Polyethersulfone-Quaternary Graphene Oxide-Sulfonated Polyethersulfone as a High-Performance Forward Osmosis Membrane Support Layer

The stability and compatibility of a nanomaterial in a substrate matrix are a tough challenge in preparing thin-film nanocomposite membranes. In this study, we fabricated a ternary nanocomposite membrane substrate consisting of polyethersulfone (PES), quaternary graphene oxide (QGO), and sulfonated polyethersulfone (SPES). First, SPES was blended with the PES substrate, and then different concentrations of QGO were incorporated within this substrate. The effect of QGO on the substrate morphology, hydrophilicity, and porosity was analyzed via scanning electron microscopy, water contact angle measurement, and gravimetric methods, respectively. The optimum loading of QGO significantly enhanced the hydrophilicity, porosity, and water permeability of the PES/SPES support layer. In addition, the effect of QGO on the polyamide rejection layer morphology and performance was thoroughly investigated. The result shows that a thin, smooth, and defect-free polyamide (PA) layer was formed on hydrophilic QGO-based substrates. Intrinsic separation performance data verified these results, where the PA layer formed on the QGO-based substrate presented the highest water permeability. The forward osmosis test also demonstrated the positive impact of QGO incorporation on the performance of membrane substrates. The optimal TFC-QS0.5 (containing 0.5 wt % of QGO) membrane has a water flux of 24.4 LMH in the forward osmosis mode and 32.1 LMH in the pressure-retarded osmosis mode when using a 1 M NaCl draw solution and deionized water feed solution.

Automated summary

In this study, a ternary nanocomposite membrane substrate consisting of polyethersulfone (PES), quaternary graphene oxide (QGO), and sulfonated polyethersulfone (SPES) was fabricated. The incorporation of an optimal loading of QGO significantly enhanced the hydrophilicity, porosity, and water permeability of the support layer. The effect of QGO on the morphology and performance of the polyamide rejection layer was also investigated, and it was found that the polyamide layer formed on a QGO-based substrate exhibited the highest water permeability. The forward osmosis test confirmed the positive impact of QGO incorporation on the performance of membrane substrates.