Organic impurities are removed from aq. solns. by treatment with combinations of macroporous, weakly-to-medium basic anion-exchanger resins, (I), present in salt form, and macroporous, weakly acidic cation exchanger resins, (II), present in H-form. Wt. ratio (I):(II) is pref. 9:1 to 1:9 (2:1 to 1:2). The resins may be used either as superimposed filter layers or as a mixed bed. Used esp. for purifying waste waters from chemical, textile, paper and leather works, opt. after a biological, chemical and/or mechanical pre-clarifying treatment. Cationic, anionic and non-ionic organic cpds. are adsorbed simultaneously; regeneration can take place with one elution soln.; (I) and (II) need not be separated before elution; total vol. of (I) and (II) and flow-resistance through filter bed change but little during elution, conditioning and charging.
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