**1. Introduction**

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105-114.

208 Modern Surface Engineering Treatments

341-358.

Electrical and electronic equipment have developed rapidly and their average life spans have been reduced due to the changes in functions and designs [1-3]. Recently, the recovery of precious metals from these electronic scraps has become attractive. Precious metals and copper in PC board scraps and waste mobile phones account for more than 95% of the total intrinsic value [4] and recently several authors are carrying out study on the applicability of economi‐ cally feasible hydrometallurgical processing routes to recover precious metals [3-5].

Due to this massive industrialization of electronic equipment like toys, cameras, laptops, cell phones, etc [6]. In recent years there has been a considerable increase in the consumption of household batteries The American industry invoice approximately 2.5 billion dollars annually selling about 3 billion batteries. In Europe in the year of 2003 were produced 160,000 tonnes of portable batteries. In this year in Brazil the annual production of these devices reaches about 1 billion units [7, 8]. In this way spent batteries represent an increasing environmental problem due to the high content of heavy metals. Unlike large batteries used for vehicles, small, portable batteries are very diverse in terms of chemical composition and represent 80–90% of all portable batteries collected [9, 10]. The difference between various types of used battery is represented by the used materials such as electrolytes and electrodes [9]. These batteries can be sorted by size, shape and chemical composition so that we can determine which metals can be recovered from each category.

© 2013 da Silva et al.; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2013 da Silva et al.; licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

For these reasons in several countries, collecting batteries is becoming mandatory, and so is recycling those containing toxic materials. Recycling may also be applied to recovering valuable materials to be reutilized [11].

lurgical process. In addition there is a diminishment of the emission of particles into the atmosphere. However, it is a more laborious process requiring pretreatment steps such as sorting, disassembling and leaching of material to improve the dissolution of metals in aqueous phase. In addition, the recovery of metals requires different aqueous media (acid or alkaline)

Electrodeposition of Alloys Coatings from Electrolytic Baths Prepared by Recovery of Exhausted Batteries for…

http://dx.doi.org/10.5772/56438

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The recovery of these materials is very important because in addition to reducing the enormous amount of waste generated by consume of these power devices, recycling could lower the cost of production of new batteries through the reuse of raw materials by recycling and, conse‐

Zn-C (also known as Leclanché or Zn-MnO2 Batteries) batteries and alkaline batteries are basically composed by potassium, manganese and zinc as metal species. The stack of Zn-C was invented in 1860 by George Leclanché and the devices currently used are very similar to

A schematic view of this type of batteries is showed in Figure 1. In these batteries the anode consists of a zinc metal cylinder used, usually in the form of plate to procedure the outside structure of the cell. The cathode consists of a graphite rod surrounded by a powder mixture of graphite and manganese dioxide. The electrolyte is a mixture of ammonium chloride and zinc chloride. During the Zn-C and alkaline batteries discharge, basically the following


In this kind of batteries, during storage and in rest periods while operating some parallel reactions can occur, causing leaks and loss of efficiency. In this way, some metals such as Cd,

( ) - - <sup>4</sup> 32 2 <sup>2</sup> Zn + 2NH Cl + 2OH Zn N ® H Cl + 2H + 2 e <sup>O</sup> (1)

2 2 2MnO + 2H O + 2e 2OH + 2MnOOH ® (2)

( ) 2 4 3 2 <sup>2</sup> Zn + 2MnO + 2NH Cl Zn NH Cl + 2MnOOH ® (3)

and various processes of precipitation [14, 18, 19].

quently it reduces the risks to the environment [19, 20].

**2. Features of Zn-MnO2 batteries**

the original version.

reactions are observed:

Zinc oxidation at anode:

Manganese reduction at cathode:

Resulting in the overall reaction:

There are basically two types of household batteries: primary batteries that after becoming worn are discarded and the secondary batteries that can be recharged [12, 13]. Within the wide range of commercially available batteries zinc-carbon batteries (also known as Leclenché or dry cells) and alkaline batteries are the most consumed because of its low cost. In Europe, from the total of batteries sold in 2003, 30.5% and 60.3%, were Zn-C batteries and alkaline batteries, respectively. In China are produced annually more than 15 billion of these devices and in Brazil estimating a consumption of six batteries per inhabitant per year [7, 8, 14].

The disposal of these batteries is a serious problem, because in their composition there are metals considered dangerous to the environment [13]. The cost for the safe disposal of these materials is quite high due to the large amount of dangerous waste generated and due to the fact that the storage capacity in landfills or dumps is running out. A policy adopted in 2006 by the European Union (EU) banned incineration and disposal of batteries in landfills. This regulation applies to all types of batteries regardless of shape, volume, weight, composition or use. Through this new policy it is expected to mobilize the EU countries member for the collection, recovery and recycling of metals present in these power devices [15]. In Brazil, according to the resolution 401/2008 of the *Brazilian National Council of the Environment* (CONAMA in Portuguese) [16], after consumption, household batteries must be collected and sent to the manufacturers, to be recycled, treated or disposed of an environmentally safe way, but until 1999 they could be disposed of in household waste since meet the limits of heavy metals in its composition. Although required, this resolution proved to be insufficient to solve the problem of environmental contamination by means of this waste since there is a large annual consumption of these batteries. A factor to be noted is that in spite of Zn and Mn match most of the composition of cells Zn-MnO2, the limits of contamination of these metals are not established by law. Another aggravating factor is the use of irregular cells entering the Brazilian market. Frequently these products do not meet manufacturing standards. The heavy metal content of these cells is seven times greater than that limited established by the CON‐ AMA. Thus, the contamination starts by improper disposal of these devices in landfills or dumps, which is the destination of the majority of household solid waste in Brazil [13,16, 17].

Industrial recycling of batteries is generally focused on two processes: the pyrometallurgical and/or the hydrometallurgical. The pyrometallurgical method is based on the difference of volatilization of different metals at high temperatures followed by condensation. The hydro‐ metallurgical method is based on the dissolution of metals in acidic or alkaline solutions. The advantage of the first method is the absence of the necessity of dismantlement of the devices. However, it is an expensive process, since it requires high temperatures and is not efficient selectively, for example, to obtain pure zinc from Zn-MnO2 batteries, Ni-Cd batteries cannot be treated simultaneously because the Zn and Cd are not selectively volatized in the oven, so sorting steps are required in advance of the materials recycling. Another drawback is related to the production of dust and gas emission into the atmosphere during the recycling process. The hydrometallurgical route is usually more economical and efficient than the pyrometal‐ lurgical process. In addition there is a diminishment of the emission of particles into the atmosphere. However, it is a more laborious process requiring pretreatment steps such as sorting, disassembling and leaching of material to improve the dissolution of metals in aqueous phase. In addition, the recovery of metals requires different aqueous media (acid or alkaline) and various processes of precipitation [14, 18, 19].

The recovery of these materials is very important because in addition to reducing the enormous amount of waste generated by consume of these power devices, recycling could lower the cost of production of new batteries through the reuse of raw materials by recycling and, conse‐ quently it reduces the risks to the environment [19, 20].
