A heterogenous hybrid thermally regenerable salt sorbent resin is formed from a hybrid precursor resin. The hybrid precursor resin is formed by intimately mixing a dry, solid crosslinked macroporous copolymer with a solution containing a polyunsaturated monomer, a monoethylenically unsaturated monomer containing a haloalkyl group and a polymerization initiator, followed by heating to cause polymerization. The hybrid precursor resin is then treated with a weak base, then subjected to hydrolysis conditions to form, respectively, weak base groups and weak acid groups to produce the hybrid thermally regenerable salt sorbent resin.