Abstract:

Cobalt ferrite and carbon nanotubes (CoFe₂O₄/CNT) composites with different mass ratios were prepared by hydrothermal method, and then used to activate persulfate (PMS) to degrade the azo dye eriochrome black T (EBT). Scanning electron microscope, X-ray diffractometer and X-ray photoelectron spectroscopy were used for sample characterization. The results showed that the introduction of CNT lessened the agglomeration of CoFe₂O₄, and accelerated the electron transfer process on the surface of CoFe₂O₄, and thus improved the catalytic activity. The CoFe₂O₄/CNT of mass ratio 4∶1 showed the highest catalytic activity, and the degradation process of EBT by CoFe₂O₄/CNT-4∶1+PMS was in accordance with the pseudo-first-order kinetics model, with the reaction rate constant 2.02 times higher than that of CoFe₂O₄+PMS system. Under the conditions of CoFe₂O₄/CNT-4∶1 dosage of 0.20g/L, PMS dosage of 0.20g/L, EBT concentration of 100mg/L, pH of 5.8 and the reaction temperature of 25℃, the degradation rate of EBT could reach 99.8% after 60min of reaction and could still reach 67.8% even when CoFe₂O₄/CNT-4∶1 had been reused for three times. Quenching experiments showed that there were four kinds of active substances in the reaction system, that is SO{}_{\mathrm{4}}^{-}·, ·OH, O{}_{\mathrm{2}}^{-}· and ¹O₂, among which ¹O₂ was the dominant one. Valence cycle of Fe²⁺/Fe³⁺ and Co²⁺/Co³⁺ and oxygen species change promoted the formation of active substances.

Key words: cobalt ferrite, carbon nanotubes, activation, catalyst support, degradation

摘要：

采用水热法制备了不同质量比铁酸钴/碳纳米管（CoFe₂O₄/CNT）复合材料，并将其用于活化过一硫酸盐（PMS）降解偶氮染料铬黑T（EBT）。使用扫描电镜、X射线衍射仪、X射线光电子能谱仪等方法进行了表征。结果表明，引入CNT改善了CoFe₂O₄团聚现象，同时CNT加速CoFe₂O₄表面电子转移过程进一步提高了CoFe₂O₄催化活性。质量比为4∶1的CoFe₂O₄/CNT表现出最高催化活性，CoFe₂O₄/CNT-4∶1+PMS降解EBT过程符合准一级动力学模型，其反应速率常数是CoFe₂O₄+PMS体系的2.02倍。单因素条件实验得出在CoFe₂O₄/CNT-4∶1投加量为0.20g/L、PMS投加量为0.20g/L、EBT质量浓度为100mg/L、pH为5.8、反应温度为25℃条件下，反应60min后EBT降解率可达到99.8%。CoFe₂O₄/CNT-4∶1循环使用三次后EBT降解率能达到67.8%。猝灭实验证明反应体系中存在着SO{}_{\mathrm{4}}^{-}·、·OH、O{}_{\mathrm{2}}^{-}·和¹O₂四种活性物质，其中¹O₂是主要活性物质。Fe²⁺/Fe³⁺、Co²⁺/Co³⁺价态循环和氧物种改变促进了活性物质生成。

关键词: 铁酸钴, 碳纳米管, 活化作用, 催化剂载体, 降解