Adsorption kinetics, isotherms and thermodynamics for malachite green and methylene blue removal in water using low-cost banana peel biosorbent

Low cost biosorbents are one of best promising materials for dye removal in wastewater treatment studies. They offer high removal efficiency and economic viability. In this work, we reported the adsorption of malachite green and methylene blue onto prepared Banana peel powder. The adsorbent was successfully characterized by various techniques. Proximate analysis has shown the presence of various components in the material such as carbohydrate and fiber, protein and fatty acids. FTIR results have confirmed the presence of various active functional groups of the various components determined from the proximate analysis test. EDS test revealed the elemental compositions of the material with rough porous surface from the corresponding SEM result. The results from the effects of dyes concentration have shown the high uptake of the dyes at high concentrations with MG increasing from 77 to 125 mg/g and MB increasing from 82 to 138 mg/g with the dye concentrations of 50 - 200 mg/L. Pseudo secondorder adsorption kinetics were found to be best to describe the mechanism of the adsorption with higher calculated equilibrium adsorption capacity (qe cal) values coefficients of correlations (R2 � 0.99). Higher temperature (323K) was found to be more efficient for the removal of both dyes with the removal efficiency of 97 and 98 using 50 mg/L MG and MB respectively. From the thermodynamics studies, all the values of Gibbs free-energy change (�'G°) were found to be negative and less than 20 kJ/mol which indicated the spontaneous nature of the adsorption. Langmuir model was found to be the best isotherm model for the dyes with the higher value of monolayer adsorption capacity (Qo) of 89.44 mgg-1 and 112.50 mgg-1 for MG and MB at higher temperature of 333K. © 2020 World Research Association. All rights reserved.