HK1223793B - Probiotic and biocide and process and apparatus for manufacture thereof - Google Patents

Description

Probiotics and biocides and production methods and devices thereof

Technical Field

The present invention broadly relates to a method and apparatus for producing a calcined powder from a lightly calcined material for use in preparing a material having biological activity suitable for a broad spectrum of viral, bacterial, and fungal activity, and as a probiotic or biocide, depending on the target.

Background Art

Nanomaterials with biocidal and probiotic properties are being widely developed, particularly nanomagnesium oxide (MgO) and nanozinc oxide (ZnO). An example of a biocide is "Antibacterial Properties of Magnesium Oxide Powder," by J. Sawei et al., World Microbiology and Biotechnology, 16, no. 2, pp. 187-194, 2000. Another example is "Antibacterial Activity of Magnesium Oxide Nanoparticle Powder Against Foodborne Pathogens," J. Nanopart. Res, 13, 6877-6885.

Sawai et al.'s research aimed to produce MgO with a high surface area and a particle size of less than 50 nm. In experiments with these materials, the MgO particles reacted rapidly with water to form nanomagnesium hydroxide. The prior art references to nanomagnesium oxide are often attributed to nanomagnesium hydroxide. These hydrous nanomaterials exhibit broad biological activity, including antiviral, antibacterial, and antifungal properties. These powders and hydrous nanopowders can neutralize toxic substances, such as chemical warfare agents.

In a paper published by T. Yin and Y. Lu, researchers demonstrated potent bactericidal activity of nanoparticles of magnesium oxide against the foodborne pathogens Escherichia coli and Salmonella. This work is significant because nanomagnesium oxide (MgO) or nanomagnesium hydroxide (MgOH) is not considered toxic to humans or animals and has a positive impact on plants through the supply of magnesium as a fertilizer. For example, seven studies observed a reduction in E. coli at a solid dose rate of 8 g/L, growth inhibition at a dose of 1 g/L, and complete cell death within 24 hours at a dose of 13 g/L. Although Mg(OH) _₂ is relatively insoluble, it dissolves rapidly in low pH environments, particularly those found in the digestive system. This is because the greater the surface area of nano-MgO/Mg(OH) _₂ , the faster its dissolution rate.

U.S. Patent No. 6,827,766 B2 protects a decontamination product comprising nanoparticles including magnesium oxide and Mg(OH) ₂ , an optional biocide, and a liquid carrier including water. The antibacterial properties are significantly enhanced by the presence of the nanoparticles. The decontamination process includes a liquid spray, mist, aerosol patch, gel, wipe, vapor, or foam. Although the claims are limited to adding existing biocides to the product as adjuvants, the disclosed embodiments teach that the nanoparticles have an effective, long-term antibacterial activity in a liquid carrier without the need for an adjuvant. Specifically, Example 3 thereof shows that a 5/1 water/oil emulsion, 2% nano magnesium oxide, calcium oxide, and ZnO solids have such properties, particularly without the requirement for a biocide.

The effect of particle size appears to be significant. U.S. Patent No. 2,576,731A (Thomson) discloses the use of a magnesium hydroxide slurry made from standard magnesium oxide as a base for foliar sprays as a carrier for insect- and fungicide-active biocides. The benefits are related to the ability of the alkaline particles to absorb the active biocide, rendering it insoluble, and the strong adhesion of the biocide particles to plant leaves, allowing the biocide to remain effective even after multiple washings of the leaves. This patent describes the effects of magnesium hydroxide, which has no insecticidal or fungicidal activity. In the context of the present invention, the important teaching of the patent is the adhesion of magnesium hydroxide.

This view is supported by a paper published by Motoike et al. entitled "Antiviral Activity of Heated Dolomite Flour" (Biocontrol Sci. 13(4):131-82008), in which treated dolomite was shown to have antiviral activity. U.S. Patent No. US 20090041818 A1 claims protection for an antiviral agent that is a mixture of an oxide and a hydroxide, wherein hydroxide ions are produced by the reaction of the oxide and the hydroxide. It is stated that a number of materials can provide the hydroxide, one of which is Mg(OH) ₂ , and the oxide is preferably MgO. The disclosure in the prior art is that the biocidal activity of such conventional slurries is primarily short-lived, and thus the produced magnesium hydroxide, or hydrated calcined dolomite slurry, does not have a significant long-term biocide effect. Without being limited by theory, this study suggests that the active chemical species in such hydroxide slurries are naturally present, but their concentration is too low to have a lasting effect on microorganisms. The present invention seeks to overcome this limitation.

A deep understanding of how nano-Mg(OH) ₂ exhibits remarkable bioactivity compared to standard materials is demonstrated at two levels.

First, at the biological level, the most plausible theory for why pathological fungal growth is chemically inhibited is the presence of reactive oxygen species (ROS). Reactive oxygen species have high redox potentials and include superoxide ions ( _O₂₂- ⁾ , which are known to hydrolyze water to generate hydroxyl radicals (OH), perhydroxyl anions ( _HO₂- ⁾ , and hydrogen peroxide ( _{H₂O₂ )} . The equilibrium of these species in water is primarily regulated by pH, and at pH values close to those of nano-Mg(OH) _₂ particles, i.e., around pH 10.4, perhydroxyl anions dominate. Plants can ramp up production of ROS as a defense against attack by pathogenic microorganisms, and ROS attack the primary cell walls of pathogenic fungi and bacteria. In response, fungi produce chemicals that react with and neutralize the ROS, and the ROS attack and destroy the cell walls of pathogenic microorganisms. The same model used for activity detection is applicable to pathogenic bacteria, particularly anaerobic Gram-negative bacteria. The ROS symbiosis is closely associated with plant ROS and beneficial Gram-positive bacteria, all of which are crucial for a healthy growth environment. Gram-positive bacteria are generally beneficial and aerobic, and ROS can increase oxygen levels in the environment. Gram-positive bacteria are generally beneficial, aerobic, and ROS can increase oxygen levels in the environment. For example, as described in the case of rice blast fungus: Kun Huang, Kirk J. Czymmek, Jeffrey L. Caplan, James A. Sweigard & Nicole M. Donofrio (2011).

Secondly, at the atomic level, it is evident that the long-term bioactivity of nano-Mg(OH) ₂ slurries is linked to their ability to generate and stabilize ROS. Generally speaking, small crystallites, by definition, form a high proportion of their crystalline surface on high-energy surfaces, and it is well understood that such surfaces are sources of energetic oxidants, such as reactive oxygen species. In the case of Mg(OH) ₂ , techniques such as electron paramagnetic resonance can detect all of the aforementioned free radical species normally present on the crystal surface, albeit at low concentrations. In solution, reactive oxygen radicals can recombine, and the bioactive effects of ROS are degraded by radial recombination. In the presence of Mg(OH) ₂ , the rate of ROS dissipation can be significantly reduced, if not inhibited, by the formation of magnesium peroxide (MgO2 ₎ . Magnesium peroxide is a stable crystalline material typically formed in a mixture with hydrogen peroxide ( _{H2O2 )} , water, and excess MgO. It is stable at ambient temperature (II Vol'nov, and E.I. Latysheva, "Thermal Stability of Magnesium Peroxide" Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 13–18, January, 1970). Therefore, nano-Mg (OH) ₂ can not only form reactive oxygen species at the grain boundaries, but also ROS species can be stabilized on the particle surface. Reactive oxygen species are stored on the surface of the nanoparticles and will be released by changes in the equilibrium associated with pathogen attack, and the general dissolution of the nano-Mg (OH) ₂ supplies magnesium to the plant as a fertilizer.

In summary, a plausible model for bioactive nano-Mg(OH) ₂ is that each particle is a nano-sized crystal with a high concentration of reactive oxygen species (ROS) stably present on its energetic surface, and that its bioactivity is enhanced by enhancing the bioactivity of the plant's natural defense system, which generates ROS to provide an aerobic environment to inhibit pathogenic microorganisms. This effect is enhanced by the pH of Mg(OH) ₂ , which at pH 10.4 neutralizes acids expelled by pathogens; the net positive particle charge from hydrolysis attracts the negatively charged surfaces of specific microorganisms and cells; and the particles adhere to the surfaces of plant microorganisms and cells. In contrast, normal Mg(OH) ₂ particles, ranging in size from 0.1 to 100 microns, typically have a surface dominated by stable 001 faces and exhibit a reduced concentration of ROS.

The same mechanism described above for nano-Mg(OH) ₂ can be applied to other bioactive materials based on metal oxides, such as nano-ZnO and AgO. Their nanoparticles will also support a range of ROS species that depend on specific defects at the corresponding grain boundaries. For example, nano-ZnO is already known to produce hydrogen peroxide and hydroxyl radicals.

The mechanism of biological activity for nanoparticles is fundamentally different from that of other fungicides and bactericides, which use toxic compounds to target pathogenic microorganisms. First, the mechanism of active oxygen production lies in the core differences between aerobic and anaerobic microorganisms, and genetic evolution is unlikely to limit the impact of biological activity. Second, the enhancement of the mechanism is a natural process, whereby plants protect themselves from pathogenic attack. No new chemicals are involved; the decomposition products are essential nutrients or micronutrients, and in the case of magnesium, it is an essential nutrient for chlorophyll production. Plants absorb magnesium through stomata in their leaves, and aerobic/anaerobic competition between fungi, Gram-positive and Gram-negative microorganisms, and plant cells occurs in the soil and on leaves, as described, for example, by Susan S. Hirano and Christen D (Upper, Microbiol. Mol. Biol. Rev. 64, 3624-653 (2000)).

Probiotics have been defined in the United States Patent and Trademark Office, Trademark Trial and Appeal Board, Serial No. 77758863 (2013) as a common name for a fertilizer produced with friendly bacteria in the soil to promote microbial ecology and restore the symbiotic relationship of the soil. In this application, the definition is expanded to include the symbiotic relationship on plant leaves, and this symbiosis is particularly related to the relationship between plants and beneficial Gram-positive bacteria, which is crucial for the healthy environment required for growth. In fact, when Mg (OH) ₂ is applied to leaves as a leaf-shaped line spray, the magnesium absorption effect of the fertilizer is obvious, through increased chlorophyll color and increased leaf thickness. Therefore, from a technical level, the characteristics of nano Mg (OH) ₂ meet its needs as a probiotic soil or plant repair.

The production of chemically synthesized nanomaterials is expensive, both in terms of production and materials. Furthermore, handling very fine powders is difficult, as these particles tend to float in the air. Most importantly, nanomaterials are difficult to filter using traditional air filters. Therefore, the production and processing of these materials requires expensive handling equipment to avoid losses and comply with safety, health, and environmental regulations. These costs have prevented nanomaterials from making a significant impact in the pesticide market. Equally important, concerns remain about nanoparticles' ability to be absorbed through the skin and inhaled into the lungs due to their small size.

There is a need for a product that has the same desirable intrinsic bioactivity of a nanomaterial, using a process that can produce a significant product, yet avoids the material handling issues of the nanomaterial, and its potential for absorption and inhalation.

Any discussion of the prior art throughout the specification should not be considered as an admission that such prior art is widely known or forms part of the common general knowledge in the field.

Summary of the Invention

Problems that need to be solved

The problem to be solved includes the production of materials to make nanoparticles with high concentrations of active species without the undesirable properties resulting from their small size. It may be an object of the present invention to overcome the shortcomings of the prior art.

One possible means of solving the problem is to first produce porous nanoparticle composite powders composed of crystalline nanoparticle materials, wherein the nanoparticles have a grain size at the nanometer level to generate active species responsible for the biological activity.

The powder may be used directly, or may be diluted in water to form a slurry and sprayed to provide protection against microbial activity.

The powder or spray material may be applied to agricultural or aquaculture crops, or products such as seeds, vegetables, meat, fish, or processed food products, or may be a surface to be decontaminated. It can be applied to soil or for phytoremediation.

These particles need to be porous enough to allow for easy diffusion of reactive oxygen species across the particle surface upon contact with microorganisms, and/or for controlled release of the diffused particles when applied to a product to produce a sustained biological effect.

The particle size is preferably such that the powder is impermeable to air and cannot diffuse through the skin. These particles are between 10-100 microns in size and are easily handled and processed by the user.

The binding of the particles is mechanically stable and does not readily degrade to nanoparticles that can be inhaled or absorbed through the skin. The particles do not weakly bind to the polymers of which the individual nanoparticles are aggregated.

The particles must be sufficiently porous to allow reactive oxygen species to form and stabilize on the particle surface and diffuse, potentially affecting microorganisms such as viruses, bacteria, and fungi in powder or hydrated form. Nanocomposites are purposefully not aggregates of nanoparticles, but rather materials in which the constituent particles are strongly interconnected to resist mechanical disintegration. A particle powder with a porosity of approximately 0.5 may be desirable.

Advantageously, the material is an oxide so that the defect species formed have a high oxidizing power as determined by their redox potential, and it is further desirable that the material has a basic pH value so that it gradually degrades in the acidic medium in which the microorganisms grow, so that fresh surfaces are constantly exposed and the biologically active reaction is maintained for a period of time until the particle dissolves.

It may be advantageous that the material from which the nanocomposite material is prepared by the method described herein is a mineral.

This may be advantageous as the surface of the powder or nanocomposite of the water-based material adheres to the microorganisms and cell walls to initiate the desired activity to protect the material and to minimize the loss of the material in water applications.

This may also be advantageous as the hydrated nanocomposite is not toxic to humans when consumed in small amounts, thus not requiring the material to be washed off before consumption. When applied to plants, it is even more preferred that the nanocomposite degrades into a fertilizer and is absorbed by the plant as a nutrient.

Means of solving the problem

A first aspect of the present invention includes a method wherein the method produces a biologically active substance by the following steps:

a) Preparing a precursor material, which is an inorganic compound powder containing one or more components, such as carbon dioxide, a metal carbonate, water, a metal hydroxide, a bicarbonate, and NH3, an amine, or an organic ligand, such as cellulose acetate or oxalate, such that, when heated, these components yield an oxide powder with a high porosity, preferably in the range of 0.5 or higher. The powder formed by heating is a metal oxide, which typically exhibits known bioactivity as a conventional nanomaterial, such as magnesium oxide or zinc oxide. A standard measure of precursor volatility is the loss on ignition when heated to a temperature below 1000°C. The loss on ignition should preferably be approximately 50% of the precursor mass. Various production techniques exist for such inorganic precursor compounds, wherein the powder is prepared as a crystalline material, typically precipitated from an aqueous solution, and ground to the desired particle size of 10-100 microns. Another method involves grinding a mineral precursor, such as a metal carbonate, hydroxide, or hydroxycarbonate. As an example, magnesium oxide mineral precursors include magnesite (magnesium _carbonate ), brucite (Mg(OH) ₂ ), hydromagnesite _4MgCO3.Mg (OH) _2.4H2O , and nesquehonite ( _{MgHCO3.OH.H2O} ), among others. Compounds include _{magnesium citrate (Mg6H6O7 ) ,} and magnesium oxalate ( _Mg2O4 ). All _of these compounds decompose upon heating to form magnesium oxide. Mixed metal compounds can either be produced or found as minerals, often _as double salts, such as dolomite.

b) calcining the precursor to produce porous nanocomposite oxide powders. The flash calcination process requires rapid evaporation of volatile components to produce particles with these properties:

(i) a particle size distribution measured in the range of 10-100 μm, for example by light scattering using shear mixing to ensure that the particles are not weakly bound to conventional nanoparticle polymers;

(ii) a high porosity (cavities left by volatile components);

(iii) a nanocrystalline structure wherein the grain length characteristics of the structure are in the nanometer range, preferably 20 nm or less, as measured by X-ray diffraction bands;

(iv) A surface area, on the order of 150 ^m2 /gm or greater, as measured, for example, by the Brunauer-Emmett-Teller (BET) method.

Surface area and porosity can be measured using techniques such as the Brunauer-Emmett-Teller (BET) method and small-angle X-ray scattering. A key requirement for producing these properties is the calcination process, which occurs at a relatively low temperature and a sufficiently short residence time so that the particles do not sinter during production, as rapid sintering would result in a loss of desirable properties. The particles may be crackled during this production process, so crackling is tolerable and can be controlled by the design of the calcination process and the choice of precursors.

An example of a continuous process involving a calciner is disclosed in PCT Patent Application No. WO2007045048 to Sceats and Horley, included herein as a whole, which occurs in a countercurrent indirect heating process using sufficiently high temperatures that the reaction is complete within seconds. Another example is a batch process in which calcination occurs at low temperatures under vacuum for an extended period of time.

(c) Hydrating the powder to produce a stable hydroxide slurry with a high solids content, preferably in the range of 50-60%. The desired properties of the slurry are that it does not settle rapidly, exhibits minimal syneresis, and has a low viscosity that allows it to be metered into a spray system for many applications. These properties can be measured by drying the slurry and taking into account the same properties measured for the calcined powder. The goal of the hydration process is to ensure that hydration occurs within the particles, directly forming the hydroxide from the nanocrystals, rather than the traditional process where the hydroxide crystals precipitate from solution. The slurry composition to achieve this process may require the use of cosolvents, temperature, and pressure to prevent precipitation mechanisms. The goal is to ensure that the hydrated material contains high-energy surface defects that are responsible for biological activity. Such defects occur at the boundaries of the hydrated particles, and the limited hydration ensures that the concentration of surface defects is maximized. An example of a hydration process is disclosed by Sceats and Vincent, for example, in AU2013904096 (incorporated herein by reference).

The present invention also discloses magnesium oxide powder or a slurry material having long-lasting biocide activity, as well as processes and apparatus for producing such biocide slurries. In one form, a biocide slurry or powder comprising particles ranging from 50 to 100 microns in size and comprising nanocrystalline hydroxide or oxide microcrystal aggregates is provided. In aqueous slurry form, additives are used to stabilize the slurry, providing a long shelf life and low resistance to shear thinning. The microcrystals are characterized by a high level of defects derived from superoxides formed during the production process. The mineral precursors are preferably the minerals magnesite and dolomite.

In another form or aspect of the invention, the biocide response is achieved by the addition of auxiliary toxins including hydrogen peroxide, ozone, traditional molecular biocides or nanoparticles which are preferably absorbed within the particle and enhance the inherent biocidal properties.

In another form, the powder can be dispersed to provide a biocide that acts through its dehydration effect, and the powder continues to provide a biocidal response after hydration. The benefit of the biocide is specifically tailored to the intended use, where one or both of the dehydration reaction and the resulting superoxide deficiency may function as an insecticide, fungicide, bactericide, or viracide. For example, in the storage and transportation of pellets, where it is desirable to maintain a low water vapor atmosphere, a non-toxic biocide powder that achieves its biocidal action through dehydration would be desirable. In other applications, such as additives for processed foods, applications with high water content, such as slurry products, are often desired.

In another form, the powder can be used in industrial applications where nanoparticle composites may have advantageous properties, such as catalyst matrices.

The powdered or slurry product preferably has a shelf life of several months and can be used as a raw material for the production of (a) foliar sprays for agricultural applications, or (b) a food additive as an inherently non-toxic biocide, or (c) as an additive added to fibers or polymers to serve as a base for gauze or wipes, or (d) dried to produce a powder or granular form, or (e) mixed with oil to form an emulsion, or (f) aerated to produce a foam or mist, or (g) a catalyst substrate.

Further aspects of the invention may include: a method for producing a biocide powder or a chemical antidote powder from a carbonate compound, comprising the steps of: grinding ore to produce a powder having a broad particle size distribution in the range of about 1-100 microns, with an average particle size selected from about 10-20 microns, preferably about 10 microns, and calcining the powder in an externally heated countercurrent flash calciner to produce an oxide having a high surface area and a high degree of calcination.

A preferred process for producing a pesticide slurry or chemical antidote powder slurry may further include forming a stable, easily thinnable slurry containing approximately 60% hydrated oxide solids after hydration of the final product by mixing the powder with water while maintaining the temperature at or near the boiling point of water until hydration is complete, applying shear mixing, adding a carboxylic acid or salt as a diluent, quenching the slurry to a temperature below 60°C, cooling the slurry to ambient temperature, and adding an additive to enhance biocidal properties.

Preferably the carbonate compound is magnesium, in which case the oxidized surface area is preferably greater than 150 ^m2 /gm, more preferably greater than 190 ^m2 /gm, and the degree of calcination is preferably greater than 90%. Preferably the carbonate compound may also be dolomite, in which case the degree of calcination will produce a semi-solid calcined dolomite _MgO.CaCO3 , preferably with a surface area greater than 30 ^m2 /gm.

The preferred carbonate compound may also be hydrated magnesium carbonate, including hydromagnesite or nesquehonite, in which case the extent of calcination will produce magnesium oxide, preferably with a surface area greater than 230 ^m² /gm. The preferred carboxylic acid is acetic acid, and the preferred carboxylates are magnesium acetate and calcium acetate. A preferred additive may be an aqueous solution of hydrogen peroxide. A preferred additive may also be ozone, sprayed into the slurry. A further preferred additive may be a molecular or nanoparticle biocide. Preferably, the additive is a dispersant.

Preferably, the slurry or powder is used to create any spray, or mixed with oil to form an emulsion, or processed into a foam or mist.

A further aspect of the invention may include a reaction apparatus for producing pesticide powder or chemical antidote powder from carbonate minerals, comprising: a grinder for the carbonate mineral; and an externally heated countercurrent flash calciner for producing high surface area oxides from the ground carbonate.

Preferably, a reaction apparatus for producing an insecticide slurry or chemical antidote slurry powder comprises: a reaction vessel having a feed port for calcined alkali carbonate powder and a water inlet; a shearing device for shearing the reaction mixture; and a steam outlet for releasing steam from the reaction vessel, allowing the heat of hydration to control the temperature of the reaction mixture to control the reaction, allowing water in the reaction mixture to boil off as hydration proceeds, and removing excess heat through the steam outlet to maintain the reaction temperature at the boiling point. A method for quenching the slurry temperature to below 60°C, preferably by transferring the slurry to a cooled vessel; a method for reducing the slurry temperature to ambient temperature; and a method for spraying the slurry with ozone, if necessary.

A further preferred aspect of the present invention may include a chemical composition for use as a biocide, wherein the composition comprises: a spray slurry of calcined powder suspended in water, wherein the particles have a porosity greater than 0.5, and wherein the surface microstructure of the particles comprises at least one nanocrystalline structure located on the outer surface of the particles. Preferably, the composition is calcined magnesite powder.

The preferred particles may be adapted to allow release of microstructures from the surface of each particle at predefined time intervals. Additionally, the preferred particles may be formed as nanoparticles adapted to provide a high redox potential.

Further inventive forms will be readily apparent from the description, drawings, and claims.

In the present invention, the words "comprising", "including" and the like are to be interpreted as their contents rather than their limitations, in a sense, "including but not limited to".

An invention is cited in a document as at least one technical problem described or as background art. The present invention aims to solve or improve at least one technical problem, which may produce one or more beneficial effects defined in the invention document. The present invention is described in detail in the preferred embodiments of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention are intended to be better understood and apparent to one of ordinary skill in the art in the following description, given by way of example only, with reference to the accompanying drawings, which are as follows:

FIG1 is a schematic diagram of a method for producing a stable, thin, high solids biocide slurry using light-burned magnesium powder.

DETAILED DESCRIPTION

Preferred embodiments of the present invention will now be described with reference to the accompanying drawings and non-limiting examples.

An example of a manufactured product can be described by considering the process flow diagram of FIG. 1 where magnesium hydroxide is a probiotic or biocide.

In this embodiment, the first step involves crushing and grinding the carbonate mineral, magnesite (essentially magnesium carbonate), into a particle size distribution close to that found in the final product. This can be achieved by setting the cutoff of the classifier and the residence time in the mill. Typically, the ground material will have a low-grade particle size of approximately 1 micron, an upper particle size of approximately 100 microns, and an average particle size in the range of 10-20 microns. Mineral impurities such as sand, talc, and magnetic particles are extracted during the process, if desired. The exact distribution depends on the mineral source, whether microcrystalline or cryptocrystalline, the impurities, the grinding machine, and the mill settings. It should be noted that there is no specification for the presence of any nanoparticles (i.e., with a diameter less than 0.1 micron). Generally, such particles are undesirable because, like fine particles, they are difficult to filter from the mill air. These particles are also handled in the following steps to address common customer and community concerns regarding nanoparticles. The mill is preferably a mill that processes the ground particles in air and removes particles above 1 micron before further grinding. This is known in the prior art.

The second step of the process is calcination, in which the magnesite is calcined. It is important that the treated particles exhibit minimal sintering during the calcination process, achieving a degree of calcination, preferably exceeding 95%. The most fundamental measure of the impact of sintering is the specific surface area, which should be greater than 150 ^m² /gm, preferably greater than 190 ^m² /gm. X-ray diffraction analysis of MgO powders reveals a line broadening, a measure of the particle's crystalline structure and, when compared to the powder's surface area, corresponds to a crystalline order of approximately 20 nanometers or less. This is the same X-ray diffraction curve observed in nanomaterials. However, in contrast, the particle size of nanomagnesia is commensurate with the crystallinity of the powder, whereas in the products of the present invention, the particle size is several orders of magnitude higher, i.e., approximately 10 microns compared to 20 nanometers. The fundamental proposition of the present invention is that the biocide or probiotic activity originates from crystallinity, not particle size.

The type of calciner is crucial to achieving the aforementioned properties. A primary requirement is that the process of eliminating the effects of sintering be extremely rapid, preferably within seconds. This means that the calcination process is rapid. A secondary requirement is that the particles experience the lowest possible temperature during this process. Conventional flash calciners introduce the particles into very hot combustion gases, and from that point on, the gas temperature decreases to extract energy from the reaction in the gas stream. Furthermore, not all particles experience the same conditions. The end result is that the outer surface of the particles is extensively sintered, making it difficult to achieve a surface area exceeding 50 m2/g. Small particles are sintered most extensively. A preferred calciner, such as that described by Sceats and Horely in WO2007/112496 (incorporated herein by reference), uses indirect countercurrent heat to produce powders with a surface area of preferably 150 m2/g or greater. During calcination, there is typically some cracking of the input particles, and a shoulder often appears in the 0.1-1 micron region of the particle size distribution. Control of the external burners along the calciner ensures the desired heat transfer to the particles, allowing the degree of calcination and surface area to be controlled. The system is known per se and can operate at a production level of approximately 5 tons per hour, with 95% calcined particles having a surface area of 190 ^m² /gm and a crystallinity of 20 nm, with negligible particles below 0.1 micrometers. These particles are very strong, resist grinding, and cannot be significantly decomposed by ultrasonic treatment. These particles are not aggregates of nanoparticles. The crystallites, although porous, are firmly bonded.

An important factor in determining the biocidal impact is the high surface area of the calcined powder. There is a range of stable magnesium bicarbonate compounds, such as hydromagnesite and nesquehonite, in the form ( _MgCO₃ ) _x (Mg(OH) _₂ ) _y ( _H₂O ) _₂ , which contain very large volume fractions of _H₂O and _CO₂ . When these materials are calcined, they produce magnesium oxide with very high surface areas, on the order of 500 m²/g. These compounds can be found as rare minerals or synthesized by injecting _CO₂ into a magnesium hydroxide slurry as described below, isolating and drying the powder before calcining. This method provides materials with a high biocidal impact.

The powder product from these two process steps can be used as a biocide powder where ideal dehydration properties are desired. Where a slurry product is desired, the third step of the process is to hydrate the slurry. This process is described by Sceats and Vincent, for example, in AU2013904096 (incorporated herein by reference), as a method in which several tons of slurry are produced per hour to match the production rate of the aforementioned calciner. The high surface area of the particles allows the hydration reaction, when vigorously mixed, to release significant amounts of heat and boil water. This establishes a set point at which heat activates hydration, and excess heat is released by boiling. The use of a shear mixer provides the uniform, controlled agitation required for processing. During the reaction, acetic acid is added to the slurry during the shear mixer operation to provide the necessary material for thinning. As the temperature begins to drop from heat loss until the reaction is complete, the slurry is preferably rapidly quenched to below 60°C and then allowed to cool to ambient temperature for the next processing step. The end result is a hydrated slurry that is stable over many months of settling and readily shear-thinns to allow pouring and processing. The slurry has the same inherent biocidal activity as the nanoparticles, but should be diluted in water for foliar spray application. This will be discussed below. Importantly, there is no significant loss of biocidal activity over the months of slurry life.

The fourth step, if necessary, is to add adjuvants to either the powder or slurry product to enhance the biocidal properties of the inherent biocidal response discussed above and below. Numerous such adjuvants are available. These can be hydrogen peroxide or ozone, which can be added to saturate the crystals and bind to the Mg(OH) ₂ surface with free radicals as superoxide ions, hydroperoxide anions, oxygen radicals, and hydroxyl radical sites. Additionally, acetate ions can be further converted to peroxyacetate ions, which are stable in a slurry at a pH of 10.4. Impurity ions such as Fe2 ⁺ and Fe3 ⁺ are removed during milling to degrade these radicals. Hydrogen peroxide or ozone is used to supplement the intrinsic radicals formed during calcination and hydration. Ozone is added to the slurry via a sparging of ozone-laden air. Other adjuvants include a wide range of established biocides, including all those listed in U.S. Patent 6,827,766 B2, or nanoparticles such as AgO and its zinc oxide. Depending on the specific adjuvant and the amount added, slurry stability can be reestablished by adding a dispersant. The use of adjuvants is generally not preferred because it may render the product toxic to humans and increase production costs compared to the inherent biocides developed in the previous steps.

The inherent biocide produced using steps 1-4 above was used to produce either magnesium oxide powder or a 60% solids content slurry, where the solids refer to magnesium hydroxide particles with a particle size range of 0.4 to 50 microns as measured by a particle size analyzer. For the slurries, the particles were confirmed by drying the slurries at approximately 100°C and measuring them by TGA and DSC, comparing these with analytical-grade magnesium hydroxide. The nanocrystallinity of the magnesium oxide or magnesium hydroxide particles was determined from the line broadening of the diffraction peaks of the dried slurries using Scherer's equation of 20 nm. Scanning electron microscopy (SEM) of the dried magnesium hydroxide powder product revealed a particle shape comparable to that of porous magnesium oxide powders produced by calcination, with pores filled by reaction with water. The surface area of the MgO powder was measured to have a BET surface area of 190 m2/g, compared to 20 m2/g for the dried magnesium hydroxide slurry.

The inherent biocidal activity of the slurry was established using in vitro measurements and preliminary crop trials. For in vitro studies, the slurry was diluted to 1% by adding water and sprayed onto prepared Petri dishes containing spots of fungi, bacteria, or test virus strains that had been cultured and grown for at least 24 hours. The rate of growth of the rings was measured over time, and the biocidal effect was determined by the degree of inhibition of the ring growth rate. Studies were conducted on several fungi, and the effects of a broad-spectrum antifungal agent and comparable commercial fungicides were observed.

In preliminary crop trials, spraying of a diluted slurry with a variety of crops, such as grapes, avocados, and bananas, resulted in fungal outbreaks and a biocidal effect, as measured by crop health, specifically the presence of fungi, compared to unsprayed fields. Upon inspection, no fungi were observed in the sprayed areas after seven days. It was noted that the powder adhered strongly to the leaves, and that leaf appearance improved, suggesting magnesium absorption into the plant, promoting greater photosynthesis. Such leaf characteristics included color and leaf thickness.

In tests of insecticide response, magnesium oxide powder caused insects to retreat from wheat. After a few days, insect numbers had been greatly reduced, and the response was similar to that of dehydrated diatomaceous earth.

It is obvious that the diluted slurry has similar biological activity to the reported nano-hydroxides. Without being bound by theory, the nano-crystalline properties of the magnesium oxide powder followed by the method and the similarity of the crystallization properties of single nano-MgO are common features. The established tendency of the crystal surfaces of MgO and Mg (OH) ₂ to stabilize free radical species such as superoxide, hydroxyl, oxygen atoms, and each hydroxide known to have the activity of breaking the original microbial epithelial cell wall is the most likely explanation for this characteristic. The high density and stable nature of these sites provide the basis for the long-life performance of the slurry and explain its decomposition of these groups to produce oxygen, which would otherwise reduce its effectiveness over time. It is also obvious that in tests with powder products, as long as it is a typical dehydrated insecticide response. Without being bound by theory, the response can be a combination of dehydration and superoxide response.

Naturally, large particles are less capable of close contact with microbial surfaces than nanoparticles. However, all MgO particles have negatively charged surfaces, and the activity against both Gram-negative and Gram-positive microorganisms suggests that close contact is not required. A more likely explanation is that free radical species are in equilibrium with water and transferred from the particles to the microorganisms by diffusion. In the case of slurries, it is the surface area of the hydroxide particles that controls the process, and it should be noted that the surface area of hydrated nanoparticles is 30 m2/g, a result similar to that measured for powders. The increased activity of smaller nanoparticles may simply be a reflection of the increased geometric surface area of the smaller particles. It is worth noting that the tendency of nanoparticles to aggregate is well-known, and diagnostic testing of particle size is performed by sonication prior to particle size determination. Nanopowders in suspension provide aggregates for their biocide activity. This is consistent with the premise of the present invention that particle size is not the source of biocidal activity. In the dehydrated case, the surface area of the MgO particles is approximately 190 m2/g. The high rate of dehydration is linked to surface area, and furthermore, the particle surface is very rough and capable of penetrating the insect exoskeleton.

The targets aren't just microorganisms, as mentioned above, but also chemicals. A different slurry application is the deactivation of toxic chemicals that would otherwise harm plants, animals, and humans. Nanomagnesium oxide has been used for this purpose, as a source of free radical species in the attack and classification of many agents, such as those that can be deployed as chemical and biological warfare agents. This is because many of these chemicals acquire toxic effects through free radical production, and the free radicals in slurries, or dispersed slurries, can react and destroy the carriers of these compounds. Magnesium oxide powder or slurries can be used to render these chemicals ineffective.

The slurry of the present invention is not typically deployed as a 60% solids biocide. Rather, it is used to create a concentrate of biocide for various applications. In agriculture, the preferred method of biocide application is through a water spray system to avoid wind damage to crops. A common method is to use a slurry of the material diluted to approximately 1% by spraying water. This foliar application method has wide industry acceptance. In this case, the magnesium hydroxide-based material has the added benefit of providing a source of magnesium, an essential nutrient for photosynthesis. The spray has particles less than 100 microns, preferably 25 microns in diameter, to avoid clogging of the nozzles. The use of the spray can also be suitable for medical applications. However, in this regard, there are also applications for incorporating the material into masks to reduce infection from atmospheric microorganisms or wipes to remove microorganisms from surfaces.

MgO lace gauze or other fabric materials can be made by reacting a powder or a slurry of materials formed from various polymers, and applying the mixture to the fabric with the purpose of adsorbing particles on the gauze. In another application area, in the food industry, a non-toxic biocide magnesium hydroxide slurry can be added to a liquid product, or can be added as a powder to a dry product. There are existing processes for treating the slurry, such as using conventional treatments to produce a desired particle size by grinding the dry product, or by combining with suitable materials to produce particles for use in applications. It is worth noting that the MgO powder can be used in food because the hydration method can be used with the food product itself. In another application, the product should be able to be dispersed into a spray or mist, or foam, to obtain coverage of a large area, such as with a toxic chemical spill.

In another application, the slurry should be mixed with existing biocides as adjuvants. This includes conventional water-soluble biocides, typically molecules that adsorb onto the particles to provide the desired biocide activity. The formation of emulsions with oils containing oil-soluble adjuvants is another such application.

Magnesium oxide is one particular oxide material that can be used, with the advantage of the availability of inorganic precursors. Another embodiment uses dolomite, where the degree of calcination of the magnesium sites and calcium sites is controlled to obtain the desired biocidal properties of the dolomite.

Although specific embodiments of the present invention have been described, it will be apparent to those skilled in the art that the present invention may be embodied in other specific forms without departing from its essential features. Therefore, all aspects of the present embodiments and examples are intended to be illustrative rather than restrictive, and all variations within the meaning and equivalent ranges thereof are intended to be included therein. It should also be understood that, unless otherwise indicated, any reference to prior art known herein does not constitute an admission that such prior art is well known to those skilled in the art.

In this specification, reference is made to the term "probiotic" to mean any material that is beneficial in promoting or enhancing the microbial balance in a treatment area, location or site.

Probiotics is also a general name for fertilizers, which refer to the use of beneficial soil bacteria to produce microbial ecological methods to restore soil symbiosis ^[1] . In this application, we extend the definition to include symbiotic relationships with plants and point out that plants absorb applied magnesium as fertilizer through the stomata of their leaves. In fact, when foliar sprays are applied to leaves, the impact of magnesium absorption as a fertilizer shock is noted by increased chlorophyll color and increased leaf thickness. The most plausible theory why pathological fungal growth is inhibited is due to the presence of reactive oxygen species ^2. Plants can ramp up the production of reactive oxygen species as a defense against microbial attack by reactive oxygen species that attack the primary cell wall of the fungus. In response, the fungus can produce chemicals that react and neutralize the reactive oxygen species ^[2] . The same model of activity is used by pathogenic bacteria, especially anaerobic Gram-negative bacteria. This symbiotic relationship is associated with the relationship between plants and beneficial Gram-positive bacteria, which are essential for a healthy environment for growth. These bacteria are aerobic, and ROS increase the oxygen level in the environment. Such bacteria are present in soil and on leaves ^[3] . The effect of the probiotics is that, in addition to the increase in the nanoparticles or nanoparticle complexes (MgOH) ₂ , they provide a higher supply of reactive oxygen species than the plants. The slow dissolution of the crystals in the acidic environment leads to a long-lasting and biologically active continuous supply of ROS. No new chemicals are introduced in the process.

Although the present invention has been described with reference to specific embodiments, those skilled in the art will appreciate that other forms may be invented that are consistent with the broad principles and spirit of the invention as described herein.

The present invention and the described preferred embodiments thereof are seen to include at least one characteristic that is industrially applicable.

References

[1] United States Patent and Trademark Office, Trademark Trial and Appeal Board, Serial No. 77758863 (2013).

[2] For example, in the case of rice blast fungus: Kun Huang, Kirk J. Czymmek, Jeffrey L. Caplan, James A. Sweigard & Nicole M. Donofrio (2011); Inhibition of plant-produced reactive oxygen species is required for successful infection by rice blast fungus, Virulence, 2: 6, 559-562, DOI: 10.4161/viru.2.6.18007.

[3] Bacteria and Pseudomonas syringae in leaf ecosystems - pathogens, ice nuclei and epiphytes, Susan S.Hirano and Christen D.Upper, Microbiol.Mol.Biol.Rev.September 64, 3624-653 (2000).

Claims (14)

1. A method for producing a biocidal powder, chemical detoxification powder, or catalyst carrier from a carbonate compound, comprising the following steps: a) Grinding minerals to produce powder with a wide particle size distribution, the particle size distribution of which ranges from 1 to 100 micrometers and the average particle size is between 10 and 20 micrometers; b) Calcining powders in an externally heated counter-current flash calciner to produce oxides with high surface area, high porosity and high degree of calcination; c) After hydration, a stable, easily diluted hydrated oxide slurry with a final product containing 60% solids is formed, which is carried out by mixing water with powder, applying shear mixing under conditions where the temperature is maintained at or near the boiling point of water until hydration is complete, and adding carboxylic acid or salt as a diluent. d) Quench the slurry to a temperature below 60°C; e) Cool the slurry to ambient temperature; and f) Additives are added to enhance biocidal properties. 2. The method according to claim 1, wherein the carbonate compound is magnesite, and the surface area of the magnesite oxide is greater than 150 ^m² /gm, and the degree of calcination is greater than 90%. 3. The method according to claim 1, wherein the carbonate compound is dolomite, and the degree of calcination is set to produce semi-solid calcined dolomite _MgO.CaCO3 with a surface area greater than 30 ^m² /gm. 4. The method according to claim 1, wherein the carbonate compound is hydrated magnesium carbonate, including magnesia or trihydrate magnesia, and the degree of calcination of the hydrated magnesium carbonate is set to produce magnesium oxide (MgO) with a surface area greater than 230 ^m² /gm. 5. The method according to claim 1, wherein the carboxylic acid is acetic acid, and the carboxylate is magnesium acetate or calcium acetate. 6. The method according to claim 1, wherein the additive is an aqueous solution of hydrogen peroxide. 7. The method according to claim 1, wherein the additive is ozone, and the ozone is sprayed into the slurry. 8. The method according to claim 1, wherein the additive is a dispersant. 9. The method of claim 1, wherein the slurry or powder is used to produce any spray or to be mixed with oil to form an emulsion, or to be processed into foam or mist. 10. A reaction apparatus for producing biocidal powder, chemical detoxification powder, or catalyst carrier from carbonate minerals, comprising: A grinding machine for carbonate minerals; b. An externally heated counter-current flash calciner for producing high surface area oxides from milled carbonates; c) A second reaction vessel having an inlet for lightly calcined carbonate powder and a water inlet; d) A shearing device for shearing the reaction mixture; and e) A steam outlet for releasing steam from the reaction vessel to control the reaction under the following conditions: allowing the heat of hydration to raise the temperature of the reaction mixture, allowing water to be removed from the reaction mixture by boiling as hydration proceeds, releasing steam through the steam outlet to remove excess heat, and controlling the reaction temperature at the boiling point. f) A device for quenching slurry to bring its temperature down to below 60°C; g) A device for cooling slurry to ambient temperature; h) A device for adding solid or liquid additives to a slurry; i) A device for injecting ozone into a slurry. 11. A chemical composition suitable for use as a biocide, wherein the chemical composition comprises: a sprayable slurry of lightly calcined carbonate powder particles suspended in water, wherein the porosity of the particles is greater than 0.5, and wherein the surface of the particles includes a microstructure, the microstructure being defined as at least one nanocrystalline structure located on the outer surface of the particles. 12. The chemical composition according to claim 11, wherein the carbonate powder is magnesite. 13. The chemical composition of claim 12, wherein the particles are adapted to allow the microstructure to be released from the surface of each particle at a predetermined time interval. 14. The chemical composition of claim 13, wherein the particles are formed into nanoparticles suitable for providing a high redox potential.