复合催化剂光催化降解DNT废水及其降解机理

为探索负载型多金属氧酸盐类复合催化剂光催化降解炸药废水的催化活性及降解机理,采用溶胶-凝胶-溶剂热的路径,制备了3种负载型多金属氧酸盐类复合催化剂H_3PW_(12)O_(40)/TiO_2、H_3PW_(12)O_(40)/TiO_2(P123)和SO_4~(2-)-H_3PW_(12)O_(40)/TiO_2(P123)。以炸药废水中典型有机污染物二硝基甲苯(DNT)为目标化合物,考察了所制备的复合催化剂在光催化降解DNT废水方面的催化活性,并对不同催化剂之间光催化活性的差异进行了合理的解释,分析了催化剂的结构与其光催化性能之间的关系。采用气相色谱-质谱联用仪(GC-MS)对废水中反应物和产物的种类进行了鉴定和分析,对光催化氧化法降解DNT废水的降解机理和矿化程度进行了研究。结果表明,以SO_4~(2-)-H_3PW_(12)O_(40)/TiO_2(P123)为催化剂,光照4h后,DNT废水降解率达98.73%。光催化降解DNT废水过程中,发生了甲基氧化、脱硝基、脱羧基等反应,降解过程中的中间产物主要包括对硝基苯甲酸、间硝基苯甲酸、1,3-二硝基苯、2,4-二叔丁基苯酚、2,4-二硝基苯甲醛。光催化降解4h后,除极少量3,4-DNT外,其余硝基苯类化合物均完全降解。

Photocatalytic Degradation of DNT Wastewater by Composite Catalyst and Its Degradation Mechanism

To explore the catalytic activity and degradation mechanism of the photocatalytic degradation of explosive wastewater by supported polyoxometalate composite catalysts, three kinds of supported polyoxometalate composite catalysts, H3PW12O40/TiO2、H3PW12O40/TiO2(P123)and SO2-4-H3PW12O40/TiO2(P123),were prepared by the sol-gel-solvothermal route.Taking the typical organic pollutant-dinitrotoluene (DNT) in explosive wastewater as traget compound, the photocatalytic activities of the prepared catalysts in the photocatalytic degradation of DNT wastewater were investigated.The reasonable explanation for the photocatalytic activity difference between different catalysts was performed.The relationship between structure and photocatalytic properties of the catalysts was analyzed.The species of reactants and products in wastewater were identified and analyzed by gas chromatography-mass spectrometry (GC-MS) instruments.The photocatalytic degradation mechanism and mineralization degree of DNT wastewaters were studied by photocatalytic oxidation method.The results show that the degradation rate of DNT in wastewater after 4h irradiation is 98.73% when SO2-4-H3PW12O40/TiO2(P123)is used as catalyst.The reaction of methyl oxidation, nitro removal and decarboxylation occurs in the process of photocatalytic degradation of DNT wastewater.Intermediate products of degradation mainly include p-nitrobenzoic acid, m-nitrobenzoic acid, 1,3-dinitrobenzene, 2,4-di-tert-butylphenol and 2,4-dinitrobenzaldehyde.After 4h degradation, the nitrobenzene compounds were degraded completely, except for a small amount of 3,4-DNT.