Comment on "Efficient removal of plastic additives by sunlight active titanium dioxide decorated Cd-Mg ferrite nanocomposite: Green synthesis, kinetics and photoactivity".

In this comment paper, some critical shortcomings and errors in the original paper [Chemosphere, 290, 133,307] are discussed. The authors have not adhered to the 12 Principles of Green Chemistry by incorporating the highly toxic metal Cd in their ferrite nanocomposite photocatalyst, despite its synthesis being described as green. Neither the necessity nor the effectiveness of Cd addition in relation to catalytic activity were explained. Although adsorption of the substrates on the catalyst is necessary for the photocatalytic process, excessive adsorption may give a false impression of efficient removal as opposed to true degradation or mineralization. This issue is extremely important for experimental design when the solubility of the substances is very low. The authors have disregarded the solvent effect of organic scavengers for the reactive species, potentially attributing a greater contribution of the degradation of substances to hydroxyl radicals. Some suggestions are also provided to improve their work in the field of photocatalysis.