The fouling layers characteristics of osmotically driven membranes affect transport behaviors of reverse salt permeation and per-fluorinated compounds

Perfluorinated compounds (PFCs) adversely affect the environment in very small amounts and are extremely stable substances. This study investigated the transport phenomenon of PFCs in terms of functional groups and membrane fouling types using 10 types of PFCs and evaluated the performance of osmotically driven membranes. The experimental results confirmed that the reverse salt flux (RSF) of organic fouled membranes significantly decreased (16.2 % and 22.3 %, respectively) and the relatively loosely deposited MP fouled membranes with many empty spaces in the fouling layers maintained RSF values similar to those of virgin membranes (2 % decreased). The rejection rates of the PFCs with SO3H functional groups increased (virgin: 96.8 %; fouled: 98.6 %), whereas PFCs with COOH functional groups decreased after organic matter fouling (virgin: 99.5 %; fouled 97.6 %). The micelles formation by PFCs with SO3H group was easily blocking fouling layers and intra-particle diffusion of other PFCs with SO3H molecules interrupt. PFCs having high Kow values tends to have increased removal efficiency after the formation of MP fouling layer. These results demonstrated that the membrane fouling layers play positive roles in the RSF and PFCs removal efficiencies in osmotically driven membrane processes, which will enable the securing of safe water resources.