Frequent oil spill accidents and industrial wastewater discharge result in severe health and ecological problems to human beings. Generally, industrial wastewater contains not only various kinds of oils, but also water-soluble dyes and heavy metal ions. Elimination of these contaminants in the process of oil/water separation is very important in industrial applications and still remains unsolved. Even though some membranes with underwater superoleophobicity have been extensively used toward oil-in-water emulsion separation, the bulk of them lack the capacity of removing the water-soluble pollutants from water during oil/water separation. Herein, a novel loess-coated polyvinylidene fluoride (PVDF) membrane was successfully fabricated through depositing the loess and sodium alginate suspension onto a PVDF membrane with a vacuum pump. The loess-coated PVDF membrane displayed extraordinary underwater superoleophobicity with oil contact angles larger than 150° and sliding angles smaller than 10° toward different oils, including crude oil with high viscosity. Besides, the loess-coated PVDF membrane can separate various oil-in-water emulsions with separation efficiencies up to 99.6% and flux as high as 910.4 L m⁻² h⁻¹ bar⁻¹. Moreover, the coated membrane retained excellent separation performances even after 10 cycles. In addition, the coated membrane showed outstanding resistance to corrosive liquids, and could separate oil-in-water emulsions in corrosive solutions effectively. Furthermore, the as-prepared membrane displayed outstanding mechanical performance and flexibility. More importantly, the loess-coated PVDF membrane exhibited effective adsorption toward dyes and heavy metal ions. This cost-efficient, environmentally friendly and multifunctional loess-coated PVDF membrane not only allows natural loess resources to be used rationally, but also effectively solves the problems of water pollution.

Crude oil spill accidents that have been occurring frequently not only have been seriously destroying the marine ecological environment and threatening human health for a long time, but also generating a great loss of precious resources. Therefore, the treatment of crude oil wastewater, especially under corrosive conditions, is one of the most urgent problems. However, to the best of our knowledge, the effective separation of surfactant-stabilized micro-nanoscale crude oil-in-water emulsions under corrosive conditions has been rarely reported. Herein, waste bricks are employed to effectively separate the surfactant-stabilized micro-nanoscale crude oil-in-water emulsions under corrosive conditions, which not only enables the removal of crude oil, but also reduces environmental pollution. The suspensions of waste brick powders (WBP) and sodium alginate were coated onto a polyvinylidene fluoride (PVDF) membrane via a vacuum filtration approach to prepare a WBP-coated membrane. The as-prepared WBP-coated membrane exhibited excellent underwater superoleophobicity under corrosive conditions and low adhesion to crude oil. Besides, the WBP-coated membrane can separate crude oil-in-water emulsions with a separation efficiency of up to 99.8% and a permeating flux as high as 623 L m⁻² h⁻¹. More significantly, the as-prepared WBP-coated membrane can successfully separate crude oil-in-water emulsions under corrosive aqueous conditions (1 M HCl, 1 M NaOH and 3.5 wt% NaCl solution) with a separation efficiency of above 99.5% and a permeating flux of up to 934 L m⁻² h⁻¹. The WBP-coated membrane not only removes crude oil from oily wastewater, but also enables the recycling of waste resources.