title: Enhanced ozonation of simulated dyestuff wastewater by microbubbles.
abstract: The ozonation of synthetic wastewater containing azo dye, CI Reactive Black 5, was investigated using a microbubble generator and a conventional bubble contactor. The microbubble generator produced a milky and high intensity microbubble solution in which the bubbles had a mean diameter of less than 58 microm and a numerical density of more than 2.9 x 10(4) counts ml(-1) at a gas flow rate of less than 0.5 l min(-1). Compared with the bubble contactor, the total mass transfer coefficient was 1.8 times higher and the pseudo-first order rate constant was 3.2-3.6 times higher at the same initial dye concentration of 100 mg l(-1), 230 mg l(-1) and 530 mg l(-1) in the proposed microbubble system. The amount of total organic carbon removed per g of ozone consumed was about 1.3 times higher in the microbubble system than in the bubble contactor. The test using terephthalic acid as the chemical probe implied that more hydroxyl radicals were produced in the microbubble system, which contributed to the degradation of the dye molecules. The results suggested that in addition to the enhancement of mass transfer, microbubbles, which had higher inner pressure, could accelerate the formation of hydroxyl radicals and hence improve the oxidation of dye molecules.
authors.affiliation: Department of Chemical Engineering, Tsinghua University, Beijing 100084, China.
authors.forename: Li-Bing
authors.initials: LB
authors.lastname: Chu
authors.forename: Xin-Hui
authors.initials: XH
authors.lastname: Xing
authors.forename: An-Feng
authors.initials: AF
authors.lastname: Yu
authors.forename: Yu-Nan
authors.initials: YN
authors.lastname: Zhou
authors.forename: Xu-Lin
authors.initials: XL
authors.lastname: Sun
authors.forename: Benjamin
authors.initials: B
authors.lastname: Jurcik
mesh_terms: D004396:Coloring Agents / Q000737:chemistry; D045423:Microbubbles; D009282:Naphthalenesulfonates / Q000737:chemistry*; D010126:Ozone / Q000737:chemistry*; D013997:Time Factors; D014865:Waste Disposal, Fluid / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000737:chemistry
chemical_list: D004396:Coloring Agents; D009282:Naphthalenesulfonates; D014874:Water Pollutants, Chemical; D010126:Ozone; C063421:Remazol black B