Recovery electrolyte

Manufacture and Recovery. Electrolytic copper refinery slimes are the principal source of selenium and its sister element, tellurium, atomic numbers 34 and 52, respectively. Electrolytic copper refinery slimes are those constituents in the copper anode which are not solubilized during the refining process and ultimately accumulate in the bottom of the electrorefining tank. These slimes are periodically recovered and processed for their metal values. Slimes generated by the refining of primary copper, copper produced from ores and concentrates, generally contain from 5—25% selenium and 2—10% tellurium. 

Incineratlon/Thermal Treatment R21 Metals Recovery - Electrolytic R22 Metals Recovery - Ion Exchange... 

C99 Other Chemical Treatment R21 Metals Recovery Electrolytic... 

Compounds CEMode Matrix (Recovery) Electrolyte (LOD) References... 

The solutions we offer are based on two main technologies electrolytic silver recovery from fixer solutions and cascade fixing. In what follows we will give more teclmical details about these teclmologies. We will clarify the key-factors to obtain reliable and more ecological solutions for the silver in the rinsing water. 

Electrolytic silver recovery is a common technique to desilver fixing solutions. It has been known for decades, although it never really reached a point where it was massively introduced into the industrial radiology market. In the past, the main reasons to implement silver recovery were twofold. 

The desilvering speed of an electrolytic silver recovery unit can be characterized by two parameters. 

The copolymer latex can be used "as is" for blending with other latexes, such as in the preparation of ABS, or the copolymer can be recovered by coagulation. The addition of electrolyte or free2ing will break the latex and allow the polymer to be recovered, washed, and dried. Process refinements have been made to avoid the difficulties of fine particles during recovery (65—67). 

Chlorine Plant Auxiliaries. Flow diagrams for the three electrolytic chlor—alkali processes are given in Figures 28 and 29. Although they differ somewhat in operation, auxiUary processes such as brine purification and chlorine recovery are common to each. 

The lime—soda process is practiced mainly in isolated areas in some process operations, in the Kraft recovery process, and in the production of alurnina. It is not as efficient a route as electrolytic production. 

M. V. Ginatta, "G.S. Electrolytic Process for the Recovery of Lead from Spent Electric Storage Batteries," paper presented at the Mnnual MIME Meeting 1975, New York. 

Electrowinning from Aqueous Solutions. Electrowinriing is the recovery of a metal by electrochemical reduction of one of its compounds dissolved in a suitable electrolyte. Various types of solutions can be used, but sulfuric acid and sulfate solutions are preferred because these are less corrosive than others and the reagents are fairly cheap. From an electrochemical viewpoint, the high mobiUty of the hydrogen ion leads to high conductivity and low ohmic losses, and the sulfate ion is electrochemicaHy inert under normal conditions. 

Zinc. The electrowinning of zinc on a commercial scale started in 1915. Most newer faciUties are electrolytic plants. The success of the process results from the abiUty to handle complex ores and to produce, after purification of the electrolyte, high purity zinc cathodes at an acceptable cost. Over the years, there have been only minor changes in the chemistry of the process to improve zinc recovery and solution purification. Improvements have been made in the areas of process instmmentation and control, automation, and prevention of water pollution. 

Metals less noble than copper, such as iron, nickel, and lead, dissolve from the anode. The lead precipitates as lead sulfate in the slimes. Other impurities such as arsenic, antimony, and bismuth remain partiy as insoluble compounds in the slimes and partiy as soluble complexes in the electrolyte. Precious metals, such as gold and silver, remain as metals in the anode slimes. The bulk of the slimes consist of particles of copper falling from the anode, and insoluble sulfides, selenides, or teUurides. These slimes are processed further for the recovery of the various constituents. Metals less noble than copper do not deposit but accumulate in solution. This requires periodic purification of the electrolyte to remove nickel sulfate, arsenic, and other impurities. 

The first commercial plant to use CYANEX 272 became operational in 1985. An additional three plants were constmcted between 1985 and 1989. Of the four, one is in South America and three in Europe. An additional three plants have been built two in Europe (1994) and one in North America (1995). Approximately 50% of the Western world s cobalt is processed using CYANEX 272. Both high purity salts and electrolytic cobalt metal are recovered from solutions ranging in composition from 30 g/L each of cobalt and nickel to 0.2 g/L Co, 95 g/L Ni Operating companies usually regard use of CYANEX 272 as confidential for competitive reasons and identities cannot be disclosed. CYANEX 272 is being evaluated on the pilot-plant scale in many additional projects involving the recovery of cobalt and other metals. 

J. E. Hoffmann, "Recovery of Selenium from Electrolytic Copper Refinery Slimes," in V. Kudryk, D. A. Corrigan, and W. W. Liang, eds.. Precious Metals Mining Extraction and Processing H, TMS, Warrendale, Pa., 1983. 

W. E. Cowley, G. Thwaite, G. Waine, The Selective Recovery Of Sodium From Mmalgam Using fd-Mlumina, Associated Octel Co. Ltd. 1978, presented at the Second International Meeting of Solid Electrolytes, University of St. Andrews, Scotiand. 

Most commercial tellurium is recovered from electrolytic copper refinery slimes (8—16). The tellurium content of slimes can range from a trace up to 10% (see Seleniumand selenium compounds). Most of the original processes developed for the recovery of metals of value from slimes resulted in tellurium being the last and least important metal produced. In recent years, many refineries have changed their slimes treatment processes for faster recovery of precious metals (17,18). The new processes have in common the need to remove the copper in slimes by autoclave leaching to low levels (<1%). In addition, this autoclave pretreatment dissolves a large amount of the tellurium, and the separation of the tellurium and copper from the solution which then follows places tellurium recovery at the beginning of the slimes treatment process. 

Electrolysis. Electrowinning of zirconium has long been considered as an alternative to the KroU process, and at one time zirconium was produced electrolyticaHy in a prototype production cell (70). Electrolysis of an aH-chloride molten-salt system is inefficient because of the stabiUty of lower chlorides in these melts. The presence of fluoride salts in the melt increases the stabiUty of in solution, decreasing the concentration of lower valence zirconium ions, and results in much higher current efficiencies. The chloride—electrolyte systems and electrolysis approaches are reviewed in References 71 and 72. The recovery of zirconium metal by electrolysis of aqueous solutions in not thermodynamically feasible, although efforts in this direction persist. 

Fig. 1. Recovery of copper from sulfide ore. The residue from electrolytic refining is processed to recover gold, silver, and selenium. Courtesy of Kennecott...

Anode impurities either dissolve in the electrolyte or fall to the bottom of the electrolytic cell as anode slime. These slimes contain silver, gold, selenium, and tellurium and represent a very significant value. Thus, the recovery of by-products from the anode slime is an important operation. 

---