Search

Abstract: Freestanding and crack-free titania–silica aerogels with high titanium content (i.e., Ti/Si=1) were successfully prepared by adjusting the hydrolysis of the two alkoxide precursors to a comparable rate during the sol–gel processing. Two titania–silica aerogels were prepared by ethanol and CO2 supercritical drying methods. Well-dispersed, nanometer-sized anatase crystal domains (ca. 10nm) were crystallized by high temperature, ethanol supercritical drying. The crystalline domains were solidly anchored to the aerogel network by Ti–O–Si bonds. Titania–silica aerogels prepared by CO2 supercritical drying method were devoid of TiO2 crystals. A molecular-level mixing was achieved and anatase TiO2 was only crystallized with difficulty by high temperature calcination (1073K). Both aerogels were mesoporous and displayed similar open pore structure that is readily accessible to reactant molecules. However, only the titania–silica aerogel with anatase TiO2 prepared by ethanol supercritical drying was active for the gas phase, photocatalytic oxidation of volatile organic compounds (i.e., isopropanol and trichloroethylene). Catalysts prepared from Degussa P25 TiO2 displayed lower activity under similar reaction conditions. [Copyright &y& Elsevier]

A cerium-doped Sb 2 S 3 anode is successfully fabricated for perfluoroalkyl acids (PFAAs) degradation via a hydroxyl radical dominant electrochemical oxidation (EO) coupled peroxymonosulfate (PMS) reaction. Various PFAAs can be efficiently removed within 25 min with high mineralization and low energy consumption. The hydroxyl radical, sulfate radical, and electron transfer are responsible for PFAAs degradation, and the hydroxyl radical played a dominant role. The electron can be moved from the highest occupied molecular orbital of these PFAAs to the lowest unoccupied molecular orbital of PMS via potential energy difference, further decomposing PMS to generate hydroxyl and sulfate radical for PFAAs degradation. Besides, the corresponding degradation pathway, defluorination, and Gibbs free energy of the reaction for each PFAAs were elucidated based on the identified intermediates and density functional theory calculations. The current study provides insight into the efficient decomposition mechanism of various PFAAs during EO and highlights its promising potential in environmental remediation. [Display omitted] • Electrochemical process can effectively remove various PFAAs. • The hydroxyl radical was responsible for the removal of PFAAs. • This electrochemical process shows strong tolerance to various changes. • PFAA degradation pathways are proposed. • The electron transfer process is clarified. [ABSTRACT FROM AUTHOR]