Functionalization of Zr@FMA with phosphonic acid groups for efficient separation of Th(IV) from aqueous solutions

A phosphonate-functionalized Zr@FMA material was prepared in this work as an adsorbent for the efficient recovery and enrichment of Th(IV) from aqueous solutions. The adsorbent, prepared by functionalizing Zr@FMA with alendronate sodium (ALS), a well-known active bisphosphonate, demonstrates good water stability and a large surface area, making it suitable for the separation and enrichment of Th(IV) in aqueous solutions. A comparison of the adsorption behavior of Th(IV) on Zr@FMA-ALS with the unfunctionalized Zr@FMA reveals that the introduction of phosphonate groups significantly enhances the maximum adsorption capacity and rate of Zr@FMA-ALS. The adsorption data aligns well with the Langmuir isotherm model, suggesting a uniform distribution of Th(IV) on the adsorbent surface in a monolayer coverage. Thermodynamic analysis indicates an endothermic and spontaneous adsorption process. Zr@FMA-ALS also shows excellent selectivity for Th(IV) over other metal ions in mixed solutions. Insights into the adsorption mechanism are provided through SEM, XPS, and FT-IR analyses, indicating that ALS molecules play a crucial role in capturing Th(IV) on the surface of Zr@FMA-ALS.