Treatment of wastewater from the thermal desorption of oil-contaminated soil: performance and sorption mechanism of pyrolytic modified sawdust

Abstract

The green development of the petrochemical industry by using waste biomass for efficient and environmentally friendly oil/water separation is emerging in recent years. Herein, in view of the oily wastewater generated by thermal desorption (TD) for remediating oil-contaminated soil, the pyrolysis modification of waste biomass sawdust and its application to oil removal from thermal desorption wastewater (TDW) were conducted. The results showed that modified sawdust (MS) exhibited excellent hydrophobicity and high sorption capacity, showing abundant microporous structure (3.90 m² g⁻¹) and pore volume (0.02 cm³ g⁻¹). The oil removal rate increased from 60.3% of the raw sawdust to 97.3% of MS, and the oil/water selectivity coefficient (2.52) was 5.5 times higher than that before the modification (0.46). For the actual high oil content (1377 mg L⁻¹) of emulsion TDW, the MS layer showed high flux (4276.8 LMH) and considerable sorption performance, with turbidity, COD, and oil removal rates of 99.2%, 24.5%, and 83.3%, respectively. In addition, the MS layer showed excellent sustainability in multiple cycle feeding experiments (10 cycles per 200 mL) and the flux could be essentially restored merely by scraping off the surface MS. Furthermore, the treatment cost and risks of secondary pollution were reduced. This work proposed a new strategy of low cost, environment-friendly, and high-efficiency oil sorption, which is a promising method for the practical treatment of highly oily wastewater.