Preparation method of superhydrophilic/superhydrophobic composite nanofiltration membrane

The invention relates to a preparation method of a superhydrophilic/superhydrophobic composite nanofiltration membrane, belonging to the technical field of membrane separation. The preparation method comprises the following steps: putting a pretreated base membrane in a polycation electrolyte solution, washing with water, putting in a polyanion electrolyte solution, washing with water, and alternately assembling many times to form a predissociation layer; putting the membrane containing the predissociation layer in a soluble calcium salt polycation electrolyte solution, taking out, washing with water, putting in a soluble-silicate-containing polyanion electrolyte solution, taking out, washing with water, and repeating many times to obtain a polyelectrolyte/calcium silicate hydrate superhydrophilic composite nanofiltration membrane; and putting the superhydrophilic membrane in a fluorosilane ethanol water solution, immersing for 40-90 minutes, flushing with deionized water, and drying and solidifying in a drying oven. The superhydrophilic nanofiltration membrane can implement entrapping separation on the water-soluble dye molecules, and the superhydrophobic nanofiltration membrane can implement entrapping separation on organic solvent dye molecules.