THE FILED OF THE INVENTION

The subject of the invention is a process for the preparation of food-grade fulvic acid and/or humic acid from raw materials containing humic acid, such as peat, xyloid lignite, leonardite.

SATE OF THE ART

Humic acids are defined as organic molecules, mainly of an acidic nature, of chemically very diverse structure and size, with a high degree of polymerisation, formed mainly by the degradation of plant parts buried undergrounds, under aerobic and anaerobic conditions by soil bacteria and fungi, by physical, chemical and microbiological processes. Plant parts, which are predominantly solid and insoluble in water, are broken down and transformed by the organisms living in the soil and water by extracellular enzymes. Two processes, decomposition and synthesis, i.e. the humification of plant parts and the formation of humic substances, take place in parallel. Easily decomposable organic matter is quickly mineralized. As a result of mineralization and humification, the soil's organic matter is in constant dynamic change. Anaerobic conditions favour organic matter accumulation, aerobic conditions favour mineralisation. Compounds which are difficult to break down are combined with nitrogencontaining substances and polymerised to form dark coloured (from dark brown to black), high molecular weight humic substances, humic acids. During humification, carbon dioxide, sulphate, nitrate, and water are produced from the microbial metabolites, the nitrogen content and the number of alkyl groups decrease, and the aromatic character increases. Therefore, humic acids are very diverse; they typically have a different structure, composition and content for each geographical region, with different mineral profiles. Humification lasts from the incorporation of dead plant material into the soil to the formation of diamonds. The first step in humification is peat formation, so humic acids are mainly formed in the peat phase. Due to the continuous decomposition and aging process, the carbon content of humic substances increases continuously, and they are converted by carbonization into xyloid lignite, brown coal, black coal, where the humic acids are no longer present.

As a consequence, soil fractions suitable for humic acid extraction can include: peats, forest soils (mostly brown), xyloid lignites (leonardite and similar soil minerals), brown coals.

Peat and xyloid lignites are the most important in terms of extraction and utility.

The use of brown forest soils is not recommended because of their organic matter content and other animal and microbiological contaminants. They contain a lot of PAH (polyaromatic hydrocarbon) type compounds, resinous and waxy substances, which make the final product unsuitable for use in the food industry.

Due to their high carbon content and their aging, brown coals contain very small amounts of leachable humic acids, so their use is uneconomical due to low yields and the necessary pretreatment having high energy and chemical demand. Furthermore, they contain large amounts of heavy metals that accumulate in them (Hg, Pb, Cd, As, Al), and their removal is extremely difficult and costly. For this reason, they are not recommended raw materials for the preparation of humic acids intended for use in the food industry.

Humic acids and fulvic acids have many positive physiological effects and research has shown that they help to maintain healthy body function and contribute to reducing the physiological stresses of modem times (stress caused by processed food - preservatives, sweeteners, colorants, emulsifiers, GMOs, hormone stress, electrosmog, chemical stress, etc.).

The physiological effects of humic acids are discussed in the following publications, among others: Klbcking, R, Helbig, B. Medical Aspects and Applications of Humic Substance, Biopolymers for Medical and Pharmaceutical Applications. Weinheim, Germany: Wiley-VCH; 2005:3-16; Terratol L.L.C., 2002. Effects of humic acid on animals and humans; and Dr. Istvan Jurcsik: Huminanycigok szerkezetenek es elettani hatdsdnak vizsgdlata (in English translation: "Examination of the structure and physiological effects of humic substances"). Dissertation. Sopron, 1978.

In summary, the physiological effects of humic acids include the following: immune-enhancing, immunostimulating effect; electrolyte-balancing effect due to their organic mineral chelates; maintaining the pH balance of the body; detoxifying, purifying, digestion-supporting effect; the possibility of micronutrient supplementation; antiviral, antibacterial effect; energizing, vitalizing effect; intestinal flora supporting effect. They are also safe to use - without side effects under normal conditions.

Humic acids can be used excellently in food supplements (microelement supplementation, in addition to supporting the above effects); as a black food colouring; and their pharmaceutical and cosmetic uses can also be mentioned.

However, the achievement of these theoretically very beneficial effects is hindered in practice by a number of factors.

One fundamental problem is that humic acids and fulvic acids are complex groups of compounds, with no precise chemical definition that define and describe groups of compounds. Their definition is based on certain physicochemical properties, which cover substances with a wide range of contents and qualities (P. MacCarthy, R. L. Malcolm, C. E. Clapp, P. R. Bloom. An Introduction to Soil Humic Substances. 1990). The current generally accepted definition and grouping of the components of soils containing humic acid are summarized in Table 1.

Table 1

Accordingly, if a humic acid-containing soil is treated with alkali, humic acid is separated from the sediment; if this humic acid fraction is treated with acid, fulvic acid and a precipitated humic acid fraction are obtained. So, in theory, it is very easy to produce humic acid and fulvic acid, but their quality, content and therefore their usability is highly variable.

It can therefore be concluded that, in general, the quality/purity of the raw material determines the quality and purity of the product. Thus, in order to ensure that the product does not contain e.g. heavy metal contaminants, the use of a clean raw material is crucial.

A further disadvantage of the simple preparation method of humic acids/fulvic acids outlined above is that small amount of material can be recovered by extracting the "unbound" fulvic acid/humic acid fraction. Cracking is commonly used to increase the amount of fulvic acid/humic acid (e.g. HU1564/91 and HU 2447/91). However, thermal cracking is not very efficient, with high losses due to excessive decomposition; part of the humic acids/fulvic acids are oxidised to carbon dioxide during the process instead of cracking.

The product often has an unpleasant smell and texture, mainly due to residual sulphur compounds. This it is not a problem for e.g. in soil or agricultural use, but it is an important factor if the goal is to achieve a food-grade product.

We also note that after classic, alkaline extraction, during acid precipitation, fulvic acid always contains some acid residue ion, depending on the acid used for precipitation. In theory, this can be purified with an ion exchanger (Kuwatsuka, S., Watanabe, A., Itoh, K. and Arai, S. (1992): Comparison of two methods of preparation of humic and fulvic acids, IHSS method and NAGOYA method. Soil Science and Plant Nutrition 38(1) p. 23-30), but this is a very expensive procedure, so it has not spread in practice. However, ion-free fulvic acid/humic acid has many advantages. On the one hand, ion-free fulvic acid can exist in both liquid and powder form, and is also soluble in alkaline and acidic media, and can be re-dissolved at any time, so its use is not restricted. On the other hand, the ion-free form makes it possible to obtain nearly 100% pure fulvic acid/humic acid (the total mass of the substance is the useful fulvic acid/humic acid). Furthermore, the presence of the counterion is also not advantageous, because in contact with other substances (e.g. during a possible formulation or application) they form a salt, which can be disturbing, and they also block free binding sites on fulvic acid/humic acid, although it is typically their free binding sites that are valuable for their biological activity.

There is therefore a need for a process that can produce fulvic acid and/or humic acid with good yields, in an environmentally friendly manner, in food-grade quality, and that can ensure food-grade quality using raw materials of varying quality.

Furthermore, there is a need for a process that can produce fulvic acid and/or humic acid in a form essentially free of counterions.

BRIEF DESCRIPTION OF THE INVENTION

The subject of the invention relates to a process for the preparation of food-grade fulvic acid and/or humic acid from peat, xyloid lignite or leonardite, wherein

(i) the raw material is subjected to acid pretreatment with an aqueous solution of an acid selected from tartaric acid, succinic acid, citric acid and their mixtures, with a pH value of no more than 2, and then a solid-liquid separation is carried out to obtain a solution and a sediment;

(ii) the sediment obtained in step (i) is subjected to thermal cracking using H2O2, where H2O2 is added to the sediment in one portion, and then the temperature is gradually increased from ambient temperature to boiling, and then a solid-liquid separation is carried out to obtain a fulvic acid solution and a sediment; then

(iii.a) optionally, the fulvic acid solution obtained in step (ii) is cooled and/or allowed to stand, then a solid-liquid separation is carried out to obtain a refined fulvic acid solution; and/or

(iv.a) optionally, the solution obtained in step (ii) or (iii.a) is dried to obtain fulvic acid crystals; and optionally

(iii.b) the sediment obtained in step (ii) is subjected to alkaline extraction, then the extraction mixture is subjected to thermal cracking using H2O2, where H2O2 is added to the extraction mixture in one portion and then the temperature is gradually increased to boiling, then solid-liquid separation is carried out to obtain a humate solution and a sediment; then

(iv.b) optionally, the humic acid is precipitated from the solution obtained in step (iii.b) using a food-grade acid, then a solid-liquid separation is carried out, to obtain a sulphur-containing solution and desulphurised humic acid; and

(v.b) optionally, the desulphurised humic acid obtained in step (iv.b) is dissolved in an alkaline medium, to obtain a humate solution; and

(vi.b) optionally, the humate solution obtained in step (iii.b) or the desulphurised humic acid obtained in step (iv.b) or the humate solution obtained in step (v.b) are dried, to obtain a humic acid powder or a crystalline humate product.

In order to use the raw material as fully as possible, we preferably carry out the process to the end, that is, we produce both fulvic acid and humic acid in food-grade quality. Therefore, preferably, in addition to steps (i) and (ii), step (iii.b) is also carried out mandatorily, and one or more of the additional optional steps can be performed depending on the purity of the products obtained in steps (ii) and (iii.b) and the desired form of the final product (solid, liquid, salt or salt-free form).

If the goal is only to produce food-grade fulvic acid, then only steps (i) and (ii) are mandatory, and steps (iii.a) and (iv.a) are optional. The sediment obtained in step (ii) as a by-product, is suitable e.g. for agricultural use.

If the goal is only to produce food-grade humic acid, steps (i), (ii) and (iii.b) must be carried out, the fulvic acid solution obtained in step (ii), if it is not of food-grade quality, may be considered as a useful by-product without further refining (it is suitable e.g., for agricultural use), and optionally, one or more of steps (iv.b), (v.b), (vi.b) can be performed to achieve the food-grade quality and the desired form of humic acid.

In one embodiment of the invention, in step (i), the acid pretreatment is performed with a mixture of tartaric acid, succinic acid and citric acid. Preferably, a mixture of tartaric acid, succinic acid and citric acid in a molar ratio of ( 1 -4) : ( 1 -3): ( 1 -4), for example in a molar ratio of about 3:2:3, is used.

In one embodiment, the acid mixture is used in a mass of about 8-10 times the mass of the starting peat.

In one embodiment, in step (i), the raw material and the acid mixture are boiled with stirring, typically for about 1-4, for example about 2 hours.

In one embodiment of the invention, in step (ii), hydrogen peroxide is used as an aqueous solution of 20-60%, preferably about 30%. In the mixture of the hydrogen peroxide solution and the sediment, the the sediment dry matter content is typically about 15-40% by weight, preferably about 25-35% by weight, for example 30% by weight.

In step (ii), boiling is preferably continued until the foaming stops.

In one embodiment, in step (ii), a catalyst is also used, preferably a Mn, Fe or Cu catalyst, typically a Cu catalyst, for example copper(II) sulphate 5 -hydrate.

In one embodiment of the invention, in step (iii.b), the alkaline extraction is carried out using a solution of NaOH, KOH, NaHCO;. KHCO3 or a mixture thereof, preferably a solution of NaOH, KOH or a mixture thereof. During the alkaline extraction, the pH value of the extraction mixture is preferably at least 12.5.

In step (iii.b) a catalyst is preferably used during the alkaline extraction, preferably disodium hydrogen phosphate or sodium dihydrogen phosphate.

In one embodiment, in step (iii.b), the alkaline extraction is performed at about 50-80°C for 1-3 hours.

In one embodiment, in step (iii.b), the hydrogen peroxide is used as an aqueous solution of about 20- 60%, for example about 30% for the thermal cracking.

The required amount of hydrogen peroxide basically depends on the amount of the sediment, a person skilled in the art is able to determine the optimal amount. The required amount of the solution is calculated by taking into account the concentration of the solution. In one embodiment, the amount of H2O2 used is about 0.03-0.05 times the weight of the dry matter content of the sediment, that is, the amount of the 30% hydrogen peroxide solution is about 0.1-0.15 times, for example about 0.12 times the weight of the dry matter content of the sediment.

During the thermal cracking in step (iii.b), the boiling is preferably continued until the foaming stops.

In step (iv.b), for example, acids selected from citric acid, malic acid, tartaric acid, succinic acid, acetic acid, lactic acid and mixtures thereof can be used as food-grade acid.

In step (iv.b), the pH value is preferably reduced below 2.0 by adding the food-grade acid.

In step (v.b), for example, a solution of NaOH, KOH, sodium hydrogen carbonate, potassium hydrogen carbonate, lysine and/or arginine can be used as an alkaline medium. The dissolution of humic acid is usually achieved at a pH value of about 10.5-11.5.

Depending on the optional steps, the product of the process can be a solution or a solid, in a counterion- free, or counterion-containing form.

In terms of their biological activity, counterion-free forms are advantageous, e.g. counterion-free fulvic acid, as well as counterion-free but water-soluble forms of humic acid, i.e. amino humates (lysino- humate, argino-humate).

DEFINITIONS

In the description, the following groups of substances are distinguished within humic substances, in accordance with the above definition:

- Fulvic acids (soluble in both alkali and acid)

- Humic acids (dissolvable in alkali, insoluble in acid), including:

- Brown humic acid, which dissolves in alkali without the use of an electrolyte (it usually makes up the majority of humic acids)

- Gray humic acid, a humic acid with larger molecules than brown humic acid; to dissolve it, an electrolyte is also needed in addition to an alkali (there is usually a small amount of this)

- Humin fraction: contains humins, which are insolubne in acid, alkali, or alkaline-electrolyte extraction. The humin fraction can be further divided into the foilowing:

- bitumen fraction (phase dissolvable in benzene, insoluble in alkali, acid, aqueous media)

- insoluble mineral oxides, hydroxides, precipitated compounds, and organic substances with a high degree of polymerization that are already at such a stage of humification (carbonization) that they cannot be dissolved in any way.

In the description, food-grade quality' means compliance in particular with tire following parameters, the number of relevant standards being given in parentheses:

- heavy metals: Arsenic < 10 mg/kg, Lead < 3 mg/kg, Cadmium < 1 mg/kg, Mercury < 0.1 mg/kg (MSZ 21470-50:2006)

- microbiological purity: total germ count <10000 CFU/g (MSZ EN ISO 4833:2003), salmonella negative (MSZ EN ISO 6579:2006), E-coli negative (MSZ ISO 16649-2:2005), mold and yeast <1000 CFU /g (ISO 21527-2:2007), pathogen negative;

In the description, the "flooding" method means that the entire amount of hydrogen peroxide is added to the reaction mixture at once. BRIEF DESCRIPTION OF THE FIGURES

Figure 1 is a flowchart of the process according to the invention; the optional steps are also shown in the figure.

Figure 2 shows the fulvic acid yield as a function of temperature, in the case of peat raw material from Alsopahok, using the "flooding" method. The white column shows the fulvic acid yield obtained by thermal cracking without acid digestion, the black column shows the fulvic acid yield obtained by thermal cracking after acid digestion.

Figure 3 shows the fulvic acid yield as a function of temperature, in the case of leonardite from Dudar (dudarite) as raw' material, using the "flooding” method. The white column shows the fulvic acid yield obtained by thermal cracking without acid digestion, the black column shows the fulvic acid yield obtained by thermal cracking after acid digestion.

Figure 4 sho ws the fulvic acid yield in the case of comparative experiments in which hydrogen peroxide was added gradually, in small portions, for 10%, 20% and 30% peat dry matter, respectively.

Figure 5 shows the fulvic acid yield plotted as a function of the mass of the 30% hydrogen peroxide solution used, in the case of thermal cracking using the "flooding" method and peat from Alsopahok as a raw material.

DETAILED DESCRIPTION OF THE INVENTION

Preparation of the raw material

The starting material of the process according to the invention is preferably peat or xyloid lignite (leonardite). If necessary, the crude, mined raw' material is prepared in a manner known in the field. The non-sticky raw ⁷ material is crushed, for example with a hammer mill or a ball mill, to an average particle size of about 1 mm or finer. If a wet, sticky raw' material is available which is unsuitable for grinding, the material is dried before grinding. This can be done by leaving it to rest in a dry place, or by using, for example, a drying oven, in which case the temperature is preferably set at a maximum of 60-80°C.

Acid digestion of the raw material

As the first step of the process, the prepared raw material is subjected to an acid treatment using an aqueous solution of an acid selected from tartaric acid, succinic acid, citric acid and their mixtures. The listed acids can be used alone, but a mixture of any two or even all three can be used. A mixture of tartaric acid, succinic acid and citric acid is preferably used, for example in a molar ratio of about (1- 4):( 1 -3):( 1 -4), preferably in a molar ratio of about 3:2:3. The acid or acid mixture is preferably used in the form of an aqueous solution with a maximum pH of 2.

The acid or acid mixture is used in such an amount that, based on the dry matter of the raw material, the total amount of the acid(s) is about 5-20 m/m%, preferably about 10 m/m%. The mixture of the raw material and the acid or acid mixture is stirred to obtain a completely homogeneous smooth suspension, then the suspension is heated, preferably boiled while stirring. Boiling may be carried out for about 1- 4, e.g. for about 2 hours.

After boiling, the digested sample is subjected to liquid-solid separation while still hot. For this, we can use e.g. centrifugation or, where appropriate, sedimentation, if the necessary time, typically about 24- 48 hours, can be provided.

The liquid phase obtained by separation is typically lemon yellow or orange, transparent solution containing minerals (in the form of citrate -tartrate -succinate complexes) and unbound natural fillvic acids and fulvate salts and other organic substances. It is an independent by-product of the process, which is suitable for use in soil conditioners and EC foliar fertilizers.

The sediment of the sample contains bound fulvic acids, humic acids, humin matter and precipitated mineral salts. The sediment is collected for further processing.

We note that the natural fulvic acid in the raw material is not part of the fulvic acid end product in our process (unlike traditional processes), but rather it is a part of the useful by-product of the acidification step.

By using acid digestion, contaminant ions are removed from the raw material, thereby it is possible to produce a food-grade final product even from lower quality raw material from more polluted areas. The acids used are organic acids suitable for use in the food industry, so they can be well integrated into the process aimed at food-grade quality. There is no need to wash them off several times, as their residual substances are not dangerous. Since the minerals are removed from the raw material in a chelated complex, a useful by-product is formed (it can be used, e.g. as an additive to soil conditioners, as an additive to foliar fertilizers). Therefore, no by-product is formed that needs to be disposed of. Their precipitation salts (calcium, magnesium) remain in the precipitate form until the end of the process and are also harmless. They do not destroy the humic substance, and the acid digestion using them is not a highly oxidative process. Since they are weak acids, they are slightly corrosive, which is important from the point of view of the equipment used. Bonded acid extraction - thermal cracking I

The next step of the process is aimed at extracting the bound fulvic acid from the sediment left after acid treatment (that is, substantially cleaned of metal ions and no longer containing free fulvic acid). For this, thermal cracking is carried out with hydrogen peroxide, ideally in the presence of a catalyst, using a so-called "flooding" method, which means that the entire amount of hydrogen peroxide is added to the sediment at once. During the process, the temperature is gradually increased from ambient temperature to boiling (to about 100°C). We have found that with this method, the yield of fulvic acid is significantly increased compared to the thermal cracking commonly used in the field, during which hydrogen peroxide is added gradually at a constant high temperature (HU 1564/91 and HU 2447/91). This will be confirmed by a comparative example later on.

During thermal cracking, hydrogen peroxide is used as an aqueous solution, preferably as an aqueous solution at a concentration of about 20-60%, for example of about 30%. In the mixture of the hydrogen peroxide solution and the sediment, the sediment dry matter content is typically about 15-40% by weight, preferably about 25-35% by weight, for example 30% by weight.

Preferably, a catalyst is also used, which can be a catalyst commonly used for redox reactions, e.g. Mn, Fe or Cu catalysts, such as copper(II) sulphate 5 -hydrate. The use of a copper-containing catalyst has the advantage of neutralizing and blocking any microbiological pathogens that may be present in the raw material, thus improving the shelf life of the product. At the same time, the use of hydrogen peroxide also neutralizes microbiological pathogens, so the use of copper-containing catalysts is not necessarily needed.

Extraction and thermal cracking are accompanied by strong foaming, which must be taken into account when sizing the extraction equipment. It is advisable to choose the size of the extraction equipment so that it is at least twice as large as the volume of the sample. As the temperature rises, the degree of foaming increases continuously. The strongest foaming is experienced between 65 and 100 °C. Cracking is carried out during boiling until foaming stops and only a simple boiling is observed. After boiling, separation is carried out, for example by centrifugation.

The separated liquid phase contains fulvic acid, which may be one of the products of the process. The pH value of the resulting fulvic acid solution is typically about 1.9 to 2.5.

The solid phase remaining after the first extraction (hereinafter: "Extraction I sludge") also contains precipitated humic acids and insoluble humin matter, as well as inorganic, water-insoluble salts and silica minerals; from this fraction, preferably humic acids are recovered later on. If the extraction of humic acid is not a goal, then the solid fraction can be used as a useful by-product in agriculture, e.g. as soil improver, animal feed additive, soil water content increasing (water binding) material. Fulvic acid refining

The bound fulvic acid fraction extracted during thermal cracking by flooding keeps a small amount of calcium and magnesium ions in bonded form. Fulvate salts of alkaline earth metals are water-insoluble compounds, so they crystallize and precipitate during a slow natural process from the fulvic acid solution obtained in the previous step.

If we want to avoid this phenomenon (e.g. if we want to achieve a very pure quality, or if the presence of calcium or magnesium fulvate would be disturbing during further use), we can refine the fulvic acid solution obtained in the previous step in the following way. The fulvic acid solution is frozen, i.e. cooled to a temperature below 0 °C, and then allowed to thaw. The solution can also be left to stand in a frozen state, but this is not absolutely necessary, because the mentioned salts precipitate by the time the solution freezes.

Sedimentation can also be used as an alternative to freezing, but in this case, the solution must be allowed to stand for 72-96 hours at room temperature. The time required for resting can be reduced by cooling the mixture.

A plate-like, yellowish -brown, butter-colored layer forms at the bottom of the solution, from which the pure (transparent) fulvic acid solution is separated, e.g. by filtration or centrifugation.

The fulvic acid solution obtained in this way may be one of the end products of the process, it can be used alone as a solution or it can be further formulated, e.g. can be encapsulated and added to beverages. The solution can also be dried to produce solid fulvic acid.

In the resulting fulvic acid solution, fulvic acid is essentially free of counterions, thus it has outstanding activity, e.g. in terms of heavy metal binding capacity and antioxidant capacity.

Drying of fulvic acid

If the fulvic acid is not intended to be used as a solution, the solution obtained in the above step can be simply dried in a known manner. For example, the finished refined fulvic acid solution is dried to 90- 95% dry matter at about 50-80 °C, preferably at about 70 °C, using a tray dryer. Dried fulvic acid forms sweet-smelling, blackish-red, easily breakable, crumbly, shiny crystals. It dissolves perfectly in water without leaving any residue. The dry, crystalline fulvic acid can also be a valuable product of the process, it can be used e.g. as a food supplement or as an active ingredient of food supplements or pharmaceutical compositions, or as a special food-grade or pharmaceutical chelating agent.

Raw and bound humic acid extraction - thermal cracking II

After extraction of the bound fulvic acid content, the brown humic acid fraction is extracted from the remaining Extraction I sludge (which contains precipitated humic acids and insoluble humin matter). Extraction I sludge is extracted with an alkaline solution. A solution of e.g. NaOH, KOH, or even NaHCCh. KHCO3 or a mixture of these solutions may be used. The extracting solution is poured in small portions into the Extraction I sludge with continuous stirring. The alkaline solution is added until the pH of the extraction mixture is higher than 12,5.

After that, a catalyst, e.g. disodium hydrogen phosphate is added, and then the extraction is carried out with continuous stirring at about 50-80 °C, preferably at about 60-70 °C, typically for 1-3, for example about 1 hour.

After the extraction time has elapsed, hydrogen peroxide solution is added to the extraction mixture, adding the total amount in one portion. If, for example, a solution of hydrogen peroxide at 30% is used, the amount is about 0,1 to 0,15 times by weight of the sediment, for example about 0,12 times by weight. A person skilled in the art can determine the optimal peroxide: sediment dry matter ratio.

Thermal cracking II is also associated with strong foaming, so care should be taken to avoid run-out. After the addition of the hydrogen peroxide solution, the solution is heated slowly and steadily to boiling (about 100°C) and boiled until the foam disappears and only boiling is observed, usually for about 0.5 to 2 hours, for example about 1 hour.

After the extraction, separation is carried out, e.g. by centrifugation. The sediment fraction is a mixture of the insoluble humin matter fraction and precipitates of various minerals (e.g. phosphate, hydroxide and/or carbonate precipitates). This fraction is separated and is not used in the following. This fraction is a useful by-product of the process, which may form the basis of soil conditioning products or can be used to increase the organic and humic substance content of flower soil.

The pure solution contains potassium- and sodium -bound humic acids in the form of humates. This is a raw product of the process, which is expediently further refined.

Refining of humic acid solution (Na-K-humate solution), odour and sulphur removal

The humic acid solution and potassium and sodium humates naturally contain molecularly bound sulphur compounds. Organic sulphur is not strongly bound to the chelate structure of humic acid, so humate solutions form an unpleasant odour when they are left to stand and rest due to the formation and release of hydrogen sulphide and sulphur oxides. During the refining process, humic acid molecules that are in the open quinone state in the alkaline medium and the humate chelates are disrupted. This can be done by using any food-grade acid, such as citric acid, malic acid, tartaric acid, succinic acid, acetic acid, lactic acid or a mixture of these. The pH value is reduced below about 2.0 by adding the acid. As a result, the rings in the humic acid close, and the humic acids precipitate out of the solution. A part of this process is that sulphur compounds that are not strongly bound are detached from the molecule and go into solution. The precipitated humic acid is then continuously stirred e.g. for about 1 hour, then separated from the liquid phase, e.g. by centrifugation.

After separation, the acid solution containing the sulphur compounds is no longer used. It is a useful by-product of the process, which can be used as an additive for horticultural irrigation water and as an additive for soil conditioning preparations.

The precipitated humic acids also lose their potassium and sodium content (in the form of potassium citrate, sodium citrate or salts formed with the other food-grade acids listed above) in addition to sulphur. Precipitated humic acids are not water-soluble compounds, but they can also be considered as a finished product. If the aim is to make a completely salt-free humic acid finished product, this fraction can simply be dried as described later.

Humic acid free of counterions has outstanding activity, e.g. in terms of heavy metal binding capacity, antioxidant capacity and liver detoxification effect.

It is noted that since the starting material for the extraction and cracking of humic acid is a purified and, during the fillvic acid extraction further "pretreated" material, the resulting humic acid is of outstanding purity.

The refining step is an optional step during the process, on the one hand, it depends on the properties of the solution obtained at the end of the previous thermal cracking step, whether it is advisable to perform it, and it also depends on how the solution is further processed. If the solution obtained at the end of the cracking step is immediately dried into a powder, most of the sulphur compounds are removed during drying, so this step is not necessary. If the resulting liquid is considered a product, then it is typically advisable to refine the raw product as described above.

Preparation of humate solution - preparation of water-soluble humic acid

If it is desired to bring the humic acid into a water-soluble form after the refining process, this can be done by adding an alkaline solution.

Solutions of, for example, NaOH, KOH, sodium hydrogen carbonate or potassium hydrogen carbonate can be used. The concentration of the alkaline solution is usually about 1-4 M, typically about 2 M. The alkaline solution is added to the precipitated humic acid fraction in such an amount that the pH value is adjusted to about 10.5-11.5 and the color of the precipitated humic acid changes from brownish to dark black and dissolves completely. The sodium or potassium humate solution is then stirred, usually for about 1 hour.

Water soluble amino humates can also be prepared. These are also salt-free humic acids, but still retain their water solubility. For this purpose, an aqueous solution of amino acids with basic side chains, e.g. 15% L-arginine solution or 20% L-lysine solution, or a combination of them, can be added to the precipitated humic acid fraction. The amino acid solutions are also used in such an amount that the pH value of the sludge or solution made from the humic acid is adjusted to a pH value of the between 10.5 and 11.5. Stirring is then also carried out, usually for about 1 hour.

The resulting humate (e.g. potassium humate or sodium humate, or argino humate, lysino humate) solutions can be considered as finished products and are of food-grade quality.

Drying of humic acid or humates, preparation of solid humic acid or humates

The prepared refined humic acid fraction or humate solution (Na-humate, K-humate, Argino-humate, Lysino-humate) can be dried in a known manner. For example, it is dried using a tray dryer at about 50-80 °C, preferably at about 70 °C, to 90-95% dry matter.

The dried humates form shiny, dark black colored, easily breakable and crumbly crystals with a characteristic smell. They dissolve well in water.

The dried, salt-free, pure humic acid is a dark brown (with a brick-red hue), non-crystalline, porous material, insoluble in water.

The products have favorable organoleptic properties (pleasant taste, odour). They can be used on their own or as an additive, or further formulated as an active ingredient in dietary supplements, cosmetic or pharmaceutical preparations, and also as food coloring (give a black, brown color).

The products obtained by the process according to the invention are of food-grade quality. It is the amount of heavy metals in the starting material and the microbiological purity that can cause problems in terms of food-grade quality. During the process according to the invention, the amount of heavy metals in the starting material is greatly reduced by the initial acid digestion; in the case of peat, xyloid lignite and leonardite used as starting material, the amount of heavy metals can be reduced below the limit values as a result of the acid digestion. Microbiological purity is ensured by the use of hydrogen peroxide and, optionally, a copper-containing catalyst during the first thermal cracking. Reagents not accepted in the food industry are not used in the process, so possible residues of reagents do not cause problems either. EXAMPLES

EXAMPLE 1: Preparation of fulvic acid and humic acid from natural peat from Alsopahok

Step 1: acid pretreatment

To the natural peat from Alsopahok, ground to the appropriate particle size ("sample"), a digesting acid mixture and distilled water are added in the quantities indicated below.

The digesting acid mixture is prepared by dissolving 67.5 g of tartaric acid, 35.4 g of succinic acid and 59.9 g of citric acid in 837.3 g of water.

After weighing the components, the mixture is stirred with a magnetic stirrer to obtain a completely homogeneous, smooth suspension. The solution is then boiled for 2 hours with stirring.

After the boiling time, the digested sample is centrifuged while still hot. The supernatant is set aside (it is a usable by-product of the process) and we continue the process with the sediment.

Step 2: Bonded Fulvic acid extraction - thermal cracking I

The following materials are used in the quantities indicated below.

Water is added to the sediment obtained in step 1, then copper(II) sulphate -5 -hydrate catalyst is added to the mixture with continuous stirring. To the homogeneously mixed suspension, the total amount of 30% H2O2 is then added and the suspension is slowly but continuously heated to 100 °C. As the temperature rises, the foaming rate increases steadily. The strongest foaming occurs between 65- 100 °C. Cracking is continued at 100 °C until foaming stops and only simple boiling is observed. After boiling, centrifugal separation is carried out.

Step 3: Fulvic acid refining

The fulvic acid solution obtained in step 2 is frozen to -24 °C and allowed to thaw at room temperature. A plate-like, yellowish-brown, butter-coloured layer forms at the bottom of the solution, from which the clear fulvic acid solution is separated by fdtration. The following parameters of the refined fulvic acid are recorded and the qualification is carried out.

Taking into account the fulvic acid content of the solution, the fulvic acid yield is 43%. Step 4: Fulvic acid drying

The refined fulvic acid solution obtained in step 3 is dried in a tray dryer at 70 °C to 90-95% dry matter. The dried fulvic acid forms sweet-smelling, blackish-red, easily breakable, crumbly, shiny crystals. Perfectly soluble in water without leaving any residue. Step 5: Raw and bound Humic acid extraction - thermal cracking II

The following materials, quantities and parameters are used.

The alkaline solution is prepared by mixing 40.0 g of sodium hydroxide, 52 g of potassium hydroxide and 904.0 g of water. After weighing the ingredients, the alkaline solution is boiled for half an hour with continuous stirring.

The alkali solution is added to the sludge obtained in step 2 in small portions, with continuous stirring. The required amount of disodium hydrogen phosphate is added, and then the extraction is carried out for 1 hour, with continuous stirring, at 60-70 °C. After 1 hour, the full amount of the specified amount of the 30% hydrogen peroxide solution is added to the extraction mixture. Thermal cracking involves strong foaming, so care must be taken to avoid run-out. After addition of the hydrogen peroxide solution, the mixture is slowly and steadily heated to 100 °C and boiled for 1 hour.

After the extraction, the solution is centrifugated. The sediment fraction is separated and not used in the following. The parameters of the solution (humate fraction) are recorded.

Step 6: Refining of humic acid solution (Na-K-humate solution), odour and sulphur removal

The following materials, quantities and parameters are used. The pH value of the humate solution obtained in step 5 was adjusted to 1.8 by adding citric acid. The mixture containing the precipitated humic acid is then continuously stirred for 1 hour and then separated from the liquid phase with a centrifuge.

The sulphur-containing citric acid solution is not used in the following. The precipitated humic acid fraction is carried on to the next step.

Step 7: Preparation of Na-humate solution - preparation of water-soluble humic acid

The following materials, quantities and parameters are used.

The alkaline solution is added to the humic acid obtained in step 6. The precipitated humic acid changes from brownish to dark black and completely dissolves. After that, the Na humate solution is stirred for 1 hour.

Step 8: Drying of Na humate

The refined Na humate solution obtained in step 7 is dried using a tray dryer at 70 °C to 90-95% dry matter. Dried Na-humate forms shiny, dark black colored, easily breakable and crumbly crystals with a characteristic smell. It dissolves well in water. EXAMPLE 2: Preparation of counterion-free humic acid from natural peat from Alsopahok

Steps 1-6.

We proceed as described in steps 1 -6 of Example 1.

Step 7: Drying of humic acid The humic acid obtained in step 6 is dried using a tray dryer at 70 °C to 90-95% dry matter. Dried humic acid is a brown, non-crystalline porous material with a characteristic smell. It does not dissolve in water.

According to Example 2, the yield of counterion -free humic acid from the starting peat is 33%. EXAMPLE 3: Preparation of argino humate from natural peat from Alsopahok

Steps 1-6.

We proceed as described in steps 1 -6 of Example 1.

Step 7: Preparation of argino humate

We proceed as described in step 7 of Example 1, using the following materials, quantities and parameters.

Step 8: Drying of agino humate

We proceed as described in step 8 of Example 1, using the following materials, quantities and parameters.

EXAMPLE 4: Preparation of fulvic acid and humic acid from leonardite from Dudar

We proceed as described in Example 1 with the exception that leonardite from Dudar (dudarite) is used as raw material. In each step, the materials and parameters given in the tables are used, and the operations described in the corresponding steps of Example 1 are carried out.

Step 1: acid pretreatment

Step 2: Bonded Fulvic acid extraction - thermal cracking I Step 3: Fulvic acid refining

The fulvic acid yield is 13,4% from the leonardite starting material

Step 4: Fulvic acid drying Step 5: Raw and bound Humic acid extraction - thermal cracking II

The parameters of the solution (humate fraction) obtained after alkaline extraction and thermal cracking are the following: Step 6: Refining of humic acid solution (Na-K-humate solution), odour and sulphur removal

The following materials are obtained:

Step 7: Preparation of Na-humate solution - preparation of water-soluble humic acid

Step 8: Drying of Na humate

Determination of contaminant elements

In the following we describe the heavy metal contaminants important from the point of view of food safety that are present in the starting material of examples 1 and 4 and the products produced from them. For comparison, in the case of dudarite, we also provide these data for the product produced without an acid pretreatment step. Heavy metals were determined by inductively coupled plasma spectrometry, using an ICP-OES Thermo Elemental iCAP 7400 Duo View instrument, according to the MSZ 21470-50:2006 standard.

Table 2: Contaminant elements of raw peat and fulvic acid and humic acid produced from it

The data confinn that the peat raw material is very clean, the pollutants are below the food industry limit (note that there is no prescribed limit for aluminum and nickel), and the amount of polluting elements in the products has further decreased.

As a result of the refining steps, the sulphur content in the products has also been significantly reduced compared to the starting material.

Table 3: Contaminant elements of leonardite and humic acid produced from it

In order to demonstrate the effect, of acid digestion, for comparison, Na humate was produced analogously to Example 4, but omitting step 1.

The data show that the lead content of the starting dudarite is higher than allowed. There are no specific regulations for aluminum and nickel, but there is a significant amount of them in dudarite. The amount of contaminant elements is somewhat reduced during the process (even without the acid diges tion step), but the acid pretreatment significantly reduces the amount of contaminants.

The results therefore demonstrate that food-grade humic acid can be produced from leonardite using the process according to the invention, despite the fact that the leonardite used as starting material contains heavy metal contaminants in concentrations higher than the limits allowed in food industry.

EXAMPLE 5: Preparation of fulvic add from peat - examination of the effect of the temperature applied during acid digestion and thermal cracking on the yield of fulvic add

Two series of experiments were carried out.

In one series, acid pretreatment was performed as described in step 1 of example 1, in the other (comparative) series, acid pretreatment was not performed.

Afterwards, thermal cracking was performed according to step 2 of example 1, but with the difference that instead of boiling, we worked at different temperatures in the te mperature range of 10-100°C.

At the end of cracking, the fulvic acid content of the solution was determined and the fulvic acid yield was calculated.

Figure 2 shows the fulvic acid yield as a function of temperature. The white column shows the fulvic acid yield obtained without acid extraction, the black column after thermal cracking after acid extraction.

The results prove that acid digestion has a positive effect on fulvic acid yield.

The highest yield was achieved when the mixture was heated to boiling and boiled during cracking.

EXAMPLE 6: Preparation of fulvic acid from leonardite - examination of the effect of the temperature applied during acid digestion and thermal cracking on the yield of fulvic acid

The series of experiments described in Example 5 were also carried out with leonardite starting material.

The results are shown in Figure 3.

The results confinn that acid digestion lias an even greater impact on yields in the case of leonardite. This can presumably be explained by the fact that it is a geologically older, more humified material, and also that many mineral elements are attached to binding sites, which, if left there, block the reaction of the peroxide and the humic substance (the minerals react with the peroxide, forming metal oxides) during cracking. However, if they are detached with acid, an "opening" space is provided, which manifests in the yield. Due to the nature of the raw material (it is an older, more carbonized material, so its fulvic acid content is lower, but its humic acid content is higher than that of peat), the overall yields are, as expected, lower than the yields obtainable from peat (example 5).

EXAMPLE 7 (comparative): Preparation of fulvic acid from natural peat from Alsopahok by "gradual" thermal cracking

We carried out a series of experiments in which acid pre-treatment was performed as described in step 1 of example 1, but thermal cracking was carried out according to the state of the art, with gradual addition of the oxidizing agent as described below. The results are presented in Figure 4.

Water is added to the sediment obtained in step 1, so that the dry matter content of the mixture is 10%, 20% or 30%, respectively, and then copper(II) sulphate 5 -hydrate catalyst is added to the mixture with continuous stirring. The homogeneously mixed suspension was heated to 60°C, after which hydrogen peroxide was added in 5 g portions. The temperature rose continuously and reached about 100 °C where, in Figure 4, the peaks can be seen in the curves assigned to the given % dry matter content. The curves show that the addition of peroxide increased the yield of fulvic acid up to a point, but after that the yields started to decrease due to excessive decomposition.

At the maximum fulvic acid yield, the fulvic acid content of the fulvic acid solution was about 3-4.5%, and the fulvic acid yield was about 6.5-9.5% based on the starting material.

By comparing this with the 43% yield of fulvic acid obtained in Example 1, it was demonstrated that the thermal cracking performed with the "flooding" method according to the invention significantly increases the yield of fulvic acid.

We also note that in the case of the optimal hydrogen peroxide amounts seen in Figure 4, the ratio of peat dry matter to peroxide is about 1: 1. We used the same ratio in our initial experiments with the "flooding" method, but we found that this amount oxidized almost all the organic matter into water and carbon dioxide, practically leaving only water and sand.

In order to determine the optimal amount of peroxide for the process according to the invention, we performed a separate series of experiments, which are presented below.

EXAMPLE 8: Preparation of fulvic acid from natural peat from Alsopahok by thermal cracking according to the invention, determination of the optimal amount of peroxide

We carried out a series of experiments in which acid pretreatment was performed as described in step 1 of example 1, then thermal cracking was carried out as described in step 2 of example 1, with the difference that the 30% hydrogen peroxide solution was used in different amounts.

The results are presented in Figure 5, where the fulvic acid content of the resulting fulvic acid solution is plotted as a function of the mass of the 30% hydrogen peroxide solution used. In the case of 5-40 g of 30% hydrogen peroxide solution shown in the figure, the ratio of peat dry matter and peroxide is about 1:0.04 - 1:0.34.

The optimal ratio of peat dry matter: peroxide is about 1:0.2, which means that, compared to the gradual dosing method, the use of about a fifth amount of hydrogen peroxide is optimal. The chemical requirement of the process is therefore significantly reduced.

In summary, the process according to the invention has the following advantages:

- food-grade fulvic acid and humic acid can be produced even if the heavy metal contaminants in the starting material are above the permitted limit,

- significantly increased yield compared to state-of-the-art procedures,

- there is no need for chemicals that need to be disposed of afterwards,

- less need for chemicals (peroxide),

- no unusable by-products are produced.

INDUSTRIAL APPLICABILITY OF THE INVENTION

The process according to the invention can be used to produce fulvic acid and/or humic acid (in solid or solution form, in versions containing counterions or without counterions) in an economical, environmentally friendly way, with outstanding quality, which can be used e.g. as a dietary supplement or as an active ingredient in dietary supplements or pharmaceutical preparations, as well as as a food coloring or as a cosmetic ingredient. The by-products created during the process can be used in agriculture (e.g. as additives to soil conditioners and foliar fertilizers).