Development of sulfonate-functionalized hydroxyapatite nanoparticles for cadmium removal from aqueous solutions

Abstract Sulfonate-functionalized hydroxyapatite was successfully synthesized by organo-functionalization using natural phosphate and Benzenedisulfonate molecules. The modified apatites were characterized using multiple techniques, evidencing the effective incorporation of organo-functional groups into the hydroxyapatite matrix. Sulfonated mesoporous hydroxyapatite possesses a large amount of accessible -SO 3 acid groups, which may be versatile adsorbents for the binding of Cd (II) cations. Stability issues of the sulfonated HAp nanocomposites for the specific reactions are addressed. The sulfonated hydroxyapatite nanopowders were evaluated cadmium removal from water. Adsorption tests reveal the efficiency of the hybrid apatites for cadmium removal (q m  = 457 mg g − 1 ). Experimental results fit the Ho-second-order kinetic model for chemical adsorption. Two possible adsorption controlled mechanisms of Cd (II) ions at the apatite surface, complexation and dissolution/precipitation, are proposed.