Electroenzymatic mineralization of 2-chlorobiphenyl in synthetic wastewater

An electroenzymatic method is developed to degrade 2-chlorobiphenyl (2-CB) with horseradish peroxidase (HRP) immobilized glassy carbon electrode as the working electrode. Cyclic voltametric studies were carried out to understand the redox reactions involved. An applied potential of –0.5 V was found suitable for the degradation of 2-CB. During degradation, dechlorination of 2-CB was confirmed by the measurement of chloride ion concentration in the reaction mixture, and was found almost equimolar to the initial 2-CB concentration. Chloride concentration was 0.53 ppm at the end of reaction while the initial 2-CB concentration was 3.15 ppm. That means that almost 97% of the chlorine in 2-CB sample was liberated. Total organic carbon (TOC) measurements revealed that almost 83% 2-CB was mineralized. Degraded products were analyzed by GC-MS to find reaction intermediates. However, no peak could be detected except 2-CB. Therefore, the most probable route of degradation is through dechlorination followed by biphenyl ring cleavage and mineralization.

We developed an electroenzymatic technique for the mineralization of 2-chloro biphenyl in synthetic waste water. Experimental findings clearly demonstrated that combined effect of immobilized horseradish peroxidase and in situ generation of hydrogen peroxide in the reactor was a potential alternative for 2-CB degradation in synthetic waste water. This technique was quite fast comparing to typical bioremediation techniques and proceeded to mineralization without producing any harmful intermediates or end products. The current efficiency for the electroenzymatic technique should be improved further. More effort is needed to develop effective enzyme immobilization technique, which is underway.