None of the existing water treatment films can be applied to the treatment of organic solvent because their polymers are vulnerable to acid, alkali, and heat. Ceramics and carbon film resistant to organic solvent are available, but neither of them can treat organic solvent at high speed. National Institute for MaterialsScience developed a filter that can filter organic solvent like oil and solventmedium. The filter has numerous holes, each of which is about 1 nanometer in diameter, and can treat organic solvent at about 1,000 times faster than the off-the-shelf filters for organic solvent. The newly developed filter is a 35-nanometer-thick diamond-like carbon film using porous alumina film as substrate, and it has numerous 1-nanometer diameter holes through which organic solvent runs.
The film has about one seventh of diamond in strength. It exhibited a permeability rate of 239 liters per hour and per bar for each square meter to filter depressurized hexane. It succeeded in eliminating more than 94% of impurities, though how much impurities can be eliminated depends on the molecular size. It has pressure resistance of up to 20 atmospheric pressures. The new film can be applied to the production of ultralow-sulfur diesel fuel (ULSD) and treatment of effluent created in the process to extract oil from oil sand. The research members plan to put the new film into practical use by replacing the porous alumina substrate with a carbon fiber sheet. The research results will be put on the January 27 issue of the American science magazine Science.