Tackling e-waste the ‘microbial’ way

Scientists extract up to 92 per cent metals from disposed mobile chargers

Written by ANJALI MARAR | Pune | Published: December 7, 2017 4:51 am
Their disposal, experts said, is trickier, due to the inclusion of a wide range of metals, some of which are toxic.

MOBILE CHARGERS are an inevitable part of our lives, but, once rendered non-functional, they are among one of the most disposed-off electronic waste items found at any e-waste scrap market.

A team of scientists from Maharashtra recently conducted a study and developed a unique ‘microbial solution’ for the problem, through which they could extract up to 92 per cent of the metal components from a defunct charger. This would make their disposal safer. The study was recently published in Environmental Science and Pollution Research.

With every Indian household today possessing an average of at least three chargers, the item has increased the huge burden of e-waste in the country by several folds. Their disposal, experts said, is trickier, due to the inclusion of a wide range of metals, some of which are toxic. For instance: a mobile charger, when disintegrated, can typically come across as a Printed Circuit Boards (PCBs), a plastic body, heat sink, condensers and transistors. As part of the study, researchers visited various scrap markets in Aurangabad. They bought at least 12 chargers — one of every make and manufactured under the same batch — each at the cost of Rs 10.

Lead researcher Nitin Adhapure from the Department of Biotechnology and Microbiology at Vivekanand Arts, Sardar Dalipsingh Commerce and Science College, Aurangabad, said, “Over a 1,000 chargers were found at these markets… It took us about a fortnight and several visits to the markets to find the chargers.”

The team then cleaned and tested the PCBs by immersing them into a liquid enriched with the potential microbes — Acidiphilium, Leptospirillum, Sulfobacillus, T caldus and A ferrooxidans, among others, which are believed to extract the metals. Some of the common metals polished on circuit boards include copper, nickel, zinc, iron, silver and lead, with copper being highest in proportion. Experiments to extract the metals were conducted on both pulverised (fine particles) and non-pulverised boards, to test their feasibility. Metal extraction from the pulverised boards was found to be higher, said a team member.

Arvind Deshmukh, former head of Microbiology Department at Dr B A M University, Osmanabad, said, “…within 144 hours of chemical processing and electrolysis, we managed to extract up to 92 per cent of the actual copper composed on the board”.  Maximum amounts of both zinc and lead were extracted within the first 48 hours of the processing, the team added.

Prashant Dhakephalkar, senior microbiologist with Agharkar Research Institute (ARI), said, “The advantage of the microbial solution is that these microbes are autotrophic — they are self-sufficient and can grown on their own,helping cap the cost of the solution.”  “Nature has provided us with numerous microbes, possessing unique characteristics to address our problems. We just need to identify them and put them to the best of use in an most eco-friendly manner,” he added. He said, “Calculation for the metal extraction using this method suggests that from one litre of the solution, the extraction cost would be less than a rupee. These metals can later be reused or sold.”

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