Methods and systems for making electrically conductive composites, fabrics, and textiles

Abstract

Devices, methods and systems for producing functional textiles and electrically conductive composites including for electro-thermal membrane distillation using a reduced graphene oxide (rGO) coated membrane. The method includes introducing a feed solution to a membrane distillation module including rGO-coated membranes. The methods also includes applying a controlled voltage to the rGO-coated membrane. The method also includes generating joule heating. The joule heating locally heats the feed solution. The method also includes adjusting the controlled voltage. The method also includes volatilizing the target elements. The method also includes, responsive to the volatizing of the target elements, separating the target elements from the feed solution. The methods and systems producing functional textiles usable for electrochemical distillation of complex mixtures and for healthcare applications based on antimicrobial activity.

Description

METHODS AND SYSTEMS FOR MAKING ELECTRICALLY CONDUCTIVE COMPOSITES, FABRICS, AND TEXTILESCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims the benefit of U.S. Provisional Application No. 63 / 519,241, titled “METHODS AND SYSTEMS FOR MAKING ELECTRICALLY CONDUCTIVE COMPOSITES, FABRICS, AND TEXTILES” filed August 12, 2023, the content of which is incorporated herein by reference in its entirety for all purposes.TECHNICAL FIELD

[0002] The present disclosure relates to sustainable devices, methods, and systems for the recovery of ammonia. More specifically, the present disclosure relates to electro-thermally driven membrane distillation for targeted elements including ammonia recovery.

[0003] Moreover, the present disclosure relates to the field of wastewater treatment and nutrient recovery, specifically to the selective separation of nitrogen-based nutrients from wastewater.

[0004] Moreover, the present disclosure relates to the systems and methods of using a reduced graphene oxide (rGO) membrane with joule heating capabilities to electro-thermally drive membrane distillation.GOVERNMENT INTEREST

[0005] This work was funded by the National Science Foundation, EEC Division of Engineering Education and Centers, NSF Engineering Research Center for Advancing Sustainable and Distributed Fertilizer production (CASFER), NSF 20-553 Gen-4 Engineering Research Centers award # 2133576.BACKGROUND

[0006] Nitrogen-based nutrients, such as aqua ammonia (NH3), are often present in wastewater at concentrations of at least 10% weight in nitrogen. However, current ammonia recovery methods, including air stripping and biological methods, face limitations in terms of low removal efficiencies, slow rates, and the inability to effectively recover valuable ammonia in a cost and energetically effective manner.

[0007] Membrane distillation, a thermally driven membrane separation process, has shown promise for desalination applications. Yet, it remains unexplored in the context of ammonia removal. To address this, the present invention proposes an innovative electro-thermally driven membrane distillation system that utilizes reduced graphene oxide (rGO) coated membranes to enhance the ammonia separation process.

[0008] Current ammonia recovery methods, like air stripping, filtration and biological methods are often limited by low removal efficiencies, slow rates, and the inability to effectively recover valuable ammonia in a cost and energetically effective way. Therefore, there is a need to explore ammonia recovery methods that are cost effective, but still have high efficiency for removal.

[0009] Further, smart multifunctional textiles have drawn tremendous interest because of their potential applications in the fields of healthcare, Joule-heaters, wearable sensors, and motion detectors. A critical requirement for smart textiles is electric conductivity. However, textile substrates are inherently electrically insulated making them unsuitable for use in electronic devices. Therefore, the main challenge in developing multifunctional textiles lies in successfully integrating electrical conductivity into the fabrics.

[0010] Graphene, a honeycomb-shaped two-dimensional material with a sp2carbon structure, possesses superior electrical and thermal conductivity, robust mechanical strength, and large surface-active sites. Furthermore, graphene materials offer antimicrobial properties through acombination of membrane stress, generation of oxidative stress, trapping effect, and photothermal activity. However, graphene and its derivatives typically require a prolonged exposure time to effectively kill or inactivate microorganisms through these mechanisms.

[0011] Prior studies on Joule-heating performance of graphene-coated fabrics involved multiple steps, various reagents, and high voltages to achieve elevated temperatures. Therefore, it is crucial to explore simpler techniques for preparing graphene-coated fabrics that exhibit high-temperature under low voltages, ensuring both human safety and energy efficiency.SUMMARY OF THE INVENTION

[0012] The present disclosure relates to methods and systems for removal of target elements, such as for example ammonia, using electro-thermally driven rGO membrane distillation.

[0013] In general embodiments of the present disclosure, the method for electro-thermal membrane distillation includes introducing a feed solution to a membrane distillation module including rGO-coated membranes. The method also includes applying a controlled voltage to the rGO-coated membrane. The method also includes generating joule heating. The joule heating locally heats the feed solution. The method also includes adjusting the controlled voltage. The method also includes volatilizing target elements in the feed solution. The method also includes, responsive to the volatizing of the target elements, separating the target elements from the feed solution.

[0014] In other general embodiments of the present disclosure, the method for preparing reduced graphene oxide-coated fabrics includes spray-coating fabrics with graphene oxide water dispersion, where the spray coating creates an even coating layer of the graphene oxide on the fabrics. The method also includes electro-chemically reducing the graphene oxide layer on the fabric using a three-electrode system. The method also includes washing the fabrics, where washing the fabrics removes sodium chloride. The method also includes drying the fabrics. The method also includes retrieving the fabrics, where the fabrics are coated in thereduced graphene oxide.

[0015] In general embodiments of the present disclosure, the method includes producing functional textiles and electrically conductive composites using layer by layer coating.

[0016] In general embodiments of the present disclosure, the method includes the application of functional textiles for the electrochemical distillation of complex mixtures.

[0017] In general embodiments of the present disclosure, the method includes the application of functional textiles for healthcare based on the antimicrobial activity of the fabrics and capacity for wound healing.BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Other advantages of the present invention will be apparent from the following detailed description of the invention in conjunction with embodiments as illustrated in the accompanying drawings, in which:

[0019] FIG. 1 depicts a schematic presentation of electro-thermally driven distillation with smart fibers, in accordance with certain embodiments of the present disclosure.

[0020] FIG. 2 depicts a schematic view of the preparation procedure of the rGO-coated fabrics, in accordance with certain embodiments of the present disclosure.

[0021] FIG. 3 depicts a schematic representation of the fabric’ s connection to the power supply and thermometer for investigating its electro-thermal performance, in accordance with certain embodiments of the present disclosure.

[0022] FIG. 4 depicts a table of samples with different rGO loadings and their corresponding resistance and electronic conductivity in accordance with a working example of the present disclosure.

[0023] FIG. 5 depicts a schematic illustration of the potential effect of increasing the rGO loading on the formation of a more continuous graphene network with increased number ofconnection points between graphene nanosheets, in accordance with certain embodiments of the present disclosure.

[0024] FIG. 6 depicts the Raman spectra of the rGO-coated fabrics with different loading levels, in accordance with certain embodiments of the present disclosure.

[0025] FIGS. 7A-7O depict the surface morphology of the samples with different rGO loadings, in accordance with certain embodiments of the present disclosure.

[0026] FIG. 8 depicts the TGA results of the control and samples, in accordance with certain embodiments of the present disclosure, presenting the residual weight percentage as a function of temperature.

[0027] FIG. 9 depicts the characteristics of the thermal decompositions observed in the samples of the working example.

[0028] FIG. 10 depicts the V-I curves for each sample of varying rGO loading under different DC voltages, in accordance with certain embodiments of the present disclosure.

[0029] FIG. 11A-11D depict the temperature profile vs. time under different applied voltages for the samples, in accordance with certain embodiments of the present disclosure.

[0030] FIG. 12 depicts the repeatability of the Joule-heating effect in the rGO-coated fabric under 9V, observed in the samples of the working example.

[0031] FIG. 13 depicts the distribution of B. subtilis colonies on agar plates over time, in accordance with certain embodiments of the present disclosure.

[0032] FIG. 14 depicts the temperature profile of the fabric surface for 300 seconds application of 9 V of the antibacterial test, in accordance with certain embodiments of the present disclosure.

[0033] FIGS. 15A-5E depict agar plates demonstrating the number of recovered colonies after each test of the working example, with FIG. 15A showing a control plate, FIG. 15B showing rGO-coated fabric no voltage, FIG. 15C showing rGO-coated fabric 1.9 V, FIG. 15D showingrGO-coated fabric 3.7 V, and FIG. 15E showing rGO-coated fabric 6.3 V, in accordance with certain embodiments of the present disclosure.

[0034] FIG. 16 depicts the temperature profiles of different voltages applied to the fabric, in accordance with certain embodiments of the present disclosure.

[0035] FIGS. 17A-17C depict SEM images of B. subtilis cells on a control group of pristine fabric without current. FIGS. 17D-17F depict SEM images of B. subtilis cells on the rGO- coated fabric subjected to a voltage of 9V for 300 seconds, in accordance with certain embodiments of the present disclosure.

[0036] FIG. 18 depicts the results on repeatability of the antibacterial performance of the rGO- coated fabric under 9V, in accordance with certain embodiments of the present disclosure.DETAILED DESCRIPTION

[0037] The disclosure provides sustainable devices, methods, and systems for electro-thermal removal of ammonia that can help solve the problems of the prior art by introducing a novel device, method, and system for electro-thermally driven rGO membrane distillation.

[0038] Unless clearly defined otherwise from the context, any range of values presented in the following Detailed Description and Claims includes each end point as well as each whole number or fractional part thereof, within the recited range. Additionally, approximating language may be applied to modify any quantitative representation that may vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about” and “substantially,” may not be limited to the precise value specified. By way of example, a range from “about 0.8 nm to about 50 nm,” includes for example, 0.8 nm, 0.9 nm, 1 nm, 3 nm, 3.14 nm, 49.999 nm, 50 nm, etc., and may include values slightly below 0.8 nm and slightly above 50 nm.

[0039] Various terms are used to refer to particular system components. Different companies may refer to a component by different names - this document does not intend to distinguishbetween components that differ in name but not function. In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . ” Also, the term “couple” or“couples” is intended to mean either an indirect or a direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection or through an indirect connection via other devices and connections.

[0040] The terminology used herein is for the purpose of describing particular example embodiments only, and is not intended to be limiting. Following long-standing patent law convention, the terms “a” and “an” mean “one or more” when used in this application, including the claims.

[0041] As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed.

[0042] The terms first, second, third, etc., may be used herein to describe various elements, components, regions, layers and / or sections; however, these elements, components, regions, layers and / or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer, or section from another region, layer, or section. Terms such as “first,” “second,” and other numerical terms, when used herein, do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer, or section discussed below could be termed a second element, component, region, layer, or section without departing from the teachings of the example embodiments. The phrase “at least one of,” when used with a list of items, means that differentcombinations of one or more of the listed items may be used, and only one item in the list may be needed. As used herein, the term “and / or” when used in the context of a listing of entities, refers to the entities being present singly or in combination. Thus, for example, the phrase “A, B, C, and / or D” includes A, B, C, and D individually, but also includes any and all combinations and subcombinations of A, B, C, and D. Accordingly, as an example, “at least one of: A, B, and C” includes any of the following combinations: A, B, C, A and B, A and C, B and C, and A and B and C. In another example, the phrase “one or more” when used with a list of items means there may be one item or any suitable number of items exceeding one.

[0043] Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper,” “top,” “bottom,” and the like, may be used herein. These spatially relative terms can be used for ease of description to describe one element’s or feature’s relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms may also be intended to encompass different orientations of the device in use, or operation, in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptions used herein interpreted accordingly.

[0044] Unless otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in this specification are approximations that can vary depending upon the desired properties sought to be obtained by the presently disclosed subject matter.

[0045] In some embodiments, the system and method for electro-thermally driven rGOmembrane distillation allow for the determination of the feasibility of stripping ammonia from wastewater with an electro-thermally driven membrane distillation technology using graphene rGO.

[0046] In certain embodiments, rGO can be used as a membrane and as an electrical conductor. Application of voltage can lead to the heating of the rGO layer and evaporation of ammonia through the membrane.

[0047] From this, in certain embodiments, evaporated ammonia will be cooled down and collected. Using the system and method, the process can concentrate ammonia up to 10 wt.% by nitrogen. Such percentile of nitrogen in ammonia and other raw materials may then be used during the manufacture of nitrogen based fertilizers.

[0048] In embodiments, the use of an rGO membrane in the system and method for electro- thermally driven rGO membrane distillation allows for enhanced recycling and enhanced recovery of targeted elements, such as ammonia. Further, in some embodiments, the system allows for localized Joule heating with higher fluxes and lower energy consumption. In some embodiments, the lower energy consumption is approximately 50% of that in common distillation processes.

[0049] Further, the use of an rGo membrane can enable ammonia storage, prevent fouling due to the antimicrobial effect of rGO and the lack of direct contact to the fluid during the process, and allow for the development of smart fabrics produced from agriculture waste (e.g., low grade cotton).

[0050] The electro-thermally driven membrane distillation system can include a membrane distillation module, a voltage application system, and an ammonia collection system. The membrane distillation system can also accommodate the feed solution containing ammonia. By applying a controlled voltage, joule heating can be generated, leading to localized heating of the feed solution. The localized heating, in certain embodiments, causes ammonia to volatilizeand separate from the feed solution. The separated ammonia can then be collected and stored for further processing.

[0051] In certain embodiments, multi-physics software may be used for simulating temperature distribution and heat flux within the membrane distillation module, allowing for optimization of the ammonia volatilization process. The simulation can assist with the determination of the flow rate and required heat flux for achieving optimum ammonia separation efficiency.

[0052] Embodiments of the present disclosure may include variations in rGO reduction levels, support materials, and applied heat levels to achieve the desired ammonia concentration and cost-effectiveness. In certain embodiments, the electro-thermally driven membrane distillation system can be utilized to concentrate ammonia at a cost of less than $500 per ton of nitrogen.

[0053] ELECTRO-THERMAL MEMBRANE DISTILLATION FOR TARGET ELEMENT REMOVAL

[0054] The system and method for electro-thermal membrane distillation is, in some embodiments, aimed at efficiently separating ammonia and other target elements from feed solutions. The method can involve utilizing a membrane distillation module equipped with membranes coated with reduced graphene oxide (rGO). The method can further include controlled application of voltage to the rGO-coated membranes, inducing joule heating that leads to localized heating of the feed solution.

[0055] During the method, the applied controlled voltage can be adjusted to optimize the heating process. This localized joule heating results in the volatilization of ammonia present in the feed solution. Consequently, the volatilized target elements, such as ammonia, are efficiently separated from the feed solution. The method’s responsiveness to the volatizing of ammonia and other target elements ensures timely separation, contributing to the overall effectiveness of the separation process.

[0056] The incorporation of rGO-coated membranes can enhance the efficiency of the electrothermal membrane distillation method. The unique properties of rGO, such as its excellent electrical conductivity and thermal stability, allow for rapid and uniform heating of the feed solution. This, in turn, can enhance the volatilization and separation of ammonia.

[0057] As shown by FIG. 1, the feed used in the system may be rich in nitrogen-based nutrients. The membrane distillation module may include a hydrophobic membrane, which is coated with reduced graphene oxide. In some embodiments, a silver / silver chloride (Ag / AgCl) electrode can be used as the reference electrode in the electrochemical experiments. Moreover, in some embodiments, copper (Cu) foil may be used. In such embodiments, the copper foil may have a thickness of approximately 0.25 mm. As shown in FIG. 1, after the absorption of water and adsorption of solids, such as metal chlorides, the remaining stream after passing through the membrane distillation module may be concentrated ammonia.

[0058] Consistent with the above disclosure, the examples of systems and methods enumerated in the following clauses are specifically contemplated and are intended as a non-limiting set of examples.

[0059] Clause 1. A method for electro-thermally driven membrane distillation of targeted elements including introducing a feed solution containing nitrogen-based nutrients to a membrane distillation module, where the feed solution includes one or more targeted elements, and the membrane distillation module includes reduced graphene oxide (rGO)-coated membranes; applying a controlled voltage to the rGO-coated membranes; generating joule heating within the feed solution by said controlled voltage, resulting in localized heating of the feed solution; adjusting said controlled voltage to optimize the joule heating process; volatilizing the one or more targeted elements from the feed solution due to the localized heating to create one or more volatized targeted elements; and in response to the volatizing of the one or more targeted elements, separating the more volatized targeted elements from thefeed.

[0060] Clause l.a. The method of any foregoing clause, where the one or more targeted elements include ammonia.

[0061] Clause l.b. The method of any foregoing clause, where the one or more targeted elements include alcohols.

[0062] Clause l.c. The method of any foregoing clause, where the one or more targeted elements include volatile fatty acids.

[0063] Clause 2. The method of any foregoing clause, where the nitrogen-based nutrients in the feed solution are present at concentrations of at least 10% weight in nitrogen.

[0064] Clause 3. The method of any foregoing clause, where the rGO-coated membranes include a layer of reduced graphene oxide applied on a porous substrate.

[0065] Clause 4. The method of any foregoing clause, where the controlled voltage applied to the rGO-coated membranes is modulated based on real-time feedback from a temperature sensor.

[0066] Clause 5. The method of any foregoing clause, where the generated joule heating is locally concentrated within the vicinity of the rGO-coated membranes.

[0067] Clause 6. The method of any foregoing clause further including maintaining a temperature gradient across the rGO-coated membranes to facilitate enhanced volatilization of targeted elements, including ammonia.

[0068] Clause 7. The method of any foregoing clause, where adjusting the controlled voltage includes dynamically adapting the voltage based on changes in feed solution composition and operational conditions.

[0069] Clause 8. The method of any foregoing clause, where volatilizing the targeted element results in the formation of targeted vapor.

[0070] Clause 9. The method of any foregoing clause, where separating the volatilized targetedelement includes condensing the targeted element vapor into a separate targeted element-rich phase.

[0071] Clause 10. The method of any foregoing clause further including recycling the condensed targeted element-rich phase back to the feed solution.

[0072] Clause 11. The method of any foregoing clause, where the membrane distillation module is configured in a cross-flow configuration.

[0073] Clause 12. The method of any foregoing clause, where the membrane distillation module is configured in a counter-current configuration.

[0074] Clause 13. The method of any foregoing clause, where the membrane distillation module is part of a continuous-flow system for separation of targeted elements.

[0075] Clause 14. The method of any foregoing clause further including utilizing waste heat from an industrial process to augment the joule heating of the feed solution.

[0076] Clause 15. The method of any foregoing clause, where the separation process is conducted in a closed-loop system.

[0077] PREPARING REDUCED GRAPHENE OXIDE-COATED FABRICS

[0078] Materials and Equipment

[0079] In some embodiments, the system may include fabrics including but not limited to nonwoven fabrics, consisting of 50% Rayon and 50% Polyester, which may be utilized as the substrate for the preparation of the modified fabrics. In some embodiments, the system may include powder and sodium chloride (NaCl, Assay 99.0 %). In certain embodiments, water may be employed during the process performed by the system.

[0080] In some embodiments, Titanium (Ti) wire of 1mm diameter (99.99%- metals basis) and Ti foil, 0.5mm thickness (99.99%- metals basis) can be used as the current collectors and electrodes.

[0081] Monolayer Graphene Oxide Water Dispersion 4 mg / ml can be used for the preparationof graphene-coated fabrics. Moreover, for the preparation of rGO-coated fabrics may include Luria Bertani Broth (Lennox) polytetrafluoroethylene (PTFE) film tape with silicone adhesive side.

[0082] In some embodiments, a silver / silver chloride (Ag / AgCl) electrode can be used as the reference electrode in the electrochemical experiments. Moreover, in some embodiments, copper (Cu) foil may be used. In such embodiments, the copper foil may have a thickness of approximately 0.25 mm.

[0083] A welding machine can be used to spot-weld the Ti wires to Ti foils. In certain embodiments, a Potentiostat can be utilized to conduct the electrochemical steps in the procedure. The samples, when necessary, can be dried using a lab oven or another heating source.

[0084] Preparation Procedure

[0085] The preparation procedure of rGO-coated fabrics may include spray-coating graphene oxide dispersion on one side of a fabric. As used in working experiments, the fabric may be a rayon / polyester blend.

[0086] Following, the graphene oxide-coated fabric may be placed in a container, such as but not limited to a glass petri dish, and transferred to a heating source, such as a lab oven. In some embodiments, the heating source may have a temperature at approximately 75°C.

[0087] The preparation procedure may also include allowing the fabric to dry for a duration of 10 minutes under the heating conditions. After the drying of the first side of the fabric, the second side of the fabric may be spray coated and dried using a similar procedure. In some embodiments, coating and drying each side separately can be employed to minimize the loss of graphene oxide.

[0088] In some embodiments, the graphene oxide-coated fabric can be placed between two Ti foils. The two Ti foils, in certain embodiments, may be held together using PTFE tape andconnected to a Potentiostat as the working electrode.

[0089] The counter electrode in some embodiments may be made of a Ti foil and, the the same or in other emboidments, the reference electrode may be made of Ag / AgCl. The electrodes may be placed in a 250 ml beaker. The distance between the working electrode and the counter electrode, in certain embodiments, is kept at 1 cm.

[0090] The procedure may also include adding NaCl to the beaker as the electrolyte for the electrochemical reduction of graphene oxide. The concentration of the electrolyte can be increased when there is larger graphene loading and higher electrode surface area. This higher concentration of ions ensures that the electrolyte does not limit the reactions. To electrochemically reduce graphene oxide, a Chronoamperometry step can be performed. For example, the Chronoamperometry step was performed at a potential of -1.4 V vs. Ag / AgCl for a duration of Ih. In such an embodiment, the electrolyte was not stirred and the reduction took place under ambient room conditions.

[0091] In certain embodiments, the fabric may be submerged in deionized water and stirred to eliminate the sodium salt adhering to the fibers. Subsequently, the fabric may be placed in oven to dry. In some embodiments, the fabric may be placed in an oven at 75°C for 10 min to dry.

[0092] As shown by FIG. 2, which is a schematic view of the preparation procedure of the rGO-coated fabrics, the process can involve spray coating graphene oxide onto the substrate and drying it in an oven, the electrochemical reduction of graphene oxide, washing the sample to remove sodium chloride, and drying in an oven. The steps shown in FIG. 2 can represent one complete iteration of the coating process and can be repeated to coat an entire fabric sample.

[0093] To enhance the rGO loading on the fabric, an iteration of the coating can be performed, which includes the steps depicted in FIG. 2.

[0094] To obtain the rGO loading, the fabrics can be weighed before and after the desirednumber of iterations. The equation below can be used to calculate the rGO loading of the fabric: rGO loading= U H (1)

[0095] Where Wi is the initial weight of fabric without any coating and W2 is the weight after completion of the coating process. A represents the surface area of the fabric, which in the working examples measured 3 cm * 3 cm.

[0096] Electro-thermal and Antibacterial Experiments

[0097] FIG. 3 depicts a schematic representation of the fabric’s connection to the power supply and thermometer for investigating its electro-thermal performance. As shown in FIG. 3, system 300 depicts the experimental setup for electrothermal evaluation. In some embodiments, system 300 utilizes copper (Cu) foils 302 and alligator clips 304 to connect the power supply 306 to the rGO-coated fabric 308.

[0098] The power supply 306, in such an embodiment, will supply a current reading for each applied voltage with a resolution of 1 mA. To measure the temperature of the rGO-coated fabric 308, the thermocouple 310 can be directly attached to the center of the rGO-coated fabric 308 using PTFE tape. The thermocouple 310 can then be connected a laptop 312.

[0099] Antibacterial tests can be conducted using gram-positive bacterium and gram-negative bacterium. To test the antibacterial qualities, a single colony of bacteria may be suspended in a sterile broth in a flask. The flask can then be incubated while shaking for a set number of hours. In certain embodiments, the number of hours was in the range of approximately 18 hours to approximately 24 hours.

[0100] After preparing the bacteria samples, the rGO-coated fabric can then be placed on top of the inoculum to allow for absorption. To apply an electric field, the inoculated rGO-coated fabric can then be connected to a direct current (DC) power supply. In such an embodiment, each sample can then be transferred to a tube containing sterile broth and subjected to vortexing to release the cells into the solution. The solution may then be serially diluted to perform theplate count method, enabling the quantification of viable cells present on each fabric.

[0101] The reduction rate (R%) for the rGO-coated fabrics can be calculated based on the equation below: 100 (2)

[0102] In the equation above, B represents the number of colonies recovered from the control immediately after inoculation, and A corresponds to the number of colonies recovered from the rGO-coated fabric after the application of a specific current and exposure time.

[0103] As shown in FIG. 4, which depicts a table of samples with different rGO loadings and their corresponding resistance and electronic conductivity, the system and process allow for mechanisms that contribute to the bacterial inactivation on the rGO-coated fabric under an electric field.

[0104] FIG. 5 schematically illustrates the potential effect of increasing the rGO loading on the formation of a more continuous graphene network with increased number of connection points between graphene nanosheets. In certain embodiments, and in working examples, the structural transformation results in improved electron mobility and higher conductivity due to a more favorable pathway for electron flow. Accordingly, in certain embodiments, the repeating coating process on the fabric enables an increase in rGO loading, leading to a more continuous graphene network.

[0105] The Raman spectra of the rGO-coated fabrics with different loading levels are presented in FIG. 6. As shown by FIG. 6, the results of the working examples depict the presence of two prominent peaks in each sample's Raman spectrum. The D band, located at approximately 1340 cm’1, corresponds to structural defects while the G band observed around 1580 cm’1, is related to the C=C stretching vibration of sp2-bonded carbon atoms. Accordingly, as shown in FIG. 6, the distinct peaks in the Raman spectra of the working example confirm the presence of graphene nanosheets on the fabrics.

[0106] Furthermore, as shown in FIG. 6, the intensity of D (ID) is slightly greater than the intensity of G (IG) for all samples which can be attributed to the removal of the oxygen functional groups during the reduction process.

[0107] FIGS. 7A-7O depict the surface morphology of the samples with different rGO loadings, in accordance with certain embodiments of the present disclosure. As shown in FIGS. 7A-7O, an increase in rGO loading on the fabric promotes interconnections between graphene nanosheets by effectively covering a larger surface area of the fabric.

[0108] FIGS. 7A, 7D, 7G, 7J, and 7M are scanning electron microscope images (SEMs) captured at low magnification. These images depicted in FIGS. 7A, 7D, 7G, 7J, and 7M show, as in certain embodiments of the working example, that as the loading of rGO increased, a larger portion of the fabric's surface was coated with rGO nanosheets. Consequently, in certain embodiments of the working example, this phenomenon resulted in the creation of an improved pathway for electrons within the fabric, facilitating enhanced electron transport.

[0109] FIGS. 7C, 7F, 71, 7L, and 70 show that, at higher magnification, the SEM images indicate the presence of wrinkles caused by rGO nanosheets in except for the control sample pictured in FIG. 7C.

[0110] In the working example, TGA was conducted to examine the impact of rGO content on the thermal resistance of the fabric. FIG. 8 depicts the TGA results of the control and samples, in accordance with certain embodiments of the present disclosure, presenting the residual weight percentage as a function of temperature. As shown in FIG. 8, the samples demonstrated an initial minor weight loss primarily attributed to the vaporization of moisture. In addition, as shown in FIG. 8, all the samples exhibited two dramatic weight losses that could be due to the presence of two polymers, namely rayon and polyester.[OHl] FIG. 9 depicts the characteristics of the thermal decompositions observed in the samples of the working example. In some embodiments, as shown in FIG. 9, the incorporation of rGOinto the fabric can lead to a shift in the decomposition temperatures to higher values and a delay in the degradation. As shown in FIG. 9, the magnitude of this shift can increase with higher rGO loading indicating a direct correlation between the rGO loading and the extent to which the decomposition temperatures are elevated. An increase in rGO content can be associated with a higher weight residue suggesting that rGO contributes to the formation of a greater amount of solid residue during the decomposition process. Accordingly, the working example observations show that the presence of rGO contributes to improved resistance against thermal degradation.

[0112] Electrothermal Performance of Working Examples

[0113] In the working example, the voltage-current (V-I) behavior of samples with varying rGO loads was investigated. Further, in the working example, different DC voltages were applied to each fabric using the power supply, and the resulting currents were recorded. FIG. 10 presents the V-I curves for each sample of varying rGO loading under different DC voltages, in accordance with certain embodiments of the present disclosure. As shown by FIG. 10, in some embodiments, increasing rGO load on the samples improves the electrical performance of the fabric.

[0114] In the working examples, the Joule-heating performance of the fabrics was investigated by measuring their surface temperature under different applied voltages. FIGS. 11 A-l ID depict the temperature profile vs. time under different applied voltages for the samples, in accordance with certain embodiments of the present disclosure. As shown in FIGS. 11 A-l ID, the results show the Joule-heating performance of the fabrics. In the working examples, for each sample, three different voltages were applied for a duration of 300 seconds, indicated by the “On” state on the graphs depicted in FIGS. 11 A-l ID, and then the voltage was turned off, indicated by the “Off’ state on the graphs depicted in FIGS. 11 A-l ID. In the working example, and as shown in FIGS. 11 A-l ID, the temperature during each step was continuously monitored andrecorded.

[0115] As shown in FIGS. 11A-11D, there is an initial rapid temperature rise followed by a slower rate of increase until a stable temperature is reached. Further, in some embodiments, as shown in FIGS. 11 A-l ID, the heating rate during the first step and the maximum temperature achieved in the second step are crucial factors when considering the performance of Joule heaters. In some embodiments, the heating rate can reflect the speed at which the temperature of the system increases, and maximum temperature indicates a balance between the input power supplied to the system and the amount of heat lost from it. As shown in FIGS. 11 A-l ID, the initial 20-second period can exhibit a high heating rate for all samples. Furthermore, as shown in FIGS. 11 A-l ID, the heating rate during this stage can increase with higher rGO content of the fabric.

[0116] The working examples show in certain embodiments the continuous and uniform coating of rGO on the fabric can lead to good electron mobility and efficient heat transfer and distribution. Further, the working examples show that the complete reduction of graphene oxide nanoflakes in certain embodiments can result in higher conductivity and enhanced Joule heating capabilities.

[0117] FIG. 12 depicts the repeatability of the Joule-heating effect in the rGO-coated fabric under 9V. As shown by FIG. 12, the working example results confirm the consistency and reliability of the fabric's Joule-heating performance over multiple repetitive cycles.

[0118] Antibacterial Performance of Working Examples

[0119] In a working example utilizing four iterations of rGO coating on fabric, the fabrics were prepared to conduct antibacterial tests under an electric field.

[0120] In the working example for antibacterial performance, 9V resulting in a current density of 88.9 mA / cmi was applied to the rGO-coated fabrics for various exposure times (30 s, 90 s, 180 s, and 300 s). Following the application of voltage to the fabrics, in such an embodiment,the plate count method was employed to determine the number of viable cells present on each fabric.

[0121] FIG. 13 depicts the distribution of B. subtilis colonies on agar plates over time. The photographs visually demonstrate the effects of different application times on the distribution of B. subtilis colonies. As shown by FIG. 13, the number of viable colonies decreases with increasing application time of the voltage.

[0122] FIG. 14 depicts the temperature profile of the fabric surface for 300 seconds application of 9 V of the antibacterial test, accompanied by the corresponding reduction rates calculated at each exposure time. After 30 s of application of the current, the fabric temperature reached approximately 58 °C, leading to a significant reduction of around 98% in bacteria. In some embodiments and as shown in the working example, as the exposure time increased, higher temperatures were attained, and the bacteria were subjected to electricity for a longer duration, leading to higher reduction rates. As shown in FIG. 14, at 300 seconds of exposure, a reduction rate of over 99.99% was achieved for B. subtilis bacteria on the fabric, accompanied by a generated temperature of over 116°C. Accordingly, the working example indicates that in certain embodiments the thermal pathway can play a dominant role in the inactivation of the bacteria.

[0123] FIGS. 15A-5E depict agar plates demonstrating the number of recovered colonies after each test of the working example, with FIG. 15A showing a control plate, FIG. 15B showing rGO-coated fabric no voltage, FIG. 15C showing rGO-coated fabric 1.9 V, FIG. 15D showing rGO-coated fabric 3.7 V, and FIG. 15E showing rGO-coated fabric 6.3 V. As shown in FIGS. 15A-15E, lower voltages resulting in lower current densities correspond to lower rates of bacterial removal.

[0124] FIG. 16 depicts the temperature profiles of different voltages applied to the fabric. As shown in FIG. 16, the temperature did not rise significantly under 1.9 V and 3.7 V. FIG. 16further illustrates the temperature variations at different current densities during the antibacterial test of the working example.

[0125] FIGS. 17A-17C depict SEM images of B. subtilis cells on a control group of pristine fabric without current. FIGS. 17D-17F depict SEM images of B. subtilis cells on the rGO- coated fabric subjected to a voltage of 9V for 300 seconds, in accordance with certain embodiments of the present disclosure.

[0126] The SEM images of FIGS. 17A-17F demonstrate a noticeable distinction between the bacterial cells on the control sample and those on the rGO-coated fabric. As shown in FIGS. 17A-17C, in the control sample, the bacterial cells exhibit an intact rod-shaped morphology, indicating their preserved viability. Conversely, as shown in FIGS. 17D-17F, the bacterial cells on the rGO-coated fabric show a significant alteration in their original shapes, further confirming the loss of their viability due to the applied electric field in certain embodiments.

[0127] Moreover, FIGS. 17A-17F show that the bacterial cells were aligned on the rGO-coated fabric in response to the electric field. Accordingly, in certain embodiments, the movement and orientation of cells induced by electrical stimuli could be used in various applications, such as for example but not limited to wound healing technologies and cancer therapy.

[0128] The working examples further included testing for repeatability of the rGO-coated fabric for antibacterial applications in certain embodiments. In the working examples, multiple antibacterial tests were conducted on the fabric, involving a range of runs from 1 to 8, under an electric field. In each run, the voltage was adjusted to achieve a current density of 88.9 mA / cmi for a duration of 300 seconds. This specific combination of current density and exposure time was determined based on its ability to yield a reduction rate exceeding 99.99%. The reduction percentage, as well as the power consumed, were measured at each step, and the results are illustrated in FIG. 18. As shown in FIG. 18, the reduction rate of bacteria did not decrease after 8 runs, indicating that in certain embodiments the antibacterial efficacy of therGO-coated fabric remains consistent and stable over multiple cycles of use.

[0129] Antibacterial Mechanisms Shown by Working Examples

[0130] In accordance with certain embodiments of the present disclosure, the working examples show that a mechanism contributing to bacterial inactivation on the rGO-coated fabric under an electric field, in some embodiments, is the physical contact and chemical interaction with rGO nanosheets on the fabric’s surface, which can lead to cell disruption. The sharp edges and wrinkles of the rGO nanosheets can physically disrupt the bacterial cell membranes, compromising their integrity. Moreover, rGO nanosheets have the potential to induce oxidative stress through the generation of reactive oxygen species, resulting in bacterial DNA damage and inhibition of bacterial growth.

[0131] In accordance with certain embodiments of the present disclosure, the working examples show that a mechanism contributing to bacterial inactivation on the rGO-coated fabric under an electric field, in some embodiments, is the joule heat generated by the applied electric current, which can cause membrane damage, protein denaturation, and enzyme inactivation within the bacterial cells. Therefore, the increase in temperature resulting from Joule heating can lead to structural changes and functional impairment of cellular components.

[0132] In accordance with certain embodiments of the present disclosure, the working examples show that a mechanism contributing to bacterial inactivation on the rGO-coated fabric under an electric field, in some embodiments, is the electrical effects, which can directly impact the bacterial cells through electroporation and direct electron transfer. These mechanisms result in destruction of the cell membrane, protein denaturation, and oxidation of enzymes. Considering this, the electric field can induce disruptive forces on the cell membranes, rendering them permeable and susceptible to damage compromising the bacterial cell’s viability.

[0133] These three pathways, namely physical contact and chemical interaction with rGO,Joule heating, and electrical effects, collectively contribute to the inactivation of bacteria on the rGO-coated fabric.

[0134] As is shown in the working examples, no colonies of bacteria were recovered after the application of electricity to the rGO-coated fabric. Therefore, the electro-thermal treatment is effective for both gram-positive and gram-negative bacteria.

[0135] Consistent with the above disclosure, the examples of systems and methods enumerated in the following clauses are specifically contemplated and are intended as a nonlimiting set of examples.

[0136] Clause 16. A method for preparing graphene oxide-coated fabrics for electrochemical reduction including spray-coating a graphene oxide dispersion onto a fabric, where, resultant to spray-coating the fabric, the fabric has a coating of graphene oxide on a surface of the fabric and the fabric is a graphene oxide-coated fabric; transferring the graphene oxide-coated fabric to a container; subjecting the container, containing the graphene oxide-coated fabric, to a heating source; allowing the graphene oxide-coated fabric to dry under the heating conditions; and electrochemically reducing the graphene oxide, where the coating of the graphene oxide on the surface of the fabric becomes reduced graphene oxide (rGO) and the fabric is a rGO- coated fabric.

[0137] Clause 17. The method of any foregoing clause further including submerging the rGO- coated fabric in a solvent and stirring to remove one or more adhered substances from the rGO- coated fabric.

[0138] Clause 18. The method of any foregoing clause further including drying the rGO-coated fabric.

[0139] Clause 19. The method of any foregoing clause further including, prior to electrochemically reducing the graphene oxide, securing the graphene oxide-coated fabric between two foils.

[0140] Clause 20. The method of any foregoing clause, where the foils are made of titanium, aluminum, or copper, and where the tape is made of polytetrafluoroethylene (PTFE) or a polymer-based material.

[0141] Clause 21. The method of any foregoing clause, where at least one of the two foils acts as a counter electrode.

[0142] Clause 22. The method of any foregoing clause, where the two foils are held together using tape and connected to a working electrode.

[0143] Clause 23. The method of any foregoing clause, where at least one of the two foils acts as a counter electrode, and further including placing the working electrode and the counter electrode in a container with a distance between the counter electrode and the working electrode maintained.

[0144] Clause 24. The method of any foregoing clause further including adding an electrolyte to the container for electrochemical reduction of graphene oxide.

[0145] Clause 25. The method of any foregoing clause, where the electrolyte concentration is adjusted based on factors including the graphene loading and electrode surface area.

[0146] Clause 26. The method of any foregoing clause, where the graphene oxide dispersion is prepared using a solvent-based method.

[0147] Clause 27. The method of any foregoing clause, where the heating source is an oven, a hot plate, or a heat gun.

[0148] Clause 28. The method of any foregoing clause, where the drying of the graphene oxidecoated fabric is carried out in an environment with controlled humidity.

[0149] Clause 29. The method of any foregoing clause, where the electrochemical reduction is conducted under a controlled atmosphere, such as inert gas or vacuum.

[0150] Clause 30. The method of any foregoing clause, where the solvent used for submerging the rGO-coated fabric is deionized water.

[0151] Clause 31. The method of any foregoing clause, where the drying of the rGO-coated fabric is carried out using natural evaporation or under controlled temperature conditions.

[0152] Clause 32. A method of using rGO-coated fabric in healthcare applications, including providing a fabric coated with graphene oxide, where the fabric coated with graphene oxide is prepared through a process including: (i) spray-coating a graphene oxide dispersion onto a fabric, (ii) subjecting the graphene oxide-coated fabric to a heating source, (iii) allowing the graphene oxide-coated fabric to dry, and (iv) electrochemically reducing the graphene oxide, where the graphene oxide on the fabric becomes reduced graphene oxide (rGO) and the fabric is a rGO-coated fabric; applying the rGO-coated fabric to a wound site, where the applying the rGO-coated fabric facilitates antimicrobial activity at the wound site; and resultant from the antimicrobial activity at the wound site, promoting wound healing.

Claims

WHAT IS CLAIMED IS:

1. A method for electro-thermally driven membrane distillation of targeted elements comprising:(a) introducing a feed solution containing nitrogen-based nutrients to a membrane distillation module, wherein(i) the feed solution comprises one or more targeted elements, and(ii) the membrane distillation module comprises reduced graphene oxide (rGO)-coated membranes;(b) applying a controlled voltage to the rGO-coated membranes;(c) generating joule heating within the feed solution by said controlled voltage, resulting in localized heating of the feed solution;(d) adjusting said controlled voltage to optimize the joule heating process;(e) volatilizing the one or more targeted elements from the feed solution due to the localized heating to create one or more volatized targeted elements; and(f) in response to the volatizing of the one or more targeted elements, separating the one or more volatized targeted elements from the feed.

2. The method of claim 1, wherein the one or more targeted elements comprise ammonia.

3. The method of claim 1, wherein the one or more targeted elements comprise alcohols.

4. The method of claim 1, wherein the one or more targeted elements comprise volatile fatty acids.

5. The method of claim 1, wherein the nitrogen -based nutrients in the feed solution are present at concentrations of at least 10% weight in nitrogen.

6. The method of claim 1, wherein the rGO-coated membranes comprise a layer of reduced graphene oxide applied on a porous substrate.

7. The method of claim 1, wherein the controlled voltage applied to the rGO-coated membranes is modulated based on real-time feedback from a temperature sensor.

8. The method of claim 1, wherein the generated joule heating is locally concentrated within the vicinity of the rGO-coated membranes.

9. The method of claim 1, further comprising maintaining a temperature gradient across the rGO-coated membranes to facilitate enhanced volatilization of ammonia.

10. The method of claim 1, wherein adjusting the controlled voltage includes dynamically adapting the voltage based on changes in feed solution composition and operational conditions.

11. The method of claim 2, wherein volatilizing the ammonia results in the formation of ammonia vapor.

12. The method of claim 11, wherein separating the one or more volatized elements includes condensing the ammonia vapor into a separate ammonia-rich phase.

13. The method of claim 12, further comprising recycling the condensed ammonia-richphase back to the feed solution.

14. The method of claim 1, wherein the membrane distillation module is configured in a cross-flow configuration.

15. The method of claim 1, wherein the membrane distillation module is configured in a counter-current configuration.

16. The method of claim 1, wherein the membrane distillation module is part of a continuous-flow system for separation of targeted elements.

17. The method of claim 1, further comprising utilizing waste heat from an industrial process to augment the joule heating of the feed solution.

18. The method of claim 1, wherein the separation process is conducted in a closed-loop system.

19. A method for preparing graphene oxide-coated fabrics for electrochemical reduction comprising:(a) spray-coating a graphene oxide dispersion onto a fabric, wherein, resultant to spray-coating the fabric, the fabric has a coating of graphene oxide on a surface of the fabric and the fabric is a graphene oxide-coated fabric;(b) transferring the graphene oxide-coated fabric to a container;(c) subjecting the container, containing the graphene oxide-coated fabric, to a heating source;(d) allowing the graphene oxide-coated fabric to dry under the heating conditions; and(e) electrochemically reducing the graphene oxide, wherein the coating of the graphene oxide on the surface of the fabric becomes reduced graphene oxide (rGO) and the fabric is a rGO-coated fabric.

20. The method of claim 19 further comprising submerging the rGO-coated fabric in a solvent and stirring to remove one or more adhered substances from the rGO-coated fabric.

21. The method of claim 19 further comprising drying the rGO-coated fabric.

22. The method of claim 19 further comprising, prior to electrochemically reducing the graphene oxide, securing the graphene oxide-coated fabric between two foils.

23. The method of claim 22, wherein the two foils are made of titanium, aluminum, or copper, and wherein the tape is made of polytetrafluoroethylene (PTFE) or a polymer-based material.

24. The method of claim 22, wherein at least one of the two foils acts as a counter electrode.

25. The method of claim 22, wherein the two foils are held together using tape and connected to a working electrode.

26. The method of claim 25, wherein at least one of the two foils acts as a counter electrode, and further comprising placing the working electrode and the counter electrode in a containerwith a distance between the counter electrode and the working electrode maintained.

27. The method of claim 26, further comprising adding an electrolyte to the container for electrochemical reduction of graphene oxide.

28. The method of claim 27, wherein the electrolyte concentration is adjusted based on factors including the graphene loading and electrode surface area.

29. The method of claim 19, wherein the graphene oxide dispersion is prepared using a solvent-based method.

30. The method of claim 19, wherein the heating source is an oven, a hot plate, or a heat gun.

31. The method of claim 19, wherein the drying of the graphene oxide-coated fabric is carried out in an environment with controlled humidity.

32. The method of claim 19, wherein the electrochemical reduction is conducted under a controlled atmosphere, such as inert gas or vacuum.

33. The method of claim 19, wherein the solvent used for submerging the rGO-coated fabric is deionized water.

34. The method of claim 19, wherein the drying of the rGO-coated fabric is carried out using natural evaporation or under controlled temperature conditions.

5. A method of using rGO-coated fabric in healthcare applications, comprising:(a) providing a fabric coated with graphene oxide, wherein the fabric coated with graphene oxide is prepared through a process comprising:(i) spray-coating a graphene oxide dispersion onto a fabric,(ii) subjecting the graphene oxide-coated fabric to a heating source,(iii) allowing the graphene oxide-coated fabric to dry, and(iv) electrochemically reducing the graphene oxide, wherein the graphene oxide on the fabric becomes reduced graphene oxide (rGO) and the fabric is a rGO-coated fabric;(b) applying the rGO-coated fabric to a wound site, wherein the applying the rGO- coated fabric facilitates antimicrobial activity at the wound site; and(c) resultant from the antimicrobial activity at the wound site, promoting wound healing.

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