Recently, the research group of Associate Professor Lv Fengyong from the School of Urban Construction and Safety Engineering published an online paper entitled “Polyanionic Electrolyte Ionization Desalination Empowers Continuous Solar Evaporation Performance” in Advanced Materials (IF=27.4, a high-profile international top journal in the field of materials science). The research paper is based on Shanghai Institute of Technology as the first unit. The research aims at the problem of salt crystal precipitation in the actual desalination process of solar evaporator, using polyanionic electrolyte functionalization strategy, excellent uniform desalting performance was achieved, proving that polyanionic electrolyte functionalization as a salt removal strategy has excellent benefits for the development of high-performance solar desalination technology and other technologies. Associate Professor Lv Fengyong is the first author of the paper, graduate students Miao Jie, Wang Zhongyu, Professor Hu Jing and Daniel Orejon from the University of Edinburgh are the corresponding authors of the paper.

Reasonable structural design is adopted to achieve efficient light absorption and water transport, different water transport strategies are used to regulate salt crystallization, Donnan balance is used to achieve salt ion regulation, and the Donnan effect is used in the polyanionic electrolyte layer. The fixed charged anion groups (such as -SO3- and COO-) can confine counter-ions (such as K+ and/or Na+) to the water supply path. First, after soaking in salt water, the sodium cation present in the polyanionic electrolyte polystyrene sulfonate-SO3NA is separated from polystyrene sulfonate-SO3 -. These charged polystyrene sulfonic acid anions create a high chemical potential in the outermost layer of the evaporator, which ultimately changes the balance of the distribution of salt ions between the main brine and the water supply pathway. Then, in addition to the Na+ cations already present in the main water, more Na+ cations are distributed along the polyanionic electrolyte polystyrene sulfonate around the evaporator skeleton, ultimately inhibiting the transport of Cl-anions, thereby inhibiting the crystallization of the salt, and achieving stable and efficient seawater desalination.

In view of the salt crystallization problem in the actual desalination process of solar evaporator, some researches use additional physical methods to desalt, or regulate the effect of salt crystallization area on the performance of the evaporator, but the long-term desalination performance is still poor. This research cleverly deposited polyanionic polyelectrolyte on the skeleton surface of SHiCF-GO inverted conical evaporator, and utilized Donnan to balance the transport of salt ions from the main water to the evaporation interface, so as to avoid salt crystallization in the desalination process. The stability of evaporation and salt removal in simulated seawater, real seawater and outdoor conditions was verified by systematic experiments. It provides a new way to realize seawater desalination simply and economically and maintain the stability of evaporation performance in the process.

Source: School of Urban Construction and Safety Engineering