Facile fabrication of superhydrophobic magnetic bio-waste for oil spill cleanup

In this study, we have demonstrated a facile method to convert corncob, an abundant and low-cost bio-waste, into a superhydrophobic magnetic bio-sorbent with potential application in oil spill remediation. We immobilized CoFe2O4 nanoparticles on the surface of corncob using the co-precipitation method to magnetize the surface of the bio-waste. Additionally, we applied silica and octadecylamine (ODA) coatings to create a rough and low surface energy sorbent material, respectively, which significantly improved its oil sorption capacity. The fabricated magnetic composite exhibited excellent magnetic responsivity (saturation magnetization: 32 emu/g), superhydrophobicity (water contact angle: 165˚), and superoleophilicity (oil contact angle: 0˚). The modified corncob (MCC) powder was easily separated using a magnetic field and showed oil sorption capacity 22.13, 13.33, 57.65, and 44.17 times its original weight for crude oils with API 23.5° and 29.7°, fresh and used motor oil, respectively. The fabricated bio-sorbent could be recovered and reused in oil-water separation at least 10 times, with a water contact angle and sorption capacity of 158.5˚ and 42 g/g, respectively, after 10 cycles. Furthermore, it displayed remarkable durability in corrosive media. We compared the performance of MCC powder with three different bio-wastes, including coconut husk, acorn, and rice husk, and found that MCC powder and coconut husk showed preferable performance over the others. Overall, our study provides a facile and efficient method for converting corncob and other bio-wastes into a superhydrophobic magnetic bio-sorbent for oil spill cleanup.