Single adsorption of diclofenac and ronidazole from aqueous solution on commercial activated carbons: effect of chemical and textural properties

The importance of the textural and physicochemical characteristics upon the adsorption capacity of the commercial activated carbons (ACs) Coconut, Wood, Merck, Darco, and Norit towards ronidazole (RNZ) and diclofenac (DCF) from water solution was investigated thoroughly in this work. At pH = 7, Coconut AC and Wood AC presented the highest adsorption capacity towards RNZ (444 mg/g) and DCF (405 mg/g). The maximum mass of RNZ adsorbed onto Coconut AC was higher in this study than those outlined previously in other works. Besides, the maximum capacity of Wood AC for adsorbing DCF was comparable to those found for other ACs. The adsorption capacity of all the ACs was increased by surface area and was favored by incrementing the acidic site concentration. The pi-pi stacking interactions were the predominant adsorption mechanism for the RNZ and DCF adsorption on ACs, and the acidic sites favored the adsorption capacity by activating the pi-pi stacking. Electrostatic interactions did not influence the adsorption of RNZ on Coconut AC, but electrostatic repulsion decreased that of DCF on Wood AC. The adsorption of DCF on Wood AC was reversible but not that of RNZ on Coconut AC. Besides, the adsorption of RNZ and DCF on the Coconut and Wood ACs was endothermic in the range of 15-25 degrees C.

Automated summary

The textural and physicochemical characteristics of commercial activated carbons have a significant impact on their adsorption capacity for ronidazole and diclofenac. Coconut AC and Wood AC exhibit the highest adsorption capacity for RNZ and DCF at pH=7. The adsorption mechanism is mainly driven by π-π stacking interactions, and the presence of acidic sites enhances the adsorption capacity. The adsorption of RNZ on Coconut AC is irreversible, while the adsorption of DCF on Wood AC is reversible.