The separation of oil–water mixtures in highly acidic, alkaline, and salty environment remains a great challenge. Simple, low-cost, efficient, eco-friendly, and easily scale-up processes for the fabrication of novel materials to effective oil–water separation in highly acidic, alkaline, and salty environment, are urgently desired. Here, a facile approach is reported for the fabrication of stable hydrogel-coated filter paper which not only can separate oil–water mixture in highly acidic, alkaline, and salty environment, but also separate surfactant-stabilized emulsion. The hydrogel-coated filter paper is fabricated by smartly crosslinking filter paper with hydrophilic polyvinyl alcohol through a simple aldol condensation reaction with glutaraldehyde as a crosslinker. The resultant multiple crosslinked networks enable the hydrogel-coated filter paper to tolerate high acid, alkali, and salt up to 8 m H₂SO₄, 10 m NaOH, and saturated NaCl. It is shown that the hydrogel-coated filter paper can separate oil–water mixtures in highly acidic, alkaline, and salty environment and oil-in-water emulsion environment, with high separation efficiency (>99%).

A magnetically recoverable and efficient demulsifier is shown to demulsify surfactant-stable water-in-oil emulsions rapidly. Ferroferric oxide (Fe₃O₄) particles are firstly coated by amorphous silicon dioxide (SiO₂), and further functionalized with a commercial dodecyltrimethoxysilane solution (KH-1231). Owing to their paramagnetic properties, the demulsifier particles can be easily recovered with a magnet. Upon addition of demulsifier to emulsions and subsequent sonification, the supernatant becomes completely transparent and no droplets are observed in the micrographs. It was also demonstrated that this demulsifier is effective for emulsions prepared with a variety of oils. Moreover, magnetically recovered demulsifier can be recycled after simple treatment without any decline of efficiency. This work presents a feasible approach for demulsifying water-in-oil emulsions, and has potential value in industry.

A superhydrophilic and underwater superoleophobic Cu(OH)₂-covered mesh with micro- and nanoscale hierarchical composite structures is successfully fabricated through a one-step chemical oxidation of a smooth-copper mesh. Such mesh, without any further modification, can selectively separate water from oil/water mixtures with high separation efficiency, and possess excellent stability even after 60 uses. This method provides a simple, low-cost, and scalable strategy for the purification of oily wastewater.

An intelligent photo-responsive spiropyran (SP)-contained surface that combines reversible wettability conversion with photochromic behavior was prepared on etched silicon substrates by atom transfer radical polymerization. The heterocyclic ring cleavage of SP moieties under UV irradiation leads to the change of the surface wettability and color. Water contact angle (CA) of the prepared surfaces change from 138.8° ± 1.3° to 42.7° ± 1.7° after 5 min under 365 nm UV irradiation and recover to its original state after 20 min of visible light irradiation, accompanied by the color change between yellowish and purple. To our knowledge, this result is the highest and fastest CA variation reported for surfaces containing SPs. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Fluoropolymer transparent thin films were deposited on different substrates by one-step vacuum evaporation method, which exhibit superhydrophobic property with water contact angle (CA) greater than 150°. Polytetrafluoroethylene (PTFE) film with network structure shows high oleophobicity with oil CA of 138°, whereas polytetrafluoroethylene-perfluoropropylvinylethers (PFA) film with particle structure is superoleophilicity with oil CA near 0°. It is believed that different conformation of CF₂ groups at the surface lead to this different surface activity. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011