不同形貌氧化钴活化过一硫酸盐降解硝基酚

Degradation of Nitrophenols in Wastewater by Peroxymonosulfate Activated by Cobalt Oxide with Different Morphologies

通过控制形貌制备具有高活性晶面的金属氧化物可提高硝基酚的降解效果,以硝酸钴和乙酸钴为原料,制备了八面体、立方块和棒状Co3O4,通过X射线衍射(XRD)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)对催化剂进行表征,表明合成的Co3O4粒径均匀、纯度较高。以3种不同形貌的Co3O4为催化剂,在pH值为8.0条件下活化过一硫酸盐(PMS)降解不同种类的硝基酚,采用高效液相色谱和总有机碳分析仪测定反应前后硝基酚和总有机碳含量(TOC)变化。3种Co3O4在Co3O4/PMS体系降解硝基酚时表现出不同的催化活性:棒状Co3O4>立方块Co3O4>八面体Co3O4,并且对不同硝基酚的降解效率存在显著的差异性。3种Co3O4在pH值为8.0下活化PMS所析出的Co^2+含量较低,且均表现出良好的循环利用性。自由基淬灭实验和电子自旋共振(ESR)测试表明Co3O4/PMS体系降解硝基酚是通过自由基和非自由基机制共同协作完成的,起作用的活性氧化物种主要为羟基自由基(·OH)、硫酸根自由基(SO·^-4)和单线态氧(^1O2)。

The degradation effect of nitrophenol can be improved by controlling the morphology of metal oxides with highly active crystal planes.The octahedral,cubic and rod-like Co3 O4 were prepared by using cobalt nitrate and cobalt acetate.The synthesized compounds were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM)and transmission electron microscope(TEM),and results show that the prepared Co3 O4 have uniform size and high purity.Peroxymonosulfate(PMS)was activated by Co3 O4 with different morphologies to degrade nitrophenols at pH 8.0.High performance liquid chromatography(HPLC)and total organic carbon(TOC)analyzer were used to determine the changes of nitrophenols and total organic carbon content before and after the reaction.The reaction rate and nitrophenols degradation in the Co3 O4/PMS system indicate that the activity of catalysts shows an order of rodlike Co3 O4>cubic Co3 O4>octahedral Co3 O4,and the position of-NO2 also affects the degradation of nitrophenol.The trace Co^2+leached from Co3 O4 has no significant effect at pH 8.0,and all of the Co3 O4 showed good reusability.Quenching experiments and electron spin resonance(ESR)spectra show that the degradation of nitrophenol in Co3 O4/PMS system is a pathway where hydroxyl radical(·OH),sulfate radical(SO·^-4)and singlet oxygen(^1 O2)play main roles.