Many places in the world are turning to large scale desalination. These places tend to be dry. Desalination produces lots of brine, which must be disposed of. But this brine offers an opportunity.
People have talked for 100 years about mining the sea for gold. The problem: the gold is in dilute solution and one must process lots of seawater. Nuclear desalinators are taking care of that piece by processing lots of seawater, and retaining the water.
I propose the residual brine be allowed to dry in the sun. How then to separate the wheat from the chaff - the valuable minerals from the common salts?
I propose that this be done just like the 49ers did it: gravity. The valuable minerals are heavier than sodium and calcium, even if present as salts. Sifting and gently shaking a mix of particulate salts will cause the heavier particles to migrate downwards, displacing lighter particles upwards. Ultimately the bottom stratum of precipitated brine will be enriched for valuable stuff.
I here assert that this double concentration product will be rich enough in valuable elements to be worth the subsequent step of extraction, which will be done according to established methods for the respective minerals.-- bungston, Jan 13 2016 Highly efficient heavy metal ions filter https://www.ethz.ch...al-ions-filter.html"ETH researchers have developed a new water filtration system that is superior to existing systems in many respects: it is extremely efficient at removing various toxic heavy metal ions and radioactive substances from water and can even be used in gold recovery." [notexactly, Jan 28 2016] One of the [old and deprecated] techniques for extracting gold involved the use of mercury, because it can dissolve gold (and some other metals that might be present). So, pouring your salt through a mercury bath, and later distilling the mercury to recover dissolved stuff, is old tech. But since there is always mercury that escapes this process cycle, and starts poisoning the environment, that is why it is deprecated (but still in use in numerous places)-- Vernon, Jan 13 2016 And what will you do with the remaining mountain of junk ?-- piluso, Jan 14 2016 chuck it in the sea, I guess.-- pocmloc, Jan 14 2016 Seems to me that the energy required to dispose all that salt would be more expensive that the money you can get from this process.-- piluso, Jan 14 2016 From a random site found through googling: ::Each liter of seawater contains, on average, about 13 billionths of a gram of gold.::
Also, from wikipedia: ::Seawater has a salinity of roughly 35,000 ppm, equivalent to 35 grams of salt per one liter (or kilogram) of water.::
So after removing all the water you have 13 billionths of a gram of gold per 35 grams of stuff.
So the amount of gold is : 13 * 10^-9 / 35, or 0.0000000037 grams/gram.
A third random site says this: ::A lower grade gold ore would contain something like 5 grams per tonne (5 parts per million).::
That is, 0.000005 grams/gram.
So this will be viable if your proposed method is about 1350 times more efficient than standard gold mining. To be honest I doubt that gravity panning is.-- Loris, Jan 14 2016 " propose that this be done just like the 49ers did it "
What, by passing to Jerry Rice a lot ?-- normzone, Jan 14 2016 //I propose that this be done just like the 49ers did it: gravity. The valuable minerals are heavier than sodium and calcium, even if present as salts.//
The only problem with that statement is that it's wrong. Gold in seawater is not present as little flakes or micro-nuggets; it's present as dissolved gold salts. When the water is removed, the gold salts will co-crystallize with more abundant salts, since there isn't enough gold salts to crystallize on its own.
However, setting aside the problems of very low gold concentration and no good way to recover it, this is a viable idea.-- MaxwellBuchanan, Jan 14 2016 Maybe Vernon's method is the way to go: pour mercury thru salt pile, recover mercury, rinse, repeat.-- bungston, Jan 14 2016 Won't work for the reasons above - mainly the huge tonnages of NaCl to sort through. I already evaporate large quantities of seawater through solar evaporation and have some large centrifuges which would be a more effective way of going about a concept that won't work.-- AusCan531, Jan 15 2016 So this is about as viable as recovering gold from fingernails?-- notexactly, Jan 15 2016 Almost.-- MaxwellBuchanan, Jan 15 2016 Centrifugation: yes. And not the dried stuff; still in solution. Cesium chloride can produce a gradient when centrifuged. I predict a few spins of the centrifuge will cause the heavier ions to migrate outward, forcing the light NaCl inwards. As the concentration of gold salts at the outer edge of the centrifuge increases it will exceed solublity and precipitate out. One need only open a valve in the centrifuge to allow the gold (also platinum, iridium, thorium etc) to squirt out and be captured in a special cup.-- bungston, Jan 16 2016 Pretty sure the going price for sea salt exceeds the value of the gold recoverable.-- MechE, Jan 17 2016 That sea salt thing is such a racket. Artificial scarcity.-- bungston, Jan 17 2016 My guess is that urine or sewage contain more of value than the slightly saltier output of a reverse osmosis desalination unit.
"The engagement is off John". she says. John's hands miss the thrown ring and the "cubic zirconia and gold token" rolls into the flooding storm sewer.
Las Vegas is the place to distill the sewage.-- popbottle, Jan 17 2016 //That sea salt thing is such a racket. Artificial scarcity//
That depends. Ordinary salt heaped up on the bank of a salt lake or the ocean is literally worth less than dirt i.e. a tonne of topsoil is worth more than a tonne of raw salt. However, if you want to make tremie crystal or 'flake' salt, (Maldon, Murray River Pink Salt, etc) that is a process which costs takes a lot of energy, time and labour. In other words it costs a f*ck of a lot to make one tonne of flake salt.
If you're talking about bog standard crystal salt which is harvested, rinsed once or twice to remove excess magnesium and calciums, then packaged in some twee little containers marked 'natural', 'organic' 'gluten-free' sea salt then marked up hugely, Yes, what a racket.-- AusCan531, Jan 18 2016 ^Roger that [bigs].-- AusCan531, Jan 18 2016 //rinsed once or twice to remove excess magnesium and calciums,//
You wouldn't want to miss an opportunity to sell the magnesium and calcium separately as supplements. I hear the modern diet is deficient in.... (insert by-product)-- bs0u0155, Jan 28 2016 I am pondering differential solubility and whether I might be making this up entirely.
1: Imagine water which is saturated in solute F. More solute F will not go into solution.
2: Imagine now solute E which is more soluble than solute F. I here assert that if one adds E to the saturated solution of F, it will drive F out of solution to make room for E. Eventually all the F will be out of solution. Or maybe there will be some F left after the solution is saturated for E; not sure. In any case, F is driven out.
3: Perhaps solute E is something like isobutanol. Adding it to a water solution not only takes up available water molecules but the remaining solution also has less solvating power for ions. After driving out the F ion, the isobutanol can be distilled out of the water and reclaimed.
I propose that differential solubility like this could be used to sort out a mix of ions, separating the wheat from the chaff; yes the wheat from the chaff. Saving the sparkling golden crystals of wheat. The chaff (aka mountain of junk) will be cast into delightfully ornamental bricks and used to build obelisks, sphinxes and other long awaited monuments on the BUNGCO campus.-- bungston, Feb 16 2016 random, halfbakery