Science and Technology

Digging for gold in digital dumps

M. Ramesh | | Updated on: Mar 14, 2021
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IIT Delhi team patents eco-friendly tech to recover fuel and metals from e-waste

It is not unknown that there is wealth lurking in electronic waste. Some of the stuff that resides in e-waste are lead, cadmium, chromium, biphenyls and an assortment of metals such as copper, zinc, silver and gold.

In 2019, India produced 3.23 million tonnes of e-waste. Globally, 63.7 million tonnes of e-waste was generated during the year, according to the Global E-waste Monitor Report 2020. This is set to grow to 75 million tonnes by 2030.

You extract all the goodies in the e-waste, you are a rich person.

A team led by KK Pant, professor in the Chemical Engineering Department of IIT Delhi, has set out to mine the wealth from electronic dumps. The result of his efforts, funded by the Department of Science and Technology, is a technology to do so.

It involves a three-step process: Pyrolysis (decomposition of materials in high temperatures), separation of metals, and recovery of individual metals.

First, the waste is shredded and heated at high temperatures. This process produces liquid and gaseous fuels, leaving behind residues that are rich in metals and some carbonaceous material. The carbonaceous material is used for making aerogel, which has many industrial applications.

Then, a low-temperature roasting technique is employed to recover metals such as copper, nickel, lead, zinc, silver and gold from the metal mixture. According to a write-up on the subject in IIT Delhi’s website, the process can recover 93 per cent copper, 100 per cent of nickel, zinc and lead, and 50 per cent of gold and silver present in the residue. “It is a green process in which no toxic chemicals are released into the environment,” says IIT Delhi.

For their project, titled ‘Self-Sustainable E-waste Recycling: Generating Wealth from Waste via Zero Discharge Technology’, the team was awarded the 2020 SRISTI-GYTI (Gandhian Young Technological Innovation) Appreciation,besides other awards over the last five years.

The team has successfully installed a 10 kg/h (kilogram per hour) pyrolysis plant for e-waste recycling at IIT Delhi. It converts all types of e-waste into combustible gases of 28 MJ/kg calorific value, liquid fuel of 30 MJ/kg calorific value, and a metal-rich solid residue. The gaseous product is primarily composed of hydrogen and methane whereas the liquid product is rich in hydrocarbons suitable for energy generation. The pilot plant is also equipped with a scrubbing system to capture halogenated compound traces in the combustible gases.

Pant says his team has successfully demonstrated the application of the technology for recycling discarded printed circuit boards, computers and mobile phones. It can also be employed for recycling plastic waste.

Besides providing a sustainable solution for e-waste recycling, the technology has the potential to generate jobs in the waste recycling industry.

The technology has been patented and published in the Journal of Cleaner Production , Journal of Hazardous Materials , Waste Management and the Journal of Environmental Chemical Engineering .

Published on March 14, 2021

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