Oil/water separation has become a worldwide challenge due to large volumes of industrial oily wastewater and frequent oil spill accidents, which constitute an enormous threat to human and biological safety. Herein, a superhydrophilic and underwater superoleophobic composite membrane was fabricated using the vacuum-assisted filtration technique of assembly of chitosan (CS) and titanium dioxide (TiO₂) on a cellulose acetate membrane for emulsified oil separation. The hydrophilic chitosan–TiO₂ (CST) composite and nanoscale hierarchical structure are beneficial for forming a water layer that can repel the infiltration of oil droplets into the membrane. The modified membrane demonstrated an excellent flux up to 6002.5 L m⁻² h⁻¹ for hexadecane-in-water emulsion, which is one order of magnitude higher than traditional filtration membranes. Furthermore, the separation efficiency for all of the emulsified oils is above 97%, indicating superior oil/water separation performance. Most importantly, the modified membrane can maintain underwater superoleophobicity even in corrosive aqueous media, including strongly acidic, strongly alkaline, and highly saline solutions. It is expected that the chitosan–TiO₂ composite membrane can be potentially useful in treating oily wastewater from industry and daily life.

By utilizing the synergistic effect of chitosan (CS), magnetite (Fe₃O₄) particles, and graphene oxide (GO), a series of efficient and eco-friendly chitosan/magnetite-graphene oxide (CS/MGO) composites were fabricated through a facile chemical route. First, Fe₃O₄ particles were chemically deposited on the surface of GO to fabricate MGO hybrid. Then, chitosan was attached on MGO sheets, assembling to CS/MGO composites. According to the results of characterization, the covalent Fe-O-C bonds, electrostatic attraction, and hydrogen bonding between GO, Fe₃O₄, and chitosan ensure excellent structural stability and physico-chemical properties. The adsorption of Cr(VI) onto CS/MGO composites was also carried out under various conditions (content of CS, pH, initial concentration, contact time, and temperature). The CS/MGO composites possess high removal capacity for Cr(VI) from aqueous solution. Moreover, results also suggested that the CS/MGO composites had a strong reducing action for Cr(VI). When adsorption occurred, Cr(VI) and Cr(III) were simultaneously removed by CS/MGO composites. In addition, CS/MGO composites could retain good Cr(VI) removal efficiency after reuse over five cycles. CS/MGO composites are expected to have potential applications as easily regenerative bioadsorbents for Cr(VI) polluted water cleanup.

The influence of different coupling agents and coupling times on the wettability of a polyurethane (PU) sponge surface were optimized. Octadecyltrichlorosilane (OTS) was selected as the optimal coupling agent to prepare the superhydrophobic sponge. The superhydrophobic sponge was prepared in one step, which has the advantages of simple operation and enhanced durability. The superhydrophobic sponge was characterized by scanning electron microscopy, Teclis Tracker tensiometry, and Fourier transform infrared (FT-IR) spectrophotometry. The water contact angle increased from 64.1° to 151.3°, exhibiting ideal superhydrophobicity. Oils and organic solvents with different viscosities and densities can be rapidly and selectively absorbed by superhydrophobic sponges, with an absorption capacity of 14.99 to 86.53 times the weight of the sponge itself, without absorbing any water. Since temperature affects the viscosity and ionic strength of oil, and influences the surface wettability of the sponges, the effect of temperature and ionic strength on the oil absorption capacity of the superhydrophobic sponges was measured, and its mechanism was elucidated. The results showed that the absorptive capacity retained more than 90% of the initial absorptive capacity after repeated use for 10 times. Low-cost, durable superhydrophobic sponges show great potential for large-scale oil-water separation.