可磁分离回收多孔CoFe_(2)O_(4)的制备及其催化过一硫酸盐降解亚甲基蓝溶液的性能

Preparation of magnetically-separated porous CoFe_(2)O_(4) and its performance in activating PMS for methylene blue degradation

采用草酸盐热解法制得Fe_(2)O_(3),Co_(3)O_(4)以及CoFe_(2)O_(4)三种过渡金属氧化物多孔材料。借助XRD,SEM,BET,VSM和XPS等测试手段对材料的晶体结构、微观形貌、比表面积、磁学性能以及表面化学状态进行分析。选择典型的阳离子型染料亚甲基蓝(MB)作为降解模型,对三种样品催化活化过一硫酸盐(PMS)降解处理模拟印染废水的性能进行评价。结果表明:三种材料均具有分级微/纳米纤维状多孔结构,CoFe_(2)O_(4)因具有最大的比表面积以及Fe,Co元素间的协同效应比Fe_(2)O_(3)和Co_(3)O_(4)表现出更为优异的催化PMS降解MB溶液的性能。通过单因素实验,确定出CoFe_(2)O_(4)/PMS体系降解500 mL浓度为10 mg·L^(-1)MB溶液的优化条件为:PMS用量3 mL(0.1 mol·L^(-1)),催化剂添加量0.07 g,反应时间50 min。在此条件下,MB的降解去除率为89.77%。考察几种阴离子对CoFe_(2)O_(4)/PMS催化氧化体系的影响,发现Cl^(-),PO_(4)^(3-),C_(2)O_(4)^(2-)的存在均对MB的降解有一定的抑制作用。活性物种猝灭实验和电子顺磁共振(EPR)鉴定结果证实,^(1)O_(2)是CoFe_(2)O_(4)/PMS催化氧化体系中产生的最主要活性物种。循环使用实验结果表明,CoFe_(2)O_(4)具有较好的稳定性,且可磁分离回收特性使其可作为活化PMS降解印染废水的候选催化材料。

Three kinds of porous transition metal oxide materials,Fe_(2)O_(3),Co_(3)O_(4) and CoFe_(2)O_(4),were successfully prepared by oxalate-routed pyrolysis method.The crystal structure,morphology,specific surface area,magnetic property and surface chemical state of those materials were characterized by XRD,SEM,BET,VSM and XPS,respectively.The catalytic performance towards PMS activation for degradation of simulated printing and dyeing wastewater were evaluated,taking a typical cationic dye methylene blue(MB)as the degradation model.The results show that all the three materials present hierarchical micro/nano porous fibrous structure,and a much higher PMS activation performance of CoFe_(2)O_(4) is observed comparing with Fe_(2)O_(3) and Co_(3)O_(4) due to its highest specific surface area as well as the concerted catalytic effect between iron and cobalt elements.Through a series of single-factor experiments,the optimal process conditions for MB(10 mg·L^(-1),500 mL)degradation in CoFe_(2)O_(4)/PMS system are determined as follows:PMS dosage of 3 mL(0.1 mol·L^(-1)),catalyst dosage of 0.07 g and reaction time of 50 min.Under this reaction condition,MB removal rate of 89.77%can be achieved.Meanwhile,effect of common anions on CoFe_(2)O_(4)/PMS advanced oxidation system is also investigated.It is found that the presence of Cl^(-),PO_(4)^(3-) and C_(2)O_(4)^(2-) all exhibit inhibition for MB degradation in different degrees.Besides,quenching experiments and electron paramagnetic resonance(EPR)identification results both confirm that ^(1)O_(2) is the primary active specie in CoFe_(2)O_(4)/PMS advanced oxidation system.Furthermore,the recycling experiments indicate that CoFe_(2)O_(4) presents a long-term stability.More importantly,CoFe_(2)O_(4) can be easily separated from liquids after the reaction with an external magnet owing to its good magnetic property.The results demonstrate that CoFe_(2)O_(4) is a promising catalyst candidate in activating PMS to degrade dyeing wastewater.