Reductive sequestration of chromate by hierarchical FeS@Fe0 particles

Abstract

Nanoscale Fe(0) (nFe(0)) can detoxify Cr(VI)-bearing wastewater and groundwater, but rapid passivation is a negative factor for large-scale remediation applications. In this study, a magnetic FeS@Fe(0) hybrid material was fabricated by immobilization of iron sulfide (FeS) onto Fe(0) particles to improve the Cr(VI) removal capacity. The solid characterization confirmed that Fe(0) particles were encapsulated by amorphous iron monosulfide. The Cr(VI) uptake by FeS@Fe(0) hybrid particles was found to follow pseudo-second-order rate kinetics, and the Langmuir isotherm was most appropriate to describe Cr(VI) sorption. Meanwhile, the FeS@Fe(0) hybrid particles showed a much higher efficiency towards Cr(VI) sequestration compared to individual nFe(0). Moreover, the results of batch experiments with various adsorbent doses indicated that the reactivity of FeS@Fe(0) varies with different FeS-to-Fe(0) molar ratios. The reaction rate constants for Cr(VI) removal first increased with an increasing FeS-to-Fe(0) ratio from 0/1 to 1/9, and then decreased for the FeS-to-Fe(0) ratio increased further 1/5 or 1/3. For environmental parameters, there was a negative effect of increasing the solution pH and dissolved oxygen on Cr(VI) removal. Furthermore, a mechanistic analysis revealed that Cr(VI) reduction occurred predominantly at the solid-liquid interface, and that Fe(II) regenerated from FeS@Fe(0) corrosion may account for 52% of the Cr(VI) reduction, while electrons from Fe(0) and FeS account for the rest. After treatment, Cr(VI) was completely transformed and immobilized as solid Fe-Cr hydroxide precipitates, thus avoiding secondary contamination. The FeS@Fe(0) hybrid material has a better potential for treating Cr(VI)-bearing wastewater than nano Fe(0).

Pyrite enhanced the reactivity of zero‐valent iron for reductive removal of dyes

“…For this purpose, 1,10-phenanthroline was added into the reaction system of Orange II with the ZVI/pyrite mixtures. 40,41 The results shown in Fig. 5 indicate that the addition of 1,10-phenanthroline significantly decreased the removal efficiency of Orange II by the ZVI/pyrite mixtures, which implies that the adsorbed iron(II) participated in the reduction of Orange II, because 1,10-phenanthroline has a strong complexation ability to ferrous ions and can exclude their contribution to the reduction of pollutants.…”

“…Hence, the contribution of adsorbed iron(II) to dye removal is worthy of further investigations. For this purpose, 1,10‐phenanthroline was added into the reaction system of Orange II with the ZVI/pyrite mixtures . The results shown in Fig.…”

Insight into pH dependent Cr(VI) removal with magnetic Fe3S4

“…For example, it was found that Cr(VI) reductive efficiency induced by ZVI was much higher than that of ferrous ions and sulfite, which may be caused by the multiple electron donators such as ZVI, the structure and dissolved ferrous ions [20]. Moreover, due to its excellent affinity of heavy metals, iron minerals can easily adsorb the generated Cr(III) species to realize the total Cr immobilization on its surface [21,22]. However, ZVI is easily oxidized at ambient conditions to form a oxidative layer on ZVI surface, which may block its further oxidation by Cr(VI) [23].…”

Synergistic degradation of PNP via coupling H2O2 with persulfate catalyzed by nano zero valent iron

“…The nano-scaled zero valent iron (nZVI) particles were fabricated by reducing FeSO 4 $7H 2 O with NaBH under nitrogen protection based on our previous report. 17…”