Exceptional Sr2+ adsorption performance of amorphous sodium zirconium phosphate

Amorphous sodium zirconium phosphate (NaZrP) with the formula Zr(HPO 4 ) 0.66 (NaPO 4 ) 1.34 ·H 2 O exhibits superior Sr 2+ adsorption capacity (221.85 mg/g) driven by a chemisorption-dominated ion-exchange mechanism. Structural characterization confirms that the amorphous matrix of NaZrP provides accessible active sites (= ZrO 2 POONa/ = ZrO 2 POOH), while kinetic and thermodynamic analyses reveal rapid adsorption kinetics (99% Sr 2+ removal within 5 min) and an endothermic, spontaneous process (ΔG =  − 36.56 kJ/mol). In simulated lake water containing competing ions (Na + /K + /Ca 2+ /Mg 2+ ), NaZrP retains 69.10% Sr 2+ uptake efficiency, demonstrating the practical potential for 90 Sr immobilization across diverse aquatic systems.