASA/ROX, effective treatment could be achieved through flexible adjustment of the Fe(VI) dosage. p -ASA/ROX (10 mg-As/L) in swine manure leachate could be efficiently treated by ferrate oxidation within 5 min, with the overall arsenic removal efficiency higher than 99.2%. The treatment performance was barely affected by the presence of common ions (K+, Ca2+, Na+, Mg2+, SO 4 2−, NO 3 −, and Cl−), while humic acid, Mn2+, Ni2+, Fe3+, and Co2+ inhibited p -ASA/ROX oxidation. The presence of PO 4 3− and NH 4 + could accelerate the oxidation of p -ASA/ROX, but PO 4 3− and humic acid compromised sorptive removal of the released arsenate due to their competitive sorption on the Fe(III) oxide-hydroxide precipitate. Ferrate oxidation is green and fast, and the operation is simple, thus it could serve as a promising and environment-friendly option for mitigating the risk of phenylarsenic feed additives in animal waste. Unlabelled Image • A simple method for treating p-ASA and ROX using ferrate (VI) was developed. • Kinetics and mechanism of p-ASA and ROX oxidation by ferrate (VI) were elucidated. • Arsenate released was removed through sorption onto the in situ formed FeO(OH). • The oxidation process took <5 min, and the total arsenic removal efficiency was >99%. • Ferrate treatment is a faster and more convenient alternative to Fenton process. [ABSTRACT FROM AUTHOR]

Abstract To obtain a cost-effective adsorbent for the removal of arsenic in water, a novel nanostructured Fe–Co based metal organic framework (MOF-74) adsorbent was successfully prepared via a simple solvothermal method. The adsorption experiments showed that the optimal molar ratio of Fe/Co in the adsorbent was 2:1. The Fe 2 Co 1 MOF-74 was characterized by various techniques and the results showed that the nanoparticle diameter ranged from 60 to 80 nm and the specific surface area was 147.82 m2/g. The isotherm and kinetic parameters of arsenic removal on Fe 2 Co 1 MOF-74 were well-fitted by the Langmuir and pseudo-second-order models. The maximum adsorption capacities toward As(III) and As(V) were 266.52 and 292.29 mg/g, respectively. The presence of sulfate, carbonate and humic acid had no obvious effect on arsenic adsorption. However, coexisting phosphate significantly hindered the removal of arsenic, especially at high concentrations (10 mmol/L). Electrostatic interaction and hydroxyl and metal–oxygen groups played important roles in the adsorption of arsenic. Furthermore, the prepared adsorbent had stable adsorption ability after regeneration and when used in a real-water matrix. The excellent adsorption performance of Fe 2 Co 1 MOF-74 material makes it a potentially promising adsorbent for the removal of arsenic. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

• Isolated pure population of mouse cranial neural crest cells (CNCCs). • Studied the effects of in utero exposure to sodium arsenate on CNCCs. • Reported arsenate-induced alterations in the expression of novel candidate genes. • Identified novel signaling pathways potentially impacted by arsenate exposure. • Identified novel genes & canonical cascades that may contribute to arsenate-induced orofacial defects. Prenatal exposure to arsenic, a naturally occurring toxic element, causes neural tube defects (NTDs) and, in animal models, orofacial anomalies. Since aberrant development or migration of cranial neural crest cells (CNCCs) can also cause similar anomalies within developing embryos, we examined the effects of in utero exposure to sodium arsenate on gene expression patterns in pure populations of CNCCs, isolated by fluorescence activated cell sorting (FACS), from Cre/LoxP reporter mice. Changes in gene expression were analyzed using Affymetrix GeneChip® microarrays and expression of selected genes was verified by TaqMan quantitative real-time PCR. We report, for the first time, arsenate-induced alterations in the expression of a number of novel candidate genes and canonical cascades that may contribute to the pathogenesis of orofacial defects. Ingenuity Pathway and NIH-DAVID analyses revealed cellular response pathways, biological themes, and potential upstream regulators, that may underlie altered fetal programming of arsenate exposed CNCCs. [ABSTRACT FROM AUTHOR]

Abstract Much attention has focused on the mutual effect of oxyanions and cations on surfaces, however, there is still a lack of knowledge on the molecular-level surface precipitation mechanisms for As(V) and Cd(II) on surfaces under different pH conditions in acid metallurgical industrial wastewater. The results of in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and extended X-ray absorption fine structure (EXAFS) spectroscopy show that different As(V) and Cd(II) surface precipitation mechanisms take effect at pH 5.0 and 7.0. Under acidic conditions, As(V) was preferentially adsorbed on TiO 2 rather than Cd(II). Thus, a Cd(II)-As(V)-TiO 2 ternary surface complex was formed with the adsorbed As(V) as the bridging molecule, and the subsequent layer-by-layer surface precipitate was generated. Under neutral conditions, the Cd(II)-As(V) surface precipitates were directly formed by using the aqueous Cd(II)-As(V) complex as a "seed", which took approximately 10 times longer than the acidic conditions to reach the adsorption equilibrium. Our findings provide spectroscopic evidence and elucidate the different simultaneous removal mechanisms of As(V) and Cd(II) on TiO 2 under acidic and neutral conditions, which will further our understanding and application of the immobilization of multiple pollutants in industrial wastewaters. Graphical abstract Unlabelled Image Highlights • Different As(V) and Cd(II) surface precipitation mechanisms took effect under acidic and neutral environments. • The As(V) bridging layer-by-layer surface precipitate was formed at pH 5. • Surface precipitates were directly formed by using the aqueous Cd As complex at pH 7. [ABSTRACT FROM AUTHOR]