Colorimetric response and adsorption performance of functional granular polyacrylonitrile for Au(I) in thiosulfate solution

Abstract

The thiosulfate gold extraction technology represents a typical non-cyanide method, which poses challenges in achieving high efficiency and cost-effective gold recovery. The present study involved the synthesis of a colorimetrically responsive granular polyacrylonitrile material (PANG_bPEI-CS₂) capable of effectively adsorbing Au(I) in thiosulfate solution. The results show that PANG_bPEI-CS₂ exhibits a colorimetric response to Au(I) in thiosulfate solution, with the observed visual color transitioning from pale yellow hue to orange. This phenomenon can be attributed to the conjugation plane extension on PANG_bPEI-CS₂ during Au(I) adsorption, resulting in a redshift of the absorption spectrum towards the visible region. The adsorption of gold in thiosulfate solution by PANG_bPEI-CS₂ follows the Langmuir isotherm and pseudo-second-order kinetic models, with the maximum loading capacity of 60.502 mg·g⁻¹. The gold adsorption mechanism by PANG_bPEI-CS₂ involves ligand exchange, wherein gold forms a ring complex with the proximity or adjacency of S atoms on PANG_bPEI-CS₂. And the adsorption process is influenced by both the pH of the solution and the concentration of thiosulfate. The loaded gold on PANG_bPEI-CS₂ can be effectively desorbed with acid thiourea solution. This finding are instrumental in addressing the challenges associated with the recovery and rapid detection of gold in thiosulfate solution.