Advances in hydrometallurgical approaches for gold recovery from E-waste: A comprehensive review and perspectives

•Gold recovery is challenging due to e-waste complexity and very low gold content.•Alternative methods for gold leaching require much effort to scale up applications.•Gold separation using smart bioadsorbents can simplify gold recovery.•Biomaterials from agricultural byproducts are promising for efficient gold separation.•An integrated approach for selective gold leaching and recovery was proposed. Increasing electronic waste (e-waste) generation is cause for great concern in the environment, for which our current society has developed various management policies, although it brings many economic opportunities through recycling and resource recovery activities. The recovery of gold from e-waste is of great importance for economic value and sustainability, as gold contained in e-waste can be manyfold that in primary gold deposits. Hydrometallurgy has succeeded in recovering gold from e-waste using different technical approaches owing to its mild operation, affordability, and low gas emission. However, it is still challenging to develop a complete technology for widespread application due to the complexity of e-waste and very low content of gold. Conventional leaching of gold may not satisfy environmental regulations, while alternative methods still require much effort to scale up their applications. Gold separation has attracted interest in the development of biomaterials for the effective, economical, and environmentally safe adsorption of gold. The phytochemical adsorption of gold has efficiently reduced gold ions to metallic gold, whereas gold-imprinted adsorbents have shown high selectivity toward gold species. The use of low-cost bio-adsorbents derived from agricultural by-products has been shown as a simple recovery option for gold by calcination. This review provides direction for future research toward selecting sustainable and efficient hydrometallurgical approaches for the recovery of gold from e-waste.