Redução do impacto ambiental do efluente proveniente do pré-tratamento da produção de biodiesel: uma proposta híbrida de descontaminação via foto-eletro-Fenton/Fered/O3

Abstract

During biodiesel production, a complex wastewater is generated. This work proposes newly solution for the treatment of wastewater from enzymatic pretreatment of biodiesel production (WEPBP) by a hybrid system based on the photo-Fered-Fenton process with O3 assistance (PEF-Fered-O3). Response surface methodology (RSM) was applied to determine the suitable conditions for the PEF-Fered-O3 process: a current intensity of 3 A, an initial solution pH controlled at 6.40, an initial H2O2 concentration of 12,000 mg L-1, and an O3 concentration of 50 mg L-1. Three new experiments were performed under similar conditions with slight changes, a higher reaction time (120 min.), single or periodic H2O2 addition – small additions at different reaction times. It was observed that periodic H2O2 addition provided the best removal results, since the occurrence of undesired side reactions that cause •OH scavenging probably was minimized. With the application of the hybrid system, a COD and TOC decrease of 91% and 75%, respectively was achieved. The presence of metals such as Fe, Cu, and Ca, electric conductivity, and voltage at 5, 10, 15, 30, 45, 60, 90, and 120 minutes were studied. The X-ray diffraction (XRD) analysis was performed with sludge samples of raw and treated WEPBP samples to study the crystallinity degrees, evidencing that there was a rearrangement of the compounds present in WEPBP, possibly caused by the oxidation of the high fraction of organic matter. Genotoxicity and cytotoxicity tests with meristematic cells from roots of Allium cepa were performed, indicating an improvement of the toxicity levels, since the events of gene regulation and cell morphology were improved after the WEPBP treatment by the hybrid system. Facing the current scenario at biodiesel industries, the proposed new hybrid system, PEF-Fered-O3 at suitable conditions, presents an efficient alternative for the treatment of the complex matrix, WEPBP, may decreasing the negative impacts of the discharge of WEPBP in the environment, since the reduction of the potential to cause abnormalities in cells of living organisms was evidenced by genotoxicity and cytotoxicity tests.