A thermoresponsive Poly(N-isopropylacrylamide) (PNIPAAm)-modified nylon membrane was fabricated via hydrothermal route. Combining rough structure, proper pore size, and thermoresponsive wettability, the membrane can separate at least 16 types of stabilized oil-in-water and water-in-oil emulsions at different temperatures. Below the LCST (ca. 25 °C), the material exhibits hydrophilicity and underwater superoleophobicity, which can be used for the separation of various kinds of oil-in-water emulsions. Above the LCST (ca. 45 °C), the membrane shows the opposite property with high hydrophobicity and superoleophilicity, and it can then separate stabilized water-in-oil emulsions. The material exhibits excellent recyclability and high separation efficiency for various kinds of emulsions and the hydrothermal method is facile and low-cost. The membrane shows good potential in real situations such as on-demand oil-spill cleanup, industrial wastewater treatment, remote operation of oil/water emulsion separation units, and fuel purification.

We have successfully fabricated sandwich structural Ag3PO4 nanoparticle/polydopamine/Al2O3 porous small balls (APPAOs) by a facile homogeneous precipitation method, which exhibit a natural light catalysis capacity to degrade different kinds of water pollutants including industrial dyes and agricultural pesticides. The porous Al2O3 provides the substrate to form the Ag3PO4/Al2O3 heterojunction, as well as increases the specific surface area (SSA) of the Ag3PO4 nanoparticle, thus greatly enhancing the photocatalytic capacity. Polydopamine (PDA) plays the role of adhesive between Al2O3 substrate and Ag3PO4 nanoparticle, aiming to stabilize the synthesized APPAO catalyst. A part of Ag3PO4 is reduced by PDA and transformed into a Ag nanosphere, which further increases SSA and enhances the catalytic ability of the material by the plasmonic effect. Further study shows that there is a dynamic process between catalysis and adsorption/desorption equilibrium; i.e., with the catalysis going ahead, the adsorption/desorption equilibrium accordingly shifts thus thoroughly treating the pollutants. In addition, the superhydrophilic surface provides the APPAO with an excellent antioil property, which greatly reduces secondary pollution, and the small ball structure makes the material easy to use and recycle. Because of its excellent reusability, mild catalytic conditions, and ease of use, the APPAO has great potential to be used in the field of low-cost practical wastewater treatment.

Current special wetting materials designed for use with oily wastewater are usually classified as either the oil-removing type or the waterremoving type, which are unifunctional and limited by the oil density. Inspired by the integrated Janus system of the lotus leaf as well as the mussel-like mollusks adhered to the lotus, we fabricated a Janus polydopamine (PDA)−polyethylene terephthalate/ polytetrafluoroethylene (PET/PTFE) membrane by simple immersion and tapepeeling. This membrane shows a lotuslike Janus wettability, self-cleaning effect, and floating property. Furthermore, the Janus membrane can separate light oil (ρ oil < ρ water )/water mixtures with the superhydrophilic side facing upward, while heavy oil (ρ oil > ρ water )/water mixtures are separated with the hydrophobic side facing upward. The separation efficiency is outstanding even after 10 repeats (>99.10%). By aid of drainage of acetone, the separation process has avoided the use of external pressure. Moreover, integrated separations of oil-in-water and water-in-oil emulsions were achieved with high efficiency. This simply prepared PDA−PET/PTFE Janus membrane has realized an integrated separation system, overcoming the monotony of traditional special wettability separation membrane and extending the bionics field into oily wastewater treatment.

The decontamination of various pollutants including oils, organic dyes, and surfactants from water is an unprecedented issue throughout the world. A facile filtration process for in situ multifunctional water purification by employing a low-cost and easy-made catechol-polyethylenimine (PEI) nanocomposite deposited membrane has been designed. In combination with the intrinsic hydrophilicity of amino-rich groups, the resultant membrane possesses superhydrophilicity and underwater superoleophobicity, which is simultaneously advantageous for capturing anionic pollutants due to the electrostatic interaction. Such membrane can be successfully used for sundry surfactant-stabilized oil-in-water emulsions separation and pH-controllable removal of water-soluble dyes and the remaining surfactants at the same time. The excellent characteristics, i.e., fabrication protocol that is easy to scale up, better alkaline resistance, selectively controllable removal ability of anionic dyes, and surfactants with unaltered adsorption performance over 30 consecutive adsorption-desorption-washing cycles, will facilitate its versatility and practicability in environmental remediation and wastewater purification.

A PANI–SiNP-decorated Janus membrane was fabricated for highly efficient stabilized oil-in-water and water-in-oil emulsion separation, meeting industrial purification standards.