University of Newcastle researchers have conducted a continuous pilot-scale trial of their acid-free silver-recovery process
The process combines mechanical crushing and grinding with froth flotation using water, air, and small quantities of reagents
Nearly 100% of the silver was recovered and concentrated into a material weighing only 1.25% of the original solar-cell feedstock
As growing numbers of solar panels reach the end of their operating life, recovering their valuable materials remains a challenge. Silver is the highest-value material in a crystalline silicon solar cell, but separating it from the other materials can require chemical-intensive processes that generate hazardous waste.
Researchers at Australia’s University of Newcastle have developed an acid-free silver-recovery process based on froth flotation, a separation technique widely used in the mining industry. The team has advanced the process from small batch experiments to a continuous pilot trial (see Researchers Develop Acid-Free Method To Recover Silver From Solar Panels).
The first step is comminution, in which the panels are crushed and ground into fine particles. The material is then subjected to froth flotation using water, air, and small quantities of flotation reagents. The reagents enable the silver-bearing particles to attach to air bubbles and float to the surface, separating them from the other materials without using acid.
During the trial, the researchers processed around 22 kg of solar-cell material obtained from approximately 460 kg of end-of-life panels, equivalent to about 23 residential modules. They recovered nearly all the silver and concentrated it into a product representing just 1.25% of the original cell material. The silver concentration in this product was more than 80 times higher than in the initial feedstock.
The trial builds on the team’s earlier small-scale batch research, which demonstrated silver recovery of more than 97% within a few minutes.
Associate Professor Mahshid Firouzi, Deputy Director of the University of Newcastle’s Centre for Critical Minerals and Urban Mining (CRITIUM), explained the significance of the latest trial. “Our earlier small-scale batch research proved flotation could recover silver from solar panels,” said Firouzi. “This latest work demonstrates that the process can operate continuously at a much larger scale with nearly 100% silver recovery, bringing us closer to commercial implementation.”
The team’s preliminary economic assessment suggests that the flotation-based process could be 3 to 5 times less expensive than conventional acid-leaching methods. According to the university, recycling currently costs approximately AUD 10 to AUD 15 per panel in Australia, compared with only a few dollars for landfill disposal. The researchers believe revenue from recovered silver could help narrow this cost difference.
