Microwave-induced degradation of N-nitrosodimethylamine (NDMA) sorbed in zeolites: Effect of mineral surface chemistry and non-thermal effect of microwave. (10th February 2018)

• Record Type: Journal Article
• Authors: Hu, Yuanan; He, Yuanzhen; Cheng, Hefa
• Is Part Of: Journal of cleaner production. Volume 174(2018)
• Page Start: 1224
• Page End: 1233
• Publication Date: 2018-02-10
• Subjects: N-nitrosodimethylamine (NDMA) -- Micropore sorption -- Microwave-induced degradation -- Dealuminated ZSM-5 -- Surface chemistry -- Non-thermal effect; Factory and trade waste -- Management -- Periodicals; Manufactures -- Environmental aspects -- Periodicals; Déchets industriels -- Gestion -- Périodiques; Usines -- Aspect de l'environnement -- Périodiques; 628.5
• DOI: 10.1016/j.jclepro.2017.11.014
• Languages: English
• ISSNs: 0959-6526

Abstract

Abstract: N -nitrosodimethylamine (NDMA), a highly toxic and carcinogenic disinfection byproduct, cannot be efficiently removed by conventional water treatment processes, while sorption by microporous minerals, followed by destruction with microwave irradiation has been developed as a promising alternative. This work examined the impact of surface cation density and type on sorption of NDMA on dealuminated ZSM-5 zeolites, and on microwave-induced degradation of the sorbed NDMA, as well as the non-thermal effect of microwave. NDMA sorption was found to increase with the framework Si/Al ratio of dealuminated ZSM-5 zeolites (i.e., decreasing density of surface cations), and was also influenced by the type of surface cations. Degradation of the sorbed NDMA proceeded faster with increases in the power level of microwave and in the micropores with higher densities of surface cations, which was attributed to the increases in the number and/or temperature of micro-scale "hot spots" formed by microwave dielectric superheating of the surface cations. The degradation rate of sorbed NDMA was also found to be inversely correlated with the hydration free energy of surface cations present in the zeolite micropores. The apparent activation energy estimated from the temperature dependence of NDMA degradation in the micropores under microwave irradiation was 18.2 kJ/mol, which is much lower than those of typical thermolysis reactions and is indicative of significant contribution from the non-thermal effect of microwave. Graphical abstract: Image 1 Highlights: Density of surface cations affects NDMA sorption in micropores of dealuminated ZSM-5. Increases in density of surface cations lead to faster degradation of sorbed NDMA. Type of surface cations also affects microwave-induced degradation of sorbed NDMA. Dielectric heating of polar species by microwave is responsible for NDMA degradation. Non-thermal effect of microwave also has significant contribution to NDMA degradation.