Zinc carbon system

Garrett et al. (1979) studied the concentration of soluble zinc in aqueous slurry of basic zinc carbonate system over the pH range 7 to 13 and observed that in the region of pH 8 to 11, where mud commonly is maintained, basic zinc carbonate provides a limited concentration of soluble zinc ion due to the poor solubility of the basic zinc carbonate in the region. Most of the chemical exists as small particles to provide a reserve for releasing zinc ion when H2S influx occurs. If this solid does not remain distributed in the mud system, settles out, or is discarded in some way, it will not be available when needed. 

Primary batteries have existed for over 100 years, but up to 1940, the zinc-carbon battery was the only one in wide use. During World War II and the postwar period, significant advances were made, not only with the zinc-carbon system, but with new and superior types of batteries. Capacity was improved from less than 50 Wh/kg with the early zinc-carbon batteries to more than 400 Wh/kg now obtained with lithium batteries. The shelf life of batteries at the time of World War n was limited to about 1 year when stored at moderate temperatures the shelf life of present-day conventional batteries is from 2 to 5 years. The shelf life of the newer lithium batteries is as high as 10 years, with a capability of storage at temperatures as high as 70°C. Low-temperature operation has been extended from 0 to -40C, and the power density has been improved manyfold. Special low-drain batteries using a solid electrolyte have shelf lives in excess of 20 years. 

The zinc-carbon system is used in special designs to enhance particular performance characteristics or for new or unique applications. 

Conventional Systems. Reserve batteries employing the conventional electrochemical systems, such as the Leclanch6 zinc-carbon system, date back to the 1930-1940 period. This stmcture, in which the electrolyte is kept in a separate vial and introduced into the cell at the time of use, was employed as a means of extending the shelf life of these batteries, which was very poor at that time. Later similar stmctures were developed using the zinc-alkaline systems. Because of the subsequent improvement of the shelf life of these primary batteries and the higher cost and lower capacity of the reserve stmcture, batteries of this type never became popular. 

The demand for electrically operated tools or devices that can be handled independently of stationary power sources led to a variety of different battery systems which are chosen depending on the field of application. In the case of rare usage, e.g., for household electric torches or for long-term applications with low current consumption, such as watches or heart pacemakers, primary cells (zinc-carbon, alkaline-manganese or lithium-iodide cells) are chosen. For many applications such as starter batteries in cars, only rechargeable battery systems, e.g., lead accumulators, are reasonable with regard to costs and the environment. 

Zinc/carbon and alkaline/manganese cells are primary battery systems lead, nickel/cadmium, and nickel/metal hydride accumulators are secondary batteries with aqueous electrolyte solutions. Their per-... 

Mn02 is used for the same purpose as the cathode active material in lithium-manganese dioxide (Li - Mn02) batteries it has been used for a long time in zinc-carbon and alkaline-manganese dioxide batteries, which are aqueous-electrolyte systems. 

K. Kordesch, C. Fabjan, J. Daniel-Ivad, J. Oliveira, Zinc-carbon-hybrid systems, Power Sources Conf. Brighton, April 1997. 

Zinc carbonate reacts with epoxide to form zinc alkoxide, which in turn reacts with carbon dioxide to regenerate zinc carbonate. The most effective catalyst systems were the reaction products between diethylzinc and polyhydroxy compounds such as water or pdyhydric phenols243,244. This copolymer is interesting as a biodegradable elastomer248. ... 

The identification of different carbonate binding modes in copper(II) and in zinc(II)/2,2 -bipyridine or tris(2-aminoethyl)amine/(bi)carbonate systems, specifically the characterization by X-ray diffraction techniques of both r)1 and r 2 isomers of [Cu(phen)2(HC03)]+ in their respective perchlorate salts, supports theories of the mechanism of action of carbonic anhydrase which invoke intramolecular proton transfer and thus participation by r)1 and by r 2 bicarbonate (55,318). 

The name Leclanche cell is given to the familiar primary system consisting of a zinc anode, manganese dioxide cathode and an electrolyte of ammonium chloride and zinc chloride dissolved in water. The alternative designation zinc-carbon ceir is broader and includes the so-called zinc chloride system which, due to a different electrolyte composition, is characterized by a different discharge mechanism. The Leclanche cell may be written as... 

The system is designated by a letter, e.g. B specifies Li/(CFJt) , C specifies Li/MnOz, L the Zn/Mn02 alkali cell, etc. (A blank rather than a letter is used for Leclanchd or zinc-carbon cells.) The shape is also specified by a letter R for cylindrical, S for prismatic and F for flat. The following examples illustrate how the system works. 

At the present time, a large number of spent batteries are disposed of directly into the urban waste stream without proper controls. In addition to the most common systems such as zinc-carbon, alkaline manganese and nickel-cadmium, these now include, at an increasing rate, nickel-metal hydride and lithium cells. Such disposal is of serious concern because of the possible effects of battery components on the environment. Consequently, most countries are now evolving policies for collection and recycling. The majority of lead-acid batteries are recycled, but the number of recycling plants in operation worldwide for other battery systems is still very small due to the unfavourable economic balance of such operations (see Table A3.1). Some of the procedures for the disposal and recycling of battery materials are now briefly described. 

Carbon-zinc is the generic term for the Leclanche and zinc chloride system. Carbon-zinc cells provide an economical source of electrical energy for low drain applications. The service life depends strongly on the discharge rate, the operating schedule and the cutoff voltage, as well as temperature and storage conditions. 

The term primary battery is used to describe any single use battery system. These include, amongst others, alkaline-manganese, zinc-carbon, lithium, mercuric oxide and zinc-air chemistries. Primary batteries are lightweight and convenient, relatively inexpensive and eonsequently are used by households throughout the world to power portable electrical and electronic devices, radios, torches, toys and a whole host of other every day appliances. 

The most common primary batteries in use today are the zinc-carbon and the alkaline-manganese battery systems. Together, they constitute in excess of 90% by weight of the total consumer battery market in Europe. Consequently, particularly within the realm of battery recycling, the term primary battery is often used to describe just these two systems. 

Lead is sometimes still used in both battery systems. In zinc-carbon batteries it is employed chiefly as an alloying addition to improve the forming characteristics of the zinc can, and additionally acts as a corrosion inhibitor. In alkaline-manganese it has found use as a plating alloy on the brass nail to reduce gassing. In zinc-carbon cells, the lead content is in the order of 0.02% and in those alkaline-manganese batteries where lead is still used, the addition is at a level of a few parts per million. 

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. 

Zinc is one of the most mobile of the heavy metals. The zinc compounds formed with the common anions found in surface waters are soluble in neutral and acidic conditions. In reducing environments, zinc sulfide (ZnS) is a relatively insoluble and stable compound, which may oxidize in the presence of dissolved oxygen. Zinc carbonate (ZnCOj) is assumed to be less stable than zinc sulfide, though still relatively insoluble. Zinc ions are dominant up to pH values of about 9 in simple aqueous systems. In basic solutions, zinc hydroxide (Zn(OH)2) precipitates if the concentration of zinc is 10.4 M. Zinc hydroxide shows minimal solubility at pH 9.5 and dissolves at higher pH values as the zincate anion, Zn(OH) . 

Only one study was found on microemulsion-based preparation of zinc oxide [103]. The two-microemulsion synthesis protocol was used by Hingorani et al. [103] to prepare zinc carbonate that was then calcined ( 220 C) to produce zinc oxide. Working with the CTAB/butanol/octane/water microemulsion system and the two-microemulsion protocol, one aqueous pseudophase contained zinc nitrate while the other contained ammonium carbonate. X-ray diffraction identified the resulting calcined particles as ZnO with an average particle size of 14 nm. 

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