Facile preparation of sodium alginate/poly(vinyl alcohol)/graphite hybrid porous hydrogel for efficient solar desalination

Porous hydrogel incorporated with the photothermal conversion materials has been the key component of the interfacial solar evaporation device. However, the preparation of high-performance porous hydrogel for the interfacial solar evaporation device still existed some limitation, like the widely available and cheap photothermal conversion material, the ease and scalability of porous structure construction in the hydrogel. In this work, a porous biomass-derived hydrogel evaporator with interconnected pore structure were developed via the simple and effective foaming-freezing-crosslinking three-step method using sodium alginate and poly(vinyl alcohol) as matrix materials and commercial graphite as the photothermal material. It has excellent photothermal conversion and water transport capabilities, with an evaporation rate of 3.15 kg m-2h−1 and an evaporation efficiency of 91 % at a solar irradiation intensity of 1 kW m−2. The evaporator also has excellent salt rejection performance due to its unique porosity. The evaporator shows good stability and long-term durability when evaporating in brine cycles. This easily prepared, inexpensive and biocompatible hydrogel evaporator has great potential in the field of solar desalination.