Biodegradable and biocompatible temperature sensitive triblock copolymer hydrogels as draw agents for forward osmosis

• Biodegradable and biocompatible temperature sensitive hydrogels were prepared.
• Prepared hydrogels were used as draw agents for FO desalination process.
• Prepared hydrogels are temperature responsive and good in dewatering properties.
• Well in hydrophilic behavior, this can lead higher water fluxes.

Recently, polymer hydrogels have been studying as a draw agent in forward osmosis (FO) due to their low toxicity, reusability and dewatering abilities. In this research work, we studied five triblock copolymer hydrogels as draw agents in FO process. Hydrogels were synthesized by ring opening polymerization of monomers d,l-lactide, Glycolide, methyl ether poly ethylene and stannous octane as catalyst. Prepared hydrogel named as “poly(ethylene glycol-[dl-lactic acid-co-glycolic acid]-b-ethylene glycol) (PEG-PLGA-PEG).” Different weight percentages i.e., 0.09 and 0.18 wt% of Graphene oxide (GO) and Graphene (Gr) were incorporated in hydrogels and named as “PEG-PLGA-PEG/GO-0.09 wt%, PEG-PLGA-PEG/GO-0.18 wt%, PEG-PLGA-PEG/G-0.09 wt% and PEG-PLGA-PEG/G-0.18 wt%.” Different types of characterization technique were used to characterize the prepared hydrogels i.e., H NMR spectrophotometers, Fourier transform infrared spectrometer (FTIR), Scanning electron microscopy (SEM), Molecular weights (MWs) measured Gel Permeation Chromatography (GPC), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). All the five prepared hydrogels were tested as draw agents in FO process to check the effect of GO and G on swelling properties, water fluxes, and water recovery. After FO experiments results advocate, GO incorporation in polymer hydrogels increase the swelling ratios and thus yields higher water fluxes among all hydrogels. By using PEG-PLGA-PEG/GO-0.09 wt% and PEG-PLGA-PEG/GO-0.18 wt% hydrogels as draw agents, deionized (DI) water and 2000 ppm NaCl as feed solutions, the average water fluxes obtained are 0.68 LMH, 0.57 LMH and 0.55 LMH, 0.48 LMH, respectively. All prepared hydrogels remained active up to two times regeneration and these hydrogels were shown negligible reverse solute diffusive flux through the FO membrane.