A novel solar-powered electrochemical mineralization system for persistent remediation of uranium-contaminated...

Reduction of the migratory ability of uranium via reduction, co-precipitation or immobilization is a widely used technology for remediation of uranium contaminated groundwater (UCG). However, the re-released uranium due to environmental alterations such as oxidation, acid dissolution, or microbial decomposition limits the long-term effect of UCG remediation. Here, we developed a novel solar-powered electrochemical mineralization (SPEM) system for persistent remediation of UCG under laboratory conditions. The SPEM system incorporates uranium into magnetite crystal to achieve long-term stability of uranium. The effects of photoelectric conversion, subsurface void fraction, groundwater seepage velocity, and electrode configuration on uranium removal were systematically analyzed. The results showed that the remediation system had excellent adaptability to complex water quality and geological conditions, and could remediate large-area contamination. After 12 h of persistent treatment, the system with newly hexagonal two-dimensional electrode configuration (1A6C) reduced uranium concentration by more than 85% in simulated subsurface environment. The mineralized uranium was not re-released within continuous rinsing of treated regions using an acid solution (pH = 3.0), for 370 h. The developed method solely requires metallic iron as a raw material, which has high and long-term efficiency, is eco-friendly, simple, and widely applicable, thus reliable for the remediation of deep UCG.