Efficient oxidative degradation of methylene blue catalyzed by Moroccan clay using hydrogen peroxide

Natural clays have been widely used in several applications, particularly in catalysis. This study reports the successful use of natural mixed Moroccan clay minerals as heterogeneous catalyst to degrade methylene blue (denoted MB) from aqueous solutions. The X-ray fluorescence, X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy techniques were used to study the chemical composition and the structural features of natural mixed Moroccan clay. The characterization results showed that the sample is a mixed illite-chlorite-kaolinite (denoted I-C-K). Various experimental parameters were analyzed namely clay catalyst amount, initial dye concentration, and the amount of hydrogen peroxide. Degradation of methylene blue was greatly depressed in the presence of ethylenediaminetetraacetic acid, which is a powerful ligand used for the complexation of iron species. Inductive coupled plasma by atomic emission spectrometry analyses showed that no traces of iron were released into the final solution. Moreover, there was no noticeable loss of activity and damage of the clay structure after five recycles. The oxidation role of hydroxyl free radicals was evaluated using isopropanol (i-Pr-OH).