Adsorption of Malachite Green Dye Using Carbonized Water Lily Leaves: Kinetics, Equilibrium and Thermodynamics Studies

Abstract

This study aimed to investigate the potential of carbonized water lily leaves (CWL) as cheap adsorbent for the adsorption of Malachite Green (MG) dye. The CWL characteristics were studied using Fourier Transform Infra-Red (FTIR) spectroscopy, Scanning Electron microscopy (SEM) and point of zero charge (PZC) to establish surface functional groups present, morphology and net neutral charge of the adsorbent. The effects of contact time (15-150min), dosage (20-200mg), initial concentration (20-140ppm), and pH (3-13) on the adsorption process were investigated for the removal of MG by batch adsorption method. The result shows that all the parameters have effect on adsorption process. Compared to the Langmuir, Freundlich, Temkin, and D-R models, the isotherm models were investigated and confirmed to fit well onto the D-R model. Pseudo-second order model best fitted the kinetic data for the different operating temperature (300C, 400C, 500C) of the analysis. Thermodynamics studies clearly indicates that the sorption was spontaneous, endothermic, and increased in the randomness of the systems at adsorbent-liquid interfaces as a result of negative Gibb’s free energy (∆G), positive enthalpy (∆H) and Entropy (∆S). Therefore, this study confirmed that carbonized water lily leaves adsorbent could be used as an alternative adsorbent for the adsorption of toxic dyes such as Malachite green dye.