Comparative analysis of chlorinated intermediates formed during electrochemical and photo(electro)catalytic degradation of 4-Ethylphenol in saline media

Formation of toxic by-products, such as chlorinated intermediates, is one of the major drawbacks of advanced oxidation processes for saline wastewater treatment. Here a comparative analysis of electrochemical oxidation and photocatalytic degradation of 4-Ethylphenol, a non-chlorinated starting model compound of the group of alkylphenols, is presented. Main intermediates have been identified and quantified for brackish [0.03 mol*L-1] and sea water [0.6 mol*L-1] salt concentrations representative for the salt levels in various industrial effluents. Our comparison indicates that photocatalytic treatment (using TiO2 photocatalysts) might be favorable over electrochemical treatments with Pt or BDD anodes due to the minor role of chlorination and the limited formation of chlorinated compounds in photocatalysis. Finally, using photoelectrochemical degradation an external surface recombination mechanism of photogenerated charge carriers will be presented explaining the absence of chlorinated compounds during photocatalytic wastewater treatment.