Solar photo-Fenton at mild conditions to treat a mixture of six emerging pollutants

Abstract

The applicability of photo-Fenton to degrade a mixture of emerging pollutants (EPs) namely amoxycillin, acetaminophen, acetemiprid, caffeine, clofibric acid and carbamazepine has been studied at different scenarios. At high concentrations, acidic photo-Fenton was able to achieve a fast removal of the EPs. Although, complete mineralization was not reached, the toxicity of the solution was decreased according to the respiration of activated sludge and luminescence of Vibrio fischeri assays, although according to this last assay a transitory enhancement of the toxicity was found, attributable to the formation of toxic by-products such as phenols, chlorophenols and chlorinated pyrydines. Experiments carried out with 5mg/l of each EP showed that at neutral media the process was two orders of magnitude less efficient than at acidic pH, although it was still able to remove the EPs. The aqueous matrix has a remarkable effect on the process as the presence of humic acids increased the reaction rate and inorganic salts played an inhibitory role. Finally, experiments performed with 10μg/l of each EP showed that under those experimental conditions nearly complete removal of the EPs was reached with neutral photo-Fenton after 120min of irradiation; in this case, humic substances played a disfavorable role.