Removal of Cationic Dye – Methylene Blue- from Aqueous Solution by Adsorption on Fly Ash-based Geopolymer

The aim of this work is to investigate the workability of removing methylene blue (MB) from aqueous solution using fly ash based geopolymer powder (FAG). The FAG was formulated by mixing fly ash (FA) and alkaline activator in an appropriate ratio. The FA and FAG were characterized by physical and chemical techniques, such as X-ray fluorescence spectroscopy, X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) and Scanning Electron Microscopy (SEM). To optimize the process of removing MB onto FAG, different parameters were studied such as, the effect of pH, initial dye concentration, adsorbent dosage, contact time and temperature. The results show that the maximum removal efficiency of MB was found in the basic environment. Isotherm studies showed that the adsorption of MB using FAG followed Langmuir model and the maximum adsorption capacity of MB is about 37.04 mg/g. Kinetic studies show that the adsorption process follows the pseudo second-order kinetic. The thermodynamic study indicated that the adsorption was favorable, endothermic and spontaneous.