Desalination via electrochlorination etc

[JacksinPA]

Electrochlorination - Wikipedia

en.wikipedia.org

I watched a YouTube video on water desalination last night & got me to thinking. Electrolysis of pure water gives hydrogen & oxygen. Electrolysis of salt water, per https://en.wikipedia.org/wiki/Electrochlorination, is called electrochlorination.

A low voltage DC current is applied, electrolysis happens producing sodium hypochlorite and hydrogen gas (H2). The solution travels to a tank that separates the hydrogen gas based on its low density. [1] Only water and ordinary salt, (sodium chloride (NaCl)) are used. The chemical reaction is:

NaCl + H2O + ENERGY → NaOCl + H2

NaOCl is sodium hypochlorite which has value as the chemical product bleach.

I'm sure this is not original, but the hydrogen gas produced can be 'burned' in air to make pure water. So sea water & electricity go in & bleach & pure water come out.

An ideal location for such an operation is on the coast near a volume consumer of bleach, which could be supplied via pipeline. NaOCl could also be converted into other value-added products. For example, terminal alkenes react with bleach to form 1-chloro-2-hydroxy derivatives. Bleach converts primary alcohols into aldehydes & secondary alcohols into ketones. Bleach is a useful oxidizing agent in many syntheses.

How efficient this process would be compared to current desalination plants is not known to me as there are too many factors involved. But one advantage is environmental: there would be no discharge of waste brine back into the ocean. These hypersaline waste streams from current desalination plants do a lot of damage to the marine life in the area.

 

[MamboDervish]

I watched a YouTube video on water desalination last night & got me to thinking. Electrolysis of pure water gives hydrogen & oxygen. Electrolysis of salt water, per https://en.wikipedia.org/wiki/Electrochlorination, is called electrochlorination.

NaCl + H2O + ENERGY → NaOCl + H2

NaOCl is sodium hypochlorite which has value as the chemical product bleach.

An ideal location for such an operation is . . . . .

Amazingly, NaOCl is actually used in wastewater treatment plants to purify, disinfect, and reduce odor in waste water - i.e. sewage - before releasing it back into the environment. And wastewater treatment plants are in every coastal metropolitan area in the country, so finding a use for it will never be a problem. The desalination plant can be put right next to the turd works, and the pumps can be driven by the Methane from the digester tanks.

 

[Antiwar]

I'm not sure I understand the point. The Wikipedia page says electrochlorination is a better way (than chlorination) to treat water for drinking. I believe electrolysis takes a lot of energy. You want to recombine the hydrogen with oxygen to produce drinking water?

Wiki:
Drinking Water
Water treatment plants have evolved their technology over the years to tackle health threats due to water contamination eg cholera, typhoid, and dysentery. Treatment plants began to implement chlorination. Chlorination virtually wiped out both the spread and initial contamination of these diseases, and did so in a way that earned it the title of "the most significant public health advance of the millennium” from Life Magazine.[4][3]



Electrochlorination is the next step in the evolution of this process. It chlorinates drinking water without producing environmental toxins. Unlike other chlorination techniques, electrochlorination generates no sludge or by-products other than hydrogen which must be managed safely. It is safer for the operators of the chlorinators as there is no handling of chlorine gas, which is highly toxic and corrosive. A risk assessment is required as hydrogen released is flammable & explosive.[3]

 

[JacksinPA]

I'm not sure I understand the point. The Wikipedia page says electrochlorination is a better way (than chlorination) to treat water for drinking. I believe electrolysis takes a lot of energy. You want to recombine the hydrogen with oxygen to produce drinking water?

Wiki:
Drinking Water
Water treatment plants have evolved their technology over the years to tackle health threats due to water contamination eg cholera, typhoid, and dysentery. Treatment plants began to implement chlorination. Chlorination virtually wiped out both the spread and initial contamination of these diseases, and did so in a way that earned it the title of "the most significant public health advance of the millennium” from Life Magazine.[4][3]



Electrochlorination is the next step in the evolution of this process. It chlorinates drinking water without producing environmental toxins. Unlike other chlorination techniques, electrochlorination generates no sludge or by-products other than hydrogen which must be managed safely. It is safer for the operators of the chlorinators as there is no handling of chlorine gas, which is highly toxic and corrosive. A risk assessment is required as hydrogen released is flammable & explosive.[3]

 

[JacksinPA]

My proposal is to use the elerctrochlorination process to make both bleach & hydrogen. The hydrogen is then 'burned' in air to produce pure water. The possible advantage going this way is avoiding the need to discharge extremely salty brine back into the ocean. Large water purification facilities could be consumers of the bleach.

 

[JacksinPA]

I'm not sure I understand the point. The Wikipedia page says electrochlorination is a better way (than chlorination) to treat water for drinking. I believe electrolysis takes a lot of energy. You want to recombine the hydrogen with oxygen to produce drinking water?

Wiki:
Drinking Water
Water treatment plants have evolved their technology over the years to tackle health threats due to water contamination eg cholera, typhoid, and dysentery. Treatment plants began to implement chlorination. Chlorination virtually wiped out both the spread and initial contamination of these diseases, and did so in a way that earned it the title of "the most significant public health advance of the millennium” from Life Magazine.[4][3]



Electrochlorination is the next step in the evolution of this process. It chlorinates drinking water without producing environmental toxins. Unlike other chlorination techniques, electrochlorination generates no sludge or by-products other than hydrogen which must be managed safely. It is safer for the operators of the chlorinators as there is no handling of chlorine gas, which is highly toxic and corrosive. A risk assessment is required as hydrogen released is flammable & explosive.[3]

One of the advantages of the electrochlorination POV is that there is no very salty brine formed as a byproduct & that has to be dumped back into the ocean. And yes, not having to handle the war gas chlorine is another advantage. Thanks for pointing it out.

 

[JacksinPA]

I'm not sure I understand the point. The Wikipedia page says electrochlorination is a better way (than chlorination) to treat water for drinking. I believe electrolysis takes a lot of energy. You want to recombine the hydrogen with oxygen to produce drinking water?

Wiki:
Drinking Water
Water treatment plants have evolved their technology over the years to tackle health threats due to water contamination eg cholera, typhoid, and dysentery. Treatment plants began to implement chlorination. Chlorination virtually wiped out both the spread and initial contamination of these diseases, and did so in a way that earned it the title of "the most significant public health advance of the millennium” from Life Magazine.[4][3]



Electrochlorination is the next step in the evolution of this process. It chlorinates drinking water without producing environmental toxins. Unlike other chlorination techniques, electrochlorination generates no sludge or by-products other than hydrogen which must be managed safely. It is safer for the operators of the chlorinators as there is no handling of chlorine gas, which is highly toxic and corrosive. A risk assessment is required as hydrogen released is flammable & explosive.[3]

My thought is using the plant to make both bleach & water with no brine waste product that needs to be disposed of in the ocean.

 

[JacksinPA]

One problem with my idea is getting rid of all the heat produced in the conversion of hydrogen & atmospheric oxygen to water. Depending on scale, there could be enough heat energy in the steam to drive a generator turbine, providing 'free' electricity for the plant.