Reverse osmosis (RO) is considered a lifesaver technology to conquer the current catastrophic water shortage situation. However, reaching a competitive RO membrane is a challenging issue. Therefore, this study investigated the optimum polymeric blending ratio between cellulose acetate (CA) and polyvinylidene fluoride (PVDF) to have a new blended polymeric membrane named cellulose acetate polyvinyl (CAPV-X), where X is the PVDF concentration %, with enhanced properties. The optimum prepared CA/PVDF blended membrane was selected for further enhancement with nano sized metal organic framework (UiO-66 MOF). Selection was made depending on each membrane salt rejection. A membrane characterization was performed based on Fourier transform infrared (FTIR), X-ray diffractometer (XRD), scanning electron microscope, thermal gravimetric analysis, and contact angle. FTIR and XRD data confirmed the successful preparation of the blended polymeric membranes CAPV-5, CAPV-7 and CAPV-10. Further, they proved UiO-66 nanofiller impregnation in the hybrid CA/PVDF/UiO-66 membrane (CPU). The addition of PVDF and nano-MOF had a slight positive effect on the membrane thermal stability. The contact angle increased with increasing the PVDF concentration and decreased once more with the impregnation of UiO-66. The RO membrane performance revealed that the optimum CA/PVDF ratio was found to be 93/7% with around 80% salt rejection and a permeate water flux of 4 L/m² h. CPU composite membrane was then fabricated to enhance salt rejection and permeate water flux. The testing data indicated that salt rejection and permeate water flux increased over blended CAPV-7 membrane by almost 12% and 42%, respectively. Overall, CPU hybrid membrane could be used for water desalination with a good salt rejection of 90.2% and a permeate water flux of 5.7 L/m² h. Graphical abstract

Many reasons have caused a worldwide water stress problem. Thus, the recycling of wastewater streams has been extensively studied. In this work, eco-friendly mixed matrix membranes (MMMs) were fabricated, characterized, and tested for the removal of two separate dyes from simulated waste streams. The environmentally friendly nano activated carbon (NAC) was extracted from water hyacinth to be impregnated as a membrane nano-filler to enhance the neat membrane performance. The extracted NAC was further studied and characterized. Cellulose acetate (CA)-based membranes were obtained by phase inversion and electrospinning mechanisms. All four synthesized blank and MMMs were characterized via scanning electron microscope (SEM) and contact angle to study their structure and hydrophilic nature, respectively. However, the membrane with optimum performance was further characterized using Fourier transfer infrared (FTIR) and X-ray diffraction (XRD). The four prepared cast and electro-spun, blank, and mixed matrix CA-based membranes showed an acceptable performance in the removal and selectivity of methylene blue (MB) dye over Congo red (CR) dye with a removal percentage ranging from 31 to 70% depending on the membrane used. It was found that the CA/NAC hybrid nanofiber membrane possessed the highest removal efficiency for MB, where the dye concentration declined from 10 to 2.92 mg/L. In contrast, the cast blank CA membrane showed the least removal percentage among the synthesized membranes with only 30% removal. As a result, this paper suggests the use of the CA/NAC hybrid membrane as an alternative and cost-effective solution for MB dye removal.

A nanosized zirconium 1,4- dicarboxybenzene metal-organic framework (UiO-66-MOF) was synthesized and impregnated into cellulose acetate (CA) polymeric matrix to enhance the membrane characteristics for brackish water desalination. Phase inversion was used for the fabrication of CA/UiO-66 hybrid membranes (CAU-X), where X is the concentration of immobilized UiO-66 nanoparticles (UiO-66-NPs) into CA polymeric matrix. Morphological structure and functional groups were investigated through different characterization techniques to prove the successful synthesis of the prepared UiO-66-NPs, the blank CA membrane, and hybrid CAU-X membranes. For more CAU-X characteristics, porosity, contact angle, and tensile strength were measured. The obtained data demonstrated that the impregnation of zirconium-based-NPs had a positive influence on the blank CA membrane properties. Additionally, the performance of the fabricated membranes was investigated in reverse osmosis (RO) bench-scale unit. The performance results for the pristine CAU-0 membrane showed a high salt rejection (SR) of 99.8% and a permeate water flux (PWF) of 1.14 L/m².h. In comparison to pristine CA membrane, CAU-X hybrid membranes have a slightly lower SR and a higher PWF. It was found that the hybrid CAU-0.02 membrane had almost a doubled PWF of 2.8 L/m².h with only 2% sacrificed SR of 97.6% compared with CAU-0 membrane. Moreover, a much better PWF of 3.4 L/m²h and a sufficient SR of approximetly 92% were obtained by CAU-0.05 membrane. Thus, CAU-0.05 was selected to further test its performance under different operating parameters. Results revealed that the optimum parameters were recorded for a sodium chloride feed stock of 5000 ppm operating at 25 °C temperature and pressure up to 15 bar. Graphical Abstract