Recovery of Precious Metals by Selective Adsorption on Dimethylamine-Modified Persimmon Peel

Dimethylamine (DMA) functional group was grafted to obtain modified persimmon peel gel (DMA-PP) with the focus of development of selective recovery of gold as well as other precious metals like palladium and platinum. The adsorption behavior of the DMA-PP gel for various metal ions at varying hydrochloric acid concentrations has been studied. It was found that the DMA-PP exhibits high affinity for Au(III) as well as for Pt(IV) and Pd(II) and no affinity for base metals such as Cu(II), Fe(III), Ni(II), and Zn(II) under the operating conditions. The valuated apparent activation energy value suggests that adsorption of Au(III) on the DMA-PP gel is a chemical process. Another important result is that the size of the gel has an important effect on kinetics of the adsorption and reduction of Au(III). The application of this gel which has very high adsorption capacity and selectivity avoids the use of any additional reducing agents for the recovery of Au(III) in elemental form. In addition, its excellent adsorption characteristics for the precious metals were confirmed under dynamic conditions of column operation.