Cadmium production

Cadmium production is dependent on the processing of zinc ores, which often contain 0.2 to 0.4% cadmium. As can be seen from Table 2, U.S. demand for cadmium normally exceeds the domestic supply and the United States is dependent on imports. 

In 1988, cadmium metal production in the United States increased significantly and imports decreased, but exports increased. Dramatic increases in cadmium prices in 1988 were attributed to the tight supply of cadmium worldwide, heavy speculative trading, and the large quantities of cadmium being purchased by the nickel—cadmium battery industry, particularly in Japan. About 30 countries are cadmium producers, led by Russia, Japan, the United States, Canada, Belgium, Germany, and Mexico, which cumulatively represented 64% of the 1988 reported world cadmium production of 19,773 metric tons. 

S. Eugelberg, Principles of Cadmium Production and Their Application at Outokumpu, International Symposium on Hydrometallurgy, AIME, Chicago, 1973, p. 1144. 

Cadmium. In 1989, U.S. consumption of cadmium for coatings was 1474 t (7), compared to 1552 t in 1970, 2089 t in 1979, and 1230 t in 1985. Cadmium plating amounts to about 15% of total cadmium production (see Cadmiumand cadmium alloys). Of the cadmium being plated in 1989, 30% was for automotive parts, over 22% for electronics, and 18% for industrial fasteners. Because of cadmium s high and weU-pubHcized toxicity and very tight waste restrictions, there are considerable efforts to develop alternative materials, and the quantities of cadmium used in electroplating ate expected to decrease. The price of cadmium anodes in early 1993 was about l/kg. 

Cadmium production is related to its use in electrochemical plants for metal galvanization (about 50%), for nickel-cadmium batteries and special alloys. 

The ionization is the rds. The spontaneous rate is considered to be accelerated by both inter-molecular (from the buffer) and intramolecular (from His-64) proton transfer. Cadmium can replace the native zinc from metalloenzymes and Cd nmr is being used increasingly to probe metal ligation sites in metalloproteins. The cadmium product often does not show enzyme activity however. 

Thun MJ, Schnorr TM, Smith A, et al Mortality among a cohort of US cadmium production workers—an update. J Natl Cancer Inst 74-.32S-, 1985... 

Humphreys, Paul G. May 1989. "New Line Plates Non-Cyanide Cadmium." Products Finishing, Gardner Publications, Inc., Cincinnati, Ohio. 

M.J. Thun, T.M. Schnorr, A.B. Smith, W.E. Halperin, and R.A. Lemen, Mortality among cohort of U.S. cadmium production workers — an update. J. Natl. Cancer Inst. 74 325-333, 1985. 

Cadmium production is often connected with zinc production. The impure cadmium metal produced in the purification of zinc electrowinning electrolyte is dissolved in 150 g L-1 sulfuric acid solution and electrowon in a process similar to that for zinc. The impure metals that would disturb electrowinning, for example, Cu, Ni, As, are removed by cementation with impure cadmium. The solution is neutralized with lime. The electrolyte contains 140-180 gL-1 Cd, 30-40gL x Zn, some chlorides, and animal glue as additives. The electrolysis is done using... 

After the plastic has been removed, the batteries are charged into a cadmium furnace and the cadmium is distilled off at high temperatures and collected. Negative cadmium plates from industrial batteries are also charged into the cadmium furnace for distillation of the cadmium. Carbon is added as a reductant. The charge is heated and the cadmium distilled, then collected in a water bath. The final cadmium product is in shot form. The cadmium shot is drummed, weighed, assayed, and shipped to the customer. The residue from the cadmium furnace, mostly iron and nickel, is shredded and fed to the nickel plant for nickel and iron recovery. 

In Japan, in the late 80 s, TOHO ZINC set up a plant for the pre-treatment of batteries and nickel-cadmium waste this was designed to produce an impure cadmium oxide to be used in its primary cadmium production process. 

Secondary cadmium production is in the range of 1500-2000 tons per year, approximately 10-15% of total current production in western world (OECD, 1994). 

Figure 3 - Refined Cadmium Production Figure 4 - Refined Thallium Production...

Thallium is obtained commercially from flue dust residues of zinc and lead smelters, and occasionally as a byproduct in cadmium production. Approximately 12 tons are produced worldwide each year for commercial use [9]. Approximately 1600 tons of thallium is released annually from emission sources such as refineries, coal-burning power plants, metal smelters, and cement plants [3]. Thallium is also released into the environment in runoff from copper and zinc mines. 

The most significant of the heat stabilizers are lead compounds, which accounted for nearly 68% of volume in 1989, but by 1994 had declined to 64%. Barium/cadmium compounds are the next most important, followed by organotin compounds (which actually come second in value terms). Barium/ zinc and calcium/zinc compounds have a high growth rate due to substitution in some cases of barium/zinc for barium/cadmium because of fears for the effects of cadmium on the environment and health, after it had been found that soluble cadmium products could have an adverse effect on the environment when used at above certain critical levels. 

As a result of great environmental problems with cadmium, both production and consumption declined from 2000 to 2001. In the United States the production of metal declined by 64%, while production of cadmium sulfide and other compounds declined by more than 93%. Such large reduction in production was not registered worldwide, but the decrease in cadmium production is evident This is expressed in Table 34.1. 

Worldwide cadmium production at present is around 17 000 metric tons/year and the global emission of cadmium compounds into the atmosphere is estimated to be 7000 metric tons/year, mainly from anthropogenic sources (Stoeppler 1991). 

Lemen RA, Lee JS, Wagoner JK, Blejer HP (1976) Cancer mortality among cadmium production workers. Ann NY Acad Sci 271 273-279... 

The nickel-metal hydride couple lends itself to a wound eonstruetion similar to that used by present-day wound niekel-eadmium cells. The basie components consist of the positive and negative eleetrodes insulated by plastic separators similar to those used in nickel-cadmium products. The sandwiched electrodes are wound together and inserted into a metallic can which is sealed after injection of a small amount of potassium hydroxide electrolyte solution. Tne result is a cell which bears a striking resemblance to current sealed nickel-cadmium cells. The nickel-metal hydride chemistry is also applicable to prismatic cell designs which evoke greater interest as product profiles become thinner. 

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