Design of nanofibre interlayer supported forward osmosis composite membranes and its evaluation in fouling study with cleaning

Nanofibre-supported forward osmosis(FO)membranes have gained popularity owing to their low structural parameters and high water flux.However,the nanofibrous membranes are less stable in long-term use,and their fouling behaviours with foulants in both feed solution(FS)and draw solution(DS)is less studied.This study developed a nanofibrous thin-film composite(TFC)FO membrane by designing a tiered dual-layer nanofibrous substrate to enhance membrane stability during long-term usage and cleaning.Various characterisation methods were used to study the effect of the electrospun nanofibre interlayer and drying time,which is the interval after removing the M-phenylenediamine(MPD)solution and before reacting with trimesoyl chloride(TMC)solution,on the intrinsic separation FO performance.The separation performance of the dual-layer nanofibrous FO membranes was examined using model foulants(sodium alginate and bovine serum albumin)in both the FS and DS.The dual-layer nanofibrous substrate was superior to the single-layer nanofibrous substrate and showed a flux of 30.2 L/m^(2)/h(LMH)when using 1.5 mol/L NaCl against deionised(DI)water in the active layer facing draw solution(AL-DS)mode.In the fouling test,the water flux was effectively improved without sacrificing the water/solute selectivity under the condition that foulants existed in both the FS and DS.In addition,the dual-layer nanofibrous TFC FO membrane was more robust during the fouling test and cleaning.