In this article we will look at how Batteries and Accumulators (RPA) are treated and disposed of, that is, the process that is used to date for recycling and raw material recovery.
Methods of treatment of spent lead accumulators
Lead-acid accumulators, used in industrial and automotive applications, at the end of their life cycle will be destined to undergo treatment operations so that the materials from which they are made can be recovered and recycled almost in their entirety. The National Battery System - Sinab Consortium, thanks to the presence of qualified partners equipped with state-of-the-art facilities for the treatment of lead-acid accumulators, is able to recover most of the recyclable components of a spent accumulator. On average, a new lead-acid accumulator consists of lead, acid (aqueous solution of sulfuric acid) and plastic material; the average weight of a new vehicle accumulator is 14 kilograms.
At the end of its life cycle, a spent accumulator can be considered to consist of:
- Lightweight plastic (polypropylene) outer casing;
- Heavy plastic parts (polyethylene, PVC);
- Electrolyte (aqueous solution of sulfuric acid);
- Lead nets and poles (grids, metallic lead);
- Pastel (lead oxide, dioxide and sulfate).
Exhausted accumulator: what to do?
A significant role in the context of the spent accumulator is assumed by the so-called crayon consisting properly of lead salts and oxides; these substances result from the lead oxidation-reduction process that is triggered once the new battery is used as well as from the reduction of the concentration and amount of acid solution in the accumulator.
The accumulator, once it has exhausted its capacity for use, will be transported by the producer to municipal ecological yards or to retailers equipped with collection bins, or it will be picked up by authorized firms from non-household producers; once the different batches of waste have been amalgamated, they will be directed to specialized firms that, from the treatment of the exhausted product, are able to derive various materials that can be reintroduced into primary production cycles such as:
- Lead foundry;
- Grinding plants for plastics;
- Chemical companies for sulfuric acid.
The treatment plant, aimed at recovering the different components of lead accumulators, usually consists of the following industrial steps:
- Storage and handling of spent accumulators;
- Grinding of spent accumulators in mill;
- Washing and separation of material from shredding;
- Collection and disposal of materials.
Waste products from lead-acid accumulators
The entire lead-acid accumulator treatment process will result in a series of atmospheric emissions that will be properly monitored and guarded by pollutant abatement equipment. The same production process will generate a number of waste products that cannot be recycled in particular:
- The electrolyte, in addition to being given to chemical companies, can be neutralized and reused as technological water for washing accumulators;
- Some heavier synthetic components, such as hard rubbers, will have to be landfilled as hazardous waste;
- From the pyrometallurgical process of lead-based products, metallurgical slag (iron oxides and sulfides) is generated, which will have to be disposed of, after grinding, in landfills as hazardous waste;
- Solid waste will be generated from the treatment of industrial fumes and emissions to be disposed of in landfills as hazardous waste.
Mode of end-of-life treatment of batteries
If for electrical and electronic equipment and lead accumulators there are a whole series of well-established treatment processes that lead, as an end result, to the separation of the different components destined for recycling or final disposal, the same cannot be said in the varied world of batteries composed of a plurality of products that can be summarized here, non-exhaustively, as zinc-carbon batteries, zinc-chloride batteries, alkaline batteries, lithium batteries, zinc-air batteries and zinc-silver batteries.
In any case, these treatment systems, usually referred to as hydrometallurgical, also consist of:
- Initial classification;
- Grinding of selected material;
- Separation as a function of grain size;
- Separation (magnetic or electrostatic);
- Chemical treatments within reactors that will lead to dissolution or sedimentation of metals.
Such treatment processes will involve the recovery of various materials such as zinc, manganese, metal alloys, paper, and plastics; generally good recycling yields occur from zinc carbon batteries and alkaline batteries. The placing on the market later of batteries containing toxic substances, such as cadmium, makes it essential that treatment systems provide for the recovery of such metal before it comes into contact with operators or the external environment; for this reason, it is possible that, in addition to the treatment steps previously listed, some specifically designed for the extraction of such toxic materials will be included.
