The application of synthesized geopolymer for the removal of cationic dye from industrial wastewater

Abstract

In this study, a low-cost and effective coal fly ash porous geopolymer (CFPG) was prepared through alkali activation and applied as adsorbent for the removal of Rhodamine B (RhB) from real industrial wastewater. Mineral composition, microstructural analysis and surface chemistry were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy, respectively. The batch experiment was investigated at different CFPG dose (0.4–2 g), RhB concentration (5–30 mg/L), pH (2, 7 and 10) and contact time (30–300 min). The removal efficiency for the adsorption of RhB using CFPG was affected by dosage, concentration, and time. However, removal efficiency of 100 % was achieved at pH (2, 7 and 10) indicating that the adsorbent can be used in wide pH range owing to the zwitterionic nature of RhB. The findings demonstrated that while increasing the initial dye concentration resulted in a decrease in removal efficiency, increasing the CFPG dose and contact time led to an improvement in removal efficiency. Additionally, for specified values of examined parameters, such as CFPG dose of 2 g, initial RhB dye concentration of 5 mg/L, and contact time of 300 min, the maximum efficiency of 100 % was achieved for RhB dye removal. The study on removal efficiency of CFPG on selective dyes showed that it could also be used to remove other cationic dyes such as malachite green and crystal violet in industrial wastewater as removal efficiency of 100 % was obtained for the removal of both dyes. Pseudo-first-order (R2 = 0.985) and Freundlich (R2 = 0.860) models were most suitable for the adsorption process.

Keywords

• Adsorption
• Rhodamine B
• Geopolymer
• Fly ash
• Circular economy