Synergetic magnetic field and loaded Fe3O4 for simultaneous efficient acetate production and Cr(VI) removal in microbial electrosynthesis systems

It is of great interest to explore effective approaches to overcome the stress of heavy metals and achieve simultaneous enhanced acetate production and heavy metal removal in the biocathodes of microbial electrosynthesis (MES) systems. Herein, the magnetic field and the loaded Fe3O4 were employed to synergetically improve both acetate production and Cr(VI) removal in the Serratia marcescens Q1 catalyzed cathode of MES. This was accomplished via increase in the circuital current and the S. marcescens release of different amounts and components of extracellular polymeric substances dominantly harboring of outer membrane c-type cytochromes, reaching 2.6 ± 0.1 mg/L/h (acetate production) and 2.3 ± 0.1 mg/L/h (Cr(VI) removal) at a circuital current of 1.4 ± 0.0 A/m2. These values were 4.2-fold (acetate production), 1.3-time (Cr(VI) removal) and 2.2-fold (circuital current) of those in the absence of magnetic field and Fe3O4. Increasing initial Cr(VI) from 60 mg/L to 120 mg/L similarly achieved more acetate production (3.3–4.2 folds) and higher circuital current (2.1–2.2 folds) than those at a Cr(VI) of 60 mg/L in the absence of magnetic field and Fe3O4, confirming the positive influential magnetic field and loaded Fe3O4 for efficient system performance at these high levels of Cr(VI). This study provides an alternative and environmentally benign approach for achieving simultaneous efficient acetate production and Cr(VI) removal, opening up the feasibility of sustainable treatment of heavy metals-contaminated organics-barren waters and wastewaters.