La0.8Ce0.2Fe0.9Ru0.1O3/TiO2催化湿式氧化降解草甘膦废水

Degradation of glophosate wastewater by catalytic wet air oxidation on La_(0.8)Ce_(0.2)Fe_(0.9)Ru_(0.1)O_3/TiO_2 catalyst

草甘膦是种广谱除草剂,草甘膦废水产量大、可生化性差。以钙钛矿型La_(0.8)Ce_(0.2)Fe_(0.9)Ru_(0.1)O_3/TiO_2为催化剂,采用湿式氧化(WAO)和催化湿式氧化(CWAO)法对草甘膦废水进行高效降解,并对草甘膦降解机制进行研究。应用XRD和XRF对催化剂进行表征,结果表明,合成的催化剂具有钙钛矿结构,但由于Ru原子半径太大可能没有完全进入钙钛矿骨架,导致CWAO反应后有微量Ru溶出。考察反应温度对草甘膦降解的影响,并对反应过程中C、N、P产物的选择性进行分析,结果表明,提高反应温度和加入催化剂有利于提高草甘膦转化率及对CO2和PO_4^(3-)的选择性,但反应温度过高不利于生成N_2,因为高温下NH3-N更容易被氧化成NO_2^-和NO_3^-。在实验条件下,合适的反应温度为200℃,反应180 min草甘膦转化率大于95%,同时对CO_2和N_2有较高的选择性,分别为54.59%和19.40%。应用计算量子化学计算草甘膦分子的净电荷分布,结果表明,WAO和CWAO中草甘膦反应的断键部位为C—C键、C—P键和C—N键,而后中间产物再进一步被氧化为CO_2、N_2、NO_2^-、NO_3^-、PO_4^(3-)等。

Glyphosate is a broad-spectrum herbicide. In the synthesis process of glyphosate,large amount of wastewater would be produced and biodegraded difficultly. The degradation mechanism of glyphosate by catalytic wet air oxidation（ CWAO） on La（0. 8）Ce（0. 2）Fe（0. 9）Ru（0. 1）O3/TiO2 was studied. The catalyst was characterized by XRD and XRF. The results showed that the catalyst had perovskite structure. Ru did not completely enter into the catalyst framework because of too large atomic radius which resulted in dissolution of Ru after CWAO. Effects of reaction temperature on degradation of glyphosate were investigated. Selectivity of products of C,N,P was analyzed. The results showed that the conversion of glyphosate and selectivity of CO2 and PO4（3-） could be significantly enhanced by addition of catalyst and increasing of reaction tempera-ture. Glyphosate was more likely to be oxidized to NO-2 and NO3- instead of N2 at high temperature. After180 min at 200 ℃,the conversion of glyphosate was greater than 95% while the selectivity of CO2 and N2 were 54. 59% and 19. 40%,respectively. Combined with the computational quantum chemistry,the mechanism of glyphosate degradation was assumed that C—C,C—N and C—P are the active sites in these WAO and CWAO reactions,and both the CO2,N2,NO2-,NO3-,and PO4（3-） could be generated during oxidation process. The net charge numbers of all the atoms were displayed to confirm the possibility and feasibility of the above reactions.