An organic-inorganic nanocomposite cation-exchanger, i.e. poly-o-toluidine Zr(IV) phosphate was synthesized via sol-gel mixing of an electrical conducting polymer poly-o-toluidine into the matrices of inorganic precipitate of Zr(IV) phosphate. The ion-exchange capacity, chemical stability, effect of eluant concentration, elution behavior, pH titration and thermal studies were also carried out to understand the ion-exchange capabilities. The physico-chemical properties of the material were determined using AAS, CHN elemental analysis, FTIR, TGA-DTA, XRD, TEM and SEM studies. On the basis of distribution studies, the material was found to be highly selective for Hg(II). Its selectivity was examined by achieving some important binary separations like Hg(II)-Pb(II), Hg(II)-Cu(II), Hg(II)-Co(II), Hg(II)-Fe(III), Hg(II)-Sr(II), etc. on its column. This material possessed d.c. electrical conductivity in the semi-conducting range, i.e. 10(-3) to 10(-2) Scm(-1); measured by four-in-line probe d.c. electrical conductivity-measuring technique. The d.c. electrical conductivity of the composite material was found stable upto 110 degrees C for the composites under ambient conditions. (C) 2008 Elsevier Ltd. All rights reserved.