Influences of sulfonation level on the nanofiltration performance of sulfonated graphene oxide polyamide nanocomposite membranes

Abstract

Abstract In this study, thin-film nanocomposite (TFN) membranes containing sulfonated graphene oxide (SGO) were prepared and used for water desalination. SGO sulfonation level influences on the physicochemical and separation performance of the prepared TFNs were studied. The TFN membranes were synthesized by interfacial polymerization of 1,3-Phenylene diamine (MPD),1,3,5-benzenetricarbonyl trichloride, and sodium dodecyl sulfate as an additive on polyethersulfone support, while GO and SGOs were dispersed in an aqueous solution of MPD. The physicochemical characterization of GO and SGO samples revealed that the sulfonation level of GO greatly influences the interlayer d-spacing, ion exchange capacity, and zeta potential of GO. Morphology analysis confirmed that GO and SGO were incorporated into the polyimide layer and that the SGO sulfonation level greatly influences the surface morphologies of TFN membranes. Generally, SGO incorporated TFN membranes provided higher hydrophilicity, water uptake, and more desirable surface morphologies for the desalination processes. Increasing the sulfonation level from 25 to 50 % wt of sulfanilic acid to GO led to a notable improvement in the salt rejection of SGO-incorporated TFNs, and it reached to about 97% for Na2SO4. This was also accompanied by a considerable increase in these membranes pure water flux, compared to the GO-containing TFN membranes (∼ 42 %) and the TFC membranes (∼ 4 times). Furthermore, the flux recovery ratio of this membrane was about 24% higher compared to the unmodified membranes, indicating the promising influences of the sulfonated groups on the compatibility, recovery and the reuse of TFN membranes.