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.

In this study, the adsorption of methyl violet from an aqueous solution using carbonised water lily (CWL) leaves powder as a low-cost, efficient and eco-friendly adsorbent was investigated using a batch system under controlled conditions. The adsorbent's moisture, organic matter, ash, bulk density, pore volume, and pH were determined. The adsorbents were characterised by scanning electron microscopy (SEM) and Fourier Transform Infrared (FT-IR) techniques which confirm the adsorption of the methyl violet onto the CWL adsorbents. The effect of adsorption parameters such as contact time, dosage, initial concentration, pH and temperature were studied for optimisation. It was confirmed that contact time, dosage, concentration, pH and temperature positively affected adsorption. The kinetic data were best described by pseudo-second order under all experimental temperatures. The adsorption isotherms were estimated and established to fit nicely into the D-R model compared to other models generated and tested. Thermodynamic studies of the sorption process indicate that the process was feasible, spontaneous, and exothermic and decrease in the randomness of the adsorption process during the transfer of molecules between the adsorbent and adsorbates with entropy (∆S) of 23.77 J/mol.K. due to negative values of Gibb's free energy observed. This study confirmed that CWL could be employed as a low-cost, eco-friendly adsorbent for removing toxic dyes such as methyl violet from an aqueous solution.