Hou Jifei, Xu Lixia, Han Yuxiang, Tang Yuqiong, Wan Haiqin, Xu Zhaoyi, Zheng Shourong
State Key Laboratory of Pollution Control and Resource Reuse, Jiangsu Key Laboratory of Vehicle Emissions Control, School of the Environment, Nanjing University Nanjing 210093 P. R. China
RSC Adv. 2019 Jan 9;9(2):974-983. doi: 10.1039/c8ra07696k. eCollection 2019 Jan 2.
The reuse, deactivation and regeneration of carbon nanotubes (CNT) and N-doped carbon nanotubes (NCNT) were studied in catalytic peroxymonosulfate (PMS) activation for phenol degradation. The results showed that for catalytic PMS activation, marked deactivation was observed on both CNT and NCNT, resulting in marked variation of the surface functionalities of the catalysts. Catalytic PMS activation led to markedly increased oxygen-containing functionalities and decreased points of zero charge (PZCs) of CNT and NCNT. The catalytic activity of CNT was strongly dependent on the initial PMS concentration but was independent of the initial phenol concentration. Furthermore, the dependency of the CNT activity on the initial PMS concentration closely followed the Langmuir-Hinshelwood model, indicating that the catalytic activation of adsorbed PMS was the rate controlling step. For the used CNT and NCNT, chemical reduction by NaBH or thermal treatment regeneration under inert atmosphere could effectively remove surface O-containing functionalities and enhance PZCs, restoring their catalytic activities; meanwhile, the N-containing functionalities of NCNT decreased with regeneration treatment, resulting in a negative impact on catalyst regeneration. The present findings indicate that surface functionalities are closely correlated with catalyst deactivation and regeneration, playing crucial roles in the catalytic activation of PMS.
研究了碳纳米管（CNT）和氮掺杂碳纳米管（NCNT）在催化过一硫酸盐（PMS）活化降解苯酚过程中的重复使用、失活和再生情况。结果表明，对于催化PMS活化，CNT和NCNT均出现明显失活，导致催化剂表面官能团发生显著变化。催化PMS活化使CNT和NCNT的含氧官能团显著增加，零电荷点（PZC）降低。CNT的催化活性强烈依赖于初始PMS浓度，但与初始苯酚浓度无关。此外，CNT活性对初始PMS浓度的依赖性紧密遵循Langmuir-Hinshelwood模型，表明吸附的PMS的催化活化是速率控制步骤。对于用过的CNT和NCNT，用NaBH进行化学还原或在惰性气氛下进行热处理再生可有效去除表面含氧官能团并提高PZC，恢复其催化活性；同时，NCNT的含氮官能团随再生处理而减少，对催化剂再生产生负面影响。目前的研究结果表明，表面官能团与催化剂失活和再生密切相关，在PMS的催化活化中起关键作用。
