The invention discloses an energy-saving
nanofiltration membrane for a water purification
system and a preparation method of the energy-saving
nanofiltration membrane. The energy-saving
nanofiltration membrane is composed of non-woven cloth, a
polysulfone supporting layer, a loose
polyamide separating layer and a dense positive charge
thin layer. By properly hydrolyzing the dense nanofiltration membrane, the molecular weight
cut-off of the nanofiltration membrane can be increased, and part of
monovalent ions are selectively allowed to permeate while it is guaranteed that small
organic molecules are effectively intercepted, so that the nanofiltration membrane still has a high
permeation flux under high-
salinity water inlet or a high
recovery rate, and it is unnecessary to additionally increase operating pressure. By depositing the dense positive charge
thin layer on the surface of the loose
polyamide separating layer through
electrostatic adsorption-chemical crosslinking, interception of the nanofiltration membrane on multivalent cations (such as
calcium ions,
magnesium ions, heavy
metal and other substances harmful to the
human body) in water can be easily improved, and drinking
water safety can be guaranteed to a great degree; meanwhile, the thickness of the deposition
coating can be effectively controlled within a certain range with the
electrostatic adsorption technology, and thus substantial increase of
permeation resistance can be avoided as far as possible.