Research on the characterization, reactivity, and transportability of porous silicon-coated nanoscale zero-valent iron

In practical conditions, the remediation efficiency is always very limited due to the rapid aggregation and deactivation of nanoscale zero-valent iron (nZVI). Porous SiO₂-coated technology can effectively suppress the agglomeration and oxidation of nZVI particle, resulting in the excellent dispersion and stability in water. A series of characterization results show that the porous SiO₂-coated Fe⁰ (Fe⁰@p-SiO₂) was a core-shell structure composite, with Fe⁰ as the core and the porous SiO₂ as the shell. Moreover, the prepared composite material has a large specific surface area (244.04 m²/g). The experiments of nitrobenzene (NB) reduction and one-dimensional simulation column indicated that the different amounts of NaOH in the preparation process lead to the different structures, shapes, and particle sizes of prepared composite materials, which have significant effects on its activity and transportability. Under the conditions investigated, the optimum ratio of Fe⁰@p-SiO₂ synthesis was n_Fe³⁺:n_{(Tetraethoxy silane, TEOS)}:n_NaOH = 1:1.85:1.19, and the corresponding reduction efficiency of NB to aniline (AN) and maximum normalized outflow concentration (C_max/C₀) was 100% and 0.79, respectively. The SiO₂-coated technology gives nZVI preparation greater control over the structure, shape, and particle size of modified nZVI composite, which has great potential in in situ remediation of groundwater contamination.