Noble Metal Recovering by Electroless Displacement Deposition on Silicon Powder

We have developed a low-cost and efficient method to recover all noble metals, gold, silver, palladium, rhodium, platinum, osmium, ruthenium, and iridium, from those aqueous solutions by simply adding hydrofluoric acid (HF) and silicon (Si) powder. The recovery rate depends on the specific surface area of Si, concentration of HF, and temperature of solution. This method can selectively recover noble metals and copper from mixture solution of noble and base metal ions, such as nickel, cobalt, and iron, and obtain pure noble metal powder by dissolving Si. The Si powder and HF solution are expected to be supplied from semiconductor industries, such as sawdust Si of wafering or dicing and waste HF solution of wafer cleaning or etching. Thus, we can say that this new method recovers noble metal from waste (urban mines) by using other waste, and it is a green electroless deposition.