PL229348B1 - Modified nanocomposite material, method for producing it and its application - Google Patents

Abstract

Disclosed is a nanocomposite material with antimicrobial properties based on cellulose filled with a silver-substituted mineral filler (zeolite), characterized by the fact that the mineral filler is Y-type zeolites, and silver is bound to the zeolite matrix in the form of cations and reduced silver nanoparticles, especially in the proportion 1: 1, and the silver content in the zeolite does not exceed 1% by weight, while the material, apart from antimicrobial properties, also exhibits sorption and catalytic oxidizing properties, confirmed at room temperature without air access; as well as the method of producing such material and its use for packaging plants, works of art, archives, monuments as well as food, pharmaceuticals and animal feed.

Description

Description of the invention

The subject of the invention is a modified cellulose-based composite material, its production method and application. More specifically, the solution relates to: 1) a cellulose-based nanocomposite packaging material, the active material of which is zeolite with metallic silver nanoparticles and silver cations embedded in the structure in a form bound to the zeolite matrix and dispersed in it; 2) a method for the production of nanocomposite packaging material containing an additional step of sonication of zeolite substituted with silver cations, which leads to their partial reduction, as well as 3) the use of nanocomposite material for packaging works of art, archives and monuments, as well as food, plants, pharmaceuticals and food for animals. The literature on the subject indicates that silver nanoparticles have both biostatic and biocidal properties, with at the same time the questioned toxicity (compared to other transition metals) towards higher organisms.

From European patent EP 0297538 B1, (publication date: June 29, 1988), a film containing zeolite with biocidal (antibiotic) properties is known. The patent describes a zeolite containing a polymer film with biocidal properties, where the zeolite content is minimized. The film is applied to at least one side of the polymeric support.

The international publication WO 2006/046837 A1, (publication date: May 4, 2006) discloses a method for the preparation of zeolite-fiber composite substrates. The application describes a method for preparing zeolite-fiber composites, and the subsequent steps involve reacting the fibers or zeolite with a binder to form an intermediate, followed by sonication using a reaction between the intermediate and the remaining zeolite or fibers to form a composite material.

A biocidal (antibiotic) zeolite is known from the European patent EP 0270129 B1 (published on: April 12, 1987). The patent describes a biocidal zeolite and a resin containing either the zeolite or the biocidal zeolite. All natural and synthetic zeolites are described, including silver ions (0.1-15%), copper and / or zinc ions (0.1-8%) and ammonium ions (0.5-15%). Other heavy metals may also be mentioned in the zeolite and the described resins include the entire body of thermosetting and thermoplastic resins.

The international publication WO 01/94512 A1 discloses a method of partial substitution (in the amount of 2-40 wt.%) Of the metal atoms (M) of the zeolite of formula M2 / n * Al2O3 * xSiO2 * yH2O by a metal from groups III, IV and Mg, Ti, Cr. Fe, Ni, Cu, Zn, Zr, Ag. the metal is mixed with the zeolite in the form of an aqueous solution of the metal salt, and the pH of the solution is in the range of 4-10.

The international publication WO 2007037195 A1 describes an antibacterial zeolite in which the exchange ions are partially or completely replaced by hydrogen and silver ions. The solution concerns a resin-based material filled with hydrogen zeolite substituted with silver cations.

Publication TW 201215561 A discloses a zeolite with modified mechanical properties extending its service life. The zeolite has been substituted with copper and silver cations, which is aimed at reducing production costs while maintaining microbicidal properties similar to purely silver. The modification consists in optimizing the ratio of Si to Al. and the use of structural additives in the form of zirconium phosphate and gelling agents.

Chinese patent application CN 102452664 A relates to a zeolite material with a modified structure by adding ash, zirconium phosphate and a refractory mortar and by optimizing the Si to Al ratio in the zeolite itself. The zeolite contains silver and copper ions to maintain similar microbicidal properties at lower cost.

The techniques offered on the market are also known - MicroChamber and Artcare paper products containing zeolites in their structure that can remove exo- and endogenous gaseous pollutants from the microenvironment of historic buildings. MicroChamber paper, however, does not contain any zeolites containing exchanged metals or metallic nanoparticles. This type of paper also has no antimicrobial activity.

The EKOPAK-plus company produces packages with a special coating of silver nanoparticles. This coating protects the products against the growth of microorganisms (bacteria, viruses and fungi) during transport and storage. Nanosilver inhibits the enzymatic processes of bacteria and contributes to the formation of active oxygen in water and air, which effectively prevents the growth of microorganisms.

PL 229 348 Β1

The main problem in using the biocidal properties of silver is the migration of its nanoparticles to the protected object (food, organisms). The harmfulness of nanoparticles to the biosphere is still the subject of scientific disputes, and the content of silver nanoparticles in food and packaging is not currently regulated in the European Union or the United States of America. However, recent literature reports indicate that nanosilver is harmful to the cells of higher organisms through the penetration of silver into the mitochondria.

As it results from the presented literature and the state of the art, there is still a need for intensive work on the search for packaging materials that would differ from those currently available in many features, including multifunctional nature, and have properties limiting the migration of silver particles from the packaging to the packed object. .

The aim of the invention is to provide a packaging material with high biocidal activity and sorption and catalytic properties with a minimum content of silver introduced into the zeolite, which silver would be dispersed in zeolite channels and chambers in the form of clusters or metallic silver atoms and silver cations to prevent their migration . The production of silver in zeolite at two oxidation states is to ensure the catalytic activity of the material. It is also an aim to provide a method of obtaining such a material with the above-mentioned characteristics.

The subject of the invention is a composite material containing cellulose filled with silver-containing zeolite, characterized in that the mineral filler is a Y-type zeolite, while the silver is in a form bound to the zeolite matrix in the form of silver cations and metallic silver nanoparticles, preferably in a 1: 1 ratio, the total silver content of the zeolite does not exceed 1% by weight. Preferably, silver ions have been introduced into the zeolite structure by ion exchange. Preferably, silver is present in addition to the silver cations in the zeolite as a result of the sonication procedure. Preferably, the zeolite matrix does not contain silver in an unbound form in the form of silver oxide clusters. Advantageously, the material according to the invention exhibits sorption properties against volatile organic compounds and gaseous pollutants as well as catalytic properties in the oxidation of volatile organic compounds at room temperature in air and at temperatures from 60 ° C in the absence of air. The material according to the invention also preferably has bactericidal and fungicidal properties, in particular against Escherichia coli, Serratia marcescens, Bacillus suhtilis and Bacillus megatherium and / or the fungi Trichoderma viride, Chaetomium giobosum. Aspergillus Niger, Cladosporium cladosporides, and Morterella alpinum.

Another object of the invention is a method of obtaining a nanocomposite packaging material, which includes the substitution of a zeolite matrix with silver (I) ions. adding the active material to the cellulosic suspension in the form of a zeolite matrix containing silver and depositing it on the cellulose fibers, shaping the furnish to the desired shape, and drying characterized by sonicating the zeolite matrix before adding the silver ion-substituted zeolite matrix to the cellulose suspension. preferably for 10 minutes in a zeolite suspension at an average power of 90 W and a solution temperature below 60 ° C, and then washing the zeolite with an aqueous solution of the disodium salt of ethylenediaminetetraacetic acid (EDTA), preferably washing with EDTA comprising the following steps: a) washing the zeolite 0, 01M EDTA at room temperature; b) rinsing for 1 hour at the boiling point of 0.01 M EDTA; c) rinsing the zeolite with 0.1 M EDTA solution; and d) rinsing the zeolite with deionized water. Preferably, during its saturation with silver, the zeolite matrix is treated with a solution of silver nitrate.

Another object of the invention is the use of the nanocomposite material according to the invention as defined above for packaging. in particular for the packaging of plants, works of art, archives and antiques, or for the packaging of food, pharmaceuticals and animal feed.

In a particular embodiment, the invention relates to a positic nock material with sorption, catalytic and antimicrobial properties. The material is made of cellulose pulp filled with a Y-type zeolite, in the structure of which clusters or metallic silver atoms are trapped, so that they do not migrate to the outside of the material. The subject of the invention is also a method of obtaining a modified zeolite exchanged with silver cations and then eluted with EDTA solution in order to remove the silver not bound to the zeolite matrix by means of sonication, which leads to the silver reaction and refining of the zeolite while maintaining its structure. The inventive material can be used as a packaging material for storage

PL 229 348 Β1 works of art, archives and antiques, as well as plants, food, pharmaceuticals and animal feed.

The first aspect of the invention is a multifunctional nanocomposite material based on cellulose filled with zeolite with clusters or silver metal atoms and silver cations trapped in the structure of its channels and chambers, showing antimicrobial, sorption and catalytic properties, which can be used, among others for wrapping plants (live and cut flowers), food and pharmaceuticals, pet food, works of art and antiques, and as insulation material.

A further aspect of the invention relates to a method for producing a material according to the invention. According to the invention, for cellulose modification, a Y-type zeolite (mesoporous material with a fotosite structure) is used, which is used as a support for silver. During ion exchange of the sodium form of the zeolite, sodium cations are replaced with silver cations (silver bound state), but it is also possible to deposit silver oxide crystals on the zeolite outer surface (silver unbound state). In the first step, after treatment with a solution of silver salt in zeolite, there is both a bound form of silver in the form of cations and an unbound form in the form of crystallites (clusters) of its oxide. The elimination of silver in the form of clusters from the surface of the zeolite is then carried out to obtain pure zeolite substituted with silver cations, i.e. a material with silver in a bonded state with minimal silver content. In the next stage, the material prepared in this way is sonicated in order to reduce silver cations to metallic silver in the form of atoms or clusters, so as to obtain a specific content of both forms of silver in the final product. Due to the fact that this process is carried out inside the zeolite, the obtained silver atoms or nanoparticles are trapped in it, which in turn reduces the risk of silver contamination of the packed products and the external environment.

Sonicators are commonly used in the chemical industry to modify the chemical properties of materials or for chemical synthesis. The approach to material design presented in the present invention allows the uniform distribution and high dispersion of zeolite in the paper material both due to i) the use of silver exchanged zeolite at the atomic scale permanently attached to the zeolite matrix by the EDTA leaching method, ii) sonication causing the zeolite dispersion and reduction of silver cations contained therein, and iii) a method of producing paper sheets with a zeolite filling.

The modified zeolite used in the present invention has a gas sorption capacity and has proven effective as a component of other products, acting as a material reducing the concentration of volatile organic compounds (VOCs) and other odor-related gases, e.g. resulting from the degradation of stored materials. In addition, silver in a dispersed state inside zeolites is a catalyst for the oxidation of VOCs, as demonstrated by the oxidation of acetaldehyde. It has surprisingly been found that in order to obtain the catalytic activity of silver at low temperatures, especially room temperature, it is necessary to have both a reduced form of metallic silver and its cations. The catalytic activity of the material is recorded at low temperatures, even without air access to the material. In this way, the present invention is new compared to other zeolite containing cellulosic materials because of this. that it can remove unwanted organic gases both by their sorption and by catalytic decomposition.

The basic ingredient for the production of the material according to the invention is pulp, which can be easily prepared in large quantities and formed into two- and three-dimensional objects such as: paper, cardboard, containers, etc. by known industrial processes, or suspended in a liquid and applied to it. in the form of a spray, as well as dried and blown into insulated spaces. Cellulose fibers have micro- and mesopores and voids, as well as a polar surface, thanks to which they can bind and hold zeolite particles.

Paper filled with the prepared zeolite, which is a special embodiment of the invention, has proven biostatic and biocidal properties against both bacteria and fungi. In addition, it has sorption properties against both (VOC) and gaseous pollutants such as SO2 or NOx. The catalytic activity of the obtained material was also demonstrated in the oxidation of VOCs at low temperatures without air access.

The invention has a number of unexpected advantages over similar prior art.

PL 229 348 Β1

In particular, in the present invention, silver is present not only in the form of cations mentioned in the zeolite, but also in the form of atoms or nanoparticles trapped in the zeolite structure. As a result, the catalytic properties of the material, which oxidizes volatile organic compounds already at room temperature, and even partially in the absence of air, have been improved. A high dispersion of the material was also obtained, which additionally contributed to the improvement of catalytic activity. On the other hand, the silver content was reduced to less than 1% by weight. The use of zeolites has a stabilizing effect on silver, which is the active ingredient of the entire material. In particular, one should consider limiting the migration of silver nanoparticles (accumulated in the packaging material) to objects or substances stored in the packaging.

The invention described in the present application differs significantly from the prior art products in that the proposed material is a multifunctional paper product that absorbs contaminants and exhibits antimicrobial and catalytic properties due to the use of silver zeolites in two oxidation states. In the present solution, zeolite aggregates with trapped cations and silver atoms or clusters in their structure are immobilized on purified cellulose fibers using chemical and physical sorption methods to form a zeolite-fiber composite material. With the use of filtration and sedimentation methods, it is possible to produce a composite material consisting of a zeolite-fiber component enriched with a layer of functionalized zeolites.

The invention should find application in the area of securing works of art and monuments. The developed material can be part of cardboard elements in contact with a work of art, in particular for luminaires that will come into contact with the exterior walls of buildings. During winter, exterior walls, especially in poorly insulated buildings such as historic houses and churches, can become cold, creating a moist microclimate inside the building. This is a particularly dangerous situation in the spaces behind and between the objects of interest, where the risk of mold growth increases. The present invention, prepared in the form of a cardboard and used as a mounting support or as a back wall for an object in a frame, can serve as a preventive tool to limit the growth of mold. As a result of increased humidity, water bridges will form between the cardboard board and our facility, which should further strengthen the biostatic effect. Another use in this group may be for wrapping material of organic materials (fabric, leather, parchment, paper, wood, fossils, etc.), which are also susceptible to microbial attack. Tissue paper can also be prepared and delivered as a ready-to-use kit in the event of a disaster such as a flood or flooding. In the case of this type of disaster or breakdown, wet items are often wrapped in tissue paper and wrapped in wipes before vacuum packing. In the next step, items are kept at low temperature, which inhibits or significantly reduces the growth / development of microorganisms. The present invention would provide in this case the possibility of additional antimicrobial protection. In all the cases presented, also the sorption properties of the present invention are of importance. For the storage of archives or library collections, boxes or envelopes with these catalytic, sorption and biocidal properties can be used.

In protecting the works of objects of cultural value, it is necessary to cut them off from the influence of gaseous harmful air pollutants, such as acid gases present in high concentration in urban agglomerations (NOx, SO2, CO2), as well as to remove gaseous products of its degradation from the atmosphere surrounding the object, which also often have a destructive effect on the object. The undesirable effects of microorganisms (fungi and bacteria) on works of art are known and described many times in the literature on the subject.

As a packaging protecting historic and archival objects, the presented invention is the only currently known product that has both antifungal and antibacterial biocidal and biostatic properties, and at the same time has sorption properties. Stabilization properties, multi-functionality, the use of renewable materials, simple and scalable production methods and the approach in line with the "green chemistry" trend distinguish the present invention from other products commercially available on the market.

The developed packaging material was subjected to comprehensive physicochemical tests. They have shown, among others, that both silver cations and metallic silver in a dispersed form in zeolite are permanently bound to it and do not penetrate into the environment, which is important due to

PL 229 348 Β1 invariability of biostatic properties of the material and safety of its use. The conducted tests for the presence of silver in the aqueous filtrate, which was in contact with the developed material (the sample marked PZAgO was used) gave a negative result - both cold and hot into the water, neither ions nor silver nanoparticles were extracted, which was found by chloride ion test and XRF analysis.

The transfer of silver nanoparticles and silver ions during contact with model food can be checked using appropriate analytical techniques. In the tests that the authors of the application performed using the XRF technique, no silver was found on agar media in long contact with silver-containing paper discs.

Moreover, it was shown that thanks to the use of sonication and obtaining silver at two oxidation states in a zeolite matrix. the material exhibits catalytic activity in the afterburning of volatile organic compounds at room temperature even in the absence of air and has significant biocidal activity. This was confirmed by in situ sorption and catalytic tests with the analysis of intermediate products of the DRIFT / FTIR reaction. Thanks to sonication, high fragmentation of the material was obtained, which could also contribute to the unique catalytic activity. The silver content in the material was brought below 1%.

The results of microbiological tests confirm the high activity of the material for strains of bacteria and fungi typically found in food or archives, comparable, however, to non-sonicated material containing only silver cations.

The results of the physicochemical and microbiological analyzes of the invention are shown in Figures 1-15. Fig. 1 shows the quantification of the silver cation exchange in the zeolite in the form of an exchange isotherm prepared by X-ray fluorescence (XRF) analyzes of the silver content in the zeolite: Figs. 2-5 refer to studies of the effect of sonication on silver exchanged zeolite; Fig. 2 shows the results of atomic force microscopy (AFM) analyzes of the sonicated zeolite topographic material (AFM topographic maps (first column) and crystallite edge distribution obtained by the non-contact method (second column) of sonicated Y zeolite samples); Figure 3 shows the results of diffractometry analyzes of the sonicated zeolite samples; Fig. 4 shows the results of quantitative and qualitative analyzes in infrared spectroscopic in situ (in situ FTIR) for CO sorption on zeolite materials subjected to sonication and on reference materials (a) FTIR spectra of carbon monoxide (II) absorbed on Ag 'ions in the tested zeolite Y samples, (b) Comparison of zeolite activation conditions; Fig. 5 shows the results of analyzes of silver content in paper material filled with sonicated zeolite; 6-8 show the characteristics of zeolite filled paper material; Fig. 6 shows the stability of the paper material as determined by measuring the pH of the samples at various stages of the preparation and the reference samples; Fig. 7 shows the durability of the paper material after aging tests performed according to ASTM standard and expressed as degree of polymerization (DP) of cellulose; Fig. 8 shows the life of zeolite Y-filled paper in terms of breaking force at zero pinching; Figures 9 and 10 show the results of sorption and catalytic tests for acetaldehyde in an airtight and in air, respectively, performed by in situ FTIR with a diffuse reflection shifter (DRIFT) on sonicated zeolite and non-sonicated zeolite. Fig. 9: obtained at different temperatures in He flow for a sample of A) sonicated Y zeolite (ZAgO_EDTA), B) unssonicated Y zeolite (ZAg ⁺ _EDTA. Spectra C and D are an enlargement, respectively, of A and B spectra in the vibration range from carbonyl groups; Fig. 10: In situ FTIR (DRIFT) spectra of the transformation of sorbed acetaldehyde obtained at different temperatures in the air flow for a sample of A) sonicated Y zeolite (ZAgO_EDTA), B) unssonicated Y zeolite (ZAg'_EDTA presented in the vibration range from carbonyl groups; Fig. 11 presents the quantitative results of DRIFT spectroscopic studies presented in Fig. 9 110, while the quantitative interpretation of the bands from acetaldehyde vibration at 1780 cm ^-1 was presented as the degree of conversion X = (I25-It) / I25, where I denotes the intensity of this band at appropriate temperatures (the intensity of the band at 25 ° C was taken as the initial amount of aldehyde); and acetic acid at 1680 cm ^-1 presented as its degree of conversion Y calculated from the intensity its band at appropriate temperatures Y = li7lmaxT (the maximum intensity observed for a given sample at a given temperature lmaxT was used as a reference value), A) for the experiment without air, B) for the experiment in air flow (in this case, the result obtained in the experiment without air due to the immediate reaction of the aldehyde). Figure 12 shows the results of acetaldehyde sorption in the air for a paper sample with sonicated zeolite (FTIR (DRIFT) spectra of acetaldehyde sorption without

PL 229 348 Β1 air access for a paper sample filled with sonicated Y zeolite (PZAgO_EDTA)). Figure 13 shows a comparison of the microbial activity of different silver-exchanged and sonicated zeolites (E. coli biocidal activity for different zeolite materials (9000 counts control)); Fig. 14 shows the results of microbiological tests for bacteria; Figure 15 shows the results of microbiological tests for fungi.

The invention is described in more detail in the following embodiment, which, however, should not be equated with the full scope of the invention.

Example 1. Preparation of the material according to the invention

Ion exchange of zeolite

The basic zeolite used for the research was Y zeolite, for which the ion exchange procedure was optimized, as shown below. ZSM-5 and MCM-56 comparative zeolites were also used for the tests. The ion exchange procedure was as follows. After placing 50 mg zeolite in 10 cm ^{3 of} a 0.1 M aqueous solution of Agnos so prepared suspensions were shaken at 300 rpm / min. Shaking was carried out in conditions with no light. After the assumed sorption time, the suspension was centrifuged at a speed of 2000 rpm. Centrifugation according to the performed optimization was carried out 5 times. The rinsing pellets were dried at 120 ° C. After conditioning for 24 h, the dried pellets were weighed with an accuracy of 0.1 mg. The samples were placed in a beaker and then poured over with 5 cm ^{3 of} 65% nitric acid solution (V). The slurry was heated to boiling and held at that temperature for a period of 15 minutes. After cooling, the suspension was centrifuged (2000 rpm) and the supernatant solution was quantitatively transferred to a 25 cm ³ volumetric flask. The sediment remaining at the bottom of the test tube was flooded with deionized water and shaken until resuspension was formed, which was then centrifuged. The supernatant solution was transferred to a volumetric flask which contained the solution after the first centrifugation. This procedure was repeated a total of 5 times. The precipitate was dried and tested for any silver remaining therein. The solution in the flask was made up to 25 cm ³ with deionized water. The silver solution prepared in this way (corresponding to the initial silver content in the zeolite) was analyzed by means of XRF using the calibration curve method.

Determination of silver in zeolite by X-ray fluorescence spectroscopy (XRF)

Measurements were made using an ED-XRF (Quant'x - Thermo) spectrometer. Measurement parameters: t = 60 s, measurement in an oxygen atmosphere, thick copper filter, large measuring cup. The Cat for silver emission line (integrated with background cut-off in the range of 21.46-22.60 keV) was selected for the determination. The determination of silver was carried out in HNOs solutions with dissolved zeolite, and the results are presented in Table 1. The determination of the silver content has a 5% error, determined on the basis of the reference to the blank. Problem results from the scatter of the - correlation coefficient for fitting the calibration curve prepared on the basis of the analysis Agnos standard solutions (see Table 1) is R ² = 0.9819. The error is also brought about by incomplete elution of silver from the zeolite with hot HNOs. The content of silver in the part of undissolved zeolite in the form of sediment was also checked, but the amount of silver in the sediments did not exceed 1% by weight. For this reason, determinations of silver content in zeolite were based on analyzes of dissolved material.

The sorption isotherm determined by means of XRF showed that the half exchange of zeolite with silver ions under the described conditions is achieved after approx. 1 h (Fig. 1). Zeolite Y selected as a component of the material is maximally saturated with silver ions after 2 hours of exchange with 0.1 M AgNOs solution under the conditions described above, and the silver ion exchange isotherm, as in the case of other metals, tends asymptotically towards the maximum value. Further exchange (over 2 hours) does not increase the silver content in the zeolite, and the subsequent results are within the error limit of the determination. Measurements of the water content in the samples presented earlier showed that this amount is practically unchanged (2.5% spread of results). Similar results were obtained for the reference zeolite type ZSM-5 and MCM-56. The isotherms did not differ in shape, and only slight differences could be observed in the ion exchange rate of the entire zeolite volume. Complete filling was achieved after just 1 hour.

PL 229 348 Β1

Table 1. The results of studies of silver content in solutions after washing zeolite after ion exchange with hot HNO3. The penultimate position in the name of the sample (0.1 means the concentration of silver in the solution, AgNO3 from which the exchange was made), the last position in the name means the ion exchange time.

Mark Ion exchange time '[h]' Number of counts Silver content [mg Ag / 'g zeolite] YAg_0.l_i 1 280,000 94.0 YAg_0.1_2 2 429,500 263 YAg_0.l_3 422 800 253 YAg 0.1 20 twenty 396 006 246 YAg_0.l_29 29 423 700 265 YAg_0.l_39 39 374,800 225 YAg_0.l_92 92 439 200 254 Data for the calibration curve AgNOi solution concentration [md / diTt '] * - 0.1 681 900 - 0.05 - 430 100 - 0.033 * 365 600 - 0.025 298 100 • - - determined concentration [mobdrn '] Blind COS - 424 900 0.0475

Preparation of the zeolite matrix

On the basis of the determined sorption isotherm, 1 h was selected as the optimal time of ion exchange. Three portions of 5.00 g each were weighed. The first portion was placed in a beaker and covered with 100 cm ^{3 of} a 0.1 M aqueous solution of nitrate (V) silver. The suspension was shaken for one hour at 300 rpm. The precipitate was filtered off and the recovered nitrate solution was reused for sorption for the second and third batches. The pellets were rinsed with 500 cm ³ of distilled water to wash out excess silver nitrate. After the pellets were dried at 60 ° C, they were mixed to obtain a homogeneous sample. From the thus prepared basic material, a representative sample was collected in order to perform physicochemical analyzes (the results are presented below). The base material (silver exchanged zeolite) was used as a filler for paper sheets in the further preparation.

Modification of the structure and composition of the zeolite matrix

Elution with EDTA was applied to the final prepared sample to remove non-zeolite silver. Thus, in the case of sonicated samples this was followed by sonication. However, due to the comparison of the sonicated samples with the unssonicated reference samples, the elution procedure is described first in the sequence. Optimization of the elution procedure was developed for non-sonicated samples and further applied in the same manner to the sonicated samples described in the present invention.

Rinsing out unbound silver with EDTA salt solution

PL 229 348 Β1

Before applying the procedure for removing silver ions from the outer surfaces of zeolite crystallites, the effect of washing on sample dealumination was checked. For this, reference samples of crude zeolite were washed with an aqueous solution of disodium ethylenediaminetetraacetic acid (EDTA). The procedure consisted of three stages:

a) washing the zeolite on a funnel (paper filter) with 150 ml of 0.01 M EDTA solution (room temperature),

b) rinsing at boiling point with 150 ml of 0.01 M EDTA solution (holding time 1 hour),

c) washing with 150 ml of 0.1 M EDTA solution.

The rinsing was carried out in a quality funnel with the use of quality paper points. The appropriate solutions were dosed in such a way that the sediment was immersed in the solution throughout the washing period. The sediment was washed with a fresh portion of complexone each time, no recirculation of solutions was used. In the case of hot washing, the modified material was placed in a beaker and poured with 0.01 M EDTA solution. The solution was stirred with a magnetic stirrer and kept at reflux for one hour.

Zeolite dealumination is excluded

The filtrates were centrifuged (4000 rpm, 4 min) and then characterized by ASA atomic absorption spectrometry (Zeeman polarized atomic absorption spectrometer - Z 2000, HITACHI) in order to eliminate the possibility of zeolite dealumination during leaching. NMR analyzes were also performed using a Bruker 400 MHz spectrometer with a solids adapter. Table 2 shows the results of the tests performed on the filtrates after treatment of zeolites with Na2EDTA. The results presented in Table 2 show that treatment of the zeolites with cold 0.01 M EDTA solution did not leach the aluminum from the structure. As a reference sample, a zeolite heated in EDTA aqueous solution for 1 hour was selected, in which dealumination took place.

In this case, aluminum was detected in the filtrates by ASA. However, the lack of detection of aluminum in the remaining solutions is not an unequivocal confirmation of the lack of dealumination in the zeolite lattice, hence the material analyzes were extended by the 27AI MAS NMR method used to determine the degree of dealumination. For this purpose, the dried pellets after washing with an aqueous EDTA solution were tested for changes in the aluminum NMR signal. The NMR spectra were normalized against the surface area of the main signal for the aluminum tetrahedral unmodified Y zeolite starting material (A = 1.0000). The values for the measured samples are presented in Table 2. The obtained results indicate that the selected washing method does not cause dealumination, which proves the thesis that after chemical treatment (washing with 0.01 M EDTA) the zeolite does not change the structure of the crystal lattice. Note that when the zeolite is heated in an EDTA solution or when a higher concentration of EDTA is used, structural changes occur. There was a loss of 6% for a wash with 0.1 M EDTA.

Table 2. The results of the clay determination in the filtrates after EDTA washing

Mark Treatment method ASA method (j.u.j NMR method - percentage of aluminum loss from the lattice * ZAg + 0.01 125 Cold 150 cm3 0.0! M EDTA 1 (not detected) 0.05 ZAg + _O.0l Tl 00 Heated for one hour in 0.01 M EDTA 3.80 ZAg + O.l T25 Washed J 50 cm3 0.1 M EDTA and (not detected) 6.10

* results related to standardized zeolite dry sludge collected after the process described in the second column of the table. The designations T25 and T100 refer to a temperature of 25 and 100 ° C, respectively.

PL 229 348 Β1

Optimization of zeolite washing

In order to optimize the time and multiplicity of washing of the silver-exchanged zeolite materials with EDTA in order to complex the silver ions on the outer surfaces of the zeolite crystallites, XRF analysis of the washing filtrates (or solutions after centrifuging the suspensions) was performed.

Table 3. Quantitative analysis of XRF - silver transition line intensity with successive EDTA washes for ZAg + Y zeolite sample after ion exchange (shaking).

Rinsing multiplicity (volume V ~ 10 times ________, _____ cm ³ ) _________________________ Analytical signal for silver [keV] 1 and 710 009 2 224 776 3 13,700 4 3 134 5 2 215 6 2 731

The above results were obtained for a freshly prepared zeolite sample after ion exchange. As the analysis of the results in Table 3 shows, sufficient rinsing of the zeolite from ions not associated with the structure is obtained after 5-fold washing, when the silver signal is at a constant minimum level (no studies on the effect of washing on the bound ions in the matrix have been conducted). The silver washout rate from zeolite compared to the first wash is almost 100%, while the washout ratio between the 4th and 5th wash is less than 0.1% so there is practically no loss of active material (with some approximation, because for fresh materials, it is very difficult to obtain such a structure that would be completely resistant to washing with water). Due to this result, it was found that 5-fold washing with water is sufficient from the point of view of silver washing, at the same time it complies with the assumptions of washing optimization, which was to ensure a well-defined structure of materials with a minimum amount of silver only bound to the zeolite matrix.

Additionally, similar analyzes were performed for increasing volumes of the EDTA solution used. For this purpose, the same mass of zeolite exchanged with silver ions was washed with successive portions of water, 50 cm ^{3 each} . ^{2 cm 3 of the} solution were taken from the filtrate prepared in this way and analyzed by means of XRF. As can be seen from the data presented in Table 4, in this case also low values of the signal derived from silver were obtained (the ratio of the last to the first result is 0.13%).

Table 4. Quantitative XRF analysis - washing of a sample of zeolite Y with silver ions ZAg + with water.

The sum of the volume of a portion of water [cm ³ ] Analytical signal for silver * [keV] 0 1 047 293 50 51 722 100 3 019 150 1 393

♦ standardized signal for sample weight and filtrate volume tested.

PL 229 348 Β1

The use of an EDTA solution has been shown to be a good way to minimize the amount of silver in the samples to the level of silver bound to the zeolite matrix. This is to prevent silver from migrating to the environment, especially in food, which is often very humid. It is also worth noting that after rinsing with 40 cm ³ EDTA, a stable washout level is obtained (Table 3). However, the leaching rate does not decrease as with water. Evidently, the EDTA solution, after complexing all ions weakly bound to the zeolite structure, can access the bound silver ions exchanged in the zeolite.

At the next stage of optimization, the stability of finished zeolites exchanged with silver ions in aqueous solutions was examined (this time after drying the samples previously - the starting material). The degree of elution of silver ions by water and EDTA was compared. The results are presented in Table 5.

The results presented in Table 5 show that the zeolite filler loses insignificant amounts of silver in the aqueous environment. Moreover, after rinsing with 50 cm ^{3 of} water, the silver content in the post-extraction solutions is below the quantification limit. The sample washed in this way was then rinsed with EDTA solution successively with 10 cm ³ portions (the colored part in Table 5). The efficiency of eluting silver ions with EDTA solution is much higher than for water (from 150 to 200 times) and increases with increasing volume of the solution. At the moment when the water was no longer able to rinse the silver ions, a large silver signal was obtained for the EDTA solution.

Table 5. Washing of the same sample of zeolite Y exchanged with silver ions (ZAg +) with water followed by EDTA. In the results presented in Tables 3 and 4, the same portioned sample was used.

The sum of the water volume in the subsequent rinsing with 10 cm ⁵ [cm ^? ] XRF analytical signal for silver [-] 10 2 129 twenty 737 thirty 56! 40 399 50 <ŁW The sum of the EDTA volume in the subsequent rinsing with portions of JO cm ' 10 EDTA 150 045 20 EDTA 55 039 30 EDTA 23 001 40 EDTA 22 100

In addition, optimization of the concentration and amount of EDTA solution used to wash the Ag * cation-substituted zeolite samples was performed on the basis of XPS surface analyzes for the Ag 'band with a binding energy of 432 eV in the spectrum. Table 6 shows the results of the quantitative analysis of modified zeolite samples (symbols mean, respectively: ZAg ⁺ means zeolite substituted with silver ions, not rinsed, ZAg ⁺ _H2O - zeolite substituted with silver ions, washed with deionized water. ZAg ⁺ _0.01 M EDTA 150 - zeolite substituted with silver ions rinsed 150 cm ³ 0.01 M EDTA and water, ZAg ⁺ _0.01M_EDTA_150 - zeolite substituted with silver ions rinsed 150 cm ³ 0.1 M EDTA and water ZAg + _0.01 M_EDTA_300 - zeolite substituted with silver ions rinsed 300 cm ' ¹ 0.01 M EDTA and water.

The results show that increasing the EDTA concentration from 0.01 M to 0.1 M for the samples ZAg + _0.01M_EDTA_150 and _Ag ⁺ _0.1 IM_EDTA_150, respectively, results in further leaching of silver from the

PL 229 348 Β1 surface of zeolite crystallites. In order to minimize the amount of silver, a more concentrated EDTA solution was used for further washing tests. On the other hand, an increase in the amount of washing solution from 150 to 300 cm ³ for the samples ZAg + _0.1M_EDTA_150 and ZAg + _0.1M_EDTA_300, respectively, does not cause further leaching of silver, and the differences in the determined amounts of Ag 'are within the measurement error. The results of the XPS analysis are consistent with those obtained with the XRF. EDTA, after rinsing out ions weakly bound to the structure (approx. 40-50 cm ³ ), is still able to rinse silver from the structure, but the degree of leaching is at a low and constant level.

Table 6. XPS quantitative results for silver on the surface of the zeolite crystallites after washing with EDTA.

A sample EDTA concentration [mol / dnfj Washing [cm ³ ] Signal for. silver after normalization [j.u.] and 2 ZAgi - 1.05 ZAg \ H ₂ O 150 HjO 150 HjO 1.19 ZAg '0.0IM.EDTA 150 0.01 150 EDTA 150 HjO 1.25 ZAg '0.1 M EDTA 150 0.1 150 EDTA 150H? O 0.29 ZAg'_0.1 M_EDTA_300 0.1 300 EDTA 150 HjO 0.31

The optimization of rinsing of the samples of the starting materials showed that the applied preparation allows to obtain stable materials with a minimum amount of silver strongly bonded to the zeolite matrix, which were used for further modification of the material.

Sonication

Sonicated samples of silver cation substituted zeolites were prepared as reference samples containing metallic silver nanoparticles dispersed in the zeolite matrix. These samples were necessary to compare the biocidal properties of silver and redoxed silver cations. The method of sonication of samples is presented below.

Procedure for sonication in solutions

The synthesis of metallic nanoparticles as reference samples was carried out in an aqueous solution of AgNOs (0.1 M). The first step was to check whether nanoparticles are formed during the process, what size they are and how stable they are. An ultrasound generator with a power of 20,000 kHz was used for the synthesis. In the first stage, the possibility of synthesizing silver nanoparticles in AgNOs solution without additives was investigated. In subsequent steps, the procedure was changed in such a way that increasing amounts of ethanol (max. 5 cm ³ ) were added to the solution. The last step was to apply an inert gas (argon) blast for 60 minutes before turning on the ultrasound, as well as a reducing mixture (H2 / He5 / 95% voi) during the sonication process.

Sonication procedure in zeolite suspension

Silver nanoparticles were also synthesized in a zeolite matrix. For this purpose, weights of 1.00 g of zeolite Y 100 were prepared and placed in a beaker. The zeolite was flooded with 150 cm ³ of distilled water and purged with argon (time 15 minutes). The sonication process was carried out using an ultrasound generator (OSonica S-4000, head with a diameter of 7 ₂ ". Chest = 90 W. Ecaik. = Approx. 97,000 J (30 minutes each) for a period consistent with the data in Table 18. Sonication conditions - average power of 90 W, the temperature of the solution - below 60 ° C. In the final phase, blowing the zeolite suspension was used for an hour and, during sonication, with the reducing mixture.

PL 229 348 Β1

Table 7. Sonication time of zeolite samples.

No. Mark* Sonication time (min] AND with 0 2 Z_son_i0 10 3 Z_son_20 twenty 4 Z_son_30 thirty

The influence of sonication on the structure of zeolites

The study of the effect of sonication on zeolite dispersion was performed using atomic force microscopy (AFM, Park Systems, model ΧΕ100). The images presented in Fig. 2 show that the fragmentation of the samples changes with increasing sonication time. In the case of a sonicated sample for 30 minutes, a drastic drop in graining can be noticed. When estimating the size of the grains, it can be seen that for the sample of unssonicated grains they have an average size of approx. 3 µm, and for the sample Z_son_10, the sizes are respectively approx. 10 times smaller. For the longest sonicated sample Z_son_30, their repeated growth is observed, although the edge shape analyzes indicate that larger grains consist of a combination of fine grains. When the sonication time is longer. the obtained samples were difficult to filter as they did not settle on the filter and got to the filtrate (hence it was necessary to centrifuge these samples). This has a significant impact on the handling of the material - difficulties in retaining the active material in the cellulose matrix. However, due to the lack of change in the nature of the material, a sonication time of 30 minutes was chosen, considering changing the material drainage procedure for this particular sample.

Investigations of the sonication effect on the zeolite structure by means of X-ray diffraction (XRD) were performed for the original (not listed) Y zeolite samples subjected to sonication (Table 7). No differences were found in the diffraction patterns (Fig. 3). Characteristic reflections related to the structure of the Y-type zeolite can be identified on the diffractograms, e.g. 7.42.10.05.11.93, 20.40, 37.73. Based on the conducted research, it can be concluded that the treatment of zeolite samples with ultrasound does not affect their phase composition.

The form and amount of silver in zeolite

The aim of this part of the research was to determine the composition of zeolite and the form of silver present in it. The research also made it possible to determine the sorption capacity of zeolite for a CO molecule. The technique of in situ infrared spectroscopy (in situ FTIR) with the use of the probe molecule for Ag * cations was used for the research (the band of CO vibrations adsorbed on Ag 'occurs at 2170 cm ¹ ). The measurements were made in two ways:

Sorption of carbon monoxide (II) at room temperature was done to determine the quantitative ratio between the silver atoms in the first and zero oxidation states. The results are shown in Figure 4. The analyzes show that both sonication and washing during the preparation of materials with an aqueous solution of Na2EDTA significantly affect this ratio (reduction of Ag 'content). Washing with EDTA solution was intended to wash out the extra-network (not exchanged with zeolite) silver ions, which is reflected in the lower amount of adsorbed CO relative to the reference sample (compare ZAg 'and ZAg'_EDTA). According to the performed ion exchange (Fig. 1), the time of ion exchange guarantees a half exchange of sodium ions with silver ions. The determined exchange time and the type of zeolite (here Si / AI = 2.5) thus determine the total number of silver ions per zeolite unit cell equal to 27. The analysis carried out shows that in the case of zeolite replaced with silver cations, this number per cell is almost 2 times smaller and amounts to 15.5 ions / cell. Part of the silver ions is thus reduced (or located in places inaccessible to carbon monoxide (II)).

PL 229 348 Β1

Activation of zeolite samples by means of vacuum conditioning was carried out at two temperatures - room temperature and at 80 ° C and 450 ° C. Measurements at the temperature of 80 ° C were made in order to check whether it is possible to remove water from the zeolite by evaporation, while maintaining the intensity of the band originating from sorbing carbon monoxide (II), which enables the analysis of the samples. For the Y-type zeolite, this band is 2175 cm ^-1 and is attributed to the Ag ⁺ (CO) monocarbonyl moiety. As shown in Figure 4, (in part b), only the samples activated by vacuum at room temperature had a sufficient band intensity. For temperature activation, this band practically disappears at both 80 ° C and 450 ° C. Therefore, the band recorded after activation with vacuum at room temperature at 2175 cm ^-1 was chosen as a marker for the silver (I) content in zeolites. The use of vacuum enabled the desorption of water from the zeolite from the silver coordination zone, which enables the quantitative interpretation of the results of CO sorption on Ag ⁺ centers, without introducing errors in the determination.

The results obtained after the activation of zeolites exchanged with silver at room temperature show that there is a high possibility of silver (l) presence in hexagonal heaps, due to the smaller number of -OH groups than in unchanged zeolites. Activation at elevated temperature (80 ° C) shows that there is migration and reduction of silver in the zeolite, which in turn is associated with the appearance of -OH groups, which must now balance the negative charge of the lattice, which cannot be done by metallic silver groups.

The degree of silver reduction is greater for the shorter sonicated sample. In the case of the sample sonicated for 30 min and additionally rinsed with EDTA (ZAg ⁺ _son_30_EDTA), washing out of silver cations with an effect comparable to that of the unssonicated sample (ZAg ⁺ _EDTA) is observed.

Table 8. Number of silver ions per unit cell in zeolite.

A sample Number of at. Ag + 7com. el. Ag 'fraction in the sample Ratio at. Ag7Ag ZAg + 15.5 1 1: 0 ZAg + _EDTA 6.4 1 1: 0 ZAg0_son. 10 8.5 0.6 3: 2 With Ag0_son_ 10 EDTA 3.0 0.5 1: 1 ZAgO_son_ thirty 14.0 0.9 9.Ί ZAg0_son_30 EDTA 5.0 0.8 4: 1

The presented test results are complementary to the XPS and XRF tests. Washing with EDTA solution reduces the amount of silver ions (approx. 3 times). In turn, the sonication process leads to the reduction of silver ions (formation of -OH groups), but only after a short time (10 min). Longer sonication causes silver re-oxidation.

From the results given in Table 8, the degree of silver reduction in a given sample (washed or unwashed series) can also be calculated. It is assumed that the maximum amount of silver cations for the unwashed series is found in the ZAg ⁺ sample, and in the EDTA washed series, puw ZAg ⁺ _EDTA. Thus, for the reference samples, the fraction of the amount of silver cations in the sample is 1. Note that by selecting the sonication time and applying the elution procedure, the Ag ⁺ : AgO ratio in the obtained material can be selected. From the point of view of the material's operation as a catalyst, the ZAg0_son_10 EDTA sample with a balanced amount of oxidized and reduced silver was selected as the optimal material, which is important from the point of view of catalytic activity. In the further part of the study, it will be abbreviated as ZAgO_EDTA.

Example 2 Development of a method of forming paper sheets filled in the zeolite paper sheet samples were prepared by the disintegration of 4.00 g of Whatman filter paper in 400 cm ³ of distilled water with a homogenizer (IKA Ultra-Turrax T18). According

PL 229 348 Β1, depending on the type of sample prepared, an appropriately prepared active material in the form of zeolites was added to the prepared paper mass (9 Table 9).

Table 9. Preparation method of model packaging material samples

Mark* Active material The method of preparing the active material additive to the paper pulp P. lack not applicable PAg + Ag ' 0.51 g of silver nitrate (V), corresponding to 0.003 mol Ag in the volume of the material PZO Y l .77 g of zeolite Y in the furnish PAgO Ag ° 0.51 silver nitrate (V), in suspension with the pulp sonicated for 10 minutes (A = 100%) PZAg + AgY 1.77 g of zeolite Y replaced by Ag '. BEYOND AgY and Ag ’ 1.77 g of zeolite Y replaced Ag 'sonicated for 10 minutes (A ~ 100%) PZAg + _EDTA Y zeolite exchanged with silver ions washed with EDTA 1.77 g of zeolite Y exchanged Ag * washed with 300 cm '0.1 M EDTA solution and 150 cm ⁵ of distilled water PZAgO_EDTA Y zeolite exchanged with silver ions, washed with EDTA and sonicated 1.77 g of zeolite Y replaced Ag 'washed with 300 cnf OJ M EDTA solution and 150 cm ³ of distilled water and sonicated for 10 minutes (A-100%)

The furnish was prepared as described in Table 8 and formed into sheets of paper using a Biichner funnel or a vacuum table. A hydrophobic fabric was used as a supporting element for the drained paper pulp. The sheets were dried on the glass in a room atmosphere. The samples were cut from the dried paper sheets in the form of disks 6 mm in diameter. The samples were secured by placing them in paper envelopes. The samples were disinfected at the stage of microbiological tests.

In addition to ion exchanging silver with zeolites selected as the active material added to paper sheets, it was necessary to develop appropriate procedures for the preparation of zeolite-filled sheets.

Primary procedure

In the primary aqueous sheet manufacturing procedure, the active material (here zeolite Y) was mixed with the furnish dispersed in deionized water. A Buchner funnel was used at the beginning of the optimization of the procedure to form the paper discs. Such a procedure meant that the paper mass (let us recall, with a volume of 400 cm ³ ) had to be drained over an area with a diameter of approx. 25 mm. Therefore, it was necessary to slowly pour the paper pulp through the sleeve adapted for this purpose. After drying, the disks differed in appearance depending on the side of the disk (bottom or top on the filter cloth). Due to these differences, the discs were tested to determine the homogeneity of the distribution of the active material in the sheet volume. The paper discs were examined by XRF spectroscopy on each side for silver content. The results for all sheets tested showed that there are significant differences in the amount (up to 10%) of silver depending on the side

PL 229 348 Β1 sample. Such a difference could influence the analysis of microbial activity as the results would depend on how the paper disks are arranged on the medium. The observed differences in the distribution of the zeolite material probably resulted from the separation of material components as a result of filtration. Additionally, note that in the case of thick paper samples of 3 mm, the so-called the mass attenuated coefficient (mass attenuated coefficient) associated with the attenuation of the XRF signal. In such a case, only a certain layer of the material reached by X-rays is analyzed. Taking into account the fact that during filtering and forming of the paper sheets, silver segregation takes place (zeolite sedimentates faster than the pulp), the silver content can only be measured in this way in the paper layer in the unenriched and not in the entire sample and vice versa. It was therefore necessary to change the method of producing the paper sheets in such a way as to guarantee an even distribution of the active material.

Modified procedure

In the modified procedure, a vacuum table was used, thanks to which it was possible to create paper sheets with a size of approx. 15-20 cm. On such a large surface, with the same suction force, the filtration time has become incomparably shorter. The sheets got rid of the water at practically the same time that the furnish appeared on the filter cloth. The sheets were removed from the filter cloth and placed on a glass (flat surface) to dry. Samples for testing (now about 6 mm in diameter) were taken from the prepared sheets. In order to determine whether there were differences in the concentration content depending on the side of the sheets, an XRF analysis was performed as in the previous case. The obtained results showed that there is no difference in the amount of silver depending on the side of the sample sheets (differences below the standard deviation). Paper sheets made with the new method were treated as model samples in physicochemical tests and determination of sorption, catalytic and microbiological activity.

Loss of active material during sheet formation

Despite the optimization of the paper sheet manufacturing procedure to maintain its homogeneity, it was necessary to determine the degree of loss of active material. This is due to the fact that said zeolite was placed in an aqueous environment in which the leaching of silver from the zeolite structure could take place. Moreover, there was a concern that some of the zeolite (especially in the case of sonicated samples - cf. the effect of sonication on the zeolite structure described later in this paper) could be washed out during filtration. Such a possibility appeared especially in the first moments of filtration, when the zeolite was in direct contact with the filter paper and could pass through it. For verification, the sheet forming system was equipped with a scrubber to collect the permeate. The filtrate was then subjected to XRF analysis for the detection of silver ions. The results obtained indicate that silver was lost in the forming of the sheets. The analysis was based on the Ka line for silver. It should be emphasized, however, that it was a semi-quantitative analysis. Due to the size of the system and the problem with quantifying the entire filtrate, quantification did not make sense. Due to the detection of silver in the filtrates and the problem with quantitative measurements of the silver content, the final paper sheets were tested for silver content separately. The determination procedure was identical to that for zeolites. however, instead of zeolite, a paper sample was digested.

Determination of silver concentration in paper sheets

During the optimization of the silver content in the final material, the quantitative analysis was synchronized with the microbiological analysis in order to determine the minimum amount of silver in the paper giving a satisfactory biocidal activity. Table 10 shows the microbial activity against the tested model organisms.

Table 10. Microbiological activity of paper materials with different silver content for selected test organisms.

Silver content mg Ag / g paper Bacteria Mushrooms 87 -r T. 7! 4- -t 4ft r -F JO AND + +/-

PL 229 348 Β1

The silver content was determined according to the following procedure:

0.02 g of paper is weighed, about 7.5 ml of 65% nitric acid (V) are poured in and brought to the boil. The slurry was held at reflux for 15 minutes while stirring. The suspension was quantitatively transferred to a tube and centrifuged at 4000 rpm. The supernatant solution was quantitatively transferred to a 25 ml volumetric flask. The sediment in the test tube was covered with distilled water, mixed to obtain a suspension, and then centrifuged again. The procedure was repeated four times. The solution in the flask (after the end of the procedure) was made up to the mark. These solutions were the basis for the determination of silver by means of XRF.

The concentration of silver in the prepared samples was determined by the XRF method from the calibration curve. The results are presented in Fig. 5 and the percentage composition is presented in Table 10.

Table 10. Percentage of silver in the final material and in the reference samples

Content % Silver content Sample mg Ag / g in paper paper PAg + 2.69 0.3 PZAg + 14.9 1.5 PZAg + EDTA 10.9 1.1 BEFORE_EDTA 31.1 3.1 5.9 0.6

In the final material subjected to sonication and then rinsing with EDTA, based on the developed procedure, the silver content is below 1% by weight. % and is 0.6 wt.%.

Example 3. Properties of the obtained paper material

Durability of the obtained paper material

The acidity of the paper

One of the parameters determining the durability of the paper is its acidity determined by pH measurements. The pH measurements of the paper samples were made with a flat electrode (Flatrode Hamilton, 809 Titrando - Metrohm). Samples and a drop of water were cut from the prepared paper sheets. Then the flat electrode was placed on the sample and the pH was measured until stabilization was achieved (not less than 120 s). The measured pH values are shown in Figure 5.

Another parameter determining the durability of the paper may be its grade after aging tests. The conditioning of the samples was performed according to ASTM D685 at 23 ° C and RH = 50%. The procedure described in ASTM D6819-02 (2007) was used for the aging tests. Aging was carried out in a climate chamber at 90 ° C and 59% relative humidity. The samples were aged for 12 days. Both pure cellulose and zeolite papers have been aged.

The degree of cellulose polymerization

The degree of weight average polymerization (DPw) of cellulose in the form of cellulose triphenyl carbamate (CTC) was determined. Molecular weight distribution analysis was performed in tetrahydrofuran, with dual detection: multi-angle light scattering (MALLS, Waters) and refractometric (R1) detection. Both detectors operated at a wavelength of 658 nm. The measurements used the value of a specific refractive index increment equal to 0.162 cm ³ / g, determined experimentally on the chromatographic set, on which subsequent measurements of the molecular weight distributions of the material were performed.

The cellulose material with the zeolite was subjected to the standard sample preparation procedure, the zeolite was separated from the CTC solution by filtering the solution through a 0.45 µm teflon syringe filter. The filtrate solution was subjected to further SEC analysis.

Paper with silver ions / nanoparticles as well as silver ions / nanoparticles and zeolite before derivatization was rinsed to remove silver ions / nanoparticles to avoid contamination of the column

PL 229 348 Β1 chromatography. Paper samples containing Ago, Ag ⁺ and zeolite were defibrated in a beaker with 50 cm ^{3 of} water (the process was assisted by an ultrasonic bath).

Table 11. DPw weight degrees of polymerization of model paper samples (SD - standard deviation), aging -12 days.

Mark Type of material DPw SD P. Unaged cellulose 1228 8 PS 12 Aged cellulose for 12 days 918 95 PZO Cellulose with zeolite - unaged 1238 82 PZO S12 Y-zeolite cellulose - aged 1285 44 PAg + Cellulose with silver ions - unaged 1288 7 PAg- Si 2 Cellulose with silver ions - aged 1 15 3 PZAg + AgY zeolite cellulose - unaged 1077 38 PZAg + S12 AgY zeolite cellulose - aged 423 14 PAgO Ag ⁰ cellulose sonicated 10 min - unaged 1357 61 PAgO_SI2 Ag ° cellulose sonicated 10 min - aged 190 5 PZAg + EDTA AgY cellulose, washed with EDTA - unaged 1362 AND PZAg + _EDTA_Sl AgY cellulose. washed EDTA - aged 591 13

2 BEYOND AgY and Ag ° cellulose sonicated 10 min - unaged 1341 17 ABOVE $ 12 Cellulose z. AgY and Ag ° sonicated 10 min - aged 287 6 PASSED AgY and Ag ⁰ cellulose sonicated 10 min. washed EÓTA - unaged 1259 28 BEYOND EDTA SI '2 AgY and Ag cellulose sonicated 10 min. washed EDTA · aged 514 37

The weight-average degree of polymerization was calculated on the basis of the molecular weight distributions of the tested samples obtained by the SEC method with the use of a multi-angle light scattering detector (MALLS).

Comparing the samples before aging with DPw, it can be concluded that despite a certain decrease in the degree of polymerization by the addition of a filler containing silver ions, the PZAg ⁺ EDTA sample shows the smallest decrease in polymerization compared to the unaged sample, much smaller than the PZAgO sonicated sample. In addition, even a slight increase in DPw was observed for the unaged PZAg ⁺ _EDTA sample as compared to the original paper sample.

In order to improve the structural parameters of the paper, the final material development procedure was enriched with an additional step of rinsing the zeolite-filled and sonicated (PZAgO) paper with EDTA salt solution, as described in the previous chapters. The resulting paper material (sample PZAgO_EDTA) had structural properties similar to the material PZAg = _EDTA.

PL 229 348 Β1

There is a correlation between DPw and pH results. Only in the case of zeolite-filled paper the sheet showed a more alkaline reaction (PZO) than the reference sample (P). It can therefore be concluded that the increase in the degree of polymerization of the paper samples filled with zeolite, sonicated and then washed with EDTA, is associated with a decrease in the acidity of the paper.

Mechanical properties

As shown in Figure 8, the addition of zeolite to the paper increases its tensile strength - the breaking strength at zero clipping is greater for the paper sample with sonicated and EDTA washed zeolite than for the reference paper. It can also be seen that washing the silver-exchanged zeolite-filled paper with EDTA solution both before and after sonication substantially improves the mechanical strength of the paper. However, on the basis of the obtained results, it cannot be clearly concluded that the addition of active material to the paper has an influence on the material strength (in terms of tearing). The large measurement error visible in the chart above results from the measurement method itself, and not from the measurement method.

Sorption and catalytic properties

Part of the sorption studies with the use of carbon monoxide (II) was presented in the previous chapter. In order to determine the sorption and catalytic abilities of the research materials, acetaldehyde was used as a representative of volatile organic compounds, and at the same time a possible degradation product of various products (food, paper) and due to its undesirable impact on human health. For comparison, samples of sonicated ZAgO_EDTA zeolite (sonicated sample for 10 min) and non-sonicated ZAg'_E DTA zeolite were used.

The tests were carried out in the insitu flow system in the reaction chamber (Harrick) inserted into the DRIFT pan of the infrared spectrometer (Thermo Nicolet 6700). Before the tests, the zeolite samples placed in the reactor were annealed at 110 ° C in He flow in order to desorb part of the water present in the zeolite. Sorption of aldehyde dosed from the saturator was carried out in the reactor in the flow He 20 cm ³ / min for 30 min at the temperature of 25 ° C. After sorption, and before switching on the thermal program, the sample was washed with He at 25 ° C. The analyzes of the transformations of formaldehyde adsorbed on the zeolite surface were carried out at different temperatures in the He flow.

The results presented in Figure 9 A. show that the modified ZAg0_EDTA zeolite shows sorption capacity. Acetaldehyde adsorbed on the samples already at room temperature, as evidenced by the bands appearing after sorption: apart from the bands from methyl vibrations in the range of 3000-2800 cm ¹ , also vibrations from the aldehyde group at 1760 and 1728 cm ' ¹ (not present in the sample reference). According to the correlation tables, the appearing bands correspond to the vibrations of the following groups:

2987 cm ¹ -Vas CH;

• 2920 cm · ¹ -v _s CH ;, • 2870 Cm ¹ - 2Vs fermi CH3, • 2752 cm ' ¹ - 25s OH (from adsorbed CH3OH), or overtone originating from extraplanar vibrations of the CH group • 1728, 1680 cm · ¹ - vC = O • 1411 cm · ¹ - 5as CH ₃ • 1350 cm ¹ - δε CH ₃ (δ CH)

Additionally, in the range of vibrations from the carbonyl groups of the aldehyde there is a band of 1642 cm ^-1 from the bending vibrations of H2O molecules bound in the zeolite. The 1680 cm ^-1 band is characteristic of stretching vibrations from carboxyl groups. These bands may shift depending on the local potential around the adsorbed molecule.

The comparison of the spectra for the presented material ZAg0_EDTA and the reference material ZAg ⁺ _EDTA shows differences in the sorption capacity and catalytic activity of the materials (Figs. 9 A and B). Analyzing the evolution of the spectra with the temperature increase (Fig. 9 a), a gradual decrease in the band intensity from the vibrations of the aldehyde group at 1728 cm ^-1 with the temperature increase for both samples (Fig. 9 C and D) can be noticed. With increasing temperature, not only acetaldehyde is desorbed from the surface of the sample (physically absorbed part at low temperature), but also oxidized initially to acetic acid, the presence of which indicates the band at 1720 and 1680 cm ¹ . The carboxyl group band appears at room temperature for the sonicated ZAg0_EDTA sample and increases with the temperature increase to 100 ° C followed by a decrease in intensity and acetic acid desorption. Note that the acetic acid bands for the unssonicated ZAg'_EDTA sample do not appear at room temperature, and develop only at 100 ° C, which is a significant difference in

PL 229 348 Β1 oxidizing both materials. In line with this observation, the conversion of acetaldehyde is also less dynamic for this sample. Moreover, taking into account the fact that the material without oxygen access (rinsing with an inert gas) exhibits an oxidizing effect, it indicates that the reaction mechanism is of the Mars-van Krevelen type, where network oxygen is consumed to oxidize the adsorbate. In the given temperature range, no significant changes in the intensity of the band originating from carbon dioxide were found, which proves incomplete oxidation of the aldehyde. In addition, the spectra at temperatures above 200 ° C are the same as before acetaldehyde sorption, with the difference that the band at 1642 cm ¹ disappeared due to the loss of water from the zeolite.

In an analogous experiment carried out in air, acetic acid is formed in zeolite as a carrier gas instead of helium in the thermal program in large amounts already at room temperature, which is a major difference compared to the unssonicated reference sample, which begins to oxidize acetaldehyde in a significant way only at 100 ° C (some traces are also observed at room temperature) (compare spectra A and B in Fig. 10). Carbon dioxide is formed for both samples at about 250 ° C.

The quantification of the observed changes is presented in Fig. 11 A and B, where X is the degree of acetaldehyde conversion determined from the band intensity at 1728 cm ^-1 (calculated similarly to the conversion, with the maximum value - the initial intensity being used as the reference point), and Y as the acetic acid conversion calculated from the band intensity at 1680 cm ^-1 (related to the maximum value). Due to the fact that acetic aldehyde in the air was oxidized already at room temperature for the sonicated sample, the intensity value after sorption at 25 ° C in the absence of air was adopted as the maximum value of the intensity. The degree of acetaldehyde conversion presented in this way covers both its conversion and desorption from the zeolite surface. The quantitative comparison of the sonicated ZAgO_EDTA zeolite sample and the non-sonicated zeolite indicates that the sonicated form is much more active at much lower temperatures. The formation of acetic acid in the air was already observed at room temperature in the amount of 80% in relation to the maximum value. Note also that the acetic acid yield maxima are repeated at the same temperatures for a given sample regardless of the experimental conditions.

Acetaldehyde is also adsorbed in samples of the final paper material (PZAgO_EDTA) shown in Figure 11. The acetaldehyde was bound in the material at 25 ° C. Such a conclusion can be drawn on the basis of the characteristic bands (2920, 1728, 1640 cm ¹ ) derived from acetaldehyde. In this case, the analysis of the catalytic capacity of the material is difficult due to the obscuring of the acealdehyde and zeolite bands by the cellulose bands. However, there is no reason to argue that they are different.

Determination of microbial activity

The tests were performed by slicing the following test organisms:

Bacteria:

1. t. Escherichia coli

2. Serratia marcescens

3. BacillussubiHis

4. Bacillus megatherium Mushrooms:

5. Trichoderma viride

6. Chaetomium globosum

7. Aspergillus niger

8. Ciadosporium cladosporioides

9. Mortierella alpinum

The above-mentioned strains are stored on media in the laboratory of the Plant-Microorganism Interaction Team, Institute of Environmental Sciences and the Małopolska Center of Biotechnology, Jagiellonian University (Kraków) and are used for comparative studies after inoculating them with appropriate media. Some of these strains come from paper isolation and some were obtained during other types of research.

Comparison of various zeolite materials

The first step in the quantitative analysis of microbial activity was to test a series of zeolites that could potentially be used in positron packaging. Y-type zeolites (fotosite), ZSM-5 (pentozil) and MCM-56 molecular sieves (mesoporous material) were used for the research. These materials were exchanged with silver cations similar to that described for zeolite Y in the previous sections.

PL 229 348 Β1

All tested materials showed antibacterial activity (Fig. 10). Note that without zeolite material (control) the bacteria multiplied at 9,000 counts. MCM-56 molecular sieves are the worst in the zeolite ranking. The microbiological activities of zeolites Y and ZSM-5 are similar regardless of the state of silver in the sample (samples with Ag 'and sonicated with Ag °). Of all the materials, however, the best Y-type zeolite (preparation consistent with the preparation described in this paper), which had almost 100% antibacterial activity in the case of Escherichia coli, turned out to be the best.

Y zeolite paper material tests

The next step in determining the activity was to carry out tests on ready-made paper sheets. Samples of materials prepared at the Faculty of Chemistry of the Jagiellonian University were used for the test. These samples were sterilized on Whatman paper in Petri dishes before being used in the experiment.

Bacteria (strains 1-4) were spread on the agar surface (NA) and spread with a disposable stick (a single stick was used for a given strain). For each of the strains and each type of paper test, 3-5 replications were used (some of the replicates were rejected due to uneven application of the material, which is visible after a few days from the time of the test; min. N = 3). A single disc of paper was placed on each Petri dish containing the bacteria. The cultures were placed at 32 ° C for three days. then the temperature was lowered to 25 ° C for a further few days. The growth of microorganisms was observed daily. The formation of a no-growth zone around the disc material was not found in any of the tested cases, which proves that the silver did not propagate from the tested material.

The rest of the experiment was transferred to a laminar chamber (sterile conditions). A significant reduction in bacterial growth was found under the discs with the addition of silver (in any form). Each Petri dish was opened and a disc of paper was placed on the back of the upper dish using sterile tweezers, turning it upside down and thus exposing the part that adhered to the agar. To assess the number of bacteria, the LuciPac Pen test (ATP + AMP Hygiene Monitoring test kit by Kikkoman Corp. coda 60331) was used, following the recommendations with minor innovations. The swab was positioned perpendicular to the disc in the central part and, resting the tip in the "screwdriver" position, was turned 360 °. The result defining the relative ATP + AMP content was then read on a lumitester reader.

Mushrooms (strains 5-9) were introduced into Petri dishes containing PDA medium and three filters of each type were placed centrally. In each case, three repetitions were assumed. The strains were introduced in the form of an agar disc with mycelium at a distance of 2 cm from the center disc. Due to the different growth rates of the mycelium, it was necessary to conduct the test for a longer period (approximately 2 weeks). Each of the tested strains showed slightly different problems during the observation.

Trichoderma viride - the strain formed colonies with spores in the circular area of the colony outside; in some cases the puck falls out! in the wrong place, which made observations difficult. In a few cases, delay in maturation of conidia was observed, which was manifested by their lighter color - light green or yellow (apart from this area of conidia with a blue goat color).

Chaetomium globosum - fruiting body formation was generally delayed on the surface of the paper samples used, where the mycelial activity was probably concentrated on the decomposition of the paper, while fruiting is a sign of a lack of nutrients.

Aspergillus niger - well suited for quick tests, although as the test passed, spores released from the surrounding conidiophores appeared on the surface of the silver discs, which made the analysis somewhat difficult, but such conidia did not germinate in such places, although they probably remained viable.

Cladosporium cladosporioides - species characterized by relatively slow growth; it was necessary to reapply the inoculum to the dishes to speed up the moment when the mycelia would reach the disks; the advantage of this species is the production of black mycelium visible within the paper discs in cases where paper colonization has taken place.

Mortierella alpina - light mycelium with conidia devoid of dark pigments.

The results presented in Figures 11 and 12 show that the paper filled with zeolite substituted with silver cations and then sonicated and washed with EDTA (PZAgO_EDTA), compared to the reference sample in the non-sonicated form (PZAg ⁺ _EDTA), shows better biocidal properties towards bacteria and is slightly better than the reference sample for antifungal activity. especially for Chaetomium and Cladosporium fungi. Summary of the developed material.

PL 229 348 Β1

Taking into account such parameters as: silver content in paper preparations, paper durability, sorption and catalytic properties, the PZAgO_EDTA paper material with sonicated Y-type zeolite exchanged with silver significantly enriches the expected packaging assumptions. Based on the optimization of the silver content, a material containing less than 1 wt. silver. This is the lowest value for which biocidal activity was observed in relation to all tested organisms. The proposed material is hybrid in nature, in which the active agent is in a form containing both silver cations and reduced silver bound in a zeolite matrix. Noteworthy are the sorption properties of the material confirmed for carbon monoxide and acetaldehyde. Another advantage of the material is its ability to catalyze oxidation reactions at room temperature in the absence of air, as demonstrated by the oxidation of acetaldehyde. High biocidal activity has been confirmed in tests with selected strains of microorganisms, typically found in food and archives. Relatively lower microbicidal activity was found in the case of Bacillus megaterium bacteria and fungi of the Aspergillus genus.

Claims (15)

Patent claims 1.Nanocomposite material comprising cellulose filled with silver-containing zeolite, characterized in that the mineral filler is a Y-type zeolite, and the silver is in a form bound to a zeolite matrix, simultaneously in the form of silver cations and metallic silver nanoparticles, preferably in a 1: 1 ratio, with whereby the total silver content of the material does not exceed 1% by weight. 2. The material according to claim The process of claim 1, wherein the silver ions are introduced into the zeolite structure by ion exchange. 3. The material according to p. The process of claim 1, wherein the reduced silver is present in addition to the silver cations in the zeolite as a result of the sonication procedure. 4. The material according to p. The method of claim 1, characterized in that it exhibits sorption properties towards volatile organic compounds and gaseous pollutants. 5. The material according to p. The method of claim 1, characterized in that it exhibits catalytic properties in the oxidation of volatile organic compounds at room temperature in air and at a temperature from 60 ° C in the absence of air. Material according to claim 1, 2, 3, 4 or 5, characterized by bactericidal and fungicidal properties, in particular against Escherichia coli, Serratia marcescens, Bacillus suhtilis and Bacillus megatherium. 7. The material according to p. The fungus according to claim 6, characterized in that it exhibits fungicidal properties against the fungi Trichoderma viride, Chaetomium glohosum, Aspergillus Niger, Cladosporium ciadosporides, and Morterella alpinum. 8. A method of obtaining nanocomposite packaging material, including substituting a zeolite matrix with silver (I) ions, adding an active material in the form of a zeolite matrix containing silver to the cellulosic suspension and depositing it on cellulose fibers, shaping the furnish to the desired shape and drying, characterized in that before the addition of the silver ion-substituted zeolite matrix to the cellulose suspension, the zeolite matrix is sonicated, preferably for 10 minutes in the zeolite suspension at an average power of 90 W and at a solution temperature below 60 ° C, followed by washing of the zeolite with an aqueous solution of disodium ethylenediaminetetraacetic acid (EDTA) wherein preferably washing with EDTA comprises the following steps: a) washing the zeolite with 0.01 M EDTA at room temperature; b) rinsing for 1 hour at the boiling point of 0.01 M EDTA; c) washing the zeolite with 0.1 M EDTA solution and d) rinsing the zeolite with deionized water. 9. The method according to p. The process of claim 8, wherein the zeolite matrix is treated with a solution of silver nitrate. 10. Use of a nanocomposite material as defined in claims 1 to 7 for packaging. 11. The use according to claim 1 10 for packaging plants, works of art, archives and antiques. PL 229 348 Β1 12. Use according to p. 10 for food, pharmaceutical and pet food packaging. 13. The use of a nanocomposite material produced by a method as defined in claim 8-9 for wrapping. 14. Use according to claim 1 13 for packaging plants, works of art, archives and antiques. 15. Use according to Claim 13 for food, pharmaceutical and pet food packaging.