A research group led by Professor Hideto Matsuyama and Professor Tomohisa Yoshioka of Kobe University has succeeded in developing an oil-water separation membrane in which a hydrophilic silica ultrathin layer is formed on the surface of a polymer porous membrane.
Purification of oil-contaminated wastewater is extremely important in terms of securing water resources that are in short supply worldwide.With the conventional agglutination method and air levitation method, which are methods for treating oil-contaminated water, it is difficult to separate minute oil droplets with a diameter of 20 micrometers or less.On the other hand, the membrane separation method saves energy, but in the treatment of oil-contaminated water, oil droplets block the pores and the permeation of water decreases.Another problem is the deterioration of performance due to the adhesion of proteins to the membrane surface.Therefore, there has been a demand for the development of a highly functional separation membrane capable of efficiently and reliably separating ultrafine oil droplets and having high water permeability.
This time, the research group decided to react a silica source with a negative charge with a porous film that was positively charged by surface modification to form an ultrathin silica layer with a thickness of about 10 nanometers on the surface of the porous film. Successful.
The ultra-thin silica layer is hydrophilic and forms a thin layer of water on the film surface to repel oil and separate oil from wastewater to obtain clean water.In addition, it does not block the pores of the porous membrane, and the membrane can permeate water at extremely high speed only by gravity.It blocks more than 99.9% of oil droplets and can treat 1 liters (per square meter) of wastewater per hour.It can block even the smallest oil droplets of several tens of nanometers, and is effective for contaminated water caused by various types of oil.In addition, the oil droplets are less likely to adhere to the membrane, the oil droplets are easily peeled off by a simple washing, and the pores of the oil droplets are less likely to be blocked.Furthermore, it does not easily get dirty with surfactants and proteins.
The newly developed membrane can be applied to the removal of oil droplets of various sizes by controlling the pores of the base porous membrane.It is expected to be used for cleaning various oil-contaminated water such as industrial wastewater.
