Process and apparatus for removing chloride and sodium ions from an aqueous sodium chloride solution

Abstract

The present invention discloses a process and apparatus for removing sodium and chloride ions from an aqueous sodium chloride solution, such as seawater or brine. The process includes electrolyzing aqueous sodium chloride to remove chloride and sodium ions in the form of chlorine gas and sodium metal. Preferably, a photovoltaic device, such as a triple junction amorphous silicon solar cell, provides the electrical energy for the electrolysis. The process utilizes electrode material that facilitates the production of chlorine gas and inhibits the evolution of hydrogen from the aqueous sodium chloride solution. The sodium is deposited onto a metal surface having a high hydrogen overpotential to produce sodium amalgam. The processed solution from the electrolysis has a reduced sodium chloride content and may be further processed to produce fresh water for human consumption or agricultural purposes. The sodium amalgam is removed from the aqueous sodium chloride solution and transported to and coupled against an air depolarizing fuel cell in water to produce electrical power with the sodium air fuel cell, power that may be used to operate the apparatus or other machinery. The product of the reaction between the sodium amalgam and the fuel cell is sodium hydroxide that may be reacted with the chlorine gas to produce sodium hypochlorite.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a process and apparatus for reducing sodium chloride concentration from an aqueous sodium chloride solution, such as sea water or brine, by removing chloride and sodium ions. More particularly, the present invention discloses a process and apparatus, wherein chloride and sodium ions are removed from the aqueous sodium chloride solution and may be used in subsequent processes. The sodium may be collected and used in the production of power from a sodium-air fuel cell and chlorine gas may be neutralized with the sodium hydroxide produced in the sodium —air fuel cell to produce sodium hypochlorite. BACKGROUND OF THE INVENTION [0002] Water is a precious and life sustaining liquid. Over 97% of the world water supplies are tied up in the ocean. The remaining 3% of the water exists as fresh water supply in natural and man-made lakes and the polar ice caps. With the looming environmental catastrophe brought upon by the global wa...

AI Technical Summary

Benefits of technology

[0021] An embodiment of the present invention provides a process and apparatus for electrolyzing aqueous sodium chloride solution to remove chlorine and sodium ions from the aqueous sodium chloride solution to reduce the salt (NaCl) content of the aqueous sodium chloride solution.

Problems solved by technology

With the looming environmental catastrophe brought upon by the global warming there is already a shortage of fresh water supply in the world.

Many of the developing countries are suffering from the failure of the monsoon and consequently the supply of fresh water in reservoirs.

Although water conservation is clearly beneficial, it is unlikely that it alone will meet the growing water needs of the world.

Although the search for new freshwater resources will continue and new sources will be identified, it is clear that freshwater is a finite resource that is politically contentious and that the most accessible sources have already been located and tapped and are being consumed.

Future sources will become increasingly expensive to both locate and utilize.

Although reverse osmosis is an effective desalination technique, it is slow, expensive and requires high energy consumption.

Related techniques, such as electrodialysis, show improved energy efficiency, but nonetheless remain costly, especially for high volume throughputs.

Anything more than that, such as sea water that may have salt content of 350,000 ppm, would require higher pressures (close to 1000 psi) and the current membranes, in addition to being expensive cannot sustain such high pressures.

It is somewhat expensive but work is being performed to continuously decrease the cost by efficient designs.

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