Influence of hexamethyl phosphoramide on polyamide composite reverse osmosis membrane performance

In this study, TFC RO membranes were prepared through interfacial polymerization with hexamethyl phosphoramide (HMPA) as an additive in the aqueous phase. There are two main highlights as follows: ▶ The flux of the membrane was greatly enhanced by the addition of HMPA, while maintaining good salt rejection. The flux and salt rejection of MH-3 membrane (3 wt% HMPA addition) reached 51.67 L/m2 h and 98.27%, respectively, for 2000 mg/L NaCl under 1.55 MPa. The flux increased by 73% and the salt rejection loss was less than 0.21% compared with the non-additive membrane. ▶ The colloidal silica fouling experiments results suggested that conventional roughness parameters such as Ra, Rms and Δ were insufficient to explain the colloidal fouling behavior in our study. We think that the average peak-valley distance and average peak spacing width on the membrane surface were related to the membrane fouling behavior.