Mercury amalgamation process

Water is reduced to hydrogen at the cathode (however, in the mercury (amalgam) process, another cathode reaction is used, see section Amalgam (Mercury) Process) ... 

Silver is usually extracted from high-grade ores by three common processes that have been known for many years. These are amalgamation, leaching, and cyanidation. In one amalgamation process, ore is crushed and mixed with sodium chloride, copper sulfate, sulfuric acid, and mercury, and roasted in cast iron pots. The amalgam is separated and washed. Silver is separated from its amalgam by distillation of mercury. 

Nuclear Fuel Services, Inc. (NFS), developed the commercially available DeHg process for the low-temperature treatment of mercury-contaminated hazardous and mixed wastes. The technology uses a proprietary amalgamation process to convert mercury into a nonhazardous solid. The technology is now offered by Advanced Recovery Systems, Inc. The developer claims the technology can be used on sludges, hazardous and mixed wastes, and mercury-contaminated wastes containing tritium. 

When he demonstrated de Medinas cold amalgamation process to the Viceroy, the latter offered him suitable reward, ordered him to make the secret known at Potosi (Bolivia), and added that the most important wedding in the world was about to take place the marriage of Mount Potosi (silver) to Mount Huancavelica (mercury) (60). 

Steel wool was used as the cathode in the process developed by G.E. Edwards. In Edwards process the mercury has to be recovered from the steel wool. Steel and galvanized steel were also used as cathodes in this investigation and mercury amalgamation was confirmed. 

Unlike covellite, the silver sulfide reaction with Hg(0) vapor is not exclusively a redox process. XRD analysis showed that no silver sulfide remained in samples having consumed 42 wt% Hg(0) and that cinnabar formation was minimal. The products formed are mercurial amalgam, HgAg, and Ag,HgS as reflected in Reaction (2). Reaction (2) does not account for two third of the initial sulfur present, however, no residual crystalline sulfur was observed in the diffraction data. None the less, this reaction reflects partial reduction of the silver(I) and oxidation of Hg(0). 

In the mercury cell process chlorine is liberated from a brine solution at Ihe anodes which are. today, typically melal anodes (Dimensionally Stable Anodes or DSAl. Collection and processing of the chlorine is similar lo Ihe techniques employed when diaphragm cells are used. However. Ihe cathode is a flowing bed or mercury. When sodium is released by electrolysis it is immediately amalgamated with the mercury The inereury amalgam is then decomposed in a separate cell 10 form sodium hydroxide and Ihe mercury is returned for reuse. 

The demercuration of (3-alkoxymercurials is usually best effected using alkaline sodium borohydride. Few rearrangements during this free radical reduction process have been observed 429 When the mercury moiety is positioned a to a carbonyl group, alkaline H2S430,431 or 1,3-propanedithiol316 provide alternatives that afford complementary stereochemical results (equation 262). The use of sodium-mercury amalgam is also useful for stereospecific reduction.432 433... 

Various modifications of the amalgamation process have been employed in Mexico and Chile, but in recent years this method has been to a great extent supplanted by the cyanide process, described on p. 291. Extraction by amalgamation is more difficult with silver than with gold. Mercury liberates silver rapidly from the chloride, bromide, and iodide, and very slowly from the sulphide. Other ores have to be converted... 

The pan-amalgamation process has found more favour than the patio process. The ore in the form of fine sludge is stirred in iron pans with a mixture of mercury, common salt, and cupric sulphate. When the action is complete, the excess of mercury is drained off, and the amalgam is allowed to settle, and then decomposed by heat. In the Boss system the process is continuous, a series of pans and settlers being employed. Some silver ores, notably those containing sulphides of arsenic, antimony, copper, iron, and zinc, are roasted with common salt before amalgamation. 

The amalgamation process is used for native silver. The ore is treated with mercury, which dissolves the silver. The liquid amalgam is then separated from the gangue and distilled, the mercury collecting in the receiver and the silver remaining in the retort. 

Mercury amalgams have also been around for a long time. An amalgam is a combination of mercury with at least one other metal. Amalgams are formed when a metal, such as silver, dissolves in mercury. The process... 

Caustic Alkali Sodium hydroxide solution from the decomposer of the amalgam process usually has a concentration of 50% and a chloride content of only 5-50 mg kg-1. It is cooled down from 80-120 °C to 40-60 °C in steel pipes, Ni-, or Incolloy coolers. Any particles of graphite from the decomposer material or traces of mercury are removed by centrifuges, candle filters, or precoated leaf filters. 

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