METHOD FOR RECYCLING OF EFFLUENC OF IONEXCHANGE METHOD

摘要

Zn is recovered from waste by prods. of ion exchange resin prodn. Reactor residues are either untreated or pretreated prior to further processing. Untreated residues contain HCl, ZnCl2 and organic material soln. Zn concentration is boosted during pretreatment by addn. of ZnCO3. Both residues are processed further by adding alkali-hydroxides or alkaline-phosphate ions. Resulting Zn contg. ppts, organic cpds. and dissolved chlorides, that have cations corresponding to the hydroxides and phosphates employed, are sepd. by known means. A 10-60 pref. 40-50% aq. soln. of KOH or NaOH is added to neutralise HCl in unpretreated residues, and their Zn content is pptd. by addn. of an alkali-phosphate soln. Following the sepn. of Zn3(PO4)2, the remaining chloride solns. are crystallised out by cooling and/or by vacuum distn. A similar process may be used in case of pretreated residues. Alternatively, followiing neutralisation, the Zn content is pptd. as Zn(OH)2 by addn. of further alkali hydroxide soln. The concn. of the latter is chosen in such a manner, that the reaction temp. should be in the 60-100 pref. 70-80 deg.C range. A three-phase system is formed comprising Zn(OH)2 ppt., aq. alkali-chloride soln. and the organic phase. The organic phase is sepd., Zn(OH)2 is filtered out while still warm and dissolved in a mineral acid (HCl, H2SO4 or HNO3) to form a corresponding Zn salt soln. Both the Zn salt soln. and the remaining Cl- soln. is crystallised out by cooling and/or vacuum distn.