Molybdenum-Oxysulfide-Functionalized MgAl-Layered Double HydroxidesA Sorbent for Selenium Oxoanions

• Published in: Inorganic chemistry Vol. 63; no. 24; pp. 10997 - 11005
• Main Authors: Alam, Robiul, Roy, Subrata Chandra, Islam, Taohedul, Feng, Renfei, Zhu, Xianchun, Donley, Carrie L., Islam, Saiful M.
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 17.06.2024
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.4c00307

Effective removal of chemically toxic selenium oxoanions at high-capacity and trace levels from contaminated water remains a challenge in current scientific pursuits. Here, we report the functionalization of the MgAl layered double hydroxide with molybdenum-oxysulfide (MoO2S2) anion, referred to as LDH-MoO2S2, and its potential to sequester SeVIO4 2– and SeIVO3 2– from aqueous solution. LDH-MoO2S2 nanosheets were synthesized by an ion exchange method in solution. Synchrotron X-ray pair distribution function (PDF) and extended X-ray absorption fine structure (EXAFS) revealed an unexpected transformation of the MoO2S2 2– to Mo2O2S6 2– like species during the intercalation process. LDH-MoO2S2 is remarkably efficient in removing SeO4 2– and SeO3 2– ions from the ppm to trace level (≤10 ppb), with distribution constant (K d) ranging from 104 to 105 mL/g. This material showed exceptionally high sorption capacities of 237 and 358 mg/g for SeO4 2– and SeO3 2–, respectively. Furthermore, LDH-MoO2S2 demonstrates substantial affinity and efficiency to remove SeO3 2–/SeO4 2– even in the presence of competitive ions from contaminated water. Hence, the removal of selenium (VI/IV) oxoanions collectively occurs through reductive precipitation and ion exchange mechanisms. This work provides significant insights into the chemical structure of the MoO2S2 anion into LDH and emphasizes its exceptional potential for high-capacity selenium removal and positioning it as a premier sorbent for selenium oxoanions.