Fe/C micro electrolysis and Fenton oxidation process for the removal of recalcitrant colored pollutants from mid-stage pulping effluent

The pulp and paper industry produces a large amount of colored effluent in the pulping, bleaching, and papermaking processes. The wastewater from the pulp washing and bleaching stages is also known as mid-stage pulping effluent, which is difficult to treat due to its toxicity and dark dolor. This paper reports a novel Fe/C micro-electrolysis process for the treatment of the mid-stage pulping effluent. Results show that this process is effective in removing the color under optimal reaction conditions. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) analyses indicate that the colored pollutants were removed from the wastewater in the Fe/C microelectrolysis by adsorption, collection and filtration mechanisms. The Fe²⁺ ions produced in the micro-electrolysis process functioned as Fenton's reagents with H₂O₂ in the follow-up oxidation stage, which enhanced the removal of chemical oxygen demand (COD) and color.