TiO2/ZSM-5m光催化耦合过硫酸盐降解焦化尾水的研究

以具有介孔结构的沸石分子筛ZSM-5m负载纳米TiO2制备出复合型光催化剂,用扫描电镜、比表面及孔径分析仪和X射线衍射对形貌和结构进行表征,通过序批试验考察了TiO2/ZSM-5m/过硫酸盐体系深度降解焦化生化处理出水中残余有机污染物(ROPs)的效果和机理.结果表明,在COD初始平均浓度为352mg/L,TiO2/ ZSM-5m投加量为1.6g/L,pH值为3.0,C(Na2S2O8)为0.8g/L,常温下反应180min,COD出水平均浓度为76.3mg/L,去除率达到78.2 %,在上述优化条件下可达到现行污染物排放标准.ROPs光催化符合Langmuir-Hinshelwood模型,推测具有微介双孔结构的催化剂表面电子易被S2O82-俘获,降低空穴与电子的复合率,促进了·OH 和SO4-·形成,对ROPs的吸附和光降解有较大的强化作用.用GC-MS对处理前后废水中的污染物进行测定以揭示降解与转化规律,发现苯类特征污染物能有效降解,但产生的中间产物明显增多.

Studies on the TiO2/ZSM-5m photocatalyst and combination with persulfate for the degradation of coking wastewater

Composite photocatalyst was prepared with nano TiO2 loaded mesoporous ZSM-5molecular sieve, its morphology and composition were characterized with scanning electron microscope (SEM), specific surface and pore size analyzer and X-ray diffraction, and treatment effects of TiO2/ZSM-5/persulfate system on the advanced degradation of residual organic pollutants (ROPs) from coking biological treated wastewater and mechanisms therein were investigated with batch experiments. The results show that an average COD effluent concentration of 76.3mg/L and percent COD removal of 78.2% can be reached under the initial average COD concentration of 352mg/L, catalyst dosage of 1.6g/L, pH of 3.0, C(Na2S2O8) of 0.8g/L and 180min of reaction at room temperature, which meets existing pollutants discharge standards. The ROPs photocatalysis process can be described with the Langmuir-Hinshelwood model, which indicats that S2O82- captured the electronics easily on the catalyst surface with the micro meso porous structure, reduced the recombination rate of hole and electron, promoted the formation of ·OH and SO4-· and strengthened the ROPs adsorption and photocatalytic degradation significantly. The contaminants before and after the treatment were measured by the determination of degradation and transformation rules with GC-MS, which revealed that the benzenes characteristic pollutants can be degraded efficiently, but the intermediate products increased remarkably.