Poly(vinyl alcohol) (PVA)-Enhanced Hybrid Hydrogels of Hyperbranched Poly(ether amine) (hPEA) for Selective Adsorption and Separation of Dyes

The unique selective adsorption of hydrophilic dyes gives the hybrid hydrogels of hyperbranched poly(ether amine) (SiO1.5-hPEA-Gels) potential in the separation. We here introduced poly(vinyl alcohol) (PVA) to enhance the mechanical strength of hybrid hydrogels to extend them into the practical application. A series of PVA-enhanced hybrid hydrogels (PVA@SiO1.5-hPEA-Gels) were prepared by chemically cross-linking between hydroxyl groups of PVA and trimethoxysilyl groups of hyperbranched poly(ether amine) (TMS-hPEA) in water. The compress stress of PVA@SiO1.5-hPEA-Gels increased significantly with the increasing content of PVA. Compared to hybrid hydrogel without PVA, the stress of PVA@SiO1.5-hPEA-1/2-Gel containing 33% PVA increased hundreds of times. The adsorption behavior of the obtained PVA-enhanced hydrogels to ten hydrophilic dyes was investigated in detail. Regardless of their charge states, PVA@SiO1.5-hPEA-Gels exhibited the quick adsorption to Ponceau S (PS), Rose Bengal (RB), Orange G (OG), and Ponceau SX (PSX) with a high adsorption capacity (Qeq) and very slow adsorption of Bismarck brown Y (BY), Methylene Blue trihydrate (MB), and Rhodamine 6G (R6G) with a low adsorption capacity. The adsorption process was found to follow the pseudo-second-order kinetics, and the introduction of PVA has no obvious effect on the adsorption behavior in this study. The big difference in the adsorption to the different dyes is indicative of the selective adsorption of PVA@SiO1.5-hPEAGels to dyes. A methodology of dynamic separation of dye's mixtures (PS/BY and OG/MB) in water is finally demonstrated by using PVA@SiO1.5-hPEA-Gels.