Ionic Liquid-Assisted Alignment of Corn Straw Microcrystalline Cellulose Aerogels with Low Tortuosity Channels for Salt-Assistance Solar Steam Evaporators

The development of a highly salt-resistant solar evaporator with long-term energy conversion is essential for practical solar desalination. Herein, we first report the ionic liquid-assisted alignment of corn straw-based microcrystalline and oxidized microcrystalline cellulose for preparation of biomass aerogel (abbreviated as CSMCA and CSOMCA) evaporators with low tortuosity channels for salt-assistance solar steam generation. By coating of carbonized cornstalk nanoparticles onto CSMCA and CSOMCA as light-absorbing layers (named C-CSMCA and C-CSOMCA), the light absorption of C-CSMCA and C-CSOMCA reaches 92 and 95%, respectively. The formation of strong H-bonding between pyranoid rings of cellulose in the presence of the ionic liquid would result in a reorientation of microcrystalline cellulose, which makes it possible to create vertically aligned channels of CSMCA and CSOMCA after replacement of solvents, followed by freeze drying. Combined with their low thermal conductivity (0.037 and 0.043 W m^–1 K^–1), high porosity, and intrinsic superhydrophilicity, C-CSMCA and C-CSOMCA exhibit high evaporation rates (1.44 and 1.36 kg m^–2 h^–1) and excellent energy conversion efficiencies (88 and 84%). In particular, bearing with vertically aligned channels, C-CSMCA and C-CSOMCA possess excellent salt tolerance for solar desalination due to a rapid resolving and return of the crystalline salt into water, for example, no surface salt crystallization for C-CSMCA after 20 days of continuous evaporation. Moreover, both C-CSMCA and C-CSOMCA have excellent sewage treatment capacity and can efficiently absorb dyes and heavy-metal ions in water bodies, showing great potential in actual desalination and sewage treatment based on their cost-effective, simple, scalable, and green manufacture.