光催化反应器中光降解重金属Cr(Ⅵ)的研究

Study on photocatalytic reduction of Cr(Ⅵ) in photobioreactor system

在光催化反应器中进行不同酸性条件下Cr(Ⅵ)吸附转化试验。结果表明TiO2对Cr(Ⅵ)吸附在pH值为1.5～2.5时最大,在此期间光照3h后,Cr(Ⅵ)降解转化率可大于95%。在pH值为1.5时,酸性反应阻抑作用可按磷酸>硫酸>盐酸>硝酸依次减弱,因为TiO2表面不同酸根离子对Cr(Ⅵ)离子的竞争吸附能力有差异。在pH值为4.0时,以甲醛、甲酸作为空穴消除剂,二氧化钛吸附性能及反应速率都明显提高,但在同一条件下,甲酸协同作用效果优于甲醛。在磷酸存在时,甲酸、甲醛对反应促进作用不明显。

The effect of acid solution on photocatalytic decompositon of Cr(Ⅵ) was studied in a photobioreactor system.The absorption of chromium on titanium oxide surface reaches a max value at a pH of 1.5-2.5,and the photocatalytic decomposing ratio of Cr(Ⅵ) can be more than 95% after 3 hour's photocatalysis.The acid inhibition ability to reduce chromium can be ordered as follows: phosphoric acid>sulfuric acid>hydrochloric acid>nitric acid,based on the various absorption competence for Cr(Ⅵ) on the titanium oxide surface.It is evident that the rate of the reduction and the capability of absorption of titanium oxide increase in the presence of formaldehyde and formic acid serving as hole scavengers at a pH value of 4.0.Formic acid can accelerate the photocatalytic decomposing ratio more rapidly than formaldehyde in the absence of phosphoric acid at the same condition.