微波诱导NiO催化降解水中邻苯二甲酸二甲酯

Degradation of dimethyl phthalate in microwave-induced NiO catalytic system

采用超声辐射沉淀-氧化法制备了纳米催化剂NiO,用XRD、XPS、BET和SEM等方法对其进行了表征.构建了微波-NiO催化反应体系,考察了该体系对DMP的去除效率及影响因素,并利用GC/MS、LC/MS鉴定降解产物,提出了可能的降解机理.结果表明:微波诱导NiO催化氧化技术是降解DMP的有效方法,在微波(750W)诱导NiO(0.4mg/L)催化降解体系中,15min内10mg/LDMP的去除率达70%以上.降解效率受到反应体系中不同条件的影响:微波功率的增加可以提高降解效率;催化剂NiO浓度越高,降解速率越快;溶液初始pH值对DMP的降解效率影响非常大,随着pH值的增大,降解效率明显提高.通过GC/MS、LC/MS分析,反应过程中DMP的降解产物主要包括双链水解产物邻苯二甲酸以及异构化产物对苯二甲酸、单链水解产物邻甲酯苯甲酸、苯环三取代产物甲酯基-邻苯二甲酸、侧链缩合形成的双环产物和少量小分子有机酸,由此推断DMP在微波诱导NiO催化体系中的降解主要包括6个途径:水解、异构化、甲酯基反应、侧链缩合成环、羟基化和开环等.

NiO nanoparticles were synthesized through ultrasonic radiation precipitation-oxidation process,calcined at 300℃,and characterized by XRD,XPS,BET,and SEM.The degradation of dimethyl phthalate(DMP)in the microwave-induced NiO catalytic system was investigated.The main intermediates were separated and identified by GC/MS and LC/MS to elucidate the potential mechanisms of the degradation process.Results showed that DMP could be effectively degraded in the experimental conditions,with up the 70%removal rate in 15min by 750W microwave and 0.4mg/L NiO.The degradation rate could be enhanced with the increase of the power of microwave,the dosage of catalyst and the initial pH of solution.The main degradation products of the DMP were identified to be p-carbomethoxy-benzoic acid,phthalic acid,terephthalic acid,carbomethoxy-phthalic acid,and a double-ring product produced through condensation of two lateral chains of DMP and so on.Consequently,the possible degradation mechanism of DMP might include 6 processes:hydrolysis,isomerization,carbomethoxylated reaction,hydroxylation,condensation of lateral chains,hydroxylation and ring-opening mineralization.