ECO-friendly chitosan-based nanocomposite films with multi functional nanoparticles for atmospheric water generation and purification

Abstract

Disclosed herein is a method for producing a chitosan-based nanocomposite film, the method comprising steps of synthesizing one or more nanoparticles from precursors of one or more metal oxides by utilizing plant-based extracts and agricultural waste, mixing precursors of one or more metal oxide at predetermined concentration and pH level to obtain a nanocomposite mixture, dissolving chitosan in an acetic acid solution, embedding the nanoparticles into a chitosan matrix, cross-linking the nanoparticles with the chitosan matrix and extending the nanocomposite mixture to form a multi-layered film.

Description

[0001] ECO-FRIENDLY CHITOSAN-BASED NANOCOMPOSITE FILMS WITH MULTI FUNCTIONAL NANOPARTICLES FOR ATMOSPHERIC WATER GENERATION AND PURIFICATION

[0002] TECHNICAL FIELD

[0003]

[0001] The present invention pertains broadly to the fields of nanotechnology, environmental engineering, materials science, and water resource management. More particularly, it relates to development of biodegradable, nanocomposite films for atmospheric water harvesting and purification.

[0004] BACKGROUND OF THE INVENTION

[0005]

[0002] Water scarcity and contamination are critical global challenges, driving the need for innovative, sustainable solutions. Atmospheric Water Harvesting (AWH) has emerged as a viable option, especially in arid regions where conventional water sources are scarce. Recent advancements in AWH technologies have aimed to capture atmospheric moisture and convert it into usable water. However, many existing technologies, such as metal-organic frameworks (MOFs) and super hygroscopic polymer films (SHPFs), face limitations in terms of scalability, energy efficiency, and environmental impact. MOFs, for instance, have demonstrated the ability to capture water even in low-humidity conditions but require energy-intensive regeneration and involve complex, resource-intensive production processes. Moreover, some MOFs raise toxicity concerns due to the use of heavy metals, restricting their practical application in potable water system.

[0006]

[0003] The development of Nanostructured Moisture-Absorbing Gels (N-MAGs) has provided an alternative with greater sustainability, as these gels leverage hydrophilic biopolymer networks functionalized with hygroscopic salts. N-MAGs excel in high-humidity environments and passively absorb moisture without requiring external energy. However, their performance is limited in low-humidity conditions, and they require periodic regeneration, typically through heating. This added energy demand reduces the suitability of N-MAGs in off-grid or low-resource applications, especially in extremely dry climates. The need for substantial amounts of hygroscopic salts also presents scalability challenges. Although promising in concept, these materials fall short of offering a universal solution for AWH, highlighting the need for materials that combine high moisture absorption rates, energy efficiency, and environmental sustainability.

[0004] Super Hygroscopic Polymer Films (SHPFs) represent another approach, particularly for arid climates with relative humidity (RH) below 30%. SHPFs, derived from renewable biomasses, integrate hygroscopic salts within a porous structure that enables efficient water vapor uptake. These films show impressive water uptake rates in controlled low-humidity environments, yet their performance diminishes significantly as humidity levels decrease further. Additionally, issues with salt crystallization and material degradation over repeated cycles remain unresolved, which limits their long-term application. While these films are relatively easy to produce at scale, their reliance on hygroscopic salts and limited performance in very low humidity conditions reveal significant limitations. Therefore, a more stable and adaptable material is necessary to overcome these constraints in a broader range of climate.

[0007]

[0005] Another advancement in AWH technologies is the use of hygroscopic hydrogels, which have high water sorption capacities and are generally more scalable than MOFs and SHPFs. These hydrogels can efficiently absorb and release water through sorption-desorption cycles and incorporate both vapor and liquid transport mechanisms, optimizing water capture. However, their effectiveness is highly dependent on environmental conditions; performance declines in extremely dry environments.

[0008]

[0006] Therefore, to address these challenges, this invention presents a biodegradable chitosan- based film embedded with hydrophilic and hydrophobic nanoparticles, providing a more sustainable, low-cost, and scalable solution for passive water harvesting and purification. This innovation effectively combines water adsorption efficiency, structural stability, and environmental compatibility, outperforming traditional materials in versatility and practical applicability.

[0009] SUMMARY OF THE INVENTION

[0010]

[0007] Embodiments of the present disclosure present technological improvements as solutions to one or more of the above-mentioned technical problems recognized by the inventor in conventional solutions.

[0011]

[0008] According to a first aspect of the present invention there is provided a method for producing a chitosan-based nanocomposite film, the method comprising steps of: synthesizing (102) one or more nanoparticles from precursors of one or more metal oxides by utilizing plantbased extracts and agricultural waste; mixing (104) precursors of one or more metal oxide at predetermined concentration and pH level to obtain a nanocomposite mixture; dissolving (106) chitosan in an acetic acid solution followed by ionic gelation to obtain one or more chitosan nanoparticles; embedding (108) the nanoparticles into a chitosan matrix, cross-linking (110) the nanoparticles with the chitosan matrix using a cross-linking agent and extending (112) the nanocomposite mixture to form a multi-layered film.

[0012]

[0009] In accordance with an embodiment of the present invention, the nanoparticles include iron oxide (FexOy), zinc oxide (ZnO), silica (SiCE), and FeZnSi nanocomposites.

[0013]

[0010] In accordance with an embodiment of the present invention, the precursors of metal oxides include iron chloride salts such as ferric chloride (FeCE) or ferrous chloride (FeCE), zinc salts, including zinc chloride (ZnCE), zinc sulfate monohydrate (ZnSCE FEO), zinc acetate dihydrate (Zn(CHsCOO)2 2ILO), and zinc nitrate hexahydrate (Zn(NOs)2 6H2O), tetraethyl orthosilicate (TEOS), and chitosan.

[0014]

[0011] In accordance with an embodiment of the present invention, precursors of metal oxides are mixed at predetermined concentration of 1 M for all precursors and pH level 7.5.

[0015]

[0012] In accordance with an embodiment of the present invention, plant-based extracts and agricultural waste include banana peel, peanut shells, phoenix dactylifera L. and other agricultural byproducts.

[0016]

[0013] In accordance with an embodiment of the present invention, to obtain a nanocomposite mixture Phoenix dactylifera L. (date palm) extract is utilized as a reducing, stabilizing, and capping agent.

[0017]

[0014] In accordance with an embodiment of the present invention, sodium tripolyphosphate (TPP) is used in ionic gelation.

[0018]

[0015] In accordance with an embodiment of the present invention, the chitosan matrix is crosslinked with polyethylene glycol (PEG) solution.

[0019]

[0016] In accordance with an embodiment of the present invention, the kinetic diameters of the multilayered film is less than 0.5 nm, specifically reaching 0.3 nm.

[0020]

[0017] According to a second aspect of the present invention, chitosan-based nanocomposite film, the film comprising a predetermined quantity of hydrophilic and hydrophobic nanoparticles; and one or more plant-based extracts and agricultural waste.

[0018] In accordance with an embodiment of the present invention, the plant-based extracts include banana peel, peanut shells, phoenix dactylifera L. and agricultural waste.

[0021] BRIEF DESCRIPTION OF DRAWINGS

[0022]

[0019] So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may have been referred by embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

[0023]

[0020] These and other features, benefits, and advantages of the present invention will become apparent by reference to the following text figure, with like reference numbers referring to like structures across the views, wherein:

[0024] FIG. 1 illustrates a method for producing a chitosan-based nanocomposite film, in accordance with an embodiment of the present invention;

[0025] FIG. 1A illustrates SEM (Scanning Electron Microscope) images illustrate the mixture of iron oxide and ZnFe2O4 nanoparticles, demonstrating uniform morphology critical for integration into the chitosan matrix, according to the embodiment of present invention;

[0026] FIG. 2 illustrates SEM images demonstrate uniform morphology of the ZnO nanoparticles, crucial for their incorporation into the chitosan matrix, according to the embodiment of present invention;

[0027] FIG. 3 illustrates SEM images show silica nanoparticle morphology produced using green methods, confirming uniform structure critical for incorporation into the films, according to the embodiment of present invention;

[0028] FIG. 4 illustrates SEM images demonstrate the uniform dispersion of FeZnSi NC, critical for maintaining film integrity and water adsorption capacity, according to the embodiment of present invention;

[0029] FIG. 5 illustrates chitosan nanoparticles synthesized using green methods demonstrate uniform morphology, critical for their integration into the chitosan matrix, according to the embodiment of present invention; FIG. 6 illustrates SEM and confocal microscopy images illustrate the uniform integration and well-dispersed nanomaterials, which reduce pore size and enhance surface roughness, improving adsorption efficiency in multi-layered films, according to the embodiment of present invention;

[0030] FIG. 7 illustrates mechanical properties (e.g., tensile strength, durability) are shown in graphs, indicating enhancements in strength and resilience over multiple cycle, according to the embodiment of present invention;

[0031] FIG. 8 illustrates the cone-shaped design’s increased water collection area compared to flat film, according to the embodiment of present invention;

[0032] FIG. 9 illustrates the improved hydrophilicity of the films, evidenced by the reduced contact angle as shown in enhances water adsorption, according to the embodiment of present invention;

[0033] FIG. 10 illustrates water droplet formation inside the Eppendorf tube and water generation on the film's surface during tests confirm the film's ability to passively autogenerate water, according to the embodiment of present invention; and

[0034] FIG. 11 illustrates the antimicrobial efficacy of the films highlights the superior protection provided by ZnO nanoparticles and FeZnSi NC compared to chitosan-only films, which developed mold within one week, whereas the nanoparticle-embedded films remained free from contamination, according to the embodiment of present invention.

[0035] DETAILED DESCRIPTION OF EMBODIMENTS

[0036]

[0021] The present invention is described hereinafter by various embodiments with reference to the accompanying drawing, wherein reference numerals used in the accompanying drawing correspond to the like elements throughout the description.

[0037]

[0022] While the present invention is described herein by way of example using embodiments and illustrative drawings, those skilled in the art will recognize that the invention is not limited to the embodiments of drawing or drawings described and are not intended to represent the scale of the various components. Further, some components that may form a part of the invention may not be illustrated in certain figures, for ease of illustration, and such omissions do not limit the embodiments outlined in any way. It should be understood that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the scope of the present invention as defined by the appended claim. As used throughout this description, the word "may" is used in a permissive sense (i.e., meaning having the potential to), rather than the mandatory sense, (i.e., meaning must). Further, the words "a" or "an" mean "at least one” and the word “plurality” means “one or more” unless otherwise mentioned. Furthermore, the terminology and phraseology used herein is solely used for descriptive purposes and should not be construed as limiting in scope. Language such as "including," "comprising," "having," "containing," or "involving," and variations thereof, is intended to be broad and encompass the subject matter listed thereafter, equivalents, and additional subject matter not recited, and is not intended to exclude other additives, components, integers, or steps. Likewise, the term "comprising" is considered synonymous with the terms "including" or "containing" for applicable legal purposes.

[0038]

[0023] Further, the various embodiments described herein below include specific method steps in an exemplary order but a wide variety of other such method steps could be implemented within the scope of the invention, including additional steps, omission of some steps, or performing the method in a different order.

[0039]

[0024] According to an embodiment of the present invention, the present invention offers a biodegradable and eco-friendly solution for atmospheric water adsorption and purification, leveraging chitosan-based films embedded with hydrophilic and hydrophobic nanoparticles synthesized through green methods. Designed to capture and retain atmospheric water even in low-humidity environments, the films present an energy-efficient, scalable option for water harvesting. The chitosan base, a naturally biodegradable polysaccharide, provides structural integrity, while the embedded nanoparticles, produced using plant extracts and agricultural waste, contribute both hydrophilic and antimicrobial properties. This green synthesis approach ensures uniform nanoparticle size and dispersion, maximizing water adsorption and preventing bacterial contamination. The fdm’s multi-layered structure further enhances its functionality; for example, a layer embedded with ZnO nanoparticles promotes antimicrobial activity, while another containing FeZnSi nanocomposites improves water retention and structural stability, enabling a passive cycle of moisture capture and release.

[0040]

[0025] To optimize water harvesting, the invention also includes a water collection device adaptable to the shape and properties of the fdm. The device’s cone-shaped design maximizes the fdm’s surface area exposed to the air, thereby increasing moisture capture. This shape naturally directs water droplets downward into a central collection reservoir, using gravity to enhance collection efficiency without needing external energy input. By maintaining close contact between the film and ambient air, the device creates a microenvironment that accelerates condensation, facilitating continuous water flow into the reservoir. This passive and adaptable system makes the invention particularly suitable for off-grid or resource-limited settings, where clean water access is essential.

[0041]

[0026] Beyond water harvesting, the chitosan film’ s antimicrobial and biodegradable properties offer broad applications, such as in food packaging to extend shelf life by managing moisture and preventing bacterial growth, or in biomedical applications as a biocompatible material for wound dressing. Overall, this invention presents a versatile, sustainable, and low-cost solution to water scarcity, aligning with global sustainability goals and supporting clean water access in diverse settings.

[0042]

[0027] The present invention is now described in detail with reference to accompanying drawing.

[0043]

[0028] FIG. 1 illustrates a method (100) for producing a chitosan-based nanocomposite film, in accordance with an embodiment of the present invention.

[0044]

[0029] The method (100) clearly starts at step (102), synthesizing one or more nanoparticles by utilizing plant-based extracts and agricultural waste. The nanoparticles used in this invention, including iron oxide (FexOy), zinc oxide (ZnO), silica oxide (SiO2), and their composites such as FeZnSi nanocomposites (NCs), are synthesized through green chemistry methods. Green chemistry methods, according to present invention, refers to environmentally friendly processes used to synthesize nanoparticles within the chitosan-based film. Instead of relying on toxic chemicals or energy-intensive techniques, the invention uses plant extracts and agricultural waste as natural reducing, stabilizing, and capping agents to create nanoparticles like iron oxide, zinc oxide, and silica.

[0045]

[0030] For example, extracts from banana peels, peanut shells, phoenix dactylifera L. and other agricultural byproducts are employed to facilitate the conversion of metal salts into nanoparticles, reducing the need for harmful chemicals. This approach minimizes environmental impact by avoiding toxic byproducts, lowering energy consumption, and making use of biodegradable, renewable resources. The resulting nanoparticles, produced in a sustainable way, are uniformly dispersed within the chitosan matrix, enhancing the fdm’s properties for water adsorption, mechanical stability, and antimicrobial protection. This environmentally sustainable approach ensures the production of nanoparticles with controlled sizes and surface properties that are optimized for water adsorption and antibacterial performance.

[0046]

[0031] Metal salts serve as precursors for synthesizing various nanoparticles in this invention, with each nanoparticle type requiring specific salts. For iron oxide nanoparticles (FexOy), iron chloride salts like ferric chloride (FeCL) or ferrous chloride (FeCL) are used, while green plant extracts act as reducing and stabilizing agents to produce uniform particles. Zinc oxide nanoparticles (ZnO) are synthesized from zinc salts, such as zinc chloride (ZnCL), zinc sulfate monohydrate (ZnSC JLO), zinc acetate dihydrate (Zn(CHsCOO)2 2H2O), and zinc nitrate hexahydrate (Zn(NOs)2 6H2O), with the choice of salt affecting the nanoparticles’ morphology and properties. Silica nanoparticles (SiCF) are created using tetraethyl orthosilicate (TEOS) as a precursor, with ammonia as a catalyst, while peanut shells and banana peels serve as natural, sustainable silica sources. Lastly, chitosan nanoparticles (Chitosan NPs) are derived from chitosan, a polysaccharide from crustacean shells, dissolved in dilute acetic acid and stabilized through ionic gelation with sodium tripolyphosphate (TPP). This green synthesis yields biocompatible, biodegradable nanoparticles ideal for water-harvesting films.

[0047]

[0032] According to an aspect of the present invention, Figure 1A depicts SEM (Scanning Electron Microscope) images illustrate the mixture of iron oxide and ZnFe2O4 nanoparticles, demonstrating uniform morphology critical for integration into the chitosan matrix.

[0048]

[0033] Synthesis of Iron Oxide Nanoparticles (FesOA: Iron oxide nanoparticles are synthesized using green methods where iron chloride salts are reduced by plant extracts such as banana peel and peanut shell extracts, which serve as reducing, stabilizing, and capping agents. These natural compounds facilitate the formation of ultrasmall nanoparticles with sizes ranging from 5 to 20 nm, significantly smaller than typical iron oxide particles. During synthesis, the pH is adjusted to ensure optimal nanoparticle formation and prevent agglomeration. The resulting nanoparticles exhibit strong hydrophilic properties, improving their water adsorption capabilities from the air while maintaining stability due to the capping effect of the plant extracts.

[0049]

[0034] According to an aspect of the present invention, Figure 2 depicts SEM images demonstrate uniform morphology of the ZnO nanoparticles, crucial for their incorporation into the chitosan matrix.

[0050]

[0035] Synthesis of Zinc Oxide Nanoparticles (ZnO): Zinc oxide nanoparticles are synthesized via a green chemical precipitation method using zinc nitrate or zinc acetate salts, with agrowaste extracts (e.g., banana peel and peanut shell extracts) acting as reducing and capping agents. The pH is carefully adjusted during synthesis to control the reaction environment and promote the formation of ultrasmall, highly crystalline ZnO nanoparticles with sizes ranging from 10 to 30 nm. These nanoparticles exhibit potent antibacterial properties due to their ability to generate reactive oxygen species (ROS). The small particle size and high crystallinity provide the ZnO nanoparticles with enhanced mechanical strength and improved water adsorption capacity.

[0051]

[0036] According to an aspect of the present invention, Figure 3 depicts SEM images show silica nanoparticle morphology produced using green methods, confirming uniform structure critical for incorporation into the films.

[0052]

[0037] Synthesis of Silica nanoparticles (SiO ): Silica nanoparticles (SiC ) are synthesized using two complementary methods: one based on a traditional chemical route and another based on a green methodology using agrowaste such as peanut shells and banana peels. Both methods result in the formation of highly efficient silica nanoparticles for enhancing the water adsorption properties of the chitosan-based films. Traditional Synthesis: Silica nanoparticles are synthesized using tetraethyl orthosilicate (TEOS) as a silica precursor, with ammonia serving as a catalyst for the condensation process. This method ensures the formation of uniform particle sizes (ranging from 1 to 50 nm) with a porous structure (< 1 nm), significantly enhancing the water adsorption surface area. Nowadays, in addition to the traditional TEOS -based method, silica nanoparticles are produced using agrowaste extracts from peanut shells (may contain 4-8% silica by weight) and banana peels (may contain 1-3% silica by weight), which naturally contain silica. This green methodology utilizes peanut shells and banana peels as sources of silica, offering a sustainable and eco-friendly alternative to chemical synthesis.

[0053]

[0038] At step (104), mixing precursors of one or more metal oxide at predetermined concentration of IM for all precursors and pH level of 7.5 to create a nanocomposite mixture. The FeZnSi nanocomposite (NC), a blend of iron oxide (FesCb), zinc oxide (ZnO), and silica oxide ( Si O2), is synthesized using green methods, with Phoenix dactylifera L. (date palm) extract serving as a natural reducing, stabilizing, and capping agent. This eco-friendly synthesis process carefully combines iron chloride, zinc nitrate, and tetraethyl orthosilicate (TEOS) precursors at specific concentrations and pH levels to optimize nanocomposite formation. The FeZnSi NC leverages the water adsorption efficiency of silica, the hydrophilic nature of iron oxide, and the antibacterial properties of zinc oxide, making it especially effective for atmospheric water harvesting. Its unique design supports both hydrophilic and hydrophobic cycles, enhancing water condensation at low temperatures and enabling direct condensation onto film surfaces. The green synthesis also ensures that the FeZnSi NC remains well-dispersed and stable, preventing degradation through multiple adsorption-desorption cycles, which supports long-term, reliable use in water-harvesting applications. Figure 4 shows SEM images demonstrate the uniform dispersion of FeZnSi NC, critical for maintaining film integrity and water adsorption capacity.

[0054]

[0039] Then at step (106), dissolving chitosan in an acetic acid solution followed by ionic gelation to obtain chitosan nanoparticles. Chitosan nanoparticles (Chitosan NPs) are synthesized from chitosan, a natural polysaccharide derived from chitin, commonly found in crustacean shells. Using a green synthesis approach, plant extracts serve as reducing and stabilizing agents, eliminating the need for harsh chemicals. To create these nanoparticles, chitosan is dissolved in dilute acetic acid and undergoes ionic gelation with sodium tripolyphosphate (TPP). Precise adjustments to the pH and concentration of this solution ensure uniform nanoparticle size and high stability. Chitosan NPs, with sizes ranging from 1 to 70 nm and a porous structure (< 1 nm), exhibit biocompatibility, biodegradability, and antibacterial properties, making them highly suitable for water-harvesting fdms by enhancing the fdm’s water adsorption surface area. Figure 5 clearly shows Chitosan nanoparticles synthesized using green methods demonstrate uniform morphology, critical for their integration into the chitosan matrix.

[0055]

[0040] Then, step (108), integrating nanoparticles into a chitosan matrix is achieved through a solution casting method, which ensures an even distribution of nanoparticles while preserving the structural integrity of the film. This process is optimized to prevent nanoparticle aggregation, a critical factor for maintaining high water adsorption efficiency and mechanical stability. The embedding process involves incorporating nanoparticles into a chitosan matrix through a systematic preparation and layering technique. Initially, the chitosan solution is prepared to create a matrix capable of forming a stable film. The nanoparticles are uniformly dispersed into a stabilizing solution to ensure even distribution and prevent aggregation. This dispersion is then introduced into the chitosan solution, either as a single composite mixture or in separate layers, depending on the desired properties of the final product. The process is completed by casting the mixture or layered solutions onto a surface, followed by controlled drying under specific temperature and time conditions. This method ensures that the nanoparticles are effectively embedded within the chitosan matrix, maintaining their functional integrity and enhancing the composite's overall performance.

[0056]

[0041] Further, in the present invention, chitosan solution is prepared by dissolving chitosan in a 0.05M acetic acid solution. Chitosan is a natural biopolymer known for its biodegradability, biocompatibility, and film-forming capabilities forming a viscous mixture that facilitates the uniform incorporation of nanoparticles. Continuous stirring is applied throughout the preparation to maintain consistent viscosity and ensure that the nanoparticles are evenly dispersed within the solution. This homogeneous distribution within the chitosan matrix allows the final film to perform effectively in water adsorption applications, leveraging the advantages of both the biopolymer and the embedded nanoparticles.

[0057]

[0042] Step (110), cross-linking the nanoparticles with chitosan matrix using a cross-linking agent. In the present invention, polyethylene glycol (PEG) is utilized as a cross-linking agent to improve the physicochemical properties of the chitosan-based films. Cross-linking with PEG enhances the interaction between the chitosan matrix and the embedded nanoparticles, resulting in a more structurally sound and durable film.

[0058]

[0043] The process begins by dispersing the nanoparticles into a PEG solution, typically at a concentration of 2-5% volume / volume (v / v). This PEG-nanoparticle mixture is then integrated into the chitosan solution, where PEG acts as a bridge, creating strong covalent and non-covalent interactions within the matrix. These interactions form a stable, interconnected network between the nanoparticles and the chitosan polymer chains, effectively locking the nanoparticles into place within the matrix. This cross-linking method results in enhanced structural integrity, tensile strength, elasticity, and durability of the films. The improvements in tensile strength and elasticity provided by PEG enable the films to withstand multiple cycles of water adsorption and desorption without significant degradation, an essential quality for sustained water-harvesting performance.

[0059]

[0044] In step (112), casting the nanocomposite mixture to form a multi-layered film. The films were initially designed as single-layer films containing one type of nanoparticle. However, according to an embodiment of the present invention, single film has been extended to a multilayered design, where different layers incorporate different nanoparticles, each contributing to the overall performance of the film. The arrangement of films is as follows:

[0060] • Layer 1 serves as the base layer, incorporating the FeZnSi nanocomposite to enhance water adsorption efficiency and provide antibacterial properties.

[0061] • Layer 2 is embedded with ZnO nanoparticles, which boost hydrophilicity and facilitate the rapid condensation and release of adsorbed water.

[0062]

[0045] This layered approach is crucial for effectively managing hydrophilic and hydrophobic cycles essential to the adsorption and desorption of water. The hydrophilic and hydrophobic nanoparticles formed are 5-40% of the polymer weight. With carefully engineered kinetic diameters of less than 0.5 nm, and specifically around 0.3 nm, the material selectively traps only H2O molecules, supporting the auto-generation of water. The interaction between different nanoparticle layers optimizes water capture, retention, and release, achieving high efficiency in the cycle of water condensation.

[0063]

[0046] In an alternate embodiment of the present disclosure, the multi-layered films may be extended to include three or four layers, using additional chitosan nanocomposites where each layer is customized to provide functionalities such as enhanced mechanical stability, stronger antibacterial effects, or efficient water condensation at low temperatures. This modular, adaptable design maximizes water-harvesting potential, allowing the films to be used effectively across various environmental conditions, thereby broadening their practical applications. Figure 6: SEM and confocal microscopy images illustrate the uniform integration and well-dispersed nanomaterials, which reduce pore size and enhance surface roughness, improving adsorption efficiency in multi-layered films. Figure 6 illustrates the uniform integration of nanoparticles into chitosan-based nanocomposite films, as evidenced by SEM and confocal microscopy images. The images highlight reduced pore sizes and enhanced surface roughness, both of which improve adsorption efficiency in multi-layered films. This integration is critical for the invention's application in atmospheric water harvesting and purification. Figure 7: Mechanical properties (e.g., tensile strength, durability) are shown in graphs, indicating enhancements in strength and resilience over multiple cycles. Figure 7 demonstrates the mechanical performance of chitosan- based nanocomposite films via tensile strength testing. The stress-deformation graph for samples cl, c2, and c3 highlights enhanced durability and elasticity, showcasing the film's ability to maintain structural integrity under stress. This durability supports repeated water adsorptiondesorption cycles, crucial for atmospheric water harvesting applications.

[0064]

[0047] Performance and Characterization of the Films: The chitosan-based films exhibit strong performance and resilience across multiple water capture cycles, demonstrating excellent hydrophilicity and water adsorption abilities. The following tests may be performed to test performance and characterize the film formed.

[0065]

[0048] Initial Performance Tests: Initial tests revealed a water contact angle (WCA) between 30° and 70°, indicating high hydrophilicity, essential for effective water capture. In varied lab conditions, the films achieved daily capture rates from 1.993 to 5.33 liters per kilogram of film, depending on humidity levels (30-85%), making them efficient for different environments.

[0066]

[0049] Characterization of Embedded Nanoparticles: To confirm nanoparticle integration, characterization techniques like Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) assessed morphology, with particles sized between 1-50 nm. Energy- Dispersive X-ray Spectroscopy (EDX) and X-ray Diffraction (XRD) validated the elemental and crystalline structure, critical for optimal water capture. Confocal Microscopy and 3D Mapping confirmed sub-nanometer pore sizes, enhancing adsorption capacity.

[0067]

[0050] Antibacterial and Antioxidant Testing: The films were also tested for antibacterial and antioxidant properties, where embedded ZnO nanocomposites displayed significant antibacterial effectiveness, preventing pathogenic contamination and ensuring water purity essential for applications in remote areas with limited clean water access.

[0068]

[0051] In accordance with embodiment of the present invention, a specially designed water collection device that maximizes the efficiency of the multi-layered films, optimized for efficiency by adapting to the film shape. The device is designed to be flexible and adaptable to the shape of the chitosan-based films, allowing it to conform to the multi-layered structure and enhance water collection efficiency. The device is cone-shaped to increase the surface area available for water collection. This shape promotes the natural flow of water droplets downward due to gravity, enabling the direct dripping of water into a reservoir or collection basin. The cone design also allows for the passive condensation of water, improving water capture without the need for external energy inputs. Figure 8 shows Illustrates the cone-shaped design’s increased water collection area compared to flat films. Figure 8 showcases the cone-shaped water collection device designed for enhanced atmospheric water harvesting. The structure maximizes surface area for condensation and channels collected water efficiently into a reservoir using gravity. This innovative design complements the multi-layered nanocomposite film, improving passive water collection performance without requiring external energy.

[0069]

[0052] Water Adsorption and Regeneration testing: Adsorption performance is notable, with a capture rate of up to 1.65 litres per kilogram of film per hour under low-humidity (below 30% RH), outperforming traditional materials like super hygroscopic polymer films (SHPFs) and metalorganic frameworks (MOFs) in arid conditions. FeZnSi nanocomposites and ZnO nanoparticles enhance moisture absorption and prevent saturation, while ZnO provides antibacterial protection, making the films practical in challenging settings like desert climates.

[0070]

[0053] Auto-Generation of Water: The films also autogenerate water without external energy, evidenced by spontaneous droplet formation in an Eppendorf tube during tests. This suggests a reliable, low-cost solution for atmospheric water generation in ambient conditions. This indicates the successful conversion of atmospheric moisture into liquid water, even without the application of external energy. The observation of water droplets inside the Eppendorf tube suggests that the films are highly effective at harvesting water from ambient air, providing a low-cost, passive solution for atmospheric water generation.

[0071]

[0054] Regeneration and Desorption: Additionally, the film release 70% of captured water within 10 minutes at mild temperatures (below 60°C), allowing repeated use with minimal energy, unlike MOFs, which need higher temperatures. The ability to regenerate at low temperatures allows the films to be used repeatedly with minimal energy input, ensuring sustainability and reducing operational costs.

[0072]

[0055] Figure 9 depicts the improved hydrophilicity of the films, evidenced by the reduced contact angle as shown in enhances water adsorption. Figure 9 demonstrates the improved hydrophilicity of the chitosan-based nanocomposite films. The reduction in water contact angle from 68.7° to 39.4° indicates enhanced surface wettability, facilitating efficient water adsorption. This feature is critical for maximizing moisture capture in atmospheric water harvesting applications, especially in low-humidity environments. Figure 10 depicts water droplet formation inside the Eppendorf tube and water generation on the film's surface during tests confirm the film's ability to passively autogenerate water. Figure 10 highlights the successful water generation and collection capabilities of the chitosan-based nanocomposite films. The spontaneous formation of water droplets in Eppendorf tubes demonstrates passive atmospheric water harvesting. The packaged films and experimental setups confirm the material's scalability, storage stability, and practical usability for decentralized water purification applications.

[0073]

[0056] Antimicrobial Properties: Finally, the antimicrobial properties of ZnO nanoparticles and FeZnSi nanocomposites prevent bacterial, mold, and fungal contamination, ensuring that the harvested water remains safe for drinking and other uses. These properties make the films especially suitable for environments where microbial contamination is a concern, such as in remote areas, disaster zones, or low-resource settings where clean water is essential for health and sanitation. ZnO nanoparticles generate reactive oxygen species (ROS) upon exposure to moisture and light, which effectively destroy a broad spectrum of bacteria and inhibit fungal growth by disrupting cell membranes and damaging their internal components. This ROS production is highly efficient in neutralizing pathogens, mold, and spores, ensuring that the water collected remains safe for human consumption without harming mammalian cells.

[0074]

[0057] The FeZnSi nanocomposite further strengthens this antimicrobial defense by combining the properties of iron oxide (FesO^ and zinc oxide. Iron oxide in the nanocomposite helps to disrupt fungal membrane structures, adding a layer of resistance against mold and fungal spores. Additionally, the chitosan matrix itself possesses natural antibacterial and antifungal properties, working in synergy with the nanoparticles to reduce bacterial growth and prevent mold colonization on the film’s surface.

[0075]

[0058] Together, these components create a multi-functional antimicrobial barrier, ideal for applications in water purification in remote or low-resource areas. Furthermore, the film’s ability to control moisture and prevent microbial contamination makes it suitable for food packaging, where preserving product safety is critical. Figure 11 shows the antimicrobial efficacy of the films highlights the superior protection provided by ZnO nanoparticles and FeZnSi NC compared to chitosan-only films, which developed mold within one week, whereas the nanoparticle-embedded films remained free from contamination. Figure 11 highlights the antimicrobial efficacy of the chitosan-based nanocomposite films. The images compare a nanoparticle-embedded film, which remains intact and mold-free, to a chitosan-only film showing significant degradation and mold growth. This demonstrates the superior antimicrobial protection provided by ZnO and FeZnSi nanocomposites, ensuring the film's durability and water purity.

[0076]

[0059] Field Testing and Scalability: The films were tested using a cone-shaped water collection device, designed to enhance water harvesting by increasing surface area and directing condensed water into a collection reservoir. During field tests in arid conditions with 15-30% relative humidity, the films successfully captured moisture from the air, with visible water droplets forming on the film surfaces and flowing into the collection basin. These tests confirmed the system's effectiveness in real-world settings.

[0077]

[0060] For scalability, the solution casting method and environmentally friendly nanoparticle synthesis enable large-scale production. This makes the films viable for widespread deployment in both urban and rural areas, offering decentralized water harvesting solutions for communities with limited access to clean water.

[0078]

[0061] This invention, with its remarkable sterilization and disinfection power, can be applied across various domains. Here are some possible use-cases:

[0079] • Water Resource Management: The film is highly effective in atmospheric water harvesting (AWH), making it valuable in arid and semi-arid regions where traditional water sources are limited. By passively capturing and condensing moisture from the air, the films offer an efficient, decentralized water solution without the need for external energy, ideal for rural or off-grid communities. • Environmental Engineering: As a sustainable technology, the film aligns with eco-friendly practices by utilizing green synthesis methods and biodegradable materials. Its energyefficient water adsorption and desorption capabilities make it suitable for large-scale water management projects aimed at addressing water scarcity in dry climates, while also contributing to reduced environmental impact.

[0080] • Atmospheric Water Harvesting. In arid and semi-arid environments, the films capture moisture passively from the air, offering a low-cost, decentralized solution for water harvesting.

[0081] • Healthcare and Pharmaceutical Storage: The film's moisture control and antimicrobial protection can benefit pharmaceutical and biomedical applications where precise humidity levels and sterile conditions are crucial. It can be used to protect medical supplies, electronics, and other sensitive equipment from moisture and microbial contamination.

[0082] • Food Packaging: With its antimicrobial properties and moisture -regulating abilities, the film serves as an effective material for biodegradable food packaging. It helps extend the shelf life of perishable products by controlling humidity and inhibiting bacterial growth, offering a sustainable alternative to traditional plastic packaging, especially in industries focused on reducing plastic waste.

[0083]

[0062] Each of these use-cases involves the deployment of the method (100) producing a chitosan-based nanocomposite film.

[0084]

[0063] The invention presents several advantages:

[0085] 1. Efficient Atmospheric Water Harvesting: The film’ s multi-layered design and nanoparticle integration enable high water capture rates, even in low-humidity environments, making it suitable for arid and semi-arid regions.

[0086] 2. Energy-Efficient Water Collection: Passive water condensation and the ability to autogenerate water without external energy reduce operational costs and make the system ideal for off-grid applications.

[0087] 3. Scalability: The solution casting method and green nanoparticle synthesis allow for cost- effective mass production, supporting large-scale deployment in urban and rural areas. 4. Environmentally Friendly: Made from biodegradable chitosan and synthesized using green methods, the film minimizes environmental impact and aligns with sustainable practices.

[0088] 5. Antimicrobial Protection: Embedded ZnO and FeZnSi nanoparticles provide strong antibacterial and antifungal properties, ensuring that the harvested water is free from contaminants, making it safe for drinking.

[0089] 6. Enhanced Durability: Polyethylene glycol (PEG) cross-linking improves the fdm’s structural integrity, allowing it to withstand multiple adsorption-desorption cycles without degradation.

[0090] 7. Versatile Applications: Besides water harvesting, the fdm’s antimicrobial and moistureregulating properties make it suitable for food packaging, biomedical applications, and pharmaceutical storage.

[0091]

[0064] These advantages collectively contribute to offering a versatile, scalable, and environmentally friendly solution for water harvesting and purification, leveraging the controlled hydrophobicity and hydrophilicity of nanoparticles to enhance performance.

[0092]

[0065] Various modifications to these embodiments are apparent to those skilled in the art from the description and the accompanying drawings. The principles associated with the various embodiments described herein may be applied to other embodiments. Therefore, the description is not intended to be limited to the embodiments shown along with the accompanying drawings but is to be providing broadest scope of consistent with the principles and the novel and inventive features disclosed or suggested herein. Accordingly, the invention is anticipated to hold on to all other such alternatives, modifications, and variations that fall within the scope of the present invention and the appended claims.

Claims

CLAIMS1. A method (100) for producing a chitosan-based nanocomposite film, the method comprising steps of: synthesizing (102) one or more nanoparticles from precursors of one or more metal oxides by utilizing plant-based extracts and agricultural waste; mixing (104) precursors of one or more metal oxide at predetermined concentration and pH level to obtain a nanocomposite mixture; dissolving (106) chitosan in an acetic acid solution followed by ionic gelation to obtain one or more chitosan nanoparticles; embedding (108) the nanoparticles into a chitosan matrix; cross-linking (110) the nanoparticles with the chitosan matrix using a cross-linking agent; and extending (112) the nanocomposite mixture to form a multi-layered film, wherein each layer contains specific nanoparticles for targeted properties like water adsorption, mechanical stability, and antimicrobial protection.

2. The method (100) as claimed in claim 1, wherein the nanoparticles include iron oxide (FexOy), zinc oxide (ZnO), silica (SiCE), and FeZnSi nanocomposites.

3. The method (100) as claimed in claim 1, wherein the precursors of metal oxides include iron chloride salts such as ferric chloride (FeCh) or ferrous chloride (FeCE), zinc salts, including zinc chloride (ZnCE), zinc sulfate monohydrate (ZnSCb FbO), zinc acetate dihydrate (Zn(CHsCOO)2 2H2O), and zinc nitrate hexahydrate (Zn(NOs)2 6H2O), tetraethyl orthosilicate (TEOS), and chitosan.

4. The method (100) as claimed in claim 1, wherein precursors of metal oxides are mixed at predetermined concentration of 1 M for all precursors and pH level 7.5.

5. The method (100) as claimed in claim 1, wherein plant-based extracts and agricultural waste include banana peel, peanut shells, phoenix dactylifera L. and other agricultural byproducts.

6. The method (100) as claimed in claim 1, wherein to obtain a nanocomposite mixture Phoenix dactylifera L. (date palm) extract is utilized as a reducing, stabilizing, and capping agent.

7. The method (100) as claimed in claim 1, wherein sodium tripolyphosphate (TPP) is used in ionic gelation.

8. The method (100) as claimed in claim 1, wherein the chitosan matrix is cross-linked with polyethylene glycol (PEG) solution.

9. The method (100) as claimed in claim 1, wherein kinetic diameters of the multilayered film is less than 0.5 nm, specifically reaching 0.3 nm.

10. A chitosan-based nanocomposite film, the film comprising: one or more of hydrophilic and hydrophobic nanoparticles; and one or more plant-based extracts and agricultural waste.

11. The chitosan-based nanocomposite film as claimed in claim 9, wherein the plant-based extracts include banana peel, peanut shells, phoenix dactylifera L. and agricultural waste.

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