Electrolytic Process to Produce Sodium Hypochlorite Using NaSICON Ceramic Membranes

79513S Sodium hypochlorite is an industrial chemical that is produced with technologies that rely on organic membranes and undivided cell methods, which have performance limitations from fouling and limited selecivity. This project will develop an innovative and energy efficient, low temperature, cost-effective, and environmental friendly electrochemical process that uses a sodium-ion-conducting membrane to continually produce sodium hypochlorite from sea water and low purity, unsoftened water and sodium chloride. The new membranes will exhibit high selectivity towards sodium ions over hydronium and alkali ions, providing greater than 90% sodium transport efficiency, with better ion transfer selectivity and better resistance to fouling. Phase I will (1) demonstrate the electrochemical performance and chemical stability of the ceraminc membranes to produce higher concentration of sodium hypochlorite on a laboratory scale; (2) synthesize several candidate membranes compositions and evaluate them for chemical stability in sea water, sodium chlorite, and sodium hypochlorite; (3) evaluate the ability of prototype cells with the ceramic membranes to produce sodium hypochlorite as a function of process conditions (i.e. voltage, current density, temperature, effluent flow rate, and corrosion resistance); and (4) determine process economics and balance of plant cost estimates. Commercial Applications and Other Benefits as described by the awardee: The membrane technology should permit the scale-up of a process that uses seawater and a salt solution prepared from un-softened water to make a high concentration of sodium hypochlorite, without causing the calcium and magnesium present in these waters to precipitate out in as hydroxides (an unpreventable outcome when making hypochlorite with existing technology). The advantages of this technology would include (1) no forced shut down of the operation for cleaning, saving time and money; (2) no short-circuiting of electrodes due to precipitates accumulating between them, enhancing safety; and (3) no waste generation, the unwelcome consequence of cleaning scale from the equipment with hydrochloric acid.