Electrochemical oxidation of thallium (I) in groundwater by employing single-chamber microbial fuel cells as renewable power sources

An aerated electrochemical reactor (AER) employing single-chamber microbial fuel cells (MFCs) as renewable power sources is proposed for Tl(I) removal in groundwater. 80.5% of Tl(I) is oxidized to Tl(III) after 4 h electrolysis with initial Tl(I) concentration of 5 mg L−1, pH of 2.0, and applied voltage of 600 mV. Comparison experiments indicate that Tl(I) oxidation is mainly attributed to indirect electrochemical oxidation by in situ generated H2O2. Carbon felt performs best as anode material, while lower initial Tl(I) concentration, pH and higher applied voltage promote Tl(I) removal efficiencies. Subsequent coagulation/precipitation realizes nearly complete removal of total Tl from groundwater. Besides as renewable power source, MFC can also remove residual total Tl in the exhausted solution from AER efficiently. Analysis of the generated precipitate further confirms that Tl(III) is the main oxidation state of Tl. This work proves that the AER driven by low bioelectricity from MFC is a cost-effective process with in situ produced advanced oxidants to remove T1(I) from groundwater satisfactorily.