Why does everyone want the silver in an old solar panel, and can you get it out without a vat of nitric acid? French researchers say you can. They report recovering more than 98% of the silver in the lab with a two-step process that skips nitric acid and leaves the cleaning liquid fit for another round.
The work comes from CEA, the French research organization, and appeared in the journal Hydrometallurgy. It was funded under the EU's Horizon Europe EVERPV project, which CEA coordinates. These are the team's own results, proven in a 20-liter reactor, which is a long way from a recycling plant.
Why does silver matter so much in recycling?
Silver is a sliver of the waste by weight, well under 1%, yet the researchers say it makes up roughly 60% of a module's economic value, citing earlier studies. Picture a fruitcake where the few expensive nuts are worth more than the whole cake. If a recycler can't pull the nuts out cleanly, the business doesn't pay.
That is why silver drives the economics of panel recycling, and why recovery rates have been climbing. Data gathered by the International Energy Agency's solar research program put US recycler Solarcycle at nearly 92% at commercial scale, with Italy's 9-Tech around 90%. A University of Newcastle team reported 97% with froth flotation in January, and EU projects such as EVERPV and Photorama are building pilot lines aiming for the mid-to-high 90s.
What is different about this method?
Most liquid-based routes (hydrometallurgy, meaning chemistry done in solutions instead of furnaces) dissolve the silver in nitric acid and then precipitate it out. The researchers say that creates nitrogen oxide emissions and nitrate-heavy waste water. Methanesulfonic acid works about as well, but it is pricey and hard to regenerate.
The CEA team turns the problem around. Rather than dissolving the silver, they dissolve almost everything else. A hot bath of hydrochloric acid with hydrogen peroxide eats through more than 98% of the aluminum, copper, lead and zinc. The silver reacts at the surface and forms a shell of silver chloride that doesn't dissolve, shielding the metal beneath. Only a small fraction of the silver, under 2%, is lost this way.
Because the silver stays solid, the acid solution isn't spent and can be reused over several cycles. A second step then separates the silver from leftover silicon by density, and the final product is a silver and silver chloride composite of about 97% purity.
What is the catch?
The composite isn't finished silver. It still needs refining, such as chemical reduction or electrowinning (using electric current to plate out pure metal), before it's ready to sell. The input is also specialized: a metal-rich powder made by sanding delaminated old modules layer by layer, a step the group described in a separate paper.
So the chemistry is one link in a longer chain. The article we read gives no cost figures and no timeline for commercial use, and we couldn't confirm either. It also doesn't say whether existing refiners would buy a 97% composite as it comes out of the process, or what that last refining step would cost, which is exactly what a recycler would need to know to judge its returns. We haven't spoken with the CEA team or with a commercial recycler, so there is no direct quote from either here, and everything above rests on the published account. The same group has also reported a mild oxalic acid method for recovering indium from heterojunction cells, which suggests a broader push toward gentler panel recycling.
The short version: the pitch is a process that dissolves the junk and leaves the valuable part alone, with fewer toxic by-products and a liquid you can reuse. The results are promising, but working recyclers already report around 90% at scale, so the real test is whether this can match them on cost and handle messy industrial feedstock. Would you trust a recycler more if it could show you a nitric-acid-free process?
That's wattsup, and here's wattsnext.
Sources
- 1.Nitric-acid-free process recovers more than 98% of silver from PV waste - pv magazine Global · pv magazine Global
Reported by the WattsUpNext desk from the sources linked below. Spot an error? Tell us at corrections@wattsupnext.com.
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