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Chinese researchers have discovered a fast, low-cost and environmentally cleaner method for extracting gold from electronic waste, that could significantly reshape e-waste recycling worldwide and reduce the need for traditional mining.
The technique, said to the be easiest means to extract gold from discarded electronics withing 20 minutes at room temperature, was developed by researchers from the Guangzhou Institute of Energy Conversion under the Chinese Academy of Sciences and South China University of Technology.
The redearch team reported that the new process costs about one-third of current market prices for gold recovery, which makes it the most cost-efficient method currently. It also achieves more than 98.2 percent gold leaching efficiency from waste Central Processing Units (CPUs) in old mobile phones and Printed Circuit Boards (PCBs) from home appliances at room temperature. According to the World Health Organisation (WHO), electronic waste (e-waste), one of the fastest growing solid waste streams in the world, records 2.6 million tons of e-waste annually, with the potential of rising to 82 million tons by 2030. The most common e-waste items include computers, large household appliances, mobile phones and medical equipment.
These items contain small but valuable amounts of precious metals, including gold (Au) and palladium (Pd), which are widely used for their excellent conductivity, stability and corrosion resistance. Meanwhile, conventional recycling methods often rely on toxic chemicals such as cyanide, posing serious environmental and health risks. To address the challenge the team, whose study outcome has been published in the Angewandte Chemie International Edition, developed a process based on a selfcatalytic leaching mechanism.
The mechanism eliminates the need for corrosive reagents or external catalysts. In contrast it uses a simple aqueous solution of potassium peroxymonosulfate (PMS) and potassium chloride (KCl). When the solution comes into contact with gold or palladium surfaces, the metals themselves behave as catalysts. On the metal surface, PMS and chloride ions (Cl) are activated, producing highly reactive oxidants such as singlet oxygen and hypochlorous acid.
These oxidants then break down the metal atoms, and allow the chloride ions to bind to them and dissolve them into the solution for easy recovery.
For the study, the team carried out quenching experiments and spectroscopic analysis.
The researchers noted that the method achieves over 98.2 percent gold leaching efficiency from waste central processing units (CPUs) and printed circuit boards (PCBs), along with a 93.4 percent palladium recovery rate.
This means that processing just 22 lbs (10 kilograms) of discarded circuit boards can yield around 1.4 grams of gold at a total cost of roughly USD 72. This is equal to about USD 1,455 per ounce, which is far below current market prices.