TiO_2/石墨烯应用于Cr(Ⅵ)和苯酚复合体系的光催化研究

Study on photocatalysis for Cr(Ⅵ)and phenol co-existed system using TiO_2/graphene composite

以溶胶凝胶法制备的TiO_2/石墨烯复合材料为光催化剂,对Cr(Ⅵ)和苯酚的复合体系进行光催化实验。考察了污染物浓度、反应气态氛围、光照时间等因素对光催化效果的影响。结果表明,Cr(Ⅵ)和苯酚的去除率均随光照时间的延长而提高。苯酚质量浓度为0～150mg/L时,Cr(Ⅵ)的去除率随着苯酚浓度的增大而升高,当苯酚质量浓度为150mg/L时,Cr(Ⅵ)的最终去除率可达到100.0%;而Cr(Ⅵ)质量浓度为0～50mg/L时,苯酚的光催化氧化去除率随Cr(Ⅵ)浓度的增大先升高后降低,当Cr(Ⅵ)质量浓度为15mg/L时,苯酚的最终去除率最高,为92.2%。综合考虑,空气为最佳气态氛围。Cr(Ⅵ)和苯酚的光催化去除反应均符合一级反应动力学规律。Cr(Ⅵ)和苯酚的光催化协同去除机理为:在光照射下,TiO_2被激发产生光生电子和光生空穴,Cr(Ⅵ)被光生电子还原成Cr(Ⅲ),苯酚主要被光生空穴氧化,光生电子和光生空穴的复合被阻止起到了协同促进作用。

TiO 2/graphene composite fabricated by the method of sol-gel was used to photocatalyze Cr(Ⅵ)and phenol co-existed system.The effects of two pollutants concentrations,reaction atmosphere and reaction time on photocatalytic reaction were investigated.Results showed that removal rates of both Cr(Ⅵ)and phenol increased with reaction time.When phenol mass concentration was 0~150 mg/L,removal rates of Cr(Ⅵ)increased with phenol increasing.The terminal removal rate of Cr(Ⅵ)reached peak(100.0%)when phenol mass concentration was 150 mg/L.When Cr(Ⅵ)mass concentration was 0~50 mg/L,removal rate of phenol increased first and then decreased.The terminal removal rate of phenol reached peak(92.2%)when Cr(Ⅵ)mass concentration was 15 mg/L.Air was the best atmosphere.Both processes of reduction of the Cr(Ⅵ)and oxidation of the phenol were fitted well with the first-order reaction kinetic.The mechanism was explained that Cr(Ⅵ)was reduced to Cr(Ⅲ)by photo-generated electrons,and phenol was mainly oxidized by photo-generated holes under irradiation,which were generated by TiO 2.The synergistic effect was due to photo-generated electrons and photo-generated holes barrier.