Batteries contain harmful metals and chemicals such as nickel cadmium, alkaline, mercury, nickel metal hydride and lead acid, which can contaminate the environment if not disposed properly. For example, when batteries containing cadmium are used in landfills, they will eventually dissolve and release the toxic substance that can seep into water supplies, posing serious health hazards for the population. This is why battery recycling has become so important because it helps prevent pollution, and also saves resources.
The Recycling Process
First of all, the batteries to be recycled are sorted according to chemistries such as nickel-cadmium, nickel-metal-hydride, lithium, alkaline etc. The combustible material, such as plastics and insulation, are then removed with a gas fired thermal oxidiser, which is the first step in the recycling process. Most recycling plants have scrubbers where the gases from the thermal oxidiser are neutralized to remove pollutants, producing clean, naked cells that contain precious metal content.
The metal in the batteries are then heated to liquefy, after they have been sawn into little pieces. Black slag left by burned out non-metallic substances are scraped off with a slag arm, and the different alloys that settle according to weight are skimmed off. Some plants pour the liquid metals directly into (65 pounds) or ‘hogs’ (2000 pounds) without separating on site, which are then shipped to metal recovery plants to produce nickel, chromium and iron re-melt alloy for the manufacturing of other metal products.
The mercury reduction in batteries, which had already started in 1984, is still continued today. For example, batteries such as those containing alkaline have had about a 97 percent mercury reduction, and newer models may contain about one-tenth the amount of mercury previously contained in the typical alkaline battery, or may be zero-added mercury. A number of mercury-free, heavy-duty, carbon-zinc batteries are now available as alternatives. Technology such as silver-oxide and zinc-air button batteries contain less mercury so they are starting to replace mercuric-oxide batteries. Nickel-cadmium batteries can be reprocessed to reclaim the nickel, and cadmium free nickel and nickel-hydride system are also being researched. At present, most nickel-cadmium batteries are permanently sealed in appliances but changes are being made in regulations which will result in a more convenient retrieval and recycling of nickel-cadmium batteries.
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