Researchers from Kanazawa University developed a new way to extract rare metals from waste.

Rare metals are in scarce supply and high demand. Ideally, these metals would be recycled from waste and reused in new electronics. But current recycling methods are complex, expensive, toxic, wasteful and generally inefficient. The team improved the method of recovering silver palladium ions from aqueous acidic waste.

Source: Chemical Engineering Journal / Kanazawa UniversitySource: Chemical Engineering Journal / Kanazawa University

The recovery of metals in elemental, metallic form is fairly straightforward: burn the waste and gather the remaining metal. The team chemically modified ultrasmall particles of cellulose. Cellulose is an abundant and non-toxic biopolymer. The modified cellulose selectively absorbs silver and palladium ions at room temperature. Absorption is nearly complete at the acidic pH with acid concentrations of around one to 13% by volume. The new method does not require cyanide or toxic elements.

The maximum metal ion absorption using the new method was fast. Silver absorption was completed in one hour. Typically, maximum adsorption would require hours with other approaches. After absorption, the team incinerated the cellulose particles to get silver or palladium powder. Higher temperature incineration converted the powder into pellets. Spectroscopic analysis showed that the final metal pellets stayed in metallic form rather than in oxide form.

Palladium and silver are valuable metals that are in limited natural supply. The new method could be a step towards recycling more rare materials and saving them from being wasted.

A paper on the new method was published in Chemical Engineering Journal.