A natural zeolite (pore size 0.40-0.78 nm) was modified by HCl or Mn ions and used for removal of Ni(2+) and Cu(2+) ions from aq. solns. at pH 1.8-13.3. Pptn. of Ni(OH)(2) and Cu(OH)(2) was obsd. at pH about 10 and 8.5-11.7, resp. The zeta potential of coagulated Ni hydroxocomplexes decreased while their size increased with increasing pH. Both zeta potential of coagulated Cu hydroxocomplexes and their size showed a broad max. at pH 7.2-8.4.