Heterogeneous Fenton degradation of bisphenol A by carbon nanotube-supported Fe3O4

In this study heterogeneous Fenton oxidation using Fe3O4 amended onto multi-walled carbon nanotube (Fe3O4/MWCNT) showed effective degradation of aqueous bisphenol A (BPA). The Fe3O4/MWCNT exhibited an octahedron crystal structure of Fe3O4 (100–150 nm) which was well-dispersed onto the MWCNT with little agglomeration. The Fe3O4/MWCNT catalyst-driven Fenton oxidation achieved high removal of BPA (97% removal in 6 h) at the selected operating conditions (pH of 3, 0.5 g catalyst/L, [H2O2]:[BPA] of 4 (mol/mol), 50 °C). The Fenton oxidation of BPA demonstrated similar removal of BPA at 0.5–1 g catalyst/L while showing significant removal of BPA at the initial pH of 3. The [H2O2]:[BPA] of 4 in this study was found to be the cost-effective condition to achieve high removal of BPA at low concentration of H2O2. Besides, the intermediates and oxidation products produced by the Fenton oxidation of BPA at the [H2O2]:[BPA] of 4 did not show any biological toxicity. The [H2O2]:[BPA] ratio of 4 was much lower than that for other heterogeneous Fenton of BPA (54 mol H2O2/mol BPA) and comparable to those for homogeneous Fenton of BPA (2–9 mol H2O2/mol BPA). The Fenton oxidation rate of BPA using the catalyst was enhanced by the factor of 3.5 as the reaction temperature increased from 20 °C to 50 °C. The five cycles of the Fenton oxidation using the same catalyst resulted in the steady removal of BPA confirming high stability of the Fe3O4/MWCNT catalyst over the multiple Fenton reactions. The scavenging tests of the hydroxyl radicals suggested that the hydroxyl radical-driven oxidation was the major step among the multiple reactions in the heterogeneous Fenton oxidation. The findings from this study suggest that the Fenton oxidation using Fe3O4/MWCNT would highly efficient solution for the removal of bisphenol A from water.