Sun K, Liu Q, Li S, Qi Y, Si Y. MnO
2 nanozyme-driven polymerization and decomposition mechanisms of 17β-estradiol: Influence of humic acid.
J Hazard Mater 2020;
393:122393. [PMID:
32120219 DOI:
10.1016/j.jhazmat.2020.122393]
[Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Revised: 02/22/2020] [Accepted: 02/22/2020] [Indexed: 06/10/2023]
Abstract
Nanozymes, which display the bifunctional properties of nanomaterials and natural enzymes, are useful tools for environmental remediation. In this research, nano-MnO2 was selected for its intrinsic enzyme-like activity to remove 17β-estradiol (E2). Results indicated that nano-MnO2 exhibited laccase-like activity (7.22 U·mg-1) and removed 97.3 % of E2 at pH 6. Humic acid (HA) impeded E2 removal (only 72.4 %) by competing with E2 for the catalytic sites of the MnO2 nanozyme surface, and there was a good linear correlation between the kinetic constants and HA concentrations (R2 = 0.9489). Notably, the phenolic -OH of E2 interacted with HA to yield various polymeric products via radical-driven covalent coupling, resulting in ablation of phenolic -OH but increase of ether groups in the polymeric structure. Intermediate products, including estrone, E2 homo-/hetero-oligomers, E2 hydroxylated and quinone-like products, as well as aromatic ring-opening species, were identified. Interestingly, HA hindered the extent of E2 oxidation, homo-coupling, and decomposition but accelerated E2 and HA hetero-coupling. A reasonable catalytic pathway of E2 and HA involving MnO2 nanozyme was proposed. These findings provide novel insights into the influence of HA on MnO2 nanozyme-driven E2 radical polymerization and decomposition, consequently favoring the ecological water restoration and the global carbon cycle.
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