Full factorial design of experiments for boron removal from Colemanite mine wastewater using Purolite S 108 resin

Abstract

Boron pollution has a vital importance in Bigadic boron mine in Turkey because the wastewaters of the mine are stored in a soil dam that threats the underground water quality. In this study the optimization of boron removal from the boron mine wastewater using Purolite S 108 resin was investigated by means of a 2(3) full factorial experimental design. Experiments were carried out in batch mode as a function of pH, temperature and resin-to-solution ratio. The low (1) and high (2) levels of the parameters for pH, temperature and resin-to-solution ratio were 2.5 and 10, 12 degrees C and 40 degrees C and 1 g/50mL and 2 g/50mL respectively. Boron adsorption capacity of the resin increased with low temperature, low resin-to-solution ratio and high pH. When the probability constants (p<0.05) at 95% confidence level were taken into consideration, only pH was found as statistically important parameter. The optimization of the parameters to obtain optimum conditions was done by interpretation of cube plots, Pareto chart and contour plots. A time span of 48 hours was enough to reach the equilibrium. Adsorption data were analyzed with the Langmuir and Freundlich isotherms. Data fitted to the Langmuir isotherm with a coefficient of determination value of 0.988. Maximum adsorption capacity was calculated as 12.87 mg g(-1). The fixed bed kinetics of boron adsorption onto resin could be explained by the Thomas and Yoon-Nelson models with a coefficient of determination value of 0.938. The fixed bed capacity of the resin was calculated as 12.71 mg g(-1).