Mn3O4/金属有机骨架材料活化过一硫酸盐降解水中难降解有机污染物罗丹明B

锰氧化物是一类环境友好型材料,可以有效活化过一硫酸盐(PMS)降解水中难降解有机污染物.但是锰氧化物在单独使用时容易出现严重的团聚现象,进而降低其对PMS的催化活性,不利于水中污染物的降解.因此,人们通常将锰氧化物负载于多孔的载体材料上.金属有机骨架材料(MOFs)因具有巨大的比表面积和温和的制备条件而广受关注.本文采用温和的溶剂热法首次成功制备了Mn3O4与MOF的复合材料Mn3O4/ZIF-8,并通过X射线衍射、扫描电镜、透射电镜、X射线光电子能谱和红外光谱等手段对其进行了表征,探究了Mn3O4/ZIF-8的形成机理.考察了Mn3O4负载量对Mn3O4/ZIF-8催化性能的影响,以及Mn3O4/ZIF-8投加量、PMS投加量、初始罗丹明B(RhB)浓度和反应温度对RhB去除效果的影响,同时探究了Mn3O4/ZIF-8的重复使用性能,分析了RhB的降解途径、去除机理以及最终的降解副产物.结果表明,边长为50?150 nm的片状Mn3O4均匀分散在粒径为250 nm的六边形ZIF-8的外表面;当Mn3O4负载量为0.5时,所制备的复合材料0.5-Mn/ZIF-120活化PMS对RhB的降解效果最好,反应60 min时RhB降解率可达到99.4%,且Mn的浸出量可以忽略不计.在该体系中,RhB的降解过程符合一级动力学反应方程,其降解速率常数随催化剂和PMS投加量的增加、反应温度的提高和初始RhB浓度的减小而增大.在0.5-Mn/ZIF-120催化剂投加量为0.4 g/L、PMS投加量为0.3 g/L、初始RhB浓度为10 mg/L、初始溶液pH为5.18及室温(23oC)条件下,水中RhB的降解率在40 min时即可达到98%.淬灭实验表明,该体系中HO?起主导作用,而其主要来源于活化PMS所产生的SO4–?.此外,通过简单的二次水冲洗方式对0.5-Mn/ZIF-120催化剂进行回收使用,在连续5次循环使用后仍然可见较高的催化活性和稳定性,RhB的去除率保持在96%以上,且Mn的浸出百分率始终低于5%.

Peroxymonosulfate activation by Mn3O4/metal-organic framework for degradation of refractory aqueous organic pollutant rhodamine B

An environmentally friendly Mn-oxide-supported metal-organic framework (MOF), Mn3O4/ZIF-8, was successfully prepared using a facile solvothermal method, with a formation mechanism pro-posed. The composite was characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron microscopy, and Fourier-transform infrared spectroscopy. After characterization, the MOF was used to activate peroxymonosulfate (PMS) for degradation of the refractory pollutant rhodamine B (RhB) in water. The composite prepared at a 0.5:1 mass ratio of Mn3O4 to ZIF-8 possessed the highest catalytic activity with negligible Mn leach-ing. The maximum RhB degradation of approximately 98% was achieved at 0.4 g/L 0.5-Mn/ZIF-120, 0.3 g/L PMS, and 10 mg/L initial RhB concentration at a reaction temperature of 23 °C. The RhB degradation followed first-order kinetics and was accelerated with increased 0.5-Mn/ZIF-120 and PMS dosages, decreased initial RhB concentration, and increased reaction temperature. Moreover, quenching tests indicated that ?OH was the predominant radical involved in the RhB degradation;the ?OH mainly originated from SO4?? and, hence, PMS. Mn3O4/ZIF-8 also displayed good reusability for RhB degradation in the presence of PMS over five runs, with a RhB degradation efficiency of more than 96% and Mn leaching of less than 5% for each run. Based on these findings, a RhB deg-radation mechanism was proposed.