Mercury-cadmium battery

Other cells, based on zinc anodes or on mercuric oxide cathodes are known. Among them are the silver-zinc battery, zinc-copper oxide battery, mercury-cadmium battery etc. 

Batteries. Many batteries intended for household use contain mercury or mercury compounds. In the form of red mercuric oxide [21908-53-2] mercury is the cathode material in the mercury—cadmium, mercury—indium—bismuth, and mercury—zinc batteries. In all other mercury batteries, the mercury is amalgamated with the zinc [7440-66-6] anode to deter corrosion and inhibit hydrogen build-up that can cause cell mpture and fire. Discarded batteries represent a primary source of mercury for release into the environment. This industry has been under intense pressure to reduce the amounts of mercury in batteries. Although battery sales have increased greatly, the battery industry has aimounced that reduction in mercury content of batteries has been made and further reductions are expected (3). In fact, by 1992, the battery industry had lowered the mercury content of batteries to 0.025 wt % (3). Use of mercury in film pack batteries for instant cameras was reportedly discontinued in 1988 (3). 

Subcategory A encompasses the manufacture of all batteries in which cadmium is the reactive anode material. Cadmium anode batteries currently manufactured are based on nickel-cadmium, silver-cadmium, and mercury-cadmium couples (Table 32.1). The manufacture of cadmium anode batteries uses various raw materials, which comprises cadmium or cadmium salts (mainly nitrates and oxides) to produce cell cathodes nickel powder and either nickel or nickel-plated steel screen to make the electrode support structures nylon and polypropylene, for use in manufacturing the cell separators and either sodium or potassium hydroxide, for use as process chemicals and as the cell electrolyte. Cobalt salts may be added to some electrodes. Batteries of this subcategory are predominantly rechargeable and find application in calculators, cell phones, laptops, and other portable electronic devices, in addition to a variety of industrial applications.1-4 A typical example is the nickel-cadmium battery described below. 

Cadmium (Cd) anode cells are at present manufactured based on nickel-cadmium, silver-cadmium, and mercury-cadmium couples. Thus wastewater streams from cadmium-based battery industries carry toxic metals cadmium, nickel, silver, and mercury, of which Cd is regarded the most hazardous. It is estimated that globally, manufacturing activities add about 3-10 times more Cd to the atmosphere than from natural resources such as forest fire and volcanic emissions. As a matter of fact, some studies have shown that NiCd batteries contribute almost 80% of cadmium to the environment,4,23 while the atmosphere is contaminated when cadmium is smelted and released as vapor into the atmosphere4 Consequently, terrestrial, aquatic, and atmospheric environments become contaminated with cadmium and remain reservoirs for human cadmium poisoning. 

Nickel-cadmium, silver-cadmium, and mercury-cadmium batteries Plating... 

Although several studies carried out in Europe, Japan and the USA concluded that mercury from batteries in waste does not pose a threat to the environment irrespective of the means of disposal, legislation was introduced to control the dispersal of mercury, cadmium and lead from waste batteries into the environment by separately collecting waste mercuric oxide, nickel cadmium and lead-acid batteries. 

The focus of European legislation for battery waste has been to reduce the impact on the environment of batteries containing heavy metals. Council Directive 91/157/EEC on batteries and accumulators containing certain dangerous substances was introduced with the aim of restricting the use of batteries containing cadmium, mercury and lead and controlling their disposal. 

The serious nature of the health problems caused by the ingestion of mercury, cadmium, and lead is beyond question. However, sources other than batteries also contribute to the magnitude or the potential and actual health problems caused by these materials. Barnett and Wolsky (6) have collected information on the fractions of the total amounts of lead, cadmium, and mercury produced in the United States that enter into battery manufacturing. Their estimates for 1989 are as follows ... 

Specific legislation relating to batteries includes the Toxic and Dangerous Waste Directive which gives priority consideration to mercury, cadmium and lead. This directive is being replaced by a Directive on Hazardous Waste which specifically includes batteries and other electrical cells. Additional metals to be covered include nickel, cobalt, silver, zinc and lithium. Thus, all commonly used batteries will be covered by this directive. 

Individual countries within the European Community handle the battery waste problem differently. For example, in Switzerland all used consumer batteries are considered hazardous waste and must be collected separately from ordinary household waste. Batteries must be recycled or stored in warehouses, not landfilled. A tax is collected on all new battery purchases to help defray the cost of recycling. In Italy, spent dry batteries are considered as hazardous waste and must be collected separately. In Sweden (10), the environmental issues relatii to waste batteries are addressed in the Control of Chemicals Bill and in the Decree on Environmentally Hazardous Batteries. All used batteries containing cadmium or mercury are collected separately under government control. The cadmium is then recycled. Regulations are in place for the manufacture of nickel/cadmium cells, limiting the exposure of workers and the emission of toxic materials. 

The batteries of principal concern at this time are lead-acid batteries, nickel-cadmium batteries, and mercury batteries. Even though they may contribute smaller amounts of toxic pollutants to MSW than other sources, concerted efforts are and should be made to prevent pollutants from these batteries from entering the foodchain and from becoming a health hazard. 

Most of the commercial battery systems, e.g. zinc-carbon, manganese dioxide-zinc, nickel-cadmium, lead-acid and mercury button cells contain toxic substances. Strong efforts have been made to recycle these batteries, to lower the concentration of their toxic substances or to replace them with alternative systems. Nevertheless, battery production processes as well as disposal or recycling activities of spent batteries are responsible for the infiltration of a few toxic substances in our environment. The following chapters describe the toxicology of mercury, cadmium and lead, which are the most toxic components found in different battery systems. 

For this reason, heavy metals and metal ions that are used as additives in plastics and rubber (as colorants, stabilisers, plasticisers and so on) should be monitored carefully, and their use as well as the amounts used should be well known and regulated. In addition to their existence in some of the additives used in plastics and rubbers, toxic heavy metals most of which are considered chronic poisons, such as arsenic, lead, mercury, cadmium, nickel, zinc and chromium, are frequently encountered in industrial processing and other manufacturing operations (their main industrial sources include paint, ink, plastic, rubber and plastic film production, leather tanning, wood preserving, battery manufacturing, and so on). 

Depending on the electrochemical system, some portable batteries contain hazardous substances such as mercury, cadmium, and lead. Table 19.4 shows an overview of the main substances contained in portable batteries in percentages by weight. (The material composition varies significantly depending on the battery size, type, and composition. All figures are mean averages.)... 

Without going into detail regarding the toxicity and ecotoxicity of the heavy metals contained in batteries, it is clear that large quantities of mercury, cadmium, or lead must not be disposed of in domestic waste disposal facilities (normal tips) as contamination of the surrounding areas cannot definitively be prevented. 

The RoHS Directive states Member States shall ensure that, from 1 July 2006, new electrical and electronic equipment (EEE—basically anything with a plug or battery) put on the market does not contain lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls (PBB), or polybrominated diphenyl ethers (PBDE). RoHS establishes maximum concentration values, which are up to 0.1% by weight in homogeneous materials for lead, mercury, hexavalent chromium, PBB, and PBDE, and up to 0.01% by weight in homogenous materials for cadmium. ... 

Another parameter which will have a very definite bearing on the choice of battery type is cell voltage, particularly on-load voltage, which are tabulated in Table 2.1 for various types of primary battery. It can be seen that these range from 0.75V/ceJI (mercury-cadmium) to over 3 V with some of the lithium and magnesium based organic electrolyte systems. 

Mercury-zinc primary batteries 8/3 8.2 Mercury-indium-bismuth and mercury-cadmium primpiy batteries 8/3... 

Mercury-indium-bismuth and mercury-cadmium primary batteries... 

Mercury-indium-bismuth and mercury-cadmium batteries are available from some manufacturers (e.g. Crompton-Parkinson). These are alkaline systems recommended for applications where high reliability in particularly onerous long-term storage and use conditions is a prime requirement. 

Mallory also supply a mercury-cadmium battery in their Duracell range. This battery (No. 304116) is of 12.6 V with a capacity of 630 mA h to an end-point of 10.3 V, or 900MA h to an end-point of 7.0 V, both on 13 000 Q at 20°C. This cylindrical battery weighs 127 g and occupies a volume of 40.5 cm and is recommended for use in applications such as alarm systems using voltage-sensitive low-battery indicators. Typical two-step discharge characteristics for this battery are shown in Figure 8.3. 

Mercuric oxide-itidium-bismuth and mercury-cadmium (primary) batteries supplied by Crompton-Parkinson... 

Mallory supply a mercury-cadmium battery in their Duracell range. This batteiy (No. 304116) is of 12.6 V... 

Duracell UK Technical Division Duracell House Gatwick Road, Crawley RHIO 2PA Primary batteries, mercury-zinc, silver-zinc, lithium solid electrolyte types, nickel-cadmium, lithium-sulphur dioxide, lithium-manganese dioxide, zinc-air. See also Duracell (US)... 

Primary batteries, zinc-alkaline manganese dioxide, mercury-zinc, carbon-zinc Leclanche, magnesium types, lithium types, silver oxide-zinc secondary batteries, alkaline, nickel-iron, mercury-cadmium. 

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