METHOD FOR PURIFYING CONCENTRATED SPENT AQUEOUS SOLUTIONS FROM CHROME (VI) COMPOUNDS Russian patent published in 1998 - IPC

FIELD: environmental control; recovery of hexavalent chrome compounds from solutions resulting from electroplating operations; reduction of hexavalent chrome to trivalent chrome for subsequent use as tanning agent for furs and leather. SUBSTANCE: aqueous hexavalent chrome solution with specific concentration is pre-mixed with sawdust, thoroughly stirred, followed by adding concentrated sulfuric acid to prepared mixture. As components are taken in specific proprietary weight ratio, hexavalent chrome is completely reduced to trivalent chrome. Method is environmentally acceptable and energy saving as it is associated with exothermic effect. The latter also determines its high reaction velocity. EFFECT: higher efficiency. 1 tbl