Synergistic utilization of Vaccinium bracteatum Thunb. leaves for coupled solar evaporation and selective lithium extraction from seawater

Abstract

Solar-driven evaporation-adsorption for lithium extraction from seawater can improve the adsorption efficiency towards lithium ions, however, the fabrication of conventional solar-driven evaporation-adsorption materials often suffers from secondary pollution. To address these issues, this study developed a biomass-based evaporation-adsorption material PVV@VLJ-LIS by synergistically utilising multiple components of Vaccinium bracteatum Thunb. leaves, enabling the integrated coupling of interfacial evaporation and selective lithium adsorption. A freezing and salting out strategy was employed to crosslink a poly(vinyl alcohol) hydrogel and a VLJ-modified titanium-based lithium-ion sieve on the evaporator surface, thereby achieving in situ self-assembly between the organic components from the leaves and the lithium-ion sieve. VLJ endows PVV@VLJ-LIS with broadband photothermal absorption and antibacterial activity, and simultaneously promotes interfacial Li⁺ diffusion kinetics. Meanwhile, P-VLR serves as a porous supporting framework, facilitating the fixation of the lithium-ion sieve and water transport. Under 1 sun irradiation, the PVV@VLJ-LIS evaporator achieved a photothermal evaporation rate of 1.61 kg/(m²·h) with an evaporation efficiency of 80%. Under 40 °C, an initial Li⁺ concentration of 100 mg/L, and pH 12, PVV@VLJ-LIS achieved an equilibrium Li⁺ uptake of 17.472 mg/g. Relative to dark conditions, the adsorption capacity increased by 104.3%, which was attributed to the photothermally driven interfacial heating and the enhanced lithium-ion migration. In addition, the as-developed multifunctional evaporator exhibited pronounced antibacterial performance, anti-oil fouling, mechanical stability, and effective salt rejection, indicating the broad application prospects of PVV@VLJ-LIS for simultaneous lithium extraction and seawater desalination in complex seawater environments.

Graphical abstract

Keywords

Lithium extraction / Solar-driven interfacial evaporation / Lithium-ion sieve / Vaccinium bracteatum Thunb. Leaves / Photothermal-adsorption synergistic strategy

Highlight

	● Biomass-based evaporation–adsorption material developed by freezing and salting out.
	● The fabrication strategy enabled whole-component utilisation of natural biomass.
	● Synergistic utilisation of biomass components enhanced light and lithium adsorption.
	● PVV@VLJ-LIS showed favorable anti-oil fouling, high strength, stable salt rejection.

References

[1] Abdullah Z W , Dong Y . (2019). Biodegradable and water resistant poly(vinyl) alcohol (PVA)/starch (ST)/glycerol (GL)/halloysite nanotube (HNT) nanocomposite films for sustainable food packaging. Frontiers in Materials, 6: 58

[2] Al-Absi R S , Abu-Dieyeh M H , Ben-Hamadou R , Nasser M S , Al-Ghouti M A . (2022). Thermodynamics, isotherms, and mecha-nisms studies of lithium recovery from seawater desalination reverse osmosis brine using roasted and ferrocyanide modified date pits. Environmental Technology & Innovation, 25: 102148

[3] Boroumand Y , Razmjou A . (2024). Adsorption-type aluminium-based direct lithium extraction: the effect of heat, salinity and lithium content. Desalination, 577: 117406

[4] Chen C K , Liu X Y , Wang J T , Guo H R , Chen Y J , Wang N F . (2024a). Research on the thermal aging mechanism of polyvinyl alcohol hydrogel. Polymers, 16(17): 2486

[5] Chen Q , Chen Z J , Li H Q , Ni B J . (2024b). Advanced lithium ion-sieves for sustainable lithium recovery from brines. Sustainable Horizons, 9: 100093

[6] Chen Z N , Du J J , Shi J B . (2025). Mxene-based lithium-ion sieve polymer membrane for sustainable lithium adsorption. Separation and Purification Technology, 354: 129316

[7] Cisowska A , Wojnicz D , Hendrich A B . (2011). Anthocyanins as antimicrobial agents of natural plant origin. Natural Product Communications, 6(1): 149–156

[8] De Rossi L , Rocchetti G , Lucini L , Rebecchi A . (2025). Antimicrobial potential of polyphenols: mechanisms of action and microbial responses—a narrative review. Antioxidants, 14(2): 200

[9] Gou K J , Li T X , Zhang C Y , Wu D X , Zhu H T . (2024). Salting-out/sacrificial template strategy for the preparation of hydrogels as efficient solar evaporators. Chemical Engineering Journal, 480: 148210

[10] Hu H Q , Guo X S , Yang L M , Wu Y B , Yang G , Luo X B . (2025a). Adsorption materials toward highly-efficient lithium extraction from non-conventional lithium sources. Advanced Materials, 37(38): 2506055

[11] Hu H Q , Yang G , Chen C L , Guo X S , Xie Y H , Hou D C , Li X M , Fan W H , Yang L M , Luo X B . (2025b). Ultra−selective and capacious lithium extraction from geothermal brines via β−diketone functionalized brush−shaped polymer. Advanced Functional Materials, 35(50): e13012

[12] Huang C C . (2022). Design and characterization of a bioinspired polyvinyl alcohol matrix with structural foam-wall microarchitectures for potential tissue engineering applications. Polymers, 14(8): 1585

[13] Jeyaraj E J , Vidana Gamage G C , Cintrat J C , Choo W S . (2023). Acylated and non-acylated anthocyanins as antibacterial and antibiofilm agents. Discover Food, 3(1): 21

[14] Kanagasundaram T , Murphy O , Haji M N , Wilson J J . (2024). The recovery and separation of lithium by using solvent extraction methods. Coordination Chemistry Reviews, 509: 215727

[15] Liu C , Yin Z H , Hou Y , Yin C R , Yin Z X . (2023). Overview of solar steam devices from materials and structures. Polymers, 15(12): 2742

[16] Ma J Q S , Sun X H , Liu Y , Wang L W , An M , Kim M , Yamauchi Y , Khaorapapong N , Yuan Z H . (2025). Bio-inspired 3D architectured aerogel evaporator for highly efficient solar seawater desalination. Nano Energy, 137: 110781

[17] Maggay I V , Chiu Y T , Lin H T , Venault A , Chang Y . (2025). Engineering bio-inert and thermostable poly(vinylidene difluoride) membranes by grafting thermal-tolerant copolymers via ring-opening reaction. Journal of Membrane Science Letters, 5(1): 100088

[18] Mojid M R , Lee K J , You J H . (2024). A review on advances in direct lithium extraction from continental brines: ion-sieve adsorption and electrochemical methods for varied Mg/Li ratios. Sustainable Materials and Technologies, 40: e00923

[19] Park J , Lee J , Shim I T , Kim E , Nam S H , Koo J W , Hwang T M . (2025). Electrochemical direct lithium extraction: a review of electrodialysis and capacitive deionization technologies. Resources, 14(2): 27

[20] Pruna A , Cárcel A C , Benedito A , Giménez E . (2019). Effect of synthesis conditions on CO₂ capture of ethylenediamine-modified graphene aerogels. Applied Surface Science, 487: 228–235

[21] Qi W D , Qi W X , Xiong D W , Long M . (2022). Quercetin: its antioxidant mechanism, antibacterial properties and potential application in prevention and control of toxipathy. Molecules, 27(19): 6545

[22] Qian C , Zheng M P , Zhang Y S , Xing E Y , Gui B L . (2023). Adsorption performance and mechanism of Li⁺ from brines using lithium/aluminum layered double hydroxides-SiO₂ bauxite composite adsorbents. Frontiers in Chemistry, 11: 1265290

[23] Qiu Z M , Zhang Y H , Lv X W , Dang J . (2025). High-capacity biomass-based composite aerogel for efficient multi-ion adsorption of vanadium, molybdenum, and nickel. Separation and Purification Technology, 368: 132990

[24] Reggio C , Barberi J , Ferraris S , Spriano S . (2023). Functionalization of Ti₆Al₄V alloy with polyphenols: the role of the titanium surface features and the addition of calcium ions on the adsorption mechanism. Metals, 13(8): 1347

[25] Toyoda M , Inagaki M . (2023). Carbon materials for solar steam-generation. Carbon, 214: 118373

[26] Wu X , Zhang H C , Zhang X Y , Guan Q , Tang X C , Wu H , Feng M B , Wang H T , Ou R W . (2024). Sustainable lithium extraction enabled by responsive metal-organic frameworks with ion-sieving adsorption effects. Proceedings of the National Academy of Sciences of the United States of America, 121(6): e2309852121

[27] Xiao C C , Yan L Q , Gao H P , Dou Z O , Xie X , Chen Y S . (2024). Selective separation and recovery of Co(II) and Ni(II) from lithium-ion battery using Cyanex 272 adsorptive membrane. Frontiers of Environmental Science & Engineering, 18(12): 148

[28] Xie Y J , Cai P X , Cao X F , Pan Y F . (2024). High-strength, water-resistant polyvinyl alcohol films reinforced with regenerated cellulose fibers for food packaging. Industrial Crops and Products, 207: 117768

[29] Xu Q X , Shi J J , Zhang J G , Li L , Jiang L , Wei Z J . (2016). Thermal, emulsifying and rheological properties of polysaccharides sequentially extracted from Vaccinium bracteatum thunb leaves. International Journal of Biological Macromolecules, 93: 1240–1252

[30] Yang Y , Fu Z , Zhang Q . (2024). Solar evaporation for simultaneous oil-water separation and electricity generation with Janus wood-based absorbers. Frontiers of Environmental Science & Engineering, 18(2): 15

[31] Yersaiynova A A , Karshyga Z B , Kenzhaliyev B K , Sukurov B M , Yessengaziyev A M , Orynbayev B M , Saulebekkyzy S . (2025). Adsorption equilibrium of lithium sorption process using synthesized inorganic sorbents. Results in Engineering, 27: 106720

[32] Yong M , Yang Y , Sun L L , Tang M , Wang Z Y , Xing C , Hou J W , Zheng M , Chui T F M , Li Z K . et al. (2025). Nanofiltration membranes for efficient lithium extraction from salt-lake brine: a critical review. ACS Environmental Au, 5(1): 12–34

[33] Zhang J F , Wenzel M , Yang L R , Luckay R C , Weigand J J . (2023a). Receptors for the recognition and extraction of lithium. Frontiers in Chemical Engineering, 5: 1271045

[34] Zhang S C , Li S Y , Wang X Y , Li C C , Liu Y X , Cheng H , Mao S L , Wu Q , Shen Z Y , Mao J L . et al. (2023b). Nonflammable electrolyte with low exothermic design for safer lithium-based batteries. Nano Energy, 114: 108639

[35] Zhang X S , Wu J X , He Y , Zhao C H , An M F , Li L B . (2024). Porous polyvinyl alcohol/polyacrylamide hydrogels loaded with HTO lithium-ion sieves for highly rapid and efficient Li⁺ extraction. Desalination, 580: 117587

[36] Zheng Y , Chen L , Liu Y H , Shi L , Wan S P , Wang L . (2019). Evaluation of antimicrobial activity of water-soluble flavonoids extract from Vaccinium bracteatum thunb. leaves. Food Science and Biotechnology, 28(6): 1853–1859

[37] Zhou J Y , Li X K , Xie W , Chen Q , Jiang Y G , Wu X H , Yang L . (2024). Realizing efficient solar evaporation and rapid lithium sorption by the halloysite nanotubes-based hydrogel. Journal of Cleaner Production, 437: 140523

[38] Zhu Z Z , Sun X D , Jiang Y H , Tian Q , Yue X J , Zhang T , Qiu F X . (2025). Facile fabrication of bilayer photothermal melamine sponge for efficient lithium extraction. Separation and Purification Technology, 360: 130941

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