Review: adsorbents for the recovery of precious metals from wastewater

This paper presents an up-to-date overview of the various advanced materials as adsorbent used in the recovery of precious metals from wastewater. The precious metals concentrated here include gold, silver, palladium and platinum, whose recovery is interesting mainly due to their vast industrial applications and high market prices. Among various methods, adsorption approach is one of the most efficient techniques for the recovery of precious metal ions from aqueous solutions. There are a number of absorbents such as carbon materials, metal-organic frameworks (MOFs), biopolymers, silicas, resins, and transition-metal sulfides, which have been developed and explored to efficient recovery of precious metal ions from wastewater. Thermodynamics and kinetics were further discussed for exploring the adsorption mechanism of precious metal ions in these advanced materials. It was found that the adsorption process of these metals is mostly spontaneous (Delta G < 0) and endothermic (Delta H > 0) in nature. This review would contribute to the development of advanced materials for recovery of precious metals from secondary sources such as wastewater.