Designing a\xa0next generation solar crystallizer for real seawater brine treatment with zero liquid discharge

Chenlin Zhang,Le Shi,Yusuf Shi,Seunghyun Hong,Tiejun Zhang,Hongxia Li,Peng Wang,Sifei Zhuo,Renyuan Li

doi:10.1038/s41467-021-21124-4

Abstract

Proper disposal of industrial brine has been a critical environmental challenge. Zero liquid discharge (ZLD) brine treatment holds great promise to the brine disposal, but its application is limited by the intensive energy consumption of its crystallization process. Here we propose a new strategy that employs an advanced solar crystallizer coupled with a salt crystallization inhibitor to eliminate highly concentrated waste brine. The rationally designed solar crystallizer exhibited a high water evaporation rate of 2.42 kg m−2 h−1 under one sun illumination when treating real concentrated seawater reverse osmosis (SWRO) brine (21.6 wt%). The solar crystallizer array showed an even higher water evaporation rate of 48.0 kg m−2 per day in the outdoor field test, suggesting a great potential for practical application. The solar crystallizer design and the salt crystallization inhibition strategy proposed and confirmed in this work provide a low-cost and sustainable solution for industrial brine disposal with ZLD.

Highlights

Proper disposal of industrial brine has been a critical environmental challenge
As mentioned above, the water evaporation performances of the same solar crystallizer is totally different when it is used to treat pure NaCl brines and real seawater brines. In the former case, the water evaporation keeps stable for a long period of time, while it drops quickly in the latter case, which is ascribed to the huge difference in salt crust structures in the two cases
The dense salt crust surface layer along with the salt crystals filling inside the QGF membrane in the case of the concentrated seawater reverse osmosis (SWRO) brine leads to the failure of the 3D crystallizer during the long term operations

Summary

Introduction

Proper disposal of industrial brine has been a critical environmental challenge. Zero liquid discharge (ZLD) brine treatment holds great promise to the brine disposal, but its application is limited by the intensive energy consumption of its crystallization process. Most of the waste brines, especially brines produced in seawater desalination plants, are directly discharged into adjacent open water bodies, e.g., rivers, lakes, near shore seawater, and the rest are injected underground in deep wells or treated in evaporation ponds[7,8,9,10]. In 2018, a three dimensional (3D) cup-shaped solar evaporator which separated the light adsorption surface from the salt precipitation surface was reported This design enabled an unimpeded sunlight absorption and in turn a much higher and long-term stable water evaporation rate (e.g., 1.26 kg m−2 h−1) even at a near saturated brine (25 wt% NaCl brine)[38]. The direct ZLD desalination can be achieved by this advanced solar distillation but only with less than 35% energy efficiency for seawater

Methods

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Conclusion