The application of geopolymers as adsorbent in dye removal

Dyes, due to their chemical structure, are used in many industrial sectors such as the textile, tannery and paint industry. Dyes released into wastewater are resistant to light, water and many chemicals. Therefore, once mixed with water, it is difficult to remove the color from the aquatic environment. Although many methods have been developed to remove the wastewater generated as a result of the industrial process, many materials are used as adsorbent in recent years due to their low cost. Geopolymers can be considered as adsorbent due to their low cost and easy availability. In this study, methyl orange removal from aqueous solutions was investigated by using fly ash-based geopolymer as adsorbent. The functional groups of the adsorbent were determined using Fourier-Transform Infrared spectroscopy (FTIR). The structure analysis of the adsorbent was performed by X-ray Fluorescent spectrometry (XRF), Scanning Electron Microscopy (SEM) and Thermogravimetric Analysis (TGA) methods. In the adsorption experiments, the effects of the initial concentration of the methyl orange solution, the amount of adsorbent, contact time, pH, temperature and ultraviolet light source parameters on the removal efficiency and adsorbent capacity were investigated. The highest removal efficiency and adsorbent capacity were found to be 98.5% and 39.39 mg/g, respectively, by using 0.1 g geopolymer adsorbent at 200 ppm initial concentration and pH=2 value.