METHOD OF OBTAINING ELEMENTARY ARSENIC AND SODIUM CHLORIDE FROM PRODUCTS OF ALKALINE HYDROLYSIS OF LEWISITE Russian patent published in 2011 - IPC A62D3/36 A62D3/37 A62D101/02 A62D101/40 

FIELD: chemistry.

SUBSTANCE: invention relates to destruction of chemical weapons and more specifically to methods of processing reaction mass formed during a basic industrial process - alkaline hydrolysis of a lewisite. The method of obtaining elementary arsenic and sodium chloride from processing solutions which contain metal arsenites, mainly products of alkaline hydrolysis of a lewisite, is characterised by that processing is carried out in a closed process loop which involves removal of mechanical impurities and insoluble substances by filtering the initial product to obtain an alkaline filtrate, reduction of an arsenic-containing compound to elementary arsenic through the effect of sodium borohydride NaBH₄ on the alkaline filtrate, filtration of the obtained heterogeneous system to separate sodium chloride solution from arsenic, which is taken for post-reduction, re-filtration of the heterogeneous system to separate arsenic, purification of the latter by repulping in aqueous and chloride media, separation of the obtained arsenic precipitate, washing said precipitate with water and alcohol, evaporation in a vacuum at 180-200°C, analysis for content of the main substances and impurities, unpacking in form of a commercial product; where after re-separation of arsenic, the filtrate which contains a mixture of sodium chloride and hydroxide, as well as residual arsenic-containing compounds are further reduced in 1-2 days, after which the obtained purified aqueous sodium chloride solution is acidified with hydrochloric acid to a neutral medium, passed through a sorbent layer and evaporated in a vacuum. The obtained salt mass is centrifuged to obtain technical sodium chloride. Condensates from vacuum-evaporating apparatus are returned to the process.

EFFECT: method is efficient, produces few wastes and is environmentally safe.

6 cl, 1 dwg