| abstract |
【Task】 Scale components can be removed selectively and sufficiently, effectively preventing the generation of scale when raw water such as seawater is desalinated by evaporation, and can obtain fresh water stably with high recovery rate. Supply composite nanofiltration membranes. [Solution] By a polycondensation reaction between a 0.2 to 2.0 wt% piperazine aqueous solution containing no base other than piperazine and a 0.10 to 0.30 wt% trimesic acid chloride solution dissolved in an organic solvent immiscible with water. Supplying salt water adjusted to a temperature of 25 ° C., a pH of 6.5, and a NaCl concentration of 500 mg / L at an operating pressure of 0.35 MPa in a composite nanofiltration membrane comprising a polyamide-based skin layer to be formed and a porous support for supporting the same When the membrane filtration treatment was carried out by supplying NaCl removal rate at a temperature of 25 ° C., pH 6.5, and salt water adjusted to a MgSO 4 concentration of 1500 mg / L at an operating pressure of 0.35 MPa. The composite nanofiltration membrane in which the ratio of MgSO 4 to the MgSO 4 removal rate, that is, [MgSO 4 removal rate (%)] / [NaCl removal rate (%)] shows a removal performance of 2 or more. [Selection figure] None |