Facile recovery of gold from e-waste by integrating chlorate leaching and selective adsorption using chitosan-based bioadsorbent.

• A facile process combining a single-step gold leaching and adsorption was proposed. • Novel chlorate reagent showed ∼100 % leaching efficiency of gold from e-waste. • Chitosan-based beads showed selective separation of gold from the chlorate leachate. • Gold with 97.8 % purity was obtained from pyrolysis of gold-adsorbed chitosan beads. • The entire process is simple, safe, and inexpensive for gold recovery from e-waste. Recovery of gold from electronic wastes, particularly waste printed circuit boards (WPCBs), has received significant attention due to its high gold content and economic value. This study reports a novel method for efficient and selective recovery of gold from WPCBs using an integrated chlorate leaching and chitosan-based bioadsorption. The experimental conditions of the leaching step were optimized, and ∼100 % leaching efficiency of gold could be achieved when 0.5 g of WPCB sample was treated with 12.5 mL (liquid to solid ratio of 25) of a mixture of chlorate (0.2 M) and chitosan (1% w/v) in 2 M HCl at 55 °C for 5 h. The WPCB leachate containing gold and other metal ions (e.g. Cu and Al) was diluted three-fold and then treated with glutaraldehyde-crosslinked chitosan (GCC) beads, achieving selective and complete adsorption of gold at GCC dose of ≥1 g/L. The adsorbed gold on GCC could be fully desorbed by using a thiourea/HCl mixture (each 0.2 M). The high efficiency of gold adsorption-desorption could be maintained up to four successive cycles, signifying long-term reusability of the GCC. As an alternative approach, thermal decomposition of the gold-adsorbed GCC at 650 °C was shown to generate sponge-like gold residue with 97.8 % purity. These results indicated high efficiency of the proposed method for recovering gold from e-waste along with its simple process steps, low chemical usage and low cost. [ABSTRACT FROM AUTHOR]