Evolution of Organic Components and Heavy Metals in Ceramics from Oil Sludge

Oil sludge (OS) is annually discharged with more than 300 million tons in the petroleum industry and is hardly utilized due to its inert properties and harmful components. Reusing it as raw materials to prepare ceramic materials has become a potential green and large-scale method. In this paper, OS mixed with oil sludge pyrolysis residue (OSPR) and oil sludge incineration fly ash (OSIFA) was converted into ceramics, and during the sintering process, the evolution of organic components and heavy metals in the ceramics was studied using X-ray diffraction (XRD), SEM-EDS, TG-FTIR, gas chromatography-mass spectrometry (GC-MS), thermodynamic analysis, physical property measurements, and heavy metal leaching tests. The results showed that the increasing proportion of OS was beneficial to reducing the initial densification temperature of ceramics and widening the range of sintering. The organic components in the OS mainly existed in the form of large carbon chain alkanes and esters of organic substances, and at 200-400 °C, organics burned to become CO₂ and H₂O gas. Ba, as the main heavy metal element in the ceramics, remained stable in the form of BaSO₄ during the sintering process, and the insolubility of BaSO₄ and the densification structure of ceramics ensured good solidification of Ba within the ceramics. Samples with 60 wt % OS, 20 wt % OSPR, and 20 wt % OSIFA had the widest sintering temperature range of 60 °C and performed best at 1150 °C with water absorption of 0.4%, flexural strength of 37.22 MPa, and qualified leaching concentrations of Ba, Cr, Mn, and Zn. This study provides a further understanding of oil-based solid waste in ceramics to promote its application in practices.