Promoting aqueous and transport characteristics of highly reactive nanoscale zero valent iron via different layered hydroxide coatings

Abstract

In this study, nanoscale zero valent iron (Fe0) was coated with different layered hydroxide coatings (Mg/Al/Ca(OH)N) to enhance its suspension stability in aqueous solution and transportability within the porous media. Morphological characteristics, crystallinity and surface elemental composition of the synthesized bare (Fe0) and coated (C-Fe0) were investigated using TEM, XRD and SEM-EDS analyses respectively. Suspension stability of Fe0 and C-Fe0 suspensions with different [Mg or Al or Ca/Fe: 0.2–1.0 wt/wt] coating ratios was investigated through several sets of 180 min settlement experiments. Moreover, packed-column experiments were conducted to evaluate the mobility of the prepared materials through porous media. Settlement results were highly consistent with mobility investigation, where C-Fe0 [Mg/Fe]1.0 showed the best performance in both with around 88% relative suspension efficiency and 93% penetration efficiency (5 times higher than Fe0). A reciprocal relation was found between particle size, crystallinity and reactivity of the C-Fe0, where the finest sizes exhibited higher crystallinity and better removal of the two targeted nutrients. Furthermore, the progressive dissolution of the Mg(OH)2 shell compared with the other coating materials resulted in its superior prolonged reactivity. The presented C-Fe0 could be promising towards enhanced performance of the reactive nanoparticles in the real water treatment applications.