title: MnO2/CeO2 for catalytic ultrasonic degradation of methyl orange.
abstract: Catalytic ultrasonic degradation of aqueous methyl orange was studied in this paper. Heterogeneous catalyst MnO2/CeO2 was prepared by impregnation of manganese oxide on cerium oxide. Morphology and specific surface area of MnO2/CeO2 catalyst were characterized and its composition was determined. Results showed big differences between fresh and used catalyst. The removal efficiency of methyl orange by MnO2/CeO2 catalytic ultrasonic process was investigated. Results showed that ultrasonic process could remove 3.5% of methyl orange while catalytic ultrasonic process could remove 85% of methyl orange in 10 min. The effects of free radical scavengers were studied to determine the role of hydroxyl free radical in catalytic ultrasonic process. Results showed that methyl orange degradation efficiency declined after adding free radical scavengers, illustrating that hydroxyl free radical played an important role in degrading methyl orange. Theoretic analysis showed that the resonance size of cavitation bubbles was comparable with the size of catalyst particles. Thus, catalyst particles might act as cavitation nucleus and enhance ultrasonic cavitation effects. Measurement of H2O2 concentration in catalytic ultrasonic process confirmed this hypothesis. Effects of pre-adsorption on catalytic ultrasonic process were examined. Pre-adsorption significantly improved methyl orange removal. The potential explanation was that methyl orange molecules adsorbed on catalysts could enter cavitation bubbles and undergo stronger cavitation.
authors.affiliation: School of Environment & Natural Resource, Renmin University of China, 59 Zhongguancun Street, Beijing 100872, China.
authors.forename: He
authors.initials: H
authors.lastname: Zhao
authors.affiliation: School of Environment & Natural Resource, Renmin University of China, 59 Zhongguancun Street, Beijing 100872, China. Electronic address: zgm5000@126.com.
authors.forename: Guangming
authors.initials: G
authors.lastname: Zhang
authors.affiliation: School of Environment & Natural Resource, Renmin University of China, 59 Zhongguancun Street, Beijing 100872, China; Master Erasmus Mundus Mamaself Universit Rennes, 1 Campus de Beaulieu, 35042 Ernnes Cedex, France.
authors.forename: Quanling
authors.initials: Q
authors.lastname: Zhang
keywords: Catalytic ultrasonic degradation; Cavitation effect; Methyl orange; MnO(2)/CeO(2); Pre-adsorption