Brine leach

The chlorination process, introduced in Europe in 1843, roasted ore with chlorides, followed by a hot brine leach and subsequent precipitation of the silver on copper. In 1887 it was discovered that gold and silver can be recovered by sodium cyanide, and this process displaced the dangerous chlorination process. By 1907 the cyanide process, where a cyanide solution is mixed with 2inc dust to precipitate the silver, was universally in use. 

Stauter, J C, Tolley, W R and Um, R T, 1978. The recovery of lead from sulphide concentrates using a chloiination/brine leach/electrolysis process, in Proceedings ACS Meeting, Anaheim, March. 

Uranium ores are leached with dilute sulfuric acid or an alkaline carbonate [3812-32-6] solution. Hexavalent uranium forms anionic complexes, such as uranyl sulfate [56959-61-6], U02(S0 3, which are more selectively adsorbed by strong base anion exchangers than are other anions in the leach Hquors. Sulfate complexes are eluted with an acidified NaCl or ammonium nitrate [6484-52-2], NH NO, solution. Carbonate complexes are eluted with a neutral brine solution. Uranium is precipitated from the eluent and shipped to other locations for enrichment. Columnar recovery systems were popular in South Africa and Canada. Continuous resin-in-pulp (RIP) systems gained popularity in the United States since they eliminated a difficult and cosdy ore particle/leach hquor separation step. 

Table 1 gives the average metal content of the earth s cmst, ore deposits, and concentrates. With the exceptions of the recovery of magnesium from seawater and alkaU metals from brines, and the solution mining and dump or heap leaching of some copper, gold, and uranium (see Uranium and uranium compounds), most ores are processed through mills. Concentrates are the raw materials for the extraction of primary metals. 

A large reserve of caUche ore bearing iodine is being processed in the Atacama Desert. Production of iodine there is relatively inexpensive. About 40% of the world supply of iodine is made from these Chilean deposits. The process consists of leaching the caUche with water. Brine is stripped of iodine using an organic solvent. The iodine is then removed from the solvent to form a slurry. SoHd-phase iodine is separated from the slurry in conventional flotation cells, dried, and packaged. Details of the process are proprietary. 

Geomembrane These liners chiefly provide impermeable barriers. They can be characterized as (1) solid waste containment hazardous landfill, landfill capping, and sanitary landfill (2) liquid containment canal, chemical/brine pond, earthen dam, fish farm, river/coastal bank, waste-water, and recreation (3) mining, leach pad and tailing ponds and (4) specialties floating reservoir caps, secondary containment, tunnel, erosion, vapor barrier, and water purification. Plastics used include medium to very low density PE, PVC, and chlorosulfonated PE (CSPE). (The Romans used in their land and road constructions what we call geomembrane.)... 

Production as practiced in Chile consists of leaching residues from their Na nitrate operation to produce a weak brine of K nitrate which is coned by solar evapn When the proper concn of K nitrate is achieved it is recovered by crystn (Ref 14)... 

To conclude this section, reference may be drawn to what is called the Placid process for recycling lead from batteries. Placid denotes the leaching of lead in warm, slightly acidic, hydrochloric acid brine to form soluble lead chloride. Lead is won from the lead chloride on the cathode of an electro winning cell and is collected. Chloride anions are released simultaneously, but then react immediately with hydrogen ions that have been produced stoichio-metrically from electrolysis of water in the anolyte and passed into the catholyte through a membrane. The hydrochloric acid that is formed is returned as a make-up content to the leaching bath. 

Leach, D. L., G. S. Plumlee, A. H. Hofstra, G. P. Landis, E. L. Rowan and J. G. Viets, 1991, Origin of late dolomite cement by C02-saturated deep basin brines evidence from the Ozark region, central United States. Geology 19, 348-351. 

It occurs in seawater where some species of seaweed and kelp accumulate the element in their cells. It is also recovered from deep brine wells found in Chile, Indonesia, Japan, and Michigan, Arkansas, and Oklahoma in the United States. The iodine is recovered from cremated ashes of seaweed. The ashes are leached with water to remove the unwanted salts. Finally, manganese dioxide (MnO ) is added to oxidize the iodine ions (1 ) to produce elemental diatomic iodine (y. The following reaction takes place 41 " + MnO —> Mnl + I. + 202-... 

B) The brines are produced by leaching of saline fluid inclusions in crystalline rocks or by intense water/rock interactions (Frape and Fritz 1987)... 

Salt caverns are developed by solution mining, a process (leaching) in which water is injected to dissolve the salt. Approximately 7 to 10 units of fresh water are required to leach 1 unit of cavern volume. Figure 10-190 illustrates the leaching process for two caverns. Modern salt dome caverns are shaped as relatively tall, slender cylinders. The leaching process produces nearly saturated brine from the cavern. Brine may be disposed into nearby disposal wells or offshore disposal fields, or it may be supplied to nearby plants as a feedstock for manufacturing of caustic (NaOH) and chlorine (CI2). The final portion of the produced brine is retained and stored in artificial surface ponds or tanks to be used to displace the stored liquid from the cavern. 

The TDS of lake waters can be high because of evaporation, as in the Great Salt Lake of Utah or the Dead Sea (Israel/Jordan). Well waters often contain high concentrations of electrolytes leached from the rocks—notably iron salts, which are a major nuisance—and the highly saline waters associated with oil- or gas-bearing formations are frequently better described as brines. 

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