Removal of some selected micropollutants in aqueous solution by advanced oxidation processes: case of Levafix blue dye, Difenoconazole & Acibenzolar-S-Methyl fungicides

Abstract

Over the last decades, Human consumption leads to massive industrial sector manufacturing. A regular utilization of micropollutants (dyes, pesticides, pharmaceuticals, and personal care products…etc) that end up the aquatic environment present real threat and considered ecosystem perturbators. Advanced oxidation processes are progressively applied for persistent pollutants degradation instead the conventional methods that have been confirmed inefficient. This research focused on Fenton-based processes using various categories of irradiations source in different type of reactors combined with commercial and synthesized material, and it has been tested on removal of three selected micropollutants, a dye and two pesticides. The degradation of Levafix Blue dye was investigated using Fenton and Visible light photo-Fenton processes. Under acidic medium, it has been observed that both processes, Fenton and Photo-Fenton, were able to eliminate roughly 99% of pollutant. However, the increase of iron concentration leads to the inhibition of reaction. The photodegradation of difenoconazole fungicide was carried out via Photo-Fenton process using synthesized α-Fe2O3 nanoparticles. The α-Fe2O3 was prepared using hydrothermal approach. Average crystallite size has been recorded to be 27 nm and the surface area was found to be SBet 24.82 m2/g. DFL removal has been tested under diverse systems: UV photolysis, UV/H2O2, UV/α- Fe2O3, Fenton and Photo-Fenton process. The kinetic has been monitored using High-Performance Liquid Chromatography. As a result, it was demonstrated that Photo-Fenton process (UV/α- Fe2O3/ H2O2) as most effective for DFL removal. The optimal catalyst dose of α- Fe2O3 for high removal rate is about 0.5 g/l at initial solution pH. The mineralization efficiency attained 83.67%. A possible mechanism pathway was proposed based on detected intermediates using gas chromatography-mass spectrometry analysis. The last part of this work focused on comparative study between photo-Fenton and Sono-Fenton processes on degradation of fungicide Acibenzolar-S-Methyl. The investigation exhibited that ultrasound irradiation has accelerated the efficiency of Fenton process via increasing the hydroxyl radicals generation the removal rate achieved the complete degradation rate within 20 min compared to photo-Fenton, Fenton, photolysis, and sonolysis processes. An optimization of parameters was carried out. A transformation mechanism pathway of the sonochemical oxidation was suggested.