Synthesis and characterisation of chromium-selective porous condensate polymers

Abstract

A series of porous condensate polymers were synthesised by catechol-phenol-paraformaldehyde polycondensation using 1,2-ethanediol as the porosogenic agent. They were thoroughly characterised for moisture content, ion-exchange capacity, solvent uptake, dye uptake, surface area and the uptake of Cr(VI) from an aqueous solution. A selected porous condensate polymer was further studied for the technical volume capacity, Cr(VI) uptake from chromate and dichromate solution and the distribution coefficient for Cr(VI) in the presence of high concentration of Cl − and SO 4 2−. The uptake of Cr(VI) by this selected porous condensate polymer was also studied under dynamic conditions using simulated cooling tower blow-down as the influent. For comparison purpose, a conventional gel-type product and a commercially available porous condensate product Duolite S-761, was also studied. Results obtained reveal that the porous condensate polymer, CPPF-G-Cr 5, has good dimensional stability, higher ion-exchange capacity, porosity, surface area and chromium uptake as compared to the conventional gel-type condensate polymer, CPPF-GEL-Cr 0. The porous condensate polymer shows very high selectivity for Cr(VI) even in the presence of high concentration of sulphate and chloride ion but the uptake is susceptible to the pH range and hence the porous condensate polymer removes Cr(VI) from the simulated cooling tower blow-down which usually has pH 4. It removes chromium from a fairly large volume of simulated cooling tower blown-down and gives out the chromium in the form of a concentrated solution of very small volume.