Improving oil absorption performance of cork via deep eutectic solvent treatment for environmental remediation

Oil pollution poses a serious threat to aquatic ecosystems and water quality, necessitating the development of efficient, selective, and reusable absorbent materials. In this study, cork was chemically modified using deep eutectic solvents (DES) synthesized from nonanoic acid combined with either choline chloride or betaine at a 1:4 molar ratio. To further enhance hydrophobicity, the DES-treated corks were subsequently coated with stearic acid. The successful chemical modification and structural changes were confirmed through comprehensive characterization using Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR), ultra-high resolution scanning electron microscope (UHR-SEM), and thermogravimetric analysis (TGA). The materials were then tested for their oil absorption capacity, reusability, and antibacterial properties. The comprehensive characterization confirmed successful chemical modification and structural changes in the cork material. The DES-treated corks exhibited improved antibacterial activity against Escherichia coli ATCC 25922, showing significant reductions of 23.2% (choline chloride-based) and 47.1% (betaine-based) compared to untreated cork. Absorption tests with engine oil and dichloromethane demonstrated that the betaine-nonanoic acid-treated cork achieved superior performance, with high absorption capacities of 13.92 g g^-1 and 28.15 g g^-1, respectively, and an oil-water separation efficiency of 80.14%. Furthermore, the material maintained high efficiency over 10 reuse cycles with minimal loss in capacity. These findings highlight the potential of DES-treated cork, particularly when coated with stearic acid, as a sustainable and high-performing sorbent for oil spill remediation.