Polyamide (PA) nanofiltration (NF) membrane, and preparation method thereof by regeneration from scrapped microfiltration (MF) membrane

A preparation method of a polyamide (PA) nanofiltration (NF) membrane by a regeneration from a scrapped microfiltration (MF) membrane, comprising the following steps:

• 1) subjecting the scrapped MF membrane to a preliminary hydraulic cleaning for 10 min to 30 min to remove large mud cakes attached to a surface of the scrapped MF membrane to obtain a first cleaned MF membrane;
• 2) performing a deep cleaning on the first cleaned MF membrane by a chemical cleaning, wherein, the first cleaned MF membrane is placed in a cup-shaped reaction vessel and reacted with a solution A for a first reaction for 1 h to 3 h to obtain a second cleaned MF membrane;
• after the first reaction is completed, the solution A is poured out;
• and then the second cleaned MF membrane is reacted with a solution B for a second reaction for 1 h to 3 h to obtain a third cleaned MF membrane;
• 3) placing the third cleaned MF membrane cleaned in step 2) in a cylindrical reaction vessel, pouring a solution C into the cylindrical reaction vessel to obtain a resulting mixture, and subjecting the resulting mixture to a third reaction at 25° C. to 30° C. for 12 h to 36 h under a shaking to obtain a repaired MF membrane, wherein the solution C is a polydopamine (PDA) solution with a concentration of 1 g/L to 5 g/L, a solvent in the solution C is a mixture of an aqueous tris(hydroxymethyl)aminomethane (THAM) solution and an aqueous hydrochloric acid solution with a mass fraction of 36%, and THAM has a concentration of 0.5 g/L to 1.5 g/L in the aqueous THAM solution;
• and
• 4) at a porous side of the repaired MF membrane obtained in step 3), preparing an active layer by an interfacial polymerization, wherein preparation steps specifically include:
• dissolving imine monomer in water to obtain a solution D, soaking the repaired MF membrane in the solution D as a support layer for 1 min to 5 min and then taking out the repaired MF membrane to obtain a resulting composite, and removing excess liquid droplets on a surface of the resulting composite with a rubber roller;
• soaking the resulting composite in a solution E for the interfacial polymerization for 30 s to 90 s to obtain a membrane product;
• and finally drying the membrane product in an oven at 60° C. to 80° C. for 1 min to 10 min to obtain the PA NF membrane.