To efficiently and synchronously separate oil/water mixture and adsorbed dyes, corn-cob-covered quartz sand (CCQS) filter media with underwater superoleophobic qualities and underoil extremely hydrophobic qualities were fabricated by grafting a corn cob onto the surface of quartz sand using the dip-coating technique. Due to the introduction of more hydrogen bonds on the quartz surface and the construction of a rough structure, the underwater oil contact angles and underoil water contact angles of the CCQS were 150.3~154.6° and 132.2°~154.6°, respectively. A separator for oil/water separation was devised, and the CCQS-filled separator could synchronously separate the oil/water mixture and adsorb malachite green. The separation efficiency of the oil/water mixture was over 99.93%, the removal rate of MG was 99.73%, and the adsorption capacity was 7.28 mg/g. The CCQS could keep its wettability steady under challenging environmental circumstances. Therefore, the study offered a novel concept for the successful oil/water mixture separation, while synchronously adsorbing dye.