SYNTHESIS, CHARACTERIZATION, AND POTENTIAL USE OF A SULFONATED CATION-EXCHANGE RESIN FOR HARD-WATER SOFTENING

This study synthesized and characterized a monofunctional sulfonic cation-exchange resin from sodium p-styrenesulfonate and furfural and evaluated its potential for hard-water softening. The effects of reactant ratio, reaction temperature, and zinc chloride catalyst loading were examined. The selected synthesis condition was a 1:1 molar ratio of sodium p-styrenesulfonate to furfural, 90 °C, and 0.07 mol ZnCl₂ per mole of furfural. Infrared spectroscopy and potentiometric titration supported assignment of strongly acidic –SO₃H functionality, with an apparent pKₕ of 1.8–2.2. The resin showed a static exchange capacity of 4.2–4.5 meq/g by 0.1 N NaOH titration, a total dynamic exchange capacity of 1,480 meq/L, an operating dynamic exchange capacity of 1,200 meq/L, and mechanical durability of 99.0%. Single-cycle desorption recovered approximately 90.5%–92.5% of sorbed Na⁺, Ca²⁺, and Mg²⁺. In regional hard-water samples with initial hardness of 11.0–12.0 meq/L, treatment reduced hardness to 3.0–3.8 meq/L in the H-

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