Bioremediation of arsenic contamination from the environment: New approach to sustainable resource management

Present acceleration of Arsenic [As] exposure leads to severe health problems. Modern scientific approaches look towards potent bio-agents for the removal of such types of contaminations in sustainable ways. Microbes can potentially change the redox potential, solubility, pH by different complex reactions during bioremediation. There are many enzymes present in the microbial system which are involved in methylation such as As (V) reductase, monomethyl arsonic acid reductase, As (III) methyltransferase, and MMA (III) methyltransferase. On the other hand, microbes have As transformation ability and changed into different extractable forms with sulfide minerals such as arsenopyrite (FeAsS), enargite (Cu3AsS4) and realgar (As4S4). In some bacteria, the As-operon machinery thiol group bind with As, itdetoxifies its toxicity. Ars R gene and arsenic reductase enzyme (Ars C) play the key role in the reduction of As (V) to As (III) and detoxify by being transported outside of the cell by Ars AB As chemiosmotic efflux system. In fungi, As (V) is reduced to As (III) by the arsenate reductase and GSH glutathione converted into GSSH glutathione disulfide. In plants, As (III) conjugates with phytochelatin (PC) or GSH glutathione and accumulates in the vacuole or is converted into less toxic forms in the presence of arsenic reductase enzyme. This review focused on the potentiality and mechanisms of different microbes for As-detoxification in a sustainable manner.

One Functionalized Polyoxovanadates Hybrid Material Based on Arsonic Acid with Highly Effective Catalytic Property of Sulfides

In this work, a novel 4-aminophenylarsonic acid functionalized polyoxovanadates (POVs) hybrid material, namely, (Me2NH2)4 ·[(L)8(H12V16O32)] (H2L = 4-NH2C6H4AsO3H2) POVs 1 was solvothermally synthesized and fully characterized. The results revealed POVs 1 consists of four similar tetranuclear vanadium clusters bridged by eight organic 4-aminophenylarsonic acid ligands. Remarkably, functionalized hybrid POVs 1 was further investigated as a heterogeneous stable catalyst in oxidation of sulfide derivatives, and exhibited high catalytic activities (yields up to 96.7%). Additionally, the functionalized hybrid polyoxovanadates catalyst can be reused without losing activities after three runs cycle.

Proton-transfer compounds featuring the unusual 4-arsonoanilinium cation from the reaction of (4-aminophenyl)arsonic acid with strong organic acids

The crystal structures of the 1:1 proton-transfer compounds of (4-aminophenyl)arsonic acid (p-arsanilic acid) with the strong organic acids, 2,4,6-trinitrophenol (picric acid), 3,5-dinitrosalicylic acid, (3-carboxy-4-hydroxy)benzenesulfonic acid (5-sulfosalicylic acid) and toluene-4-sulfonic acid have been determined at 200 K and their hydrogen–bonding patterns examined. The compounds are, respectively, anhydrous 4-arsonoanilinium 2,4,6-trinitrophenolate (1), the hydrate 4-arsonoanilinium 2-carboxy-4,6-dinitrophenolate monohydrate (2), the hydrate 4-arsonoanilinium (3-carboxy-4-hydroxy)benzenesulfonate monohydrate (3) and the partial solvate 4-arsonoanilinium toluene-4-sulfonate 0.8 hydrate (4). The asymmetric unit of2, a phenolate, comprises two independent but conformationally similar cation-anion pairs and two water molecules of solvation, and in all compounds, extensive inter-species hydrogen–bonding interactions involving arsono O–H···O and anilinium N–H···O hydrogen–bonds generate three-dimensional supramolecular structures. In the cases of1and2, the acceptors include phenolate and nitro O-atom acceptors, with3and4, additionally, sulfonate O-atom acceptors, and with the hydrates2–4, the water molecules of solvation. A feature of the hydrogen–bonding in3is the presence of primary chains extending along (010) through centrosymmetric cyclicR22(8) motifs together with conjoined cyclicR34(12) motifs, which include the water molecule of solvation. The primary hydrogen–bonding in the substructure of4involves homomolecular cation–cation arsono O–H···O interactions forming columns down the crystallographic four-fold axis of the unit cell.

Unusual 4-arsonoanilinium cationic species in the hydrochloride salt of (4-aminophenyl)arsonic acid and formed in the reaction of the acid with copper(II) sulfate, copper(II) chloride and cadmium chloride

Structures having the unusual protonated 4-arsonoanilinium species, namely in the hydrochloride salt, C6H9AsNO3 +·Cl−, (I), and the complex salts formed from the reaction of (4-aminophenyl)arsonic acid (p-arsanilic acid) with copper(II) sulfate, i.e. hexaaquacopper(II) bis(4-arsonoanilinium) disulfate dihydrate, (C6H9AsNO3)2[Cu(H2O)6](SO4)2·2H2O, (II), with copper(II) chloride, i.e. poly[bis(4-arsonoanilinium) [tetra-μ-chlorido-cuprate(II)]], {(C6H9AsNO3)2[CuCl4]} n , (III), and with cadmium chloride, i.e. poly[bis(4-arsonoanilinium) [tetra-μ-chlorido-cadmate(II)]], {(C6H9AsNO3)2[CdCl4]} n , (IV), have been determined. In (II), the two 4-arsonoanilinium cations are accompanied by [Cu(H2O)6]2+ cations with sulfate anions. In the isotypic complex salts (III) and (IV), they act as counter-cations to the {[CuCl4]2−} n or {[CdCl4]2−} n anionic polymer sheets, respectively. In (II), the [Cu(H2O)6]2+ ion sits on a crystallographic centre of symmetry and displays a slightly distorted octahedral coordination geometry. The asymmetric unit for (II) contains, in addition to half the [Cu(H2O)6]2+ ion, one 4-arsonoanilinium cation, a sulfate dianion and a solvent water molecule. Extensive O—H...O and N—H...O hydrogen bonds link all the species, giving an overall three-dimensional structure. In (III), four of the chloride ligands are related by inversion [Cu—Cl = 2.2826 (8) and 2.2990 (9) Å], with the other two sites of the tetragonally distorted octahedral CuCl6 unit occupied by symmetry-generated Cl-atom donors [Cu—Cl = 2.9833 (9) Å], forming a two-dimensional coordination polymer network substructure lying parallel to (001). In the crystal, the polymer layers are linked across [001] by a number of bridging hydrogen bonds involving N—H...Cl interactions from head-to-head-linked As—O—H...O 4-arsonoanilinium cations. A three-dimensional network structure is formed. CdII compound (IV) is isotypic with CuII complex (III), but with the central CdCl6 complex repeat unit having a more regular M—Cl bond-length range [2.5232 (12)–2.6931 (10) Å] compared to that in (III). This series of compounds represents the first reported crystal structures having the protonated 4-arsonoanilinium species.

The coordination complex structures and hydrogen bonding in the three-dimensional alkaline earth metal salts (Mg, Ca, Sr and Ba) of (4-aminophenyl)arsonic acid

(4-Aminophenyl)arsonic acid (p-arsanilic acid) is used as an antihelminth in veterinary applications and was earlier used in the monosodium salt dihydrate form as the antisyphilitic drug atoxyl. Examples of complexes with this acid are rare. The structures of the alkaline earth metal (Mg, Ca, Sr and Ba) complexes with (4-aminophenyl)arsonic acid (p-arsanilic acid) have been determined, viz. hexaaquamagnesium bis[hydrogen (4-aminophenyl)arsonate] tetrahydrate, [Mg(H2O)6](C6H7AsNO3)·4H2O, (I), catena-poly[[[diaquacalcium]-bis[μ2-hydrogen (4-aminophenyl)arsonato-κ2 O:O′]-[diaquacalcium]-bis[μ2-hydrogen (4-aminophenyl)arsonato-κ2 O:O]] dihydrate], {[Ca(C6H7AsNO3)2(H2O)2]·2H2O} n , (II), catena-poly[[triaquastrontium]-bis[μ2-hydrogen (4-aminophenyl)arsonato-κ2 O:O′]], [Sr(C6H7AsNO3)2(H2O)3] n , (III), and catena-poly[[triaquabarium]-bis[μ2-hydrogen (4-aminophenyl)arsonato-κ2 O:O′]], [Ba(C6H7AsNO3)2(H2O)3] n , (IV). In the structure of magnesium salt (I), the centrosymmetric octahedral [Mg(H2O)6]2+ cation, the two hydrogen p-arsanilate anions and the four water molecules of solvation form a three-dimensional network structure through inter-species O—H and N—H hydrogen-bonding interactions with water and arsonate O-atom and amine N-atom acceptors. In one-dimensional coordination polymer (II), the distorted octahedral CaO6 coordination polyhedron comprises two trans-related water molecules and four arsonate O-atom donors from bridging hydrogen arsanilate ligands. One bridging extension is four-membered via a single O atom and the other is eight-membered via O:O′-bridging, both across inversion centres, giving a chain coordination polymer extending along the [100] direction. Extensive hydrogen-bonding involving O—H...O, O—H...N and N—H...O interactions gives an overall three-dimensional structure. The structures of the polymeric Sr and Ba complexes (III) and (IV), respectively, are isotypic and are based on irregular MO7 coordination polyhedra about the M 2+ centres, which lie on twofold rotation axes along with one of the coordinated water molecules. The coordination centres are linked through inversion-related arsonate O:O′-bridges, giving eight-membered ring motifs and forming coordination polymeric chains extending along the [100] direction. Inter-chain N—H...O and O—H...O hydrogen-bonding interactions extend the structures into three dimensions and the crystal packing includes π–π ring interactions [minimum ring centroid separations = 3.4666 (17) Å for (III) and 3.4855 (8) Å for (IV)].

Hexaaquamanganese(II) bis[hydrogen (4-aminophenyl)arsonate] tetrahydrate

In the structure of the complex salt formed from the reaction of manganese(II) acetate with (4-aminophenyl)arsonic acid (p-arsanilic acid), [Mn(H2O)6](C6H7AsNO3)2·4H2O, the centrosymmetric Mn(H2O)6coordination polyhedron has slightly distorted octahedral stereochemistry, with the two hydrogen (4-aminophenyl)arsonate anions and the four water molecules of solvation related by inversion. Extensive O—H...O, O—H...N and N—H...O hydrogen bonds link all species, giving an overall three-dimensional supramolecular structure, which also has weak π–π ring interactions [minimum ring-centroid separation = 3.7304 (15) Å]. The structure is isotypic with that of the Mg salt.

Lewisite exposure biomarkers in urine by liquid chromatography – inductively coupled plasma tandem mass spectrometry: with an accelerated matrix-matched stability study

A simple and robust LC-ICP-MS/MS method is described for quantitative analysis of human urine for (2-chlorovinyl)arsonic acid (CVAOA), a metabolite of Lewisite.