Figure 58 
ABUNDANCE OF SOME CRITICAL 
ELEMENTS IN SEA WATER 
Average 
Concentration 
Mg/Liter' 
Element 
Presently produced: 
Magnesium . 
Bromine 
Not Produced: 
Uranium 0.003 
Silver 0.00004 
Tin. 0.0008 
Gold , 0.000004 
Zinc . 0.01 
Titanium 0.001 
Note that 1 part per million equals 1.026 Mg/Liter. 
Source: Goldberg, E. D., ‘‘Minor Elements in Sea Water,” 
Chemical Oceanography, vol. \, J. P. Riley and G. Skirrow 
(ed.), Academic Press, London, pp. 164-165. 
Most dissolved elements found in the ocean are 
being recovered more economically from other 
sources. Possibly the next material to be extracted 
commercially from sea water will be uranium. The 
English are reported to be experimenting with a 
uranium process, but prospects for its commercial 
utilization are not known.?? 
The economics of bromine versus magnesium 
extraction is a good illustration of why one should 
not be too pessimistic about the commercial 
possibilities of extracting less concentrated ele- 
ments. Sea water contains only 65 ppm (parts per 
million) bromine versus 1,300 ppm magnesium. 
Yet bromine sells for about 25 cents per pound 
versus 35 cents for magnesium. The bromine 
extraction process is less costly than the magne- 
sium process because it requires only 2 process 
steps to extract and convert the bromine to a 
salable form, whereas 10 steps are required for 
magnesium metal. 
This indicates that other elements, even though 
less concentrated than bromine, may be produced 
at lower costs per pound than bromine if the 
technology can be developed along with the 
required market. 
2° Spangler, M. B., op. cit., p. 9. 
VI-196 
2. Long-Range Technology 
To obtain minute quantities of elements it is 
necessary to modify the present philosophy of 
processing 100 per cent of sea water, 96.5 per cent 
of which is water, to recover only very small 
amounts of chemicals. It may be preferable to 
remove desired solids from the sea water at sea and 
then handle only the useable material. 
Present desalting methods concentrate brines 
by a ratio of about two to one. However, 
concentrations of up to three to one have been 
reported feasible, and pretreatment processes such 
as ion exchange may allow concentration ratios as 
high as five to one. Future techniques may further 
increase the ability to concentrate brines. Im- 
proved extraction processes using concentrated 
brines (as may be available from desalting facili- 
ties) will permit more economical recovery of 
various chemicals. 
Extraction directly from the sea using natural 
processes, another potential method of recovery, 
will require considerable additional basic research 
into sea water chemistry, biology, and extraction 
processes. For example, iodine has been extracted 
commercially from certain seaweed that concen- 
trates the element. Some marine organisms con- 
centrate trace elements in ratios as great as 
100,000 to 1, as with vanadium. Lead is concen- 
trated as much as 20 million to 1 in certain fish 
bones. 
Biological concentration suggests future tech- 
niques of recovering valuable trace elements by 
learning which organisms can concentrate the 
desired elements best, culturing them in sea water, 
harvesting them, and extracting the elements, or 
learning the processes and adapting them to 
industrial practice. 
D. Conclusions 
Extraction of magnesium compounds, magne- 
sium metal, bromine, and salt from sea water is 
highly successful. World-wide, salt is the most 
important product. Almost 30 per cent of the 
total world production of salt is from sea water. 
U.S. industry has been profitably extracting 
magnesium and bromine from sea water for over 25 
years. About 90 per cent of all magnesium metal 
and 50 per cent of all bromine production in the 
United States is derived from sea water. 
