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Abstract
The photocatalytic activation of sulfites, a common by-product in industries, is a green and sustainable technology with great promise for the treatment of refractory pollutants in water. In this study, N vacancies and N doping were constructed at precise sites in graphitic carbon nitride (CN), following the combination with biochar (BC), synthesizing the BVCN with excellent photocatalytic activation of sulfites under solar light. When the BC was 5wt% (5BVCN), the reaction rate constant of reactive red 120 (RR120) in SO32−-containing solution reached 0.0247 min−1, which was 5.49 times of CN and 15.43 times of 5BVCN in SO32−-free solution. Characterizations and density functional theory (DFT) calculations revealed that N vacancies could trap electrons, while N doping regulated the electronic structure, forming mid-gap states to enhance the separation of carriers. In BVCN, BC rich in pyridinic N serves as both electron transfer channel and electron storage medium, having π-π interaction with structurally regulated CN (VCN). BVCN has narrower band gap and low recombination rate of photogenerated carriers, responds well to visible light, and is easy to firmly associated with SO32−, enhancing the electron transfer from SO32− to BVCN. In the SO32−-containing system, the primary active species were identified as SO3•−, •O2− and h+. Moreover, BVCN exhibited good stability and recyclability. The system shows potential for treating wastewater containing sulfites, realizing resource utilization.Graphical
Highlights
Graphical Abstract1 Introduction With the rapid development of industry (paper, printing, and dyeing, etc.), addressing the resulting environmental pollution has increasingly become a global research hotspot
With the rapid development of industry, addressing the resulting environmental pollution has increasingly become a global research hotspot
3.1 Morphology and structure The X-ray diffraction (XRD) pattern (Fig. 1a) of carbon nitride (CN) showed two distinct peaks at 2θ = 13.1° and 27.6°, corresponding to the (100) and (002) facets attributed to tris-triazine ring in-plane packing and interlayer stacking of aromatic structures, respectively
Summary
1 Introduction With the rapid development of industry (paper, printing, and dyeing, etc.), addressing the resulting environmental pollution has increasingly become a global research hotspot. The combination of sulfite activation with photocatalysis maximizes the advantages of both technologies, enabling efficient pollutant degradation (Chen et al 2019) and is considered a cleaner production strategy. The photocatalysts commonly used for sulfite activation often contain transition metals (Luo et al 2021), resulting in secondary environmental pollution (Tang et al 2022). The development of metal-free, non-toxic and high-efficiency photocatalysts is crucial to advancing the application of photocatalytic activation of sulfite. Biochar (BC) is a promising option due to its abundant and inexpensive raw materials, simple preparation process, and easy graphitization at high temperature (Qi et al 2020), which enables π-π stacking interaction with CN, leading to electron delocalization (Yang et al 2021) and effectively inhibiting the recombination of photogenerated carriers. This study provides a theoretical foundation for implementing the "treating waste with waste" of industrial wastewater by photocatalysis technology
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