Influence of incorporating beta zeolite nanoparticles on water permeability and ion selectivity of polyamide nanofiltration membranes

A novel polyamide (PA) thin film nanocomposite (TFN) membrane modified with Beta (β) zeolite was prepared by interfacial polymerization on a poly (ether sulfone) (PES) ultrafiltration membrane. Compared with the PA thin film composite (TFC) membrane, the introduction of β zeolite with porous structure notably increased the water flux of TFN membrane. Because the β zeolite with tiny-sized and well-defined inner-porous acted as prior flow channels for water molecules and a barrier for the sulfate ions. The successful introduction of β zeolite into the (PA) selective layer and their dispersion in the corresponding layer were verified by scanning electron microscope (SEM) and atomic force microscopy (AFM). Water contact angle, zeta potential measurements were used to characterize the changes of membrane surface properties before and after incorporating the β zeolite. With the β zeolite introducing, the water contact angle of modified TFN membrane was decreased to 47.8°, which was benefited to improve the water flux. Meanwhile, the negative charges of the modified TFN membrane was increased, resulting in an enhancement of separation effect on SO42- and Cl-. In term of nanofiltration (NF) experiments, the highest pure water flux of the TFN membranes reached up to 81.22 L m-2 hr-1 under operating pressure of 0.2 MPa, which was 2.5 times as much as the pristine TFC membrane.