The direct and indirect photolysis of 4,4′-dichlorobiphenyl in various surfactant/solvent-aided systems

Surfactant and organic solvents have individually been shown useful in assisting the solubilization of hydrophobic organics out of contaminated soil and promoting UV-induced photodecay at a succeeding treatment process. A newly proposed process is to use the mixtures of surfactant and solvents together in achieving better performance. This study was to explore some basic variables and conditions that may be useful in optimizing the performance of surfactant/solvent-aided UV systems through the selection of surfactant micelles, the adjustment of the reaction pH levels, and the addition of photosensitizer and hydrogen sources. A PCB monomer 4,4'-dichlorobiphenyl (DCB) was used as the target compound for this study; about 1.3 to 2.3 times greater DCB photodecay rate enhancements were observed by using surfactant/acetone or surfactant/triethylamine (TEA) combinations at their optimal conditions. Overdose of these additives (acetone and TEA) will result in retardation of the reactions. However, the use of surfactant with a multi-solvents system (surfactant/acetone/TEA) shows an add-on effect in amplifying the overall decay rate for more than 12%, suggesting that a more complicated mechanism is involved than the simple parallel-reaction assumption. (C) 2002 Elsevier Science Ltd. All rights reserved.