Fresh from sea-water ... and hydrogen too

 

Malta always had a water problem.  Every living being needs water to survive, and man is no exception.  The country is not endowed with consistent natural rivers, and along the times gathered water from wells, looked for streams out of rocks and dug holes in the ground, to be able to drink along with his animals, cook, irrigate.

 

With a growing population, usage grew commensurately, and the amount of holes in the ground increased, became deeper and so much water was extracted that some streams dried up, and the water raised started being salty such that it was hardly potable any longer.

 

Desalination entered into the picture, that is the production of fresh water from sea water.  The first type was distillation, where sea water is heated until boiling, steam rises leaving behind the salt that remains in water more and more concentrated.  The steam rises until it meets a cool surface, condenses and is gathered as fresh water.  The first such plant started in 1966.  This is a very expensive plant to run, as all the water that needs to be so procesed has to be boiled, which is very energy intensive.

 

An innovative version of this process is reverse osmosis.  Imaging having salt water on the left of, and less salty water on the right of a membrane.  In normal conditions of temperature and pressure, there will be a tendency for water to pass from the right to the left, through the pores of the membrane, until the water on both sides have the same salt content.  This process is osmosis.

 

In reverse osmosis, the more salty side is compressed, with the effect that water flow in the membrane is reversed, that is the salty side becomes even more salty as the water has the tendency of seeping to the other side.

 

Malta has several plants of this type, the first built at Għar Lapsi in 1982,1 and for many years was well known in the world as a laboratory for this technology.

 

Recently I was reading about an interesting development for this technology, which could potentially be used also for the production of hydrogen, a simple element, the first produced in the universe, and also a fuel being mentioned as having an important role on this earth in the fight against climate change.

 

Researchers have announced having found a different use for reverse osmosis membranes in electrolysis, that is the production of hydrogen and oxygen from water and electrical current.  Up to now, the production of these gases needed fresh water, as sea water couldn’t be used due to the parallel production of chlorine, with is a toxic gas (salt chemically consists of sodium and chlorine).

 

The researchers found that oxygen is produced on the positive side (anode) and hydrogen on the negative side (cathode) as happens normally during electrolysis, but chlorine can be prevented from passing from one side to the other, which happens during conventional electrolysis, by a reverse osmosis membrane.  This is a huge advantage.2

 

So far, in this research the membrane is only used for electrolysis, not also to produce fresh water at the same time.  Nevertheless, if this research is commercialised, Malta with its experience in the field of reverse osmosis and its limitless resources of sea water, can make use of this technology as a new industry if combined with a renewable source of energy.

I would follow such a development with great interest.

 

1https://www.wsc.com.mt/about-us/our-history/, retrieved 10/6/2021

2https://acapmag.com.au/2020/09/generating-renewable-hydrogen-fuel-from-sea/, retrieved 10/6/2021