Advanced Materials: New Fabrics Realize Efficient And Continuous Evaporation Of Seawater

Chen Zhigang, a researcher from Donghua University, has designed a new bionic photothermal fabric, which realizes efficient and continuous evaporation of seawater, opens a new perspective for large-scale design of two-dimensional flexible photothermal film and industrial application of solar driven seawater desalination, and provides assistance in coping with the global freshwater resource crisis. Relevant research results were recently published in Advanced Materials.

The core of solar desalination is photothermal materials and evaporation devices. The existing photothermal materials mainly include three-dimensional structural materials and two-dimensional films, both of which have advantages, but at the same time, there are some problems that limit the practical application.

Inspired by the leaf structure and transpiration, the research team used a single commercial polyester (PET) fiber as raw material, constructed it into a two-dimensional PET fabric with a typical three-layer structure through knitting technology, and further modified it to obtain a leaf like photothermal fabric CPP-H. The experimental results show that the sunlight absorption rate of CPP-H fabric is significantly increased to 96.1%, showing low heat loss and excellent photothermal conversion performance, while reducing the enthalpy of evaporation and improving the evaporation efficiency.

On this basis, the researchers hung the CPP-H fabric between the high sea trough and the low altitude trough obliquely and assembled it into a light oriented inclined evaporator, which realized the transmission of seawater from the high sea trough to the low altitude trough. Under the sunlight, the fabric absorbs the sunlight and converts it into heat, which promotes the simultaneous evaporation of seawater on the top and bottom surfaces of the top layer and on the top and bottom surfaces of the bottom layer.

The evaporation model of CPP-H fabric simulates the transpiration process of plant leaves. After evaporation, the remaining seawater is concentrated into brine and dripped to the low level collecting tank, so as to effectively avoid salt crystallization accumulation in the evaporator. The experimental results show that the performance of the three-layer photothermal fabric is better than that of the traditional floating model based on similar materials, the single-layer fabric suspension model or the three-layer fabric.

Chen Zhigang said that in the future, the team will further explore the influence of the composition and micro nano structure of the photothermal fabric on the light absorption, photothermal conversion and evaporation process, further optimize the evaporation rate and reduce the cost of freshwater production, in order to lay the foundation for the industrialization of solar desalination and help build a green system of freshwater supply.