Recovery of Au(III) from leach solutions using thiourea functionalized zeolitic imidazolate frameworks (TU*ZIF-8)

Abstract

Metal organic frameworks (MOFs) have diverse applications in adsorption/separation fields. However, little is known about MOFs as adsorbents for the adsorption of Au(III) from aqueous solutions. In this work, a highly porous MOFs, ZIF-8, was modified by thiourea (TU) via coordination-based post-synthetic modification strategy. Compared with pristine ZIF-8, the TU functionalized ZIF-8, TU*ZIF-8, exhibited a remarkable Au(III) adsorption ability with a saturation adsorption capacity of 4262.8 mg/g although its surface area and pore volume decreased with TU loading. Interestingly, the adsorption efficiency of Au(III) was >99% with a broad Au(III) concentration range of 50–400 mg/L using only 20 mg TU*ZIF-8. Meanwhile, TU*ZIF-8 showed an encouraging selectivity for Au(III) in the presence of some metal ions such as Cu(II), Cr(VI), Pb(II), Cd(II), Mn(II), Mg(II), and Co(II). The improved adsorption of Au(III) on TU*ZIF-8 is explained by the synergistic effect of electrostatic interaction and coordination interaction. Particularly, the coordination interaction between Au(III) and TU of TU*ZIF-8 plays a major role in the Au(III) adsorption process of TU*ZIF-8. This work suggests a potential application of functionalized MOFs for the efficient recovery of gold from aqueous solutions.