Recovery of gold using graphene oxide/calcium alginate hydrogel beads from a scrap solid state detector

Abstract

Hydrogel beads was developed for the selective removal of gold from a scrap solid state detector. Beads were synthesized by graphene oxide impregnation in calcium alginate matrix (Gra-Alg) using sol gel method. Scrap solid state detector was dissolved in aqua regia. Copper (Cu) from the solution was recovered using conventional chemical separation where as gold(Au) from the supernatant solution was selectively isolated using Gra-Alg hydrogel beads. The characteristic XRD peak of graphene oxide was observed at 2θ = 11°. The maximum uptake capacity of the hydrogel beads is observed as 81.87 mg g−1. The sorption capacity of the hydrogel beads is highly dependent on the pH of the solution and more than 95% uptake of Au was observed at pH range 2–4. The equilibrium contact time of the sorption of gold on the hydrogel beads was 22 h. Isotherm study suggests that the system is following the Langmuir isotherm model and the maximum sorption capacity (Q0) was observed as 81.87 mg g-1. The experimental data fitted well with the second order pseudo kinetic equation with linear correlation coefficient value as 0.94 and the rate constant is 0.001 g mg-1 min-1.