Authors: M.O. Moldurushku, A.F. Chuldum

Title of the article: Study of water leaching of arsenic-containingf roasting product

Year: 2020, Issue: 3, Pages: 13-18

Branch of knowledge: 05.17.01 Technology of inorganic substances

Index UDK: 66.061.16; 66.065.5; 546.19

DOI: 10.26730/1999-4125-2020-3-13-18

Abstract: The arsenic waste recycling is a pressing problem. The study of water leaching process of arsenic-containing product of the roasting with the subsequent crystallization from sodium arsenate solution is the objective of this paper. The product of the roasting was obtained by roasting sludge/soda/coal (ratio 1:1:0,1) at 800 – 850°С during 3 h. As a result of residue water leaching, up to 76 % of the arsenic content goes to the solution. The values of change in the enthalpy of dissolution (∆Hsol) of anhydrous and hydrated sodium arsenate at 25°C were -129,6; 52,7 kJ/mol; estimated assessment of change in Gibbs energies (∆G) -185; -2,76 kJ/mol, respectively. It was shown that with temperature increasing to 70°C, the solubility of hydrated sodium arsenate and the arsenic extraction degree in the solution increase, a further increase in temperature slightly affects the solubility of arsenic. It was also noted that when the solution was cooled from 70 to 25°С, a white precipitate was formed from the solution. The composition of the precipitate and alkaline solution was considered. The composition of the precipitate at room temperature is represented by particles of sodium arsenate, soda. Also, there are silicon, chlorine, and potassium present in the precipitate. The solution predominantly contains ions of bicarbonates, carbonates, in order of decreasing are ions of sulfate, chloride, magnesium, calcium. Over time, the concentration of arsenic ions decreases from 5,8 to 2 g/l, which is associated with the precipitation of arsenic. The solution was evaporated under isothermal conditions. The precipitate composition after evaporation is mainly represented by particles of sodium arsenate; soda and silicon are present in the precipitate.

Key words: water leaching sodium arsenate enthalpy of dissolution alkaline solution precipitate evaporation

Receiving date: 23.06.2020

Publication date: 30.09.2020

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