Treatment of motor oil-contaminated water via sorption onto natural organic lignocellulosic waste: thermodynamics, kinetics, isotherm, recycling, and reuse

Ipomoea batatas peel (IBP) is established as a viable lignocellulosic sorbent for wastewater treatment but has not been applied for the decontamination of oil-polluted water. This work reports for the first time the sorption of motor oil from water onto IBP as a natural eco-friendly sorbent. The FTIR spectra of IBP showed several functional groups desirable for efficient uptake of motor oil from water. SEM characterizations revealed an irregular and porous surface morphology, while EDX showed carbon (56.2%) and oxygen (39.0%) as major constituents of IBP sorbent. The BET surface area and pore characterizations of IBP revealed a surface of 5.774 m²/g, a pore volume of 0.00423 cm³/g, and an average pore diameter of 3.062 nm. The Langmuir model presented the best fit to the isotherm oil sorption analysis with a coefficient of determination (R²) of 0.9034 and a sum square error (SSE) of 0.0071. Kinetic modeling revealed that the process conformed to the intraparticle diffusion and pseudo-second-order model, while thermodynamics displayed a physical, endothermic, and feasible uptake of motor oil onto IBP. The oil sorption was found to be dominated by absorption mechanism and hydrophobic interactions. The motor oil-loaded IBP showed 96.2% oil desorption using petroleum ether as eluent. Besides, IBP exhibited efficient recycling and reuse for oil uptake with a decrease from 3.39 (initial uptake) to 2.82 g/g (fourth cycle). These investigations prove that IBP sorbent is a highly efficient biodegradable, eco-friendly, and reusable natural organic material for sequestration of motor oil from water.