Aliquat-336-impregnated alginate capsule as a green sorbent for selective recovery of gold from metal mixtures

A novel green sorbent Aliquat-336-impregnated alginate capsule (AIAC), was manufactured by dropping mixture of Aliquat-336, carboxymethyl cellulose and CaCl₂ into the sodium alginate solution. Four types of capsules were prepared with different Aliquat-336 concentrations (0M, 0.1M, 0.2M, and 0.3M). Among the prepared capsules, AIAC with 0.2M Aliquat-336 exhibited the best Au(III) selectivity. The study of pH edge revealed that pH 1 was the best condition for selective adsorption of Au(III). In the ternary mixture of Au(III), Pt(IV) and Pd(II), the developed sorbent showed the maximum Au(III) uptake of 191.92±10.13mg/g, which was about 10 times higher than those of Pt(IV) and Pd(II). Sorption-desorption cycles revealed that the sorbent could be regenerated without significant loss of sorption capacity and selectivity. XPS analysis proposed two step mechanism of gold uptake: first selective binding of Au(III) followed by subsequent reduction of Au(III) to Au(0). Finally, through designs of sorption-desorption processes, high-purity gold solutions of 97.06% and 98.49% were obtained from the low and high concentrations of the ternary metal mixtures, respectively.