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Circuit Board Waste Mops Up Toxic Metals

Date:2014-12-16

Researchers in Hong Kong have found a beneficial new use for the electronic waste from discarded cell phones, computers, and other gadgets. Ground up into a powder, printed circuit boards from these products could sponge up another type of pollutiontoxic heavy metals in water.

              

About 20 to 50 million tons of electronic waste is produced worldwide each year, and most of it is incinerated or dumped into landfills. Environmental scientists worry about the ecological and human health hazards caused by this e-waste, especially in developing countries that receive the bulk of the waste. Burning the plastic-metal mix in printed circuit boards releases toxic compounds such as dioxins and furans. In landfills, the metals on the boards can eventually contaminate groundwater.

But recycling circuit boards is expensive. Only the metal parts of the boards have reuse value, so the nonmetallic parts must be separated out from the e-waste, which is a costly process.

 

To make e-waste recycling more economically viable, Gordon Mckay and his colleagues at the Hong Kong University of Science & Technology began investigating uses for this nonmetallic fraction, which is made of plastic and aluminosilicates. The team had previously developed adsorbent materials to remove toxic heavy metals from wastewater effluents produced in the microelectronics industry. They thought the aluminosilicate material in the circuit boards would make an effective adsorbent

materials, similar to zeolite materials currently used for this purpose.

 

To test this idea, McKay and colleagues worked with a powder made by grinding up the nonmetallic fraction of circuit boards. They heated it and treated it with potassium hydroxide, which is a common technique used to increase porosity in carbon-based adsorbents. The team then added the powder to solutions of copper, lead, and zinc.

 

The researchers are now conducting a pilot study to make a 10-kg batch of the adsorbent resin, and they are discussing developing the project on an industrial scale with an electronic waste recycling company in Hong Kong, McKay says. He thinks the ideal application for the new adsorbent materials  would be to treat wastewater effluent from electronics production. “It would be quite a nice complete circle,”he says.

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