Patent Application
20250018368
The present description is from the field of preparing macromolecular substances to produce articles or porous materials.
The scarcity of fresh water suitable for consumption has been intensifying in different regions of the planet as a result of irregular disposal of sewage and pollution due to spills/leaks of organic and inorganic chemicals (heavy metals, dyes, etc), whether as a result of accidents, natural disasters or bad labor/industrial practices. Such contamination also occurs in maritime waters and estuaries, harming fishing, leisure and other activities linked to the seas and coasts. In general, the vast majority of contaminants are always harmful to all living beings that make up a given ecosystem, whether human or not.
The growing concern about environmental problems related to the contamination of river waters with pollutants (heavy metals, dyes, pesticides, detergents, etc) has demanded attention from both the industry and society as a whole. This occurs because although heavy metals are natural components found in the Earth's crust, some of them (Cu, Hg, Cd, Pb, etc) can be toxic, even in low concentrations. Furthermore, some of them can be bioaccumulative for the human body, representing a threat to human health (causing diseases such as cancer), and to other living beings, in which quantities of these metals are discarded excessively and irresponsibly.
It is worth noting that many environments contaminated by pollutants are complex mixtures, which contain various metals and dyes, such as waste from the textile industry discarded in effluents. This complexity makes the treatment of these contaminated media a greater challenge to be overcome.
Among the various strategies that can be applied in order to reduce the amount of these pollutants, absorbent and/or adsorbent materials show promise, due to their easy applicability and high specific surface area, making them efficient in water remediation, even in low quantities. However, most commercial absorbents and/or adsorbents are non-biodegradable or minimally biodegradable. Therefore, the search for biodegradable materials obtained from renewable sources has attracted attention.
In this scenario, biomass has emerged as a source of obtaining biodegradable and renewable polymers, applicable in the development of new absorbent/adsorbent materials. Among these materials, nanocellulose stands out, due to its abundance and excellent reinforcing properties, in addition to being a renewable and biodegradable material. Additionally, nanocellulose can be isolated from sugarcane bagasse, which is one of the main by-products of the ethanol production process and consists mainly of cellulose.
Cellulose (C6H10O5) n is the most abundant natural polymer in nature, renewable and biodegradable, formed from glucose with β(1,4) linkages between D-glucose units. The polymer chains interact via intra- and intermolecular interactions, forming hydrogen bonds through the hydroxyl groups present in the monomeric units.
Nanometer-scale structures extracted from cellulose arouse considerable interest due to their intrinsic properties (different morphological structures, hydrophilicity, possibility of functionalization and abundance), and this allows applications in different segments. Nanocellulose extracted from plant biomass can be classified into two different denominations, according to its structure and extraction route: crystalline nanocellulose (CNC), which is the crystalline region of the polymer, composed of shorter and more rigid chains; and nanofibrillated cellulose (CNF), which consists of the crystalline and amorphous region of the polymer with longer chains. Furthermore, these nanostructures can be used in their original form as polymer matrix in composites, since they have low density, high rigidity, surface modification capacity, and high aspect ratio.
The process of obtaining nanocellulose requires defibrillation of the cellulose, a method called “top-down”, in which the biomass bulk made up of fibers and microfibers are comminuted into fibrils with nanometric dimensions. This process can be carried out via chemical and/or mechanical methods, thus altering its final properties.
The most common chemical process for obtaining nanocellulose is acid hydrolysis, assisted with strong acids (sulfuric or hydrochloric). In this process, hydrolysis occurs in the amorphous regions of cellulose fibers, isolating cellulose nanocrystals (CNC). Mechanical processes require equipment that applies high shear energy to the cellulose suspension, such as ball mills, ultrasound and high-pressure microfluidizers. Such processes result in nanofibrillated cellulose (CNF) with average diameters depending on the number of cycles and the amount of applied energy.
Due to the abundant amount of hydroxyl groups on the surfaces of the cellulose chains that make up these nanostructures, it is possible to combine chemical cellulose functionalization processes, such as acetylation and graphitization or even TEMPO oxidation (N-oxyl-2,2,6,6-tetramethylpiperidine), which together with mechanical processes, favor fibrillation and obtaining functionalized CNF with uniform morphology and average diameter, and that when applied in the production of porous materials, this CNF can produce structures with high porosity, more homogeneous pore sizes and with micro and nanometric dimensions.
CNFs, which are one of the raw materials of this invention, show promise in the production of porous materials (aerogels, foams and sponges) due to their characteristics of renewability, biodegradability and support in three-dimensional porous structures with high specific surface area.
Known applications include acoustic and thermal insulation, membranes for water decontamination, biological growth scaffolds for bone regeneration or tissue printing, and electronic devices for energy generation and storage.
The viability of foams based on nanocellulose is also due, among other factors, to the simplicity of their method of obtaining, which includes mixing the components added to the nanocellulose suspension, subsequent freezing and sublimation (removal) of water through the freeze-drying process.
For effective adsorption of the pollutants, the porous material must remain structurally resilient for a considerable period of time in order to achieve maximum adsorption. However, due to its inherent hydrophilicity, resulting from the high availability of solvatable hydroxyl groups in aqueous media, the use of nanocellulose as a filtering foam or pollutant absorber in aqueous media is not viable. In this context, crosslinking agents are added to nanocellulose, interconnecting the nanostructure chains by physical or chemical means, in order to obtain a porous and structurally resilient 3D structure in aqueous media.
Natural rubber latex (NRL) extracted from rubber trees has unique properties, especially when compared to its synthetic analogue, polyisoprene. The distinguished characteristics of NRL come from its natural composition. The amount of polyisoprene in NRL can be estimated at 96% m/m, with 1% m/m protein and 3% m/m phospholipids. These almost 4% of different compounds in NRL give it unique properties, stabilizing the polyisoprene particles, surrounding this hydrophobic core with a protein-phospholipid layer that gives it a negative charge, this being the property responsible for the colloidal stability necessary for its effective homogeneous dispersion in polymeric matrices, such as nanofibrillated cellulose matrix.
In view of the above, there is a demand for the development of new structurally resilient porous materials in aqueous media based on biopolymers with high porosity and specific surface area, whose functionalization with groups that sequester inorganic and organic pollutants, such as heavy metals, dyes and detergents allows its application in the remediation of aquatic environments.
Patent document US20190309144 describes an airgel or foam comprising CNF. Its production process is also described, which uses at least one organic solvent, as well as one or more degreasing agents. crosslinking. Such components are not environmentally friendly, which is a disadvantage of the technique described in this document.
Patent document EP3335695 discloses a hydrogel-like foam comprising TEMPO-oxidized CNF, trehalose and polyethylene glycol. This document also describes the production process of this foam, wherein one of the steps involves the freeze-drying process. The described formulation is not suitable for producing foams (which have a solid content below 10% by mass, preferably below 8% by mass), due to the increase in viscosity in the presence of trehalose and polyethylene glycol.
Patent document SE539714C2 describes a foam comprising fibrillated (CNF) or crystalline (CNC) nanocellulose, oxidized by periodate. The process of producing this foam, which involves cross-linking control through highly complex steps of ice growth followed by thawing, is also described. Such a process strongly depends on strict temperature control as a function of freezing time to achieve the described airgel.
Patent document FI127764B presents a method of treating water with CNF oxidized by TEMPO, wherein nanocellulose acts as a filtering agent for heavy metals in a network formed by CNF. Such nanocellulose is not processed to obtain the foam. The use of cellulose in this way brings some disadvantages, such as the difficulty in removing residual nanocellulose after treating the polluted aqueous environment and difficulty in separating nanocellulose and water, making it impossible to reuse the material.
Patent document U.S. Pat. No. 10,350,576 discloses a process for producing an airgel that comprises cellulose nanocrystals or nanofibrillates functionalized with organosilane groups through heating, being applied to the removal of hydrophobic pollutants. A limitation of the described object is evident in its difficulty in removing hydrophilic and amphiphilic pollutants due to the high hydrophobicity of the revealed airgel.
Patent document BR02020022041-1 anticipates a hydrophobic foam comprising natural rubber latex (NRL) and cellulose in fibrillar format, preferably micro and nanofibrillated cellulose. The components stabilize the polyisoprene particles of this latex, surrounding its hydrophobic core with a protein-phospholipid layer that gives it a negative charge, being responsible for the colloidal stability necessary for its effective dispersion in polymeric matrices, such as the nanofibrillated cellulose matrix, eliminating the need for the addition of any stabilizing, dispersing and crosslink for this purpose. A limitation of the aforementioned is the fact that the cellulose described in this document does not undergo refinement by oxidation, having less control over the size of the resulting mixture of microstructures and nanostructures. As a result of the lack of refinement in the control of diameters in cellulose, the resulting foam mostly presents micrometer-sized pores and high hydrophobicity, making it difficult to capture pollutants such as hydrophilic dyes and amphiphilic materials.
It is an objective of the present description to reveal a foam based on materials from a natural and renewable source, with high porosity, low density and high adsorption capacity for inorganic (heavy metals precursors) and organic (dyes and detergents) compounds, which can be applied as an absorbent material in the remediation of river systems or as a protection against their contamination. It is also the objective of the present description to disclose a production process for said foam.
The objects of the present invention are achieved by a foam comprising oxidized nanofibrillated cellulose and natural rubber latex. The objectives of the present invention are also achieved by a foam production process based on oxidized fibrillated cellulose and natural rubber latex, wherein the process comprises:
adding cellulose in micro and nanofibrillar format, previously oxidized and homogenized to a dispersion of natural rubber latex;
The present invention is illustrated in the embodiments represented in figures, as briefly described below.
The present description discloses a foam comprising natural rubber latex (NRL) and cellulose in fibrillar format, specifically oxidized micro and nanofibrillated cellulose. The aforementioned oxidized micro and nanofibrillated cellulose foams are produced using “green” routes (using renewable components and eliminating the use of solvents, that is, using only water as a solvent). This production process involves the incorporation of natural rubber latex (a biopolymer commonly extracted from Hevea brasilienses) as a crosslinking agent for cellulose nanofibrils in aqueous media.
The oxidized micro and nanofibrillated cellulose described herein undergoes refinement by oxidation, having greater control over the size of the resulting microstructures and nanostructures. As a result of greater control over the diameters of cellulose nanofibers, the foams obtained had a low solids content (below 8% by mass, preferably below 2%), high porosity (porosity above 80%, with nanometric-sized pores) and high mechanical-structural stability in aqueous media, compared to prior art foams formed by NRL and non-oxidized fibrillar cellulose, facilitating the capture of pollutants such as hydrophilic dyes and amphiphilic materials.
The presence of the cellulose's negative charge, due to the previous oxidation process, makes it possible to capture pollutants charged with opposite charges, such as cationic dyes and heavy metal ions, expanding the range of applications of these foams.
In one embodiment of the present description, the foams comprise cellulose with oxidized fibrillar morphology with micro and nanometric dimensions.
In one embodiment of the present description, the foams comprise cellulose with oxidized fibrillar morphology containing carboxylic groups.
In one embodiment of the present description, the foams comprise cellulose with oxidized fibrillar morphology from at least one natural source selected from the group comprising eucalyptus, sugar cane bagasse and mixtures thereof.
In one embodiment of the present description, the foams comprise a concentration of natural rubber latex in dry mass between 5 and 50%.
In one embodiment of the present description, the foams comprise natural rubber latex with a pH between 7 and 9.
In one embodiment of the present description, the foams comprise natural rubber latex from Hevea brasilienses.
In one embodiment of the present description, the foam production process comprises:
In one embodiment of the present description, at least one of the mold walls has lower thermal conductivity than the other mold walls.
The various types of foams described here, due to their characteristics and production processes, find a wide range of applications, including: use for adsorption of dyes; use for adsorption of detergents; use for adsorption of inorganic precursor salts of heavy metals, such as Cu, Cd, Pb, Hg and Ag.
In one embodiment of the present description, said foams are used for decontamination and remediation of waters, such as waters disposed in reservoirs or found in the environment.
In one embodiment of the present description, said foams are used for decontamination and remediation of waters, and the media decontaminated/remediated with them do not exhibit ecotoxicity.
In the following paragraphs, non-limiting examples of embodiments of the present invention are presented that have the same inventive concept as the previously described embodiments.
In this example, the detergent retention capacity of the foams of the present invention was evaluated, considering a composition containing natural rubber latex (NRL) and oxidized nanofibrillated cellulose (CNF), whose source was sugar cane bagasse. The foam was produced according to the method described below.
For the composition, it was used an aqueous dispersion of NRL extracted from the species Hevea brasilienses with an ammonia percentage of 0.9% and 62.5% total solids content, and CNF with 2% m/m solids content containing cellulose nanofibrils from sugarcane bagasse.
In this exemplary embodiment, the foams were obtained in a process involving two steps. The first involves the functionalization of CNF from sugarcane bagasse, and the second involves the homogenization of oxidized CNF with NRL in proportions of 80% CNF and 20% latex, all in dry mass.
Oxidized CNF was obtained through the oxidation of bleached pulp mediated by TEMPO (N-oxyl-2,2,6,6-tetramethylpiperidine). Thus, 13 g of bleached pulp were immersed in 1300 ml of distilled water for 24 hours. Then, the system was shaken to homogenize the suspension. A PH meter is coupled to the system and 1.3 g of NaBr and 0.208 g of TEMPO were added. The addition of 40 g of NaClO (12%) was done slowly in order to keep the pH constant and equal to 10. This was done with the addition of a NaOH solution (0.5M). The entire procedure was performed between 100 and 130 min. Once the reaction was complete, HCl was added to neutralize the suspension (pH 7). The oxidized CNF was washed to remove excess reagent.
The mixture of homogenized oxidized CNF (previously sonicated in tip ultrasound with an amplitude of 40% for 5 min under an ice bath) and the dispersion of NRL was made with a final solids content equal to 2% m/m. The mixture was subjected to mechanical stirring for 30 min at a temperature of 27° C. This amount of solids resulted in a suitable viscosity for filling cylindrical polyethylene molds. The molds were filled with the CNF/NRL mixture and placed in a freezer for 24 hours at −10° C. They were subsequently subjected to the freeze-drying process for 48 hours to completely sublimate the ice contained in the samples.
The foams were immersed in 10 mL of yellow commercial detergent (Limpol™ brand, produced by the company Bombril S.A., Brazil) for a detergent retention time of 5 minutes. Measurements were acquired in quintuplicate after 5 minutes in equilibrium with the commercial detergent, as shown in Table 1.
The absorption or retention capacity (Q) was calculated from equation (1):
Wherein Mf e Mo are, respectively, the masses of the foams after absorption and drying. The detergent retention capacity was (39.7±1.4) g/g, when compared to the dry foam mass itself (before detergent retention).
In this example, the same foams as in Example 1 were subjected to consecutive reuse tests. The tests are described below.
Initially, the foams from Example 1 were submerged in water for 20 hours, to clean and remove the retained detergent. After this immersion time, the foams were removed from the water and dried at room temperature for 48 h. Then, each foam was immersed in 10 mL of yellow commercial detergent (Limpol™) for a detergent retention time of 5 minutes. Measurements were acquired in quintuplicate for the foams. The retention capacity (Q) of the detergent by the foams is described in Table 2. The Q value of the Limpol™ detergent was (23.5±4.9) g/g, when compared to the mass of the dry foam itself (before detergent retention). The reuse of foams showed a detergent retention efficiency of 60%.
The CNF80/NRL20 foams from the first reuse cycle were dried and analyzed for their internal porous microstructure by X-ray microtomography, in order to evaluate the possible structural changes caused by the retention/reuse process.
The porous microstructure of the foams was verified by 2D projections, as shown in
After the first reuse test, the same foams were subjected to the second and third reuse test. The test is described as follows: foams were submerged in water for 20 h, to clean and remove retained detergent. After this immersion time, they were removed from the water and dried at room temperature for 2 days. Then, each foam was immersed in 10 mL of yellow commercial detergent (Limpol™) for a detergent retention time of 5 minutes. Measurements were acquired in quintuplicate for the foams. The detergent retention capacity (Q) of the foams was calculated according to Equation 1 and the calculated values are organized in Table 3 and Table 4, referring, respectively, to the second and third reuse test.
The Q value of Limpol™ detergent was (21.1±5.2) g/g for the second test, when compared to the dry foam mass itself (before detergent retention).
In the case of the third test, the Q value was (20±7) g/g. The reuse of the foams showed a detergent retention efficiency of between 86 and 90%, in relation to the reuse cycles (cycles 1, 2, and 3). This demonstrates the effectiveness of use in repeated retention cycles, maintaining its 3D structural architecture, and the eco-sustainable characteristic of this material.
In this example, a detergent retention test was carried out with state-of-the-art foams (according to previous document BR02020022041-1) formed from non-oxidized CNF combined with NRL, for comparison with foams obtained with oxidized CNF, as per the present description.
Non-oxidized CNF foams were obtained in a process that involves the homogenization of non-oxidized CNF with NRL in proportions of 80% CNF and 20% latex, all in dry mass.
The mixture of homogenized non-oxidized CNF (previously sonicated in tip ultrasound with an amplitude of 40% for 5 min under an ice bath) and the dispersion of NRL was made with a final solids content equal to 2% m/m. The mixture was subjected to mechanical stirring for 30 min at a temperature of 27° C. This amount of solids resulted in a suitable viscosity for filling cylindrical polyethylene molds. The molds were filled with the CNF/NRL mixture and placed in a freezer for 24 hours at −10° C. They were subsequently subjected to the freeze-drying process for 48 hours to completely sublimate the ice contained in the samples.
The foams were then immersed in 10 mL of yellow commercial detergent (Limpol™) for a detergent retention time of 5 minutes. Measurements were acquired in quintuplicate after 5 minutes in equilibrium with the commercial detergent, as shown in Table 5.
The detergent retention capacity (Q) for foams with non-oxidized CNF was (26.1±1.2) g/g, below those produced with oxidized CNF (39.7±1.4) g/g. The increase in Q value may be related to the oxidation of CNFs. The existence of these functional groups promotes greater entanglement of nanofibrils, resulting in a hydrated three-dimensional structure, which when subjected to the freezing process and subsequent freeze-drying results in architectures with greater porosity, smaller pores and greater specific surface area. This greater surface area can be closely correlated with the significant increase in the Q value, thus justifying the need for oxidation of CNFs to gain absorption of amphiphilic components.
In parallel with the increase in the Q value, the lack of oxidation of CNF impedes the structural resilience of the foam in a liquid medium.
In this exemplary embodiment, the foams were obtained in a process involving two steps. The first involves the functionalization of CNF from sugarcane bagasse, and the second involves the homogenization of oxidized CNF with NRL in proportions of 80% CNF and 20% latex, all in dry mass.
Oxidized CNF was obtained through the oxidation of bleached pulp mediated by TEMPO (N-oxyl-2,2,6,6-tetramethylpiperidine). Thus, 13 g of bleached pulp were immersed in 1300 ml of distilled water for 24 hours. Then, the system was shaken to homogenize the dispersion. A PH meter is coupled to the system and 1.3 g of NaBr and 0.208 g of TEMPO were added. The addition of 40 g of NaClO (12%) was done slowly in order to keep the pH constant and equal to 10. This was done with the addition of a 0.5 M NaOH solution. The entire procedure was carried out between 100 and 130 min. Once the reaction was complete, HCl was added to neutralize the suspension, resulting in pH 7. The oxidized CNF was washed to remove excess reagent.
The mixture of homogenized oxidized CNF (previously sonicated in tip ultrasound with an amplitude of 40% for 5 min under an ice bath) and the dispersion of NRL was made with a final solids content equal to 2% m/m. The mixture was subjected to mechanical stirring for 30 min at a temperature of 27° C. This amount of solids resulted in a suitable viscosity for filling cylindrical polyethylene molds. The molds were filled with the CNF/NRL mixture and placed in a freezer for 24 hours at −10° C. They were subsequently subjected to the freeze-drying process for 48 hours to completely sublimate the ice contained in the samples.
The foams show good structural resistance when immersed for 24 hours in water, as shown in
The foams demonstrated high MB adsorption, with the QMB value being close to 250 mg/g adsorbed after 24 hours. This can be visually verified by the change in color of the solution and foam (
In this present invention, the foams were obtained in a process involving two steps. The first involves the functionalization of CNF from sugarcane bagasse, and the second involves the homogenization of oxidized CNF with NRL in proportions of 80% CNF and 20% latex, all in dry mass.
Oxidized CNF was obtained through the oxidation of bleached pulp mediated by TEMPO (N-oxyl-2,2,6,6-tetramethylpiperidine). Thus, 13 g of bleached pulp were immersed in 1300 ml of distilled water for 24 hours. Then, the system was shaken to homogenize the suspension. A PH meter is coupled to the system and 1.3 g of NaBr and 0.208 g of TEMPO were added. The addition of 40 g of NaClO (12%) was done slowly in order to keep the pH constant and equal to 10. This was done with the addition of a NaOH solution (0.5M). The entire procedure was performed between 100 and 130 min. Once the reaction was complete, HCl was added to neutralize the suspension, resulting in pH 7. The oxidized CNF was washed to remove excess reagent.
The mixture of homogenized oxidized CNF (previously sonicated in tip ultrasound with an amplitude of 40% for 5 min under an ice bath) and the dispersion of NRL was made with a final solids content equal to 2% m/m. The mixture was subjected to mechanical stirring for 30 min at a temperature of 27° C. This amount of solids resulted in a suitable viscosity for filling cylindrical polyethylene molds. The molds were filled with the CNF/NRL mixture and placed in a freezer for 24 hours at −10° C. They were subsequently subjected to the freeze-drying process (10 mBar) for 48 hours to completely sublimate the ice contained in the samples.
The adsorption capacity of Copper II ions was evaluated based on the isothermal adsorption test of known masses of foams inserted in copper chloride solutions. For this, different copper chloride solutions ranging between 15 and 700 mg/L were prepared and equilibrated at 27° C. Such concentrations were called “Cinitial”. The mass of the CNF/NRL foams was cataloged and identified as “minitial”. The minitial values and Cinitial obtained from this example are quantified in Table 7.
The previously weighed foams were immersed in 25 mL of each concentration, as illustrated in
From the data presented in Table 7, it appears that oxidized CNF and NRL foams are effective in sequestering copper ions. The amount adsorbed here reached values of around 350 mg of Cu II adsorbed per gram of foam. The adsorption capacity for different concentrations was verified. Even at very low values (˜25 ppm) the foams were effective in sequestering more than 40% of the ions available in solution. In short, for all of these, the sequestration was effective and with values above those reported in the literature (between 20 and 100 mg/g).
Additionally, the adsorption of Cu II ions on the foam was analyzed by X-ray microtomography, in order to identify possible morphological changes, as well as differences in X-ray attenuation, after the adsorption of copper ions. This test was carried out with the samples after immersion in a CuCl2 solution and subsequently dried for 2 days (
The foams were obtained in a process that involves two steps. The first involves the functionalization of CNF from sugarcane bagasse, and the second involves the homogenization of oxidized CNF with NRL in proportions of 80% CNF and 20% latex, all in dry mass.
Oxidized CNF was obtained through the oxidation of bleached pulp mediated by TEMPO (N-oxyl-2,2,6,6-tetramethylpiperidine). Thus, 13 g of bleached pulp were immersed in 1300 ml of distilled water for 24 hours. Then, the system was shaken to homogenize the suspension. A PH meter is coupled to the system and 1.3 g of NaBr and 0.208 g of TEMPO were added. The addition of 40 g of NaClO (12%) was done slowly in order to keep the pH constant and equal to 10. This was done with the addition of a NaOH solution (0.5M). The entire procedure was performed between 100 and 130 min. Once the reaction was complete, HCl was added to neutralize the suspension, resulting in a neutral pH (˜7). The oxidized CNF was washed with distilled water to remove excess reagent.
The mixture of homogenized oxidized CNF (previously sonicated in tip ultrasound with an amplitude of 40% for 5 min under an ice bath) and the dispersion of NRL was made with a final solids content equal to 2% m/m. The mixture was subjected to mechanical stirring for 30 min at a temperature of 27° C. This amount of solids resulted in a suitable viscosity for filling cylindrical polyethylene molds. The molds were filled with the CNF/NRL mixture and placed in a freezer for 24 hours at −10° C. They were subsequently subjected to the freeze-drying process (10 mBar) for 48 hours to completely sublimate the ice contained in the samples.
The proposed ecotoxicity test consisted of evaluating the ecotoxicity of the material and the exposure of a bioindicator to systems contaminated with Cu (II) that were previously remediated by these foams based on CNF and NRL. The bioindicator model used was from Daphia similis, in which the acute toxicity results (median mortality concentration—LC50—with 95% confidence interval (CI), estimated by the PriProbit software) were used as a response variable. Furthermore, in order to simulate an experiment closer to the real scenario, the presence of organic compounds, such as humic acid (HA-found in aquatic environments in concentrations between 1-20 mg L−1) were incorporated in this assay, as they may interfere with the capture efficiency of Cu (II) ions. The ecotoxicity of CNF/NRL foam was evaluated.
Like this, the test was divided into three subsequent stages, which are schematized in
The second included the remediation process of media containing Cu (II) ions in concentrations 0, 20, and 60 μg L−1 for 48 h at 20° C., respectively above and below the pre-determined LC50 value. The lethal concentration values that kill 50% of the organisms (LC50) obtained were 33.0 and 28.36 μg L−1 respectively for 24 and 48 h of exposure to Cu (II) ions.
Two groups of foams were investigated (
All organisms died after exposure to Cu (II) solutions at both 20 and 60 μg L−1. However, for the systems treated with CNF/NRL and CNF/NRL/HA foams, no organism deaths were identified, thus indicating that these CNF/NRL foams completely reduced the toxicity of Cu (II) at doses greater than 60 μg. L−1. The similarity of the results for the media treated with CNF/NRL and CNF/NRL/HA indicated that the presence of humic acid does not interfere with the CNF/NRL remediation process, even for high concentrations of HA. It can also be observed that the foams studied here did not interfere with the mortality rate, that is, 0% of dead organisms when exposed only to aerogels, demonstrating that such materials do not present risks to the lives of aquatic organisms.
Although exemplary embodiments of the processes and products described have been presented in this report, the scope of protection is not intended to be limited to their literal meaning. Therefore, the description should be interpreted not as limiting, but merely as exemplifications of particular embodiments of the inventive concept presented here. One skilled in the art can readily apply the teachings of this description in analogous solutions therefrom, limited only by the scope of the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1020210213299 | Oct 2021 | BR | national |
| 1020220216037 | Oct 2022 | BR | national |
This application is a national stage entry application under 35 U.S.C. 371 of PCT Patent Application No. PCT/BR2022/050410, filed on Oct. 25, 2022, which claims priority to Brazilian patent application Ser. No. 1020210213299, filed on Oct. 25, 2021 and Brazilian patent application Ser. No. 1020220216037, filed on Oct. 25, 2022, the entire contents of each of which are incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/BR2022/050410 | 10/25/2022 | WO |
