Biosorption of an Anionic Dye, Eosin Yellow onto Pineapple Peels: Isotherm and Thermodynamic Study

Abstract

Eosin Yellow (EY), an anionic dye (acid dye) was adsorbed using an agricultural waste, pineapple peels (PP) as bio-sorbent in order to investigate its suitability as an alternative adsorbent, and to give insight into the mechanisms of binding. The study includes: equilibrium isotherms and thermodynamics studies. The adsorption isotherm and thermodynamics experiments were conducted using batch equilibrium techniques. The adsorption data were fitted into Langmuir, Freundlich and Temkin isotherm models; as a result, the data fitted well into the Langmuir model from which the adsorption capacity, qe was obtained as 11.76 mg/g. Experimental values of the thermodynamics parameters (ΔH, ΔS and ΔG) and separation factor (RL) in combination suggested that the adsorption process was endothermic, feasible, spontaneous, and had high degree of freedom. Combined results of the isotherms and thermodynamic study suggested a physisorption-chemisorption mechanism for the adsorption process. Therefore, the results of the study could provide useful information to evaluate the raw pineapple peel powder as a cheap source of adsorbent for the removal of EY from waste water.