Arsenic (III) removal by mechanochemically sulfidated microscale zero valent iron under anoxic and oxic conditions

Alteration of birnessite reactivity in dynamic anoxic/oxic environments

“…Although the influence of phase transformation on the reactivity of birnessite has been already investigated (Lefkowitz and Elzinga, 2015;Wang et al, 2018a;Wang et al, 2019), very little knowledge exists about the impact of oxygen on the removal of organic compounds interacted with MnO2 surfaces. Furthermore, MnO2 may co-exist with dissolved Mn(II) and emerging contaminants in natural systems which may be subjected to alternation between anaerobic and oxic conditions, such as water-sediment interfaces, water table fluctuations, groundwater recharge (Jeong et al, 2010;Wu et al, 2020;Zhao et al, 2021). However, little is known about the potential changes in the surface reactivity of MnO2 in environmental settings under alternating redox conditions.…”

Iron Powders as a Potential Material for Arsenic Removal in Aqueous Systems

“…136) Similar study on usage of mechanochemically sulfidated micro scale IP benefitting arsenic (As (V)) removal in oxic and anoxic conditions via enhanced iron corrosion, formation of As 4 S 4 and FeAsS precipitates is reported by Zhao and team. 155) IP combined with KMnO4 and Fe + 2 ions achieving higher removal of arsenite compared to pristine IP is also observed. 141) In another study, addition of CuSO 4 to IP, enhanced the corrosion rate of IP due to formation of Fe-Cu galvanic system, thus improving rate of arsenic removal.…”

Simultaneous Sequestration of Humic Acid-Complexed Pb(II), Zn(II), Cd(II), and As(V) by Sulfidated Zero-Valent Iron: Performance and Stability of Sequestration Products

“…Likewise, for HA-complexed Pb­(II), the lag time before its rapid disappearance was shortened from 35 to 12 min with the S/Fe molar ratio increasing from 0.01 to 0.12, but higher values of the S/Fe molar ratio resulted in an extended lag phase (Figure e). This decrease in S-ZVI reactivity at higher S/Fe molar ratios should be due to excess FeS x species that could block or mask the surface pores, resulting in reduced SSA and inefficient mass transfer. , …”

“…This decrease in S-ZVI reactivity at higher S/Fe molar ratios should be due to excess FeS x species that could block or mask the surface pores, resulting in reduced SSA and inefficient mass transfer. 25,33 Figure 1f shows the k obs of HM removal by S-ZVI at stage II. Generally, the rate constants for the tested HMs at stage II are 4−7 folds higher than those at stage I.…”

“…Recently, by incorporating sulfur into ZVI and thus constructing an iron sulfide (FeS x ) shell on the ZVI surface, sulfidation pretreatment was proposed as an alternative approach to enhancing the performance of ZVI and has gained increasing interest since its inception. − As a semiconductor, FeS x has higher electron conductivity than that of iron oxides, which can thus facilitate electron transfer and ZVI corrosion under oxic conditions. ,, Besides the improved ZVI reactivity, the presence of reduced sulfur species (e.g., S 2– ) in sulfidated ZVI (S-ZVI) was also found to be able to provide an additional metal sequestration route by forming insoluble metal sulfide precipitates . Thus, all these benefits make S-ZVI a promising candidate for remediation of HMs. − …”