Enhancement of reverse osmosis membranes for groundwater purification using cellulose acetate incorporated with ultrathin graphitic carbon nitride nanosheets

Abstract

Modified reverse osmosis (RO) membranes are emerging in the fields of water desalination and purification as next-generation separation techniques. Highly efficient graphitic carbon nitride (g-C3N4) RO membranes were fabricated by incorporating g-C3N4 into polyvinyl alcohol-based cellulose acetate. X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy were employed to determine the crystal structure and textural qualities of the ultrathin graphitic layers. The interlayer spacing of the g-C3N4 in the modified membranes was relatively narrow, which significantly impacted membrane performance. Phase inversion was employed to fabricate uniform and compact g-C3N4 hybrid membranes. The impact of the g-C3N4 loading quantity in the polymeric solution on viscosity and membrane performance was investigated. An optimized concentration of 0.5 wt% for the ultrathin g-C3N4 resulted in a distinguished dense top layer. The fabricated RO membranes were evaluated using a synthetic saline solution (2000 ppm of NaCl), resulting in a percentage rejection of 95% at a reasonable operating pressure of 15 bar to exhibit 10.5 LMH. The fabricated membranes exhibited self-cleaning properties after soaking in malachite green dye (10 mgL−l); this demonstrated the antifouling properties of the membrane. The g-C3N4 membrane was successfully applied in a groundwater purification process and its efficiency was observed to reach approximately 97%. This membrane is promising for groundwater treatment.