Aqueous toxic metal removal with functionalized magnetic nanoparticles

Aqueous sequestration of dissolved toxic metal species has been a strategic target for scientific research since the development of quantitative methods of detection. Traditional technologies mainly include reductions and adsorption with zero-valent metals and their oxides. Adsorption-based platforms are incapable of selection bias, unable to differentiate between similar oxidation states, and are difficult to separate and recycle. Magnetic nanoparticles have been the focus of multidisciplinary research efforts for the removal of aqueous toxic metals since they can be magnetically separated from the treated water. This makes the toxic metals easier to isolate and allows for regeneration of the nanoparticles, reducing cost and resource consumption. Smaller magnetic nanoparticles above specific temperatures are superparamagnetic which broadens their applicability. Adsorption is enhanced by the increased surface to volume ratio compared to bulk materials and ease of isolation under applied magnetic fields. Surface functionalization with various organic and inorganic compounds capable of preferential interactions with specific metals and metalloids improves the selection bias and enhances the utility of the filtration technology. This chapter will focus on the basic chemistry of magnetic iron oxides and highlight functionalization techniques, including the use of organosilanes, designed to remove specific metals and metalloid ions from aqueous solutions through covalent bonding (chemisorption). Current functionalization platforms including the use of organosilanes will also be examined.