Chih-Ming Ma

Mineralization of reactive Black 5 in aqueous solution by ozone/H2O2 in the presence of a magnetic catalyst

Particles are often too small to be separated from a reaction system and recycled, especially in wastewater treatment via a catalytic ozonation process. Thus, the objective of this study was to prepare a magnetic catalyst (SiO(2)/Fe(3)O(4)) that can be recycled by using an external magnetic field. The effects of the characteristics of the magnetic catalyst, pH values, catalyst dosage, and initial concentration of Reactive Black 5 (RB5) on mineralization efficiency of the magnetic catalyst/H(2)O(2)/O(3) process were also investigated. The mineralization efficiency of RB5 under various conditions followed the sequence: SiO(2)/Fe(3)O(4)/H(2)O(2)/O(3)>SiO(2)/Fe(3)O(4)/O(3)>Fe(3)O(4)/O(3) approximately H(2)O(2)/O(3)>O(3)>SiO(2)/Fe(3)O(4)/H(2)O(2). Given the results of our reuse and recovery experiments, the magnetic catalyst shows considerable promise for use in water treatment.

Effect of platinum on the photocatalytic decomposition of 2‐chlorophenol in aqueous solution by UV/TiO2

Abstract Photocatalytic decomposition of 2‐chlorophenol in aqueous solutions with platinum‐coated TiO2 slurry under UV irradiation was examined, utilizing various solution pH levels, dissolved oxygen levels and UV light intensities. The atomic percentage of platinum deposited on the TiO2 surfaces were identified by X‐ray photoelectron spectroscopy (XPS) to be in the range of 0.12 and 0.99%. The decomposition of 2‐chlorophenol in acidic aqueous solutions by UV/TiO2 was enhanced to certain extents for experiments conducted with platinum‐coated TiO2 containing up to 0.82% platinum because of the formation of Schottky barrier between platinum and TiO2 to prevent the recombination of electric holes and electrons. However, for experiments conducted with TiO2 coated with higher platinum contents, the decomposition rate of 2‐chlorophenol was reduced markedly, possibly because of the depression of the light absorption of TiO2 by the shielding of coated platinum. The photocatalytic decomposition of 2‐chlorophenol in aqueous solution was inhibited for experiments conducted in neutral and alkaline solutions because the presence of platinum increases the repulsion between 2‐chlorophenol species and TiO2 to hinder the adsorption of 2‐chlorophenol species on TiO2. The decomposition rate of 2‐chlorophenol in aqueous solution by UV/TiO2 was found to be improved significantly with increasing UV light intensity.

Decomposition of 2-chlorophenol by sonolysis in aqueous solution saturated with various dissolved gases

Abstract The effect of several operating factors on the decomposition of 2‐chlorophenol in aqueous solution by sonolysis was investigated in this study. Experiments conducted with the purge of Ar/O2 gas mixture of 2:1 molar ratio into aqueous solution yielded noticeably higher decomposition rate for 2‐chlorophenol (k 1 = 0.0060) possibly due to the increased solubility of the gas mixture. Sonochemical decomposition of 2‐chlorophenol was found to be more effective for experiments conducted in acidic and neutral solutions than in alkaline solutions (about 85% decomposition at solution pH 3). The sonication rate constant for the decomposition of 2‐chlorophenol was increased (0.0006 to 0.00516 at pH = 3; 0.00023 to 0.00284 at pH = 9) with sonication intensity applied between 8 and 50W cm–2. The addition of appropriate amounts of ferrous ions could increase the decomposition rate of 2‐chlorophenol by sonolysis, suggesting that Fe2+ ions may react with hydroxyl peroxide to prevent the recombination of hydroxyl free radicals.