Fe/polymer-based photocatalyst synthesized by sono-sorption method applied to wastewater treatment

Abstract

The present work focused on the photo-Fenton performance using Fe+2 immobilized on chitosan and alginate spheres for degrading methylene blue dye (MB) and a real effluent (RE) from a pulp and paper mill industry. With the aim of optimizing iron sorption onto these matrices, the time sorption was evaluated in the presence of ultrasound (sono-sorption) and in its absence (conventional method). SEM/EDS, XRD and thermogravimetric analysis (TGA) were used to characterize the catalyst prepared. The results showed no morphological change on the spheres, regardless of the iron sorption method employed; however, the ultrasound bath drastically decreases the synthesis time from several hours to a few minutes (15 min), comparing to the conventional method. Response surface methodology and Box-Behnken design were used to evaluate the effects of the pH, the mass of Fe photocatalyst and H2O2 concentration. 98.8 % removal of the MB occurred at pH = 3, 2 g of catalytic spheres, 300 mg/L of H2O2, after 6 min of photo-Fenton treatment. The pseudo-first-order kinetic model of Langmuir-Hinshelwood exhibited a good fit. The industrial wastewater from the pulp and paper mill presented, after 20 min, 96 % discoloration and, 100 % of DBO, 86 % of DQO and 52 % turbidity reduction. The stability of chitosan beads with iron immobilized by ultrasound (Fe/C/US) was confirmed over six cycles. The color removal of the pulp and paper mill wastewater remained higher than 86 % even after the sixth cycle.