Process for the removal of heavy metals from aqueous liquids

Claim 1

A process for homogeneously precipitating heavy metal ions selected from the group consisting of chromium ions, zinc ions, and lead ions from aqueous liquids containing same consisting essentially of separately but simultaneously adding (1) an aqueous liquid containing said heavy metal ions in the form of a heavy metal salt selected from the group consisting of chromium sulphate, zinc sulphate, and lead sulphate and (2) an aqueous liquid containing a base that precipitates the heavy metal ion of said heavy metal salt in the form of its hydroxide or basic salt to a quantity of water that (a) is being stirred, (b) has a pH between 5 and 10, and (c) is at a temperature ranging from about 60° C. to about 100° C. to cause homogeneous precipitation of the heavy metal hydroxide or basic salt, wherein the pH of the resulting solution is maintained between 6 and 8 by adjusting the rates of addition of aqueous liquid (1) and aqueous liquid (2) and wherein the temperature is held within the range from about 60° C. to about 100° C. during the homogeneous precipitation, and separating the precipitated heavy metal hydroxide or basic salt from the resulting solution.