Enhanced Permanganate Oxidation of Sulfamethoxazole and Removal of Dissolved Organics with Biochar: Formation of Highly Oxidative Manganese Intermediate Species and in Situ Activation of Biochar

Abstract

Sulfamethoxazole (SMX) is a broad-spectrum antibiotic and was largely used in breeding industry. The reaction rate of SMX with KMnO4 is slow, and the adsorption efficiency of biochar for SMX was inferior (less than 11% in 30 min). By adding biochar powder into SMX solution with the addition of permanganate, the oxidation ratio of SMX surged to 97% in 30 min, and over 58% of the total organic carbon (TOC) was simultaneously removed. KMnO4 interacted with biochar and resulted in the formation of highly oxidative intermediate manganese species, which transformed SMX into hydrolysis products, oxygen-transfer products, and self-coupling products. Brunauer–Emmett–Teller (BET) analysis showed that surface area, total pore volume, and micropore volume of biochar increased by 32.1%, 36.4%, and 80.6%, respectively, after reaction process. This in situ activation of biochar with KMnO4 enhanced its adsorption capacity and led to great improvement of TOC removal. Besides KMnO4 oxidation, biochar also enhanced TOC removal in Mn­(III) oxidation (KMnO4+ bisulfite) and ozonization of SMX. Considering that KMnO4 could react with biochar and result in the formation of intermediate manganese species, while biochar can be simultaneously activated and exhibit high capacity for organic adsorption, the combination of biochar with the chemical/advanced oxidation could be a promising process for the removal of environmental pollutants.

Insights into the Electron-Transfer Mechanism of Permanganate Activation by Graphite for Enhanced Oxidation of Sulfamethoxazole

“…There is an emerging insight that carbon materials (e.g., biochar, carbon nanotubes) can donate electrons to accelerate the decomposition of KMnO 4 for producing highly reactive intermediate Mn species. , Thus, electron-rich sites of these carbon materials are the inducers of reactive intermediate Mn species. To discern the role of electron-donating sites of graphite, the reactivity of raw graphite and preoxidized graphite (oxidized by ozone for 2 h) was comparatively evaluated . To better understand the changes in surface properties induced by O 3 oxidation, raw and preoxidized graphite were characterized by conductivity, Nyquist plots, and cyclic voltammetry (Text S5, Table S2, and Figure S2).…”

“…Very recently, intermediate Mn species dominated extremely fast oxidation of organic contaminants by coupling KMnO 4 , and bisulfite has attracted much attention, which initiates a new category of permanganate-based AOPs. , However, the relatively low electron utilization and residual salinity in effluents are the intrinsic shortages for environmental application. To overcome these drawbacks, biochar was employed as an electron sacrificer for promoting KMnO 4 oxidation . However, the unattainable regeneration of reductive sites causes the short-lasting reactivity of biochar.…”

Visualizing the emerging trends of biochar research and applications in 2019: a scientometric analysis and review

“…The catalytic degradation of organic pollutants by biochar is one of the major research topics and trends in 2019, and most research papers were published in the "Chemical Engineering Journal". Among the organic pollutants, antibiotics (especially sulfonamides) received extensive attention as they are increasingly used in the breeding industry, agriculture, and human medicine (Klein et al 2018;Tian et al 2019). Modified biochar was effective in activating persulfate/H 2 O 2 for organic pollutants degradation through radical (SO 4 •− , HO•, O 2 •− ) oxidation (Table 2).…”

“…Non-radical 1 O 2 oxidation of antibiotics was also proposed, which provided a new, safe and efficient oxidation pathway for organic pollutants (Yin et al 2019;Zou et al 2019). Besides, biochar treated with KMnO 4 could also enhance the degradation of sulfamethoxazole mediated by highly oxidative intermediate manganese species, which provides a new perspective for organic pollutants removal by biochar with the chemical/ advanced oxidation (Tian et al 2019). The possible degradation mechanisms of organic pollutants mediated by biochar are summarized in Fig.…”

Degradation of Diclofenac in Urine by Electro-Permanganate Process Driven by Microbial Fuel Cells

“…Ultraviolet (UV) irradiation, biochar, and some reagents (e.g., bisulfite and humic acid (HA)) have been successfully applied to activate PM. The formed reactive species can accelerate the oxidation rate of PM [20][21][22][23]. Our previous work also proved that PM could be reduced to RMnS in an electric field (E-PM), and that the generated RMnS was faster than PM in the oxidation of DCF [17,24,25].…”