Electroless Displacement Deposition of Noble Metal on Silicon Powder for Recovering from Urban Mines

We developed a simple recovery method of all noble metals from aqueous solutions by adding silicon (Si) powder and fluoride. This method is expected to be low-cost, because the Si powder and the fluoride solution can be supplied from semiconductor industries, such as the sawdust Si of wafering or dicing and the waste hydrofluoric acid solution of wafer cleaning or etching. In this study, we investigated the recovery of noble metals using a low-toxic agent instead of a toxic hydrofluoric acid, or sawdust Si powder. This method can recover noble metals using ammonium fluoride or sodium fluoride. The recovery rate with sawdust Si is as high as that using pure Si powder. We found that the recovery of noble metals by this method from aqueous solutions including aqua regia is also possible.