Multiapplication Triple Network Hydrogel for Desalination and Water Treatment

ABSTRACT Solar evaporators are promising for freshwater generation from seawater and wastewater, but are currently made from fossil‐based materials compromising their sustainable profile. We developed a triple network hydrogel (CTMH) for solar‐driven water purification. The hydrogel combines Fe‐based metal–organic framework nanoparticles (Fe‐MOF NPs) as light‐absorbing components with two bio‐derived polymers: sodium carboxymethyl cellulose (CMC) and starch. These polymers tailored the pore structure and swelling properties of the cellulose fibers. The hydrogel has a light absorption of 94%. The porosities together with the hydrophilic nature of the hydrogel constituents almost half the water evaporation enthalpy to 1301 J·g −1 . Through the synergistic effects, an evaporation rate of 2.55 kg·m −2 ·h −1 and a photothermal conversion of 92.2% are obtained for the CTMH hydrogel. In addition, the CTMH hydrogel has excellent salt resistance. The abundant hydroxyl groups remove up to 99.9% of methylene blue (MB), methyl orange (MO), and rhodamine B (RhB) dyes by adsorption through hydrogen bonding and electrostatic interaction. Purification efficiency is up to 99% for seawater and wastewater. Therefore, the bio‐based triple network CTMH hydrogel has great potential for seawater desalination and dyeing wastewater purification.