Microwave-Assisted Syntheses of 1-Acetyl 2-Methylbenzimidazole Sodium Bisulfate pH-Responsive Ionic Draw Solute for Forward Osmosis Applications

This work is related to the development of a highly efficient pH-responsive ionic draw solute for forward osmosis applications utilizing microwave-assisted fast heating. This solute is classified as an ionic compound, a sodium salt originating from imidazole, with the scientific acronym 1-acetyl-2-methylbenzimidazole sodium bisulfate (AMBIM-Na). The synthesized compound was analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), as well as additional physical characteristics. The baseline performance was initially evaluated at various molar concentrations against distilled water as the feed solution (FS). The results indicated that the produced solute exhibits elevated osmotic pressure, resulting in a water flux of up to 130 LMH for a 1 M concentration, coupled with the absence of reverse salt flux. The synthesized AMBIM-Na at a concentration of 1 M was utilized as a draw solution (DS) against synthetic brackish water. The water flux declined progressively with the increase in FS concentration, decreasing from 130 LMH with distilled water to 99, 70, and 41 LMH at NaCl concentrations of 5, 10, and 15 g/L, respectively. The regeneration of the draw solute was assessed using pH adjustment, revealing that 100% regeneration occurs by reducing the pH to 2.