Recently, the team led by Professor Song Jitian and Professor Xu Qing from the School of Mechanical Engineering of our university published a research paper titled "Strategy for Regulating Hydrogel Pore Size through Ultrasound-Assisted Directional Freezing for Enhanced Interfacial Evaporation" inChemical Engineering Journal—a TOP journal in the field of engineering technology. Professor Song Jitian’s research group has long focused on the research and development of thermal evaporation concentration technologies and equipment for liquid food and biological materials. Based on the group’s previous research, this study has achieved an innovative breakthrough in combining thermal evaporation and photothermal evaporation, providing new technical ideas and solutions for the evaporation concentration process of liquid food and showing broad application prospects. Professor Song Jitian from the School of Mechanical Engineering is the corresponding author, and Tianjin University of Science and Technology is the first author’s affiliation.

A 2021 report by the World Meteorological Organization (WMO) pointed out that more than 2 billion people worldwide face insufficient access to clean water, and this number is expected to surge to nearly 5 billion by 2050. Solar-driven interfacial evaporation (SDIE) technology has become a research focus in the field of water treatment due to its advantages of low carbon emissions, environmental friendliness and sustainability.

This study adopted ultrasound-assisted directional freezing technology to achieve precise regulation of the hydrogel pore structure by interfering with the nucleation and growth process of ice crystals. During the directional freezing process, the introduction of ultrasound significantly refined the ice crystal size and reduced the pore size distribution, thereby optimizing the evaporation performance of the hydrogel. The research found that the increase in ultrasound power leads to a gradual decrease in hydrogel pore size and a gradual increase in pore density, which provides a new method for preparing hydrogels with specific pore sizes and pore densities.

The hydrogel prepared by ultrasound-assisted directional freezing exhibits excellent evaporation performance under solar drive. Under one sun intensity, the evaporation rate reaches up to 3.85 kg/m²/h, with an evaporation efficiency of 92%. Even under high salinity conditions of 20%, the hydrogel evaporator can operate stably, with the evaporation rate increased by 23%.

The publication of this research achievement provides new ideas and directions for the application and development of photothermal evaporation technology. It is expected to be further promoted to fields such as liquid food concentration and industrial saline wastewater treatment, with broad application prospects and applicable scenarios.