State Key Laboratory of Pollution Control and Resources Reuse, School of Environmental Science & Engineering, Tongji University, Shanghai, 200092, PR China; Shanghai Institute of Pollution Control Ecological Security, Shanghai, 200092, PR China.
Department of Civil Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, PR China.
Chemosphere. 2020 Jan;239:124612. doi: 10.1016/j.chemosphere.2019.124612. Epub 2019 Aug 31.
The degradation of carboxylic acid has been identified as one of the rate-determining steps in the mineralization of organic pollutants by ozonation. In this study, Ce(III)-doped graphitic carbon nitride (Ce-CN) composites with different Ce(III) contents were synthesized and used as catalysts for the ozonation of oxalate. The morphology and structure of the Ce-CN were comprehensively characterized using various techniques such as SEM, XRD, FTIR, and XPS. The results show that the structure of g-CN provided an ideal site for the accommodation of Ce(III) and thus facilitated the formation of surface hydroxyl groups. With 2.5%Ce-CN as a catalyst, the degradation efficiency of oxalate was increased by 47.1% after reaction for 30 min. The decomposition of ozone was accelerated in the presence of Ce-CN. Hydroxyl radicals were recorded by electron spin resonance and identified as the major actives species. Under the catalysis of 2.5%Ce-CN, the production of hydroxyl radicals was increased by 40%. The Ce(III) and surface hydroxyl groups that distributed uniformly on the surface of Ce-CN were speculated as the dual catalytic sites for the complexation of oxalate and activation of ozone, respectively. Ce-CN had a high stability and reutilization capability. It is proposed that a complex was formed between surface Ce(III) and oxalate, and this complex could be more easily attacked by the surrounding ozone and hydroxyl radicals than free oxalate. As oxalate is a typical recalcitrant carboxylic acid, the findings from this study are expected to promote the application of ozonation in the removal of organic pollutants.
已确定羧酸的降解是臭氧化有机污染物矿化的速率决定步骤之一。在这项研究中，合成了具有不同 Ce(III)含量的 Ce(III)掺杂石墨相氮化碳 (Ce-CN) 复合材料，并将其用作草酸盐臭氧化的催化剂。使用 SEM、XRD、FTIR 和 XPS 等多种技术对 Ce-CN 的形貌和结构进行了综合表征。结果表明，g-CN 的结构为 Ce(III)提供了理想的容纳位置，从而促进了表面羟基的形成。以 2.5%Ce-CN 为催化剂，反应 30 min 后草酸盐的降解效率提高了 47.1%。Ce-CN 的存在加速了臭氧的分解。通过电子顺磁共振记录到羟基自由基，并将其鉴定为主要活性物质。在 2.5%Ce-CN 的催化作用下，羟基自由基的生成量增加了 40%。推测均匀分布在 Ce-CN 表面的 Ce(III)和表面羟基基团分别作为草酸盐的络合和臭氧的活化的双催化位点。Ce-CN 具有较高的稳定性和可重复利用性。提出表面 Ce(III)与草酸盐形成配合物，该配合物比游离草酸盐更容易受到周围臭氧和羟基自由基的攻击。由于草酸盐是一种典型的难降解羧酸，因此本研究的结果有望促进臭氧化在去除有机污染物中的应用。
