紫外光及日光下天然金红石光催化降解苯酚的研究

Photocatalytic degradation of phenol by natural rutile under UV and sunlight irradiation

研究了山西代县天然金红石在紫外光和日光照射条件下对苯酚的光催化降解性能,考察了光照时间、pH值、苯酚初始浓度以及H2O2添加量对降解过程的影响。在紫外光照射下,酸性条件(pH=3.5)利于光催化降解,中性和碱性条件下降解效率较低;当初始浓度为60mg/L时,降解速率可达1.922mg/(L.h);H2O2作为电子捕获剂可提高苯酚降解速率,最佳投加量为2mL/L。在日光条件下,天然金红石对苯酚表现出良好的降解性能,照射7h后,降解率达87.68%,仅略低于P25型TiO2(99.72%),可在14h内完全降解。根据电子探针和X射线衍射分析结果,认为天然金红石晶格中的V、Fe等杂质可能是提高其可见光响应效果和光催化活性的主要原因。

Phenol is a kind of hardly degradable organic pollutants which widely exist in wastewater and pose great harm to human environment,so the decontamination of phenol is an urgent task in China.In this paper,photocatalytic degradation of phenol was investigated using natural rutile TiO2 powders from Shanxi Province under irradiation of UV and sunlight.The effects of irradiation time,pH value,initial concentration of phenol and dosage of H2O2 on the efficiency of photocatalytic degradation of phenol were studied.The results indicate that natural rutile TiO2,which is commonly thought to have very low catalytic activity,can effectively photodegrade the phenol when it is synergized with H2O2,but the coexistence of light source,charge-trapping agent and photocatalyst is the precondition of photocatalytic reaction.The degradation efficiency of phenol is much higher in acidic condition than in neutral or alkaline conditions,especially when the pH value is 3.5.When the initial concentration is lower,the phenol can be degraded more completely.When the initial concentration is 60 mg/L,the degradation rate is up to 1.922 mg/（L·h）.As an effective charge-trapping agent,H2O2 can inhibit the recombination of electron-hole and facilitate the degradation process,and its favorable dosage is 2 ml/L.It is shown that 87.68% of phenol is degraded under sunlight irradiation by natural rutile in 7 h,which is comparable with the P25 （99.72%）,and phenol can be completely degraded by natural rutile TiO2 in 14 h.The result of nitrogen adsorption shows that the Brunauer-Emmett-Teller （BET） specific surface area of rutile is only 0.469 6 m2/g,which is by far smaller than that of P25 （44 m2/g）.According to EPMA and XRD analysis,it is held that the impurity atoms,such as V and Fe,might induce some response to visible light and greatly enhance the photocatalytic capability of natural rutile.As the most common existing form of TiO2 in nature,rutile can be utilized as photocatalyst to tackle the problem of organic pollution.Compared with synthetic titanium dioxide,it can overcome the shortage of low utilization of solar energy and hence has promising environmental application.