Electrolytic oxidation studies of 2,2′-dichlorobiphenyl using ruthenium oxide electrodes, persulfate oxidizers, and UV irradiation

A three probe potentiostat was used to control the potential to a catalytic ruthenium oxide anode in oxidation studies of 2,2′-dichlorobiphenyl (2,2′). Voltages applied varied in one volt increments from 2.0 to 4.0 volts. Studies involved determination of the optimum voltage operating in conjunction with added sodium persulfate oxidizers (0.002 M and 0.018 M) and various exposure times (1 and 8 h) to ultra-violet (254.7 nm) provided by a General Electric BH-6 high pressure mercury arc lamp. The oxidation products of 2,2′ consisted of four compounds. The primary product was 2-chloro, 2′-hydroxyl biphenyl. Other products included: 2-acetoxy, 2′chlorobiphenyl (as previously observed by Laule et al, Journal of Electroanalytical Chemistry, 213: 329–332 (1986)), and dibenzofuran and 5,5′ dichlorodibenzofuran. All products were confirmed using a combination of GC and GC/MS. No reduction in 2,2′ concentration was observed in any of the control solutions in the absence of an applied voltage. Additionally, the presence of an oxidizer and UV irradiation aided the oxidation of 2,2′-dichlorobiphenyl. The oxidation percentage of the 2,2′ at 5 ppm was in the range of 70% under the optimum conditions of applied potential (3.0 volts), persulfate concentration (0.018 M), and UV exposure time (8 h). All reaction conditions and analysis procedures are described.