Engineering stable thallium immobilization through synergistic microbial-mineral partnership in Fe-doped biogenic manganese oxides.

Thallium (Tl), an extremely toxic heavy metal, poses severe threats to water security due to the high mobility and toxicity of its monovalent form (Tl(I)). While biogenic manganese oxides (BMOs) show promise for Tl remediation, their practical application is hindered by structural instability and performance limitations. This study develops a breakthrough strategy through iron-doped BMOs (Fe-BMOs) that establish a synergistic microbial-mineral partnership for enhanced Tl immobilization. By optimizing Fe(III) incorporation (0.2%) during the early exponential phase of Pseudomonas putida MnB1(a manganese oxidizing bacterium), we created a stable composite material that maintains structural integrity while achieving 94% Tl removal efficiency-a 39% enhancement over conventional BMOs. The system operates through multiple mechanisms: the Fe-doped matrix provides enhanced porosity, Mn(III) content, and oxygen vacancies for efficient Tl sequestration via oxidation, ion exchange, and complexation, while microbial activity maintains mineral stability through continuous Mn(II) re-oxidation. Crucially, the material demonstrates exceptional environmental adaptability, maintaining robust performance across pH variations (4-8), Tl concentrations (1-10 mg L-1), and different dosing regimes, with toxicity characteristic leaching procedure (TCLP) rates consistently below 1.73%. The time-dependent Tl incorporation into mineral lattices further ensures long-term stability. This work provides both a technically viable solution for Tl contamination control and a fundamental paradigm for designing effective microbial-mineral systems for environmental remediation.