Effect of the Mineral Structure of Magnetite Synthesized from Hematite on the Heterogeneous Fenton Process of Crude-oil Waste Degradation

Abstract

Crude oil spills frequently occur during transportation on land and sea, leading to significant soil and groundwater pollution. Crude oil recalcitrant compounds persist in the environment, bioaccumulate through the food chains, and pose a risk of causing adverse effects to human health. This study aims to analyse catalytic effect of the mineral phase of magnetite synthesized from hematite applied to the heterogeneous Fenton process and degradation of crude oil residues. In this study, magnetite was synthesized by hematite iron ore reduction at temperatures ranging from 650 to 800 K using biochar from waste deposits. The conversion rates were 7%, 34%, 69%, and 78%. The mineralogical analysis of each sample was carried out with the X-Ray Diffraction method (XRD). After the brief characterization of synthesized products and crude oil, experiments have been carried out to investigate the effect of the mineral structure of synthesized products on the crude-oil mineralization. The heterogeneous Fenton oxidation process, when conducted at room temperature, achieves successful reductions in residual TOC levels by 37.6%, 58.6%, 76.6 and 80.8% with an H₂O₂/Fe3O4 molar ratio of 10 and at a pH of 6.5 for a crude oil TOC concentration of 1 g/L, compared to a decrease of 53%, 66%, 66.5%, and 74.2% at a pH of 3.2. Chromatographic analysis using the synthesized product with 78% of magnetite after magnetic separation shows that the degradation rate of alkanes with carbon atoms greater than 15 is low. Although samples rich in hematite have shown good stability, an improvement in recovery and reusability was observed as the magnetite content increased.