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• Choice of activator has impact on the adsorbent sorption capacity. • The best activated carbons obtained had a high 1167 m 2 /g specific surface area. • Maximum methylene blue adsorption capacity (q m ) was 641.03 mg/g. • Thermodynamic studies showed the adsorption process was spontaneous and endothermic. Precursor of activated carbon were empty casings of pupas of Hermetia illucens fly. The precursor was subjected either to physical activation (CO 2 ) or chemical activation (H 3 PO 4 , K 2 CO 3 , Na 2 CO 3 ). Impregnation with potassium carbonate provided the adsorbent characterized by the best parameters, its surface area was 1167 m 2 /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 pH pzc . The adsorbents obtained by impregnation with K 2 CO 3 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.
Bazan‐Wozniak et al. (Sun,) studied this question.