# Suppressing Salt Transport through Composite Pervaporation Membranes for Brine Desalination
## 4 Conclusions  
Initially, in this work, composite membrane desalination performance was optimized by varying the cross-linking density of PVA. The results suggested the transport of salt ions through the membrane followed the solution-diffusion mechanism in the form of hydrated ions. Then, by incorporating a small amount of GO (0.1 wt. %) into PVA matrix, a high salt rejection can be maintained during the extended desalination operation, while the flux was relatively unaffected. This can be attributed to the impermeable properties of GO to salt ions and fast water molecule transport along its surface. In addition, the presence of polar groups on GO can also form hydrogen bonds with PVA, which rigidified the PVA chains and suppressed the transport of bulkier salt ions. The GO/PVA composite membrane also exhibited satisfactory anti-fouling properties during the treatment of calcium and humic-containing brine wastewater. Lastly, the study on permeate pressure indicated its crucial role in affecting the membrane productivity for such PVA-based pervaporation membranes.  
The following are available online at www.mdpi.com/2076-3417/7/8/856/s1. Figure S1: Contact angle after membrane pre-treatment, Figure S2: Flux and conductivity profile of composite PVDF membrane with KOH/MR 0.2/5 wt. % by one layer casting, where the membrane was cleaned with in-situ cleaning method: (top) \"96 h 100 g/L NaCl + 24 h Milli-Q water cycle; (bottom) \"23 h 100 g/L NaCl + 1 h Milli-Q water cycle\". The feed inlet temperature is 65 \(\pm\) 1 \({}^{\circ}\)C, Figure S3: Flux and conductivity profile of composite PVA/PVDF membrane with KOH/MR 0.2/5 wt. % by one layer casting using a feed solution of 30 g/L, 100 g/L NaCl and PAC solution with the same conductivity as 30 g/L NaCl (~55 mS/cm). The feed inlet temperature was 65 \(\pm\) 1 \({}^{\circ}\)C, Figure S4: Cross-sectional SEM images of the composite membrane fabricated with the cast coating: (a,b) PVA/PVDF, (c,d) PVA0.1 GO/PVDF, Figure S5: Digital photo of freestanding PVA samples with different GO loadings: (a) 0, (b) 0.1 wt. %, (c) 0.2 wt. %, and (d) 0.3 wt. %, Figure S6: SEM images of freestanding PVA membrane with GO loading of (a), (b) 0.1 wt. %, (c) 0.2 wt. %, (d) magnified 0.1 wt. %, Figure S7: XRD curves of GO only/PVDF, freestanding PVA, and freestanding PVA with GO loading of 0.1 wt. %, Figure S8: Flux profile of composite membrane PVA0.1 GO/PVDF using Milli-Q water, 100 g/L NaCl and Milli-Q water as the feed, sequentially, Table S1: Contact angles of the composite membrane samples with different GO loadings.  
This research was supported under Australian Research Council's Discovery Projects funding scheme (DP130104048).  
Figure 11: (**a**) Flux and (**b**) permeate conductivity profiles of composite PVA/PVDF membrane (MR value of 0.2) and PVA0.1 GO/PVDF membrane using 2 L of 100 g/L NaCl as the feed without top-up at operating temperature of 65 \({}^{\circ}\)C.  
**Author Contributions:** [PERSON], [PERSON] and [PERSON] conceived the idea of suppressing salt transport by GO incorporation. The experimental work was carried out by [PERSON]. [PERSON] and [PERSON] built the pervaporation setup. [PERSON], [PERSON], [PERSON], [PERSON], [PERSON] and [PERSON] contributed to the manuscript writing and editing.  
**Conflicts of Interest:** The authors declare no conflict of interest.