Recovery of palladium and gold from pgm ore and concentrate leachates using fe₃ o₄ @sio₂ @mg-al-ldh nanocomposite

In this work, we developed a core–shell nanostructured magnetic composite by function-alizing layered double hydroxide (Mg-Al-LDH) microspheres with Fe₃ O₄ @SiO₂, for the recovery of Au(III) and Pd(II). The magnetic Fe₃ O₄ nanoparticles provided effective magnetic separation of the adsorbent from aqueous solutions. While silica protected the Fe₃ O₄ nanoparticles, increased the adsorption sites and the stability of the material. Finally, Mg-Al-LDH was chosen because of its large anion sorption capacities which lead to the improved adsorption capacity of Fe₃ O₄ @SiO₂ @ Mg-Al-LDH nanocomposite. The morphology and structural composition of the nanocomposite were characterized using various analytical techniques. It was satisfactorily established that silica was coated on iron oxide and layered double hydroxide was immobilized on Fe₃ O₄ @SiO₂ . Parameters affecting adsorption of the composite towards Au(III) and Pd(II), such as effects of sample pH, mass of adsorbent, extraction time, eluent type and concentration were investigated using response methodology based on central composite design. Maximum adsorption capacities of Fe₃ O₄ @SiO₂ @ Mg-Al-LDH for Au(III) and Pd(II) were 289 mg g⁻¹ and 313 mg g⁻¹, respectively. Under optimum conditions, the proposed method displayed good analytical performance suggesting that the adsor-bent is a good candidate for quantitative extraction of Au(III) and Pd(II) from secondary sources. Additionally, %recoveries ranging from 85%–99.6% were obtained revealing that Fe₃ O₄ @SiO₂ @ Mg-Al-LDH could selectively extract Au(III) and Pd(II) from leaching solutions of SARM 107 PGM ore and SARM 186 PGM concentrate.