Unique and outstanding cadmium sequestration by polystyrene-supported nanosized zirconium hydroxides: a case study

Abstract

Water pollution by heavy metals remains a serious environmental and health issue. Herein, a new hybrid adsorbent was prepared for selective Cd(II) sequestration by immobilizing nanosized zirconium hydroxides (HZO) onto a macroporous cation exchanger. The positively charged SO₃⁻H group within the host matrix can accelerate the target Cd(II) ions diffusion and enrichment, combining with the strong adsorption by HZO nanoparticles. Solution pH influence proves that Cd(II) can be efficiently eliminated by HZO-PS in a wide pH range of 2.5–7.0 with negligible Zr(IV) releases. Both HZO-PS and PS exhibit similar and fast kinetic behaviors by approaching sorption equilibrium within 150 min. Such results can be ascribed to the unique surface-charged groups for accelerating Cd(II) diffusion. Moreover, HZO-PS also exhibits favorable sorption selectivity in the presence of common cations at high levels. Fixed-bed column experiments further demonstrate its efficient applicability with the treated capacity of 750 bed volume (BV) per run and the exhausted HZO-PS can be readily regenerated using binary HNO₃ and Ca(NO₃)₂ mixtures for repeated use. All the results suggest that the hybrid material HZO-PS is a promising adsorbent for cadmium retention in water.