Three-dimensional porous photo-thermal fiber felt with salt-resistant property for high efficient solar distillation

Enhancing Solar Steam Generation of Hydrogels via Silver Nanoparticle-Doped Cellulose Nanofibers

Solar steam generation (SSG) is regarded as an efficient approach for harnessing solar energy to purify polluted or saline water. Herein, we demonstrate a hydrogel composed of cellulose nanofibers (CNFs), polyethylenimine (PEI), and reduced graphene oxide (rGO) that functions as an independent solar steam generator, which shows enhanced solar water evaporation efficiency by incorporating silver nanoparticles (AgNPs). It presented that the presence of AgNPs increases the photothermal conversion efficiency and thermal conductivity of the evaporator and reduces the enthalpy of evaporation. As a result, an outstanding water evaporation rate of 3.62 kg m-2 h-1 and a photothermal conversion efficiency of 96.25% are successfully obtained under one sun illumination. Also, the resulting hydrogel exhibits exceptional mechanical properties, as well as outstanding desalination and salt-resistant abilities during prolonged seawater desalination. In oil/water mixtures, the evaporation of the hydrogel decreases to 2.94 kg m-2 h-1, owing to the oil layer barrier. This work paves a reference approach to produce easily addressed cellulose nanofiber (CNF)-based hydrogel evaporators with significantly enhanced evaporation rates.

Synergy of feed-side aeration and super slippery interface in membrane distillation for enhanced water flux and scaling mitigation

Membrane distillation (MD) is an acknowledged promising technology for desalinating hypersaline brine, and as such can be a suitable candidate to further concentrate the seawater discharged from reverse osmosis process. Mineral scaling represents a major constraint against the application of MD for further desalination of concentrated seawater, especially when considering CaSO₄ (gypsum) and NaCl. Up until now, it has been difficult to rely solely on membrane modification to mitigate CaSO₄ scaling. Permeate-side aeration can lessen CaSO₄ scaling, but does not permit to increase the water flux. Herein, we proposed the synergy of feed-side aeration and super slippery interface to perform concentrated seawater desalination via direct contact membrane distillation. The results of this study show that this synergistic effect could significantly increase the water flux, which was approximately 1.5 times higher in comparison to the membrane without aeration. Moreover, the synergistic effect effectively alleviates the complex scaling of concentrated seawater, achieving 90 wt% water recovery rate. Based on the observed results, we elucidated the mechanisms governing the enhanced water flux and scaling mitigation driven by the synergistic effect. In addition, we studied the optimal working condition for this system, unveiling that low-intensity large bubbles are more suitable as they lead to a better equilibrium between the economics and functionality of the process.

Nanostructured Photothermal Materials for Environmental and Catalytic Applications

Solar energy is a green and sustainable clean energy source. Its rational use can alleviate the energy crisis and environmental pollution. Directly converting solar energy into heat energy is the most efficient method among all solar conversion strategies. Recently, various environmental and energy applications based on nanostructured photothermal materials stimulated the re-examination of the interfacial solar energy conversion process. The design of photothermal nanomaterials is demonstrated to be critical to promote the solar-to-heat energy conversion and the following physical and chemical processes. This review introduces the latest photothermal nanomaterials and their nanostructure modulation strategies for environmental (seawater evaporation) and catalytic (C1 conversion) applications. We present the research progress of photothermal seawater evaporation based on two-dimensional and three-dimensional porous materials. Then, we describe the progress of photothermal catalysis based on layered double hydroxide derived nanostructures, hydroxylated indium oxide nanostructures, and metal plasmonic nanostructures. Finally, we present our insights concerning the future development of this field.

In Situ Three-Dimensional Welded Nanofibrous Membranes for Robust Membrane Distillation of Concentrated Seawater

Membrane distillation (MD) is a promising technology for treating the concentrated seawater discharged from the desalination process. Interconnected porous membranes, fabricated by additive manufacturing, have received significant attention for MD technology because of their excellent permeability. However, their poor hydrophobic durability induced by the deformation of pores constrains their water desalination performance. Herein, an in situ three-dimensional (3D) welding approach involving emulsion electrospinning is reported for fabricating robust nanofibrous membranes. The reported method is simple and effective for welding nanofibers at their intersections, and the reinforced membrane pores are uniform in the 3D space. The results show that the in situ 3D welded nanofibrous membrane, with a stability of 170 h and water recovery of 76.9%, exhibits better desalination performance than the nonwelded (superhydrophobic) nanofibrous membrane and the postwelded (superhydrophobic) nanofibrous membrane. Furthermore, the stability mechanism of the in situ 3D welded nanofibrous membrane and the two different wetting mechanisms of the nonwelded and postwelded nanofibrous membranes were investigated in the current work. More significantly, the in situ 3D welded nanofibrous membrane can further concentrate the actual concentrated seawater (121°E, 37°N) to crystallization, demonstrating its potential applications for the desalination of challenging concentrated seawater.