Cadmium, metal manufacturing

Cadmium Fluoride. Elemental fluorine reacts with cadmium metal as well as the oxide, sulfide, and chloride to give CdF2 [7790-79-6]. Alternatively, treatment of CdCO with 40% HF yields a solution of CdF2, which may be evaporated to recover efflorescent crystals of the dihydrate. CdF2 has been used in phosphors, glass manufacture, nuclear reactor controls, and electric bmshes and in 1991 sold as a pure electronic grade (99.99%) at l/g. 

To protect humans and other mammals, proposed air-quality criteria range from 0.01 to less than 1.0 mg/m3 for metallic nickel and slightly soluble nickel compounds, 0.015-0.5 mg/m3 for water soluble nickel compounds, and 0.005 to 0.7 mg/m3 for nickel carbonyl (Table 6.10). Inhalation of nickel subsulfide concentrations (0.11 to 1.8 mg Ni/m3) near the current threshold limit value of 1 mg Ni/m3 can produce detrimental changes in the respiratory tract of rats after only a few days of exposure (Benson et al. 1995). Additional animal studies are recommended to identify minimally effective inhalation exposure levels for the various nickel compounds (USPHS 1993). Continued monitoring of nickel refining, nickel-cadmium battery manufacture, and nickel powder metallurgy installations is recommended because ambient air levels of bioavailable nickel at these... 

Zinc mining, lead and zinc refining and non-ferrous metal industry Manufacture of cadmium compounds Manufacture of pigments Manufacture of stabilisers Manufacture of batteries Electroplating... 

In connection with pyrometallurgical zinc metal manufacture, cadmium oxide and sulfide are also reduced. In the subsequent zinc refining by distillation, cadmium is effectively separated from zinc, as the two metals condense at different temperatures. 

An important property is that, because of its volatility (melting point 321 C, boiling point 765 °C), cadmium metal can be burned in air to form a brown oxide (CdO). This is not stable in moist air and will slowly convert to the carbonate. However, CdO is readily soluble in mineral adds and is used as a starting point to make solutions of cadmium salts for pigment manufacture. 

Not all manufacturers produce cadmium oxide, as some prefer to dissolve cadmium metal directly in acid. However cadmium oxide is used in many other applications, including nickel cadmium batteries and stabilizers for polymers. 

Cadmium metal powders as produced conventionally are unsuitable for use as electrode materials. Activated cadmium anodes are produced by (1) electroforming the anode, (2) electroforming powder by a special process followed by pelleting, or (3) precipitating by a special process as a low-nickel alloy and pelleting. All of these processes have been used by different manufacturers to give cells with various performance parameters. ... 

Replacement of Labile Chlorines. When PVC is manufactured, competing reactions to the normal head-to-tail free-radical polymerization can sometimes take place. These side reactions are few ia number yet their presence ia the finished resin can be devastating. These abnormal stmctures have weakened carbon—chlorine bonds and are more susceptible to certain displacement reactions than are the normal PVC carbon—chlorine bonds. Carboxylate and mercaptide salts of certain metals, particularly organotin, zinc, cadmium, and antimony, attack these labile chlorine sites and replace them with a more thermally stable C—O or C—S bound ligand. These electrophilic metal centers can readily coordinate with the electronegative polarized chlorine atoms found at sites similar to stmctures (3—6). 

Heavy Metals. Heavy metals of particular concern in the treatment of wastewaters include copper, chromium, 2inc, cadmium, mercury, lead, and nickel. They are usually present in the form of organic complexes, especially in wastewaters generated from textiles finishing and dye chemicals manufacture. 

TXRF is frequently used for contamination control and ultrasensitive chemical analysis, in particular in relation to materials used in semiconductor manufacturing [278,279], and metallic impurities on resin surfaces, as in PFA sheets [279,280], TXRF has been used by Simmross et al. [281] for the quantitative determination of cadmium in the four IRMM polyethylene reference materials (VDA-001 to 004). Microsamples (20-100 ig) from each reference material were transferred by hot pressing at 130 °C as 3 xm thin films straight on to quartz glass discs commonly used for TXRF analysis. The results obtained were quite satisfactory (Table 8.50). Other reports of the forensic application to plastic materials by TXRF have appeared [282], including a study of PE films by elemental analysis [283],... 

Batteries may be taken to a household-hazardous-waste collection or a local battery collection program. One can also contact the battery manufacturer for other disposal options or for information on collection programs. If disposal is the only option, and the household batteries are not banned from the permitted landfill in the area, one should protect the batteries for disposal by placing them in a sturdy plastic bag in a sturdy container to help guard against leakage. Waste batteries should not be burned because of the metals that could explode. When burned, some heavy metals such as mercury may vaporize and escape into the air, and cadmium and lead may end up in the ash.12... 

---