In-situ interfacial polymerization of zwitterionic nanofiltration membranes with anti-scaling performance

Abstract

Mineral scaling caused by multivalent metal ions can significantly hinder the long-term operation of nanofiltration membranes. In this study, in-situ interfacial polymerization including a posttreatment by using a citric acid solution was employed in order to mitigate scaling on the membrane surface. Under the optimal conditions (15 ​min of posttreatment with a 2 ​M citric acid solution), the membrane water permeance increased from 5.76 ​± ​0.2 to 15.1 ​± ​1.8 ​L⋅m⁻²⋅h⁻¹·bar⁻¹ for the pristine and the optimal membrane, respectively. The molecular weight cut-off of the optimal membrane was 399 ​Da, which allows for the removal of organic micropollutants in groundwater. Furthermore, the resulting membrane showed a Na₂SO₄ and CaCl₂ rejection of 92.5 ​± ​1.9 and 11.4 ​± ​1.3%, respectively. During the anti-scaling tests, the membrane fabricated with this strategy exhibited a minor decline of the water permeance of 33.5% when subjected to the same water recovery process, opposed to 65.8% for the pristine membrane. This proposed fabricating procedure thus provides an effective strategy for retarding membrane scaling in desalination applications.