Mesoporous nanocrystalline sulfonated hydroxyapatites enhance heavy metal removal and antimicrobial activity

Abstract

Abstract Heavy metal ions are major contaminants of water resources. Their high solubility in water causes serious health problems as they can be adsorbed by living species and therefore, accumulate in humans. In this study, two approaches are explored: the first is based on the manufacture of mesoporous nanocristalline sulfonated hydroxyapatite. The influence of sulfonate ligands and the structure and surface chemistry of the materials are discussed. The second approach is based on the recovery of sulfonated hydroxyapatites used as adsorbents for heavy metal removal from water, which are studied for their antibacterial properties. The single and multi-component adsorption of Pb2+, Zn2+ and Cd2+ ions is enhanced in apatite enriched with sulfonate ligands, with remarkable selectivity and efficiency. The calculated maximal single sorption capacities qe were in the order Zn2+(4.21 mmol g-1) > Cd2+(3.15 mmol g-1) > Pb2+(2.45 mmol g-1). Competition between metal ions decreases the adsorption capacity of each metal ion. Results show that Zn2+ and Cd2+ are preferentially adsorbed by sulfonated-HAp. The sulfonated hydroxyapatites are tested for their antimicrobial activity against three bacterial strains: Escherichia coli and Pseudomonas aeruginosa as Gram-negative model and Staphylococcus aureus as Gram-positive model bacteria. Results evidence the 1,3-Benzenedisulfonate-functionalized hydroxyapatite antimicrobial activity against G-positive and G-negative bacteria. The mechanisms responsible for metal-ion adsorption and antibacterial activity are discussed.