silica iron (Fe@GN) represents a new family of silica-supported iron systems for water remediation. They exhibit superior adsorption capacities for As(v) removal and can be readily regenerated with high efficiencies of reuse, which is a key factor in their environmental benefits.
Effects of silica on iron Fischer-Tropsch catalysts
As a chemical promoter, silica inhibits reduction and carburization of iron and improves dispersion and stability of the active phase. It also strengthens H, C, and O adsorptions on the iron sites. It largely suppresses the formation of methane.
In aqueous systems, silica inhibits the hydrolysis of Fe(III) by replacing double-corner FeO6-octahedra in oxy-hydroxide polymers that are formed at the early stages of the process. The replacement by silica atoms in these complexes enables us to elucidate the atomic environment of Fe(III) during its hydrolysis in aqueous solutions.
Simultaneous deoxidation and oxidation in pure iron melts, in which dissolved silicon is present, results in the amorphous formation of iron oxy-hydroxide polymers containing double-corner FeO6-octahedra linked together by common edges. We have measured the strength of these silica inclusions produced by this type of deoxidation, characterized their micromechanical properties, and obtained fracture stress levels in the range from 8 to 17%.
The tensile strength of silica inclusions along their surfaces is predicted by finite element simulation to be on the order of 10 GPa, which is in the range of maximum values reported for dry silica fibers in vacuum or liquid nitrogen [39]. The presence within iron and its alloys of precipitated silica need not be deleterious, as we show here; this might be exploited to produce novel high-strength materials.