A Study On Fluoride Removal By Electrosorption

Fluoride is a necessary trace element for human since it plays an important role in bone development. Proper quantity of fluoride intake is helpful for human, but water containing excessive fluoride concentration may result in bone distortion, bone aching, anchylosis, muscle and tendon calcium, walking trouble and even paralysis for severe victims. In north-west china, there are about 70 million people drinking water containting excessive amount of fluorine that caused fluorosis in different degree. Performance of fluoride removal by electrosorption of composite electrodes was systematically studied for searching reasonable methods.In this paper, the research on the use of composite electrodes was doing on both batch reactor and dynamic test. Batch reactor tests were performed to study adsorption kinetics equations, adsorption isotherm equations and the effect of space between electrodes on fluoride removal. Dynamic tests were performed to study the effect of voltage, initial concentration and flowrate on fluoride removal efficiency and the self-made testing equipment was used.Batch reactor tests showed that the electrosorption behavior of composite electrodes on fluoride removal conformed to the first order reaction kinetics equations and between reaction rate constant Kand voltage E were an liner correlation. The Freundlich isotherm equation fit the experiment data excellently, showed linear correlations of K with voltage E, and the fluoride removal efficiency was improved with space between electrodes decreased.Dynamic tests showed that electrosorption of composite electrodes on fluoride removal had more advantages, for instance, low energy consumption, easy desorption and operation, and little secondary pollution. The voltage, initial concentration and flowrate had effect on fluoride removal efficiency. When initial concentration was 2.4mg/L and flowrate was 10mL/min, compared with adding 2V, the adsorption rate of fluoride at voltage of 4V was increased 26.1%. When voltage was 4V and flowrate was 10mL/min, compared with 1.6mg/L, the residual fluoride concentration at initial concentration of 2.4mg/L was increased 0.3995mg/L. When the initial concentration was 2.4mg/L and voltage was 4V, compared with 30mL/min, the adsorption rate of fluoride at flowrate of 10mL/min was increased 25.2%. So if voltage was increased and initial concentration and flowrate were decreased respectively, the removal efficiency of fluoride could be increased. The effluent fluoride concentration could meet the requirement of drinking water standards. Moreover the equipment was simple, and the industrialization was easy to be realized. It had the broad application prospect.