摘要:

Treatment of 2-chlorophenol (2-CP), 4-chlorophenol (4-CP) and 2,4-dichlorophenol (2,4-DCP) in aqueous solutions with direct photolysis (254 nm), ozonation and ozonation with photolysis was studied. A model was developed to simulate chlorophenol treatment in a semibatch column using these processes under acidic conditions in which the chemical reactions are slow. Satisfactory results were obtained in simulating the chlorophenol and ozone concentrations, and the concentrations of an aromatic quinone, hydrogen peroxide and chloride ions formed in the course of the processes. Chlorophenol oxidation systems, however, appeared to be very complex and the formation of intermediate and final products were dependent on the reaction conditions. The degradation rate of chlorophenols was not enhanced by the combination of ozone with UV radiation compared with ozonation alone. Oxidation at low pH in both processes proceeded mainly through reactions with molecular ozone.

ISSN:0191-9512    

DOI:10.1080/01919519808547263

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Ozonation of 2-chlorophenol (2-CP), 4-chlorophenol (4-CP) and 2,4-dichlorophenol (2,4-DCP) in basic aqueous solutions is discussed. In such conditions (pH=9.5), ozonation of chlorophenols proceeds rapidly due to the presence of the dissociated form of the phenolic compound. No ozone occurs in the bulk of the liquid and, in modelling, it becomes necessary to account for the reactions in the liquid film. Two approaches were tested: 1) the film and bulk balances were solved sequentially, and the diffusional fluxes coupling the balances were obtained by solving numerically the concentration profiles in the film; 2) the bulk mass balances were solved without the film mass balances by applying the enhancement factor calculated from existing correlations. The results of both approaches are compared with experimental data. The formation mechanism of an aromatic quinone, hydrogen peroxide and chloride ions during the ozonation appeared to differ under basic conditions from that under acidic conditions. Hydroxyl radical reactions did not, however, have any effect on the chlorophenol decomposition.

ISSN:0191-9512    

DOI:10.1080/01919519808547265

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The effects of ozonation, hydrogen peroxide treatment and chlorination on the quality of organic matter and microbiological growth in drinking water were studied in a pilot plant. All oxidants degraded organic matter (humus) increasing the concentration of assimilable organic carbon (AOC). Even though the oxidants efficiently decreased microbial numbers, microbial regrowth occurred in all drinking waters. Microbial regrowth was strong especially after ozone/hydrogen peroxide treatment. Chlorination combined with ozone and hydrogen peroxide decreased microbial numbers most efficiently. However, microbial growth started even in chlorinated samples within 2-3 days.

ISSN:0191-9512    

DOI:10.1080/01919519808547266

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Experimental results obtained with a wire-to-cylinder ozone generator (5-20cm in length, inner diameter ∼ 12mm), using a 5 to 60l/h flow-rate range of air or N2+O2mixtures, a negative D.C. high voltage being applied to the wire, are analyzed. As for the “classical” industrial ozonizers, the chemical engineering method, based on the energy density concept (Becker parameter β=P/Q) and the global coefficients of formation Kfand destruction Kdof ozone, was applied. Some peculiar behavior of the Kfcoefficient and the role played by nitrogen and its excited levels are pointed out. The results obtained are compared with those of other authors. It appears clearly that the main parameters are not only the Becker parameter but also, and independently, the applied electrical power (P) and gas flow rate (Q) through the residence time (tr). The residence time (or contact time) of the reactant gas with the corona discharge inside the reactor seems to be about some seconds

ISSN:0191-9512    

DOI:10.1080/01919519808547267

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0191-9512    

DOI:10.1080/01919519808547268

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor