Abstract
The treatment of oily wastewater and organic solvents in aquatic systems demands effective, low-cost, and scalable separation materials. In this work, hydrophobic coked sand was prepared from the pyrolysis of Munaily Mola oil-sand residues, which is a fluorine-free and waste-based method for oil-water separation. Pyrolysis created a conformal layer of amorphous carbon on the quartz particles, resulting in inherent micro- and nano-hierarchical roughness and decreased surface polarity without further chemical treatment. The material was thoroughly characterized by SEM, EDS, XRD, FTIR, Raman spectroscopy, XPS, BET analysis, and TGA analysis, which revealed the retention of the crystalline α-quartz phase, the presence of a stable carbonaceous layer, mesoporous structure, and high thermal stability. The coked sand had a water contact angle of about 140°, which slightly reduced to ∼129° after long-term cycling, reflecting durable hydrophobic properties. In the gravity-driven separation experiments with 1,2-dichloroethane/water mixtures, the coked sand delivered an initial flux of 3034 L m −2 h −1 and sustained an average separation efficiency of ∼96% over 30 cycles. Although the initial pore saturation resulted in a flux reduction, the system stabilized during subsequent cycling with maintained high selectivity. The robust carbon-silica hybrid framework facilitated sustained performance without fluorinated additives and complicated post-processing procedures. Because of its waste-based material origin, low cost of production, and mechanical and chemical robustness, the coked sand is a scalable granular filter medium for gravity-driven oil/water separation and environmental remediation.