EXTRACTION DE L'ARSENIC EN SOLUTION DANS DES LIQUEURS CONTENANT DES CARBONATE, SULFATE, EVENTUELLEMENT DE L'HYDROXYDE, ALCALINS, AINSI QUE L'UN AU MOINS DES METAUX VANADIUM, URANIUM ET MOLYBDENE

摘要

The parent patent describes a process for purifying solns. contg. alkali metal (bi)carbonate, sulphate and/or hydroxide as well as one or more of vanadium, uranium and molybdenum in the form of the alkali metal salt(s). The process comprises (i) heating the soln. at its b.pt. or above with 0.1-20 times the stoichiometric amt. of lime required to convert the (bi)carbonate content into alkalimetal hydroxide (ignoring the amt. of lime required to ppte. insol. calcium cpds. of V,U and MO); (ii) separating the alkali metal hydroxide-enriched liquor from the ppte. contg. mainly calcium carbonate and a mixt. of other (in)organic calcium salts, and washing the ppte; (iii) concentrating the combined liquor and wash liquor by evap. to an alkali metal hydroxide content of at least 50% to form a second ppte. (mainly alkali metal sulphate); and (iv) sepg. the ppte. to recover the alkali metal hydroxide-rich liquor. In the present invention, the soln. is treated, prior to step (i), with a magnesium cpd. in at least the stoichiometric amt. required to ppte. magnesium arsenate. The process is used to purify leach solns. for recycling in the leaching of uranium or vanadium minerals (opt. contg. molybdenum) after pptn. and sepn. of the metal values.