Persistent free radicals in biochar enhance superoxide-mediated Fe(III)/Fe (II) cycling and the efficacy of CaO2 Fenton-like treatment

JOURNAL OF HAZARDOUS MATERIALS

卷:421

Article

Zhang, Shuqi¹  Wei, Yan¹  Metz, Jordin²  He, Shengbing¹  Alvarez, Pedro J. J.²  Long, Mingce¹ 

[1] Shanghai Jiao Tong Univ, Sch Environm Sci & Engn, Key Lab Thin Film & Microfabricat Technol, Minist Educ, 800 Dongchuan Rd, Shanghai 200240, Peoples R China

[2] Rice Univ, Houston, TX 77005 USA

关键词: Calcium peroxide;    Superoxide;    Fenton-like reactions;    Biochar;    Persistent free radicals;   

DOI  :  10.1016/j.jhazmat.2021.126805

来源: Elsevier

【 摘 要 】

Superoxide radicals (O-2(center dot-)) produced by the reaction of Fe(III) with H2O2 can regenerate Fe(II) in Fenton-like reactions, and conditions that facilitate this function enhance Fenton treatment. Here, we developed an efficient Fenton-like system by using calcium peroxide/biochar (CaO2/BC) composites as oxidants and tartaric acidchelated Fe(III) as catalysts, and tested it for enhanced O-2(center dot) (-)-based Fe(II) regeneration and faster sulfamethoxazole (SMX) degradation. SMX degradation rates and peroxide utilization efficiencies were significantly higher with CaO2/BC than those with CaO2 or H2O2 lacking BC. The CaO2/BC system showed superior activity to reduce Fe(III), while kinetic analyses using chloroform as a O-2(center dot)-probe inferred that the O(2)(center dot-)generation rate by CaO2/BC was one-half of that by CaO2. Apparently, O-2(center dot-) is utilized more efficiently in this system to regenerate Fe(II) and enhance SMX degradation. Additionally, a positive correlation between SMX degradation rate constants and EPR signal intensities of biochar-derived persistent free radicals (PFRs) in CaO2/BC was obtained. We postulate that PFRs enhanced Fe(III) reduction by shuttling electrons donated by O-2(center dot-). This represents a new strategy to augment the ability of superoxide to accelerate Fe(III)/Fe(II) cycling for increased hydroxyl radical production and organic pollutant removal in Fenton-like reactions.

【 授权许可】

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