Why is it so difficult to make water drinkable from the salty oceans?
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Correct me about the chemistry part but water being a polar solvent breaks down salt into its component sodium and chloride. Not to mention the other diluted minerals suspended within ocean water. (whale pee being one of them lol)
Now, breaking down that bond back into H2O and NaCl is really energy intensive. So it’s either you use insane amounts of pressure to filter ocean water through a membrane that only lets molecular water pass through (reverse osmosis) OR you apply a lot of heat to boil the water component into steam while leaving the heavier salts behind, producing brine (distillation).
Both processes give you distilled water that has to be filtered again (just to make sure), and then remineralized (because drinking distilled water straight ain’t good for you)
The water and salt is sort of chemically bonded to each other. Not through regular covalent bonds but through ionic bonds using Van Der Waals forces. But the principle is the same. You need to break apart these bonds which require energy. There are a few ways to do this but they all require quite a bit of energy in order to brake these bonds to get the salt out of the water.
There are a number of desalination plants around the world providing clean drinking water to coastal areas. But they all suffer from the issue of requiring huge amounts of energy which means the water they make is quite expensive. If drinking water is available even hundreds of miles away it is cheaper to build and operate an aqueduct then a desalination plant.
It’s not difficult per se, it’s just very expensive, both in terms of money and in terms of energy used, especially if you intend to do it on a large scale. Countries wealthy enough to afford mass-desalination usually also have other sources of water available, like reservoirs, lakes and whatnot. Countries that don’t have other sources of water, for example those in desert climates, usually aren’t wealthy enough to afford mass-desalination. There are a few exceptions, if you look up mass desalination plants you’ll find they mostly occur in countries that are wealthy _and_ desert-like, like Saudi Arabia and the UAE.
It’s not difficult, just more expensive. Big ships, for instance, often have fresh-water generators for onboard drinking water.
It takes a lot of energy to separate the salt from the water. Energy is expensive. It’s not that complicated though—one method can even be done at home.
Take salt water. Put it in a heat-proof container with an open top, but don’t fill it too full—leave a few inches of space. Over the salt water container, place a top that slants to one side with the lower end of the slant going past the edge of the container, making sure there is a gap between the lower end of the top and the edge of the container. Cover over any holes with aluminum foil besides the gap at the lower edge of the lid. When you boil the salt water in the container, fresh water will condense on the lid and slide down it out of the gap on the lower edge. This will give you a very basic, very wasteful distillation setup. Using the same equipment as an alcohol distiller will give better results but still take a ton of energy.
It’s not difficult. We can readily remove salt from water, the technology is there and we already do it. Most (all?) naval ships that are out to sea for months at a time actively desalinate seawater for use on the ship.
The issue is (1) it takes huge amounts of energy to desalinate water when we’re already in an energy (pollution) crisis and (2) you need to figure out where to dump all the salt when you’re done without completely destroying local ecosystems, because salt pretty much kills everything.
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