Iron-loaded carbon nanotube-microfibrous composite for catalytic wet peroxide oxidation of m-cresol in a fixed bed...

A kind of novel iron-loaded carbon nanotube-microfibrous composite (Fe₂O₃-CNT-MF) catalyst is prepared and tested for fixed bed m-cresol catalytic wet peroxide oxidation (CWPO) reaction. Results show that the Fe₂O₃-CNT-MF can significantly decline the pressure drop of the fixed bed. Higher temperature, lower feed flow rate, higher catalyst bed height, and higher H₂O₂ dosage are beneficial to m-cresol degradation. Lower pH can also improve m-cresol degradation, but it will cause severe iron leaching. The highest m-cresol removal (over 99.5%) and total organic carbon (TOC) removal (53.6%) can be observed under condition of 2 cm bed height, flow rate of 2 mL/min, reaction temperature of 70 °C, 6 g/L H₂O₂, and initial pH = 1. Meanwhile, the Fe₂O₃-CNT-MF catalyst shows good stability with less than 10% decrease in m-cresol conversion and 7% decrease in TOC conversion after 24-h reaction and less than 2 mg/L iron leaching is observed in all conditions except for strong acid condition. Two probable pathways of m-cresol degradation process are presented. Under most conditions, m-cresol will first be turned into methylhydroquinone, followed by oxidation to p-toluquinone. In basic condition, some m-cresol will first be changed into 4-methylpyrocatechol. These aromatic intermediates will then be oxidized into some small molecular acids and finally be mineralized to CO₂ and H₂O.