Removal of anionic dyes (Reactive Black 5 and Congo Red) from aqueous solutions using Banana Peel Powder as an adsorbent

The adsorption characteristics of Reactive Black 5 (RB5) and Cong Red (CR) onto Banana Peel Powder (BPP) from aqueous solution were investigated as a function of pH, contact time, initial dye concentration and temperature. The BPP was characterized by Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) analysis. FTIR results revealed that hydroxyl (OH), amine (-NH) and carboxyl (-C-O) functional groups present on the surface of BPP. The SEM results show that BPP has an irregular and porous surface morphology which is adequate for dye adsorption. The equilibrium data were analyzed using Langmuir and Freundlich isotherm models. Experimental results were best represented by the Langmuir isotherm model. The adjustments of models were confirmed by the Chi-square (chi(2)) test and the correlation coefficients (R-2). The maximum monolayer adsorption capacities of RB5 and CR on BPP calculated from Langmuir isotherm model were 49.2 and 164.6 mg/g at pH 3.0 and 298 K. Experimental data were also tested in terms of adsorption kinetics using pseudo-first-order and pseudo-second-order kinetic models. The results showed that the adsorption processes of both RB5 and CR followed well pseudo-second-order kinetic models. The calculated thermodynamic parameters AG, Alf and AS showed that the adsorption of RB5 and CR onto BPP was feasible, spontaneous and endothermic in the temperature range 298-318 K. The RB5 and CR were desorbed from BPP using 0.1 M NaOH. The recovery for both anionic dyes was found to be higher than 90%. Based on these it can be concluded that BPP can be used as an effective, low cost, and eco-friendly adsorbent for CR removal than RB5 from aqueous solution.