Spongy adsorbent products including oxidized cellulose nanofibers for solute separation

Abstract

A spongy product includes a three-dimensional scaffold that includes charged cellulose fibrils and that is configured to adsorb, absorb, ion-exchange, or remove a solute from a liquid medium, when the spongy product is added to the liquid medium. A method of manufacturing a spongy product includes providing an aqueous suspension including charged cellulose fibrils, forming the aqueous suspension into a precursor body, freezing the precursor body to form a porous network within the precursor body, crosslinking the porous network to form a crosslinked structure within the precursor body, and incubating the precursor body including the crosslinked structure to form the spongy product.

Description

Attorney Docket No. 201291.17. PCTSPONGY ADSORBENT PRODUCTS INCLUDING OXIDIZED CELLULOSE NANOFIBERS FOR SOLUTE SEPARATION CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Patent Application No. 63 / 779,912 filed on March 28, 2025. The entire contents of this application are hereby incorporated by reference.BACKGROUND OF THE INVENTION1. Field of the Invention

[0002] The present invention relates to compositions and methods for manufacturing spongy products that remove solutes from liquid media, including aqueous and non-aqueous media, using charged cellulosic fibrils as adsorbent and / or absorbent materials.2. Description of the Related Art

[0003] Water contamination by charged pollutants remains a significant environmental and public health concern. Such pollutants are commonly classified according to their ionic character, as cationic pollutants and anionic pollutants present distinct removal challenges in contaminated water sources.

[0004] Cationic pollutants generally include many dissolved heavy metal ions and certain synthetic dyes. Representative cationic heavy metals include, for example, cadmium (Cd), lead (Pb), Iron (Fe), mercury (Hg), and nickel (Ni), which are frequently introduced into water bodies through industrial discharge, mining operations, and agricultural runoff. Cationic dye pollutants include, for example, Basacryl Red GL, methylene blue, crystal violet, malachite green, rhodamine B, and basic fuchsin. These contaminants are often toxic, persistent, and prone to bioaccumulation, thereby posing risks such as neurological damage, organ toxicity, mutagenicity, and carcinogenicity.

[0005] Anionic pollutants include metal oxyanions, anionic dyes, nutrients, and certain persistent organic contaminants. For example, chromium- and arsenic-containing contaminants may exist in water as anionic oxyanions. Anionic synthetic dyes include methyl orange, Eriochrome black T, Alizarin yellow R, acid orange, and Congo red. Nutrient pollutants, including nitrate and phosphate species, are also commonly anionic and are major contributors toeutrophication and ecosystem imbalance. In addition, several emerging contaminants, including certain per- and polyfluoroalkyl substances (PFAS) compounds, may occur in anionic form and are particularly problematic because of their chemical stability, mobility, and resistance to degradation.

[0006] Certain contaminants may exist in either cationic or anionic form, depending on chemical structure and / or environmental conditions. These include some PFAS compounds, microplastics, engineered nanomaterials, and other emerging pollutants. Such variability further complicates treatment, as many conventional systems are optimized only for a narrow class of charged species.

[0007] Conventional water treatment materials and technologies have significant drawbacks in addressing a broad spectrum of ionic pollutants. Conventional water treatments using activated carbon, although widely used as an adsorbent, often exhibit only moderate adsorption efficiency for certain charged contaminants, suffer from fouling, limited regeneration capability, and relatively high operating costs. Conventional water treatments using ion-exchange resins may provide selectivity for specific ionic contaminants, but the conventional water treatments using ion-exchange resins are frequently limited by clogging, poor performance in complex pollutant mixtures, and the need for repeated chemical regeneration. Conventional membrane filtration systems can effectively remove a range of contaminants but are energy-intensive, susceptible to fouling, and generate concentrated secondary waste streams, requiring further disposal or treatment. Conventional precipitationbased processes may be useful for some metal ions but generally lack selectivity, may require substantial chemical inputs, and often produce sludge that must be managed.

[0008] Accordingly, there remains a need for improved materials and treatment approaches capable of efficiently removing both cationic and anionic pollutants from contaminated water, while reducing the disadvantages associated with conventional adsorbents, ion-exchange materials, membranes, and related treatment systems.SUMMARY OF THE INVENTION

[0009] To overcome the problems described above, example embodiments of the present invention provide spongy products and methods of manufacturing spongy products thatprovide removal, sequestration, separation, capture, adsorption, absorption, ion exchange, or combinations thereof of one or more solutes from a liquid medium using charged cellulosic fibrils, with cross-sectional dimensions between 2 nanometers-50 nanometers, as adsorbent and / or absorbent materials. The charged cellulosic fibrils include nanocellulose (NC), cellulose nanocrystals (CNC), cellulose nanofibrils (CNF), cellulose microfibrils (CMF), lignin-containing cellulose nanofibers (LCNFs), or combinations thereof, prepared by a Nitro-Oxidation Process (NOP) or any other suitable process. The liquid media can include aqueous or non-aqueous media. The solutes may include cationic and / or anionic pollutants.

[0010] Example embodiments of the present invention include spongy products with tunable charge properties (cationic and / or anionic) that can be prepared by a freeze-thaw process followed by crosslinking of carboxylated cellulose nanofibers (CNFs) with metal ions or hydrogen bonding agents, that provide a foam-like, poroelastic, biodegradable, scalable, and cost-effective solution that can remove solutes from a liquid medium. The spongy products can include a large surface area, tunable functional groups, and excellent reusability, making the spongy products superior alternatives to conventional and synthetic adsorbents.

[0011] In addition to surface-charge differences (anionic or cationic), the spongy products, including wet sponges and aerated sponges, can also differ in structural configuration and performance characteristics.

[0012] The term "sponge" can include HydroSponge, AeroSponge, or both, unless expressly stated otherwise.

[0013] HydroSponge is an example of a wet sponge that includes a pre-hydrated scaffold formed from carboxylated cellulose nanofibers (CNFs) crosslinked with metal ions or other cationic crosslinking agents. The cationic spongy product can exhibit high elasticity, substantial water-retention capacity, efficient drainage and reabsorption behavior, high porosity, compressibility, and reusability, thereby rendering the cationic spongy product suitable for removal of a wide range of anionic pollutants from liquid media, such as water sources.

[0014] AeroSponge is an example of an aerated sponge that is a substantially dry, water-free version of a wet sponge. The aerated sponge may be characterized by ultra-low weight, high porosity, good mechanical strength, and high pollutant adsorption capacity, making wetsponges easier to transport and particularly effective for the rapid removal of organic pollutants, heavy metals, and PFAS.

[0015] The efficiency of the spongy materials of the example embodiments of the present invention is attributed to pore size distribution and scaffold engineering, which enhances mechanical properties, pollutant diffusion, and adsorption kinetics. Unlike conventional hydrogels and aerogels, these materials exhibit superior compressibility, structural integrity, and fast diffusion and adsorption rates of pollutants, as CNFs are included in a three-dimensional porous structure. This structural advantage of the resulting spongy products can significantly improve the pollutant adsorption efficiency, making the spongy materials applicable in a broad range of applications in separation science either through adsorption and / or ion exchange phenomena.

[0016] The spongy product can be made of carboxylated cellulose nanofibers (CNFs) prepared by a freeze-thaw process followed by an ionic (e.g., divalent and trivalent cations) or chemical crosslinking treatment (e.g., hydrogen bonding). But other crosslinking agents, such as urea, chitosan, ethylene glycol, acetic acid, tannic acid, polyphenols polyacrylic acid, polyamides, polyvinyl alcohol, and their derivatives, can be used to achieve structural integrity, cationic or anionic modification, rapid adsorption kinetics, and high adsorption efficiency.

[0017] The NOP-produced nanocellulose (NC) materials can be extracted from a broad range of lignocellulosic feedstocks, including, for example, both woody and non-woody plants, even from underutilized sources such as agriculture, food, and animal wastes. More specifically, the NC materials can be derived from a biomass source from diverse wood and non-wood sources including hard and soft woods, jute, palm trees, sugarcane bagasse, corn, wheat, oats, rice, sorghum, oil palm, bamboo, spinifex, coastal bermudagrass, miscanthus, switchgrass, azolla, seaweeds, flax, hemp, ramie, kenaf stalk fiber, kenaf core, abaca, sisal, pineapple, banana leaf, banana peel, banana fiber, curaua, lotus leaf stalk, roselle, seed hair fiber, cotton fiber, kapok fiber, areca nut fiber, coconut, potato, cabbage, tomato, rubberwood, Indian screw tree, achira fiber, citrus, soybean, soybean straw, spent grain, soy hull, pea hull, grape pomace, fruit pomace, or any combination thereof. The non-plant biomass feedstock can also be selected from animal manure, cow manure, horse manure, poultry litter, aquatic biomass,shrimp shells, lobster shells, agricultural residues, food-processing waste, eggshells, egg membranes, livestock / animal-processing waste, bones, cartilage, insect biomass, algae, seaweed, mixed food waste, consumer / residential / urban / municipal organic waste, or a mixture thereof. The non-plant biomass feedstock can include a lignocellulosic component.

[0018] To further improve the adsorption efficiency, biochar, activated carbons, and carbon nanomaterials can be incorporated into CNF suspensions prior to the preparation of the spongy products to provide additional functionality in the final products.

[0019] Example embodiments of the present invention provide new adsorbents that can be prepared in varying shapes, density, and properties, enabling new remediation pathways. For example, spongy products can be fabricated into a light-weight form, allowing the design of a floating adsorption system for surface water treatment. The spongy products can also be used directly in the column or batch reactor format for continuous industrial wastewater treatment.

[0020] The combination of biodegradability, scalability, and enhanced adsorption properties of the example embodiments of the present invention, including, for example, wet sponges and aerated sponges, provide adsorptive materials for new water remediation technologies.

[0021] According to an example embodiment of the present invention, a spongy product includes a three-dimensional scaffold that includes charged cellulose fibrils and that is configured to adsorb, absorb, ion-exchange, or remove a solute from a liquid medium, when the spongy product is added to the liquid medium.

[0022] The charged cellulose fibrils can include nanocellulose, cellulose nanocrystals, cellulose nanofibrils, cellulose microfibrils, lignin-containing cellulose nanofibers, oxidized cellulose fibrils, derivatized cellulose fibrils, or any combination thereof. The charged cellulose fibrils can include cellulose fibrils including carboxyl, aldehyde, hydroxyl, sulfate, sulfonate, phosphate, phosphonate, amine, ammonium, imine, amidine, guanidinium, zwitterionic functionality, metal-coordination functionality, ion-exchangeable functionality, or any combination thereof. The charged cellulose fibrils can include nitro-oxidized fibrils, TEMPO-oxidized fibrils, carboxymethylated fibrils, phosphorylated fibrils, sulfonated fibrils, periodate-oxidized fibrils, chlorite-oxidized fibrils, esterified fibrils, etherified fibrils, amidated fibrils,aminated fibrils, enzymatically treated fibrils, mechanically fibrillated fibrils, acid-hydrolyzed fibrils, or any combination thereof.

[0023] The three-dimensional scaffold can be configured as a cationic sponge adsorbent, an anionic sponge adsorbent, an amphoteric sponge adsorbent, a zwitterionic sponge adsorbent, or a spongy product including both anionic and cationic adsorption sites.

[0024] The three-dimensional scaffold can be crosslinked such that the three-dimensional scaffold includes cationic functionality and / or affinity to define a cationic sponge adsorbent. The three-dimensional scaffold can be crosslinked with a divalent ion, a trivalent ion, or any combination thereof. The three-dimensional scaffold can be crosslinked with calcium, magnesium, zinc, manganese, copper, iron, aluminum, nickel, cobalt, molybdenum, a rare earth metal, or any combination thereof. The three-dimensional scaffold can be crosslinked with Fe3+, Al3+, Ca2+, Mg2+, Zn2+, or any combination thereof.

[0025] The three-dimensional scaffold can be crosslinked such that the three-dimensional scaffold includes anionic functionality and / or affinity to define an anionic sponge adsorbent. The three-dimensional scaffold can be stabilized by hydrogen bonding, fibril entanglement, a hydrogen-bonding crosslinking agent, or any combination thereof. The three-dimensional scaffold can include a hydrogen-bonding crosslinking agent and / or a non-covalent stabilizer. The hydrogen-bonding crosslinking agent and / or the non-covalent stabilizer can include urea, citric acid, genipin, chitosan, polydopamine, lignosulfonate, polyethylene glycol, carboxyl-functionalized polymers or oligomers, polyacrylic acid, polyvinyl alcohol, polyamides, ureidopyrimidone-containing materials, tannic acid, polyphenols, derivatives thereof, or any combination thereof.

[0026] The three-dimensional scaffold can define a hydrated sponge, a hydrogel sponge, a water-loaded sponge, a dry sponge, an aerated sponge, an aerogel sponge, or any combination thereof. The three-dimensional scaffold can define an interconnected pore structure, an opencell structure, aligned pores, lamellar pores, gradient pores, directional pores, a honeycomb microstructure, or any combination thereof.

[0027] The solute can include a cationic pollutant, an anionic pollutant, an amphoteric pollutant, a neutral pollutant, an organic pollutant, an inorganic pollutant, a biologicalpollutant, or any combination thereof. The solute can include a heavy metal, a metal ion, a radionuclide, an oxyanion, an inorganic salt, a nutrient, a cationic dye, an anionic dye, a neutral dye, a pharmaceutical, an endocrine disrupting compound, a pesticide, a herbicide, a surfactant, a plastic, a microplastic, a nanoplastic, an engineered nanomaterial, a pathogen, a biomolecule, a protein, a microorganism, a toxin, or any combination thereof.

[0028] The solute can include a per- and polyfluoroalkyl substance (PFAS). The PFAS can include a short-chain PFAS, a long-chain PFAS, a linear PFAS, a branched PFAS, a polymeric PFAS, an oligomeric PFAS, a fluorotelomer compounds, a fluoropolymer degradation product, a GenX compound, a perfluoroalkyl sulfonate, a perfluoroalkyl carboxylate, or any combination thereof. The PFAS can include perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorobutanesulfonic acid (PFBS), perfluorobutanoic acid (PFBA), hexafluoropropylene oxide dimer acid, or a salt thereof.

[0029] The spongy product can further include activated carbon, biochar, gelatin, cellulose sludge, lignin, chitosan, metal oxide nanoparticles, a clay, a zeolite, a nanomaterial, a carbon nanomaterial, an inorganic sorbent, an organic sorbent, a polymer, a biopolymer, a mineral filler, or any combination thereof.

[0030] According to an example embodiment of the present invention, a method of manufacturing a spongy product includes providing an aqueous suspension including charged cellulose fibrils, forming the aqueous suspension into a precursor body, freezing the precursor body to form a porous network within the precursor body, crosslinking the porous network to form a crosslinked structure within the precursor body, and incubating the precursor body including the crosslinked structure to form the spongy product.

[0031] The method can further include subjecting the precursor body to one or more freeze-thaw cycles or to ice templating. The method can further include, after incubating the precursor body including the crosslinked structure, drying, freeze-drying, solvent exchanging, or lyophilizing the crosslinked structure to form the spongy product.

[0032] Crosslinking the porous network can include using an ionic crosslinking agent, a hydrogen-bonding crosslinking agent, a covalent crosslinking agent, a non-covalent stabilizer, or any combination thereof.

[0033] According to an example embodiment of the present invention, a method of removing a pollutant from a liquid medium includes contacting the liquid medium with the spongy product of one of various example embodiments of the present invention, in batch mode, floating mode, immersion mode, gravity-fed mode, continuous-flow mode, cartridge mode, packed-bed mode, column mode, membrane-assisted mode, or any combination thereof, thereby removing the pollutant from the liquid medium.

[0034] The pollutant can include a cationic pollutant, an anionic pollutant, an amphoteric pollutant, an organic pollutant, an inorganic pollutant, a per- and polyfluoroalkyl substance (PFAS), or any combination thereof.

[0035] The spongy product can be configured as a mat, a sheet, a pad, a slab, a block, a monolith, a membrane body, a cartridge insert, a filter insert, a floating sorbent, a granular medium, a powder, a pellet, a rod, a cylinder, a bead, a shredded fragment, a rolled body, a folded body, a honeycomb body, a vertical adsorbent body, a layered article, a multilayer article, or any combination thereof. The system can further include an active adsorption layer and a scavenging layer that captures leached ions, residual contaminants, competing ions, or any combination thereof.

[0036] The above and other features, elements, characteristics, steps, and advantages of the present invention will become more apparent from the following detailed description of example embodiments of the present invention with reference to the attached drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The patent or application file contains at least one drawing executed in color. The patent or application file also contains a corresponding black and white line drawing for each of the at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

[0038] Fig. 1 is a schematic flowchart showing the preparation of a spongy product.

[0039] Figs. 2A and 2B show the preparation of a wet-sponge mat including a mixture of CNF and biochar. Fig. 2A is in black and white. Fig. 2B is in color.

[0040] Figs. 3A-3L are pictures showing the preparation of adsorbents, which can be used with, for example, a wet sponge or an aerated sponge in various shapes and forms. Figs. 3A-3F are in black and white. Figs. 3G-L are in color.

[0041] Fig. 4 shows various shapes of example sponges, including granular, powder, beads, and cylindrical, in which the internal structure of the sponges can be honeycomb-like with composite scaffolding walls with skin-core layers.

[0042] Fig. 5 is a picture of a scanning electron microscopy (SEM) image of a Fe3+-crosslinked sponge that has been used for the adsorption of various solutes.

[0043] Fig. 6 shows the preparation of sponges using freeze-thaw cycles to physically crosslink, for example, by hydrogen bonding, a CNF network for Pb2+and Cd2+adsorption, followed by structural and compositional analysis.

[0044] Fig. 7 shows the preparation of wet sponges crosslinked with Fe3+and Al3+for enhanced arseniteadsorption.

[0045] Fig. 8 shows the preparation of charcoal-based sponges and Fe3+crosslinked wet sponges, integration of the charcoal-based sponges and the wet sponges into filter cartridges for arsenite removal, and the corresponding analytical evaluation.

[0046] Fig. 9 is a graph showing the nonlinear adsorption isotherm fits using the Langmuir, Freundlich, and Sips models for determining the maximum adsorption capacity Qmax of wet sponges for Cd2+.

[0047] Fig. 10 is a graph showing the nonlinear adsorption isotherm fits using the Langmuir, Freundlich, and Sips models for determining the maximum adsorption capacity Qmax of wet sponges for Pb2+.

[0048] Fig. 11 is a graph showing the nonlinear adsorption isotherm fits using the Langmuir, Freundlich, and Sips models for determining the maximum adsorption capacity max of Fe3+crosslinked wet sponges for arsenite (AsO^-).

[0049] Fig. 12 is a graph showing the nonlinear adsorption isotherm fits using the Langmuir, Freundlich, and Sips models for determining the maximum adsorption capacity Qmax of Al3+crosslinked wet sponges for arsenite

[0050] Fig. 13 is a bar graph showing Arsenite (AsO^~) removal efficiency across four reuse cycles using a single filter cartridge includes a two-layer configuration of charcoal sponges at the bottom and Fe3+crosslinked wet sponges at the top, where each bar represents the remaining amounts as a percentage.

[0051] Fig. 14 is a bar graph showing the comparative adsorption of arsenite, phosphate, and sulfate Fe3+and Al3+crosslinked hydrogels, where each bar represents the adsorbed amounts and where the percentage removed is indicated.

[0052] Fig. 15 is a graph showing adsorption of PFOA, PFOS, PFBA, and PFBS using wet sponges crosslinked with Fe3+.

[0053] Fig. 16 is a graph showing adsorption of PFOA, PFOS, PFBA, and PFBS using wet sponges prepared from freeze-thawing of CNF / gelatin hydrogels containing 0.5 w / w% activated carbon, crosslinked with 50-mM Fe3+.

[0054] Fig. 17 are pictures showing poroelastic behavior of a wet sponge for better reusability, in which (A) shows a CNF / gelatin hydrogel with 0.5 w / w% activated carbon, crosslinked with 50-mM Fe3+, (B) a wet sponged compressed to remove water, and (C) a wet sponge has swelled to its original shape when submerged in water.

[0055] Fig. 18 is a bar graph showing adsorption of Basacryl Red GL at different initial concentrations using an aerated sponged, in which approximately 50 mL of dye solution was treated with 0.25 g of sponge and stirred for 24 h prior to measurement of adsorption efficiency.DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0056] A spongy product, including, for example, a sponge, can be prepared as a porous mat or vertically oriented adsorbent body and that may subsequently be processed into a range of shapes and sizes suitable for water purification and solute separation as shown in Figs. 1-5. The spongy product can be configured, for example, as a mat, a sheet, a pad, a slab, a block, a monolith, a membrane body, a cartridge insert, a filter insert, a floating sorbent, a granular medium, a powder, a pellet, a rod, a cylinder, a bead, a shredded fragment, a rolled body, a folded body, a honeycomb body, a vertical adsorbent body, a layered article, a multilayer article, or any combination thereof.

[0057] The spongy product can be used to adsorb, absorb, ion-exchange, or remove a solute from a liquid medium, when the spongy product is added to the liquid medium. A solute (e.g., a pollutant) can be removed from a liquid medium by contacting the liquid medium with the spongy product in batch mode, floating mode, immersion mode, gravity-fed mode, continuous-flow mode, cartridge mode, packed-bed mode, column mode, membrane-assisted mode, or any combination thereof. The solute can include a cationic pollutant, an anionic pollutant, an amphoteric pollutant, a neutral pollutant, an organic pollutant, an inorganic pollutant, a biological pollutant, or any combination thereof. The solute can include a heavy metal, a metal ion, a radionuclide, an oxyanion, an inorganic salt, a nutrient, a cationic dye, an anionic dye, a neutral dye, a pharmaceutical, an endocrine disrupting compound, a pesticide, a herbicide, a surfactant, a plastic, a microplastic, a nanoplastic, an engineered nanomaterial, a pathogen, a biomolecule, a protein, a microorganism, a toxin, or any combination thereof. The solute can include a per- and polyfluoroalkyl substance (PFAS). The PFAS can include a shortchain PFAS, a long-chain PFAS, a linear PFAS, a branched PFAS, a polymeric PFAS, an oligomeric PFAS, a fluorotelomer compounds, a fluoropolymer degradation product, a GenX compound, a perfluoroalkyl sulfonate, a perfluoroalkyl carboxylate, or any combination thereof. The PFAS can also include perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorobutanesulfonic acid (PFBS), perfluorobutanoic acid (PFBA), hexafluoropropylene oxide dimer acid, or a salt thereof.

[0058] The spongy product can be included in a system that adsorbs, absorbs, ionexchanges, or removes a solute from a liquid medium. The system can include an active adsorption layer and a scavenging layer that captures leached ions, residual contaminants, competing ions, or any combination thereof.

[0059] The spongy product can be produced using an aqueous suspension including charged cellulose fibrils (e.g., cellulose nanofibers (CNFs)) or a mixture including charged cellulose fibrils and one or more additives selected from activated carbon, biochar, gelatin, cellulose sludge, lignin, chitosan, metal oxide nanoparticles, a clay, a zeolite, a nanomaterial, a carbon nanomaterial, an inorganic sorbent, an organic sorbent, a polymer, a biopolymer, a mineral filler, or combinations thereof. The mixture may be mechanically homogenized and castinto a mold of desired dimensions. The charged cellulose fibrils have a diameter in a range from about 2 nm-about 50 nm, within manufacturing and / or measurement tolerances. The charged cellulose fibrils, including CNFs, can be produced by a nitro-oxidation process (NOP) as discussed, for example, in U.S. Pat. No. 10,894,838 and in PCT Application No.PCT / US2015 / 060261, the contents of which are hereby incorporated by reference in their entirety. A NOP can use various biomass feedstocks, allowing for the utilization of both hard and softwoods, including agricultural residues.

[0060] The molded material may then be subjected to freeze-thaw processing or ice templating at a temperature of about -5°C to about -20°C for about 1 hour to about 24 hours to generate a porous precursor scaffold as shown in Fig. 5. Crosslinking agents, including multivalent metal ions or other reactive molecules, may thereafter be introduced into the scaffold and allowed to diffuse through the pore network under capillary forces. Following incubation for about 1 hour to about 72 hours at about 1°C to about 20°C, within manufacturing and / or measurement tolerances, a wet sponge product may be obtained. The wet sponge can be a HydroSponge. The wet sponge may optionally then be lyophilized or freeze dried to produce a dry, lightweight aerated sponge, while substantially preserving the porous architecture of the wet sponge. The aerated sponge can be an AeroSponge.

[0061] The resulting spongy product may exhibit high porosity, interconnected pore networks, capillary-driven liquid uptake, high internal surface area, mechanical integrity, and shape adaptability, all of which are beneficial for water purification and solute separation. Ice templating can be used to produce aligned or honeycomb-like pore structures, as shown in Fig.5 that improve permeability and mass transfer. The spongy product may be further processed into granules, powders, pellets, rods, sheets, pads, or other shaped bodies for use in batch systems, packed columns, filtration cartridges, and other treatment formats.

[0062] The term "cellulose" denotes a fibrous biomaterial ranging in size from macro to micro to nano, extractable from various biomass feedstocks and / or natural organic wastes. This cellulose can be crosslinked with several salts or other crosslinking agents to fulfill multiple objectives, such as enhancing water and solutes retention within the elastic porous networks of the spongy product.

[0063] NOPs that can be used to produce the cellulose nanofibers (CNFs) for step (i) in Fig. 1 are disclosed in U.S. Pat. No. 10,894,838 and in PCT Application No. PCT / US2015 / 060261. The NOPs can use various biomass feedstocks, allowing for the utilization of both hard and softwoods, including agricultural residues. However, softwoods with low lignin content, specifically agricultural residues, can also be used.

[0064] Cross-linking can refer to the interaction between negatively charged cellulose fibers and positively charged salt ions through electrostatic attraction. This interaction involves two particle types with opposite charges, leading to mutual attraction. Depending on the type of salt ions, such as transitional metal ions, interactions with cellulose functionalities can occur through a metal-ligand interaction. This metal-ligand interaction may involve a coordinate covalent bond, also known as a dative bond, dipolar bond, or coordinate bond. Besides salts, molecular compounds can be used to crosslink the cellulose fibers to form adsorbents of the spongy products. One or more crosslinking agents, such as genipin, chitosan, citric acid, polydopamine, lignosulfonate, etc., can be incorporated along with CNFs.

[0065] An adsorbent composition, which can be used with a wet sponge (e.g., HydroSponge) or an aerated sponge (e.g., AeroSponge) can include CNF or cellulose in the range of about 0.01 wt% to about 99.99 wt%, within manufacturing and / or measurement tolerances, combined with a salt solution in the range of about 1 mmol to about 1000 mmol, within manufacturing and / or measurement tolerances. In specific formulations, the adsorbent composition may include about 0.01 wt%-about 100 wt% cellulose % components, within manufacturing and / or measurement tolerances. Alternatively, the adsorbent composition may include cellulose in the range of about 1.0 wt%-about 10 wt%, within manufacturing and / or measurement tolerances, and cellulose components in the range of about 10 wt%-about 20 wt%, within manufacturing and / or measurement tolerances. Another variation can include cellulose in the range of about 20 wt%-about 30 wt%, within manufacturing and / or measurement tolerances, and cellulose components in the range of about 30 wt% to about 40 wt%, within manufacturing and / or measurement tolerances. In an alternate formulation, the adsorbent composition may include about 40 wt% cellulose and about 50 wt% cellulose components, within manufacturing and / or measurement tolerances. Moreover, the adsorbentcomposition may include about 50 wt% to about 100 wt% or more of additional components, within manufacturing and / or measurement tolerances, relative to the total weight of the adsorbent composition.

[0066] To achieve stable sorbents crosslinked by various ions, a cellulose content of at least about 0.25 wt% to about 1.5 wt%, within manufacturing and / or measurement tolerances, including about 1 wt% to about 5 wt%, within manufacturing and / or measurement tolerances, with about 100 mM-about 500 mM of divalent, within manufacturing and / or measurement tolerances or about 1 mM-about 200 mM of trivalent ions, within manufacturing and / or measurement tolerances, can be used.

[0067] In addition to cellulose, the sorbents may also include lignin, hemicellulose, holocellulose, proteins, and fatty acids. The specific composition of lignin depends on the feedstock used. If softwood is utilized, lignin includes coniferyl alcohol. For hardwood, the lignin includes coniferyl alcohol and sinapyl alcohol. For grass, the lignin includes three monomers: coniferyl, sinapyl, and p-coumaryl alcohol. Hemicellulose encompasses xyloglucans, xylans, mannans, glucomannans, and beta-(l-->3,l-->4)-glucans. Additionally, cellulose may contain proteins and their derivatives, such as amino acids and fatty acids depending on the used feedstocks.

[0068] The flowchart in Fig. 1 shows the production of a spongy product in a mat form, which can then be further processed into various shapes and sizes, as shown in Figs. 3A-3L and 4. The process starts by blending charged cellulose fibrils derived from diverse feedstocks. These feedstocks can include, but are not limited to, jute, bagasse, cow dung, horse dung, and food wastes. The charged cellulose fibrils can include nanocellulose, cellulose nanocrystals, cellulose nanofibrils, cellulose microfibrils, lignin-containing cellulose nanofibers, oxidized cellulose fibrils, derivatized cellulose fibrils, or any combination thereof. The charged cellulose fibrils can include cellulose fibrils including carboxyl, aldehyde, hydroxyl, sulfate, sulfonate, phosphate, phosphonate, amine, ammonium, imine, amidine, guanidinium, zwitterionic functionality, metal-coordination functionality, ion-exchangeable functionality, or any combination thereof. The charged cellulose fibrils can be produced by any suitable process, including nitro-oxidation, TEMPO-mediated oxidation, carboxymethylation, phosphorylation,sulfonation, periodate oxidation, chlorite oxidation, esterification, etherification, amidation, amination, enzymatic treatment, mechanical fibrillation, acid hydrolysis, or any combination thereof. That is, the charged cellulose fibrils can include nitro-oxidized fibrils, TEMPO-oxidized fibrils, carboxymethylated fibrils, phosphorylated fibrils, sulfonated fibrils, periodate-oxidized fibrils, chlorite-oxidized fibrils, esterified fibrils, etherified fibrils, amidated fibrils, aminated fibrils, enzymatically treated fibrils, mechanically fi bril lated fibrils, acid-hydrolyzed fibrils, or any combination thereof. An initial aqueous suspension (i) including charged cellulose fibrils is prepared. Alternatively, a mixture (ii) including an aqueous suspension including charged cellulose fibrils and additives can be prepared. The additives can include, for example, activated carbon, biochar, gelatin, cellulose sludge, lignin, chitosan, a clay, a zeolite, a nanomaterial, a carbon nanomaterial, an inorganic sorbent, an organic sorbent, a polymer, a biopolymer, a mineral filler, etc. The additives can be included in range from about 0.01 wt% to about 100 wt%, within manufacturing and / or measurement tolerances, relative to the total volume of the aqueous suspension (i).

[0069] In step (a), the aqueous suspension (i) or the mixture (ii) is introduced into a mold having the desired size and volume to form a large flat mat having width w, depth d, and length I. Additional materials can be incorporated. The additional materials can include, but are not limited to, biochar, activated carbon, nanomaterials, clays, chitosan, zeolite, other sorbents, or any combination thereof. The aqueous suspension (i) or the mixture (ii) can be mechanically mixed to create a uniform suspension / paste with evenly distributed texture in step (b).

[0070] In some example embodiments, as shown in steps (a) and (b) in Fig. 1, about 0.5 wt%-about 1 wt% of charged cellulose fibrils (e.g., CNF or cellulose fibers), within manufacturing and / or measurement tolerances, can be used. These charged cellulose fibrils can be mixed, for example, with biochar in a range from about 0.1 wt%-about 1 wt%, within manufacturing and / or measurement tolerances, or higher amounts as needed. Instead of biochar, various other adsorbents such as activated carbon, carbon nanotubes, zeolites, polymers, etc., or combinations thereof can be incorporated into the mixture. Various mixing ratio of charged cellulose fibrils to biochar or other additives can be used. For example, the mixing ratio of charged cellulose fibrils to additive(s) can be 1:1, 1:0.5, 1:2, 1:4, or other suitableratios, depending on the desired properties of the final spongy product. This flexibility in the ratio allows for customization of the different composite adsorbents to optimize performance for specific applications.

[0071] In step (a) of Fig. 1, there is an option to infuse the mixture with air bubbles or nanobubbles (air and / or oxygen) using a nanobubble generator. This infusion process is designed to engineer different pore architecture and sizes that contribute to the formation of precision pores in the wet sponge or aerated sponge. The bubbles can be charged with different surfactants in real-time to further tune or engineer the pore networks in the spongy product. Using bubbles can improve the pore volume, aeration, and water absorption capabilities of the spongy product, while also contributing to its environmentally friendly attributes. These enhancements can collectively achieve more supportive and efficient adsorbents for maximum pollutant adsorption.

[0072] In step (c), the mold undergoes a freeze-thaw process or ice templating treatment to create a porous network within the aqueous suspension (i) or the mixture (ii) to create a precursor body. This step (c) involves maintaining the mold at a desired temperature range of about -5°C to about -20°C, within manufacturing and / or measurement tolerances, for a duration of about 1 hour to about 24 hours, within manufacturing and / or measurement tolerances, and then returning the mold to room temperature. During the freeze-thaw process or ice templating treatment, the free water molecules within the molds form ice crystals.

[0073] Alternatively, the freezing duration can be significantly reduced through rapid freezing or repeated freezing techniques. These techniques include, for example, cryogenic freezing using liquid nitrogen or carbon dioxide to expose the aqueous suspension (i) or the mixture (ii) to temperatures as low as -196°C. To prevent the formation of large ice crystals, which could compromise the texture and quality of the resulting spongy product, various rapid freezing techniques can be employed, which can include acoustic freezing, flash freezing, quench cooling, immersion freezing, vapor compression freezing, plate freezing, blast freezing, spray freezing, or cryo-milling and supercooling to rapidly freeze the aqueous suspension (i) or the mixture (ii) in a controlled manner. These techniques ensure rapid and uniform freezing,preserving the integrity and quality of the charged cellulose fibrils or other fibers mixture within the resulting spongy product.

[0074] In the subsequent step (d), a crosslinked structure can be formed of the porous network using a crosslinking agent. The crosslinked structure can define a three-dimensional scaffold. As shown in Fig. 1, a crosslinking agent (iv) is applied to the top of the mats, or the mats are suspended in an ionic solution or a solution including the crosslinking agent. If the crosslinking agent is introduced on the top surface of the mats, then the ions of the crosslinking agent migrate through the pores in the three-dimensional scaffold of charged cellulose fibrils via diffusion, enhanced by the capillary forces inherent in the charged cellulose fibrils in the mat. The three-dimensional scaffold can be configured as a cationic sponge adsorbent, an anionic sponge adsorbent, an amphoteric sponge adsorbent, a zwitterionic sponge adsorbent, or a spongy product including both anionic and cationic adsorption sites. The three-dimensional scaffold can be crosslinked such that the three-dimensional scaffold includes cationic functionality and / or affinity to define a cationic sponge adsorbent or such that the three-dimensional scaffold includes anionic functionality and / or affinity to define an anionic sponge adsorbent. Cationic affinity means the three-dimensional scaffold preferentially adsorbs cations, and anionic affinity means that the three-dimensional scaffold preferentially adsorbs anions. The three-dimensional scaffold can define a hydrated sponge, a hydrogel sponge, a water-loaded sponge, a dry sponge, an aerated sponge, an aerogel sponge, or any combination thereof. The resulting dry-sponge products can exhibit high porosity, elasticity, water retention, drainage, reabsorption, permeability, and fast pollutant diffusion in aqueous environments. And the resulting aerated-sponge products can exhibit ultra-lightweight character, high porosity, enhanced mechanical strength, and rapid adsorption in aqueous environments. The three-dimensional scaffold can include an interconnected pore structure, an open-cell structure, aligned pores, lamellar pores, gradient pores, directional pores, a honeycomb microstructure, or any combination thereof. The three-dimensional scaffold can have capillary uptake, compressibility, poroelasticity, squeezability, reusability, elasticity, resiliency, shape recovery, or any combination thereof.

[0075] The crosslinking agent can include ions or salts, including ions with valences of +1, +2, and +3, or any combination thereof. The crosslinking agent can include a hydrogen bonding crosslinking agent and / or a metal ionic crosslinking agent.

[0076] The hydrogen bonding crosslinking agent can include, for example, urea, citric acid, genipin, chitosan, polydopamine, lignosulfonate, polyethylene glycol, carboxyl-functionalized polymers or oligomers (e.g., polyacrylic acid), polyvinyl alcohol, polyamide, supramolecular crosslinkers (e.g., ureidopyrimidone), tannic acid, polyphenols, and their derivatives. These hydrogen bonding crosslinking agents, and similar types, can be applied in the form of a solution or granules, powder, pills, or equivalent forms.

[0077] The metal ionic crosslinking agent can include monovalent (+1), divalent (+2), and trivalent (+3) salts. These salts include, for example, potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), aluminum (Al), manganese (Mn), zinc (Zn), copper (Cu), molybdenum (Mo), nitrogen (N), phosphorus (P), sulfur (S), boron (B), chlorine (Cl), nickel (Ni)-based salt ions, or any combination thereof. These salts, and similar types, can be applied in the form of solution or granules, powder, prills, or equivalent forms.

[0078] Submerging frozen charged cellulose fibrils (e.g., CNFs) in an ionic solution or a solution including crosslinking agents can achieve uniform distribution and effective integration of ions or crosslinking agents within the mats.

[0079] To achieve comprehensive distribution and effective integration of the ions and / or crosslinking agents within the precursor body, in step (e), incubation is performed. The incubation step (e) can be maintained for a period of about 1 hour to about 72 hours, within manufacturing and / or measurement tolerances, during the thawing process, which can occur at room temperature, refrigerated in a range from about 0°C-about 10°C, or in a range from about l°C-about 20°C, within manufacturing and / or measurement tolerances, or at freezing temperatures (<0°C). The incubation step (e), whether at room temperature or under refrigerated conditions (<0°C or about 1°C to about 10°C, within manufacturing and / or measurement tolerances), stabilizes the structures, including the three-dimensional scaffold, within the spongy product, ensuring the mechanical integrity and functional performance of thefinal spongy products. This step (e) supports the structural stability and uniformity of a wet sponge or an aerated sponge.

[0080] After the crosslinking reactions, wet spongy products are produced. In step (f), the products prepared in step (e) are subjected to a lyophilization process or freeze-drying to rapidly remove moisture and to form dry aerogel structures. Step (e) transforms a wet sponge into an aerated counterpart (i.e., an aerated sponge), while retaining the structural integrity but becoming very lightweight.

[0081] Figs. 2A and 2B show the preparation of a large-scale wet-sponge mat, based on a mixture of CNFs (prepared by a NOP using raw jute as a feedstock) and biochar. In (a), an initial preparation of 300 grams of a blend containing 0.8% CNF by weight and biochar in a 1:2 ratio is poured into a medium-sized silicon mold (e.g., >200 mm in length). The mat having a thickness of 0.4 inches-0.5 inches is then frozen at -20°C for 20 hours, solidifying the mat's structure and preparing the mat for infusion with a crosslinking agent. In (b), after freezing, 25 mL of a 200 mM calcium nitrate (CafNOsh) solution is added to the mat. In (c), the mat is left for several days to allow the calcium ions to diffuse thoroughly through the mat's structure to ensure proper crosslinking of the ionic content and the structural integrity of the mat, as depicted by the ion diffusion (ln) process shown in Fig. 1.

[0082] Figs. 3A-3L show the processing of the spongy product into various shapes and forms, tailored to their intended applications, handling requirements, and adsorption efficiency. Figs. 3A and 3G show a spongy product having a circular shape. Figs. 3B and 3H show a spongy product with a cubic shape. Figs. 3C and 31 show a spongy product with a dome shape. Figs. 3D and 3J show a spongy product with a cylindrical shape with a dimple on one end. Figs.3E and 3K show a spongy product with a hollow cylindrical shape. Figs. 3F and 3L show a spongy product with a hexagonal shape.

[0083] Fig. 4 shows spongy products with various shapes, such as: (1) granular with irregular or round shape (sizes typically ranging from about 0.2 mm to about 5 mm, within manufacturing and / or measurement tolerances), which can then be further processed into a powder form through shredding or grinding; (2) powders (with sizes smaller than about 0.18 mm, within manufacturing and / or measurement tolerances, which can be collected using amesh size ~200+ filter); (3) cylindrical pellets or rods, which can be produced with a diameter of about 1 mm-about 5 mm, within manufacturing and / or measurement tolerances, using a cylindrical mold. These spongy products can have honeycomb microstructures that can be created using, for example, ice templating.

[0084] In addition to water purification, the spongy products can be used for other applications, such as air purification, gas separation, other liquid and gas applications in pharmaceuticals, food processing, gas-phase adsorption, solvent recovery, and catalysis, chromatography, automotive catalytic converters, VOC removal, industrial gas purification, desiccants (e.g., silica gel, molecular sieves), ion exchange resins, catalyst support, protective clothing, face masks, and hybrid applications like supported catalysts, functionalized coatings, and industrial filtration.

[0085] Fig. 5 is an SEM image showing sheet-like structures that are wrapped around each other, creating a range of pore sizes that facilitate the accommodation of different solutes based on their size and shape.

[0086] The above processes can be used to produce an anionic spongy product including charged cellulose fibrils that can be used for the removal of cationic pollutants. The charged cellulose fibrils (e.g., carboxylated CNFs) may be formed into a porous three-dimensional scaffold and structurally stabilized by hydrogen-bonding crosslinking agents and / or other non-covalent interactions, including hydrogen bonding, fibril entanglement, capillary consolidation, and freeze-thaw structuring, such that the three-dimensional scaffold substantially preserves its anionic nature. The retained carboxylate functionalities of the CNFs in the three-dimensional scaffold provide negatively charged sites capable of binding to cationic pollutants through electrostatic attraction, complexation, coordination, and / or ion exchange. The resulting anionic spongy product may possess high porosity, interconnected pore channels, and accessible carboxyl groups, and may therefore be used for removal of cationic dyes, metal ions, radionuclides, and other positively charged solutes.

[0087] Alternatively, the above processes can be used to produce a cationic spongy product including charged cellulose fibrils that can be used for the removal of anionic pollutants. The charged cellulose fibrils (e.g., carboxylated CNFs) may be formed into a porous three-dimensional scaffold and can be crosslinked with divalent ionic species to provide structural stability, while preserving sufficient anionic functionality for capture of cationic pollutants. The divalent ionic species may be displaced, exchanged, or supplemented by higher-valence cationic pollutants, including trivalent pollutants, thereby enabling selective uptake through ion-exchange and / or coordination mechanisms.

[0088] The crosslinking agents can include hydrogen-bonding crosslinking agents and / or other non-covalent structural stabilizers configured to provide structural integrity to the three-dimensional scaffold including the charged cellulose fibrils (e.g., carboxylated CNFs) without substantially neutralizing the carboxylate functionalities thereof. Suitable hydrogen-bonding crosslinking agents may include urea, citric acid, genipin, chitosan, polydopamine, lignosulfonate, polyethylene glycol, carboxyl-functionalized polymers or oligomers (e.g., polyacrylic acid), polyvinyl alcohol, polyamides, supramolecular crosslinkers (e.g., ureidopyrimidone), tannic acid, polyphenols, derivatives thereof, and combinations thereof. These crosslinking agents may be introduced in solution form or as granules, powders, pellets, tablets, or other suitable forms. These crosslinking agents can structurally stabilize the three-dimensional scaffold, while substantially preserving the three-dimensional scaffold's anionic or cationic nature, thereby yielding an anionic or cationic spongy product effective for removal of cationic or anionic pollutants.

[0089] Example 1 includes an anionic wet-sponge adsorbent for removal of cationic pollutants. Non-crosslinked wet-sponge adsorbents were prepared as shown in Fig. 6 from a 1 wt% carboxylated CNF suspension for adsorption of cationic heavy metals. A 10-mL aliquot of the suspension was subjected to four freeze-thaw cycles, each including freezing at about -16°C to about -20°C for about 24 hours and thawing at room temperature for about 8 hours to about 9 hours. The resulting stable wet-sponge structures were tested for adsorption of Pb2+and Cd2+. As shown in Figs. 9 and 10, non-linear Langmuir, Freundlich, and Sips isotherm models were used to measure the maximum adsorption capacities Qmax of about 845.82 mg / g for Pb2+and about 823.61 mg / g for Cd2+.

[0090] Example 2 includes a cationic wet-sponge adsorbent for removal of anionic pollutants. The ionic crosslinking agents can include divalent and trivalent metal salts capable ofimparting cationic functionality to the three-dimensional scaffold including carboxylated CNFs. Suitable salts may include calcium (Ca), magnesium (Mg), iron (Fe), aluminum (Al), zinc (Zn), manganese (Mn), or any combination thereof. Iron- and aluminum-containing salts can be used to prepare cationic spongy products for adsorption of anionic water pollutants. These salts may be provided in solution form or as granules, powders, pellets, tablets, or other suitable forms. The resulting crosslinked three-dimensional scaffold may function as a cationic adsorbent for removal of anionic contaminants through adsorption and / or ion-exchange interactions.

[0091] Example 3 includes an ionically crosslinked wet-sponge adsorbent as shown in Fig. 7 from a l-wt.% carboxylated-CNF aqueous suspension for adsorption of anionic pollutants. A 10-mL aliquot of the aqueous suspension was frozen at about -16°C to about -20°C for about 24 hours and processed through four freeze-thaw cycles to form a porous three-dimensional scaffold. The three-dimensional scaffold was then crosslinked in a 50-mM solution including Fe3+ions or Al3+ions for about 24 hours, followed by washing with deionized water. The resulting stable crosslinked wet-sponge material were tested for arsenite adsorption, yielding maximum adsorption capacities of about 328.38 mg / g for Fe3+-crosslinked wet sponge and about 215.55 mg / g for Al3+-crosslinked wet sponge as shown in Figs. 11 and 12.

[0092] Example 4 uses of wet-sponge adsorbents in batch and continuous-flow water treatment systems. The sponge adsorbents may be used as floating sorbents in batch treatment systems as shown in Figs. 7 and 8 or packed into cartridges as shown in Fig. 8 for continuous-flow filtration and solute separation. As floating sorbents, the sponge materials may be introduced directly into a contaminated liquid, where the porous and lightweight structure of the sponge materials enables buoyancy, fluid uptake, and adsorption of target contaminants, followed by removal of the sponge from the treated liquid.

[0093] The sponge adsorbents may be packed into a filter cartridge or column. For example, a gravity-fed water filter cartridge can include a lower scavenging layer and an upper active treatment layer as shown in Fig. 8. The lower layer includes physically crosslinked cellulose wet sponges mixed with activated carbon and functioned to capture any leached cationic species. The upper layer includes Fe3+-crosslinked carboxylated CNF-based wet sponges that serves as the primary adsorptive medium for removal of arsenite from an aqueous feed stream. Thecontaminated solution was placed in an upper reservoir and allowed to pass continuously through the cartridge under gravity-driven flow. Multiple filtration cycles may be performed to assess durability, reusability, and contaminant-removal performance, with filtered effluent analyzed to determine removal efficiency and cation scavenging performance.

[0094] Example 5 includes a multilayer cartridge including wet-sponge adsorbents for continuous removal of arsenite and for trapping of secondary ion leaching. The multilayer cartridge can be sealed and can be used to treat an aqueous arsenite (AsO^~) solution having an initial concentration of 100 ppm. Four consecutive filtration cycles were performed using fresh arsenite solutions of the same concentration as shown in Fig. 13 and in Table 1 below. Effluent collected from each cycle was analyzed by inductively coupled plasma - optical emission spectroscopy (ICP-OES). The multilayer cartridge removed about 88.3% of arsenite in the first cycle, about 82.6% in the second cycle, about 31.0% in the third cycle, and about 68.3% in the fourth cycle, demonstrating multi-cycle contaminant removal and secondary scavenging capability.Table 1Table 1 shows initial arseniteconcentrations (ppm), remaining concentrations (ppm), and removal percentage for each cycle of the reuse experiment using the same multilayer cartridge.

[0095] Example 6 shows batch adsorption and wet-sponge selectivity in the presence of competing anions. A competitive batch adsorption experiment was performed to evaluate the selectivity of chemically crosslinked wet-sponge adsorbents in the presence of competing anions as shown in Fig. 14. Mixed aqueous solutions containing arsenite, phosphate, and sulfate were prepared with each ion having an initial concentration of 500 ppm. Fe3+-crosslinked and Al3+-crosslinked wet-sponge materials were prepared from 10 mL of a l-wt% carboxylated CNFsuspension, frozen at about -16°C to about -20°C for about 24 hours, crosslinked in 50-mM metal-ion solutions, and washed with deionized water. Each crosslinked wet sponge was placed into 50 mL of the mixed-anion solution and agitated by orbital shaking at room temperature for about 24 hours. Following equilibration, the remaining ion concentrations were analyzed by ICP-OES. The results showed that the phosphate reduced the arsenite adsorption capacity of the sponges under competitive conditions. As can be seen in Fig. 14, the Fe3+-crosslinked wet sponge achieved an arsenite removal efficiency of about 33.2%, while the Al3+-crosslinked wet sponge achieved an arsenite removal efficiency of about 15.4%, indicating stronger arsenite selectivity for the Fe3+-crosslinked wet sponge.

[0096] Example 7 uses wet-sponge adsorbents to remove PFAS Compounds. Fe3+-crosslinked wet-sponge adsorbents were evaluated for adsorption of: perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorobutanesulfonic acid (PFBS) and perfluorobutanoic acid (PFBA). A carboxylated CNF suspension was introduced into a silicone mold, frozen at about -20°C for about 24 hours, and crosslinked in a Fe3+ion bath having a concentration of about 100 mM to about 500 mM for about 1 to about 3 days at about 5°C to about 25°C, within manufacturing and / or measurement tolerances. The resulting wet-sponge samples were weighed and placed in centrifuge tubes containing about 5 ppm PFAS solution, followed by orbital shaking at about 120 rpm. Aliquots were withdrawn and analyzed by liquid chromatography - tandem mass spectrometry (LC-MS / MS). As shown in Fig. 15, the Fe3+-crosslinked wet sponge removed about 50% of PFBS and PFBA after about 2 hours, while adsorption of PFOA and PFOS was negligible under the test conditions.

[0097] Example 8 uses a CNF / gelatin / activated carbon composite wet-sponge adsorbents for removal of PFAS Compounds. CNF / gelatin / activated carbon composite wet-sponge adsorbents were prepared and evaluated for removal of PFOS, PFOA, PFBS, and PFBA under column-flow conditions. A homogeneous suspension containing CNF, gelatin, and activated carbon was introduced into a silicone mold, frozen at about -20°C for about 24 hours, and crosslinked in a 50-mM Fe3+bath for about 1 to about 3 days at about 5°C to about 25°C, within manufacturing and / or measurement tolerances. The resulting adsorbents were packed into filtration columns, and aqueous PFAS solutions having concentrations of about 5 ppm werepassed through the columns. Eluent fractions were collected over time and analyzed by LC-MS / MS. The Fe3+-crosslinked CNF / gelatin / activated carbon wet-sponge columns removed about 90% of both short-chain and long-chain PFAS within about 3 hours as shown in Fig. 16, with adsorption values of about 93.8% for PFBS, 90.1% for PFOS, 86.9% for PFOA, and 82.1% for PFBA as shown in Fig. 16. Approximately 50% adsorption was observed within about 30 minutes for all tested PFAS compounds. The poroelastic behavior of the wet-sponge adsorbents demonstrates improved reusability as shown in Fig. 17. A CNF / gelatin wet sponge containing 0.5 wt.% activated carbon and crosslinked with 50-mM Fe3+can be compressed to remove absorbed water and subsequently reswell to substantially its original shape upon submersion in water. This reversible deformation indicates retention of structural integrity and supports repeated use in adsorption applications.

[0098] Example 9 includes adsorption of dyes at different concentrations using an aerated sponge. Basacryl Red GL dye solutions were prepared at initial concentrations of 2, 4, 6, 8, and 10 ppm. In each experiment, approximately 50 mL of dye solution was treated with 0.25 g of aerated sponge and stirred for 24 hours. Following treatment, the adsorption percentage was determined for each concentration. The aerated sponges exhibited adsorption values of about 93.27%, 87.27%, 82.92%, 78.27%, and 77.50% for 2, 4, 6, 8, and 10 ppm, respectively, demonstrating effective dye removal over the tested concentration range.

[0099] It should be understood that the foregoing description is only illustrative of the present invention. Various alternatives and modifications can be devised by those skilled in the art without departing from the present invention. Accordingly, the present invention is intended to embrace all such alternatives, modifications, and variances that fall within the scope of the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A spongy product comprising a three-dimensional scaffold that includes charged cellulose fibrils and that is configured to adsorb, absorb, ion-exchange, or remove a solute from a liquid medium, when the spongy product is added to the liquid medium, wherein the charged cellulose fibrils have a diameter in a range from about 2 nm-about 50 nm.

2. The spongy product of claim 1, wherein the charged cellulose fibrils include nanocellulose, cellulose nanocrystals, cellulose nanofibrils, cellulose microfibrils, lignincontaining cellulose nanofibers, oxidized cellulose fibrils, derivatized cellulose fibrils, or any combination thereof.

3. The spongy product of claim 1 or 2, wherein the charged cellulose fibrils include cellulose fibrils including carboxyl, aldehyde, hydroxyl, sulfate, sulfonate, phosphate, phosphonate, amine, ammonium, imine, amidine, guanidinium, zwitterionic functionality, metal-coordination functionality, ion-exchangeable functionality, or any combination thereof.

4. The spongy product of one of claims 1-3, wherein the charged cellulose fibrils include nitro-oxidized fibrils, TEMPO-oxidized fibrils, carboxymethylated fibrils, phosphorylated fibrils, sulfonated fibrils, periodate-oxidized fibrils, chlorite-oxidized fibrils, esterified fibrils, etherified fibrils, amidated fibrils, aminated fibrils, enzymatically treated fibrils, mechanically f i b ri Hated fibrils, acid-hydrolyzed fibrils, or any combination thereof.

5. The spongy product of one of claims 1-4, wherein the three-dimensional scaffold is configured as a cationic sponge adsorbent, an anionic sponge adsorbent, an amphoteric sponge adsorbent, a zwitterionic sponge adsorbent, or a spongy product including both anionic and cationic adsorption sites.

6. The spongy product of one of claims 1-4, wherein the three-dimensional scaffold is crosslinked such that the three-dimensional scaffold includes cationic functionality and / or affinity to define a cationic sponge adsorbent.

7. The spongy product of claim 6, wherein the three-dimensional scaffold is crosslinked with a divalent ion, a trivalent ion, or any combination thereof.

8. The spongy product of claim 7, wherein the three-dimensional scaffold is crosslinked with calcium, magnesium, zinc, manganese, copper, iron, aluminum, nickel, cobalt, molybdenum, a rare earth metal, or any combination thereof.

9. The spongy product of claim 7 or 8, wherein the three-dimensional scaffold is crosslinked with Fe3+, Al3+, Ca2+, Mg2+, Zn2+, or any combination thereof.

10. The spongy product of one of claims 1-4, wherein the three-dimensional scaffold is crosslinked such that the three-dimensional scaffold includes anionic functionality and / or affinity to define an anionic sponge adsorbent.

11. The spongy product of claim 10, wherein the three-dimensional scaffold is stabilized by hydrogen bonding, fibril entanglement, a hydrogen-bonding crosslinking agent, or any combination thereof.

12. The spongy product of claim 10 or 11, wherein the three-dimensional scaffold includes a hydrogen-bonding crosslinking agent and / or a non-covalent stabilizer.

13. The spongy product of claim 12, wherein the hydrogen-bonding crosslinking agent and / or the non-covalent stabilizer includes urea, citric acid, genipin, chitosan, polydopamine, lignosulfonate, polyethylene glycol, carboxyl-functionalized polymers or oligomers, polyacrylicacid, polyvinyl alcohol, polyamides, ureidopyrimidone-containing materials, tannic acid, polyphenols, derivatives thereof, or any combination thereof.

14. The spongy product of one of claims 1-13, wherein the three-dimensional scaffold defines a hydrated sponge, a hydrogel sponge, a water-loaded sponge, a dry sponge, an aerated sponge, an aerogel sponge, or any combination thereof.

15. The spongy product of one of claims 1-14, wherein the three-dimensional scaffold defines an interconnected pore structure, an open-cell structure, aligned pores, lamellar pores, gradient pores, directional pores, a honeycomb microstructure, or any combination thereof.

16. The spongy product of one of claims 1-15, wherein the solute includes a cationic pollutant, an anionic pollutant, an amphoteric pollutant, a neutral pollutant, an organic pollutant, an inorganic pollutant, a biological pollutant, or any combination thereof.

17. The spongy product of one of claims 1-16, wherein the solute includes a heavy metal, a metal ion, a radionuclide, an oxyanion, an inorganic salt, a nutrient, a cationic dye, an anionic dye, a neutral dye, a pharmaceutical, an endocrine disrupting compound, a pesticide, a herbicide, a surfactant, a plastic, a microplastic, a nanoplastic, an engineered nanomaterial, a pathogen, a biomolecule, a protein, a microorganism, a toxin, or any combination thereof.

18. The spongy product of one of claims 1-16, wherein the solute includes a per- and polyfluoroalkyl substance (PFAS).

19. The spongy product of claim 18, wherein the PFAS includes a short-chain PFAS, a long-chain PFAS, a linear PFAS, a branched PFAS, a polymeric PFAS, an oligomeric PFAS, a fluorotelomer compounds, a fluoropolymer degradation product, a GenX compound, a perfluoroalkyl sulfonate, a perfluoroalkyl carboxylate, or any combination thereof.

20. The spongy product of claim 18, wherein the PFAS includes perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorobutanesulfonic acid (PFBS), perfluorobutanoic acid (PFBA), hexafluoropropylene oxide dimer acid, or a salt thereof.

21. The spongy product of one of claims 1-20, further comprising activated carbon, biochar, gelatin, cellulose sludge, lignin, chitosan, metal oxide nanoparticles, a clay, a zeolite, a nanomaterial, a carbon nanomaterial, an inorganic sorbent, an organic sorbent, a polymer, a biopolymer, a mineral filler, or any combination thereof.

22. A method of manufacturing a spongy product comprising:providing an aqueous suspension including charged cellulose fibrils;forming the aqueous suspension into a precursor body;freezing the precursor body to form a porous network within the precursor body; crosslinking the porous network to form a crosslinked structure within the precursor body; andincubating the precursor body including the crosslinked structure to form the spongy product.

23. The method of claim 22, further comprising subjecting the precursor body to one or more freeze-thaw cycles or to ice templating.

24. The method of claim 22 or 23, further comprising, after incubating the precursor body including the crosslinked structure, drying, freeze-drying, solvent exchanging, or lyophilizing the crosslinked structure to form the spongy product.

25. The method of one of claims 22-24, wherein crosslinking the porous network includes using an ionic crosslinking agent, a hydrogen-bonding crosslinking agent, a covalent crosslinking agent, a non-covalent stabilizer, or any combination thereof.

26. A method of removing a pollutant from a liquid medium comprising contacting the liquid medium with the spongy product of one of claims 1-21 in batch mode, floating mode, immersion mode, gravity-fed mode, continuous-flow mode, cartridge mode, packed-bed mode, column mode, membrane-assisted mode, or any combination thereof, to remove the pollutant from the liquid medium.

27. The method of claim 26, wherein the pollutant includes a cationic pollutant, an anionic pollutant, an amphoteric pollutant, an organic pollutant, an inorganic pollutant, a per-and polyfluoroalkyl substance (PFAS), or any combination thereof.

28. A system comprising the spongy product of one of claims 1-21, wherein the spongy product is configured as a mat, a sheet, a pad, a slab, a block, a monolith, a membrane body, a cartridge insert, a filter insert, a floating sorbent, a granular medium, a powder, a pellet, a rod, a cylinder, a bead, a shredded fragment, a rolled body, a folded body, a honeycomb body, a vertical adsorbent body, a layered article, a multilayer article, or any combination thereof.

29. The system of claim 28, further comprising an active adsorption layer and a scavenging layer configured to capture leached ions, residual contaminants, competing ions, or any combination thereof.

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