Boron removal from colemanite mine wastewater by coagulation using zinc hydroxide―A factorial optimization study

Abstract

In this study, boron removal from synthetic solutions and colemanite mine wastewater by coagulation method using in-situ generated zinc hydroxide from zinc chloride salt was investigated. The parameters for Jar test experiments were solution pH (8-12), concentration (50-750 mg/L), temperature (12-40oC), and zinc chloride dosage (1.0204-10.204 g). The saturation pH of zinc hydroxide is 8.93. The boron adsorption capacity reached to maximum value at pH value of 9 and this pH was selected as optimum value. Boron adsorption capacity increased with increasing concentration due to increasing driving force of concentration. High dosages increased the removal percentage. The adsorption of boron to zinc hydroxide had exothermic nature. The optimum conditions obtained from synthetic solutions were applied to the colemanite mine wastewater by 22 factorial designs. The maximum boron adsorption capacity of zinc hydroxide from colemanite mine wastewater was calculated as 43.57 mg/g. The used material and process was promising for boron mine wastewater. The end product of removal from mine wastewater may be used in zinc borate production by solid-state reactions by calcinations.