7778-39-4Relevant academic research and scientific papers
Rapid catalytic oxidation of As(iii) to As(v) using a: Bacillus spore-2,2,6,6-tetramethylpiperidine-1-oxyl system
Qin, Yuqing,Peng, Fei,Hu, Yonggang
, p. 2286 - 2294 (2019/05/21)
The oxidation of As(iii) to As(v) is a critical process in the treatment of contaminated water. We found that 95% As(iii) (10 mg L-1) could be rapidly oxidized to As(v) by a laccase-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) system in 1 h. Based on this finding, we used Bacillus subtilis spores instead of laccase for As(iii) oxidation with the same effect because the former had plenty of CotA-laccase on their surface. The catalytic ability of CotA protein and spores was confirmed by expressing the CotA protein and knocking out the cotA gene from wild-type spores. Both laccase- and spore-TEMPO systems displayed similar oxidation rate constants, Michaelis-Menten constants, and maximal velocities owing to the formation of the oxoammonium cation of TEMPO in the presence of dissolved oxygen. Several other laccase mediators such as 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic-acid) (ABTS), acetosyringone (AS), 1-hydroxybenzotriazole (HBT), 2-hydroxybutyl acrylate (HBA), violuric acid (VLA), 4-oxo-TEMPO, 4-amino-TEMPO, 4-methoxy-TEMPO, 4-hydroxy-TEMPO benzoate, and 4-hydroxy-TEMPO coupled with spores for As(iii) oxidation were also investigated in detail. The spore-TEMPO system exhibited the highest oxidation efficiency and tolerated the addition of 10 mg L-1 Al3+, Ti4+, Cu2+, K+, Fe3+, Zn2+, Ni2+, Mg2+, Co2+, and Mn2+. Both laccase and spores recovered via ultrafiltration and centrifugation, respectively, could be reused for at least five cycles. The developed spore-based system has several advantages including eco-friendliness, ease of operation and storage, low cost, recyclability, sustainability, and without the need for enzyme purification. These findings may have promising implications for developing a new eco-friendly and cost-effective technology for the treatment of arsenic-containing water.
Compatible Mechanism for a Simultaneous Description of the Roebuck, Dushman, and Iodate-Arsenous Acid Reactions in an Acidic Medium
Valkai, László,Horváth, Attila K.
, p. 1595 - 1603 (2016/02/27)
The iodine-arsenous acid (Roebuck), iodide-iodate (Dushman), and iodate-arsenous acid reactions have been studied simultaneously by a stopped-flow technique by monitoring the absorbance-time profiles at the isosbestic point of the I2/I3- system (468 nm). Using the well-accepted rate coefficients of iodine hydrolysis, we have proven that iodine is the kinetically active species of the iodine-arsenous acid reaction. Strong iodide inhibition of this system is explained by a rapidly established equilibrium between iodine and arsenous acid to produce an iodide ion, a hydrogen ion, and a short-lived intermediate H2AsO3I, which is shifted far to the left. Taking into consideration the generally accepted kinetic model of the Dushman reaction where I2O2 plays a key role to account for all of the most important observations in this subsystem and a sequence of simple formal oxygen-transfer reactions between arsenous acid and iodic acid as well as iodous acid and hypoiodous acid, we propose a 13-step comprehensive kinetic model, including seven rapidly established equilibria with only six fitted parameters, that is able to explain all of the most important characteristics of the kinetic curves of all of the title systems both individually and simultaneously.
Synthesis, structure, and thermal expansion of sodium zirconium arsenate phosphates
Sukhanov,Pet'Kov,Firsov,Kurazhkovskaya,Borovikova
, p. 1351 - 1357 (2011/12/14)
Sodium zirconium arsenate phosphates NaZr2(AsO4) x (PO4)3-x were synthesized by precipitation technique and studied by X-ray diffraction and IR spectroscopy. In the series of NaZr2(AsO4) x (PO4)3-x, continuous substitution solid solutions are formed (0 ≤ x ≤ 3) with the mineral kosnarite structure. The crystal structure of NaZr2(AsO 4)1.5(PO4)1.5 was refined by full-profile analysis: space group R c, a = 8.9600(4)?, c = 22.9770(9) ?, V = 1597.5(1) ?3, R wp = 4.55. The thermal expansion of the arsenate-phosphate NaZr2(AsO4) 1.5(PO4)1.5 and the arsenate NaZr 2(AsO4)3 was studied by thermal X-ray diffraction in the temperature range of 20-800°C. The average linear thermal expansion coefficients (αav = 2.45 × 10-6 and 3.91 × 10-6 K-1, respectively) indicate that these salts are medium expansion compounds.
Iron arsenate frameworks
Wiggin, Seth B.,Hughes, Robert W.,Price, Daniel J.,Weller, Mark T.
, p. 2935 - 2941 (2008/02/10)
Six new iron arsenate framework structures, Fe2As 2O7·2H2O, [Fe6As 8O32H4]2-(1,4-butanediamininium 2+)·2H2O, [Fe4As6/
Synthesis and proposed crystal structure of a disordered cadmium arsenate apatite Cd5(AsO4)3Cl1-2x-yO x□xOHy
Johnson, Christopher D.,Feldmann, Joerg,Macphee, Donald E.,Worrall, Fred,Skakle, Janet M.S.
, p. 3611 - 3615 (2007/10/03)
During a study into the synthesis of minerals composed of mining wastes aimed at improving their immobilisation, a cadmium arsenate apatite has been prepared by hydrothermal methods. The structure of this apatite was analysed by single crystal X-ray diffraction, and was found to consist of a standard apatite framework based on Cd5(AsO4)3X, where X represents an anion resident on the (0,0,0.25) site. The framework is hexagonal with the space group P63/m (no 176), a = 9.9709(8), c = 6.4916(4) A. The X ion site is predominantly occupied by Cl- ions; however due to significant shortening of the c axis exhibited by all cadmium containing apatite phases, a pure chlorapatite is not possible without a significant cation deficiency. No evidence of the necessary deficiency was found in the crystal structure. For larger bromo- and iodo-apatites significant modulations along the c-axis are required to accommodate the halide. This paper examines a number of compensation mechanisms and proposes that a minor disorder of chloride, oxide and hydroxide located on the X ion site provides the required charge compensation mechanism. This is contrary to previous complex modulations proposed in the literature, The proposed chemical formula is Cd 5(AsO4)3Cl1-2x-yO x□xOHy where □ represents a vacancy.
Synthesis and TG/DTA study on two new metallo(VI)-arsenato(V) heteropolyacids containing vanadium(V)
Fodor,Ghizdavu,?uteu,Caraban
, p. 153 - 158 (2008/10/09)
An improved method for the synthesis of two heteropolyacids of the same type: H5[AsMo10V2O40]· 13H2O and H5[AsW10V2O40] ·16H2O was elaborated. Th
Electrochemical preparation of arsenic and its compounds
Smetanin,Smirnov,Chernykh,Turygin,Khudenko,Fedorov,Tomilov
, p. 22 - 36 (2008/10/08)
Electrochemical processes are used to recover elemental arsenic from NaH2AsO3 solutions, oxidize As2O3 suspensions to arsenic acid, and reduce arsenic acid to arsine. The electrolysis conditions are optimized for obtaining elemental arsenic: 0.8-0.9 M NaH 2AsO3, 0.03-0.05 A/cm2, 20-25°C. The introduction of tetraalkylammonium salts containing C9-C12 substituents, e.g., trimethylcetylammonium bromide, is shown to stabilize the current efficiency in terms of As at a level of 45-50%. The current efficiency of copper cathodes attains 89% in 1-2 M H3AsO4 solutions at a current density of 0.2 A/cm2. In the electrosynthesis of arsenic acid, quantitative substance and current yields are achieved in 2-3 M HCl solutions. Low-waste processes are proposed for preparing arsenic, H 3AsO4, and As2O5 from As 2O3. The resulting arsenic is suitable for producing high-purity (99.9999%) material. The physicochemical processes underlying arsine generation are examined, and a bench-scale electrochemical arsine generator is described which can be used in the manufacturing of semiconductor materials.
Electrochemical synthesis of arsenic acid
Turygin,Smetanin,Khudenko,Tomilov
, p. 1237 - 1239 (2007/10/03)
The possibility of oxidizing arsenic(III) oxide to arsenic acid in quantitative yield in the presence of hydrochloric or hydrobromic acid as a catalyst was studied.
Thermochemistry of High-Temperature Phases of Zirconium and Hafnium Pyrophosphates and Pyroarsenates
Karyakin,Chernorukov,Bondareva
, p. 701 - 704 (2008/10/08)
Using the adiabatic calorimetry method, the standard enthalpy of formation at T = 298.15 K (kJ/mol) was found to be -2806.0 ± 4.0 for β-ZrP2O7, -1975.0 ± 6.0 for β-ZrAs2O7, -2827.5 ± 4.0 for β-HfP2O7, and -2006.5 ± 4.0 for β-HfAs2O7. Based on these data, the enthalpies of polymorphic transitions in pyrophosphates (pyroarsenates) from the low-temperature to the high-temperature phase and the enthalpies of thermal decomposition of the compounds under consideration were derived.
Phase Equilibria in the As2O5-CdO System
Kasenov,Mustafin,Makitova
, p. 1922 - 1926 (2008/10/08)
A T-x diagram of the As2O5-CdO system is studied by X-ray diffraction analysis. Three cadmium arsenates - hexagonal Cd(AsO3)2, melting incongruently at 760°C; orthorhombic Cd2As2O7, melting incongruently at 930°C; and monoclinic Cd3(AsO4)2, melting congruently at 1070°C - are found to exist. Heat capacities of these compounds are measured between 298.15 and 673 K by dynamic calorimetry. The thermodynamic functions S°(T), H°(T)-H°(298.15), and ΦXX(T) are calculated.
