Hydrogen Arsenate Research Articles

Adsorption of ions onto high silica volcanic glass

Chemical fingerprint techniques are frequently applied to airborne volcanic eruption products, so-called tephra, such as ash and pumice for archeological and geoscientific purposes. However, in some cases, a meaningful interpretation of the results is complicated by superficial contaminations. Therefore, this situation was simulated by the use of powdered rhyolitic pumice to investigate its capability to adsorb several ions from aqueous solutions. Using neutron activation analysis, adsorption could be proven for Cr 3+, Cr 2O 7 2− (dichromate), Fe 3+, Co 2+, HAsO 4 2− (hydrogen arsenate), Rb +, Sr 2+, Cs +, Ba 2+, La 3+, Ce 3+, Ce 4+, Sm 3+, Th 4+ and UO 2 2+, which is a clear evidence for the interaction of those ions with the volcanic glass. In our experiments, pumice powder showed the ability to adsorb ions in the range from 1.8 mg kg −1 (in case of HAsO 4 2−) to 5.8 wt% (in case of Fe 3+). Adsorption is probably due to ion-exchange reactions. It could also be shown that a few ions are not adsorbed in detectable quantities: Na +, K +, Fe 2+, Zn 2+ and Nd 3+. The knowledge about adsorption of ions enables us not only to examine the possible influence of contaminations where chemical fingerprinting methods are applied to volcanic material for archaeometry, but it also suggests the technical application of pumiceous materials for technical purposes, like water purification or as an adsorbent in the final storage of nuclear waste. In another series of INAA supported experiments, the influence of chemicals like ascorbic acid, acetic acid, HCl, HF, HNO 3, H 2O, H 2O 2, H 3PO 4, H 2SO 4, NaOH and NH 3 on the bulk composition of pumice powder was investigated—resulting in no detectable change. We conclude that superficially contaminated tephra can be washed in diluted HF to remove contaminations without influencing the chemical fingerprint.

CsAl(H2AsO4)2(HAsO4): A New Monoclinic Protonated Arsenate with Decorated Kroehnkite‐Like Chains.

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CsAl(H2AsO4)2(HAsO4): a new monoclinic protonated arsenate with decorated kröhnkite-like chains

The crystal structure of hydrothermally synthesized caesium aluminium bis[dihydrogen arsenate(V)] hydrogen arsenate(V), CsAl(H(2)AsO(4))(2)(HAsO(4)), was determined from single-crystal X-ray diffraction data collected at room temperature. The compound represents a new structure type that is characterized by decorated kröhnkite-like [100] chains of corner-sharing AlO(6) octahedra and AsO(4) tetrahedra. Ten-coordinated Cs atoms are situated between the chains, which are interconnected by five different hydrogen bonds [O...O = 2.569 (4)-2.978 (4) A]. All atoms are in general positions. CsAl(H(2)AsO(4))(2)(HAsO(4)) is very closely related to CsGa(H(1.5)AsO(4))(2)(H(2)AsO(4)) and isotypic CsCr(H(1.5)AsO(4))(2)(H(2)AsO(4)).

Speciation and Removal of Arsenic in column packed with chitosan

The arsenic speciation and arsenic removal in chitosan packed column were studied. Arsenic removal experiments were carried out with an arsenic standard solution (1.0 mg/l) and drilled well water samples from Limon Mine Community at different pH, water flowrate, and volume of adsorbent material. The simulation of arsenic speciation was carried out at a pH range from 0 to 12, a temperature of 25ºC, a pE equal to 4, and a total arsenic concentration of 1.34 x 10-5 mol kg-1. According to speciation calculations arsenic is found mainly in oxidized form in the conditions of Limon Mine’s drilled well waters, dihydrogen arsenate ion (H2AsO4-), and hydrogen arsenate ion (HAsO42-) being the major species. The experiments showed that arsenic adsorption depends mainly on the pH as well as the activity of functional groups that compose the chitosan structure. At pH 3 and volume of adsorbent material of 337.8 cm3 an adsorption of 94% was obtained from arsenic standard solution, and the arsenic present in the Limon Community’s water was almost totally removed at pH 3 and 7. The use of the results for designing purposes demands the breakthrough curves for chitosan to be determined.

Fragmentation of the DNA Repair Enzyme, OGG1, in Mouse Nonparenchymal Liver Cells by Arsenic Compounds

Our previous work demonstrated that arsenic compounds increased 8-hydroxyguanine (8-OH-Gua) in the DNA of cultured human cells (A549) and reduced the endonuclease nicking activity for 8-OH-Gua, suggesting that arsenic compound-induced carcinogenesis was the consequence of the inhibition of DNA repair. However, the exact mechanism by which the repair systems were disturbed was unknown. To elucidate the mechanism, we analyzed mouse 8-oxoguanine DNA glycosylase 1 (mOGG1) expression in mouse nonparenchymal liver cells, NCTC, treated with arsenic compounds (arsenic trioxide, sodium arsenite, and sodium hydrogen arsenate). We detected a cleaved form of mOGG1 (35 kDa) in addition to normal mOGG1 (type 1a, 38 kDa) in NCTC treated with arsenic compounds. These results are similar to our previous results which showed that fragmentation of mOGG1 by etoposide was related to caspase-dependent apoptosis, and was accompanied by increased 8-OH-Gua accumulation. Taken together, our results suggested that arsenic compounds might increase 8-OH-Gua accumulation by inhibiting 8-OH-Gua repair, due to mOGG1 cleavage.

Octahedral—Tetrahedral Framework Structures of InAsO4×H2O and PbIn(AsO4)(AsO3OH).

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CsGa(H1.5AsO4)2(H2AsO4) and isotypic CsCr(H1.5AsO4)2(H2AsO4): decorated kröhnkite-like chains in two unusual hydrogen arsenates

Hydrothermally synthesized caesium gallium(III) hydrogen arsenate(V), CsGa(H1.5AsO4)2(H2AsO4), (I), and isotypic caesium chromium(III) hydrogen arsenate(V), CsCr(H1.5AsO4)2(H2AsO4), (II), represent a new structure type and stoichiometry among MI-MIII hydrogen arsenates. The crystal structure, determined from single-crystal X-ray diffraction data, is based on an infinite octahedral-tetrahedral chain and can be described as a decorated kröhnkite-like chain. The chains extend parallel to [100] and are separated by ten-coordinated Cs atoms. The hydrogen-bonding scheme comprises one very short symmetry-restricted hydrogen bond, with O...O distances of 2.519 (4) and 2.508 (4) A in (I) and (II), respectively, and two further medium-strong hydrogen bonds, all of which reinforce the connections between adjacent chains. The average Ga-O and Cr-O bond lengths are 1.973 (15) and 1.980 (13) A, respectively, and the average As-O bond lengths in the two protonated arsenate groups lie within a very narrow range [1.690 (18)-1.69 (3) A]. The Cs atom is located on a centre of inversion, while the MIII and As2 atoms lie on twofold axes. Relationships to CaBa2(HPO4)2(H2PO4)2 and other compounds containing decorated kröhnkite-type or kröhnkite-like chains are discussed.

Octahedral–tetrahedral framework structures of InAsO4·H2O and PbIn(AsO4)(AsO3OH)

Indium arsenate(V) monohydrate, InAsO4.H2O, (I), crystallizes in the structure type of MnMoO4.H2O. The structure is built of In2O8(H2O)2 dimers (mean In-O=2.150 A) corner-linked to slightly distorted AsO4 tetrahedra (mean As-O=1.686 A). The linkage results in a three-dimensional framework, with small voids into which the apical water ligand of the InO5(H2O) octahedron points. The hydrogen bonds in (I) are of medium strength. Lead(II) indium arsenate(V) hydrogen arsenate(V), PbIn(AsO4)(AsO3OH), (II), represents the first reported lead indium arsenate. It is characterized by a framework structure of InO6 octahedra corner-linked to AsO4 and AsO3OH tetrahedra. The resulting voids are occupied by Pb2O10(OH)2 dimers built of two edge-sharing highly distorted PbO6(OH) polyhedra (mean Pb-O=2.623 A). The compound is isotypic with PbFe(III)(AsO4)(AsO3OH). The average In-O bond length in (II) is 2.157 A. In both arsenates, all atoms are in general positions.

Solubility and stability of barium arsenate and barium hydrogen arsenate at 25 °C

The inconsistency among current thermodynamic data of Ba 3(AsO 4) 2(c) and BaHAsO 4·H 2O(c) led the authors to obtain independent solubility data of barium arsenate by both precipitation and dissolution experiments. Low and neutral pH (3.63–7.43) favored the formation of BaHAsO 4·H 2O(c). Both BaHAsO 4·H 2O(c) and Ba 3(AsO 4) 2(c) formed at the neutral pH conditions (7.47, 7.66), whereas Ba 3(AsO 4) 2(c) was the only solid phase precipitated at high pH (13.03, 13.10). The Ba 3(AsO 4) 2(c) precipitate acquired at 50 °C appeared as small leafy crystal, while the Ba 3(AsO 4) 2(c) solid precipitated at 25 °C comprised granular aggregate with some smaller crystal clusters. XRD and SEM analyses of Ba 3(AsO 4) 2(c) and BaHAsO 4·H 2O(c) indicated that the solids were indistinguishable before and after the dissolution experiments. In the present work, the solubility products ( K sp) for Ba 3(AsO 4) 2(c) and BaHAsO 4·H 2O(c) were determined to be 10 −23.53(10 −23.01 to 10 −24.00) and 10 −5.60(10 −5.23 to 10 −5.89), respectively. Δ G f ° for Ba 3(AsO 4) 2(c) and BaHAsO 4·H 2O(c) were calculated to be −3113.40 and −1544.47 kJ/mol, respectively. There was no difference between the solubility products of the leafy and the granular Ba 3(AsO 4) 2(c) solids.

Catena-Poly[[oxo(1,10-phenanthroline)vanadium(IV)]-di-μ-hydrogenphosphato

The crystal structure of [VO(HPO4)(C12H8N2)]n consists of a bis­(vanadyl hydrogen phosphate) skeleton that assumes a linear ribbon conformation; the nitro­gen heterocycles that chelate to the VIV atoms are connected to the sides of the flat ribbon. The compound is isostructural with the hydrogen arsenate, whose structure has been reported by Hou et al. [Inorg. Chem. Commun. (2004). 7, 128–130]. The asymmetric unit, with the exception of one O atom, lies on a mirror plane

A facile soft template synthesis and characterization of PbHAsO 4 nanocrystals

Monoclinic lead hydrogen arsenate (LHA) nanocrystals with different crystallization morphologies and crystallite sizes were prepared successfully by a soft template synthesis method in the presence of sodium dodecylbenzenesulfonate (SDBS) or polyvinylpyrrolidone (PVP). The products were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The possible mechanism of SDBS and PVP in the experiment was briefly illustrated.

Alkali scandium arsenates. II. The framework structures of alpha- and beta-CsSc(HAsO4)2.

The crystal structures of hydrothermally synthesized alpha-, (I), and beta-caesium scandium bis[hydrogen arsenate(V)], (II), both CsSc(HAsO4)2, have been determined from single-crystal X-ray diffraction data collected at room temperature. The dimorphs are both characterized by a three-dimensional negatively charged framework of corner-sharing alternating ScO6 octahedra and HAsO4 tetrahedra. The charge-balancing Cs+ cations are located in a system of three intersecting tunnels in (I) and in tunnels parallel to the a axis in (II). Strong to weak hydrogen bonds reinforce both frameworks. The average Sc-O bond lengths are 2.098 and 2.094 A, respectively. Compound (I) is triclinic and isotypic with (NH4)Fe(III)(HPO4)2, alpha-A(I)V(III)(HPO4)2 (A is NH4 or Rb) and alpha-(NH4)(Al(0.64)Ga(0.36))(HPO4)2. Compound (II) is monoclinic and isotypic with (H3O)Fe(III)(HPO4)2, beta-A(I)V(III)(HPO4)2 (A is NH4 or Rb), CsIn(HPO4)2 and RbSc(HPO4)2. Both (I) and (II) represent the first arsenate examples of their structure types. The Cs and Sc atoms in (I) lie on inversion centres. In (II), all atoms are in general positions. A brief overview is presented of the six structure types shown by A(I)M(III)(HXO4)2 compounds (X is P or As).

Alkali scandium arsenates. I. The framework structures of KSc(HAsO4)2 and RbScAs2O7.

The crystal structures of hydrothermally synthesized potassium scandium hydrogen arsenate(V), KSc(HAsO4)2, (I), and rubidium scandium diarsenate(V), RbScAs2O7, (II), were determined from single-crystal X-ray diffraction data collected at room temperature. Compound (I) represents a new microporous structure type, designated MCV-3, which is characterized by a three-dimensional framework of corner-sharing alternating ScO6 octahedra and HAsO4 tetrahedra. Intersecting tunnels parallel to [101] and [110] host eight-coordinate K atoms. There is one hydrogen bond of medium strength [O...O = 2.7153 (18) A]. Compound (II) is the first reported diarsenate with a KAlP2O7-type structure and is isotypic with at least 27 A(I)M(III) diphosphates. The average Sc-O bond lengths in (I) and (II) are 2.09 (2) and 2.09 (3) A, respectively. The K and Sc atoms in (I) lie on an inversion centre and a twofold axis, respectively. All atoms in (II) are in general positions.

Arsenic Uptake by Native Fern Species in Thailand: Effect of Chelating Agents on Hyperaccumulation of Arsenic by Pityrogramma calomelanos

Nineteen native fern species collected from an area in Thailand with high arsenic concentration in soil and in ground water as a result of tin mining was screened for elevated arsenic concentration in fronds. Two species of fern were found to contain elevated arsenic in their fronds in nature: Pityrogramma calomelanos (108–1156 µg g−1 dried weight) and Pteris vittata (79 µg g−1 dried weight). Under hydroponic culture Pityrogramma calomelanos (a silver back fern) accumulated arsenic in its shoot at rate of 4616 µg g−1 (dried weight). The accumulation of arsenic in Pityrogramma calomelanos shoot doubled with the addition of an EDTA (Ethelenediamine tetraacetic acid) chelating agent. The highest accumulation occurred 6 weeks after exposure to 10 mg L−1 arsenic as disodium hydrogen arsenate. The addition of another chelating agent, DMSA (Dimercaptosuccinic acid), resulted in a 5-fold decrease in arsenic concentration in the Pityrogramma calomelanos shoot compared to control after 6 weeks of exposure to arsenic. The contrasting effect of the EDTA and DMSA chelating agent was attributed to the strong binding of the thiol group to arsenic ion. This study indicated that Pityrogramma calomelanos uptake and translocate arsenic in the form of arsenate and arsenite rather than the As–DMSA complex. Using phytoextraction efficiency calculations, it was determined that Pityrogramma calomelanos gave the highest arsenic phytoextraction efficiency at 6 weeks after exposure to arsenic in the EDTA treatment, with an efficiency of 77.8 mg As based on whole plant biomass.

Arsenic toxicity and HSP70 expression in Xenopus laevis embryos.

The evaluation of the effect of trace metals on health can be difficult, because of their presence in the environment in various chemical forms. Exposure to arsenic compounds is an example of this complexity, as it can be present in the environment in inorganic and organic forms. The effects of arsenic in vertebrates are complicated by several variables, such as speciation of the element, the exposure route, and the susceptibility of the particular animal species. The embryotoxicity and teratogenicity of three arsenic species - sodium arsenite (NaAsO(2)), disodium hydrogen arsenate (Na(2)HAsO(4)) and dimethylarsinic acid [(CH3)2AsOOH] - were evaluated by the modified frog embryo teratogenic assay on Xenopus (FETAX). We also show how the classical FETAX endpoints, based on morphological and morphometrical analysis, can conveniently be integrated with the study of molecular markers. Possible changes in the expression of the mRNA for the heat-shock protein HSP70, following exposure to NaAsO(2), were examined by using the reverse transcriptase polymerase chain reaction. HSP70 mRNA is strongly induced by arsenic.

Refinement of two different crystal structures simultaneously from a multiple-crystal sample: neutron study of 3-deazauracil and lead hydrogen arsenate at 100 K

The structures of 3-deazauracil and lead hydrogen arsenate have been studied by neutron single crystal diffraction at 100K, using a sample containing one crystal of each material. The experiment on the composite sample was entirely routine, using recently developed multiple-crystal techniques. The structures themselves represent the best low temperature neutron determinations on each of these materials and are discussed.

Layered zincoarsenate templated by N,N,N',N'-tetramethylethylenediamine molecules

The title compound, N,N,N′,N′-tetra­methyl­ethyl­enedi­ammon­ium di­aqua­(arsenate)­(hydrogen arsenate)­dizinc(II), (C6H18N2)0.5[Zn2(AsO4)(HAsO4)(H2O)2], is a new zincoarsenate obtained by hydro­thermal synthesis. The structure consists of infinite two-dimensional anionic layers alternating with planes containing centrosymmetric organic diprotonated template N,N,N′,N′-tetra­methyl­ethyl­enedi­ammonium cations, [H3N­C6H12NH3]2+. The latter are interconnected to the framework through hydrogen bonds.

Stability of Metal-Arsenic Solids in Drinking Water Systems

The solubility of arsenic solids is of importance in public health, water treatment, and geochemistry. This work focuses on copper-arsenic and barium-arsenic solids. Experiments were conducted at conditions typical of water distribution systems (e.g., pH ∼ 7, T = 20°C, μ ∼ 10−2.8 M, and typical elemental concentrations). The solubility product for barium hydrogen arsenate (BaHAsO4) was verified by both precipitation and dissolution experiments as a log Ksp value of −5.51 ± 0.02, consistent with literature values. Evidence collected in systems with copper were not consistent with a single arsenic containing solid. Instead data appeared to favor sorption mechanisms with removed arsenic:copper ratios at 0.3:1. The results allow for improved predictability of arsenic behavior in manmade and natural systems.

Hydrogen-atom ordering in a single crystal of PbHASO4monitored at 2 K intervals

The ordering of the H atom in a single crystal of lead hydrogen arsenate has been monitored at 2 K steps in the temperature range 280 to 210 K. Single frames of data were collected using the neutron time-of-flight Laue method, with data-collection times of less than 10 min. The results from these limited data sets are shown to be of value in describing the ordering trend in the structure.

Hydrogen-Atom Ordering in Lead Hydrogen Arsenate Monitored by Neutron Time-of-Flight Laue Diffraction using Single-Frame Methods

The ordering of the hydrogen atom in a single crystal of lead hydrogen arsenate in the temperature range 320 to 80 K is described. The details of the ordering at small temperature steps are determined from single frames of data collected using the neutron time-of-flight Laue method. The constrained refinements obtained from these data yield lower precision than full data sets but allow the ordering to be characterized rapidly and reliably. This is the first example of the use of this single-frame method of monitoring such phase transitions. The approach used here with neutrons, stimulated in part by synchrotron Laue diffraction, will be of interest for all time-resolved experiments with synchrotron radiation or neutrons.