Surface-Anchored Zirconium Phosphate via Polydopamine Coating on Ion-Exchange Resin for Rapid, High-Capacity Cs+ Capture

In this study, a novel hybrid adsorbent polydopamine-based nano-zirconium phosphate coated resin (DPZrP) was successfully synthesized, where zirconium phosphate (ZrP) was surface-anchored onto a polystyrene ion-exchange resin (D001) via polydopamine (PDA) mediation. Characterization results indicated that PDA, acting as an interfacial bridge, not only achieved the stable loading of ZrP but also exerted a spatial confinement effect on ZrP through its polymeric cross-linked structure, thereby effectively suppressing the agglomeration of nanoparticles. Compared with pristine D001 and pure ZrP, the hybrid material DPZrP exhibited superior adsorption performance for Cs+. The adsorption capacity of DPZrP for Cs+ reached a theoretical maximum of 921.99 mg/g at 333 K. Adsorption kinetic studies indicated that adsorption equilibrium was reached within 120 min, and the reaction rate constant was 1.55 times that of DZrP. The pH effect experiment showed that DPZrP maintained Cs+ removal rates of 73.4% and 58.1% under strongly acidic (pH = 2) and strongly alkaline (pH = 12) conditions, respectively. When the molar ratio of Ca2+ to Cs+ was as high as 64, the Cs+ removal rate of DPZrP was 19.3% and 30.4% higher than those of DZrP and D001, respectively. Dynamic column experiments revealed that after treating 2000 bed volumes of simulated wastewater ([Cs+]0 = 2.5 mg/L), the Cs+ concentration in the effluent remained below 0.5 μg/L, with breakthrough occurring at 3000 BV. After five consecutive adsorption–desorption cycles, the Cs+ removal rate of DPZrP remained at 88.4%. These studies confirmed the dispersion effect of PDA on ZrP, and the synthesized DPZrP possessed both rapid capture ability and high adsorption capacity for Cs+. Thus, it provides an efficient adsorbent for the safe purification of nuclear waste liquids.