Recycled magnetite as sustainable photo-catalyst for hydrogen peroxide and peroxydisulfate activation: insights into efficiency and mechanism of Picloram removal in water

Abstract

In this work, the activation oxidants like H2O2 and peroxydisulfate (S2O82-) was investigated in the presence of a recycled magnetite (rMG) obtained from Hymag’in company (France) both in the dark and under UVA light. The degradation of picloram (PIC) was used as model pollutant. The effects of oxidants (type and concentration), light and water matrix were assessed. Better efficiencies were observed in systems containing peroxydisufate (PDS) due to the better stability of sulfate radicals compared to hydroxyl radicals. In addition, iron leaching was observed in PDS-based systems, thus suggesting homogeneous Fenton reactions increased their efficiency compared to systems containing H2O2. The effect of light boosted the efficiency due to regeneration of Fe(II) by Fe(III) photolysis. The 0.2 g L-1 rMG can completely degrade PIC under UVA light and the presence of PDS after only 2 h reaction. In wastewaters effluents, rMG exhibited promising results with a removal of about 60% of PIC after 4 h, and it was significantly better than commercial magnetite. The present works highlights the feasibility of using wastes from iron industry to treat wastewater which is an added value for the circular economy of water.