Metal-Free Activation of Sulfite by Benzoquinone-Derived Carbon for Efficient Organic Contaminant Degradation: Identification and Regulation of Active Sites

Abstract

Sulfite [S(IV)]-based advanced oxidation processes (AOPs) driven by carbon materials provide an environmentally friendly, economical route for environmental remediation. However, the active sites and involved radical mechanisms are still controversial due to the complexity of the carbon structure, thus greatly hampering the development of highly efficient systems. Herein, a benzoquinone-derived carbon (BQC)/S(IV) system was developed for organic pollutant degradation in an acidic medium for the first time. The quinone groups and conductivity were confirmed as the key factors for S(IV) activation through cyclic voltammetry, antitheses, specific site masking, and quantitative structure−activity relationship methods. Benefiting from the high content of quinone groups and excellent conductivity, the BQC catalyst exhibited much more effective in activating Na 2 SO 3 for organic pollutant degradation compared to most traditional carbon or even metal catalysts. The chronopotentiometry and in situ Raman results revealed that the formation of C−S(IV)* complexes was the primary step to produce SO 3•− , followed by the production of SO 4•− via a chain reaction, in which the SO 4•− radical was responsible for pollutant degradation. The findings may provide novel insights into reaction mechanisms in S(IV)-AOP systems and pave the way toward highly efficient carbon catalysts to activate S(IV) for the elimination of organic contaminants.

Heterogeneous Activation of Sulfite by a Three-Dimensional Printed Hierarchically Porous Copper Catalyst for the Degradation of Tetracycline Hydrochloride in Water

“…It is widely acknowledged that various ROS, including SO 3 ·– , SO 4 ·– , SO 5 ·– , and ·OH, may be generated in the S­(IV) activation process, in which dissolved oxygen (DO) plays a crucial role in the generation of SO 4 ·– , SO 5 ·– , and ·OH. , In this regard, TC degradation was performed under N 2 - and O 2 -saturated atmospheres to validate the role of the generated reactive species. As shown in Figure a, TC could be hardly degraded under N 2 -saturated conditions, suggesting that SO 3 ·– alone was inefficient for the degradation of TC due to its weak oxidizability E (SO 3 ·– /SO 3 2– = 0.63 V] .…”

“…In recent years, antibiotic contaminants in water have aroused extensive attention due to their adverse biological impact and potential risks to aquatic ecosystems and human health. − Tetracycline hydrochloride (TC), one of the most frequently used antibiotics, has been recognized as an emerging environmental issue because of its remarkable mutagenicity and toxicity. , Conventional biological treatment processes in wastewater treatment plants often fail to completely eliminate TC-related antibiotics, resulting in their significant storage and discharge, thereby exacerbating the global antibiotic resistance crisis and producing toxic byproducts during the transformation process. , …”