A hierarchical salt-rejection strategy for sustainable and high-efficiency solar-driven desalination

Zhengyi Mao; Xuliang Chen; Yingxian Chen; Junda Shen; Jianpan Huang; Yuhan Chen; Xiaoguang Duan; Yicheng Han; Kannie Wai Yan Chan; Jian LU

doi:10.1016/j.nanoms.2023.08.003

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Research Article | Open Access

A hierarchical salt-rejection strategy for sustainable and high-efficiency solar-driven desalination

Zhengyi Mao^{^a^,^b}, Xuliang Chen^{^b}, Yingxian Chen^{^c}, Junda Shen^{^c}, Jianpan Huang^{^d}, Yuhan Chen^{^b}, Xiaoguang Duan^{^e}, Yicheng Han^{^b}, Kannie Wai Yan Chan^{^d}, Jian LU^{^a^,^b^,^f^,^g}()

CityU-Shenzhen Futian Research Institute, Shenzhen, 518045, China

Department of Mechanical Engineering, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong, China

Department of Material Science and Engineering, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong, China

Department of Biomedical Engineering, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong, China

School of Chemical Engineering and Advanced Materials, The University of Adelaide, Adelaide, Australia

Hong Kong Branch of National Precious Metals Material Engineering Research Centre, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong, China

Centre for Advanced Structural Materials, City University of Hong Kong Shenzhen Research Institute, Greater Bay Joint Division, Shenyang National Laboratory for Materials Science, Shenzhen, 518057, China

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Abstract

Solar steam generation (SSG) is widely regarded as one of the most sustainable technologies for seawater desalination. However, salt fouling severely compromises the evaporation performance and lifetime of evaporators, limiting their practical applications. Herein, we propose a hierarchical salt-rejection (HSR) strategy to prevent salt precipitation during long-term evaporation while maintaining a rapid evaporation rate, even in high-salinity brine. The salt diffusion process is segmented into three steps—insulation, branching diffusion, and arterial transport—that significantly enhance the salt-resistance properties of the evaporator. Moreover, the HSR strategy overcomes the tradeoff between salt resistance and evaporation rate. Consequently, a high evaporation rate of 2.84 kg m⁻² h⁻¹, stable evaporation for 7 days cyclic tests in 20 wt% NaCl solution, and continuous operation for 170 h in natural seawater under 1 sun illumination were achieved. Compared with control evaporators, the HSR evaporator exhibited a > 54% enhancement in total water evaporation mass during 24 h continuous evaporation in 20 wt% salt water. Furthermore, a water collection device equipped with the HSR evaporator realized a high water purification rate (1.1 kg m⁻² h⁻¹), highlighting its potential for agricultural applications.

Keywords

Solar water evaporation 3D printing Salt-rejection Hierarchical structures High efficiency

References

[1]

A. Boretti, L. Rosa, npj Clean Water 2 (2019) 15.