Toward the Development of a Novel Electro-Fenton System for Eliminating Toxic Organic Substances from Water. Part 1. In Situ Generation of Hydrogen Peroxide

The use of a novel electrochemical oxidation system is investigated for in situ generation of hydrogen peroxide, which constitutes the major reactant for hydroxyl radical (OH center dot) production via the Fenton reaction. The novel electro-Fenton (EF) filter is comprised of a stack of carbon anodic and cathodic electrode pairs, for operation in continuous mode, with potential applications in elimination of toxic organic substances (e.g., pesticides, pharmaceuticals) from drinking and similar water sources. Experiments are performed to assess the performance of three types of electrodes (made of woven carbon fibers, loose carbon fibers, and powdered carbon) in the synthesis of hydrogen peroxide by supplying to the system a low voltage direct current. The efficiency of H2O2 electro-generation as a function of various process parameters (i.e., electrode potential, solution pH, ionic strength) is studied for the most promising carbon material (i.e., loose carbon fibers). The results indicate that the optimal cathodic potential for H2O2 generation is 1.3 V vs Ag/AgCl reference electrode at pH 3, with initial mean dissolved oxygen concentration 8.5 mg L-1. Under these conditions, the average current density and average current efficiency are 5.2 A.m(-2) and 70%, respectively. Reduced electrolyte (Na2SO4) concentration significantly affects the H2O2 electrogeneration rate, whereas increased solution pH leaves the current efficiency unaffected. Research is ongoing regarding optimization of the EF filter and the effective impregnation (in the porous cathodic electrodes) of iron nanoparticles, which mediate the continuous degradation of organic substances.