Th(IV) adsorption by heulandite–high-temperature activated sodium zirconium phosphate from aqueous solution

Abstract

Herein, heulandite–high-temperature activated sodium zirconium phosphate (HEU–HTA-Na-ZrP) composites were first synthesised for adsorbing tetravalent thorium (Th(IV)) from aqueous solution. Furthermore, the HEU–HTA-Na-ZrP pellets (HEU–HTA-Na-ZrP-P) were fabricated for dynamic adsorption. Compared to Na-ZrP, the BET surface area of HEU–HTA-Na-ZrP increased of ∼ 189 m2⋅g−1. In batch adsorption, Th(IV) adsorption increased with increasing pH, C0 values (the initial concentrations) and temperature. The equilibrium Th(IV) adsorption capacities were 314.17 ± 11.27 mg⋅g−1 and 358.89 ± 3.47 mg⋅g−1 for Na-ZrP and HEU–HTA-Na-ZrP, respectively. Thermodynamics, isotherms and kinetics suggested an endothermic, spontaneous, homogeneous and chemisorption process. Characterization verified the adsorption capacities of Th(IV), and the main possible Th(IV) adsorption mechanisms were associated with ion exchange and –OH, Zr–O coordination. Notably, the reusability study indicated that the samples treated with 0.1 mol⋅L−1 H3PO4 solution exhibited excellent reusability. Dynamic adsorption results indicated the structural stability of the composite pellets. τ (min) increased with increasing mass and then decreased, and τ (min) decreased with increasing pH. Both Thomas and Yoon–Nelson models could better describe the Th(IV) dynamic adsorption behaviour. Moreover, HEU–HTA-Na-ZrP-P could separate Th(IV) from simulated and real nuclear wastewater. This work demonstrates that HEU–HTA-Na-ZrP can be applied as an efficient adsorbent for the removal of Th(IV) from Th-containing solutions.