Liqian Wang

Bio: Liqian Wang is an academic researcher from Zhejiang University. The author has contributed to research in topics: Self-healing hydrogels & Business. The author has an hindex of 1, co-authored 2 publications receiving 15 citations.

Accelerating solar desalination in brine through ion activated hierarchically porous polyion complex hydrogels

Abstract: Solar-powered water desalination has been considered as one of the most promising solutions to alleviate clean water scarcity. In concentrated brine, the strong hydration ability of ions increases the required energy for water evaporation and thus lowers the desalination performances of most-existing solar vapor generators (SVGs). Here, a novel SVG is reported that exhibits superior desalination performance in brine than in pure water. This SVG is constructed by the complexation of oppositely charged polyelectrolytes into a hierarchically porous hydrogel (HPH), with interpenetrated polyaniline as efficient light absorbers. With controlled thermal management, the evaporation rate of this HPH-based SVG is 2.79 kg m−2 h−1 in simulated brine (3.5 wt% NaCl solutions) under one sun illumination, 67% higher than that in pure water (1.67 kg m−2 h−1) and more prominent than existing salt-resistant SVGs. Desalination tests with real seawater indicate that HPH is salt-resistant and sustainable for fast freshwater production. All-atom molecular dynamics simulations indicate that the unique interactions between the oppositely charged groups of the polyion complex and the mobile ions in brine can alter the water state, resulting in enhanced hydrability of the polymeric skeleton. This work provides a new approach for the development of next-generation SVGs with enhanced solar desalination performance.

Effect of water content on the physical properties and structure of walnut oleogels

Abstract: This study aimed to investigate the effect of water content on the properties and structure of oleogels by developing walnut oleogel based on potato starch and candelilla wax (CW). Physical, thermal, rheological and microstructure characteristics of the walnut oleogel were determined by texture analyzer, differential scanning calorimeter, rotary rheometer, X-ray diffractometer and optical microscope. Results showed that with increased water content, the hardness of the oleogel increased from 123.35 g to 158 g, whereas the oil loss rate decreased from 24.64% to 10.91%. However, these two values decreased slightly when the ratio of oil to water was 1 : 1. The prepared oleogels have a high elastic modulus, and the flow behavior of all walnut oleogels conformed to that of a non-flowing fluid. Microstructure observation indicated that the crystal size and quantity increased with an increase in water content, and the liquid oil was wrapped in the crystal network by CW and potato starch, forming solidified droplets to further promote gelation. In conclusion, when the ratio of oil to water is 39%, the oleogel has good physical properties and stable crystal structure. These findings can provide an indication of water content in the composition of oleogels.

Multi-responsive PNIPAM-PEGDA hydrogel composite.

Abstract: Hydrogels are widely used in applications such as soft robots and flexible sensors due to their sensitivity to environmental stimuli. It is highly demanded to develop multiple-responsive hydrogel structures. In this work, we employ the 3D printing technique to fabricate a PNIPAM–PEGDA hydrogel bilayer that can change shape through controlling the temperature, solvent mixture and magnetic field. The PNIPAM gel is a typical thermo-responsive gel, showing a decrease in swelling ratio with increasing temperature. Meanwhile, the PNIPAM gels also exhibit the cononsolvency effect in ethanol–water mixtures with a smaller swelling ratio in the mixture compared with that in each pure solvent. In comparison, the swelling ratio of PEGDA gels is insensitive to changes in both the temperature and solvent composition. Thus, the bilayer structure of PNIPAM–PEGDA can bend in different directions and with different angles with changing the temperature and solvent composition. Finally, Fe3O4 nanoparticles are incorporated into the matrix of PEGDA gels, endowing the whole structure with deformation and motion in response to an external magnetic field.

An integrated highly hydrated cellulose network with a synergistic photothermal effect for efficient solar-driven water evaporation and salt resistance

Abstract: Solar-driven water evaporation is an effective approach for using solar energy to purify seawater and wastewater. However, the high energy requirements of bulk water evaporation fundamentally restrict the practicality of solar freshwater production. Herein, we demonstrate an efficient hierarchical solar evaporator by combining polydopamine (PDA) and Ti3C2Tx MXene (MX) with a cellulose network skeleton of delignified wood (DW). By integrating activated water in a hydrated cellulose network and the synergistic photothermal effect between PDA and MX, the obtained PDMX@DW evaporator achieved a high evaporation rate of 2.08 kg m−2 h−1 and energy efficiency of 93.6% under 1 sun illumination. Differential scanning calorimetry and dark evaporation experiments indicated that the water in PDMX@DW exhibited a lower vaporization enthalpy (1915 J g−1) than bulk water (2440 J g−1). Raman spectral analysis and density functional theory calculations were used to investigate the structure of water molecules in the cellulose network, and it turns out that high contents of weakly hydrogen-bonded intermediate water were the most likely origin of the reduced vaporization enthalpy. More importantly, due to the interactive cellulose network structure and increased water supply rate, PDMX@DW exhibited excellent salt resistance and long-term stability in high-concentration brine. This work provides an effective method for breaking the evaporation limitation of the traditional wood-based evaporator and improving its salt resistance.

Metal- and halide-free, solid-state polymeric water vapor sorbents for efficient water-sorption-driven cooling and atmospheric water harvesting.

Abstract: Metal- and halide-free, solid-state water vapor sorbents are highly desirable for water-sorption-based applications, because most of the solid sorbents suffer from low water sorption capacity caused by their rigid porosity, while the liquid sorbents are limited by their fluidity and strong corrosivity, which is caused by the halide ions. Herein, we report a novel type of highly efficient and benign polymeric sorbent, which contains no metal or halide, and has an expandable solid state when wet. A group of sorbents are synthesized by polymerizing and crosslinking the metal-free quaternary ammonium monomers followed by an ion-exchange process to replace chloride anions with benign-anions, including acetate, oxalate, and citrate. They show significantly reduced corrosivity and improved water sorption capacity. Importantly, the water sorption capacity of the acetate paired hydrogel is among the best of the literature reported hygroscopic polymers in their pure form, even though the hydrogel is crosslinked. The hydrogel-based sorbents are further used for water-sorption-driven cooling and atmospheric water harvesting applications, which show improved coefficient of performance (COP) and high freshwater production rate, respectively. The results of this work would inspire more research interest in developing better water sorbents and potentially broaden the application horizon of water-sorption-based processes towards the water-energy nexus.