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

• Aliquat-336-impregnated alginate capsule (AIAC) was fabricated in a facile approach.
• AIAC showed selectivity toward Au(III) in ternary metal mixture solution.
• The maximum Au(III) uptake was 191.92 mg/g, which was about 10 times higher than those of Pt(IV) and Pd(II).
• High-purity gold solutions of 97.06% and 98.49% were separately obtained from the low and high metal concentrations.

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 (0 M, 0.1 M, 0.2 M, and 0.3 M). Among the prepared capsules, AIAC with 0.2 M 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 ± 10.13 mg/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.

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