pH-Controlled Tailoring of Multiscale Magnetite Structure for Enhanced H₂S Capture

Area of Science:

• Materials Science
• Environmental Chemistry
• Chemical Engineering

Background:

• Iron oxide adsorbents show promise for hydrogen sulfide (H2S) removal due to cost and environmental benefits.
• Precise control over microstructural features influencing H2S adsorption performance is not well understood.

Purpose of the Study:

• To investigate the relationship between microstructure and adsorption performance in Fe-based adsorbents.
• To elucidate the role of pH in controlling the synthesis of effective H2S adsorbents.

Main Methods:

• A pH-controlled hydrothermal synthesis strategy using ferrous sulfate heptahydrate.
• Characterization of adsorbent microstructure and surface properties.
• Fixed-bed adsorption tests for H2S removal at ambient temperature.

Main Results:

• A functional pH threshold of ≥7 was identified for pure-phase Fe3O4 formation and stabilization of the Fe2+/Fe3+ redox couple.
• Adsorbent synthesized at pH 13.0 exhibited enhanced basicity, mesoporosity, and {111} facets.
• Breakthrough capacity reached 85 mg/g, a 7-fold increase compared to pH 7, with a total sulfur uptake of 250 mg/g.

Conclusions:

• Multiscale microstructural features, including redox-active sites, defects, and surface basicity, critically govern H2S capture efficiency.
• The study provides a design strategy for tuning these features to optimize Fe-based adsorbents for H2S removal.