Cationic dye removal using Pergularia tomentosa L. fruit: kinetics and isotherm characteristics using classical and advanced models

The agricultural crops prove to be low-cost and abundant biosorbents that are able to adsorb dyes from contaminant water. In the present study, different techniques were used to characterize the powdered Pergularia tomentosa fruit. After that, the biomaterial was exploited to investigate the adsorption of methylene blue in batch mode. The effects of initial pH, contact time, dye concentration, biosorbent dose, and temperature on the biosorption capacity have been performed. The fit of the adsorption isotherms was performed by means of several classical models and advanced models derived from statistical physics. The two-energy monolayer model proves to be the more suitable. It appears that two functional groups of the biosorbent are involved in the dye biosorption. The adsorption energy ranges from 14 to 18 kJ·mol which indicates a physiosorption mechanism. The maximum adsorption capacity is 152 mg·g. Pergularia tomentosa fruit proves to be attractive for the efficient removal of cationic dyes from polluted water.