Multifunctional bio-based photothermal hydrogel for highly efficient seawater desalination and contaminant adsorption

In this paper, a vertically aligned porous photothermal PVA-psyllium husk hybrid hydrogel (PHH) has been prepared by introducing naturally abundant biomass psyllium husk (PH), along with nitrogen-doped carbon quantum dots-iron oxide hybrid nanocomposite (NCQD@Fe 3 O 4 ) into polyvinyl alcohol hydrogel. Using PHH, an evaporation rate of 2.6 kg m −2 h −1 and ≈ 92% solar to vapor conversion efficiency have been achieved under 1 sun. After 10 cycling tests, PHH shows an evaporation rate of ⁓ 2.5 to 2.6 kg m -2 h -1 under different harsh conditions (pH 3-14 and salinity up to 250 g/kg), indicating long-lasting stability. In addition to this, the PHH evaporator shows excellent salt-resistant desalination and contaminant adsorption performance in seawater. Owing to a series of merits such as cost-effectiveness ($5.23/m 2 ), high vapor conversion efficiency, excellent transport, and salt mitigation properties this renewable biomass-based evaporator may open new possibilities in the deployment of low-cost solar water purifiers with assured water quality. • A biomass photothermal hydrogel has been prepared. • An evaporation rate of 2.6 kg m −2 h −1 and ≈ 92% solar-to-vapor conversion efficiency have been achieved under 1 sun. • Superhydrophilicity and vertically aligned channels impart salt rejection property. • The material shows good adsorption towards organic and inorganic contaminants.