High‐Yield and Low‐Cost Solar Water Purification via Hydrogel‐Based Membrane Distillation

Abstract

As an eco‐friendly means, solar water purification has attracted substantial research interest regarding material design, system engineering, and energy management. However, the low water yield and relatively high cost essentially restrict its practical potential. Here, a hydrogel‐based ultrathin membrane (HUM) is developed to synergistically coordinate facilitated vapor transfer and environmental energy harvesting for solar‐driven membrane distillation. The evaporation front is directly exposed to an airflow, which fundamentally eliminates the temperature polarization induced energy consumption. As such, the humidity of the output flow is significantly increased, and thus the vapor collection ratio rises to over 80% to achieve a high water yield of 2.4 kg m–2 h–1 under one sun without any energy recycling and cooling accessories. The HUM with a raw material cost of $0.36 m–2 offers a competitive potential cost of freshwater production of about $0.3–1.0 m–3. This work demonstrates a promising membrane distillation strategy based on sustainable energy toward both decentralized water purification and large‐scale water treatment.

Recent developments of hydrogel based solar water purification technology

“…It is reported that the carbon black can be treated by a concentrated HNO3 solution to improve its hydrophilicity and the dispersibility in water. 96 Considering the simple processing method and low cost of HNO3, the carbon black can be arguably considered a low-cost material. Combing with a reasonable light path and design, the evaporation rate of these materials can reach 3.86 kg m -2 h -1 , and the energy conversion efficiency is as high as 92%.…”

“…Carbon-based materials have been used as solar absorbers in various studies in recent years, owing to their excellent light absorption over a broad spectrum, ease of preparation, abundance and low cost. Carbon-based materials include activated carbon, 83–86 polymer 76,87–90 or biomass 82,91–95 derived carbide, carbon black 96–101 and various amorphous carbon materials and highly graphitized carbon materials, such as graphene, 56,59,63,74,77,102–122 carbon nanotubes (CNTs) 27,123–130 and their derivatives.…”

“…144 Other studies have reported the use of specific solid waste as solar absorbers, including red mud (residue of the aluminum mining industry), 180 semi-coke, 183 and pencil graphite. 178 Besides, reducing the use of solar absorbers by distributing them only around the evaporation interface 35,148 and constructing multilayer-structure with only one layer of them 73,75,83,96,100,141 is also effective. Moreover, designing a recyclable solar water purification platform 27,105 is another proven solution.…”

Estado del arte. Métodos de desalinización de agua

“…Consiste en pasar una corriente salina caliente y una corriente de agua fría desalinizada separadas por una membrana porosa y aprovechar la diferencia en las presiones de vapor para lograr que las moléculas de vapor de agua pasen de la corriente de agua salada hacia el lado del agua pura [51,52,53,54,55,56]. La membrana es de naturaleza hidrofóbica y debido al tamaño de los poros, ni el agua líquida ni las sales pueden atravesarla.…”

All‐in‐One Solar Interfacial Evaporation System with Highly Effective Heat Management and Water Collection

“…[ 8 ] Although the collection installations much larger than the evaporation area and with auxiliary facilities (e.g., airflow assistances, extra condensers) are able to reduce local humidity for a closed system, high capital, and operating costs will be involved, restricting their industrial applications considerably. [ 9–12 ]…”