MEMBRANE PROCESSES FOR METAL RECOVERY AND POLLUTION CONTROL IN METAL PROCESS INDUSTRIES

摘要

MEMBRANE PROCESSES FOR METAL RECOVERYAND POLLUTION CONTROL IN METAL PROCESS INDUSTRIES-ABSTRACT OF THE DISCLOSURE:A process for the treatment of an aqueousstream containing an acid or base and typically a pre-cipitatable material such as a metal ion comprises:(a) subjecting the aqueous stream to (i) atreatment to produce a relatively pure stream of waterand a concentrated aqueous stream, and (ii) watersplitting to produce a stream of base, a stream of acidand a dilute aqueous stream of a concentration lower thanthe concentrated aqueous stream, the treatments (i) and(ii) being effected in either order,(b) recycling at least part of the pure waterstream produced in (a)(i) to an earlier stream either inthe production leading to said aqueous stream or to step(i) or (ii),(c) recycling at least part of the acid and/orbase streams produced in (a)(ii) to an earlier streameither in the production leading to said aqueous streamor to an earlier step in the process, and(d) recycling at least part of the lower con-centration stream produced in (a)(ii) to either (a)(i) orto another step in the process,whereby, when present, only the precipitatable materialis removed from the aqueous stream, thereby obviatingtoxic waste disposal problems.