Electrolytic and electro-irradiated technologies for the removal of chloramphenicol in synthetic urine with diamond anodes

Abstract

Hospital effluents are a major source for the occurrence of pharmaceuticals in the environment. In this work, the treatment of synthetic urine polluted with chloramphenicol is studied by using three different conductive-diamond electrochemical oxidation technologies: electrolysis (single electrolysis), photoelectrolysis and high-frequency ultrasound sonoelectrolysis. These technologies were evaluated at 10 and 100 mA cm−2. Results shows that not only chloramphenicol but also other organics contained in urine are completely mineralized by electrolysis. Ammonium is the main inorganic nitrogen species formed and it can react with the electrogenerated hypochlorite, favouring the formation of chloramines. These species prevent the potential formation of perchlorate from chlorides contained in urine at low current densities (10 mA cm−2) and delay its occurrence at high current densities (100 mA cm−2). On the other hand, irradiation of ultraviolet (UV) light or high-frequency ultrasound (US) produce changes in the performance of the electrolytic treatment, but these changes are not as important as in other cases of study shown in the literature. Nonetheless, the effect of electroirradiated technologies seems to be higher and depends on the type of pollutant when working at low current densities (10 mA cm−2). It is positive in the case of the degradation of the antibiotic and the uric acid and negative in the case of urea where there is a clear antagonistic effect. Production of oxidants increases with the current density although in lower ratio than expected. These results are of great importance because clearly point out that electrolytic technologies can be applied to minimize the diffuse pollution associated to pharmaceuticals before discharge into municipal sewers.