Pilot-scale treatment of p-Nitrophenol wastewater by microwave-enhanced Fenton oxidation process: Effects of system parameters and kinetics study

A pilot-scale microwave-Fenton (MW-Fenton) process in a continuous flow microwave irradiation system was studied by the degradation of p-Nitrophenol (p-NP) in wastewater. The results showed that the amount of hydroxyl radicals (OH center dot) in MW-Fenton process was 2.8 times higher than that in conventional Fenton process at 7 min. The maximum p-NP removal efficiency (93.2%) was measured at pH 3.3 when n(H2O2)/n(p-NP) was 13.9, n(H2O2)/n(Fe(II)) was 81.6 and the hydraulic detention time was 12 min by mixing p-NP and H2O2 solution firstly, and then adding Fe(II) solution. The energy efficiency in the pilot-scale process was estimated to be 75.5%, superior to our previous lab-scale treatment result (less than 70%). The process obeyed the pseudo first-order kinetics by assuming a constant concentration of OH center dot. The apparent activation energy of p-NP degradation, calculated by Arrhenius equation, was 44.89 kJ mol(-1). The range of intrinsic reaction rate constants of p-NP degradation under optimal conditions in the continuous flow MW irradiation system was from 1.09 x 10(8) L mol(-1) s(-1) to 2.63 x 10(8) L mol(-1) s(-1). The pilot-scale study prompts the potential industrial application of MW-Fenton oxidation process in rapid and effective removal of refractory toxic organic pollutants from wastewater. (C) 2013 Elsevier B.V. All rights reserved.