Full factorial design of experiments for boron removal from solutions by Purolite S 108 resin converted to hydroxyl form

In this study, boron removal from synthetic solutions using Purolite S 108 resin converted to hydroxyl form was investigated. Experiments were carried out in batch mode as a function of pH (4–10), concentration (50–500 mg/L), and resin-to-solution ratio (1–2.5 g/50 mL). Optimum pH value was determined as 10 and exchange capacity increased with increasing concentration. Boron exchange capacity of the resin increased at low solid-to-solution ratios. A 23 full factorial experimental design was applied to determine the optimum values and degree of importance of parameters. The low (1) and high (2) levels of the parameters were 3 and 7 for pH, 500 and 1,000 mg/L for concentration, and 1 and 2 g/50 mL for solid-to-solution ratio, respectively. The optimization of the parameters was done by interpretation of cube plot and Pareto chart. At 87% confidence level, the importance sequence of parameters and their interaction were as follows: concentration, pH-concentration interaction, and pH had positive effect on capacity. Solid amount, pH-solid amount, and concentration–solid amount interactions had negative effect on the capacity. Maximum capacity was calculated to be 25.5 mg/g. The kinetic data fitted to the pseudo-second-order model and rate controlling steps were liquid film and ash layer diffusion.