Thia-crown ether functionalized mesoporous silica (SBA-15) adsorbent for selective recovery of gold (Au3+) ions from electronic waste leachate

The rapid production rate of electrical and electronic devices demands for gold (Au) recovery and recycling from their generated wastes. However, achieving adsorbents with high selectivity for Au remains a challenge. Herein, an Au3+-selective composite adsorbent (15TCE@SBA-15) was successfully fabricated through covalent attachment of thia-crown ether (15TCE) as ligand on mesoporous silica support SBA-15. The physicochemical properties of 15TCE@SBA-15 were extensively examined using FT-IR, SAXRD, TGA, FE-SEM, EDS mapping, surface area (BET), and pore size distribution (BJH, NLDFT) analysis. To evaluate its ability to selectively capture Au3+, adsorption experiments were conducted. The results revealed that 15TCE@SBA-15 was able to capture 126 mg of Au3+ per gram of sample. More importantly, it was highly selective towards Au3+ with distribution coefficient of K-D similar to 2439 L g(-1) vs. other cations (i.e. Pd2+, Pt4+, Ni2+, Pb2+, Cu2+, Zn2+) present in spent mobile phones with K-D values < 1.0. 15TCE@SBA-15 can concentrate Au3+ up to similar to 19,837 (CF x 10(-3)) times in contrast to other cations with CF x 10(-3) <= 3-1019. 15TCE@SBA-15 is stable with consistent performance in cycled adsorption/desorption runs. General results reveal the potential of 15TCE@SBA-15 for selective Au3+ recovery from secondary sources such as electronic waste leachates and other aqueous streams.