Combined Effect of Fluoride and Arsenate on Gene Expression of Osteoclast Differentiation Factor and Osteoprotegerin

Objective To study the combined effect of fluoride and arsenate on the expression of SD rat osteoblastic osteoclast differentiation factor （ODF） mRNA and osteoprotegerin （OPG） mRNA. Methods Osteoblasts were obtained by enzymatic isolation from newborn SD rats. A factorial experiment was performed. Osteoblasts were exposed to NaF （0.5 mmolF/L, 4 molF/L） and Na3AsH2 （12.5 μmolAs/L and 200 μmolAs/L） separately or F plus As and cultured for 48 h. The gene expression of osteoblastic ODF and OPG was observed by RT-PCR. Results The expression ofODF mRNA increased in F0.5, F4 groups compared with control group and two groups of F0.As200, F,As200 compared with As200 group, and decreased significantly in groups of F4As12.5, F0.5As200, and F4As200. The expression of OPG rnRNA decreased in groups of F4, As200, F4As12.5, F0.5As200, and F4As200. Conclusion The joint effect of fluoride and arsenate on the gene expression of ODF is antagonistic, while the combined effect on the gene expression of OPG is synergistic. F4, F4As12.5, and F0.5As200 promote bone resorption of rat osteoclasts, whereas F0.5As12.5 inhibits osteolytic effect of rat osteoclasts.

Competitive and cooperative adsorption of arsenate and citrate on goethite

The fate of arsenic in natural environments is influenced by adsorption onto metal （hydr）oxides. The extent of arsenic adsorption is strongly affected by coexisting dissolved natural organic acids. Recently, some studies reported that there existed competitive adsorption between arsenate and citrate on goethite. Humic acid is known to interact strongly with arsenate by forming complexes in aqueous solution, hence it is necessary to undertake a comprehensive study of the adsorption of arsenate/citrate onto goethite in the presence of one another. The results showed that at the arsenate concentrations used in this study （0.006-0.27 mmol/L）, citrate decreased arsenate adsorption at acidic pH but no effect was observed at alkaline pH. In comparison, citrate adsorption was inhibited at acidic pH, but enhanced at alkaline pH by arsenate. This was probably due to the formation of complex between arsenate and citrate like the case of arsenate with humic acid. These results implied that the mechanism of the adsorption of arsenate and citrate onto goethite in the presence of one another involved not only competition for binding sites, but the cooperation between the two species at the watergoethite interface as well.

Stabilization of ferric arsenate sludge with mechanochemically prepared FeS2/Fe composites

FeS2/Fe composites were mechanochemically prepared with iron powder and pyrite for the stabilization of ferrite arsenate sludge(FAS).The effects of preparation parameters on stabilization performance were investigated.The results show that the optimum conditions are FeS2/Fe molar ratio of 5:5,milling time of 2 h,ball-to-material mass ratio of 15:1 and milling with stainless steel ball.Then,the composites were characterized by XRD,SEM,FTIR,etc.The physicochemical properties of FeS2/Fe mixture change dramatically,which is responsible for its excellent performance.Finally,the stabilization process of FAS was optimized.When the FAS is mixed with composites at mass ratio of 4:1 and milled for 30 min,the As leaching concentration of FAS can be reduced from 639.15 to 4.74 mg/L with the stabilization ratio of 99.2%.

Interaction mechanism between arsenate and fayalite-type copper slag at high temperatures

The interaction mechanism between sodium arsenate and fayalite-type copper slag at 1200℃was investigated through XRD,XPS,HRTEM,TCLP and other technical means and methods.The results indicated that the proportions of sodium arsenate in the slag and flue gas phases were approximately 30%and 70%,respectively.The addition of sodium arsenate depolymerized the fayalite structure and changed it from a crystalline state to an amorphous state.The fayalite structural changes indicated that the[AsO_(4)]tetrahedron in sodium arsenate combined with the[SiO_(4)]tetrahedron and[FeO_(4)]tetrahedron through bridging oxygen to form a silicate glass structure.The TCLP test results of the samples before and after the high temperature reaction of fayalite and sodium arsenate showed that after high temperature reaction,fayalite could effectively reduce the leaching toxicity of sodium arsenate,reducing the leaching concentration of arsenic from 3025.52 to 12.8 mg/L before and after reaction,respectively.

Oxidation Characteristics of the Reactivity Between Pyrite and Aqueous Arsenate

Natural pyrites contain high levels of adsorbed and structurally incorporated arsenic(As),which may simultaneously result in the release of As and affect the oxidation process of pyrite.However,the oxidation and electrochemical behaviors of As on the oxidation reactivity of pyrites are still not clear.In this study,pyrite was prepared by a hydrothermal method and applied to study the oxidation mechanism between pyrite and aqueous arsenate.Analyses of X-ray diffraction,X-ray photoelectron spectroscopy,and scanning electron microscopy demonstrate that the as-prepared sample is an octahedron-like pyrite with high purity and crystallinity.The interaction between As(V)and pyrite as well as the electrochemical behaviors of pyrite oxidation in the presence of aqueous arsenate were investigated under acidic conditions by an ion analysis method,cyclic voltammetry(CV),Tafel,and electrochemical impedance spectroscopy(EIS).The results of the chemical reaction indicate that electrons are transferred from S 22-to dissolved oxygen with the formation of SO 42-in the initial As(V)concentration range of 0–0.3 mmol/L.In the initial As(V)concentration range of 0.4–1.2 mmol/L,electrons are transferred from S 22-to As(V)with the formation of elemental S 0 and As(III).The CV,the Tafel plot and EIS analyses indicate that aqueous arsenate in an electrolyte promotes oxidation reactivity and passivation of the pyrite electrode.Moreover,the electron transfer rate increases with increasing aqueous arsenate concentration in the electrolyte.

Synthesis and characterization of arsenate antimonic acid AAAc(1 : 1)

The AAAc(1 : 1) was synthesized in water by As2O3 and Sb2O3 with molar ratio of 1 : 1: AAAc(1 : 1)was characterized by Raman, IR, TG/DTG, DSC, XPS and XRD. The results show that there are four peaks to vsof As-OH, As-O-Sb, Sb-OH and Sb-O-Sb in Raman spectra of AAAc(1 : 1) at 100 - 1 000 cm-1. The solution of AAAc(1 : 1) was also titrated with KOH solution. The titration results show that AAAc(1 : 1) is a hexabasic acid with dissociation constants of k1 = 3.62 × 10-2 , k2 = 3.05 × 10-3 , k3 = 6. 43 × 10-6 , k4 = 9. 78 × 10-8 ,k5 = 1.32 × 10-11 , k6 =3.87 × 10-12. AAAc(1 : 1) has a good solubility and stability in water, its solid obtained by free volatilizing water from its solution under air at ambient temperature is amorphous. Chemical and thermal analyture of AsO ( OH )2-OH-Sb ( OH )4-O-Sb ( OH )4-OH-AsO ( OH )2 or As ( OH )3-O-Sb(OH)4-O-Sb(OH)4-O-As(OH)3 (isomerism) through experimental determination and geometry optimization.

Sorption Kinetic of Arsenate as Water Contaminant on Zero Valent Iron

This study investigates the sorption of arsenate from water using zero-valent iron ZVI as sorbent. Batch experiments were carried out to study the sorption kinetics of arsenate under different concentrations of arsenate varies from 0.5 to 200 mg/l. A kinetic model was considered to describe the arsenates sorption on ZVI material. The kinetics of the arsenate sorption processes were described by the Langmuir kinetic model. The sorption capacity increases with high initial concentration which obtained the maximum sorption 2.1 mg/g at 200 mg/l of arsenate initial concentration. The results show that the rapid initial sorption rates of arsenate were occurred at the beginning of experiments running time, followed by a slower removal that gradually approaches an equilibrium condition. The data from laboratory batch experiments were used to verify the simulation results of the kinetic model resulting in good agreement between measured and modeled results. The results indicate that ZVI could be employed as sorbent materials to enhance the sorption processes and increase the removal rate of arsenate from water.

Adsorption removal of roxarsone, arsenite(Ⅲ),and arsenate(Ⅴ) using iron-modified sorghum straw biochar and its kinetics

Arsenic(As)contamination in groundwater is a major problem in many countries,which causes serious health issues.In this paper,a novel method has been developed for the simultaneous removal of ROX and As(Ⅲ/Ⅴ)using the modified sorghum straw biochar(MSSB).The MSSB was characterized by X-ray diffraction,scanning electron microscopy,Fourier Transform Infrared,and Brunauer–Emmet–Teller(BET)surface area.The removal performance of MSSB for ROX,arsenite[As(Ⅲ)],and arsenate(As(Ⅴ))was investigated using batch experiments.At pH of 5,the arsenic concentration of 1.0 mg/L,adsorbent dose of 1.0 g/L,the maximum adsorptioncapacities of ROX,As(Ⅲ),and As(Ⅴ)were 12.4,5.3,and 23.0 mg/g,respectively.The adsorption behaviors were fit well with the Langmuir and the pseudo-second-order rate model.The results showed that MSSB acted as a highly effective adsorbent to simultaneously remove the composite pollution system consisted of ROX and As(Ⅲ/Ⅴ)in aqueous solutions,providing a promising method in environmental restoration applications.

Arsenate Removal by Iron-Modified Ion Exchange Fiber

The adsorption characteristics of arsenate on ion exchange fiber(IEF) and iron-modified ion exchange fiber(FeIEF) were evaluated.Batch adsorption experiments were conducted to study the arsenate adsorption effect by varying contact time,pH,and coexisting anions.Adsorption capacity was found to increase by increasing the contact time and acidic conditions were favorable for arsenate adsorption on IEF and Fe-IEF.Arsenate adsorption data were better consistent with Freundlich equation than Langmuir equation.The maximum monolayer adsorption capacities were 285 and 333 mg/g at 25℃ for IEF and Fe-IEF respectively.The adsorption kinetics was found to follow the pseudo-first-order kinetic model.The existence of HCO 3-,PO34-,SO24-,SiO23-,and NO 3-decreased the arsenate adsorption capacity on IEF.Cl-and F-had little influence on it.When FeIEF was adopted,the effects of HCO 3-,SO24-,Cl-,SiO23-,and NO 3-were negligible,while PO43-could still markedly decrease the adsorption capacity and F-had inhibitory effect on arsenate adsorption.Fe-IEF can be used as a highly selective and efficient sorbent for removal of arsenate from aqueous solutions.

Hydrothermal Synthesis and Structure of One New Vanadoarsenate [Zn(dien)(Hdien)]_2[As_6V_(15)O_(42)(H_2O)]·4H_2O

One new arsenic-vanadium cluster, [Zn（dien）（Hdien）]2[As6V15O42（H2O）]·4H2O （1, dien = diethylenetriamine）, has been hydrothermally synthesized and characterized by IR, elemental analysis, TGA, magnetic property and single-crystal X-ray diffraction analysis. Crystal data for 1： monoclinic, space group P21/n, a = 13.959（3）, b = 22.428（5）, c = 22.831（5） A^°, β = 90.733（4）°, Z = 4. X-ray crystallographic study showed that compound 1 is constructed from [As6V15O42（H2O）]^6- polyoxoanions linked together by novel [Zn（dien）（Hdien）]^3＋ complex fragments via hydrogen bonds into a three-dimensional network. Variable temperature susceptibility measurement demonstrates the presence of antiferromagnetic interaction between V^IV cations in 1.

Hydrothermal Syntheses, Structure Characteristics and Magnetic Properties of a Series of New Molybdenum Arsenates Based on {(As3O3)2(Mo6O18)(MO6)}(M = Ni, (1); Co, (2); Zn, (3))

Three new polyoxometalates K2[H2（As3O3）2（Mo6O18）（NiO6）]？H2O （1）, K2[H2-（As3O3）2（Mo6O18）（CoO6）]？H2O （2） and [Zn（H4,4？-bpy）2（H2O）4][（As3O3）2（Mo6O18）（ZnO6）]？4H2O （3） （4,4？-bpy = 4,4？-bipyridine） have been synthesized under hydrothermal conditions and characterized by IR, elemental analyses, XPS and single-crystal X-ray diffraction analyses, respectively. Compound 1 represents a new 3D framework structure constructed from polyoxoanion [（As3O3）2（Mo6O18）（NiO6）]4- via covalent bond. Compound 2 has an identical structure with 1. Compound 3 represents a new 2D layer structure constructed from transition metal coordination cations [Zn（H4,4？-bipy）2（H2O）4]4＋, lattice water molecules and polyoxoanions [（As3O3）2- （Mo6O18）（ZnO6）]4- via multi-point N–H？？？O and O–H？？？O hydrogen bonding interactions. Crystal data： for 1, cubic, space group Pa-3, a = 15.0022（8） ？, V = 3376.5（3） ？3, Z = 24; for 2, cubic space group Pa-3, a = 15.1596（10）, V = 3483.88 ？3, Z = 24; for 3, monoclinic, space group C2/m, a = 19.699（4）, b = 14.223（3）, c = 9.1455（18） ？, β = 106.80（3）o, V = 2453.0（9） ？3, Z = 8. In addition, the magnetic behaviors for compounds 1 and 2 have been investigated.

Preliminary Study of the Characteristics and Genesis of Arsenate Minerals in the Oxidized Zone of the Debao Skarn-Type Cu-Sn Ore Deposit in Guangxi

Through the study of the oxidized zone of the Debao skarn-type Cu-Sn deposit in Guangxi, the authorshave found 14 arsenate minerals, most of which are for the first time reported in China. They are mainly Cuarsenate minerals with subordinate Cu-Pb arsenate minerals and minor Fe-Pb-Ba varieties. Based on their paragenesis these minerals may be divided into the following series: (1) the clinoclasite-olivenite-cornwallite- cornubite- debaoite- copper silicarsenate association, (2) the scorodite- carminite- beudan-tite-bayldonite- duftite association, and (3) the scorodite-Ba-bearing pharmacosiderite- dussertite association. Arsenate minerals are formed generally in the oxidized zone of the sulfide-type deposits which lie in thewarm, humid and rainy torrid-subtropical zone with pH=6-8 and contain large amounts of arsenopyrite andcarbonate rocks.

Kinetics of Desolvation of the Glycation of Hemoglobin Catalyzed by Buffer Phosphate and Arsenate

The glycation of hemoglobin is catalyzed by buffer phosphate and arsenate. The catalytic constant （kB） for aqueous arsenate is two-fold larger than for aqueous phosphate. The catalytic constant （ks） of phosphate in sorbitol mixtures increase from （1.67 ± 0.11） × 10-10 s-1·M-1 to （5.78 ± 0.39） × 10-10 s-1·M-1 and the catalytic constant is enhanced 3.5 times, relative to that in water; the catalytic constant （kB） of arsenate in sorbitol mixtures increase from （2.98±0.07）× 10-10 s-1·M-1 to （6.62 ± 0.53） × 10-10 s-1·M-1 and the catalytic constant is enhanced 2 times, relative to that in water. The spontaneous rate constants are independent of sorbitol concentration for phosphate and arsenate. The catalytic power of phosphate and arsenate in sorbitol are the same. Desolvation of strongly hydrated species such as HPO42 and HAsO42 should make a contribution to the energy cost of the formation of anion-hemoglobin complexes and can be a possible explanation for higher catalytic potential of HAsO42 in water. The same catalytic constant （ksB） for phosphate and arsenate in sorbitol indicates that the same catalyst base group on the hemoglobin molecule may be involved in the abstraction of proton in the Amadori rearrangement.

Indirect photocatalytic reduction of arsenate to arsenite in aqueous solution with TiO_2 in the presence of hole scavengers

The indirect photocatalytic reduction of arsenate to arsenite in aqueous solution with titanium dioxide(TiO_2)was investigated with various hole scavengers such as methanol, ethanol, 2-propanol, formaldehyde, acetone,formic acid and acetic acid. Although the direct photocatalytic reduction of arsenate to arsenite with TiO_2 was impossible, an indirect reduction of As(V) was possible in the presence of sacrificial electron donors to form strongly reductive radicals. The addition of ethanol was very effective for indirect photocatalytic reduction of As(V) in aqueous solution with TiO_2 photocatalyst. The indirect photocatalytic reduction rate of As(V) may be related with both the reaction rate constants of reaction of hydroxyl radicals with hole scavenger and the reactivities for the radicals M· which are produced by the reaction of ·OH with hole scavenger.

An Exploratory Analysis of the Market Perspective on Reclaiming Chromated Copper Arsenate (CCA) from Decommissioned Preservative-Treated Wood Utility Poles

In the area of recycling of spent chromated copper arsenate (CCA)-treated wood, most studies to date have focused on methods of removing/extracting the residual preservative from the wood matrix. It is well recognized that exposure of CCA-treated wood to an acid solution can reverse the CCA fixation process thereby converting the CCA elements into their water-soluble form. The economic viability of the process is enhanced because it can be integrated with other technologies and products (e.g., “green” spray foam insulation, etc.). The market for the “green” CCA is the same as for traditional CCA-the wood treating industry, principally utility poles and pilings. A market research study was conducted to determine the suitability of spent CCA-treated wood as a source for recycled, “green” CCA for manufacturing “green” spray-foam insulation. Specifically, we wanted to discern the attitudes and overall perspectives of buyers/sellers (i.e., utilities and wood treating companies) of CCA preservatives and treated wood products, disposal methods and costs for decommissioned CCA-treated wood, and understand perceptions of and willingness-to-pay for “green” CCA preservatives extracted from the technologies used in this research. Results show that 60% of wood preservative treating respondents and 60% of electric utility company respondents are somewhat or greatly interested in using out-of-service utility poles as feedstock for “green insulation” as part of a new potential business venture.

Phylogenetic analysis and arsenate reduction effect of the arsenic-reducing bacteria enriched from contaminated soils at an abandoned smelter site

Microbial reduction of As(V)(i.e.,arsenate)plays an important role in arsenic(As)mobilization in aqueous environment.In this study,we investigated As(V)reduction characteristics of the bacteria enriched from the arsenic-contaminated soil at an abandoned smelter site.It was found that As(V)was completely reduced to As(III)(i.e.,arsenite)in 21 h.After 3-d incubation,a yellow solid was precipitated and the concentration of As(III)decreased sharply.After 150 h incubation,ca.65%of soluble arsenic was removed fro...

Arsenic Distribution,Species,and Its Effect on Maize Growth Treated with Arsenate

A pot experiment was conducted to investigate the effect of different arsenic （As） levels on maize （Zea mays L.） growth and As accumulation and species in different parts of maize plants,as a guideline for production of maize in As-polluted areas with the objective of preventing As from entering the food chain,and improving understanding of the mechanisms of effect of As on plant.Zhengdan 958 was grown at five As levels added to soil （0,12.5,25,50,and 100 mg kg^-1 As）.As concentration in maize tissues increased in the order of grain〈stalk〈leaf〈〈root.The As concentration in maize grain exceeded the maximum permissible concentration of 0.7 mg kg^-1 in China at levels of 50 and 100 mg kg^-1.As species were presented in root,stalk,and grain,but organic As was the major As species identified in the grain.Maize plants were able to reduce arsenate to arsenite.Low As levels of 12.5 and 25 mg kg^-1 improved maize growth and grain nutrition quality,while high levels of As 50 or 100 mg kg^-1 inhibited them.Yield reduction at high As levels resulted mainly from reduced ear length,kernel number per row,and kernel weight.

A new mixed-valent iron arsenate black crystal

Scorodite（FeAsO4·2H2O）is the most popular phase for arsenic（As）immobilization while the reductive dissolution of Fe（Ⅲ）to Fe（Ⅱ）will promote As release.In the present study,an equilibrium between Fe（Ⅲ）and Fe（Ⅱ）was achieved in scorodite preparation system by introducing certain alcohol（methanol,ethanol,isopropanol or tert-butanol）,and thus a new mixed-valent iron arsenate black crystal formulated as Fe（Ⅱ）（5.2）Fe（Ⅲ）（8.8）（HAsO4）4（AsO4）8·H2O was prepared.In comparison with scorodite,the black crystal has higher As content（36.4%,mass fraction）and lower crystal water content（0.73%,mass fraction）.Additionally,the leaching concentration of As can be lower than the threshold value（5 mg/L）regulated by identification standards for hazardous wastes of China（GB 5080.3-2007）.Therefore,this new mixed-valent iron arsenate crystal could be classified as a non-hazardous and promising As-bearing phase in environmental applications.

Arsenate and phosphate interaction in Saccharomyces cerevisiae

In the present study, arsenate（As（V）） and phosphate（P（V）） interactions were investigated in growth, uptake and RNA content in yeast（Saccharomyces cerevisiae）. Yeast grew slowly with As（V） concentrations increasing in the medium. However, the maximal population density was almost the same among different As（V） treatments. It was in the late log phase that yeast growth was aug- mented by low As（V）, which was maybe due to the fact that methionine metabolism was stressed by vitamin B6 deprivation, so As（V） treatments did not affect maximal population density. However, with P （V） concentrations increasing, the maximal population density increased. Therefore, the maximal population density was determined by P （V） concentrations in the medium but not by As （V） concentrations in the medium. Ycflp（a tonoplast transpor） transports As（GS）3 into the vacuole, but arsenic（As） remaining in the thalli was 1.27% with As（V） exposure for 60 h, from which it can be speculated that the percentage of As transported into vacuole should be lower than 1.27%. However, the percentage of As pumped out of cell was 71.49% with As （V） exposure for 68 h. Although two pathways （extrusion and sequestration） were involved in As detoxification in yeast, the extrusion pathway played a major role in As detoxification. RNA content was the highest in the early-log phase and was reduced by As（V）.

Influence of Arsenate and Phosphate on the Regulation of Growth and TCA Cycle in the Rice (<i>Oryza sativa</i>L.) Cultivars IR64 and Nayanmani

The influence of arsenate and phosphate on the growth and respiration of 21 days old seedlings in two cultivars of rice, viz., IR64 and Nayanmani was studied. As arsenate and phosphate are similar in their chemical configuration and the latter is preferentially taken up by the phosphate transporters, it results in a competitive inhibition of arsenate uptake in presence of phosphate. Increasing concentrations of sodium arsenate (25 μM, 50 μM and 100 μM) hindered the growth in both the cultivars, with cv. IR64 being more severely affected than cv. Nayanmani. There was an elevation in the levels of organic acids measured in both the cultivars, accompanied by a reduction in the activities of the dehydrogenases of the TCA cycle, viz., pyruvate dehydrogenase, isocitrate dehydrogenase, succinate dehydrogenase and malate dedrogenase under arsenic treatment alone. Also, an elevation in the activities of citrate synthase and fumarase enzymes was noticed in both test seedlings with increasing concentrations of arsenic. These alterations were more prominent in cv. IR64 than in cv. Nayanmani. On joint application of phosphate along with arsenate, amelioration of the toxic effects of arsenate was observed to some extent, resulting in an overall revival of respiration leading to improved growth and metabolism.