Phase evolution matters: How Fe(II) reshapes coprecipitate surfaces for enhanced U(VI) adsorption
Chaofei Zhang1, Yuan Chen2, Huiyang Mei3
1Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China; Key Laboratory of Petroleum Resources Exploration and Evaluation, Gansu Province, Lanzhou 730000, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Water Research
|March 22, 2026
Summary
Uranium (U(VI)) immobilization on iron (oxyhydr)oxides depends on iron ratios. Low Fe(II) density limits reductive immobilization, favoring adsorption pathways for uranium sequestration.
Area of Science:
- Environmental Science
- Geochemistry
- Materials Science
Background:
- Iron (oxyhydr)oxides are key for uranium sequestration.
- Uranium (VI) immobilization by Fe(II)/Fe(III) co-precipitates at moderate ratios needs clarification.
Purpose of the Study:
- Investigate phase evolution during Fe(II)/Fe(III) co-precipitation.
- Elucidate U(VI) immobilization mechanisms by these co-precipitates.
Main Methods:
- X-ray diffraction (XRD) and transmission electron microscopy (TEM) for phase analysis.
- Acid dissolution experiments to assess Fe(II) incorporation.
- Density functional theory (DFT) and spectroscopic analysis for reaction mechanisms.
Main Results:
- Low Fe(II)/Fe(III) ratio (1:50) maintained ferrihydrite phase; high ratio (1:10) transformed to goethite.
- Fe(II) incorporated into precipitate bulk, enhancing goethite surface reactivity for accelerated U(VI) immobilization.
- A reductive inert threshold for structural Fe(II) was identified between Fe(II)/Fe(III) ratios of 1:10 and 1:2.
Conclusions:
- Uranium immobilization is adsorption-dominated at low Fe(II) density, with limited reduction.
- Fe(II) speciation and availability critically influence uranium reduction.
- Findings provide a basis for predicting environmental uranium behavior.
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