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Researchers from the University of Cambridge have developed a new method for recycling lead acid batteries which has the potential to transform the battery recycling industry.
The process, developed by Dr R Vasant Kumar and his research colleagues at the Department of Materials Science & Metallurgy, uses less energy, produces fewer toxic emissions and is more cost-effective than current methods.
Dr Kumar is presenting the technology this week at the International Secondary Lead Conference in Hyderabad, India.
Lead acid batteries are in wide use around the world, primarily in automobiles and other industrial applications. The batteries are relatively low in cost, have a large power-to-weight ratio, and can be recharged many times. Eventually, however, performance degrades and the batteries must be recycled, as lead is highly toxic to plants and animals.
The Cambridge process uses about 8% of the energy required by the conventional recycling process
In North America and Europe, more than 95% of lead acid batteries are recycled, as there is a well-established recycling infrastructure. In developing countries such as India, China and Russia, the same infrastructure does not yet exist, and automobile use is expanding rapidly. In the past, there has been little regulation of battery recycling in many of these countries, and the use of highly dangerous ‘backyard smelters’ is commonplace.
Over the past several years, there has been increasing regulation controlling the use and recycling of lead in developing countries, although the conventional recycling method used in the West is only economically viable at a large scale, making it too expensive for many small operators.
The conventional process involves dismantling the batteries, melting the spent battery paste in smelting furnaces at temperatures of 1000°C, pouring the molten lead into moulds, removing any impurities, and then re-melting the lead for use in new batteries.
The Cambridge process developed by Dr Kumar and his colleagues directly recovers lead oxide from the spent battery paste. The battery paste is mixed with citric acid and the resulting crystallites are heated to a temperature of 350°C, resulting in a mixture of lead and lead oxide, which can be used for the manufacture of new lead battery paste.
The Cambridge process uses about 8% of the energy required by the conventional recycling process and produces fewer emissions of toxic sulphur dioxide and lead dust. The new process is also much lower in cost, as it eliminates the expensive smelting step that converts the battery paste to metallic lead, which is then re-oxidised to lead oxide in the conventional process. The Cambridge process is also economically viable on either a small or large scale.
Cambridge Enterprise, the University’s commercialisation group, and the Nonferrous Materials Technology Development Centre (NFTDC) in Hyderabad are seeking commercial partners to establish a pilot scale plant for demonstrating the Cambridge process.
Ongoing research is supported by the UK-India Education and Research Initiative, the China Scholarship Council and Cambridge Enterprise.