Bicarbonate activated hydrogen peroxide oxidation of diclofenac in aqueous solution

Abstract

Diclofenac is a non-steroidal anti-inflammatory drug used in the form of oral tablets or in the form of gel and it is one of the most spread organic pollutant, together with its metabolites. There are many ways to eliminate the organic pollutants, like diclofenac, from waters; among them, advanced oxidation processes (AOPs) are widely used, since they are able to produce oxidizing radicals like hydroxyl, superoxide radical, hydroxy peroxyl radical and singlet oxygen from oxidants such as oxygen, hydrogen peroxide and ozone. The presence of bicarbonate anion (HCO3−) in wastewater can significantly reduce the concentration of •OH due to scavenging processes that lead to H2O and to a much less reactive oxygen species, the carbonate radical •CO3−, but also it was proved that the bicarbonate anion is as activator for hydrogen peroxide in sulfide oxidation reactions, epoxidation of alkenes, and degradation of several dyes through generation of carbonate and superoxide radicals. Chemical oxidation with hydrogen peroxide and sodium bicarbonate is an efficient method for degradation of non-steroidal anti-inflammatory drugs, such as diclofenac. The activity of certain micro components have also been studied to see if they have an influence on the degradation reaction. The following micro components were used for this experiment: CoSO4 and NaNO2. It has been observed that the presence of nitrites has an inhibitory effect on the degradation reaction, while the presence of cobalt ions in very low concentrations has an activating effect.