Decoding the divalent cation effect on sulfidation of zero-valent iron: Phase evolution and FeS_x assembly

Area of Science:

• Environmental Science
• Materials Science
• Chemistry

Background:

• Sulfidated zero-valent iron (S-ZVI) enhances contaminant removal but traditional preparation methods hinder optimal iron sulfide assembly.
• Pickling processes for S-ZVI disrupt interfacial assembly, leading to imbalanced electron transfer and storage.

Purpose of the Study:

• To develop an improved method for preparing S-ZVI with enhanced decontamination capabilities.
• To investigate the role of divalent cations in regulating iron sulfide assembly and improving S-ZVI performance.

Main Methods:

• S-ZVI was synthesized using liquid-phase precipitation in solutions containing trace divalent cations.
• The phase evolution and interfacial assembly of iron sulfides (FeS_x) on the ZVI surface were analyzed.
• Cr(VI) removal efficiency was compared between S-ZVI prepared with and without divalent cations.

Main Results:

• S-ZVI prepared with trace divalent cations exhibited a 323.25-fold increase in Cr(VI) removal compared to bare ZVI.
• Divalent cations facilitated FeS_x chemical assembly by regulating surface protonation and phase evolution.
• Optimized assembly reduced electron storage consumption and proved effective in simulated groundwater.

Conclusions:

• Divalent cation regulation is crucial for ordered FeS_x assembly at the ZVI interface, enhancing S-ZVI performance.
• This approach offers a versatile and effective strategy for in-situ sulfidation and S-ZVI application in soil and groundwater remediation.