Reduction of the environmental impact of wastewater from the pretreatment of biodiesel production: A hybrid proposal for decontamination via photo-electro-Fenton/Fered/O 3

• Published in: Journal of environmental management Vol. 342; p. 118080
• Main Authors: Kreutz, Gustavo K, Borba, Fernando H, Baroni, Suzymeire, Mayer, Ildemar, Seibert, Daiana, Inticher, Jonas J, Zorzo, Camila F, Guimarães, Raíssa E
• Format: Journal Article
• Language: English
• Published: England 15.09.2023
• Subjects: Biofuels; Decontamination; Hydrogen Peroxide - chemistry; Oxidation-Reduction; Waste Disposal, Fluid - methods; Wastewater; Water Pollutants, Chemical - chemistry; Advanced wastewater treatment; Genotoxicity and cytotoxicity assays; Electrochemical oxidation

Complex wastewater is generated during biodiesel production. We propose a new solution for the treatment of wastewater from enzymatic pretreatment of biodiesel production (WEPBP) by using a hybrid system based on the photo-Fered-Fenton process with O assistance (PEF-Fered-O ). We applied response surface methodology (RSM) to determine the suitable conditions for the PEF-Fered-O process: a current intensity of 3 A, an initial solution pH controlled at 6.4, an initial H O concentration of 12,000 mg L , and an O concentration of 50 mg L . We performed three new experiments under similar conditions with slight changes to the conditions, namely a longer reaction time (120 min) and single or periodic H O addition (i.e., small H O additions at different reaction times). Periodic H O addition provided the best removal results probably by reducing the occurrence of undesired side reactions that cause hydroxyl radical ( OH) scavenging. With the application of the hybrid system, the chemical oxygen demand (COD) and total organic carbon (TOC) decreased by 91% and 75%, respectively. We also evaluated the presence of metals such as iron, copper, and calcium; electric conductivity; and voltage at 5, 10, 15, 30, 45, 60, 90, and 120 min. We submitted raw and treated WEPBP sludge samples to X-ray diffraction to study the degree of crystallinity. There was a rearrangement of the compounds present in treated WEPBP, possibly caused by oxidation of a large fraction of organic matter. Finally, we evaluated the genotoxicity and cytotoxicity of WEPBP by using Allium cepa meristematic root cells. Treated WEPBP was less toxic to these cells, denoted by improvements in gene regulation and cell morphology. Given the current scenario for the biodiesel industry, applying the proposed hybrid PEF-Fered-O system at suitable conditions provides an efficient alternative to treat a complex matrix, namely WEPBP, to reduce its potential to cause abnormalities in the cells of living organisms. Thus, the negative impacts of the discharge of WEPBP in the environment might be reduced.