Reactor design and kinetics study of 4,4'-dichlorobiphenyl photodecay in surfactant solution by using a photosensitizer and hydrogen source.

The system design based on the photodegradation kinetics of 4,4'-dichlorobiphenyl (4,4'-DCB) in surfactant solution with the aid of solvents (acetone and/or squalane) has been studied. Organic solvents acetone and squalane were added as a photosensitizer and a hydrogen source, respectively, to achieve better photolysis performance. The quantum yield of 4,4'-DCB photodecay in Tween 80 micellar solution in the presence of added acetone was increased from 0.032 to 0.043 at its optimal condition. Acetone was shown to be an effective photosensitizer at low concentration, but an overdose would quench the reaction. Furthermore, the addition of squalane could further promote the photodechlorination of 4,4'-DCB in the Tween 80/acetone solutions for an additional 59% of rate improvement. However, an overdose of either solvent was found to cause UV light attenuation and to reduce the observed quantum yield. This effect has been justified and quantified in this study by a proposed light attenuation model, which has also been incorporated into the kinetic equation so that the resulted formula can be used to design the UV reactors for water and wastewater treatment works.