Recovery of precious metals from e-waste - conventional & phytoremediation methods

What is it about?

E-waste, also known as waste from electrical and electronic equipment, is a solid waste that accumulates quickly due to high demand driven by the market for replacing newer electrical and electronic products. The global e-waste generation is estimated to be between 53.6 million tons, and it is increasing by 3–5% per year. Metals make-up approximately 30% of e-waste, which contains precious elements Au, Ag, Cu, Pt, and other high-value elements, valued at USD 57 billion, which is driving the e-waste recycling industry. It is noteworthy that the recycling of precious elements from e-waste has emerged as a profitable enterprise in several parts of developing nations. E-waste contains 50–100 times higher levels of precious metals compared to natural ores, making it suitable for mining. E-waste recycling in developing nations, mostly occurs through the informal sector comprising manual collection, crushing, segregation and selling of precious elements, such as Au, Ag, Cu, Pb, Pt, and other rare elements (Nd, In, and Ga). The organized sector, on the other hand, mostly employs mechano-chemical methods, such as pyrometallurgy, hydrometallurgy, and bio-hydrometallurgy, which have serious environmental consequences. Both the informal and formal sectors of e-waste processing lead to the leaching of toxic elements into groundwater and soils. Owing to the lesser efficiency of greener technologies, such as phytoremediation and bioremediation, their use in precious metal extraction is very limited. However, this review explores several hyper-accumulating and tolerant plants viz. Brassica juncea and Berkheya coddii, which holds great potential in phytomining of precious metal from e-waste. Thus, the state of the art in precious metal extraction from e-waste as well as the advantages and disadvantages of different metal extraction technologies has been reviewed.

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Photo by Tom Caillarec on Unsplash

Photo by Tom Caillarec on Unsplash

Why is it important?

Growing global challenge – Addresses rapidly increasing e-waste generation (53.6 million tons annually, growing 3–5% per year). Economic value – Highlights e-waste as a “urban mine” containing USD 57 billion worth of precious metals, far richer than natural ores. Environmental urgency – Exposes pollution risks from informal and formal recycling sectors, including toxic leaching into soil and water. Innovation potential – Reviews greener technologies like phytomining using hyperaccumulator plants, offering sustainable alternatives. Guidance for stakeholders – Provides a comprehensive overview of current extraction technologies, benefits, and limitations to inform policy, research, and industry practices.

Perspectives