Tough porous nanocomposite hydrogel for water treatment

Developing a cost-effective, stable, and recyclable adsorbent with high adsorption capacity and rapid adsorption kinetics is highly demanded for water treatment but has been proven challenging. Herein, we report a one-step strategy to synthesize tough porous nanocomposite hydrogel, by introducing biochar nanoparticles and interconnected pores into a polyacrylamide hydrogel matrix as an exemplary system. The polyacrylamide hydrogel provides the overall mechanical strength to carry loads and facilitate recycling, the biochar provides adsorptive locus for high adsorption capacity, and the interconnected pores expedite solvent transport for rapid adsorption kinetics. Mechanical characterizations manifest that the porous biochar hydrogel possesses a tensile strength of 128 kPa, a stretchability of 5.9, and a toughness of 538 J m^-2. Porous structure analysis reveals that the hydrogel contains an increscent specific surface area by 441% and an augmented pore volume by 279% compared to pure polyacrylamide hydrogel. Experiments pertaining to adsorption isotherms and kinetics, with methylene blue as the model adsorbate, indicate enhanced adsorption performances. The tough hydrogel also allows facile recycling and maintains mechanical robustness after five regeneration cycles. Furthermore, biocompatibility is endorsed by cytotoxicity test. The proposed method could open an ample space for designing and synthesizing tough porous nanocomposite hydrogels for water treatment.