Interfacial evaporation using light-absorbing hydrogels
offers
efficient solar evaporation performance under natural sunlight, ensuring
an affordable clean water supply. However, achieving light-absorbing
hydrogels with durable and efficient utilization is still a challenge
due to inevitable salt accumulation, a difficult-to-control surface
morphology, and poor mechanical properties on the surfaces of hydrogel-based
evaporators. In this work, a photothermal sponge-like hydrogel with
a 3D interconnected porous structure was constructed using low-cost
activated carbon as a photothermal material, as well as a double-network
polymer chain as the basic skeleton using a simple foaming polymerization
strategy. The sponge-like hydrogel evaporator showed tailored surface
topography, adequate water transport, excellent elasticity and toughness,
good salt rejection, and thermal localization properties. Under the
irradiation of simulated sunlight (1.0 kW/m2), a high evaporation
rate of 2.33 kg·m–2·h–1 was achieved. Furthermore, efficient salt self-cleaning behavior
was achieved due to the fast ion diffusion within the 3D interconnected
porous structures. Even in highly concentrated brine of 15 wt %, continuous
and efficient water evaporation was still achieved. The excellent
evaporation and salt rejection properties of this photothermal sponge-like
hydrogel indicated its promising long-term sustainable utilization
in seawater desalination.
Solar evaporative desalination technology is one of the most promising technologies to alleviate freshwater shortages, but the preparation of an inexpensive and sustainable 3D substrate remains a challenge. Lignocellulosic sponge (LS) is a commercial product that is widely available, clean, renewable, degradable, inexpensive, and porous. In this work, LS was found to be a good substrate for photothermal evaporation. LS has good compatibility with polypyrrole (PPy), which has excellent photothermal conversion performance. A simple and effective photothermal conversion evaporator (PPy-LS) was obtained by in situ polymerization of pyrrole on the surface of LS by chemical oxidation. The as-prepared PPy-LS exhibited good light absorption and thermal management capabilities, possessing an evaporation rate of 1.85 kg m −2 h −1 and an evaporation efficiency of 88.65% at 1 sunlight. PPy-LS also had excellent mechanical properties, superhydrophilicity, and water absorption. Combined with its porous network structure, PPy-LS exhibited good salt tolerance in 10 wt % NaCl solution and excellent thermal management capability. The PPy-LS solar evaporation device has the advantages of a simple preparation method, good durability, and sustainability, which provides an important direction for solar interface evaporation.
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