Using deep eutectic solvents for the in-situ synthesis of graphene-metal nanohybrids and nanocomposite membranes for dye desalination

Deep eutectic solvents (DESs) have recently gained much attention as an environmentally green solvent for different chemical reactions such as materials development. In this study, we used choline chloride/ethylene glycol DES to synthesize different graphene oxide (GO) based nanohybrids such as DES/GO-Fe2O3, DES/GO-Fe3O4, DES/GO-Ag, DES/GO-Au, and DES/GO-TiO2 by reducing the metal precursors to their associated nano-particles and conjugating them onto the GO surface. Different physical and chemical characterization techniques such as TEM, SEM-EDS, XRD, Raman, and FTIR confirmed the successful preparation of these nanohybrids and their properties. Among the synthesized nanohybrids, DES-GO/TiO2 was selected for the preparation of ultrafast lamellar nanofiltration membrane with self-cleaning properties. The filtration performance of the DES-GO/TiO2 membranes with different GO:TiO2 ratios, i.e., (4:1), (1:1), and (1:4), has been assessed to indicate the effect of TiO2 content on the performance of the membranes filtration. Also, the role of membrane loadings, i.e., 50, 250, and 400 mg/m2 was studied on the water permeance, and dye and salt rejections of the synthesized membranes. DES/GO-TiO2(1:4) membrane with 50 mg/m2 was able to provide the highest water permeance of 200.6 & PLUSMN; 1.7 LMH/Bar and 98.3 & PLUSMN; 1.2% of EB dye rejection while providing very low Na2SO4 salt rejection of 4.1 & PLUSMN; 0.2% indicating its potential effectiveness for selective dye/salt separation.