Comparative studies on adsorptive removal of phenol by three agro-based carbons: Equilibrium and isotherm studies

The present study deals with the adsorption of phenol on carbon-rich black gram husk (BGH), green gram husk (GGH), and rice husk (RH). All these agro-wastes were collected from the local mills and physico-chemical treatments were carried out to improve their adsorption capacity. Batch studies were performed to evaluate the effect of various experimental parameters such as initial pH, contact time, adsorbent dosage, and initial phenol concentration (C0) of 100 mg/l. Optimum conditions for phenol removal were found to be at pH 5.1 (in the range 2–12), an adsorbent dosage of 0.5 g/l of solution and for an equilibrium time of 6 h. Equilibrium isotherms for the adsorption of phenol on BGH, GGH, and RH were analyzed by Freundlich, Langmuir, Temkin, Redlich–Peterson, and Dubinin–Radushkevich isotherm models. Redlich–Peterson isotherm was found to be the best representative for phenol-sorption on all the three adsorbents studied.