Study on the Reasons for the Difference between the Measured and Real Values of Fluoride Ion Content after Addition of Defluorinating Agent in Wastewater Treatment Process

Excessive fluoride (F) content in water bodies can seriously affect human health, so there are strict standards for the discharge of fluoridated wastewater. In this paper, the fluoride ion concentration decreased to about 0.2 mg/L after the treatment of industrial wastewater by the three-stage process of lime emulsion + defluoridation agent + adsorption. However, it was found that the fluoride ion concentration of water samples increased after defluoridation. This phenomenon was related to the defluorinating agent added. Al and Fe ions in the defluorinating agent would cause large deviations between the detected values and the true values, while the masking agent added to the detection has a limited effect. The change of temperature in the presence of Al, Fe and Ca ions would also affect the detection of fluoride ions