Outstanding performance of ZnS/TiO2 for the urgent disposal of liquid mercury leakage indoors: Novel support effect, reaction mechanism and kinetics

Highlights: • TiO₂ shows a novel support effect on ZnS for Hg⁰ capture. • The bond strength of Zn-S in S-Zn-O is significantly weaker than that in S-Zn-S as Zn²⁺ preferred to O²⁻ than S²⁻. • The loading of ZnO significantly improved the Hg⁰ adsorption ability of TiO₂-S. • The amount of S²⁻ on TiO₂-S that can bond with physically adsorbed Hg⁰ significantly increases after ZnO loading. • ZnS/TiO₂ offers a significant advantage in the urgent disposal of liquid Hg⁰ leakage indoors as a co-benefit of air purifiers. Effectively weakening the bond strength of Zn-S in S-Zn-S on ZnS is of great significance to the improvement of its performance for the urgent disposal of liquid Hg⁰ leakage indoors. In this work, ZnS was loaded on three common supports (i.e., TiO₂, SiO₂, and Al₂O₃) to further improve its performance for capturing high concentrations of Hg⁰ indoors. After being loaded on TiO₂, the S-Zn-O bond was present on ZnS, and the bond strength of Zn-S in S-Zn-O was significantly weaker than that in S-Zn-S because Zn²⁺ preferred to O²⁻ than S²⁻. Hence, physically adsorbed Hg⁰ was much easier to bond with S in S-Zn-O than that in S-Zn-S to form HgS. Therefore, TiO₂ showed a novel support effect on ZnS for Hg⁰ capture, and the Hg⁰ capture performance of ZnS/TiO₂ was greatly better than those of ZnS, ZnS/SiO₂, and ZnS/Al₂O₃. Moreover, the promotion mechanism of ZnO loading on Hg⁰ adsorption onto TiO₂-S was discovered after comparing the Hg⁰ adsorption kinetic parameters of TiO₂-S and ZnS/TiO₂. The promotion of ZnO loading was primarily related to the notable increase in the content of S²⁻ that can bond with physically adsorbed Hg⁰, which predominantly resulted from the strong interaction of ZnO/TiO₂ with H₂S.