Effect of Staphylococcus epidermidis on U(VI) sequestration by Al-goethite

Area of Science:

• Environmental Science
• Geochemistry
• Microbiology

Background:

• Uranium (U(VI)) contamination poses environmental risks.
• Understanding U(VI) sequestration by mineral-bacteria systems is crucial for remediation.
• Al-goethite is a common soil mineral involved in metal adsorption.

Purpose of the Study:

• To investigate the effect of Staphylococcus epidermidis on U(VI) sequestration by Al-goethite.
• To elucidate the mechanisms governing U(VI) adsorption and transformation in mineral-bacteria systems.
• To assess the influence of environmental conditions (pH, carbonate) on U(VI) fate.

Main Methods:

• Batch experiments were conducted under varying geological conditions.
• Langmuir equation was used to calculate maximum adsorption capacities.
• X-ray Photoelectron Spectroscopy (XPS) and Fourier-Transform Infrared (FT-IR) spectroscopy were employed for surface analysis.

Main Results:

• S. epidermidis significantly enhanced U(VI) adsorption rates at pH < 9.0, increasing maximum adsorption capacity from 13.16 to 47.86 mg/g at pH 4.0 and 310 K.
• Adsorption decreased at high carbonate and pH due to electrostatic repulsion.
• XPS analysis indicated U(VI) reduction to U(IV) by S. epidermidis, with complexation affecting Fe(III) reduction at high pH.

Conclusions:

• S. epidermidis plays a significant role in enhancing U(VI) sequestration by Al-goethite, particularly under favorable pH conditions.
• Environmental factors like high pH and carbonate concentrations can alter U(VI) fate and transport.
• The interaction involves surface complexation and potential redox transformations, impacting U(VI) mobility in near-surface environments.