Newer ways to recover metals

The last year has been a year of metals, with the entire world scrambling to get ahead in the race for precious metals. With silver, copper, and other rare metals becoming more important than ever due to solar and electric vehicles, every country is seeking alternative sources for these metals beyond mining. 

The focus has also been on e-waste, the fastest-growing solid waste stream worldwide. This contains a combination of precious and rare metals, such as copper, iron, tin, lead, cadmium, palladium, and even gold and silver, in relatively pure form. Recovering these metals, however, is not easy. In India, some of this waste ends up in informal disposal sites, such as landfills, due to inadequate and unsafe recycling mechanisms.

The Global E-Waste Monitor 2024 estimates that 62 million tonnes of e-waste were generated worldwide in 2022. This figure is expected to rise to 82 million tonnes by 2030. Central Pollution Control Board (CPCB) data shows that India generated over 1.6 million tonnes of e-waste in 2022–23. 

Conventional recycling methods like pyrometallurgy and hydrometallurgy rely on very high-temperature processing and strong acids to recover metals in their pure forms. These methods release harmful gases, generate hazardous chemicals and expose workers to unsafe conditions.

“India relies heavily on technologies used by Japan, South Korea, and European countries to recycle e-waste,” says Sinu Kurian, a researcher from the Indian Institute of Technology, Madras, adding that greener, more efficient ways to do this using raw materials available within India are necessary.

Motivated to address the environmental costs of existing methods, her team at IIT Madras used a thymol-capric acid deep eutectic solvent (DES) to recover metallic copper from e-waste sources such as printed circuit boards. A DES is a mixture of two or more compounds formed through extensive hydrogen bonds to lower their melting points, resulting in the solvents staying in liquid form at room temperatures.

Sinu Kurian, the lead researcher in the study, says that thymol-capric acid DES combines thymol, derived from plant-based sources like thyme and ajwain, with capric acid, commonly found in coconut and palm kernel oils and milk fat, making the blend environmentally friendly. 

In her experiment, Sinu dissolved 0.2 g of copper powder in 25mL of thymol-capric acid DES. She then added trisodium citrate
to copper-dissolved DES, which separated
the mixture into two layers: a reusable DES layer and an aqueous phase containing
copper ions.

Sinu said that this method was tested on printed circuit boards of mobile phones. Identical results were obtained in each case. The same method was followed for iron to establish the effectiveness of green solvents in dissolving other metals.

According to Sinu, this method simplifies the steps involved in metal extraction by limiting the use of water and does not require strong solvents. She believes that once the protocol for her study is established, this method can be scalable to people and industries. At the moment, however, the method is achievable only in labs.

This raises a larger question: how then is e-waste actually recycled in India today? 

From scrap to steel 

Under government rules, all electronic and electrical equipment manufacturers in India must obtain an Extended Producer Responsibility (EPR) certificate, making them accountable for the safe disposal of end-of-life products. 

Recyclers say that more than three-fourths of the total e-waste produced in India is estimated to be handled by the unorganised sector, largely run by local dealers, with little documented information on recovery
practices.

However, a growing number of registered solid waste management companies are shifting towards e-waste processing units that extract metals in their pure form and sell them to various manufacturing companies.

Ravi Kumar Neeladri, chief executive officer of Blue-Planet E-Waste Solutions Private Limited, whose plant is near Hoskote, says that the metals extracted in the highest amounts at their factory are aluminium, copper and iron. 

“After sourcing end-of-life products, we first segregate plastics from e-waste manually. Then the metallic components are melted down, or smelted, after which the impurities from the slag are removed using hydrochloric acid (HCl),” he said.

He explained that scrap plastics from segregated e-waste are shredded into small flakes. These flakes are then supplied to Original Equipment Manufacturers (OEMs), who convert them into granules. 

He says iron is the most commonly found metal in e-waste, followed by stainless steel, aluminium and copper. Silver and gold are also found in minor quantities in the PCBs of most electronic equipment.

“Due to high precision technology and higher cost of extraction of precious metals, which are found in micrograms compared to other metals, which are available in kilograms, we don’t extract them yet,” he notes, adding that the extraction of rare earth elements faces a similar challenge.

“We use a PCB recycling machine that converts circuit boards into powders. The powdered PCBs are exported to a company in Japan where they extract copper, silver and gold,” says Ishita Bansal, co-founder and COO of Plannex Recycling. She adds that iron, aluminium, and other commonly found metals are extracted at the Plannex factories and sold to manufacturing companies. 

Recyclers and researchers say that India needs to invent a greener route to recover its e-waste. 

Satish Sinha, Associate Director of Toxics Link, a Delhi-based policy advocacy firm that also works in the e-waste sector, notes that India’s biggest challenge in managing e-waste begins at the source.

He says the major gap in E-Waste (Management) Rules, 2022, is the lack of an effective collection and recycling system, especially in rural areas, along with weak enforcement, limited recovery of valuable and critical metals and insufficient integration of the informal sector into the formal e-waste management framework.

(The author is a freelance journalist)