Improving the Reactivity of Zerovalent Iron by Taking Advantage of Its Magnetic Memory: Implications for Arsenite Removal

Abstract

Premagnetization was employed to enhance the reactivity of zerovalent iron (ZVI) toward As(III) sequestration for the first time. Compared to the pristine ZVI (Pri-ZVI), the rate of As(III) elimination by the premagnetized ZVI (Mag-ZVI) was greater over the pHini range of 4.0-9.0 and increased progressively with increasing intensity of the magnetic field for premagnetization. Mag-ZVI could keep its reactivity for a long time and showed better performance than Pri-ZVI for As(III) removal from synthetic groundwater in column tests. The Fe K-edge XAFS analysis for As(III)-treated ZVI samples unraveled that premagnetization promoted the transformation of ZVI to iron (hydr)oxides and shifted the corrosion products from maghemite and magnetite to lepidocrocite, which favored the arsenic sequestration. The arsenic species analysis revealed that premagnetization facilitated the oxidation of As(III) to As(V). ZVI pretreated with grinding was very different from Mag-ZVI with regard to As(III) removal, indicating that the improved reactivity of Mag-ZVI should not be associated with the physical squeezing effect of the ZVI grains during magnetization. The positive correlation between the remanence of Mag-ZVI and the rate constants of total arsenic removal indicated that the enhanced reactivity of Mag-ZVI was mainly ascribed to its magnetic memory, i.e., the remanence kept by Mag-ZVI.

Direct Synthesis of Novel and Reactive Sulfide-modified Nano Iron through Nanoparticle Seeding for Improved Cadmium-Contaminated Water Treatment

“…FeSSi derived from system with 0.048 g SiO 2 dosage has the highest Mr among all of sulfide-modified nZVI. According to the literature 49 , high Mr favors pollutants removal by ZVI through faster iron corrosion.…”

An insight in magnetic field enhanced zero-valent iron/H2O2 Fenton-like systems: Critical role and evolution of the pristine iron oxides layer

“…1d ). It suggested that MF would not only improve mass transfer of the initial surface-bond reactions, but also lead to simultaneous variation on the surface properties of the pristine ZVI 19 39 .…”

“…Commercial iron powders are generally adopted in the ZVI/H 2 O 2 systems 6 12 15 17 . However, undesirable phenomena of initial lag reaction periods were observed, mainly attributing to existence of passive oxides films around the ZVI particles 12 18 19 . Occurrence of outer oxides filmscan be observed during the manufacture and storage procedures of commercial iron powders 1 17 18 19 .…”

“…However, undesirable phenomena of initial lag reaction periods were observed, mainly attributing to existence of passive oxides films around the ZVI particles 12 18 19 . Occurrence of outer oxides filmscan be observed during the manufacture and storage procedures of commercial iron powders 1 17 18 19 . It makes the ZVI particles atmospherically stable and block the electron transfer from inner Fe 0 to the surface 1 20 .…”

“…Recently, weak magnetic field (MF, <70 mT) was regarded as a promising cost-effective and environmental friendly tool to benefit the ZVI technologies 1 . It was reported that WMF not only significantly accelerated the removal of heavy metal ions (Se(IV), As(III)/As(V) and Cu(II)) by ZVI over a wide pH range 18 19 26 27 28 29 30 , but also improved the degradation of organic pollutants in Fe 0 /O 2 or Fe 0 /persulfate systems 29 30 . Based on a series of studies, Guan’s group concluded an enhancement role of weak MF in neutral ZVI systems 1 .…”