硫修饰的多孔Co3O4活化过一硫酸盐降解亚甲基蓝

Porous Co3O4 Modified with Sulfur in Activating Peroxymonosulfate for Degradation of Methylene Blue

摘要:

以Na2S2O3为硫源，采用改进的草酸盐-热解法制备出系列不同硫修饰量的Co3O4多孔催化剂材料（Sx@Co3O4，x=0.25、0.5、0.75、1，x代表硫的添加比例，以Co(NO3)2?6H2O的物质的量为基准计算得到）。以亚甲基蓝（MB）为降解模型，对不同催化剂活化过一硫酸盐（PMS）的性能进行对比研究。考察了工艺参数（催化剂用量、PMS浓度、反应温度、常见阴离子种类）在Sx@Co3O4-PMS体系下对MB降解率的影响，并对催化剂的循环稳定性进行了评价。结果表明，随着硫引入量的增加，Co3O4的催化性能逐渐升高，S1@Co3O4样品表现出最佳的催化性能。硫元素以SO42-的形式键合在Co3O4的表面，Co3O4催化活性的增强是SO42-在其表面修饰引起的比表面积增大、表面氧空位含量增多以及对HSO5-的极化增强三者综合作用的结果。在最优化反应条件下（催化剂用量0.04 g/L、PMS浓度0.6 mmol/L、反应温度25 ℃，反应时间25 min），S1@Co3O4-PMS高级氧化体系对 500 mL 10 mg/L MB溶液的降解率高达98.35%。S1@Co3O4可通过简单的方式回收利用，在连续4次循环使用后其对MB的降解率仍可达68.57%。电子顺磁共振谱（EPR）证实，MB在S1@Co3O4-PMS体系中的降解是自由基（?SO4-、?OH和?O2-）和非自由基（1O2）共同作用的结果。

Abstract:

Using Na2S2O3 as sulfur source, a series of sulfur-modified porous Co3O4 catalysts with different sulfur contents were prepared by an improved oxalate-pyrolysis method (Sx@Co3O4, x=0.25, 0.5, 0.75, 1, where x represented the added ratio of sulfur and was calculated by the amount of Co(NO3)2?6H2O). Their properties for activating peroxymonosulfate (PMS) to degrade methylene blue (MB) were compared and the catalyst with the best catalytic performance was screened out. On this basis, the influences of treatment parameters including catalyst dosage, PMS concentration, reaction temperature and common anion species on MB degradation ratios under Sx@Co3O4-PMS system were investigated. Besides, the cyclic stability of catalyst was evaluated. Results showed that the performance of Co3O4 was boosted with the increase of sulfur content in the range of this study, and S1@Co3O4 exhibited the best catalytic performance. Moreover, it was confirmed that sulfur element was uniformly bonded on the surface of Co3O4 in the form of SO42-. The modification of S increased the specific surface area, oxygen vacancy content of Co3O4 and enhanced the polarization effect for HSO5-, which was considered as a key reason for improving the catalytic activity of Co3O4. Under the optimal reaction conditions: catalyst dosage of 0.04 g/L, PMS concentration of 0.6 mmol/L, reaction temperature of 25 ℃, and reaction time of 25 min, a degradation rate of 98.35% for MB (500 mL 10 mg/L) could be reached in the S1@Co3O4-PMS advanced oxidation system. S1@Co3O4 was recycled in a simple way and the degradation ratio of MB could reach 68.57% after four consecutive cycles. Furthermore, electron paramagnetic resonance spectroscopy (EPR) confirmed that the degradation of MB in S1@Co3O4-PMS system was the result of co-action of free radicals (?SO4-, ?OH and ?O2-) and non-free radicals (1O2).