7778-39-4Relevant articles and documents
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.
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.
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.
