Surface-Tuned Quartz Particles for Oil–Water Separation: SEM Characterization, Coating Effects, and Predictive Modelling

Oily wastewater is a critical environmental concern, and the high costs and fouling of conventional membranes drive the search for low-cost, efficient alternatives. This study evaluates surface-modified quartz particles for oil–water separation, focusing on hydrophilic and hydrophobic coatings. Quartz samples underwent washing, hydrophobic coating, and hydrophilic coating, with morphological and elemental changes assessed using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM–EDS). Oil and grease (O&G) content was determined via the EPA 1664 method under high-solids conditions. The untreated oil–water mixture contained 142,955.9 mg/L O&G. Hydrophilic-coated quartz achieved the greatest reduction, producing water with only 751.3 mg/L O&G, indicating excellent oil rejection and water selectivity. Washed quartz performed similarly at 837.1 mg/L. Hydrophobic-coated quartz, while yielding higher residual oil in water (64,198.9 mg/L), demonstrated strong oil affinity, making it more suitable for oil recovery applications. Raw quartz, tested without heavy oil loading, showed a baseline of 13.4 mg/L. These results confirm that surface engineering of quartz enables tunable separation properties, where hydrophilic surfaces favor water purification and hydrophobic surfaces enhance oil capture. The findings provide a pathway for scalable, cost-effective, and application-specific oily wastewater treatment solutions.