Integration of Biodegradation and Nano-Oxidation for Removal of PAHs from Aqueous Solution

Despite many reports being published on using biodegradation or Fenton-like oxidation to remove various containments, the integration of these two processes to improve the removal efficiency of contaminants is still a challenge. This study attempted to remove naphthalene and phenanthrene from aqueous solution using a sequential biodegradation and Fenton-like oxidation based on green synthesis of iron nanoparticles (Fe NPs). Results showed that after 96 h, 100% naphthalene was biodegraded, whereas only 28.9% phenanthrene and 48.3% chemical oxygen demand (COD) were removed, respectively, indicating that the biodegradation was an incomplete process and the degraded metabolites still existed. To improve the removal efficiency of phenanthrene and the degraded metabolites, Fenton-like oxidation based on Fe NPs synthesized using tea extracts under various atmospheres (N-2, O-2 and air) was employed. Results indicated 100% of phenanthrene was removed, total COD removed increased to 81.5%, 77.2% and 68.7% using N-2, O-2 and air Fe NPs, respectively. In addition, Fe NPs were confirmed by scanning electron microscopy (SEM) and X-ray energy-dispersive spectroscopy (EDS). Finally, the degraded metabolites were identified by GC-MS to understand the degradation pathway.