METHOD OF PROCESSING OF SODIUM HYDROLYSINE ARSENITE Russian patent published in 2017 - IPC C01G28/00 

FIELD: chemistry.

SUBSTANCE: method of processing sodium hydrolysis arsenite involves leaching arsenic salts by the first step of acidifying sodium arsenite with hydrolysed hydrochloric acid, separating the precipitate and the filtrate. Concentration of the filtrate by evaporation. The concentrated filtrate is separated from the resulting precipitate containing sodium chloride and arsenic compounds. The arsenic (III) oxide is then precipitated by the second step of acidifying the filtrate with hydrochloric acid. After separation of the arsenic (III) oxide precipitate, soluble lanthanum compounds are added to the formed filtrate at pH 6.0 before precipitation of arsenic compounds (V). According to the method, before leaching, sodium hydrolysis sodium arsenite is dissolved in water or in a liquid, which is a mixture of filtrates, washings and condensates obtained at different stages of the technological cycle, with the separation of water-insoluble substances by filtration. The first stage of acidification is carried out to pH 8.0-9.0. Evaporation of the filtrate is carried out to a concentration of sodium arsenite of at least 20 wt %. The second stage of acidification is carried out to a pH of 6.0±0.2. A precipitate containing sodium chloride and arsenic is diluted with water to a 20% solution, sodium hydroxide is added to the solution to pH 7.0-8.5 and soluble lanthanum compounds are precipitated with arsenic (V) compounds. The filtrate is subjected to adsorption purification and sodium chloride is isolated therefrom. Arsenic compounds (V) are mixed with hydrochloric acid, hydrogen sulphide or sodium sulfide is introduced, the resulting precipitate is oxidised to give arsenic oxide (III). Arsenic compounds (V) are precipitated from the filtrate.

EFFECT: reduction of labor intensity of the process due to exclusion of the stage of reduction of arsenic compounds in arsenic compounds and increase of its ecological compatibility by ensuring the closure of the processing cycle.

1 dwg