铕掺杂对Co_(3)O_(4)活化过一硫酸盐降解亚甲基蓝性能的增强

Co_(3)O_(4) Doped with Europium as a Performance Enhanced Heterogeneous Catalyst to Activate Peroxymonosulfate for Degradation of Methylene Blue

以Co(NO_(3))_(2)和Eu(NO_(3))3为原料,采用草酸盐-热分解法制得了系列不同Co/Eu比例(n_(Co)/n_(Eu))的多孔双金属复合氧化物催化剂,并对其活化过一硫酸盐(PMS)降解亚甲基蓝(MB)的性能进行对比评价。结果表明,按n_(Co)/n_(Eu)=9制得的材料(Co_(9)Eu_(1))具有最为优异的活化PMS降解MB的性能。在温度为25℃、催化剂用量和PMS浓度分别为0.10 g·L^(-1)和0.6 mmol·L^(-1)的反应条件下,Co_(9)Eu_(1)/PMS体系对MB的降解率可达86.66%,而纯Co_(3)O_(4)催化下的MB降解率仅为52.62%。Co_(9)Eu_(1)出色的催化性能是由于Eu^(3+)的缺电子特性增强了对吸附于催化剂表面PMS的极化而使其更易被主催化成分Co_(3)O_(4)活化。体系中阴离子C_(2)O_(4)^(2-)和HCO_(3)-的存在对Co_(9)Eu_(1)/PMS氧化降解MB的性能具有明显抑制作用。猝灭实验和电子顺磁共振谱(EPR)证实Co_(9)Eu_(1)/PMS体系中同时存在SO_(4)^(-)·、·OH和·O_(2)-三种自由基型活性物种以及1O_(2)非自由基型活性物种,其中SO_(4)^(-)·对MB的氧化降解起关键作用。Co_(9)Eu_(1)具有良好的稳定性,在连续4次循环使用中其催化性能未见明显变化。

Employing Co(NO_(3))_(2) and Eu(NO_(3))_(3) as raw materials,a series of porous Co/Eu bimetallic-oxide catalysts were synthesized through an oxalate-pyrolysis method,and their catalytic performances in activating peroxymonosulfate(PMS)for degradation of methylene blue(MB)were evaluated.The results showed that the samplewith a Co/Eu molar ratio(n_(Co)/n_(Eu))of 9(Co_(9)Eu_(1))exhibited the most excellent catalytic property towards PMS decomposition for MB removal.The degradation ratio of MB was 86.66%in the system of Co_(9)Eu_(1)/PMS,while it was only 52.62%for the counterpart,under the reaction conditions:catalyst addition of 0.10 g·L^(-1),PMS concentration of 0.6 mmol·L^(-1),and a reaction temperature of 25℃.The outstanding catalytic performance of Co_(9)Eu_(1) is attributed to the electrondeficient property of Eu^(3+),which can enhance the polarization of PMS adsorbed on the surface of the catalyst and then make PMS easier to be activated by the primary catalytic component of Co_(3)O_(4).Meanwhile,it is found that both C_(2)O_(4)^(2-) and HCO_(3)-anions have obvious inhibitory effects on the degradation efficiency of MB in the Co_(9)Eu_(1)/PMS reaction system.In addition,quenching experiments and electron paramagnetic resonance spectroscopies(EPR)identify that reactive oxygen species(SO_(4)^(-)·,·OH and·O_(2)-) and non-radical reactive oxygen species(1O_(2)) both exist in the reaction system.Among them,SO_(4)^(-)·plays a key role in MB oxidative degradation process.Furthermore,no significant changes in catalytic performance in four consecutive cycles was observed.