The influence of RO membrane surface properties on surfactant fouling in radioactive wastewater treatment

Abstract

Reverse osmosis (RO) has been shown to be an efficient treatment method for radioactive wastewater, which has been employed in nuclear power plants. However, the fouling on RO membrane surface should be solved to fabricate modified RO membranes with selective and fouling-resistant surface, which is essential for the further widespread application of RO. To provide fundamental insights into fouling control methods, the influence of surface properties on surfactant fouling was investigated with modified RO membranes. The results showed that surfactant fouling reduced the flux of RO membranes by 35 %–75 %. The interfacial free energies associated with the surfactants and RO membranes surface were calculated by XDLVO theory to explain surfactant fouling mechanisms. The interfacial free energies associated with CTAB and RO membrane surface increased from 3.18 to 41.22 and 69.62 mJ m−2 and SDBS increased from 20.21 to 34.07 and 43.97 mJ m−2, Tween 80 increased from -2.63 to 3.98 and 9.61 mJ m−2 with PEI and EPTAC grafting. The results indicated that the changes of interfacial free energies were mainly caused by the changes of membrane hydrophilicity and surface charge. Fabricating RO membrane with hydrophilic and neutrally charged surface was potential for improving all kinds of surfactants resistant capability. Besides, surfactant fouling had great influence on membrane permeability. The changes of radioactive nuclide rejections were mainly caused by the changes of membrane surface charge while the increase of boron rejection was attributed to the rise of membrane surface steric-hindrance. Therefore, the membrane hydrophilicity and surface charge should be carefully considered in radioactive wastewater containing surfactants treatment.