Electro-responsive PVA/PAMPS hydrogel draw agents for high-flux forward osmosis desalination with efficient...

Conventional forward osmosis (FO) draw solutes are limited by low water flux and inefficient regeneration. To address these challenges, this study develops a series of electro-responsive PVA-based composite hydrogels by integrating sodium alginate (SA), polyacrylic acid (PAA), and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) through a combined free-radical polymerization and cyclic freeze-thaw approach. The resulting PVA/PAMPS hydrogels exhibit enhanced mechanical strength (96.18 kPa) and macroporous morphology, ensuring high porosity, low density, and efficient water transport. The incorporation of hydrophilic functional groups (-OH, -COOH, -SO₃H) improves proton conductivity and water retention, facilitating rapid electro-deswelling under low-voltage stimulation. Swelling analysis reveals non-Fickian diffusion behavior with an equilibrium swelling ratio of 22.28 g/g, while the dehydration rate increases proportionally with applied voltage (15 V). In FO performance tests with the active layer facing the draw solution (AL-DS), the hydrogel achieved a maximum pure water flux of 2.19 L/(m² h). Using deionized water and 1000 mg/L NaCl as feed solutions, cumulative water fluxes of 80.55 L/m² and 35.76 L/m² were obtained over 60 h, respectively, demonstrating strong salt rejection and operational stability. This work highlights the potential of electro-responsive AMPS/PAMPS hydrogels as efficient, regenerable, and mechanically robust draw agents for next-generation FO desalination and wastewater treatment.