Stable and Salt-Resistant Janus Evaporator Based on Cellulose Composite Aerogels from Waste Cotton Fabric

Abstract

Solar steam generation has been considered a promising approach for using renewable solar energy to produce clean water from seawater and wastewater. It shows great potential for alleviating water shortages. However, salt accumulation and system longevity are challenges which impede the widespread use of evaporators. This paper reports a stable Janus evaporator with thickness controllable hydrophilic and hydrophobic layers based on cellulose composite aerogels, which were extracted from waste cotton fabric by a two-step freeze-drying process. The obtained glutaraldehyde cross-linked carbon nanotubes/cellulose Janus aerogel exhibited an attractive solar steam generation rate of 1.81 kg·m–2·h–1 and a light-to-vapor efficiency of up to 92.5% in 1 sun illumination. Moreover, the Janus solar steam generator could pledge stable and sustainable solar-driven water evaporation performance within a 10 h test, showing a high salt-resistant property in simulated seawater. In addition, the developed solar evaporator also had a good purification effect on dye wastewater. These findings suggest its potential ability for seawater desalination and wastewater purification.

Natural Cellulose Fiber-Derived Photothermal Aerogel for Efficient and Sustainable Solar Desalination

“…The morphologies of the SBF aerogel and the SBFAP material as well as their internal microstructures were investigated with an SEM system. The surface structure of the SBF aerogel was observed as shown in Figure a–c, which exhibited that the material has 3D interconnected pore structures with a pore size from 20 to 100 μm and a pore wall thickness of less than 1 μm. , As a result, the aerogel had a low density (0.0495 g/cm 3 ) and a high porosity (96.7%), which is predicted in Note S1. , The specific surface area of the SBFAP material was 17.3 m 2 /g, which was comparable to those of the reported aerogel materials. Thus, there were main factors that reduced the thermal conductivity of the SBF aerogels. , The surface morphologies of the SBFAP aerogel were observed as shown in Figure d–f.…”

“…Substrates, such as metallic nanoparticles, semiconductors, polymers, carbon-based materials, and biomass, have been widely used for the fabrication of photothermal materials with various morphologies (e.g., 2D, 3D interconnected porous, hierarchical, conical structures, etc. ). , Consequently, the water evaporation performance of the SSG could reach approximately 2–4 kg m –2 h –1 , with an energy utilization efficiency of 100% for a relatively 3D-structural photothermal material. , However, the practical application of 3D-structural photothermal materials is still restricted due to their high fabrication cost and low structural stability during preservation and transportation. − Thus, future work is still needed to address these challenges.…”

“…Recently, aerogels, as potential substrate materials for the preparation of photothermal materials, have attracted much attention. − This is because aerogels possess many favorable properties, namely (1) 3D interconnected porous structure with a large specific surface area that increases the water transportation ability, (2) high porosity and low density that reduce the thermal conductivity, (3) simple fabrication method, in which freeze drying is a significant step, , and (4) numerous hydroxyl groups that help reduce the enthalpy of water evaporation. , The aerogels used to fabricate photothermal materials were first proposed by combining a bacterial cellulose biomaterial with a graphene oxide layer . Till date, various aerogels have been used as substrates for photothermal material production.…”

“…Besides, the aerogel-based photothermal materials demonstrate an excellent self-cleaning property. Consequently, salt crystals, deposited on the material surface during seawater desalination, can be quickly dissolved. , Nevertheless, since the crosslinking of hydrogens or Si-O-C forms aerogels, the structural stability in seawater usually is poor, limiting the practical application. , Besides, to improve the light absorption ability of photothermal materials, costly materials (e.g., PPy, PDA, PEDOT:PSS, CNT, etc.) were used, leading to an increased fabrication cost. , Therefore, it is crucial to fabricate an aerogel-based photothermal material with excellent structural stability and efficient water evaporation using a simple and low-cost procedure …”

“…37 The biomass materials and natural celluloses, extracted from waste cotton fabrics, were utilized in the fabrication of photothermal materials in an attempt to reduce their fabrication costs while enhancing their structural stability. 24,38,39 The agar hydrogel (AHG), which was derived from natural algae, was used to prepare a photothermal material by immobilizing Prussian blue nanoparticles on a cellulose nanofiber (CNF-PB). 38 With the salt rejection ability of the AHG, the photothermal material exhibited a stable performance under long-term seawater desalination.…”