Removal of boron from waters using fly ash

Abstract

In this study, various operational parameters were tested in order to determine the feasibility of using fly ash to remove boron from aqueous solutions. Studied parameters include time of reaction, material type, solid-liquid ratio, temperature and boron concentration. Preliminary studies revealed that the ability of Yeniköy fly ash to remove boron is similar to that achieved by amberlite under certain conditions. Therefore, Yeniköy ash was selected for sorption studies which aimed at elucidating some of the thermodynamic and kinetic profiles of the sorption process. Experiments were performed using the batch technique at six different initial boron concentrations (10, 30, 50, 100, 250, 500 mg/L), three different temperatures (298, 308, 318 K) and time period ranging from 2 minutes up to 48 hours. The experimental results revealed that the percentage sorption of boron on Yeniköy fly ash can reach up to 100% under appropriate conditions. Results showed that sorption of boron on Yeniköy fly ash followed pseudo-second-order kinetics. The activation energies Ea, were obtained as -90.3, -57.8 and -6.1 kJ/mole for the initial concentrations of 10, 30 and 50 mg/L, respectively. Negative .Ho values were obtained for lower initial concentrations of boron (10, 30, 50 mg/L) indicating that the processes are exothermic. On the contrary, at high concentrations, positive .Ho values were obtained for boron sorption on fly ash indicating that the uptake process becomes endothermic. The entropy change of the sorption process was found in the range of (-234)-(158) J/mole-K.