Selective Recovery of Au(III) from Binary Metal Solution Using Aliquat-336-Impregnated Alginate Capsule

Aliquat-336-impregnated alginate capsule (Aliquat-336-AC) was fabricated using a facile method. Ionic liquid Aliquat-336 was used as a model extractant owing to its good extraction performance toward precious metals (PMs). Aliquat-336-AC was prepared by dropping the mixture solution (Aliquat-336 + Tween 80 + CaCl2) into the alginate solution. CaCl2was used to form Ca-alginate shell, leading to Aliquat-336-AC. Two types of binary metal solutions, Au (III)/Pt (IV) and Au (III)/Pd (II) were used to evaluate metal sorption capacity of Aliquat-336-AC. The maximum Au (III) uptake in Au (III)/Pt (IV) and Au (III)/Pd (II) systems were 61.38 and 82.97 mg/g, respectively. Whereas, the uptakes of Pt (IV) and Pd (II) were almost closed to zero, indicating excellent Au (III) selectivity of Aliquat-336-AC. A comparative study was carried out between liquid/liquid extraction (LLE) using Aliquat-336 and solid/liquid adsorption (SLA) using Aliquat-336-AC for Au (III) selective recovery from Au (III)/Pt (IV) and Au (III)/Pd (II) solutions. The data of selectivity coefficients (αsel) showed that the values of αAu/Ptand αAu/Pdwere 10253.34 and 5817.61 in the SLA system, respectively. These values were much higher than 2033.38 of αAu/Ptand 1879.80 of αAu/Pdin the LLE system. Therefore, Aliquat-336-AC can be used as a selective adsorbent for Au (III).