Effect of HCO3- concentration in groundwater on TiO2 photocatalytic water purification
Effect of HCO3- concentration in groundwater on TiO2 photocatalytic water purification
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DOI：
10.1016/j.apcatb.2018.10.022
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发表时间：
2019-03-01
影响因子：
22.1
通讯作者：
Yang, Yingnan
中科院分区：
文献类型：
--
作者：
Negishi, Nobuaki;Miyazaki, Yukari;Yang, Yingnan
评价地下水系统主要组分对光催化活性的影响是开发商品化光催化净水系统的关键。在本工作中，我们探讨了碳酸氢根离子(HCO3-)对二氧化钛陶瓷光催化剂光催化活性的影响。两个品牌的矿泉水，依云和Contrex，含有高浓度的碱土金属离子镁和钙，被用作地下水的模型。以甲酸降解率作为光催化活性的指标。还观察了HCO3-的降解速率以及HCO3-反离子的种类和浓度随光催化反应的进展而发生的变化。在完成15个循环的8h的光催化反应后(总运行时间120h)，利用X射线衍射分析、拉曼光谱、扫描电子显微镜和能量色散X射线光谱对光催化剂的表面和形成的沉淀物进行了分析。我们发现，无论反离子的类型如何，随着HCO3-浓度的增加，光催化活性都会降低。此外，尽管随着实验循环的进行，光催化剂表面上的沉淀物(我们确定为CaCO3)的积累增加，但光催化活性保持不变。当Ca~(2+)为反离子时，光催化降低了甲酸和HCO3-的浓度，而其他金属离子Na~+、K~+和Mg~(2+)的存在对甲酸和HCO3-的浓度没有影响。结果表明，当Ca~(2+)为反离子时，碳酸氢根离子参与了光催化反应，降低了甲酸的光催化降解率，生成了CaCO_3沉淀。
Evaluation of the effects of major components of groundwater systems on photocatalytic activity is essential for the development of commercial photocatalytic water purification systems. In this work, we have probed the effects of bicarbonate ion (HCO3-) on the photocatalytic activity of a TiO2 ceramic photocatalyst. Two brands of mineral water, Evian and Contrex, which contain high concentrations of alkaline earth metal ions Mg2+ and Ca2+, were used as models for groundwater. The degradation rate of formic acid was used as an index of photocatalytic activity. The rate of HCO3- degradation and changes in the type and concentration of the HCO3- counterion with the progress of photocatalytic reaction were also observed. After the completion of 15 cycles of 8 h of photocatalytic reaction (total run time 120 h), the surface of the photocatalyst and precipitates formed on it were analyzed by means of X-ray diffraction analysis, Raman spectrometry, scanning electron microscopy, and energy dispersive X-ray spectrometry. We found that the photocatalytic activity was reduced with increasing HCO3- concentration, irrespective of the type of counterion present. In addition, photocatalytic activity remained unchanged despite an increase in accumulation of the precipitate, which we identified as CaCO3, on the photocatalyst surface with the progress of experimental cycles. We also observed that the concentration of formic acid and HCO3- were decreased with photocatalysis when Ca2+ was a counterion, however, no effect in presence of other metal ions, Na+, K+ or Mg2+, was observed. These results show that bicarbonate ion was involved in the photocatalytic reaction when Ca2+ was the counterion, and as a result, the photocatalytic degradation rate of formic acid was decreased and CaCO3 precipitate was formed.