ARTICLE IN PRESS
JID: JOBAB
[m3GeSsc;February 6, 2026;11:5]
Z. Wei, J. Liu, Y. Wang et al.
Journal of Bioresources and Bioproducts xxx (xxxx) xxx
functionality and durability ( Jing et al., 2021 ). Therefore, enhancing the water- and oil-proof properties of paper is a crucial step toward achieving the goal of substitution of plastic with paper. Coating technology is an important means to improve the water- and oil-proof properties and functionalization of paper ( Basak et al., 2024 ). Per- and polyfluoroalkyl substances (PFAS) coatings can significantly reduce the surface energy of paper, thereby producing paper-based materials with excellent water- and oil-proof properties. However, due to the bioaccumulation and toxicity of PFAS, they pose potential threats to the ecological environment and human health and have been gradually phased out ( Zabaleta et al., 2020 ; Neng et al., 2025 ). Currently, thermoplastic materials such as LDPE, which are non-renewable and difficult to biodegrade, are commonly used as coatings to impart water- and oil-proof properties to paper. These non-degradable coatings have significant draw- backs. First, they are difficult to separate effectively from the paper substrate, which severely limits the recycling and reuse of paper. Second, when waste paper-based materials coated with these substances are disposed of in landfills, the coatings do not naturally degrade, inevitably causing environmental pollution and ecological burdens ( Kansal et al., 2020 ). Therefore, developing environ- mentally friendly, non-toxic, easily separable, and scalable water- and oil-proof coatings has become a critical challenge. In recent years, paper coatings based on biodegradable materials such as polysaccharides, proteins, and polyvinyl alcohol (PVA) have garnered widespread attention due to their environmental friendliness and sustainability. These materials have been extensively applied to enhance the mechanical strength of paper, impart oil-proof properties, or introduce additional functionalities such as antibacterial properties ( Chi et al., 2020 ; Huang et al., 2023 ; Cheng et al., 2024 ; Li et al., 2024 ; de Amorim dos Santos et al., 2025 ). However, their high hydrophilicity often results in poor water-proof performance after coating, which limits their application in high-humidity environments or in fields requiring high barrier properties. To address the shortcomings in water- and oil-proof properties of pa- per treated with biodegradable coatings, current strategies mainly include hydrophobic modification of hydrophilic biodegradable polymers ( Hamdani et al., 2020 ; Tan et al., 2023 ; Fang et al., 2025 ), multilayer composite coating ( Kansal et al., 2020 ; Zhu et al., 2023 ), and emulsion coating ( Zhang et al., 2023 ; Peng et al., 2024 ). Emulsion coating technology presents a promising solution with significant advantages. This strategy cleverly combines oil-proof and water-proof components through emulsification, creating a stable aqueous dispersion system that simultaneously enhances both the water- and oil-proof properties of paper in a single coating process. This method not only avoids complex chemical modifications but also simplifies the coating procedure, aligning with the principles of green manufacturing. However, conventional emulsion coatings typically depend on synthetic surfactants to disperse and stabilize the oil phase. Although these systems avoid the use of organic solvents, the surfactants may introduce potential ecotoxicity, and the resulting emulsions often exhibit insufficient thermodynamic stability ( Cui et al., 2021 ). For example, cetyltrimethylammo- nium bromide (CTAB) is frequently used as a surfactant for alkyl ketene dimer (AKD) emulsions in industrial applications. While such emulsions can impart excellent hydrophobicity to paper, CTAB itself exhibits high biological toxicity ( Timmer et al., 2019 ). Therefore, developing alternative stabilizers that are efficient, non-toxic, and derived from renewable sources is essential for advanc- ing emulsion coating technologies. Pickering emulsion coating technology, stabilized by solid particles, particularly those derived from biomass-based nanomaterials, has emerged as a pivotal breakthrough in recent years, offering a novel pathway for creating high-performance and environmentally friendly coatings. The stabilization mechanism relies on the irreversible adsorption of solid particles at the oil-water interface, forming a dense barrier with high mechanical strength, which results in an emulsion system with exceptional stability. A Pickering emulsion coating was developed using cellulose nanocrystals (CNC) as the stabilizer, with chitosan and glutinous rice starch dissolved in the aqueous phase, while polylactic acid (PLA) was dissolved in dichloromethane to form the oil phase. This coating significantly enhanced the paper’s hydrophobicity and oil-proof properties. The PVA is a water-soluble synthetic polymer that is widely used due to its excellent film-forming ability, biocompatibility, and biodegradability. The molecular chains of PVA are rich in hydroxyl groups, which can form strong hydrogen bonds with the cellulose paper substrates, thereby providing good coating adhesion and a continuous, defect-free film structure. This makes PVA an ideal paper coating material that can significantly enhance the mechanical properties and oil-proof performance of paper ( Liu et al., 2022 ; Choe et al., 2024 ). However, paper coated with PVA exhibits poor water-proof performance, necessitating further modification or compounding with hydrophobic components to overcome this limitation ( Kwon et al., 2024 ). Stearic acid (SA), a long-chain saturated fatty acid, is regarded as an environmentally friendly hydrophobic material due to its biocompatibility, biodegradability, and renewa- bility ( Zhou et al., 2024 ). However, the hydrophobicity of stearic acid makes it difficult to achieve stable dispersion in water, and its compatibility with hydrophilic PVA is poor, thereby limiting the synergistic combination and practical application of both in aqueous systems. Lignin is the second most abundant natural polymer, primarily sourced from the black liquor of the paper industry, and is currently mostly utilized in low-value applications or directly incinerated. In recent years, with the development of nanotechnology, the high-value utilization of lignin has shown new prospects. Lignin nanoparticles (LNPs), prepared via nanonization, possess the characteristic advantages of nanomaterials, including small size and high specific surface area ( Yao et al., 2025 ). Furthermore, since lignin molecules contain both hydrophobic structures (such as phenyl rings and methoxy groups) and hydrophilic groups (such as hydroxyl and carboxyl groups), they can self-assemble into amphiphilic nanoparticles with high surface activity ( Gan et al., 2025 ). These characteristics make LNPs ideal emulsifiers for Pickering emulsions. To address the limitations of paper regarding water- and oil-proof properties, this study developed a ternary hybrid oil-in-water (O/W) PLS Pickering emulsion coating, composed of biodegradable PVA, biomass-derived SA and LNPs. Unlike the conventional LNPs-stabilized Pickering emulsions reported in previous studies, the PLS emulsion coating achieved a synergistic composition of hydrophilic PVA and hydrophobic SA. In this system, LNPs acted as emulsifiers, effectively reducing the interfacial tension and stabilizing the oil-water interface. The PVA, present in the continuous aqueous phase, imparted film-forming ability and oil-proof properties to the coating while also contributing to emulsion stability. Meanwhile, SA, as the hydrophobic oil phase, was uniformly dispersed as micrometer-sized droplets, providing essential hydrophobicity to the coating. When applied to the paper surface, the PLS emulsion coating formed a protective “armor ” layer that significantly enhanced the paper’s proof properties to water and oil, as well
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