N原子杂化石墨烯高效活化过一硫酸盐降解RBk5染料废水

过硫酸盐高级氧化技术使用过程中,活化剂的大量流失与其环境二次危害是影响该技术应用的主要限制因素.针对这一问题本研究采用改进的Hummers法结合水热法制备环境友好型的N原子掺杂石墨烯作为催化剂,活化过一硫酸盐(PMS)产生硫酸根自由基(SO4-·)和羟基自由基(·OH)降解活性黑5(RBk5)染料.利用傅立叶红外光谱,X-射线光电子能谱,拉曼光谱和透射电子显微镜对N原子掺杂石墨烯进行表征.对催化剂催化性能进行研究,考察了初始p H、催化剂投加量和PMS投加量等因素对降解过程的影响.结果表明,N元素掺杂能够有效提升石墨烯材料的PMS催化活性,且活性受N掺杂比例影响较大;废水的初始p H对降解效率无明显影响.催化剂投加量为1. 5 g·L-1,PMS投加量为0. 3 g·L-1的条件下,反应25min后RBk5染料废水的降解率可达到99%以上,反应过程符合一级反应动力学.自由基猝灭实验显示,N掺杂石墨烯/PMS体系降解RBk5为表面反应,SO4-·和·OH为降解RBk5的主要自由基.循环实验证明催化剂稳定性能良好.

Degradation of RBk5 with Peroxymonosulfate Efficiently Activated by N-Doped Graphene

The large loss of catalysts and secondary pollution problems are bottlenecks for the utilization of persulfate advanced oxidation processes. Thus, a modified Hummers method combined with a hydrothermal method was used to prepare N-doped graphene as a catalyst for peroxymonosulfate (PMS) activation. The produced sulfate radical (SO₄^-·) and hydroxyl radical (·OH) were able to degrade RBk5. N-doped graphene was characterized by Fourier transform infrared, X-ray photoelectron spectroscopy, Raman spectroscopy, and transmission electron microscopy. The influences of vital parameters (i. e., initial pH, catalyst dosage, and PMS dosage) on RBk5 removal were investigated systematically to examine the catalytic performance. The results showed that the N element doping can effectively improve the catalytic activity of graphene, and the activity is greatly affected by the N doping ratio. The initial pH of the wastewater had no significant effect on the degradation efficiency. Under the condition of 1.5 g·L^-1 catalyst dosage and 0.3 g·L^-1 PMS dosage, the removal rate of RBk5 dye reached 99% after 25 min of reaction. The reaction process accorded with first-order reaction kinetics. Radical quenching experiments were done and indicated that the degradation of RBk5 in N-doped graphene/PMS systems was a surface reaction, and SO₄^-· and ·OH were identified as the main radical species. The catalyst exhibited excellent stability over five successive degradation cycles.