Photo-Fenton mineralization of synthetic municipal wastewater effluent containing acetaminophen in a pilot plant

The aim of this work was to study the mineralization of acetaminophen (ACTP) present in synthetic municipal wastewater effluent (S.E.) in a UV-A/C pilot plant using a homogeneous photo-Fenton oxidation process with continuous addition of H2O2 to the system.The mineralization process was found to follow pseudo-first-order kinetics. Experimental kinetic constants were fitted using neural networks (NNs). The mathematical model reproduced the experimental data to within a 90% confidence level. At the optimum conditions (H2O2 flow rate = 50 mL/h, [Fe(II)] = 2 ppm, pH = 2.5 and temperature = 40 °C), 71.5%, 82.1% and 94% of COT, COD and BDO-5 were removed in 120 min respectively.Determination of the hydrogen peroxide consumed and remaining in the water revealed that 5.8 mol of H2O2 were consumed per each mol of total organic carbon removed from solution. It was also confirmed that an excess of dissolved H2O2 is needed to achieve high mineralization rates, so continuous addition of peroxide is recommended for industrial application of this process.Comparison experiments of scavenger-loaded conditions proved that the reaction takes place mainly through a radical and single oxygen mechanism (96.7%).The molecular pathway (0.7%) and direct photolysis (2.6%) are secondary.

Research Highlights
► Photo-Fenton process is an alternative for the mineralization of S.E. with ACTP.
► Under optimum conditions, 83% of COD and 71% of TOC are removed in 120 min.
► 5.8 mol of H2O2 were consumed per mol of TOC removed.
► The reaction takes place mainly through a radical mechanism.