Electro-responsive semi-IPN hydrogel with enhanced responsive property for forward osmosis desalination

An electro-responsive hydrogel with semi-interpenetrating polymer networks (semi-IPN) composed of crosslinked poly(2-acrylamido-2-methyl-l-propanesulfonic acid-co-acrylamide) (P(AMPS-AM)) and linear polyelectrolyte polyacrylic acid (PAA) was explored. The semi-IPN hydrogel was characterized with different methods and then used as advanced draw agent toward high water recovery for forward osmosis (FO) desalination. The swelling kinetics of the semi-IPN hydrogel was investigated, and the electro-responsive nature of the hydrogel under electric stimulus (in direct contact with electrodes) was determined. Results indicated that in comparison with pure P(AMPS-AM) hydrogel, the semi-IPN hydrogel exhibited a loose network structure with more pores. In addition, a higher equilibrium swelling capacity and more pronounced deswelling under electric stimulus can be observed for the semi-IPN hydrogel. Furthermore, the semi-IPN hydrogel displayed a similar initial water flux of 2.20 L m⁻² h⁻¹ (LMH) from 2 g/L NaCl solution of a lab-scale FO process. Importantly, the semi-IPN hydrogel had a 25% increase in water recovery efficiency under the electric stimulus of 15 V, and showed better recyclability during three cycles of regeneration compared with pure P(AMPS-AM). The mechanism of enhanced dewatering nature for the semi-IPN hydrogel under electric stimulus was elucidated. These results indicate this new hydrogel's potential as a promising candidate for improving FO performance.