Stoichiometric Carbocatalysis via Epoxide-Like C−S−O Configuration on Sulfur-Doped Biochar for Environmental Remediation

Document Type

Article

Publication Date

4-15-2022

Publication Title

Journal of Hazardous Materials

Volume

428

Abstract

Heteroatom doping is a promising technique to enhance biochar for effective environmental remediation. However, development of electroactive heteroatom-doped biochars, e.g., sulfur-doped biochar, has been hindered due to complex nature of non-stoichiometric biomass-derived carbon and changeable electrochemical state of dopants. Herein, we produced a series of wood waste-derived biochars with customized levels of minerals and redox-active moieties, aiming to unravel the crucial factors for sulfur doping. Calcium (Ca) in biochar was found to preferentially coordinate with sulfur to form inactive inorganic sulfur minerals (i.e., CaSO4 and CaS) with inferior catalytic reactivity. After diminishing the inherent Ca minerals beforehand, we could introduce surface phenoxyl-type radicals (C−O•) and vacancy defects on the biochar to develop an electrophilic C−S−O bonding configuration, which guaranteed a high affinity towards peroxymonosulfate (PMS, 2.08 mM g−1, 30 min) and efficient removal of bisphenol A (BPA, 91.1%, 30 min). Scavenging experiments and in-situ Raman analyses indicated that the epoxide-like C−S−O structure induced nucleophilic addition of PMS to generate surface-bound singlet oxygen (1O2, major) and hydroxyl radicals (•OH, minor) through a preservative and stoichiometric interfacial reaction. Overall, the proposed approach overcomes the major hurdles in science-informed fabrication of sulfur-doped biochar and advances its development for environmental remediation.

Keywords

Biomass valorization; Engineered biochar catalyst; Heteroatom doping; Persulfate activation; Sustainable waste management; Wastewater treatment

Disciplines

Pharmacology, Toxicology and Environmental Health

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