Continuous process for the removal of chromium from waste waters and valorization of the recovered chromium

摘要

A continuous process is described, wherein chromium-containing waste waters are subjected to continuous hot treatment with acetic acid or with alkaline acetates and alkaline hydroxides at a temperature from 40° C. to boiling point and at atmospheric pressure, at a pH higher than 6.5, preferably between 7 and 10, particularly about 7.5. Thus, a "sandy" type of chromium hydroxide is obtained, having a titer in Cr.sub. 2 O.sub. 3 of 20 to 40% by weight, which quickly filters, is easily soluble in acids, and thereby affords an easy valorization both as a tanning agent and as a raw material for preparing other chromium compound.