Removal of PFOA in groundwater by Fe⁰ and MnO₂ nanoparticles under visible light

The main objective of this study was to find a cost-effective, efficient and environmentally-friendly solution to remove perfluorooctanic acid (PFOA) from groundwater by using Fe⁰ and MnO₂ nanoparticles. The selected method was expected to be applicable to the remediation of PFOA-contaminated groundwater. Phytotoxicity of the nanoparticle treatment was studied to demonstrate the safe application of the nanomaterials. Zero-valent Fe (100 mg L⁻¹) and MnO₂ (100 mg L⁻¹) nanoparticles, produced in our lab, were used to remove PFOA up to 10 mg L⁻¹. The test was conducted under visible light with or without addition of 0.88 mol L⁻¹ H₂O₂ in a pH range of 0.5–11.0 for a duration of 18 h. Using Fe nanoparticles, a higher percentage of PFOA was removed under extreme acidic environment of pH 0.5 than under the basic environment of pH 11.0, and a minimum removal rate was reached under the neutral environment. The Fe nanoparticles were more efficient than the MnO₂ nanoparticles at pH 0.5 with a removal rate of 69.7% and 89.7% without and with H₂O₂ addition, respectively. Phytotoxicity study showed that the treatment by Fe nanoparticles under mild pH reduced the phytotoxicity of groundwater-associated PFOA to Arabidopsis thaliana. The Fe nanoparticles did not show negative effect to A. thaliana under the experimental conditions used in this study.