Minerals, recovery from seawater

Oceanic zooplankton species, wax esters in, 26 204-205 Ocean ranching, 3 198 Ocean raw materials, 17 684-699 consolidated deposits of, 17 691-694 economic aspects of, 17 697 fluid deposits of, 17 694-695 minerals recovery from, 17 695—697 unconsolidated deposits of, 17 686-691 Ocean resources, global, 17 684—686 Oceans, selenium content of, 22 11. See also Marine entries Seawater Ocean thermal energy conversion (OTEC) power plants, 13 267, 268 26 92-93 Ocean transportation, 25 328 Ochratoxin A, 7 267-268 Ochre (mineral hematite) color, 7 333... 

RECOVERY OF VALUABLE MINERAL COMPONENTS FROM SEAWATER BY ION-EXCHANGE AND SORPTION METHODS... 

Recovery of Valuable Mineral Components from Seawater by Ion-Exchange and Sorption Methods... 

Figure 2 Scheme for recovery of mineral components from seawater. Amounts of components are given in tons per year, assuming the unit capacity is around 1000 m /hr. Products which can be partially used as reagents in the technological process. 

Studies related to the recovery of mineral components from seawater have been conducted in several countries, including island countries, such as... 

Dissolved Minerals. The most significant source of minerals for sustainable recovery may be ocean waters which contain nearly all the known elements in some degree of solution. Production of dissolved minerals from seawater is limited to fresh water, magnesium, magnesium compounds (qv), salt, bromine, and heavy water, ie, deuterium oxide. Considerable development of techniques for recovery of copper, gold, and uranium by solution or bacterial methods has been carried out in several countries for appHcation onshore. These methods are expected to be fully transferable to the marine environment (5). The potential for extraction of dissolved materials from naturally enriched sources, such as hydrothermal vents, may be high. 

The world s oceans hold 1.37x10 of water (97.2% of the total amount of water of the hydrosphere). They cover 71% of the earth s surface, are actually the biggest reservoir on our planet, and contain many important minerals. The overall content of mineral matter in the oceans is estimated to be about 5 x 10 tons [1,2]. The seas contain virtually all of the naturally occurring elements and are the only universal source of mineral wealth that is available to most nations. For some of them it is the only source. Yet, most of the elements, the microelements, are available in very low concentrations, i.e., in parts per billion (ppb). The products being extracted from seawater with economic profit at present are sodium chloride, magnesium compounds, and bromine [2-4]. During the last two decades there has been growing interest in the possibility of commercial recovery of additional minerals from seawater [5] and brines [6]. 

Whereas the recovery process for minerals, and especially metals, from land-based sources must be totally adapted to the unique ore composition, the recovery of minerals (including metals) from seawater can become universal thanks to the unique ionic composition of sea water all over the world. This makes the development of a unified technology an attractive prospect for mining the seas. 

Current economic and ecological analyses of the various processes available for recovery of minerals from seawater (evaporation, solvent extraction, sorption, ion exchange, flotation, fractional precipitation, distillation, electrolysis, electrodialysis, and electrocoagulation) favor ion exchange and sorption technology. 

RECOVERY OF MINERALS FROM SEAWATER Table 5 Uranium Selective Ion-Exchange Materials... 

This element is widely employed in the production of glass and glass fibers, fluxes, antiseptics, and other products. Boron compounds are also widely used in nuclear technology [264]. Boron is an element that occurs at a relatively high concentration level in seawater (4.5 mg/L). Yet, economically acceptable processes for boron extraction from the sea do not exist, despite the fact that methods for its recovery from highly mineralized brines have been available since the beginning of the 1960s [253]. With the development of such methods, attempts were made to determine the lowest concentration levels of the element, at which economical processes could be developed [256, 266]. This critical concentration of boron was at that time estimated to be around 20 mg/L. Currently, the critical concentration of boron is estimated to be 15 mg/L or even somewhat less. 

In Chapter 3, Ruslan Khamizov and coworkers describe the economic recovery of minerals from seawater and brines formed in desalination plants and solar evaporation operations. The employment of ion-exchange technology for this purpose is critically reviewed. They carefully examine the economic aspects of optimal ion-exchange recovery of minerals from these sources by combining various techniques of the operation discussed in Chapter 2. The great rapid depletion of land-based mineral resources of the world make this a problem of great interest. 

The halogens are so reactive that they are found naturally only as compounds. The first mineral found to contain bromine (bro-margyrite, AgBr) was discovered in Mexico in 1841, and industrial production of bromides followed the discovery of the giant Stassfurt potash deposits in Germany in 1858. All methods of bromine production depend on the oxidation of bromide ions. There are no naturally occurring oxygen salts of bromine that would act as a source of the element. Commercial recovery of bromine from brines and from seawater involves the oxidation of the bromide ions in solution with CI2 to free elemental bro-... 

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