Extraction of precious metals from industrial solutions by the pine (Pinus sylvestris) sawdust-based biosorbent modified with thiourea groups

A novel biosorbent based on pine (Pinus sylvestris) sawdust with chemical grafted thiourea groups was proposed for preconcentration of precious metals. A simple procedure was proposed for the synthesis of biosorbent by treating of sawdust with ammonium thiocyanate solution and a subsequent heat treatment at 160 degrees C. The biosorbent has been studied by thermogravimetry/differential scanning calorimetry (TGA/DSC), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FT-IR). The adsorption properties for precious metals ions (Au3+, Pd2+, Pt2+, Pt4+, Ir4+, Rh3+, Ru4+) extraction have been studied. Biosorbent quantitatively extracted precious metals from dilute solutions of hydrochloric acid (0.5-4.0 M). Iron and non-ferrous metals were not extracted in these conditions. The adsorbent showed high adsorption capacity for precious metals: 0.4 (Au3+), 1.7 (Pd2+), 1.0 (Pt2+), 0.8 (Pt4+), 0.45 (Ru4+), 0.55 (Rh3+), 0.4 (Ir4+) mmol/g. Biosorbent was used for extraction and preconcentration of precious metals from industrial solutions of refinery. Enriched for precious metals desorbing solution was obtained as a result. It is possible to obtain precious metals powder by combustion of biosorbent after adsorption of precious metals.