A novel polyurea nanofiltration membrane constructed by PEI/TA-MoS2 for efficient removal of heavy metal ions

• High-flux PEI-TDI PUNF membrane doped with TA-MoS 2 nanosheets was prepared. • MoS 2 nanosheets were uniformly dispersed in membrane by TA. • TSPU is positively charged and retains magnesium salts higher than sodium salts. • TSPU has good retention behavior for heavy metal ions. Heavy metal pollution poses a serious threat to human health. Positively charged nanofiltration membranes show excellent application prospects in the field of heavy metal removal due to the combined effect of electrostatic repulsion and size sieving. Here, molybdenum disulfide (MoS 2 ) nanosheets were dispersed in aqueous solution polyethyleneimine (PEI) by virtue of the adhesion effect of tannic acid (TA). Positively charged polyurea NF membranes (TSPU) were prepared by interfacial polymerization of aqueous phase PEI/TA-MoS 2 and organic phase 2,4-toluene diisocyanate (TDI). The surface of the optimized membrane TSPU-0.015 showed better hydrophilicity, the water contact angle was 74.53°, and the functional layer thickness of TSPU-0.015 was 114.8 nm. TSPU-0.015 interface was positively charged (IEP TSPU-0.015 =5.62), so the rejection of magnesium salts is significantly higher than that of sodium salts. It shows a retention performance of more than 99% for high-valent heavy metal ions such as Fe 3+ and Cu 2+ , and the retention for Cd 2+ is as high as 92.53%. The permeation flux of TSPU-0.015 is 2.88 times higher than that of undoped MoS 2 (TSPU-0), and the flux to MgSO 4 solution reaches 34.5 L/m 2 ·h (6 bar, R (MgSO4) = 93.18%). TSPU has long-term stable operation and excellent anti-pollution properties, showing wide application potential in the fields of inorganic salt separation and heavy metal pollution.