Calcite-packed columns for the removal of fluoride in industrial wastewater

摘要

Fluoric acid wastewaters from modern semiconductor industries require advanced multi-step treatments to meet stringent reclaim and discharge regulations. Calcite-packed columns were investigated for their performances in treating two types of fluoric acid wastewaters from a semiconductor industry. In case of relatively pure hydrofluoric acid wastewater, the calcite column were capable of reducing the fluoride concentrations from 860 to 7.7 mg/L. Whereas the fluoride in the mixed fluoric acid wastewater was removed to remarkably low levels (lower than 0.1 mg/L) because it was additionally sorbed onto a calcium phosphate solid after precipitated as fluorite at the elevated concentration of calcium. Estimation of saturation indices indicated that metastable fluorite and CaHPO_4 were possible controlling solid phases in the columns. The effluent produced in calcite columns during operation has higher alkalinity which is beneficial for water reuse.