Raw clays from Morocco for degradation of pollutants by Fenton-like reaction for water treatment

Abstract

Three raw clays from Morocco were used as heterogeneous catalysts for Fenton-like oxidation of organic pollutants in water. The selected pollutants were two dyes used in the textile industry, Congo Red (CR) and Tartrazine (Tar, known also as a food coloring compound, E102) and Caffeine (Caf), a stimulant drug present in popular beverages such as coffee and tea, commonly used in Morocco. Two different processes were used for their degradation: (i) Fenton-like reaction; and (ii) electro-Fenton-like reaction. Process (i) was used for Tar and Caf degradation in the presence of clays from different region of Morocco (Middle Atlas - ClayMA, Fez - ClayF, and Ourika - ClayO), the best results being obtained with ClayO and ClayMA, on which 60.0% and 23.4% of conversion and 41.0% and 20.5% of mineralization were achieved for Tar and Caf, respectively. Process (ii) was used for degrading CR by clay-modified electrodes (CME) using the rawclays from Fez and Ourika regions (ClayF and ClayO). The stability of the CME was assessed by cyclic voltammetry studies, which proved that they are stable in the experimental conditions used. The electrodegradation of CR dye, performed without hydrogen peroxide in the reaction medium, achieve 67.0% of mineralization at the end of electrolysis (2 h).