A composite adsorbent of ZnS nanoclusters grown in zeolite NaA synthesized from fly ash with a high mercury ion removal efficiency in solution

Yu Li; Liyun Yang; Xinxue Li; Takahiro Miki; Tetsuya Nagasaka

doi:10.1016/j.jhazmat.2021.125044

A composite adsorbent of ZnS nanoclusters grown in zeolite NaA synthesized from fly ash with a high mercury ion removal efficiency in solution

J Hazard Mater. 2021 Jun 5:411:125044. doi: 10.1016/j.jhazmat.2021.125044. Epub 2021 Jan 6.

Authors

Yu Li¹, Liyun Yang², Xinxue Li³, Takahiro Miki⁴, Tetsuya Nagasaka⁴

Affiliations

¹ School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, 100083, PR China; School of Chemistry and Biological Engineering, University of Science and Technology Beijing, 100083, PR China.
² School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, 100083, PR China. Electronic address: Yangliyun@ustb.edu.cn.
³ School of Chemistry and Biological Engineering, University of Science and Technology Beijing, 100083, PR China.
⁴ Department of Metallurgy, Graduate School of Engineering, Tohoku University, 02 Aoba-yama, Sendai 980-8579, Japan.

PMID: 33429309
DOI: 10.1016/j.jhazmat.2021.125044

Abstract

In this study, the nanocomposite adsorbent (ZnS-zeolite NaA) was prepared by a simple ion-exchange method, which modified the zeolite NaA synthesized from fly ash. The removal efficiency, adsorption mechanism of mercury ions by ZnS-zeolite NaA and release of zinc ion into aqueous solution during the adsorption process were determined. The results showed that ZnS nanoclusters were introduced the supercages of zeolite by ion exchange to synthesize the ZnS-zeolite NaA with high removal capacity for Hg²⁺ in the initial pH 2-7 of solution. Determination of the adsorption kinetics and thermodynamic parameters, in combination with X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy analyses, revealed that the Hg²⁺ adsorption by ZnS-zeolite NaA was Hg²⁺ complexed and ion exchanged with ZnS in the ZnS-zeolite NaA to form stable HgS, and then, the released Zn²⁺ was adsorbed by the zeolite, preventing Zn²⁺ pollution. The Hg²⁺ removal rate was greater than 99.90% with the coexistence of either Zn²⁺ or Cu²⁺, Cd²⁺ and Pb²⁺. After five repetitions, the Hg²⁺ removal rate by the ZnS-zeolite NaA was only slightly decreased by 2%. Therefore, ZnS-zeolite NaA synthesized using fly ash has potential for broad application as a Hg²⁺ adsorbent.

Keywords: Fly ash; Mercury ion; Nanocomposite adsorbent; Zeolite NaA; Zinc ion pollution.