Intrinsic Activity of SBA-like Silica in the Catalytic Ozonation of Organic Pollutants

Abstract

ABSTRACTHydrothermal synthesis using two gel compositions: i. 1 SiO2: 0.059 P123: 56.130 HCl: 607.638 H2O; ii. 1 SiO2: 0.006 P123: 0.013 F127: 42.439 HCl: 442.876 H2O, resulted in highly crystalline SBA-15 and SBA-16 like silica with intrinsic activity in the catalytic ozonation of oxalic acid (OA), phenol (φ-OH) and Orange G (OG) in water at room temperature. X-ray diffraction, nitrogen adsorption–desorption, transmission and scanning electron microscopies revealed highly ordered mesoporous structure, with large surface area, regular channels and uniform particle size. UV-Vis analysis provided faster, more precise and reliable assessments of the decomposition yield and process selectivity than the conventional and laborious method of Chemical Oxygen Demand (COD). The ozone reactivity was found to be favored by increasing size of the organic substrate. OG and phenol decomposition required shorter ozonation time (20, 15 min, respectively) than OA, involving mainly phenyl ring hydroxylation and cleavage. Measurements through thermal programmed desorption of carbon dioxide and water revealed that the catalytic activity of the SBA samples involves adsorption via both acid-base and hydrophobic interactions. Suitable SBA modifications allow tailoring these interactions for even faster ozonation without persistent traces of short chain derivatives.