An AF aerogel is an aerogel that has been developed using amyloid fibrils derived from whey, as an adsorbent for gold recovery from e-waste. Other earlier AF aerogels have been developed that use synthetic aramid fibers, in particular for thermal insulation. A study has demonstrated that protein derived AF aerogels have a high capacity for gold adsorption. Their use would have a less environmental impact than that of the conventional use of activated carbon as adsorbent.
Process.
Nanofibrils of protein amyloid derived from whey is a novel (as of 2023) adsorbent for the extraction of gold from electronic waste. Materials scientists at the Swiss Federal Institute of Technology developed the method. Prepared AF aerogels have a very high capacity for the adsorption of gold. 
The process begins with the separation of amyloid fibrils from waste dairy products, and their incorporation into an aerogel. The AF aerogel is then used in a solvent of dissolved computer motherboards (the main printed circuit board in a computer) to extract the gold contained. Af aerogels can convert gold (Au) ions into single crystalline flakes. The result is a yield of high purity gold nuggets, equating to around 21-22 carats, with only trace amounts of other metals present.
Economics.
The use of AF aerogels has a profitable profile. It costs just over one dollar to retrieve one gram of gold, and the market value of a gram of gold (as of 2023) is around 50 dollars.
Environment.
One ton of e-waste generates more than a hundred times more gold than a ton of gold ore. In a report by the UN to address the increasing issue of e-waste one of the solutions put forward was the use of "urban mining", to extract metals and minerals from e-waste.
The use of AF aerogels compares favourably in terms of environmental impact in comparison to the conventional use of activated carbon adsorbents.
References.
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