Arsenate and arsenite

Arsenite can also be separated by ion chromatography using standard conditions. It elutes early, near the carbonate dip. For these applications the ultraviolet detector should be placed between the separator and suppressor columns. 

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Wilson and Dickenson observed no exchange, over a period of three hours at 100 °C, between arsenate and arsenite ions in media ranging from aqueous acid to aqueous alkali. Martin et al have found similar results for the exchange between arsenate and thioarsenite ions in aqueous media. However, in liquid ammonia exchange occurred between ammonium arsenate and arsenic trisulphide. The isotopic method was used -... 

Sato, T. and Kobayashi, Y., The ars operon in the skin element of Bacillus subtilis confers resistance to arsenate and arsenite, J Bacteriol, 180 (7), 1655-1661, 1998. 

Goldberg (2002) found no evidence of any competition in sorption of arsenate and arsenite on Al or Fe-oxides and montmorillonite, but only a small and apparent competitive effect of equimolar arsenate on arsenite sorption on kaolinite and illite. The minor competitive effect in this study was due to the small concentrations of arsenic which is very low for saturation site. Competition for sorption sites is evident by increasing the surface coverage of the sorbents. Arsenate prevents arsenite sorption on metal oxides when the surfaces of the sorbents are saturated by the anions (Jain and Loeppert 2000 Violante and Pigna 2002). 

The effect of other inorganic anions (sulfate, molybdate, silicate), low molecular mass organic ligands (LMMOLs, such as oxalate, malate, citrate, tartrate and succinate), and fulvic or humic acid on the sorption of arsenate and arsenite onto variable charge minerals and soils has been studied (Roy et al. 1986 Grafe et al. 2001 Liu et al. 2001 Violante et al. 2005a,b). 

Kampf N, Scheinost AC, Schultze DG (2000) Oxides minerals. In Sumner ME (ed) Handbook of soil science, CRC Press, Boca Raton (FL), F125-F168 Jain A, Loeppert RH (2000) Effect of competing anions on the adsorption of arsenate and arsenite by ferrihydrite. J Environ Qual 29 1422-1430 Jain A, Raven KP, Loeppert RH (1999) Arsenite and arsenate adsorption on ferrihydrite surface charge reduction and net OH release stoichiometry. Environ Sci Technol 33 1179-1184... 

Sun X, Doner, HE (1996) An investigation of arsenate and arsenite bonding structures on goethite by FTIR. Soil Sci 161 865-872 Sun X, Doner HE (1998) Adsorption and oxidation of arsenite on goethite. Soil Sci 163 278-287... 

Haywood and Riley [14] have described a spectrophotometric method for the determination of arsenic in seawater. Adsorption colloid flotation has been employed to separate phosphate and arsenate from seawater [15]. These two anions, in 500 ml filtered seawater, are brought to the surface in less than 5 min, by use of ferric hydroxide (added as 0.1 M FeC 2 ml) as collector, at pH 4, in the presence of sodium dodecyl sulfate [added as 0.05% ethanolic solution (4 ml)] and a stream of nitrogen (15 ml/minutes). The foam is then removed and phosphate and arsenate are determined spectrophotometrically [16]. Recoveries of arsenate and arsenite exceeding 90% were obtained by this procedure. 

Johnson and Pilson [229] have described a spectrophotometric molybdenum blue method for the determination of phosphate, arsenate, and arsenite in estuary water and sea water. A reducing reagent is used to lower the oxidation state of any arsenic present to +3, which eliminates any absorbance caused by molybdoarsenate, since arsenite will not form the molybdenum complex. This results in an absorbance value for phosphate only. 

Bottino, N.R., R.D. Newman, E.R. Cox, R. Stockton, M. Hoban, R.A. Zingaro, and K.J. Irgolic. 1978. The effects of arsenate and arsenite on the growth and morphology of the marine unicellular algae Tetraselmis chui (Chlorophyta) and Hymenomonas carterae (Chrysophyta). Jour. Exp. Mar. Biol. Ecol. 33 153-168. 

Su C., Puls R.W., Arsenate and arsenite removal by zero-valent iron kinetics, redox transformation, and implications for in situ groundwater remediation, Environ. Sci. Technol. 35,2001, 1487-1992. 

As conclusion, Zr(IV) loaded Diaion CRP200 will be promising in the removal of arsenite and arsenate, whereas much more detailed studies will be needed about its behavior in the removal of sub-ppm levels of both arsenate and arsenite. However, we would like to emphasize that all results described here were obtained by using the single column during ca. 2 years... 

Chanda, M., O Driscoll, K. F., Rempel, G. L., Ligand exchange sorption of arsenate and arsenite anions by chelating resins in ferric ion form I. Weak-base chieating resin Dow XFS-4195. Reactive Polym. 7,1988, 251-261. 

Arsenate and arsenite from ground water Zr-clinoptilolite [228]... 

Biochemical effects of arsenate and arsenite are considered in this review. Enzymes that normally act on substrates of structure R— — P03H2 (i.e., of oxidation state V) often act on the analogues R—CH2— P03H2 and R— —As03H2. The further arsonic acid analogue R—CH2 —As03H2, which may have unusual effects, is considered. 

As203 + 3PC13 + 9H20 = 2As + 3H3P04 + 9HC1 A similar reaction occurs also with arsenates and arsenites, and is... 

Sodium hydrosulphite reduces arsenates and arsenites, yielding precipitates containing sulphides the composition of which varies with conditions. In strongly acid solutions arsenic trisulphide is the main product.2 Sodium thiosulphate also precipitates arsenic as the trisulphide from acid solutions,3 but the amount of precipitation depends on the nature and concentration of the acid present. Thus, with hydrochloric, perchloric or sulphuric acid, the precipitation reaches a maximum of 50 to 80 per cent, for 0-1N acid,4 and above this concentration the amount of precipitation falls to zero with hydrochloric acid but passes through a minimum with perchloric acid at N concentration and with sulphuric acid at 2 to 3N concentration. At still higher acid concentrations precipitation becomes almost quantitative. 

In spite of the fact that ISEs for more than 60 ions have been described so far, recent findings imply that these ISEs should be re-characterized and re-optimized for trace level applications [19]. The list of ISEs with low-level LODs needs to be expanded either by re-characterization of existing ionophores or by synthesis of new ones. Important ions for which low LODs have yet to be demonstrated are, for example, mercury, chromium, nickel, arsenate and arsenite ions. Hopefully, synthetic chemists will rise to the challenge and new, selective ionophores will be developed that will achieve this goal. 

Ghimire, K.N., Inoue, K., Yamaguchi, H. et al. (2003) Adsorptive separation of arsenate and arsenite anions from aqueous medium by using orange waste. Water Research, 37(20), 4945-53. 

Masue, Y., Loeppert, R.H. and Kramer, T.A. (2007) Arsenate and arsenite adsorption and desorption behavior on coprecipitated aluminum iron hydroxides. Environmental Science and Technology, 41(3), 837-42. 

Payne, K.B. and Abdel-Fattah, T.M. (2005) Adsorption of arsenate and arsenite by iron-treated activated carbon and zeolites effects of pH, temperature, and ionic strength. Journal of Environmental Science and Health, Part A Toxic/Hazardous Substances and Environmental Engineering, 40(4), 723-49. 

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