Selective recovery of Au(III) from aqueous solutions by nano-silica grafted with 4-(aminomethyl) pyridine

A new adsorbent was synthesized via functionalizing nano-silica with 4-(aminomethyl) pyridine for selective recovery of gold. The adsorbent was characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy and transmission electron microscopy, and BET (surface area and porosimetry analyzer). The results indicated that the maximum adsorption capacity of Au(III) was 55.5 mg/g at pH 4.0 and room temperature. The adsorption reaction was fairly rapid and reached equilibrium within 30 min. The adsorption processes of Au(III) were fitted well to the Langmuir isotherm model and adsorption kinetics of Au(III) followed the pseudo-second-order rate equation. The adsorption mechanism lies on the chelation and ion exchange between gold ions and amines/hydroxyl groups. The adsorbent had good reusability after five cycles. Moreover, 4-(aminomethyl) pyridine-Silica nanoparticles has a good selectivity in the adsorption of Au(III) from the coexisting ions. Therefore, 4-(aminomethyl) pyridine functionalized nano-silica could be of great potential as new adsorbent for the selective recovery of Au(III) from industrial effluents and waste e-products. [GRAPHICS]