Removal of Hg(ii) in aqueous solutions through physical and chemical adsorption principles

Adsorption has been the focus of research on the treatment of heavy metal mercury pollution since it is among the most toxic heavy metals in existence. The US EPA has set a mandatory discharge limit of 10 μg Hg L^-1 for wastewater and for drinking water a maximum accepted concentration of 1 μg Hg L^-1. Physical adsorption and chemical adsorption are the two major mechanisms of adsorption methods used for mercury removal in aqueous sources. The recent decades' research progress is reviewed to elaborate varieties of adsorption materials ranging from materials with large surface area for physical adsorption to metal oxides for chemical adsorption. Many examples are presented to illustrate the adsorption principles and clarify the relationship between the structure and performance of the adsorbents. The combination of physical adsorption and chemical adsorption gives rise to numbers of potential mercury removal composites. This review demonstrates the adsorption mechanism and the performance of varieties of adsorbents, which would provide a comprehensive understanding on the design and fabrication of new materials for the removal of heavy metal ions in water.