The purpose of this study was to investigate the removal of safranine T (ST) by geopolymer prepared from coal fly ash (GPFA) nanocomposite, which was conducted as an experimental-lab scale study. The study examined the impact of significant operational factors like solution pH, GPFA mass, ST concentration, temperature, and reaction time. Under the optimal conditions for the process (pH = 9, GPFA mass of 1 g/L, initial concentration of ST of 50 mg/L, temperature of 50 \(^\circ{\rm C} ,\) and reaction time of 75 min), the observed removal efficiency was about 100%. The different types of kinetics and isotherms were investigated, and seven types of error coefficients, in addition to regression coefficients, were also used to ensure the results. According to the obtained results, the Langmuir isotherm and PSO kinetics were the most compatible with the equilibrium data. According to the isotherm that adsorption has been fitted, qmax values were found to be 140.2, 156.2, 166.4, and 173.9 mg/g at different temperatures. Based on the results of Temkin and D-R isotherm, the ST adsorption was a chemical process. Negative ΔGo and positive ΔHo and ΔSo values indicated spontaneous and endothermic adsorption processes and increased disorder during the adsorption process, respectively. The last important point is the remarkable ST removal percentage in the adsorption–desorption cycle, where it was still 82.6% even after 5 cycles of reuse.
