Electrodeionization: An Efficient Way for Removal of Fluoride from Tap Water Using an Aluminum Form of Phosphomethylated Resin

Abstract

A unit is developed for the continuous production of fluoride free water using an electrodeionization (EDI) process. The experiments are carried out with a laboratory-scale unit. The EDI process usually operates in two regimes of enhanced transfer and electroregeneration. The current efficiency decreased in the second regime of the EDI system because of water dissociation. The cation-exchange membrane (CEM) and anion-exchange membrane (AEM) used for the present study are converted from a styrene–divinylbenzene-based interpolymer film by sulfonation and chloromethylation, respectively. Methyl methacrylate–ethylene glycol dimethacrylate-based amphoteric resin synthesized by radical suspension polymerization shows a 4.57 mequiv/g ion-exchange capacity with 57% water uptake. Both the membranes and resins are characterized by the means of chemical and mechanical properties. The membranes and resins show very good electrochemical properties with excellent mechanical stability. The removal of fluoride from three concentrations of tap water streams revealed the significance of the water composition on the performance of the EDI unit with respect to the selectivity of fluoride removal and energy consumption. Three potentials (9, 12, and 15 V/cell pair) are applied in different sets of experiments during EDI, out of which 12 V/cell pair was found to be more efficient with a lower power consumption of 4.6 kwh/kg and 37% current efficiency.