The adsorptive potential of potassium hydroxide treated water lily leaves for malachite green dye removal from aqueous solution: isotherms, kinetics and thermodynamics studies

In this research work, a chemically treated water lily leaves (AWL) powder was prepared and used as low cost, efficient and environment friendly adsorbent for the removal of Malachite green (MG) from aqueous solution. Physical parameters of this adsorbent including moisture content (9.93%), ash content (9.09%), organic matter (90.91%), bulk density (0.316g/cm3), pore volume (1.89cm3) and pH (7.07) were determined using standard methods. The adsorbent was characterised by Fourier Transform-Infrared Spectroscopy (FT-IR), Point of Zero Charge (PZC) and Scanning Electron Microscopic (SEM) methods to determined its surface functional group, net neutral charge of 5.90 and surface morphology respectively. Batch techniques were employed to optimise various operational parameters such as contact time, adsorbent dosage, initial dye concentration, solution pH and temperature respectively. The percentage adsorption and adsorption capacity were found to be 90.66% and 148.83mg/g respectively. The kinetics data analysed were best fitted into pseudo-second order relative to other models tested (pseudo-first order, Elovich and Intraparticle diffusion Models) for the different operating temperatures (30, 40, 500C). The isotherms were estimated and confirmed to best fit into D-R model compared to Langmuir, Freundlich and Temkin models analysed. Thermodynamics studies indicates that the sorption is spontaneous, exothermic, and decrease in randomness of the system during the adsorption process as a results of negative values for Gibb’s Free energy (∆G), enthalpy (∆H), and Entropy (∆S). This study confirmed that chemically treated water lily leaves (AWL) powder could be used as an alternative adsorbent for removal of toxic dyes such Malachite green