Chapter 11. Applications of Engineered Nanomaterials in the Recovery of Metals from Wastewater

The occurrences of certain metal and metalloid (hereafter metal) ions in municipal and industrial wastewater are major concerns due to the adverse effects such metals can have on human health and the environment at relatively low concentrations. Given the fact that all metals are attained from finite deposits, their recovery from wastewater is essential in order to prevent loss of materials from the global supply loop. An intrinsic challenge, however, is that economically valuable metal ions are often present at relatively low concentrations and in highly complex chemical matrices and thus conventional extraction methods are often not economically or practically feasible. The use of engineered nanomaterials could overcome this issue due to their unique properties, including high specific surface area, colloidal behaviour and quantum size effects. This chapter will discuss the wide potential of engineered nanomaterials for the recovery of metal ions from wastewater, including their use as suspended colloids and as fixed bed reactors. Significant technical challenges remain, however, associated with (1) their synthesis cost and (2) the ecotoxicity of ‘unbound’ engineered nanomaterials, which if overcome, could give rise to the widespread adoption of engineered nanomaterials in the recovery of metals from wastewater.