Elastic, super-hydrophobic and biodegradable chitosan sponges fabricated for oil/water separation

Due to easy availability and biodegradability, chitosan (CS)-based porous adsorbents have attracted significant interest in oil-spill and organic solvent removal. Herein, a multi-network CS-based sponge was fabricated via ion and hydrogen bond cross-linking using lemon, followed by covalent cross-linking via heptanal, in-situ loading of Fe3O4-polydopamine (PDA) particles and polylactic acid (PLA) coating. The as-fabricated sponge was systematically characterized by Fourier transform-infrared spectrometry (FT-IR), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), transmission electron microscope (TEM), static water contact angles (WCA) and so on. The as-fabricated CS-based sponge exhibits excellent elasticity, which could be compressed to large strains (80%) at a relatively high stress (0.685 MPa). The WCA of the targeted sponge can reach to 152.2 ± 1.2º after multiple surface functionalization. In addition, the degradation rate of the as-fabricated sponge can still reach 45.01 ± 1.11% within 15 days. Particularly, the sponge could selectively adsorb oil/organic solvent with up to 50 times of its own weight, and effectively separate the surfactant-stabilized oil-in-water emulsion with a flux of 8753 ± 423.56 L m−2 h−1. Last but not least, the sponge can be driven and recycled magnetically. In conclusion, this promising multifunctional sponge can be applied as a new absorbent for oil-water separation.