Alcohothermal synthesis of sulfidated zero-valent iron for enhanced Cr(Ⅵ)removal

Sulfidation of zero-valent iron(ZVI)has attracted broad attention in recent years for improving the sequestration of contaminants from water.However,sulfidated ZVI(S-ZVI)is mostly synthesized in the aqueous phase,which usually causes the formation of a thick iron oxide layer on the ZVI surface and hinders the efficient electron transfer to the contaminants.In this study,an alcohothermal strategy was employed for S-ZVI synthesis by the one-step reaction of iron powder with elemental sulfur.It is found that ferrous sulfide(FeS)with high purity and fine crystallization was formed on the ZVI surface,which is extremely favorable for electron transfer.Cr(Ⅵ)removal experiments confirm that the rate constant of SZVI synthesized by the alcohothermal method was 267.1-and 5.4-fold higher than those of un-sulfidated ZVI and aqueous-phase synthesized S-ZVI,respectively.Systematic characterizations proved that Cr(Ⅵ)was reduced and co-precipitated on S-ZVI in the form of a Fe(Ⅲ)/Cr(Ⅲ)/Cr(Ⅵ)composite,suggesting its environmental benignancy.

Remediation of arsenic contaminated soil by sulfidated zero-valent iron

In this study,the influences of sulfidation on zero-valent iron(ZVI)performance toward As(Ⅴ)immobilization in soil were systemically investigated.It was found that,compared to unamended ZVI,sulfidated ZVI(S-ZVI)is more favorable to immobilize As(Ⅴ)in soil and promote the conversion of water soluble As to less mobile Fe-Mn bound As.Specifically,under the optimal S/Fe molar ratio of 0.05,almost all of the leached As could be sequestrated by>0.5 wt.%S-ZVI within 3 h.Although the presence of HA could decrease the desorption of As from soil,HA inhibited the reactivity of S-ZVI to a greater extent.Column experiments further proved the feasibility of applying S-ZVI on soil As(Ⅴ)immobilization.More importantly,to achieve a good As retention performance,S-ZVI should be fully mixed with soil or located on the downstream side of As migration.The test simulating the flooding conditions in rice culture revealed there was also a good long-term stability of soil As(Ⅴ)after S-ZVI remediation,where only 0.7%of As was desorbed after 30 days of incubation.Magnetic separation was employed to separate the immobilized As(Ⅴ)from soil after S-ZVI amendment,where the separation efficiency was found to be dependent of the iron dosage,liquid to soil ratio,and reaction time.Toxicity characteristic leaching procedure(TCLP)tests revealed that the leachability of As from soil was significantly reduced after the S-ZVI amendment and magnetic separation treatment.All these findings provided some insights into the remediation of As(Ⅴ)-polluted soil by ZVI.