Elimination of hydrogen sulfide adsorbed on Cu(II)-modified hydroxyapatite by warm water

Elimination behavior of hydrogen sulfide (H2S) molecules adsorbed on Cu(II)-supported hydroxyapatite (Cu-HAp) using warmed ultrapure water was investigated, and H2S adsorption ability of Cu-HAp before and after exposure to initial H2S gas and the subsequent water treatment was compared. Cu-HAp quickly and markedly adsorbed H2S and its color changed from light blue to dark brown, suggesting that sulfuric component was chemically adsorbed on the surface of Cu-HAp and that it was present as a Cu(II) salt. After the water treatment of Cu-HAp at 333 K after exposure to H2S, the solid phase kept its original crystalline structure and no sulfuric component was detected. The color of the sample gradually changed and turned back to the almost original one after immersion in water for 4 weeks. In addition, Cu-HAp treated in water recovered H2S adsorption ability up to 76 % compared to the original Cu-HAp. Solid residue obtained by evaporation of the treated solution was mainly composed of hydrated calcium sulfate, while any Cu(II) salt was not detected. It suggests that sulfides adsorbed on Cu-HAp was oxidized and eluted into water, and that Cu(II) remained on the surface of the adsorbent. Consequently, Cu-HAp is expected to be a reusable adsorbent against gaseous H2S.