Extracting other mineral from salt in evaporated seawater

Question

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 $\pu{18 980 ppm}$ (parts per million) in seawater, sodium ($\pu{10 561 ppm}$), magnesium ($\pu{1 272 ppm}$), sulfur $(\pu{884 ppm})$, calcium ($\pu{400 ppm}$), potassium ($\pu{380 ppm}$), bromine ($\pu{65 ppm}$), inorganic carbon ($\pu{28 ppm}$) and strontium ($\pu{13 ppm}$). Then follow boron ($\pu{4.6 ppm}$), silicon $(\pu{4 ppm})$, organic carbon ($\pu{3 ppm}$), aluminum ($\pu{1.9 ppm}$), fluorine ($\pu{1.4 ppm}$), nitrogen in the form of nitrate ($\pu{0.7 ppm}$), organic nitrogen ($\pu{0.2 ppm}$), rubidium ($\pu{0.2 ppm}$), lithium ($\pu{0.1 ppm}$), phosphorous in the form of phosphate ($\pu{0.1 ppm}$), copper $(\pu{0.09 ppm})$, barium ($\pu{0.05 ppm}$), iodine (also $\pu{0.05 ppm}$), nitrogen in the form of nitrite (also $\pu{0.05 ppm}$) and nitrogen in the form of ammonia (once more $\pu{0.05 ppm}$). Thereafter, we have arsenic ($\pu{0.024 ppm}$), iron ($\pu{0.02 ppm}$), organic phosphorous $(\pu{0.016 ppm})$, zinc $(\pu{0.014 ppm})$, manganese ($\pu{0.01 ppm}$), lead ($\pu{0.005 ppm}$), selenium ($\pu{0.004 ppm}$), tin $(\pu{0.003 ppm})$, caesium ($\pu{0.002 ppm}$), molybdenum (also $\pu{0.002 ppm}$) and uranium ($\pu{0.0016 ppm}$). Then come gallium ($\pu{0.0005 ppm}$), nickel (also $\pu{0.0005 ppm}$), thorium (also $\pu{0.0005 ppm}$), cerium ($\pu{0.0004 ppm}$), vanadium $(\pu{0.0003 ppm})$, lanthanum (also $\pu{0.0003 ppm}$), yttrium (also $\pu{0.0003 ppm}$), mercury (once more $\pu{0.0003 ppm}$), silver (also $\pu{0.0003 ppm}$), bismuth ($\pu{0.0002 ppm}$), cobalt $(\pu{0.0001 ppm})$ and,finally, gold ($\pu{0.000008 ppm}$). Altogether, there are some 50 quadrillion tons (that is, $\pu{50 000 000 000 000 000 tons}$) 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 $\ce{NaCl}$)

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

(lithium salt pond, which seen exactly same as $\ce{NaCl}$ 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

Answer 1

One material extracted from seawater is magnesium.

In the United States, magnesium is obtained principally with the Dow process, by electrolysis of fused magnesium chloride from brine and sea water [emphasis added]. A saline solution containing $\ce{Mg^{2+}}$ ions is first treated with lime (calcium oxide)[sic; calcium hydroxide would seem more likely] and the precipitated magnesium hydroxide is collected:

$\ce{Mg^{2+}(aq) + CaO(s) + H2O → Ca^{2+}(aq) + Mg(OH)2(s)}$

The hydroxide is then converted to a partial hydrate of magnesium chloride by treating the hydroxide with hydrochloric acid and heating of the product:

$\ce{Mg(OH)2(s) + 2 HCl → MgCl2(aq) + 2H2O(l)}$

The salt is then electrolyzed in the molten state. At the cathode, the Mg2+  ion is reduced by two electrons to magnesium metal:

$\ce{Mg^{2+} + 2 e^− → Mg}$