Chitin-based porous carbons from Hermetia illucens fly with large surface area for efficient adsorption of methylene blue; adsorption mechanism, kinetics and equilibrium studies

Abstract

Precursor of activated carbon were empty casings of pupas of Hermetia illucens fly. The precursor was subjected either to physical activation (CO2) or chemical activation (H3PO4, K2CO3, Na2CO3). Impregnation with potassium carbonate provided the adsorbent characterized by the best parameters, its surface area was 1167 m2/g, while the maximum sorption capacity towards methylene blue in water solution, according to the Langmuir model was 641.03 mg/g. The best fit to the experimental data was obtained for the pseudo second-order model, which indicated that the process was driven by chemisorption. Moreover, the sorption capacity of the activated carbons increased when pH of the dye solution was higher than pHpzc. The adsorbents obtained by impregnation with K2CO3 may be reused. The study conducted on the thermodynamics of dye adsorption on adsorbents revealed that it was endothermic in nature. The highest efficiency of desorption (80 %) was obtained for 0.5 mol/L of hydrochloric acid.