Modified halloysite nanotubes for deodorization

Abstract

The present application relates to modified halloysite nanotubes configured for chemisorption of volatile organic compounds with high efficiency and / or have high formaldehyde retention capacity by comprising one or more functional groups selected from amines (in other words, amino-), hydrazides, and acylhydrazides, as well as to the production methods and use thereof.

Description

[0001] SPECIFICATION

[0002] MODIFIED HALLOYSITE NANOTUBES FOR DEODORIZATION

[0003] Technical Field

[0004] The present application relates to materials for odor removal. The present application particularly relates to modified nanotubes to provide chemisorption of volatile organic compounds.

[0005] Background

[0006] Prior art technologies directed to the removal or reduction of unpleasant odors are highly diverse. Among the most widely used techniques are methods based on absorption and adsorption. Activated carbon, known for having a large surface area per unit weight, is widely used in air purifiers and filtration systems due to its adsorption of odor-causing molecules. Similarly, zeolites, which are microporous minerals, find use in both industrial and domestic applications since they trap odor-causing molecules within their structure. US10960096B2 discloses gas-permeable devices that absorb volatile organic compounds (abbreviated as VOCs) and malodorous compounds.

[0007] Chemical neutralization can be mentioned as another approach. Odor neutralizers chemically react with odor-causing molecules, thereby neutralizing the same. Ozone, which is frequently used in air purification systems, and essential oils having odorneutralizing properties can be considered in this category. Bioenzymatic cleaners, which are effective in decomposing organic materials that cause bad odors, also fall within this category; and they are commonly used in cleaning products designed for the removal of animal odors, waste, and spilled food products.

[0008] Masking agents are products that provide a temporary solution by covering unpleasant odors with relatively pleasant scents. Perfumes and air freshener mixtures, as well as essential oils that provide not only a masking effect but also mild antimicrobial properties, fall within this category. In oxidation methods, ozone generators are employed in decomposition of odor-causing compounds with ozone, or hydroxyl generators that produce hydroxyl radicals are used to react with odor-causing compounds and neutralize the same. These technologies are generally used in air purification and sanitation applications.

[0009] In microbial techniques, the natural abilities of beneficial bacteria and other microorganisms are utilized. The use of probiotics, which compete with and prevail over odor-causing bacteria, falls within this category. Another example in this category, biological filters or biofilters, use microbial cultures in the treatment of malodorous gases in industrial plants.

[0010] Photocatalytic oxidation is an advanced method in which catalysts such as titanium dioxide are used together with ultraviolet (abbreviated as UV) light, thereby oxidizing and decomposing volatile organic compounds and odor-causing molecules. This technology is generally used in modern air purification systems.

[0011] Finally, physical barriers such as odor barriers and sealing elements are used to prevent the spread of unpleasant odors. These are particularly used in waste management and sanitation, where confining malodorous materials and keeping them under control is of critical importance.

[0012] Despite the existence of the wide variety of technologies listed above, there is always benefit in proposing new technologies that provide high odor removal performance at low cost.

[0013] Brief Description

[0014] The main objective of the present application is to overcome the deficiencies of the prior art mentioned above. Another objective of the present application is to provide an odor remover that is low-cost and has a high adsorption capacity. These objectives are achieved by means of the features constituting the independent claims of the present application. In this regard, the present application provides modified halloysite nanotubes comprising one or more functional groups selected from amino, hydrazides, and acylhydrazides for chemisorption of volatile organic compounds, and a method enabling the production of the same. The present application further proposes the use of the modified halloysite nanotubes conforming to this description in odor removal. Odor removal is achieved through chemisorption of volatile organic compounds and / or retention of formaldehyde by the modified halloysite nanotubes.

[0015] Brief Description of the Drawings

[0016] FIG. la schematizes a reaction in which an aldehyde is chemisorbed by an amino group on an exemplary modified halloysite nanotube within the scope of the present application.

[0017] FIG. lb schematizes a reaction in which an aldehyde is chemisorbed by a hydrazide group on an exemplary modified halloysite nanotube within the scope of the present application.

[0018] FIG.lc schematizes a reaction in which an aldehyde is chemisorbed by an acylhydrazide group on an exemplary modified halloysite nanotube within the scope of the present application.

[0019] FIG.2 shows a first chemical reaction taking place in an exemplary implementation of the method subject to the present application.

[0020] FIG.3 shows a second chemical reaction taking place in an exemplary implementation of the method subject to the present application.

[0021] FIG.4 shows a third chemical reaction taking place in an exemplary implementation of the method subject to the present application.

[0022] Detailed Description Halloysite nanotubes or halloysite nanoclay (abbreviated as HNT) have a unique surface characteristic and therefore it has been concluded that they have high potential in the reduction of odor emissions, particularly when suitably modified. According to the technology proposed in the present application, halloysite nanotubes are modified with various specifically selected functional groups. Thus, modified halloysite nanotubes (abbreviated as mHNTs) are provided with high chemisorption capability, as well as in which adsorption capacities -which were already higher than those of zeolites- are significantly improved.

[0023] The modified halloysite nanotubes subject to the present application have several advantages compared to zeolites, which are commonly used in odor removal; since they can be synthesized more easily, have high biocompatibility, are relatively low-cost, have a relatively low environmental impact potential, and provide a relatively high adsorption capacity.

[0024] In light of the above information, the modified halloysite nanotubes proposed in the present application comprise one or more functional groups selected from amino, hydrazides, and acylhydrazides. Thanks to these functional groups, volatile organic compounds can be chemisorbed and formaldehyde can be retained by the modified halloysite nanotubes, thereby providing odor removal.

[0025] FIG. la schematizes a reaction in which an aldehyde is chemisorbed by an amino group on a modified halloysite nanotube obtained as a result of an exemplary modification of a halloysite nanotube according to the present application. At the end of the reaction, an imine group is formed. Here, the part of the modified halloysite nanotube other than the amino group participating in the reaction is represented by R.

[0026] FIG. lb schematizes a reaction in which an aldehyde is chemisorbed by a hydrazide group on a modified halloysite nanotube obtained as a result of an exemplary modification of a halloysite nanotube according to the present application. At the end of the reaction, a hydrazone group is formed. Here, the part of the modified halloysite nanotube other than the hydrazide group participating in the reaction is represented by R. FIG ,1c schematizes a reaction in which an aldehyde is chemisorbed by an acylhydrazide group on a modified halloysite nanotube obtained as a result of an exemplary modification of a halloysite nanotube according to the present application. At the end of the reaction, an acylhydrazone group is formed. Here, the part of the modified halloysite nanotube other than the acylhydrazide group participating in the reaction is represented by R.

[0027] The present application further provides a method for the production of modified halloysite nanotubes conforming to the above description. In other words, the present application proposes a method for producing the one or more modified halloysite nanotubes comprising one or more functional groups selected from amines (in other words, amino-), hydrazides, and acylhydrazides for chemisorption of volatile organic compounds. The method of the present application comprises the following steps:

[0028] (a) obtaining a first reaction product (Pl) by carrying out a first chemical reaction (Rxnl) between monochloroacetic acid or one or more alkali metal salts thereof and one or more first compounds (Cl) selected from one or more N-(3- (trialkoxysilyl)alkyl)alkylenediamines, one or more ((trialkoxysilyl)alkyl)anilines, and one or more (3-anilinoalkyl)trialkoxysila nes;

[0029] (b) obtaining a second reaction product (P2) by carrying out a second chemical reaction (Rxn2) between the first reaction product (Pl) and hydrazine or hydrazine hydrate;

[0030] (c) obtaining one or more modified halloysite nanotubes (mHNT) by carrying out a third chemical reaction (Rxn3) between the second reaction product (P2) and one or more halloysite nanotubes.

[0031] An exemplary first chemical reaction (Rxnl) mentioned in step (a) of the method is shown in FIG.2. With the reaction in FIG.2, an exemplary first reaction product (Pl) is obtained. Additionally, hydrochloric acid may be expected to form in the first reaction (Rxnl). Starting from the exemplary first reaction product (Pl) obtained in the reaction shown in FIG.2, an exemplary second chemical reaction (Rxn2) that can be carried out is shown in FIG.3. With the reaction shown in FIG.3, an exemplary second reaction product (P2) is obtained.

[0032] An exemplary third chemical reaction (Rxn3) that can be carried out starting from the exemplary second reaction product (P2) obtained in the reaction shown in FIG.3, is shown in FIG.4. An example of the modified halloysite nanotubes (mHNT) according to the present application is obtained with the reaction shown in FIG.4. As can be seen, the halloysite nanotubes (HNT) comprise silanol groups on their surfaces, and the third chemical reaction (Rxn3) takes place between the second reaction product (P2) and these silanol groups. Since the silanol groups are located on the surface of the halloysite nanotubes (HNT), it is not inappropriate to state that the third chemical reaction (Rxn3) takes place between the halloysite nanotubes (HNT) and the second reaction product (P2).

[0033] In an exemplary implementation of the method according to the present application, N- (3-(trimethoxysilyl)propyl)ethylenediamine can be selected and used as the N-(3- (trialkoxysilyl)alkyl)alkylenediamine.

[0034] In an exemplary implementation of the method according to the present application, ((trimethoxysilyl)propyl)aniline can be selected and used as the ((trialkoxysilyl)alkyl)aniline.

[0035] In an exemplary implementation of the method according to the present application, (3- anilinopropyl)trimethoxysilane can be selected and used as the (3- anilinoalkyl)trialkoxysilane.

[0036] In an exemplary implementation of the method according to the present application, sodium monochloroacetate may be selected and used as the alkali metal salt of monochloroacetic acid. A skilled chemist reading the method described in the present specification and exemplified with the Figures can accomplish the production of modified halloysite nanotubes (mHNT) comprising one or more functional groups selected from amino, hydrazides, and acylhydrazides, without any undue burden. By implementing any version of the method described herein, modified halloysite nanotubes (mHNT) that function with high performance in the chemisorption of volatile organic compounds and / or the retention of formaldehyde can be obtained without difficulty.

[0037] In parallel with the above explanations, the present application proposes the use of one or more modified halloysite nanotubes comprising one or more functional groups selected from amino, hydrazides, and acylhydrazides in odor removal. The odor removal can take place, for example, through chemisorption of one or more volatile organic compounds on a surface of the modified halloysite nanotubes by the one or more functional groups. Alternatively or additionally, the odor removal may take place, for example, through retention of formaldehyde on a surface of the modified halloysite nanotubes by the one or more functional groups. In particular, amino groups are effective in efficiently adsorbing volatile organic compounds and are an effective formaldehyde scavenger.

[0038] The thermal stability of many plastic materials at high temperatures is weak; therefore, when plastic materials are subjected to thermal processing or recycling, volatile organic compounds that are malodorous and harmful to the environment are released. In this regard, an exemplary use according to the present application may be carried out during the thermal processing of one or more plastic materials. Similarly, another exemplary use according to the present application may be carried out during the recycling of one or more plastic materials.

[0039] Thanks to the relatively easy and abundant availability of halloysite nanotubes, the present application enables an odor-removing material that is lower-cost compared to, for example, zeolites. Furthermore, thanks to the relatively high adsorption capacity of halloysite nanotubes, the present application enables an odor remover with higher capacity compared to, for example, zeolites. The method proposed in the present application makes it possible to provide halloysite nanotubes with a high amount of amino groups, thereby providing a very high odor removal capacity.

[0040] Reference signs

[0041] Cl first compound

[0042] HNT halloysite nanotube mHNT modified halloysite nanotube

[0043] Pl first reaction product

[0044] P2 second reaction product

[0045] P3 third reaction product

[0046] Rxnl first chemical reaction Rxn2 second chemical reaction

[0047] Rxn3 third chemical reaction

Claims

Claims1. One or more modified halloysite nanotubes comprising one or more functional groups selected from amino, hydrazides, and acylhydrazides.

2. A method for producing one or more modified halloysite nanotubes comprising one or more functional groups selected from amino, hydrazides, and acylhydrazides; the method comprising the following steps:(a) obtaining a first reaction product (Pl) by carrying out a first chemical reaction (Rxnl) between monochloroacetic acid or one or more alkali metal salts thereof and one or more first compounds (Cl) selected from one or more N-(3-(trialkoxysilyl)alkyl)alkylenedia mines, one or more((tria Ikoxysi lyl)al kyl)a ni li nes, and one or more (3-a ni li noa lkyl)tria Ikoxysila nes;(b) obtaining a second reaction product (P2) by carrying out a second chemical reaction (Rxn2) between the first reaction product (Pl) and hydrazine or hydrazine hydrate;(c) obtaining the one or more modified halloysite nanotubes (mHNT) by carrying out a third chemical reaction (Rxn3) between the second reaction product (P2) and one or more halloysite nanotubes.

3. The method according to claim 2, wherein N-(3- (trimethoxysilyl)propyl)ethylenediamine is used as the N-(3- (trialkoxysilyl)alkyl)alkylenediamine.

4. The method according to any one of claims 2 or 3, wherein ((trimethoxysilyl)propyl)aniline is used as the ((trialkoxysilyl)alkyl)aniline.

5. The method according to any one of claims 2 to 4, wherein (3- anilinopropyl)trimethoxysilane is used as the (3-a ni li noa lkyl)tria Ikoxysi la ne.

6. The method according to any one of claims 2 to 5, wherein sodium monochloroacetate is used as the alkali metal salt of monochloroacetic acid.

7. Use of one or more modified halloysite nanotubes comprising one or more functional groups selected from amino, hydrazides, and acylhydrazides in odor removal.

8. The use according to claim 7, wherein the odor removal comprises chemisorption of one or more volatile organic compounds on a surface of the modified halloysite nanotubes by the one or more functional groups.

9. The use according to any one of claims 7 or 8, wherein the odor removal comprises retention of formaldehyde on a surface of the modified halloysite nanotubes by the one or more functional groups.

10. The use according to any one of claims 7 to 9 during a thermal processing of one or more plastic materials.

11. The use according to any one of claims 7 to 9 during a recycling of one or more plastic materials.

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