Control of hard water scaling in electrochemical cells

Abstract

A threshold agent composition and methods of using the same to produce hypochlorite and other effluent streams from an electrochemical cell without the detrimental effects of hard water scaling are disclosed. The invention further discloses use of chemistries to prevent hard water scale formation in various electrochemical cells to enhance cell longevity without decreasing chlorine, hypochlorite or other effluent production.

Description

FIELD OF THE INVENTIONThe invention pertains to the field of water electrolysis and more particularly, threshold agent compositions and methods of use for preventing hard water scale formation in electrochemical cells to enhance cell longevity. In particular, hard water scale formation is prevented through the use of a threshold agent without having to soften the water source for the electrochemical cell or cause any decrease in the production rate of sodium hypochlorite or other effluent from an electrochemical cell.BACKGROUND OF THE INVENTIONElectrolysis as a water treatment process produces two forms of altered water: a reduced or alkaline water; and an oxidized or acidic water. Electrolysis uses an electric current to split water into its two constituent elements: hydrogen and oxygen. Electricity enters the water at a cathode, a negatively charged terminal, passes through the water and exits through an anode, a positively charged terminal. Hydrogen is collected at the cathode (n...

AI Technical Summary

Benefits of technology

The present invention relates to electrochemical processes for the production of sodium hypochlorite and other effluent sources with the use of threshold agents to prevent hard water scale formation in electrochemical cells to enhance cell longevity. According to an aspect of the invention, a method for producing hypochlorite and reducing hard water scaling in an electrochemical cell without decreasing hypochlorite production includes obtaining an electrochemical cell configured with at least one anode and cathode to produce a hypochlorite source, providing a water and a sodium chloride source to the cell, adding a threshold agent to the cell, and applying an electric current the cell to produce hypochlorite and reduce hard water scaling without decreasing hypochlorite production. In a further aspect of the invention, the threshold agent is added in the amount of up to about 10,000 ppm and is a water soluble polycarboxylate capable of preventing hard water scale formation on electrodes and membranes.

According to still further aspects of the invention the threshold agent may be added in the amount of up to about 1,000 ppm or in the amount of from about 50 ppm to about 500 ppm. The threshold agent may have a molecular weight less than 5,000, preferably less than 2,000. Preferably, the hypochlorite produced according to embodiments of the invention effectively cleans and / or sanitizes surfaces without depositing streaks or spotting.

Problems solved by technology

The effectiveness and convenience of utilizing electrolysis systems are frequently limited due to the failure of the electrodes and membranes of the cells caused by both corrosion and hard water scaling.

Most often, calcium and magnesium ions are contained in either the water source or salt solutions added to electrochemical cells, resulting in the previously considered unavoidable scaling in cells, resulting in detrimental effects to the cells by forming hydroxide precipitates and scale.

The precipitate and scale eventually coat the surface of the electrodes and membranes causing an increased voltage demand by the cell and may potentially lead to short-circuiting of the cell.

Therefore, a significant disadvantage to the use of electrochemical cells, such as for the production of hypochlorite, is the required use of softened water to prevent hard water scaling.

This is undesirable as acids are very corrosive and may erode the electrodes, specifically the electrode coatings.

However, these and other means of maintaining and repairing electrochemical cells are undesirable and costly for consumers.

Despite the various means for preventing scaling and corrosion, eventually the electrochemical cells become permanently fouled or ineffective, requiring consumers to pay for expensive maintenance and repairs and / or replacement.

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