Electrically Breaking Down Brine Water

Brine is well known to be salty water most often associated with the sea. But many different industrial processes produce brine and it can be a very serious pollutant. An increase in water salt levels of just a couple of percent can kill off all local wildlife and so precautions must be taken in order to desalinate the water to reduce its environmental effect. As I mention here, in a previous post on desalinating water, reverse osmosis is the most common method used it is even used on most modern ships that need to stay sailing for an extended period. But this osmosis, despite being great for sea water, begins to become inefficient when dealing with really high levels of salt such as in brine.  And now to go with the graphene filtration there is another option now open for the filtering of these liquids.

The new idea is  a development in the topic of electrodialysis. In electrodialysis two semi-permeable membranes, one for cations (positive charged) and one for anions (negative charged), are aided by an electric field which acts as an increased bias for the ions to pass through the filtration membranes. Often this method is thought of as only being viable for low salt concentration filtration but since brine is quite conductive it lends itself towards an electrical approach. The concept that has been developed is that of creating membranes that are described as concentration polarised. This means the boundaries of the membrane favour some ion transport over others and creates a net concentration gradient in a certain direction so long as energy is supplied akin to active transport. This method seems very promising as so far experiments have shown a reduced rate of membrane fouling (the blocking of the pores) the bane of membrane filtration.


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