Nanocomposite co-catalysts, based on smectite and biowaste-derived carbon, as peroxymonosulfate activators in degradation of tartrazine

Chitosan (Ch)-derived from biowaste along with smectite, an abundant clay mineral, were used in a low-cost and eco-friendly synthesis of a new type of catalyst. Nanocomposite catalysts constituted of Co supported on smectite with chitosan-derived carbon loading were obtained using an impregnation carbonization procedure and denoted as Co/cCh-S-T (T stands for applied carbonization temperature). The carbonization was performed in the temperature range from 400 °C to 700 °C in the flow of N2 providing inert atmosphere. The temperature of 500 °C was found to be the most suitable for catalyst synthesis regarding catalytic performance in a peroxymonosulfate activated degradation of tartrazine. The incorporation of carbonized chitosan structure within the interlamellar space of the smectite was confirmed using X-ray powder diffraction. The high-resolution transmission electron microscopy confirmed a layered structure of nanocomposites characteristic for smectite, as well as the presence of small spherical cobalt containing nanoformations (confirmed by energy dispersive X-ray spectroscopy) well dispersed within structure. The existance of cobalt in the CoII and CoIII oxidation state was proven by X-ray photoelectron spectroscopy. The Co/cCh-S-500 catalyst was proven to be stable and efficient after 5 consecutive cycles. This work showed that nanocomposite Co-catalysts, based on smectite and biowaste-derived carbon, as peroxymonosulfate activators exhibited a very promising performance in the degradation of water pollutants.