Novel sodium and potassium carbon quantum dots as forward osmosis draw solutes: Synthesis, characterization and performance testing
Afraa H. Kamel, Qusay F. Alsalhy, Salah S. Ibrahim, Khalefa A. Faneer, S.A. Hashemifard, Amir Jangizehi, Sebastian Seiffert, Michael Maskos, Alireza Shakeri, Christoph Bantz
Abstract
Novel draw solutes based on potassium- and modified sodium-functionalized carbon quantum dots (K-CQDs and Na-CQDs) were prepared for seawater desalination. The characteristics of draw solutes were determined using Fourier Transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray (EDX) spectroscopy, and thermal gravimetric analysis (TGA). The results of the FO system with K-CQDs and deionized water (DI) as a feed revealed a high water flux of 10.94–13.924 L/m2.h (LMH), very low reverse solute flux of 0.0161–0.0253 g/m2.h (gMH), and specific reverse solute flux of 0.0015–0.0018 at a concentration of 0.3–0.5 g/mL. The water flux of K-CQDs at a concentration of (0.3–0.5) g/mL for seawater and 0.5 g/mL for Real Persian Gulf (RPG) water (Arabian Gulf) was (3.779–5.371) LMH and 6.1662 LMH, respectively. For Na-CQDs with DI, the obtained water flux, reverse solute flux, and specific reverse solute flux were 10.3433–11.935 LMH, 0.0414–0.0621 gMH of 0.004–0.0052, respectively at a concentration of 0.3–0.5 g/mL at 29 °C. The fluxes of synthetic seawater and RPG with K-CQDs and Na-CQDs were 5.37 and 6.16 LMH and 2.78 and 3.78 LMH, respectively, at CQDs concentration of 0.5 g/mL. The stability test showed that there was only a slight decrease in the flux of 2 % after three-cycle of FO operations with K-CQDs.