Removal of co-existing fluoride, calcium, magnesium, and carbonates, by non-chemical induced electrolysis system for drinking and industrial purposes

An electrolysis (ELC) system was proposed to remove co-existing F−, Ca2+, Mg2+, CO32−, and HCO3− from groundwater without the addition of any chemicals. The proposed system utilized an ELC cell composed of non-corrosive platinum and stainless steel electrodes. Ion removal mechanisms, performance against different ion concentrations, and charge loading were studied and compared with drinking and industrial water quality guidelines. System performance with real groundwater was also examined. Results revealed that ELC effectively removes (CO32− + HCO3−) in the anode as CO2, and (CO32− + HCO3−), Ca2+, and Mg2+ in cathode as MgCO3, CaCO3, and Mg(OH)2. F− was removed by co-precipitation with Mg(OH)2 and Coulomb transfer. Maximum removal of 58%-F−, 42%-Ca2+, and 95%-Mg2+ were observed at a charge loading of 1500 C/L. With increasing Ca2+ and Mg2+, removal increments of cathode F−, Ca2+, Mg2+, and (CO32− + HCO3−) were noticed. To meet drinking water guidelines value of 1.5 mg/L of F−, minimum initial ion concentration ranges should be within F− < 4.29–6 mg/L, Mg2+ < 75–125 mg/L, Ca2+ > 50 mg/L, and (CO32− + HCO3−) < 10–0 mmol/L for 1500 C/L. The anode delivered the quality water which meets industrial boiler water alkalinity guideline for the initial (CO32− + HCO3−) < 12.5 meq/L. The community-scale treatment system established in Sri Lanka confirmed smooth operation with a higher removal of F− and Ca2+ in the cathode and (CO32− + HCO3−) in the anode which can be slightly approximated with laboratory results.