RU2744806C1 - Method for producing magnetically sorption material - Google Patents

Abstract

FIELD: sorbents.

SUBSTANCE: invention relates to a method for producing a magnetically controlled sorption material, which can be used where large amounts of aqueous solutions containing heavy metals are formed - in the processing and neutralization of chemical effluents in electroplating, metallurgy, leather production, organic synthesis, production of anticorrosive paints and others. The method of obtaining magnetically controlled sorption material includes mixing at a temperature of 40-70°C equal volumes of an aqueous solution containing iron chloride FeCl₃ and iron sulfate FeSO₄·7H₂O in a molar ratio from 1:1 to 1:2, in amounts providing the total iron content in the final material 50-70 g / l. The resulting mixture is stirred with a mechanical stirrer at a speed of 2000 rpm for 10-15 minutes. After that, sodium nitrite NaNO₂ is added to the reaction mixture in an amount of 1.5-2.5 wt% of the total iron content in the mixture, sodium nitrate NaNO₃ in an amount of 8-10% of the difference in the masses of FeSO₄·7H₂O and FeCl₃ and stirring is continued even in within 60-70 minutes to obtain a ferrite suspension.

EFFECT: invention improves magnetic activity of the obtained sorbent.

1 cl, 3 dwg, 2 tbl, 4 ex

Description

The proposed group of inventions relates to methods for the purification of industrial waste water from heavy metals with the extraction of the mentioned metals, as well as to methods of obtaining a magnetically controlled sorption material used for this, and can be used where large amounts of aqueous solutions containing heavy metals are formed: in processing processes and neutralization of chemical effluents in electroplating industries, metallurgy, leather production, organic synthesis, production of anticorrosive paints and others.

Sorption methods of wastewater treatment from heavy metal compounds that are not biodegradable, used along with reagent treatment, provide deep purification, however, in addition to high efficiency and mechanical strength, industrial sorbents require such qualities as availability, the possibility of further processing of the used sorbent and, at the same time, low cost. ...

The advantage of magnetic adsorbents is that their location can be controlled using a magnetic field. The latter circumstance makes it possible to easily extract the spent magnetic sorbent from the dispersion medium using magnetic probes, catchers, etc. Adsorbents with magnetic properties can be used for contact purification of substances, which greatly simplifies the adsorption process and ensures the completeness of the adsorbent utilization, makes it possible to replace the stage of separating the spent adsorbent from the solution, which is one of the laborious, magnetic separation. However, in order to ensure the efficiency of cleaning, it is necessary to take into account the influence of many factors and, first of all, the magnetic activity of the sorbent.

There is a method of obtaining a magnetic composite sorbent for purifying wastewater from ions of heavy metals and oil products (RU 2626363, publ. 2017.07.26), including the deposition of magnetite from a solution containing a mixture of ferric and ferrous chlorides on the surface of the waste wood MDF fiber, with a mass the ratio of said waste and said chlorides FeCl ₃ and FeCl ₂ as 10: 2.23: 0.99. The deposition is carried out with ammonia water under the influence of ultrasonic vibrations with a frequency of 35 kHz at a temperature of 25 ± 5 ° C. The resulting product is repeatedly washed with water to a neutral medium, and then dried in vacuum at a temperature of 110 ° C for 2 hours. A complex method requiring energy and labor does not provide the necessary correspondence between the cost of the produced sorbent and its operational properties.

A known method of obtaining a composite sorbent with magnetic properties, which can be used for the purification of industrial wastewater (RU 2661210, publ. 2018.07.13), including the preparation of a suspension of magnetite by dispersing magnetite Fe ₃ O ₄ in a 1-5% solution of polyvinyl alcohol and stirring at 80 ° C for 20 minutes, adding to the resulting suspension of coffee waste in a mass ratio of 1: (2-6), stirring at 80 ° C for one hour, filtering the resulting suspension and drying the resulting composite at 105 ° C to constant weight followed by grinding. Preliminary preparation of coffee waste is carried out by washing them until the color and neutral medium disappear with distilled water heated to 50 ° C, followed by filtering out the precipitate, drying in a convection oven at 105 ° C for 5 hours and processing with a 0.5 M alkali solution in for 24 hours at room temperature, and at least 10 parts by weight of alkali are taken for 1 part of the precipitate obtained. Multi-stage preparation of coffee raw materials significantly complicates the method, increases labor costs and, ultimately, increases the cost of the produced sorbent, the magnetic properties of which are relatively low.

The idea of using “zero cost” sorbents obtained from industrial and other waste for wastewater treatment, which is so tempting theoretically, in practice, is faced with a long, multi-stage and costly preparatory processing of this raw material. As a result, the method of obtaining a sorbent from waste turns out to be rather complicated, and its cost is far from zero, given the mediocre qualities of the obtained sorbent.

A known method of producing a magnetically controlled sorbent on a mineral basis for removing organic and inorganic contaminants from water systems and separating the spent sorbent by the method of magnetic separation (utility model UA 91147, publ. 2014.06.25). To obtain the sorbent, a natural clay mineral of the montmorilonite class is used: saponite NaMg ₃ [AlSi ₃ O ₁₀ ] (OH) ₂ ⋅4H ₂ O of natural origin and nanosized magnetite Fe ₃ O ₄ synthesized in the form of a magnetic fluid. To increase the number of active centers and the working surface of the sorbent, the saponite is modified with a 10-20% hydrochloric acid solution. The sorption base of the material obtained by a known method is a clay mineral, which at the same time is a ballast from the point of view of the magnetic activity of the material and prevents high magnetic characteristics from being obtained.

Composite sorption materials obtained by the above-described known methods do not differ in high sorption and magnetic characteristics due to the fact that their sorption properties are provided by some components, and magnetic - by others, while the heterogeneity of their composition causes difficulties in the collection of sorption material "loaded" with metals extracted from water - pollutants, using magnetic means, as well as difficulties at the stage of their desorption and utilization.

As the closest to the claimed technical essence is considered described in the Russian patent RU 2547496, publ. 2015.04.10, a method of obtaining a magnetoactive composite sorbent for collecting heavy metals and radionuclides, which is carried out by coprecipitation of aqueous solutions of iron (II) and iron (III) salts at a ratio of 2: 1 in the presence of alkali (NH ₄ OH) to obtain magnetite with a size particles of 7-30 nm, add humic acids or their salts to it at a ratio of 1: 4 to 4: 1, after which the resulting mixture is subjected to mechano-chemical treatment in a ball mill. Depending on the concentration of the polymer matrix, the processing equipment used, as well as the method of using the sorbent, the latter can be obtained in the form of diluted and concentrated liquids and powders.

The disadvantages of this method include the insufficiently pronounced magnetic activity of the sorbent obtained with its help, which is associated with the presence of a significant volume of polymer matrix formed by humic acids, which interferes with the effective control of the sorbent using magnetic means and its isolation by the method of magnetic separation. In addition, the sorbent obtained by a known method after collection is not subject to further use, but requires disposal as waste.

Sorption wastewater treatment, including the use of sorbents with magnetic properties, is currently widely used.

The known method (RU 2669853, publ. 2018.10.16) sorption purification of dissolved uranium from natural, waste and sea waters, providing effective treatment, as well as effective separation of sediment from the treated solution by the method of magnetic separation. The known purification method involves the use of sorption materials based on iron oxide systems with a macroporous structure containing a nanoscale phase of iron. The sorbent is introduced into the purified aqueous medium at a concentration of 1: 100 by weight with a content of uranyl ions in the solution of at least 10 g / l, at a pH of 2.5 to 7-8, at room temperature, kept for 3-8 to 48 hours, after which it is filtered and the precipitate is recovered. The known method is complex due to the use of a sorbent, the synthesis of which is multistage, time-consuming and laborious, while the known method provides for the extraction of only one uranium from contaminated aqueous media.

A group of inventions is known, which includes a method for producing a magnetic sorption material in the form of nanoparticles of iron oxide (II, III) and a method for purifying waste water with its help, which provides for the removal of solid suspended particles and total phosphorus (CN 109665566, publ. 2019.04.23). To obtain magnetic iron oxide (II, III) with nanosized particles, iron sulfate is dissolved in tap water, an alkaline compound is added to the resulting solution, and air is introduced into the solution at room temperature, ensuring constant stirring of the solution. According to the authors, the obtained magnetic nanosized iron (II, III) oxide is of high purity, and its nanoparticles have a uniform size and shape. However, the method chosen by the authors for the oxidation of iron sulfate with atmospheric oxygen at room temperature, as described in a known patent, in the absence of control over the completeness of the process, does not guarantee complete oxidation of iron sulfate and the formation of an effective sorption material. From the above abstract, the ratio of nanoparticles of iron oxides of different valence (II and III) during their simultaneous formation during the oxidation of iron sulfate is also unclear. Thus, there is no reliable evidence of obtaining a sorption material by a known method that provides effective wastewater treatment. In addition, the known method does not provide for the joint processing of the sorbent with the adsorbed heavy metal-pollutant.

Closest to the proposed method for extracting heavy metals from industrial wastewater is a method for purifying wastewater containing heavy metals (US 6666972, publ. 2003.12.23), using a sorption material, which is a spent highly magnetic iron oxide catalyst used in the synthesis of styrene monomer from ethyl benzene. This sorption material, which has served its life as a catalyst, is intended for the purification of acidic wastewater with a pH value of about 1.0 and containing Cu, Fe, Ni, Cr or Zn. It contains at least 70% of magnetite Fe ₃ O ₄ , as well as alkali and alkaline earth metals. According to the known method, for the purification of waste water from heavy metals, the mentioned sorption material based on iron oxide is introduced into the treated water at a weight ratio of water: sorbent equal to 1: 0.05; mechanically stir the resulting reaction mixture at a speed of 60 rpm for 15 minutes; separating the solid from the solution using magnetic means and removing the heavy metal compounds. The known method does not provide for the joint processing of the used sorption material and the heavy metals adsorbed by it. In addition, it is very likely that the previously "used" sorption material may carry unaccounted for impurities that are not of great importance for the subsequent disposal of pollutant metals, but may turn out to be extremely undesirable in the event of their subsequent processing to obtain a commercial product.

The objective of the proposed group of inventions is to create a method for producing a magnetically controlled sorbent extracted by magnetic means together with adsorbed pollutant metals from wastewater and processed together with them to obtain a commercial product, as well as a method for extracting these metals from industrial wastewater using the obtained sorbent ...

The technical result of the proposed group of inventions is to increase the magnetic activity of the obtained sorbent and the efficiency of its collection using magnetic means together with the adsorbed heavy metals and ensuring their subsequent joint processing to obtain a marketable product.

The specified technical result is achieved by a method of obtaining a magnetically controlled sorption material for the extraction of heavy metals from industrial wastewater, which is carried out by coprecipitation of iron (II) salts and iron (III) salts from aqueous solutions in the presence of alkali, in which, in contrast to the known, coprecipitation is carried out by mixing at a temperature of 40-70 ° C equal volumes of an aqueous solution containing iron (II) sulfate FeSO _{4 ⋅7H 2} O and iron (III) chloride FeCl ₃ in a molar ratio from 1: 1 to 2: 1, in amounts providing a total the iron content in the final material is 50-70 g / l, and an alkaline solution containing sodium hydroxide NaOH in an amount equal to half the total mass of FeCl ₃ and FeSO _{4 ⋅7H 2} O in the reaction mixture, which is stirred with a mechanical stirrer at a speed of 2000 rpm / min for 10-15 minutes, sodium nitrite NaNO ₂ is added in an amount of 1.5-2.0% of the total mass of iron, sodium nitrate NaNO ₃ in an amount of 8-10% of the difference in Fe masses SO ₄ ⋅7H ₂ O and FeCl ₃ in the above mixture and stirring is continued for another 60-70 minutes to obtain a ferrite suspension.

The specified technical result is also achieved by the method of extracting heavy metals from industrial wastewater, including the introduction of a sorption material based on iron oxides into wastewater, their mechanical stirring, the separation of solid matter from the solution to be purified from the solution to be purified with the extraction of heavy metals, in which, unlike from the known, as a sorption material, a ferrite suspension obtained by the proposed method is used, which is introduced into the wastewater at the rate of 1 weight part of the suspension per 1.5-2.5 weight parts of heavy metals-pollutants contained in the wastewater, while as a solid The substances are separated from the solution by magnetic separation from the solution of the ferrite suspension with adsorbed heavy metals and together with them are sent for processing by known methods.

The ferrite suspension obtained by the proposed method allows its repeated use until the sorption capacity is completely depleted, which is of practical importance in the case of a low concentration of heavy metals in the processed wastewater.

The method of obtaining magnetically controlled sorption material in the form of the above-mentioned ferrite suspension is carried out as follows.

A solution is prepared containing a salt of ferrous iron, which is mainly used as ferrous sulfate _{FeSO 4 H7H 2} O (ferrous sulfate) and a salt of ferric iron, which is mainly used as ferric chloride FeCl ₃ , while ferrous sulfate and ferric chloride are taken in molar a ratio from 1: 1 to 2: 1 in calculated quantities providing the total amount of iron II and iron III in solution of 50-70 g / l.

The prepared solution of iron salts FeCl ₃ and FeSO _{4 ⋅7H 2} O is heated to a temperature of 40-70 ° C and mixed with an equal volume of also heated aqueous solution containing NaOH in an amount equal to half of the total mass of iron salts. Stir with a mechanical stirrer at a speed of at least 2000 rpm. _{After stirring for 10-15 minutes, sodium nitrite NaNO 2} is introduced into the reaction mixture in the form of a hot solution in a small amount of water in an amount of 1-2% of the total content of iron II and iron III in this mixture and intensive stirring is continued for another 60 -70 minutes

The presence of alkali NaOH in the reaction mixture is necessary to control the properties of the medium under the influence of which the formation of iron oxide occurs, since these properties affect the recrystallization of iron hydroxide and the formation of certain phases of iron oxides in the form of nanosized particles.

Sodium nitrite NaNO ₂ contributes to the activation of the resulting material with an improvement in its sorption properties and at the same time is able to provide the oxidation of an excess amount of iron salts.

To oxidize an excess amount of ferrous sulfate FeSO _{4 ⋅7H 2} O in the reaction mixture, sodium nitrate NaNO ₃ is introduced into it in an amount of 8-10% of the difference between the masses _of FeSO _{4 ⋅7H 2} O and FeCl ₃ present in the mixture.

Thus, a material containing nanosized particles of iron oxides of various modifications is obtained, which is essentially a single magnetic component, the high sorption properties of which make it possible to carry out effective wastewater treatment with the extraction of heavy metals without additional means to enhance its sorption properties, i.e. without additional components.

FIG. 1 is a photograph showing the obtained sorption material in interaction with a permanent magnet, confirming its clearly pronounced magnetic properties.

The method of extracting heavy metals from industrial wastewater using the ferrite suspension obtained by the proposed method is carried out as follows.

Determine the concentration of polluting heavy metals in the original water samples, in particular, by atomic absorption spectrophotometry. Sorption material in the form of a ferrite suspension obtained by the above method is added to the treated waste water at the rate of 1 weight part of the suspension per 1.5-2.5 weight parts of heavy metals contained in the waste water and is stirred by mechanical means at a speed of 60-75 rpm min for 15-20 minutes.

After that, magnetic separation is carried out with the release of the magnetically controlled sorbent together with the adsorbed metals.

The chemical composition of the precipitate formed as a result of the purification of the model solution, dried and subjected to heat treatment for conversion into the oxide form, is presented in Table 1.

The resulting precipitate was subjected to drying at T = 105 ° C and heat treatment, which is necessary for the "manifestation" of the crystal structure of the material during X-ray diffraction, otherwise the material appears amorphous in the photographs.

FIG. 2 shows an X-ray diffraction pattern of the precipitate of the obtained ferrite suspension subjected to heat treatment at 1000 ° C, which unambiguously indicates the homogeneity of its composition.

FIG. 3 shows an X-ray diffraction pattern of a ferrite suspension sediment subjected to heat treatment at 1000 ° C after sorption of Fe, Cu, Zn, Ni, Cr (III), and Pb from an aqueous model solution.

FIG. 2 and 3, the following designations are used:

Comparison of the values shown in FIG. 2 and 3 of the X-ray diffraction patterns shows that after the sorption treatment of the model solution, only the peak of the iron-nickel spinel Ni _0.4 Fe _2.6 O ₄ appears on the X-ray diffraction pattern, which indicates that during the purification process sorption processes are accompanied only by structural changes in ferrite.

In principle, during the ferritic treatment of industrial wastewater containing heavy metals, the formation of ferromagnetic compounds of the spinel type is possible (nickel is an example), however, it is obvious that these changes are not massive. Ions of other metals practically do not participate in this process, but conglomerate around the particles of the ferrite suspension, acting as coagulation centers, and precipitate from the solution together with the ferrite suspension in the form of hydroxides; the process of sorption cleaning mainly occurs under the influence of forces due to the interaction of ions and solid particles with a magnetic field.

When treating wastewater with a high content of heavy metals, the ferrite suspension obtained by the proposed method, in addition to its sorption properties, exhibits the properties of a coagulant-precipitant.

As noted above, when working with wastewater that has low levels of pollutant metals, it is permissible to reuse and even reuse the ferrite suspension in the presence of an unused sorption capacity. The spent sorption material, which has completely exhausted its sorption capacity, in combination with adsorbed heavy metals, is easily and simply removed from the purified effluent using magnetic separation, filtered and sent for processing.

The sorption material obtained by the proposed method is suitable for joint processing with the extracted metals, since it practically does not add unnecessary ballast components to the resulting product.

Thus, the treatment of industrial wastewater by the proposed method with the help of the proposed sorption material makes it possible to utilize the spent sorbent with adsorbed heavy metals to obtain a final product that is safe for the environment and suitable for further use.

As a result, the proposed method, which is affordable, low-cost and safe, can be recommended as a reliable tool for industrial wastewater treatment

Examples of specific implementation of the invention

Example 1

Prepared 1 liter of a solution containing 162 g of FeCl ₃ and 278 g of FeSO ₄ 7H ₂ O, and 1 liter of a solution containing 220 g of NaOH. The alkaline solution was heated to 50 ° C. The prepared solutions were combined with stirring using an electric stirrer at a speed of 2000 rpm for 15 minutes. Then 1.7 g of sodium nitrite NaNO ₂ and 12 g of sodium nitrate NaNO ₃ , dissolved in a small amount of hot vaults, were added to the reaction mass. Thereafter, stirring at the same speed was continued for 1 hour. More than 2 liters of ferrite suspension was obtained, which is a rather thick greasy substance containing a mixture of iron oxides in the form of nanosized particles with a total Fe content of 54-55 g / l.

Example 2

Prepared 1 liter of a solution containing 162 g of FeCl ₃ and 556 g of FeSO ₄ 7H ₂ O and 1 liter of an aqueous solution containing 360 g of NaOH. Then they acted in the same way as in example 1, while 2.5 g of sodium nitrite NaNO ₂ and 39 g of sodium nitrate NaNO ₃ , dissolved in hot water, were introduced into the reaction mass. Similarly to example 1, received about 2.5 liters of ferrite suspension containing a mixture of nanosized particles of iron oxides with a total Fe content of about 67 g / l.

Example 3

A model solution containing, mg / l: Cu 31.7; Zn 105.0; Ni 28.4; Cr III 43.0; Pb 16.2; Fe 0.81. To one liter of this model solution, totaling 225.1 mg of heavy metals, the ferrite suspension obtained by the above method was added at the rate of 1 weight part of the suspension to 1.5 weight parts of the total content of heavy metals. Thus, 150 mg of the ferrite suspension prepared according to example 1 was added to 1 liter of the above solution. The necessary contact of the metal particles with the sorbent was ensured by mixing the solution to be cleaned with the sorbent using a mechanical stirrer at a low (60 rpm) speed for 15 minutes.

Then, by a known method, magnetic separation and filtration were carried out, and a sorbent with adsorbed metals, suitable for further processing, was isolated.

The composition of the thermally treated sludge of the ferrite suspension after purification with it using a model solution and adsorption of contaminating metals is shown in Table 1.

Table 2 shows the residual concentrations of heavy metals in the solution after cleaning with a ferrite suspension.

After a simple preparation (washing, if necessary, drying) the obtained conglomerate of the suspension with the adsorbed metals can be sent for processing in a known manner, for example, by the method of aluminothermy.

Example 4

The processing of the aforementioned model solution simulating industrial wastewater was carried out analogously to example 3. The ferrite suspension obtained according to example 2 was introduced at the rate of 1 weight part of the suspension per 2.5 weight parts of heavy metals contained in the solution to be purified, which amounted to 90 mg of suspension per 1 l solution to be cleaned.

The results are similar to those obtained in example 3.

Claims (1)

A method of obtaining a magnetically controlled sorption material for the extraction of heavy metals from industrial wastewater, which is carried out by coprecipitation of aqueous solutions of iron (II) salts and iron (III) salts in the presence of alkali, characterized in that the coprecipitation is carried out by mixing at a temperature of 40-70 ° C equal volumes of an aqueous solution containing iron (II) sulfate FeSO _{4 ⋅7H 2} O and iron (III) chloride FeCl ₃ in a molar ratio from 1: 1 to 2: 1, in amounts providing the total iron content in the final material 50-70 g / l, and an alkaline solution containing sodium hydroxide NaOH in an amount equal to half the total mass of FeCl ₃ and FeSO _{4 ⋅7H 2} O in the reaction mixture, which is stirred with a mechanical stirrer at a speed of 2000 rpm for 10-15 minutes, add sodium nitrite NaNO ₂ in the amount of 1.5-2.0% of the total weight of iron, sodium nitrate NaNO ₃ in the amount of 8-10% of the difference in the masses _of FeSO _{4 ⋅7H 2} O and FeCl ₃ in the mixture and continue stirring holding for another 60-70 minutes to obtain a ferrite suspension.

Images