Toxic materials in the battery as a factor in the recycling of batteries

Toxic materials in the battery as a factor in the recycling of batteries

At the end of the battery’s service life, in order to protect the environment from the toxic effects of used batteries, its disposal becomes a key issue. For environmental safety, the harmful effects of lead and lithium in batteries must be eliminated. In the recycling plant, when the used batteries are dumped on the conveyor belt, the molten lead is converted into “ingots” called “metal blocks (ingots) pigs” and “hogs”. The operator places the recycled lead blocks on In a separate container. If it is a used lithium battery, it is processed and stored in a container that can be buried underground to avoid lithium toxicity leakage.

Toxic materials in the battery as a factor in the recycling of batteries
Used battery

The portability of electricity has become a part of daily life. Batteries are widely used in portable electrical and electronic devices, such as phones, computers, radios, compact discs, tape recorders, cordless tools, and even electric cars. But when the service life is reached, these batteries in turn bother us. The primary battery (primary battery, dry battery) used in the flashlight has a one-time use time, while the rechargeable battery can be charged thousands of times. From the viewpoint of environmental protection, rechargeable batteries classified as secondary batteries are superior to primary batteries in terms of saving materials. Therefore, a rechargeable battery is equivalent to dozens of primary batteries and saves the cost of recycling hundreds of primary batteries. In addition, life cycle cost is also one of the concerns of users.

Around the world, hundreds of millions of large batteries and millions of small batteries containing a large amount of toxic and hazardous substances are produced and used every year. Until recently, most batteries were simply discarded. However, due to the latest environmental regulations, lead-acid and industrial nickel-cadmium batteries are systematically collected in order to recover the toxic and harmful substances. Battery recycling requirements vary from country to country, and there is a clear trend that controls on requirements and disposal options will become stricter. The United States, Germany, France, and other European countries are actively considering more thorough regulations. A few decades ago, the European Union drafted a document requiring at least 80% of all industrial and automotive rechargeable batteries to be recycled. Recycling requirements are based on the materials used in the manufacturing process of rechargeable batteries. Only a small part of battery materials can be recycled and reused, which depends on three different factors:
·The ratio of batteries returned;
·The ratio of recoverable materials for each battery;
· The percentage of renewable materials actually recovered.
The recovery rate of lead-acid batteries exceeds 95%, the mass of recyclable lead in batteries is about 60%, and the efficiency of secondary smelting is about 95%. Taking all these factors into account, the mass of the recyclable part of the battery material is about 54%.

Toxic materials in the battery as a factor in the recycling of batteries
Toxic substances in batteries

① Toxic materials used in the manufacture of rechargeable batteries
Some toxic materials used in the design and development of rechargeable batteries determine the requirements for recycling and storage. Lead (Pb), cadmium (Cd), lithium (Li), vanadium (V), praseodymium (Pr), cobalt (Co), and manganese (Mn) are widely used materials in the manufacture of secondary batteries and primary batteries. Due to the mixing of rare earth elements such as lanthanum (La), neodymium(Nd), praseodymium (Pr), and cerium (Ce), mixed rare earth metals are produced. The configuration of rare earth elements in some alloys improves the electrode characteristics of the battery, that is, widens the temperature range, increases the specific power and energy density, extends the cycle life, and significantly improves the electrochemical activity. The characteristics of various rare earth elements and other elements widely used in rechargeable batteries are summarized in Table 1.

Elements used in alloyssymbolValence
cadmiumCd2
Cerium (RE)Ce3.4
cobaltCo2, 3
Lanthanum (RE)La3
lithiumLi1
manganeseMn2, 3, 4, 6, 7
Neodymium (RE)Nd3
nickelNi2, 3
praseodymium (RE)Pr3
sulfurS2, 4, 6
vanadiumV3, 5
zirconiumZr4
Note: RE is rare earth element
Table 1 Valence state characteristics of different rare earths and other elements used in battery alloys

Consumer batteries are generally relatively small and are discarded in municipal solid waste along with other items. When the waste reaches a landfill, water is first leached from the used and broken batteries, followed by nickel, cadmium, and mercury. High concentrations of metals are removed from landfills. When the waste enters the incinerator, the battery produces a high concentration of metal fumes in the chimney emissions and ash, which increases the cost of environmental control. Battery manufacturers claim that used batteries account for close to 1.5 to 06 tons of municipal solid waste. However, this amount is less than 1% of the total municipal solid waste generated. The solid waste contains about 67% lead, 90% mercury and more than 50% cadmium. In some countries, county and city regulatory authorities approve the removal of lead-acid batteries from municipal solid waste incinerators and landfills, requiring certification for the safe disposal of used batteries.

②Safety and toxicity restrictions for workers
In many industrially developed countries, the toxicity restrictions on workers’ handling of various toxic and hazardous substances are widely used in battery manufacturing. In addition, drinking water and ambient air standards also set toxicity limits. Under normal circumstances, the maximum allowable amount of the substance inhaled by a worker during an 8h working time is measured in milligrams per cubic meter (mg/m3). Nickel is 1mg/m3, lead is 0.15mg/m3, and cadmium is 0.005mg/m3.

Some advanced industrial countries have established strict guidelines for water supply facilities to protect their citizens from the adverse effects of toxic and harmful substances. Some countries have established maximum levels of pollutants (MCL), and drinking water above this level is considered unhealthy. The American MCL standard is 0.05mg/L for lead and 0.01mg/L for cadmium. The MCL in the United States does not specify the nickel content. The detailed adverse effects of lead, cadmium, mercury, nickel and their compounds are available on the US Environmental Protection Agency’s list. This list contains the Toxic Substance Emission Inventory (TRI) of chemicals, which is updated every five years.