Removal of polychlorinated biphenyls combining the synergy of bacteria and iron bionanoparticles prepared from agrowaste

Abstract This study presents an environmentally sustainable approach for synthesizing iron bionanoparticles using grape berries and grape pomace from two Vitis vinifera cultivars (Merlot and Blaufränkisch) highlighting the valorization of food industry waste within circular economy principles and the synergistic approach involving bacteria for environmental cleanup. The Merlot pomace-derived nanoparticles exhibited an amorphous structure, predominant Fe(III) species (Mössbauer spectroscopy), high specific surface area (398 m 2 ·g⁻ 1 ), and nanometric, porous morphology. Fe–O bond formation and polyphenol complexation was confirmed. Evolution of pH and redox potential values during synthesis revealed that slightly alkaline, near-physiological conditions favor nanoparticles formation and redox activity. All iron nanoparticle types were applied in removal experiments targeting polychlorinated biphenyls (from congener mixture Delor 103). The highest removal of the sum of PCBs congeners by nanoparticles alone reached 62% after 14 days using Merlot pomace-derived nanoparticles. When combined with the bacterium Ochrobactrum anthropi in a sequential synergistic approach, removal efficiency increased to 76%. Co-application with Stenotrophomonas maltophilia also resulted in high removal (70%). Ecotoxicological assessment revealed general non-toxicity of tested nanoparticles (derived from Merlot pomace) using Sinapis alba seed germination and Ochrobactrum anthropi auxanogram assays. However, higher concentrations (10 g·L −1 ) induced 46% inhibition of plant growth, likely due to restricted translocation of nutrients to the upper plant tissues. The results demonstrate the dual benefit of transforming agrowaste into effective, low-toxicity nanomaterials for remediation, supporting sustainable nanotechnology for environmental applications. Graphical abstract