Mineral Wealth from the Oceans

 

Besides protein in fish and seafood for essential nutrition, how many minerals and elements are there in the oceans? Lots of them.

It is estimated there are 3.9 × 10⁹ (3.9 billion) tons of elements carried annually in solution to the oceans.

Rain is constantly peppering over the dry land on its way to the ocean and, in the process, it dissolves a little bit of all the materials it soaks up. Not all are soluble, many are, some less soluble than others. When the dissolved substances reach the ocean, some less soluble substances make their way to the ocean bottom.

The Earth has been in existence for over 4.5 billion years. In the constant bombardment by rain there would be so many materials washed into the oceans that every element in all known compounds is found in the ocean mixed up with the water molecules.

Scientists who analyze sea waters found there are approximately 3.25 percent of dissolved elements including gold in some 1370×10⁶ cubic km or 1.4522 × 10¹⁷ litres of waters in the oceans. The total weight of solid and dissolved material comes to 50,000 trillion (50,000,000,000,000,000) tons out of which 75 % of them is salt as sodium chloride with a bit of all other elements in the remaining 25 %.

The seafloor holds rich deposits of minerals such as copper, zinc, nickel, gold, silver, magnesium, and phosphorus. These deposits exist as crusts on volcanic and other rocks and as nodules on abyssal plain sediment. They occur typically about 3 to 10 centimetres in size.

The oceans contain vast quantities of other materials that humans use today. However, direct extraction of these mineral resources is limited to salt, magnesium, placer gold, tin, titanium, and diamonds and of course fresh water through desalination in countries like in Arabic countries where fresh water is scarce.

For a start, there are enough magnesium compounds present in the ocean to yield a total of 19 thousand billion (1,900 000 000 000 000) tons of that metal.

Such an ample supply in the ocean is enough to last our human needs an enormous length of time, especially since whatever we extract and use eventually gets washed back into the ocean.

Magnesium is distributed evenly in the ocean unlike pockets of minerals on land. Even with uniform dilutions throughout the ocean, it will take us, working with perfect efficiency, 360 liters of seawater to get a 0.5 kg of magnesium. Advances in extraction methods have allowed us to do this economically, and magnesium is now profitably extracted from sea water in almost any amount we want.

Another element present in substantial quantities in seawater is bromine, a chemical relative to chlorine called halogens.

Under the Mendeleev periodic table, group 7A (or VIIA) are the halogens: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). The name "halogen" means "salt former", derived from the Greek words halo- ("salt") and -gen ("formation").

The sea contains dissolved halogens – besides chlorine as sodium chloride, bromine compounds that would yield a total of a hundred thousand billion (100,000,000,000,000) tons of pure bromine. 

This is about a twentieth of the supply of magnesium, so twenty times as much seawater or about 7000 liters must be searched at perfect efficiency to get nearly 0.5 kg of bromine. This too, can be done cost-effectively, and the sea is a major supplier of the world’s bromine.

The third halogen of chlorine is iodine. This is a rarer element than bromine and chlorine throughout this planet, and it is present in the ocean to less than a thousandth of a quantity of bromine. The total amount of 86 billion tons sounds very impressive, but translated, this is only 0.45 kg of bromine in 7,570,000 liters of sea water.   

This is too little for it to be extracted cost-effectively by direct means.  However, fortunately there is another method to do this for us – the natural way.  Depending on the species, seaweed and brown algae have a very high concentration of iodine. The iodine can be extracted by burning to ash to produce iodide. This can then be oxidised to iodine and recovered by solvent extraction and evaporation.

The most expensive element in seawater is gold.  There is at least one to two grams of gold for every 100 million metric tons of ocean water in the Atlantic and north Pacific. There is also undissolved gold on the seafloor. The ocean is deep, and gold deposits are at least 1.5 km to 3.0 km underwater.

In order to extract gold from sea water, 104 to 125 cubic km, or 104,204,550,000,000 to 125,045,460,000,000 litres of ocean waters will have to be searched and processed in order to yield just 0.45 kg of gold. The cost of doing this is far more expensive than the cost of the gold itself. We might as well give up and leave the gold to rest quietly and in peace the ocean.

What about silver, the next most costly element. The concentration of silver in seawater is between 2 – 100 parts per trillion, averaging at 50 parts per trillion. The total volume of seawater in the world’s oceans is approximately 1370×10⁶ km3 or 1.4522 × 10¹⁷ litres.

The density of seawater is 1.025 kg/L. Hence the mass of ocean water is 1.49 x 10 ¹⁷ kg. Out of every trillion kg of ocean water there is 50 kg of silver. Hence the amount of silver in the ocean is about 7,450,000 kg of silver.   

Many people have tried to extract gold and silver from sea water, but I think the cost of doing so is prohibitive, and hence in my opinion they are not worth the effort.

There is 420 mg of calcium per litre of seawater. Translated, this means there is 6 x 10 ¹³ kg (60 trillion kg) of calcium in the ocean water. One of the main reasons for the abundance of calcium in water is its natural occurrence in the earth's crust, and acidic rain constantly wash calcium off the land into the ocean. Calcium is also a constituent of coral. 

However, nobody attempts to extract calcium from the ocean, as calcium is so cheap and abundant in land such as in limestone hills.

But the cheapest of all is to mine salt from the ocean where hardly any effort needs to be done. The watercourse cuts deep into the land, forming narrow bays and lagoons, and rock mass movements and subsidence cause the seabed to drop steadily. Under these conditions, about 13.6 million years ago, salt deposits were formed automatically for us to reap in abundance. In other words, part of the sea has been cut off by the land depositing the salt on dry land as salt mines.

Fortunately sodium as salt or sodium chloride, not gold or silver or other element except calcium and magnesium, is one of the most important elements required by our body for its physiological functions such as for the absorbance and transport of nutrients, maintenance of  blood pressure, the right balance of fluid and electrolytes, transmission of nerve signals such as in the heart, and the contraction and relaxation of the muscles, and is given almost free for us from the oceans.

It is the salt of life from the ocean where all life first originated, and for this:

We thank God for this gift.

(1,830 words in 7 pages)