METHOD FOR CLEANING ULTRADISPERSED DIAMONDS Russian patent published in 1997 - IPC

FIELD: production of industrial diamonds, environmental control. SUBSTANCE: feed material comprising ultradispersed diamonds is subjected to mechanical filtration, treated with concentrated sulfuric acid, followed by heating. Next oxidizing agent, namely, aqueous solution of chromic anhydride is added to heated mixture of feed material with sulfuric acid to form reaction mixture comprising sulfuric acid, chromic anhydride and water in following ratio, wt.%: sulfuric acid 28-30, chromic anhydride 14-16, water being balance. Diamonds are washed out with water to remove acid treatment products, resulting effluents are neutralized and neutralization products are recovered. Mechanical filtration is carried out using set of vibratory sieves. Feed material is treated with sulfuric acid at 105-110 C for 1.0-1.5 hours. Ultradispersed diamonds are washed for removing acid treatment products first with water at 60-70 C to pH = 5-6, next with hot distilled water until negative reaction to chromium ions present in effluents is achieved, followed by neutralization of effluents by successively adding to them barium chloride and sodium hydroxide. Finally, resulting sediment is removed. EFFECT: higher product purity, intensified process, better environment protection offered. 4 cl