Synthesis of mesoporous silica-calcium phosphate hybrid nanoparticles and their potential as efficient adsorbent for cadmium ions removal from aqueous solution

Since adsorption and nanomaterials had been respectively found to be the most promising technique and the preferred adsorbents for heavy metal ions removal, in this study, novel mesoporous silica-calcium phosphate (MS-CP) hybrid nanoparticles were synthesized by a facile one-pot method, and subsequently assessed as adsorbent for Cd2+ removal from aqueous solution. MS-CP were characterized by scanning and transmission electron microscopies, etc. The influences of initial Cd2+ concentration, contact time, solution temperature and solution pH on removal efficiency of Cd2+ were investigated in detail. The results revealed that MS-CP were nanospheres of 20 nm and presented a bimodal pore distribution (3.82 nm and 12.40 nm), a high surface area (314.56 m(2)/g) and a large pore volume (1.21 cm(3)/g). The Cd2+ removal experiments demonstrated that MS-CP had a high adsorption capacity due to electrostatic interaction between Cd2+ and silanol groups on MS-CP surface, as well as ion-exchange between Cd2+ and calcium in MS-CP. Additionally, removal efficiency of Cd2+ increased with increasing contact time and solution temperature, while decreased as initial Cd2+ concentration increased. The maximum adsorption capacity of Cd2+ by MS-CP was above 153 mg/L. These results suggested that the as-synthesized MS-CP could be promising adsorbent for Cd2+ removal from aqueous solution. (C) 2018 Published by Elsevier Inc.