Circuit boards to building blocks
19 August 2008
Old circuit boards could be turned into tough planks to make fences or park benches, thanks to a new process developed by scientists in China.
While circuit boards contain toxic materials that contaminate soil around landfill sites or release noxious gases if incinerated, they also contain high levels of copper and aluminium, as well as precious metals like gold and palladium. These valuable metals can be extracted during recycling but the process leaves behind a large amount of non-metallic material.
This circuit board 'pulp' consists of the glass fibres and epoxy resin that make up circuit board bases and often ends up in landfill. Now, chemists at Jiao Tong University, Shanghai, have found a way to turn this pulp into planks that are nearly as strong as reinforced concrete.
The researchers first crush circuit boards into a fine powder and then use an electrostatic separator to remove any metallic components. Next, the non-metallic powder is added to a carefully-mixed solution containing unsaturated polyester and kneaded together to make a 'dough'. This can then be heated and pressed into shapes.
'We tested the strength and hardness of our planks and showed that they have properties that are comparable with other building materials,' says Zhenming Xu, the leader of the research team. 'We are confident that this material can be used for making products such as fences, sewer grates or park benches.'
Electronic waste is a growing problem, with millions of tonnes being thrown away every year. Xu says around 300,000 tonnes of circuit board are disposed of every year in China alone. Where precious metals are already being extracted from the old boards, Xu is confident that a further step to convert them into planks could be made economically viable.
'Recycling non-metallic materials from waste printed circuit boards is essential for managing electronic waste,' says Jirang Cui, an expert on e-recycling at the Norwegian University of Science and Technology (NTNU) in Trondheim, Norway. 'This is a good idea, but there are still some challenges to overcome. For example, the team need to ensure that any residual metals do not affect the properties of the plates.'
Xu acknowledges that there is still work to be done. The team are currently carrying out further tests to evaluate whether the boards can stand up to outdoor conditions.
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J Guo et al, Environ. Sci. Technol., 2008, 42, 5267 (DOI: 10.1021/es800825u)
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