Synthesis and characterization of an innovative poly vinyl alcohol / sodium alginate bioartificial hydrogel for forward-osmosis desalination

Abstract

Abstract Hydrogels are three-dimensional network of polymeric materials that can hold large amount of water due to their hydrophilic structure. Hydrogels have received considerable attention for their use in FO desalination. The primary goal of the present work is the synthesis of a bioartificial hydrogel from a blend of sodium alginate (SA) and polyvinyl alcohol (PVA) using epichlorohydrin (EPC) as cross-linking agent. The effects of the percentage of PVA in the blend and cross linker / total polymer ratio on equilibrium swelling ratio (ESR) were investigated to optimize the hydrogel’s composition. Furthermore, the water flux and the reverse solute flux of the optimum PVA/SA hydrogel was evaluated in batch FO unit under the effect of different parameters such as: hydrogel particle size, temperature of feed solution, feed solution concentration and membrane orientation. FTIR spectroscopy, SEM, XRD were used to characterize the prepared hydrogel. In addition, mechanical properties of the prepared hydrogel were measured. Results reveal that maximum % ESR of 5228 was achieved with a hydrogel which has 25% PVA and cross linker/total polymer ratio of 0.8. FO experimental data indicated that as the hydrogel particle size decreases the water flux increases. However, the increase of feed solution temperature has a proportional effect on water flux whereas the feed solution concentration has a reverse effect on water flux. PRO mode proves to be superior to FO mode. In all FO experiment reverse solute flux approached zero. The performance of the present hydrogel to desalinate real brackish water has been examined.