RU2463282C1 - Method of producing water-soluble humic acids - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to agriculture. The method of producing water-soluble humic acids from caustobioliths of the coal family, which involves exposing caustobioliths to a potassium or sodium hydroxide solution with concentration of 2.0-4.0 wt %, separating the liquid phase, treating the liquid phase with acid, followed by separation in a centrifugal force field and separating the heavy phase, treating the obtained heavy phase with a hydroxide of alkali or alkali-earth metals until obtaining a ready product, wherein the caustobioliths are subjected to attrition with a potassium or sodium hydroxide solution to obtain particles with size of 250-5 mcm in amount of not less than 90 wt %, wherein the heavy phase is also subjected to attrition with a hydroxide of an alkali or alkali-earth metal until achieving pH 3.5-5.0.

EFFECT: invention increases output of humic acids while maintaining their natural state and cutting the duration of the process.

5 cl, 6 dwg, 5 tbl, 18 ex

Description

The invention relates to the production of humic substances, in particular, to the production of water-soluble humic acids from coal series caustobioliths, i.e. from peat, coal, sapropel, etc., which can be used to solve important environmental and agricultural problems, namely for detoxification of heavy metals in industrial and household waste, soil cleaning, reclamation of disturbed lands, as well as to restore and increase soil fertility.

Under natural conditions, humic substances are formed in the process of oxidative destruction of plant residues under the influence of microorganisms and atmospheric oxygen. This is a natural product, which is an essential component that ensures the existence of modern life forms, a necessary component of all metabolic processes in the biosphere. Humic acids, forming the basis of soil humus and determining soil fertility, also perform accumulating functions, that is, they accumulate the most important plant nutrition elements in the soil, promote the decomposition of natural and synthetic materials, protect microflora and plants from adverse factors and have a stimulating effect on their growth and development. In addition, they can form stable water-insoluble compounds with heavy metal ions and many other dangerous environmental pollutants. However, in their initial natural state, humic acids have low activity due to low hydration and dispersion, blocking their active centers by various components, including mineral ones, therefore, the task of obtaining humic acids with a high degree of activity, namely, water-soluble, is currently relevant. which are an excellent detoxifier, forming strong complexes with heavy metal ions and organic toxins, which in combination lose their bioavailability. (I.V. Perminova, D.Sc., Chemistry and Life, No. 1, 2008).

A known method of producing water-soluble humic acids by oxidation of organic raw materials with an aqueous solution of a mixture of acids by heating. As an aqueous solution of a mixture of acids using an aqueous solution of mineral and organic acids containing 3-10% wt. nitrogen and 3-10% wt. acetic acid. The process is carried out in a reactor equipped with a chopper-heater with recirculation with a recirculation coefficient of the reaction mixture in the range of 1-10 at atmospheric pressure, the ratio of oxidizer: organic raw materials (2.0-5.0): 1 and the reaction time 10-30 minutes, followed by separation of the mixture into solid and liquid phases. To obtain water-soluble humic acids, the solid phase containing humic acids is treated with alkali or ammonia water or caustic soda until a pH of 6.0-7.0 is reached, and the liquid phase after regeneration is returned to the process (RF patent No. 2281930, C05F 11/02 , publ. 02/10/2006).

The disadvantage of this method is the insufficiently high yield of humic acids, as well as the presence of fulvic acids in the final product, since in the process of acid extraction of fulvic acids associated with humic acids present in the feed, acid extraction is not extracted. Moreover, as you know, the effect of acid is destructive for humic acids, and therefore the known method does not allow to obtain humic acids in a state close to natural (Rakovsky V.E., Pigulevskaya L.V., Chemistry and Genesis of Peat, M., 1978). In addition, the process is cyclical in nature, while the time spent on the cycle takes considerable time.

A known method of producing water-soluble humic acids, according to which a mixture is prepared consisting of coal and potassium and / or sodium carbonates in dry form, in a ratio of 1: (0.8-1.2), and subjected to dispersion. The resulting product is incubated for a day. The result is a finished product, the soluble content of which is 87.0-94.5% wt. (Pat. RF No. 2036190, C05F 11/02, publ. 08.12.92).

Despite the rather high yield of humic acids, in the final product they are mixed with coal, where their amount does not exceed 40% wt. The disadvantage of this method is also the significant duration of the process due to its cyclical nature.

The closest in technical essence is the method of obtaining water-soluble humic acids by processing pre-crushed feedstock, which is used as a series of coal caustobiolites - peat, coal, shale, with an aqueous solution of mixtures of potassium hydroxide or sodium and potassium or sodium carbonate. The concentration of hydroxides is maintained at 0.5-4.0% by weight, and the concentration of carbonates is 3.0-8.0% by weight. The remainder of peat or coal is separated by filtration, and the filtrate is treated with acid to a pH of 2-4. The resulting pulp is centrifuged, and the thickened product is treated with potassium hydroxide to a pH of 7-8 (RF patent No. 21116632, C05F 11/02, publ. 09/10/98).

This method uses the technology of “soft” extraction of humic substances, which allows one to obtain humic acids, the composition of which is close to their natural state and does not contain tar and mineral impurities, however, the yield of humic acids is quite low and, as calculations show, is 75.7% wt. . The disadvantage of this method is also the significant duration of the process, since the extraction of humic acids from caustobiolites by mixing them with potassium or sodium hydroxide requires considerable time.

The problem to which the invention is directed, is to increase the yield of humic acids while maintaining their natural state and reducing the time of the process.

The problem is solved in that in a method for producing water-soluble humic acids from coal series caustobioliths, including exposure to coal series caustobioliths with a solution of potassium or sodium hydroxide at a concentration of 2.0-4.0% by weight, separating the liquid phase and treating it with acid, followed by separation in the field of centrifugal forces and treatment of the obtained heavy phase with alkali or alkaline earth metal hydroxide to obtain the finished product, the caustobiolites are abraded with a solution of potassium or sodium hydroxide with obtaining particles with a size of 250-5 microns in an amount of not less than 90% wt., and the heavy phase is also subjected to abrasion with hydroxide of an alkali or alkaline earth metal until a pH of 3.5-5.0 is reached.

At the same time, abrasion is carried out in a mill mill.

In addition, caustobiolites and a solution of potassium or sodium hydroxide are taken in a mass ratio of 1: (0.5-2.0).

In addition, calcium hydroxide is used as the alkaline earth metal hydroxide.

In addition, a decanter is used to separate the phases in the field of centrifugal forces.

Abrasion of coal series caustobioliths with a solution of potassium or sodium hydroxide to obtain particles with a size of 250-5 microns in an amount of not less than 90% wt. allows to increase the yield of humic acids due to an increase in the efficiency of mass transfer processes, caused not only by an increase in the surface contact area of the particles with the solution during grinding, but also by the sliding effect that is characteristic of the abrasion process under pressure of the particles in contact with the solution during ultrafine grinding. As you know, the abrasion process is carried out in devices whose working bodies are surfaces moving relative to each other, the action of which is simultaneously shear and crush. This effect contributes to a faster interaction of a solution of potassium or sodium hydroxide not only with the surface of the crushed particles of caustobiolites, but also its penetration into their pores, which increases the contact area and, accordingly, the amount of humic acids extracted from them, and also accelerates the process of their extraction. In this case, the use of a solution of potassium or sodium hydroxide concentration of 2.0-4.0% wt. allows you to save the natural composition of humic acids almost unchanged, since such a concentration eliminates the destruction of humic acid molecules (Orlov D.S. Humic acids of soils and the general theory of humification. - M.: Moscow State University, 1991).

The abrasion of the heavy phase with an alkali metal hydroxide to reach a pH of 3.5-5.0 helps to reduce the time for the process of obtaining humic acids due to the fact that due to the increased mass transfer during abrasion, the maximum completeness of chemical reactions is ensured, and therefore the possibility of using only the necessary calculated amount of alkali metal hydroxide solution. This allows you to get the most condensed finished product and thereby reduce the time of the process by reducing the processed volumes. The preparation of the proposed method of water-soluble humic acids with a pH of 3.5-5.0, as shown by experiments, makes it possible to ensure their high reactivity with a high yield of humic acids.

The use of a mill mill for abrasion makes it possible to provide the most optimal conditions for the physicochemical process of interaction between the particles of the material and the solution - high fineness, effective mass transfer, and accordingly, the efficiency and acceleration of extraction, as well as an increase in the yield of humic acids. In addition, the mill mill is characterized by high productivity, which allows to accelerate the process of obtaining water-soluble humic acids. At the same time, the use of a millstone makes it possible to increase the technological effectiveness of the process, since the characteristics of this device make it possible to ensure the continuity of the process of obtaining water-soluble humic acids.

Carrying out the abrasion of coal series caustobioliths and a solution of potassium or sodium hydroxide with a mass ratio of 1: (0.5-2.0) allows the extraction of humic acids with the minimum allowable losses and, accordingly, with their maximum yield.

Conducting phase separation in the decanter helps to accelerate the process of obtaining water-soluble humic acids by ensuring a continuous process of phase separation in the decanter.

The proposed method is illustrated by the following drawing and graphs.

Figure 1 shows a schematic diagram of an installation for implementing a method for producing water-soluble humic acids; figure 2 presents a graph of the dependence of the yield of humic acid on the concentration of a solution of potassium hydroxide; figure 3 shows a graph of the dependence of the loss of humic acid from the mass ratio of brown coal: potassium hydroxide and the time of phase separation in the field of centrifugal forces; figure 4 shows a graph of changes in the content of heavy metals in sewage sludge during their treatment with humic acid obtained by the proposed method; figure 5 shows a graph of changes in the content of zinc in wastewater when it is treated with humic acid obtained by the proposed method; figure 6 shows a graph of changes in the iron content in wastewater when it is treated with humic acid obtained by the proposed method.

The proposed method is carried out on the installation, a diagram of which is shown in figure 1.

The installation comprises a hopper 1 and a tank 2, the outputs of which are connected to a millstone for abrasion of caustobiolites 3. The outlet of a mill mill 3 is connected to a decanter 4, the liquid phase outlet of which is connected to a precipitation tank 5, and the solid phase outlet is connected to a briquetting line (not shown) . The output of the acid tank 6 is connected to the input of the precipitation tank 5, and the output of the precipitation tank 5 is connected to the decanter 7. The output of the heavy phase of decanter 7 is connected to a mill mill to abrade the heavy phase 8 with alkali or alkaline earth metal hydroxide, and the output of the liquid phase is connected to the line return (not shown). The mill mill 8 is connected to a tank for a solution of alkali metal hydroxide 9.

The method is as follows.

Pre-crushed to particles 1-10 mm in size, a caustobiolite of a coal row, for example, brown coal, is fed from a hopper 1 (Fig. 1) to a mill mill 3. At the same time, in the mass ratio 1: (0.5-2.0) of capacity 2 serves a solution of potassium or sodium hydroxide concentration of 2.0-4.0% wt. Abrasion is carried out in a mill mill with a gap between the disks (millstones) of 0.1 mm (with a smaller gap jamming occurs) to obtain particles with a size of 250-5 microns in an amount of not less than 90% wt. The resulting pulp from a mill mill 3 enters decanter 4, where during centrifugal acceleration the separation of solid (coal) and liquid (solution of humic substances) phases occurs. The solid phase is sent for briquetting, and the liquid phase (solution of humic substances) is sent to sedimentation tank 5, where the solution is acidified by adding acid from tank 6 to a pH of 2.1-2.5 to form a pulp - coagulated humic acid. The pulp formed in the tank 5 is fed to the decanter 7, where the separation of the heavy phase — coagulated humic acid — takes place. The heavy phase is fed to the mill mill 8, where at the same time in a mass ratio to the heavy phase 1: (0.1-0.2) from the tank 9 a solution of alkali or alkaline earth metal hydroxide with a concentration of 2-4% by weight is fed, and they are rubbed to achieve a pH of 3.2-5.0. The result is a finished product - water-soluble humic acids. The liquid phase recovered in decanter 7 is made alkaline and returned to the process.

Example 1

Pre-crushed to particles with a size of 1-10 mm, brown coal from hopper 1 (Fig. 1) was fed into a mill mill 3. At the same time, a potassium hydroxide solution of 4.0% wt was supplied from a tank 2 in a mass ratio of 1: 2. Abrasion was carried out in a mill mill with a gap between the disks (millstones) of 0.1 mm to obtain particles with a size of 250-5 microns in an amount of 93.49% wt. (fractional composition of brown coal after abrasion is shown in table 1). The resulting pulp from a mill mill 3 was fed to decanter 4, where during centrifugal acceleration of 1500 g for 3 min there was a separation of solid (coal) and liquid (solution of humic substances) phases. The solid phase was sent for briquetting, and the liquid (humic substances solution) was sent to sedimentation tank 5, where the solution was added by sulfuric acid with a concentration of 10.0% wt. from tank 6 was acidified to pH 2.1-2.5 with the formation of pulp - coagulated humic acid. The pulp formed in tank 5 was fed to decanter 7, where the release of the heavy phase — coagulated humic acid — took place. The heavy phase was fed to mill mill 8, where a potassium hydroxide solution of 4.0% by weight was fed from tank 9 at the same time in a mass ratio to heavy phase 1: 0.2, and they were rubbed until pH 4.5 was reached. The result was a finished product — water-soluble humic acids, the yield of which was 97.91% wt. The liquid phase isolated in decanter 7 after alkalization was returned to the process — to tank 2.

Example 2. The method was carried out analogously to example 1, but brown coal was abraded to a particle size of 250-5 μm in the amount of 63.66% wt., While the yield of humic acids was significantly reduced and amounted to 68.60% wt. The result showed a significant decrease in the yield of humic acids during enlargement of the fractional composition of coal during abrasion (table 1), since the area of mass transfer decreases.

Example 3. The method was carried out analogously to example 1, but the heavy phase was abraded with calcium hydroxide. The yield of humic acids was 97.91% wt.

Examples 4-9. The method was carried out analogously to example 1, but potassium hydroxide solutions of various concentrations were used.

The result showed a significant decrease in the yield of humic acids with a decrease in the concentration of potassium hydroxide below 2.0% wt. The results of the method according to examples 4-9 are shown in table 2 and in the graph of figure 2.

Examples 10-15. The method was carried out analogously to example 1, but used various mass ratios of brown coal: potassium hydroxide solution and the phase separation time in the field of centrifugal forces. The results are presented in table 3 and in the graph (figure 3). As can be seen from table 3 and figure 3, a decrease in the amount of solution less than 0.5 of the amount of coal leads to a significant increase in the loss of humic acids due to their residual content in brown coal, and an increase in the amount of solution over 2.0 does not lead to a significant decrease losses.

Thus, the results of the method according to examples 10-15 confirm that the optimal mass ratio of brown coal to a solution of alkali metal hydroxide, which ensures the maximum yield of humic acids, is 1: (0.5-2.0).

Table 1 The dependence of the yield of humic acids on the fractional composition of brown coal during its abrasion Example No. The content of fractions in the pulp,% wt. The output of humic acids,% wt. More than 250 microns from 250 to 100 microns from 100 to 7 microns from 7 to 5 microns less than 5 microns one 5.73 33.12 13.49 46.88 0.78 97.91 2 36.34 47.91 5.31 10.12 0.32 68.60

table 2 The dependence of the yield of humic acids on the concentration of potassium hydroxide solution No. of examples The concentration of potassium hydroxide solution,% wt. The output of humic acids,% wt. four 4.0 98.2 5 3,5 97.6 6 3.0 85.6 7 2.5 81.2 8 2.0 77.3 9 1,5 41.6

Table 3 The influence of the mass ratio of brown coal: potassium hydroxide solution on the loss of humic acids during phase separation in the field of centrifugal forces No. of examples mass ratio of brown coal: potassium hydroxide solution loss of humic acids in brown coal after separation of the aqueous phase as a function of time (% wt.) 2 minutes 3 min 4 min 5 minutes 10 1: 2.0 0.44 0.33 0.31 0.29 eleven 1: 1,5 0.79 0.59 0.55 0.51 12 1: 1,0 1.78 1.33 1.24 1.15 13 1: 0.5 7.13 5.30 4.99 4.63 fourteen 1: 0.3 19.80 14.85 13.86 12.87 fifteen 1: 0.2 44.55 33.41 31.19 28.96

Thus, in comparison with the prototype method, the proposed method allows to increase the yield of water-soluble humic acids to 77.3-98.2% wt. (in the prototype - 75.7% wt.).

In addition, the proposed method allows to reduce the time of the process of obtaining water-soluble humic acids by improving the mass transfer and, accordingly, accelerating the extraction of humic acids, as well as by reducing the processed volumes during abrasion of the heavy phase with alkali or alkaline earth metal hydroxide.

The use of a millstone and a decanter in the implementation of the proposed method allows to provide the most optimal conditions for the physicochemical process of interaction of the particles of the material and the solution - high fineness, effective mass transfer and, accordingly, extraction efficiency, increased yield of humic acids and reduced process time. In addition, the reduction of the process time is affected by the high productivity of millstones. In particular, millstones of the CO series can produce particles up to 5 microns with a productivity of 100-300 kg / h. The use of a millstone and decanter in the implementation of the proposed method also allows to ensure the continuity of the process and thereby increase its manufacturability.

To confirm the properties of water-soluble humic acids obtained by the proposed method, experiments were carried out (examples 16-18) for the detoxification of wastewater and sewage sludge.

Example 16

Sewage sludge (WWS) with a moisture content of 70% was treated with an aqueous solution of humic acids obtained according to example 1, with a mass ratio of WWS: humic acids - 1: 0.001 (dry matter). The results of the experiment are shown in table 4 and in the graphs (figure 4, 5).

Table 4 The results of the treatment of WWS with water-soluble humic acids The content of heavy metal, mg / kg Heavy metal before processing maximum permissible concentration after processing zinc 435.0 23.0 21.0 copper 3.65 3.0 0.1 lead 1.09 6.0 0.1 chromium 4.8 - 0.1

As can be seen from table 4 and graphs (figure 4, figure 5), the water-soluble humic acids obtained by the proposed method provide the conversion to a bioavailable form of copper, lead and chromium, reducing the concentration of the bioavailable form of zinc to the maximum permissible concentration.

Example 17

Wastewater with an iron ion concentration of 1.25 mg / L was treated with an aqueous solution of humic acids with a concentration of 1.0% by weight, obtained according to Example 1 (GK1), in a volume ratio of 1: 0.012. The results are shown in table 5 and in the graph (Fig.6).

Wastewater with an iron ion concentration of 1.25 mg / L was treated with an aqueous solution of humic acids with a concentration of 1.0 wt%, obtained according to Example 3 (GK2), in a volume ratio of 1: 0.012. The results are shown in table 5 and in the graph (Fig.6).

Example 18

Wastewater with an iron ion concentration of 0.3 mg / L was treated with an aqueous solution of humic acids with a concentration of 1.0 wt.% Obtained according to example 1 (GK1), in a volume ratio of 1: 0.012. The results are shown in table 5 and in the graph (Fig.6).

Wastewater with an iron ion concentration of 0.3 mg / L was treated with an aqueous solution of humic acids with a concentration of 1.0% by weight, obtained according to Example 3 (HC2), in a volume ratio of 1: 0.012. The results are shown in table 5 and in the graph (Fig.6).

Table 5 Wastewater treatment results with water-soluble humic acids No. of examples The iron content, mg / l before processing after processing GK2 after processing GK1 17 1.25 0.45 0.92 eighteen 0.30 0,065 0.23

The results of the experiment, presented in table 5 and in the graph (Fig.6), showed the efficiency of binding of iron ions in wastewater with water-soluble humic acids, and the best results were achieved using humic acids obtained in example 3 (using calcium hydroxide).

Claims (5)

1. A method of producing water-soluble humic acids from coal series caustobioliths, including exposure to caustobiolites with a potassium or sodium hydroxide concentration of 2.0-4.0 wt.%, Separating the liquid phase, treating it with acid, followed by separation in the field of centrifugal forces and releasing heavy phase treatment of the obtained heavy phase with hydroxide of alkali or alkaline earth metals to obtain the finished product, characterized in that the caustobiolites are subjected to abrasion with a solution of potassium or sodium hydroxide to obtain particles of size 250-5 μm in an amount of not less than 90 wt.%, and the heavy phase is also subjected to abrasion with hydroxide of an alkali or alkaline earth metal until a pH of 3.5-5.0 is reached. 2. The method according to claim 1, characterized in that the abrasion is carried out in a mill mill. 3. The method according to claim 1, characterized in that the caustobiolites and a solution of potassium or sodium hydroxide are taken in a mass ratio of 1: (0.5-2.0). 4. The method according to claim 1, characterized in that calcium hydroxide is used as the alkaline earth metal hydroxide. 5. The method according to claim 1, characterized in that a decanter is used to separate the phases in the field of centrifugal forces.

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