Size-Dependent Response of the Reductive Reactivity of Zerovalent Iron toward the Coexistence of Natural Organic Matter

Abstract

Although the existence of ubiquitous natural organic matter (NOM) exerts significant effects on the performance of zerovalent iron (ZVI), size-dependent response of the reactivity of ZVI toward NOM under both aerobic and anaerobic conditions has not been considered. In this study, the oxic removal and anoxic removal of the pollutant diatrizoate (DTA) by mechanochemically prepared ZVI of varying sizes in the presence of humic acid (HA), a typical NOM, were investigated comparatively. When oxygen was present, the effect of HA on DTA degradation transformed from promotion to inhibition as the particle size of ZVI decreased from microscale (mZVI) to nanoscale (nZVI). By contrast, in the absence of oxygen, HA always suppressed DTA removal regardless of ZVI size. Under aerobic conditions, HA complexed with Fe(III) (hydr)oxides and then detached from the mZVI surface, leading to the depassivation effect and promotion of atomic hydrogen (H*), while HA and HA−Fe(III) complexes coated the surface of nZVI with a relatively smaller size and suppressed the formation of H*. Under anaerobic conditions, adsorbed HA and associated HA−Fe(II) complexes covered the surfaces of mZVI and nZVI to different extents, resulting in the occupation of active sites and inhibiting generation of H*. This study provides an in-depth insight into the interaction between ZVI and NOM and may serve as theoretical guidance for the application of ZVI-based technologies.

Effect of natural organic matter (NOM) on the removal efficiency of Hg(ii) by MoS2: dependence on the Hg/MoS2 ratio and NOM properties

“…4d), 44 implying the formation of the Hg–NOM complexes through the complexation between Hg and –COOH and/or –OH groups on the NOM molecules. 45–47 Additionally, the particle size and ζ potential of MoS 2 remained unaffected by the addition of NOM with concentration up to 100 mg L −1 (Fig. S14†).…”

Catalytic dechlorination of 1,2-DCA in nano Cu0-borohydride system: effects of Cu0/Cun+ ratio, surface poisoning, and regeneration of Cu0 sites

“…For example, Cu/ZnO/Al 2 O 3 catalyst had retained 80% catalytic activity in the presence of 2% sulfur but Cu/Al 2 O 3 catalyst was completely deactivated with only 0.2% sulfur 35 , 64 . Chen et al 65 reported higher HA adsorption on nZVI than micro-ZVI surface which resulted in lesser H * formation on the nZVI and, thus, lesser contaminant degradation. Though extensive work has been published on the effects of groundwater constituents on various copper catalysts (mostly supported catalysts), no study has investigated their effects on the catalytic efficiency of nCu 0 synthesized by borohydride reduction method.…”

Interstitial Compound Fe3C-Doped Fe(0) Nanoparticles Embedded in Mesoporous Carbon Efficiently Boosting Cr(VI) Removal

“…NZVI, ferrous ions, and active H* are found to be the primary reductive species in the ZVI-based reduction process. , Therefore, it is necessary to examine their contribution to Cr­(VI) reduction in the Fe(0)/Fe 3 C@MesoC system. 1,10-Phenanthroline and tert -butyl alcohol were used as scavengers to quench the surface ferrous ions and H*, respectively. − As depicted in Figure c, the removal efficiency of Fe(0)/Fe 3 C@MesoC to Cr­(VI) dropped to 36% after adding 1,10-phenanthroline, while adding tert -butanol had little effect on Fe(0)/Fe 3 C@MesoC for the reduction of Cr­(VI), and Fe(0)/Fe 3 C@MesoC still retained a 92% removal efficiency.…”

“…NZVI, ferrous ions, and active H* are found to be the primary reductive species in the ZVI-based reduction process. 30,31 Therefore, it is necessary to examine their contribution to Cr(VI) reduction in the Fe(0)/ Fe 3 C@MesoC system. 1,10-Phenanthroline and tert-butyl alcohol were used as scavengers to quench the surface ferrous ions and H*, respectively.…”