I recently stumbled upon this news,

seawater contains 47 minerals and metals. Starting with the most abundant and proceeding to the least abundant, these are chloride, with a concentration of 18 980 parts per million (ppm) in seawater, sodium (10 561 ppm), magnesium (1 272 ppm), sulfur (884 ppm), calcium (400 ppm), potassium (380 ppm), bromine (65 ppm), inorganic carbon (28 ppm) and strontium (13 ppm). Then follow boron (4.6 ppm), silicon (4 ppm), organic carbon (3 ppm), aluminum (1.9 ppm), fluorine (1.4 ppm), nitrogen in the form of nitrate (0.7 ppm), organic nitrogen (0.2 ppm), rubidium (0.2 ppm), lithium (0.1 ppm), phosphorous in the form of phosphate (0.1 ppm), copper (0.09 ppm), barium (0.05 ppm), iodine (also 0.05 ppm), nitrogen in the form of nitrite (also 0.05 ppm) and nitrogen in the form of ammonia (once more 0.05 ppm). Thereafter, we have arsenic (0.024 ppm), iron (0.02 ppm), organic phosphorous (0.016 ppm), zinc (0.014 ppm), manganese (0.01 ppm), lead (0.005 ppm), selenium (0.004 ppm), tin (0.003 ppm), caesium (0.002 ppm), molybdenum (also 0.002 ppm) and uranium (0.0016 ppm). Then come gallium (0.0005 ppm), nickel (also 0.0005 ppm), thorium (also 0.0005 ppm), cerium (0.0004 ppm), vanadium (0.0003 ppm), lanthanum (also 0.0003 ppm), yttrium (also 0.0003 ppm), mercury (once more 0.0003 ppm), silver (also 0.0003 ppm), bismuth (0.0002 ppm), cobalt (0.0001 ppm) and, finally, gold (0.000008 ppm). Altogether, there are some 50 quadrillion tons (that is, 50 000 000 000 000 000 t) of minerals and metals dissolved in all the world’s seas and oceans.

Which is quite surprising for me (thought those white crystal was only NaCl)

Assuming I already have TONS of general salts (mixed) from simple seawater evaporation, is there any way to separate each mineral? Let's say by pouring the salts in magnet (for material that is having magnetic properties), etc

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(lithium salt pond, which seen exactly same as Nacl pond)

Apologize for shallow understanding of the topic. Any suggestion is highly appreciated since I can't find the answer elsewhere

P.S: This question have been posted earlier in Physics

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    $\begingroup$ I believe you will need to find properties that differentiate the constituents. For example, density, solubility, reactivity, melting point, boiling point, etc. You will then have to apply a sorter that differentiates on one of these factors. Many of the constituents will be physically or chemically bonded so you may need to grind or react the salt to separate these things. $\endgroup$ – Drew Nov 14 '20 at 4:31
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    $\begingroup$ Perhaps posting in Chemistry would have been smarter... $\endgroup$ – Solar Mike Nov 14 '20 at 5:18
  • $\begingroup$ SolarMike @Drew Thank you for the valuable input & suggestion! $\endgroup$ – talkingpandas Nov 14 '20 at 12:50
  • $\begingroup$ Is there a way to do this? Yes. Each item might require a different method. Few will be cost-effective. This question is just too broad to answer. $\endgroup$ – Tiger Guy Nov 21 '20 at 3:38
  • $\begingroup$ Extracting the minerals & metals from sea salts is possible, but it would be better to extract them from sea water, whilst dissolved than from dry salt. Most extractive primary metallurgical & chemical processes involve liquids. The reason why it hasn't been done on a commercial basis is due to the number of processes that would be needed but mainly because the extremely low concentrations of minerals & metals in sea water make it uneconomic to do so. $\endgroup$ – Fred Nov 21 '20 at 9:54

There are two common techniques. The first is "crystallization separation", which takes advantage of the fact that not all species of salt precipitate out of aqueous solution in the same range of concentrations and temperatures, so one can try to manipulate the temperature and concentration (through evaporation) of the aqueous solution into a range where the salt that one considers a valuable product precipitates out, but some or all of the unwanted salts stay in solution. (This also happens naturally, in the formation of evaporite sequences.) The second is "flotation separation", which takes advantage of the fact that, when an aqueous solution is concentrated enough for salts to be precipitating out, the solution is dense enough for some of the less dense solid salts to float to the top of the water column as they precipitate (particularly if they can be attached to air bubbles by the addition of a small quantity of a hydrophobic organic chemical that preferentially attaches to one species of solid salt rather than another), whereas other solid salts are denser and sink to the bottom. However, both methods leave one with a strong aqueous solution of the unwanted salts, which can be an environmentally hazardous waste if not handled carefully.

I first learned about these two techniques from Garrett (1996), Potash: deposits, processing, properties and uses, Chapman & Hall, but I have a feeling that book is quite hard to get hold of.

  • $\begingroup$ This is new, thank you (in most cases it's always been suggested to use mineral-specific filtration membrane). But I am looking for possibilities to separate them all when they are already in solid state, not aqueous. Any reference i could look at? $\endgroup$ – talkingpandas Nov 14 '20 at 21:27
  • $\begingroup$ The two techniques I mentioned are frequently used for salt mixtures initially in solid state, by dissolving them in water first. $\endgroup$ – Daniel Hatton Nov 14 '20 at 22:19
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    $\begingroup$ As for references: I checked, and Google Books' preview will show you a lot of the content of the above-mentioned book by Garrett. The same is true of Bartlett (1998), Solution mining: leaching and fluid recovery of materials, Gordon and Breach Science Publishers. And if you're a member of a library with the appropriate subscription, you could try Titkov (2004), Int. J. Miner. Process. **74**(1-4): 107-123. $\endgroup$ – Daniel Hatton Nov 14 '20 at 22:26

Sea water contains every element found on earth. Very few are present in concentrations that makes it economical to extract . Magnesium is one if the few that is practical to collect.


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