Chapter 5 - Adsorptive and reductive removal of toxic and radioactive metal ions by nanoscale zero-valent iron–based nanomaterials from wastewater

Abstract

Nanoscale zero-valent iron (nZVI) is a widely applied nanomaterial in the removal of toxic and radioactive metal ions from groundwater and industrial wastewater. The advancement of nZVI (i.e., small size, large surface area, environmental friendliness, and high reactivity) has made it feasible to separate many toxic metal ions from wastewater while fulfilling its large-scale application. In this chapter, we aim to describe the progress thus far with a view to providing a comprehensive summary of toxic and radioactive metal ion removal using nZVI-based materials. Several synthetic and modification techniques are introduced for pristine nZVI and nZVI-based nanomaterials. Furthermore, we overview the major adsorptive and reductive factors influencing the application of nZVI to toxic and radioactive metal ions, such as nZVI intrinsic characteristics (e.g., surface area, surface passivation, and metallic iron core), different target species (e.g., U(VI), Tc(VII), Se(IV)/Se(VI), Cr(VI), As(III)/As(V), Hg(II), Cu(II), and Ni(II)), and various operating conditions (e.g., pH, coexisting anions and cations, reaction time, temperature, and natural organic matter), and the potential mechanisms involved. The interaction mechanism between respective contaminants and nZVI-based nanomaterials with advanced spectroscopic techniques and the DFT theoretical calculation model are discussed. Moreover, the toxicity and risks of nZVI-based nanomaterial application are also examined. These efforts and attempts can broaden the development of nZVI-based nanomaterials for large-scale water treatment.