Full factorial design of experiments for boron removal by iron hydroxide from colemanite mine wastewater

Abstract

In this study, iron hydroxide was in-situ generated from iron chloride in the jar test reactors and used for boron removal from both synthetic solutions and colemanite mine wastewater. A time span of 32.5 minutes was enough for equilibrium between boron and iron hydroxide. In the synthetic boron solutions, the variations of boron adsorption capacity of iron hydroxide were investigated by the experimental parameters chosen as pH (7-10), concentration (50-250 mg/L), iron chloride amount (2.5-10 g) and temperature (22.5-40 oC). The optimum pH value for boron removal was determined as 7. Because the higher boron concentrations supported to the boron uptake of iron hydroxide, the optimum boron concentration was 250 mg/L. The boron uptake capacity of iron hydroxide increased with decreasing iron chloride dosage. The boron adsorption onto the iron hydroxide was an exothermic process. The optimum conditions obtained from the synthetic solution experiments were applied to the colemanite mine wastewater by 22 full factorial experimental design of factors which were dilution (1 and 10 fold) and iron chloride amount (5 and 10 g). The optimization of boron removal by iron hydroxide was realized by analyzing Pareto chart. Maximum capacity was calculated as 23.80 mg/g.