Method for producing composite sorbent based on thermally expanded graphite and mill scale for purifying aqueous solutions from petroleum products and heavy metal ions

Abstract

FIELD: wastewater treatment.SUBSTANCE: to obtain a composite sorbent based on thermally expanded graphite (TEG) and mill scale for purifying aqueous solutions from oil products and heavy metal ions, TEG powder and magnetite- and hematite-comprising mill scale of arbitrary shape with a particle size from 140 to 4000 µm are used. Repeated crushing and sifting of mill scale are carried out to obtain particles with a size of 140 to 160 mcm. A mixture of thermally expanded graphite and mill scale is prepared in such a way that the ratio between the components is, wt.%: TRG 5-15, mill scale 95-85. Cold pressing of the mixture is carried out using a matrix made of ferrous metals with an internal diameter of 12 to 52 mm at a pressing pressure of 5.1 to 58.9 MPa until a cylinder with a height of 14 to 68 mm is obtained.EFFECT: obtain a sorbent for simultaneous purification of industrial wastewater from petroleum products and heavy metal ions without the use of hazardous chemical environments and the disposal of mill scale.5 cl, 4 dwg, 2 tbl

Description

[0001] FIELD OF TECHNOLOGY

[0002] This invention relates to developments in the field of industrial wastewater treatment systems, specifically the use of sorbents for the effective removal of oil sludge compounds from industrial wastewater, which contain saturated and aromatic hydrocarbons, carboxylic acids, asphaltenes, tars, metal ions, including heavy metals, mechanical impurities, and, in some cases, radioactive elements. This sorbent can be used to treat wastewater from various organizations.

[0003] STATE OF THE ART

[0004] The development of technological progress is inextricably linked to the increase in industrial output of various products. As a result, large volumes of industrial wastewater are generated, containing various types of oil sludge. These sludges are amphoteric or finely crystalline masses containing from 50 to 95% water. It should be noted that the chemical composition of oil sludge is extremely complex and includes saturated and aromatic hydrocarbons, carboxylic acids, asphaltenes, tars, metal ions (depending on the type of production, primarily metallurgy, various heavy metals with an atomic mass greater than 50 atomic units appear), mechanical impurities, and radioactive elements if used in the process. Wastewater from power plants, including nuclear ones, is analyzed depending on the type of plant, as they vary greatly in the composition of hazardous elements and the methods for removing them.The sorbent proposed in our application can also be used in wastewater treatment systems of various thermal electric, solar and hydroelectric power plants.

[0005] A significant portion of petroleum products in industrial wastewater, along with a wide range of organic compounds, comes from cutting fluids (CWs), which can be divided into oil-based and water-miscible, as well as from degreasing solutions. Oil-based CWs are mineral oils (70-90%), either without additives or with additives for various functional purposes. Water-miscible CWs include three types: emulsifying, semi-synthetic, and synthetic. Emulsifying CWs (emulsols) are specially selected (balanced) mixtures of mineral oils, emulsifiers, binders (water, alcohols, glycols, etc.), corrosion inhibitors, biocides, antifoam agents, and various additives.In addition to emulsifiers, so-called water-miscible cutting fluids (WMFs) are increasingly used. These include semi-synthetic (containing trace amounts of petroleum oils) and synthetic (containing no petroleum oils) cutting fluids that mix well with water and form stable colloidal emulsions or solutions. The most important components of WMFs are vegetable oils (rapeseed, coriander, castor, and cottonseed), animal fats, and fat substitutes (synthetic fatty acids and naphthenic acids). Modern WMFs contain additives for various functional purposes (0.5-15%). These primarily include antiwear, extreme pressure, and antioxidant additives. The additives used are phosphates and dialkyl phosphates, dialkyl dithiophosphates and dialkyl dithiocarbamates of metals, amine salts and amides of dialkyl phosphoric acids, sulfurized fats, organic sulfides and polysulfides, chlorinated paraffins, antioxidants such as aromatic amines, alkanolamines, and polymethylsiloxane liquids (antifoam additives).To protect cutting fluids from microbiological damage, biocides are added. Triazines are used as biocides for cutting fluids, but oxazolines, thiazolines, formalin, furacilin, hexachlorophene, and vazin are also recommended. All of these components in cutting fluids can have extremely negative environmental impacts when accumulated in aqueous systems. It should be noted that they belong to hazard classes III (petroleum hydrocarbons) and IV (triethanolamine, carbamol, oleic acid, and others).

[0006] Heavy metal ions (classified as hazard class I (cadmium, lead, zinc), II (copper, chromium, nickel), and III (manganese)) in industrial wastewater, especially from metallurgical plants, pose a much greater danger to the environment. It's worth noting that when heavy metal ions, especially lead and cadmium, enter water bodies, the normal development of many lower organisms is disrupted at concentrations of 0.02 mg / L and above, and death is often observed at concentrations above 0.05 mg / L. These elements are naturally metabolized when released into water, but this is a lengthy process, so exceeding the maximum permissible concentration is highly undesirable. It's also worth noting that when chromium accumulates in the human body, its toxicological effects on vital organs manifest themselves, including damage to the brain and central nervous system. Chromium primarily enters the human body through water and food.The negative impact of heavy metal ions on the operation of wastewater treatment plants is particularly noteworthy. For example, the presence of copper and zinc in wastewater at concentrations of 0.5 mg / L inhibits sludge digestion at treatment plants by 5-6%. Increasing their concentration intensifies this inhibition. If the total concentration of heavy metal ions, such as copper, zinc, lead, chromium, and manganese, exceeds 80 mg / L, the treatment plant equipment may fail. This situation can arise at metallurgical plants, especially in the steel industry. Therefore, the first stage of wastewater treatment begins with the removal of heavy metal ions.

[0007] The steel industry requires, on the one hand, the purification of industrial wastewater from petroleum products and heavy metal ions, and on the other, waste disposal. The production of 1,000 kg of steel generates approximately 500 kg of various waste, of which mill scale accounts for approximately 50-60 kg. Storing and disposing of this waste in landfills, given limited storage space and increased transportation and other costs, becomes extremely costly and unsafe when large accumulations occur, potentially leading to serious environmental pollution. Recycling is the only option. It is worth noting that mill scale, due to its unique properties, is extremely difficult to use in the secondary steelmaking cycle (the process would be technologically complex and expensive). Steel produced using mill scale without government subsidies under the waste disposal program would be uncompetitive in price and would not be in demand by consumers.The various proposed methods for processing mill scale for the chemical industry are also extremely expensive to implement, and the use of scale in the construction industry is often ineffective compared to secondary materials from other industries, including metallurgy.

[0008] A large number of methods and technologies have been developed for this purpose. The most widely used method is chemical precipitation of heavy metal ions from an aqueous solution in special pools, followed by manual extraction from the sludge, packaging in special containers, and disposal at landfills. This method is costly (manual labor is required, the sludge contains high levels of petroleum chemicals, which require washing or is extremely difficult to package, etc.). The packaging itself takes up additional space during disposal along with additional waste. Workers must wear special clothing and protective equipment, as the sludge contains chromium. Furthermore, landfills must also install a clay screen at the disposal site. In some cases, an electrochemical process is used for purification, but this requires significant electrical energy and long periods of time to treat a given volume of wastewater (an extremely expensive treatment process).

[0009] Various models of filters based on carbon components and various metal powders have been proposed for purifying wastewater from heavy metal ions (a secondary method for utilizing metallurgical waste). The idea was to simultaneously filter oil products and heavy metal ions. However, problems arise with the subsequent disposal of this sorbent, preventing the release of heavy metal ions into the environment under various factors. Special containers for their disposal are also required. This entails significant costs for transporting the sorbents to the filter manufacturing site, among other expenses. In this situation, the search for new solutions for producing sorbents for the simultaneous filtration of oil products and heavy metal ions from industrial wastewater from metallurgical plants is extremely urgent, especially when using production waste for sorbent production.

[0010] DESCRIPTION OF ANALOGUES

[0011] One of the first inventions, which was used for wastewater purification from heavy metal ions using production waste (ash), can be considered a method for purifying wastewater from heavy metals and organic substances (A.S. SU1560483, C02F 1 / 28, BI No. 16, 1990), including ash treatment and sediment separation by sedimentation, in which the wastewater is sequentially treated first with ash containing CaO 30-50%, to a pH of 8.75-9.25, and then with ash containing CaO 3-5%, to a pH of 6.5. The disadvantage of this method is the low purification efficiency due to the low sorption capacity of ash in relation to copper, zinc and lead and the complexity of the technological process for large volumes of purification. And also the need to dispose of ash after sorption.

[0012] Another invention that can be considered similar in physical principle to our proposed invention is patent application RU 2051112 C1 (published December 27, 1995). The invention relates to methods for purifying wastewater from heavy metal ions and Cr(VI) by sorption and can find application in metallurgical and chemical industries with pickling and galvanic shops. The aim of the invention is to increase the efficiency of heavy metal ion removal by additionally extracting hexavalent chromium ions. To implement the method, wastewater containing chromium ions and other heavy metals is passed through a zeolite layer pre-treated with an oxalic acid solution with a concentration of 0.05-0.1 mol / l in the presence of a mineral acid to a pH of 1-2. The method allows increasing the degree of water purification from chromium (VI) ions to 100% while maintaining a high degree of purification for other heavy metal ions.The disadvantages of this invention include small volumes of wastewater treatment, high cost of the mineral and problems with the disposal of spent sorbent.

[0013] A method for adsorption water purification from heavy metal ions, petroleum products, phenol, and surfactants is also known (patent application (RU No. 2111171 published on May 20, 1998)) . Siliceous rock of mixed mineral composition is used as a natural adsorbent, containing, by weight: opal-cristobolite 30-49, zeolite 7-25, clay component 7-25, detrital-sand-silt material - the rest. A disadvantage of this method is the low degree of water purification from heavy metal ions. In addition, the rock is processed at a temperature of 250 °C, which requires the use of labor-intensive technological design of the sorbent activation process. The issue of spent sorbent disposal also remains open.

[0014] A related technical solution is a method for producing a composite sorbent for water purification from heavy metal ions (patent application RU No. 2328341, published November 10, 2008). The sorbent consists of 12-18% nanophase iron hydroxide, 5-13% nanophase boehmite, and ground zeolite from the Kholinskoye deposit. The sorbent can be produced in two ways. For the first method, zeolite is mixed with nanophase boehmite and iron hydroxide. The mixture is ground in an agate mortar and dried for 6 hours at 190°C. Nanophase boehmite is obtained by reacting aluminum powder with distilled water in a slightly alkaline medium. The mixture is heated to 50°C and left until the reaction is complete. The precipitate is filtered, washed to a neutral pH, dried for 2 hours at 50-75°C, and then the temperature is increased to 160°C and kept for another 6 hours.Nanophase iron hydroxide is obtained as a freshly precipitated gel by reacting aqueous solutions of ferric chloride and ammonia. To obtain the sorbent using the second method, crushed zeolite is placed in distilled water, aluminum powder is added, and the resulting mixture is heated to 50°C and left until the reaction is complete. The reaction is carried out in an alkaline medium using a concentrated NH4OH solution. The reaction mixture is acidified with hydrochloric acid to pH 4, and a FeCl3⋅6H2O solution (concentration 29.59 g / L) is added with stirring. After cooling the reaction mixture, the precipitate is filtered, washed to a neutral pH, and dried using the method described in the first method.The disadvantages of this method include: a large number of manufacturing stages and a lengthy manufacturing process; the use of caustic substances such as hydrochloric acid and concentrated ammonia solution; sintering of the material at high temperatures; and the use of zeolite from the Kholinsky deposit as an inert carrier, which increases delivery costs to various regions.

[0015] Also related in technical terms is a composite sorbent for water purification from heavy metal ions, consisting of modified chitosan and graphene oxide, and a method for producing it, presented in a Chinese patent (CN 103240063 A, published on August 14, 2013). The method involves producing graphene oxide by oxidizing graphite with concentrated sulfuric acid, sodium nitrate, and potassium permanganate, and producing amorphous chitosan by reacting it with chloroacetic acid and a quaternization agent. The resulting amorphous chitosan and graphene oxide are mixed and subjected to intense ultrasonication to intercalate the graphene oxide into nanosized particles and uniformly distribute the graphene oxide within the chitosan structure. The disadvantage of this method is the use of caustic substances (chloroacetic and concentrated sulfuric acid) and a strong oxidizing agent - potassium permanganate.Purification of contaminated water is carried out using a powdered composite, which necessitates additional operations to remove spent sorbent from purified water.

[0016] When considering sorbents, it is necessary to note the latest invention related to its production based on granular activated carbon, patent application (RU 2753230 C1 published on August 12, 2021). In the presented invention, granular activated carbon is treated with a modifying solution that ensures the formation of an active component on its surface - manganese (II) sulfide, in two stages. In the first stage, granular activated carbon is impregnated with a solution of manganese (II) sulfate with a concentration of 0.25-7.5 wt.% at a ratio of the mass of activated carbon to the volume of the solution (V P ), which is determined by the formula: V P = m a.y. ⋅V Σ ⋅Κ пр ., where m a.y - mass of activated carbon, g; V Σ- total pore volume, cm 3 / g; K пр . - impregnation coefficient (K пр= 0.8), followed by aging of the impregnated activated carbon and drying to an air-dry state. In the second stage, the resulting modified semi-product is placed for 0.5-1.5 hours in a 10% solution of sodium sulfide, taken in a 5% excess relative to the stoichiometry of the reaction equation of the interaction of manganese sulfate with sodium sulfide. The target product is separated from the liquid and dried. The resulting sorbent based on granular activated carbon, the surface of which is modified with manganese (II) sulfide in an amount of 1-10 wt.%, has a maximum equilibrium capacity of 2.3 mg / g, and ensures a mercury extraction rate from highly concentrated wastewater of over 90%. The above combination of essential features allows for the following technical result: an expanded range of sorbents for ensuring a high degree of mercury purification in aqueous media, represented by activated carbon modified with manganese sulfide, an increased degree of mercury ion purification in highly concentrated solutions, an increased service life of the sorbent, and the production of a sorbent with stable characteristics while reducing the time of its production. The disadvantages of this method include the high cost of spent sorbent disposal, which is not so important if it is used to purify water from heavy metal ions, including mercury. Without mercury purification, sorbent made of activated carbon granules is extremely rarely used to purify water from other heavy metal ions.

[0017] A similar invention in technical terms to ours is a method for producing a polymer sorption composite material for water purification from heavy metal ions, patent application (RU 2734712 C1 published on October 22, 2020). The application presents a composite sorbent based on potassium polytitanate and polyvinyl butyral, intended for the purification of industrial wastewater from heavy metal ions. A polymer sorption composite material for wastewater purification from heavy metal ions, consisting of 50-70% by weight of polyvinyl butyral and 30-50% by weight of potassium polytitanate, and a method for producing the polymer sorption composite material are proposed. The technical result of the patent is the production of a sorption material from low-hazard components with reduced labor costs.Among the disadvantages is that the developed sorbent is well suited for wastewater with low concentrations of oil sludge, which is uncommon in the steel industry. The cost of these components is not low compared to other sorbent components; only the manufacturing technology is simple, as is the case with other sorbents.

[0018] Similar in terms of the tasks to be solved (simultaneous purification of wastewater from heavy metals and oil sludge) is an invention that presents a sorbent made of natural materials, patent application (RU 2150997 C1 published on 20.06.2000). In the invention, a siliceous rock of mixed mineral composition is used as an adsorbent, containing in wt. %: opal-cristobolite 51-70, zeolite 9-25, clay component (montmorillonite, hydromica) 7-15, calcite 10-25, detrital-sand-silt material selected from deposits in Tatarstan. The air-dried adsorbent is crushed, ground, and sieved to separate the fraction (1.0-4.0)⋅10-3 m. The sample is calcined (at a temperature rise rate of 50°C per hour) in an electric furnace at 300°C for 2 hours. The pre-prepared sample and a 2 N hydrochloric acid (HCl) solution are loaded into a porcelain beaker at a solid:liquid ratio of 1:2.The treatment is carried out at room temperature for 20 minutes, stirring occasionally with a glass rod. The hydrochloric acid solution is then drained, and the adsorbent is neutralized with a 0.05 N NaOH solution to a pH of 7.0. The main disadvantage of this method, compared to the other methods discussed, is the use of hydrochloric acid, which requires equipment resistant to aggressive environments. This makes the sorbent production process complex and expensive. Shipping the material from Tatarstan also contributes to the cost.

[0019] Similar in implementation technology and application to expanded graphite is an invention (RU 2652704 C1, published April 28, 2018) for the purification of various environments from man-made pollutants, in particular for collecting spilled oil and other hydrocarbons from the surface of water bodies and soil, as well as for oil spill containment. The expanded graphite-based sorbent is modified with a magnetic phase represented by metal ferrites with improved performance characteristics due to the uniform distribution of the magnetic phase over the sorbent's surface, an increase in the magnetic phase content in the expanded graphite, and enhanced magnetic properties.The proposed method for producing a sorbent based on thermally expanded graphite modified, in essence, by a magnetic ferrite phase, which comprises the following stages: (A) impregnating intercalated graphite particles with an aqueous solution of salts, including a trivalent iron salt and a divalent metal salt with a content of each of said salts in an amount of from 2.5 to 25 mass %, where said salts are selected from a group of salts capable of decomposition in the temperature range from 500 to 1200 to iron (III) oxide and metal (II) oxide to carry out the sorption of said salts on the surface of graphite particles;

[0020] (B) separating the intercalated graphite particles impregnated in accordance with step (A) from the resulting liquid to obtain a solid phase;

[0021] (C) drying the solid phase to a free-flowing state; and

[0022] (D) heat treatment of the obtained solid phase in accordance with step (C) at a temperature of 500-1200°C.

[0023] In particular embodiments of the invention, the heat treatment at stage D is carried out in an air atmosphere. The trivalent iron salt at stage (A) can be a salt selected from the group consisting of FeCl3, Fe(NO3)3, and Fe2(SO4)3. And the divalent metal salt at stage (A) can be a salt selected from the group consisting of Co(NO3)2, Ni(NO3)2, Mg(NO3)2, CoCl2, NiCl2, and MgCl2. It is advisable to use bisulfate graphite particles as intercalated graphite particles at stage (A). The noted sorbent requires a long time to manufacture. Iron salts are expensive, and heat treatment requires a large amount of electrical energy. And the main purpose of this sorbent is to localize oil or fuel spills on the water surface and then collect them. The authors did not provide data on its possible use as a filter for wastewater containing heavy metal ions.

[0024] The invention (RU 2643963 C2 published on 06.02.2018) is similar in production technology (grinding the sorbent component) and in the problems of wastewater treatment from heavy metal ions and oil sludge. The invention presents the result of wastewater treatment using a sorbent made by grinding Kamennoyarsk opoka from the Astrakhan region, which contains (%): SiO2- 86.2, Al2O3- 4.15, Fe2O3- 1.56, TiO2- 0.2, K2O - 1.2, CaO - 1, Na2O up to 0.5; MgO up to 1. Opoka has a high sorption capacity in relation to ions of ammonium, potassium, rubidium, cesium, iron, cobalt, nickel, manganese (II), chromium (III), zinc, cadmium, lead, mercury, copper, alkaline earth, rare earth elements and a large group of organic substances, which can ensure a high degree of water purification in the domestic drinking water supply system.

[0025] After grinding, the flask is dried at 150°C, crushed, dust-free, and sieved to separate particles ranging in size from 1 to 8 mm with a residual moisture content of 2-5%. The objective of this invention is to expand the range of sorbents for water purification by developing a simple and environmentally friendly method for producing sorbents based on natural aluminosilicates, increasing their processing volumes, and reducing the time it takes to produce a high-quality product.

[0026] The essence of the claimed method for producing a natural sorbent for water purification in domestic and drinking water supply systems is as follows. To increase the sorption capacity, flasks are crushed and dispersed through screens. The flasks, with particles ranging from 50 to 100 mm in diameter and 50% moisture content, are loaded into a storage bin. An auger conveys them to a drying oven at 150°C (the flask exits with a moisture content of 16%). The flasks are then fed to a hammer mill via a belt conveyor, where they are broken into smaller granules. Dust with a particle size of 0-1 mm and a moisture content of 20% is sifted through a drum screen and sent by an auger to the storage bin. Next, the granules are conveyed to the workshop by a belt conveyor. A storage bin holds different types of granules (1,000 tons of 1-3 mm, 2,000 tons of 3-5 mm, and 2,000 tons of 5-8 mm). These are then fed via a screw to a vibrating screen with replaceable meshes. Three volumes of flasks with different particle sizes are then formed.They are pressed into various briquettes, mainly cylindrical in shape, and installed in bunker-type filters on the flow.

[0027] The disadvantages of this method of filter material production include the lack of use of recycled raw materials for the sorbents (delivery from the Astrakhan region is expensive). The large number of cycles required to prepare the sorbent using a drying oven (high energy consumption) makes this process expensive compared to other methods. The issue of subsequent disposal of the spent sorbent is also not addressed.

[0028] The closest invention to the use of iron oxide in a sorbent and the solving of wastewater treatment problems for heavy metal ions is the invention (US 20120168383, published July 5, 2012), which can be used as a prototype. The invention presents a sorbent consisting of a graphene-oxide complex. This complex consists of graphene and needle-shaped iron oxide nanoparticles grown on its surface. Their production uses a multi-step method that involves preparing a dispersed solution of reduced graphene and mixing the dispersed solution with a solution containing iron oxide precursors, which must be prepared using thermal treatment, to obtain a mixture.The mixture is then stirred to produce a dispersed graphene-iron oxide solution containing a graphene-oxide complex in which needle-shaped iron oxide nanoparticles are grown on the graphene surface (this stirring process takes a long time—at least two hours). The final step involves separation—separating the graphene-oxide complex from the dispersed graphene-oxide complex solution. The graphene-oxide complex is then used as a membrane filter to purify water of heavy metals.

[0029] To ensure the membrane filter properties of the graphene-oxide complex for water purification from heavy metals, needle-shaped iron oxide nanoparticles ranging in length from 10 nm to 500 nm must form on the graphene surface. This is achieved by using an iron oxide precursor—iron(II) pyrite or iron(III) pyrite—which affects the complex's sorption properties for filtering certain heavy metal ions. This point is reflected in the patent's description of various options for water purification from heavy metal ions.

[0030] Furthermore, after water purification from heavy metal ions, these complexes must be removed. A magnetic field is used for this purpose. The patent describes a method for removing the graphene-iron oxide complex, which adsorbs heavy metals, using a magnet. The photographs show that when the magnet is moved toward a solution of chromium ions mixed with the graphene-iron oxide complex (i.e., when a magnetic field is generated), the chromium ions are removed. Consequently, the solution, initially light yellow, becomes clear, and the graphene-iron oxide complex, which adsorbs heavy metals, is attracted to the magnet and adheres to the glass surface. This method for removing the complex with heavy metal ions is extremely difficult to apply technologically in industrial purification. Contact with such a complex will destroy the magnet. Furthermore, this complex with heavy metal ions must be disposed of at a landfill in special packaging.All this, taking into account the complex and expensive preparation of the complex itself, makes this method impractical for use in metallurgical plants for the purification of wastewater from heavy metal ions.

[0031] DISCLOSURE OF THE INVENTION

[0032] The problem that our invention is aimed at solving is the development of a method for producing a sorbent based on thermally expanded graphite (TEG) and mill scale for the simultaneous purification of industrial wastewater from petroleum products and heavy metal ions based on a new sorbent made of thermally expanded graphite with the addition of iron oxides (mill scale).

[0033] Another problem addressed by this invention relates to the recycling of mill scale stored at metallurgical plant landfills, which require appropriate maintenance. Recycling is associated with various complexities and, in some cases, is economically impractical.

[0034] To solve this problem, it is proposed to develop a method for producing a sorbent based on thermally expanded graphite with the inclusion of mill scale (iron oxide), which is a waste product of metallurgical production, in its structure.

[0035] A method for producing a composite sorbent based on thermally expanded graphite (TEG) and mill scale for purifying aqueous solutions from petroleum products and heavy metal ions, which consists in taking TEG powder and mill scale containing magnetite and hematite of arbitrary shape, with a particle size of 140 to 4000 μm; repeatedly crushing and sifting the mill scale to obtain particles ranging in size from 140 to 160 μm; preparing a mixture of thermally expanded graphite and mill scale in such a way that the ratio between TEG and mill scale is (wt.%): for TEG from 5 to 15, for mill scale - from 95 to 85; cold pressing of the mixture is carried out using a matrix made of ferrous metals with an internal diameter of 12 to 52 mm at a pressing pressure of 5.1 to 58.9 MPa until a dense volume in the form of a cylinder with a height of 14 to 68 mm is obtained.

[0036] The method for producing a composite sorbent additionally includes, at the stage of preparing the mixture, preliminary weighing of each component in a separate measuring container with an error of ± 0.05 g, and mixing of the weighed TEG and mill scale is carried out by filling the container simultaneously with manual stirring.

[0037] The method for producing a composite sorbent additionally includes, at the stage of preparing the mixture, repeating the mixing in a gravity mixer until the homogeneity of the prepared mixture is achieved to be at least 5%.

[0038] The mixture is prepared and pressed at a temperature of 10 to 35 °C.

[0039] The technical result, unlike previously achieved capabilities using the obtained data, is that the manufactured sorbent allows for water purification from heavy metal ions to levels below the MAC. The use of mill scale in the manufactured sorbent improved the filtering properties of thermally expanded graphite for removing oil sludge from water. The concentration of oil sludge in the water after filtration does not exceed the MAC, allowing this water to be sent for subsequent purification cycles.

[0040] Mill scale is a waste product of metallurgical enterprises; its use in the sorbent is a recycling method that does not require large expenditures for its processing (crushing into particles of 140-160 microns in size) for subsequent use in the manufacture of the sorbent.

[0041] Thermo-expanded graphite will act as a binding element when pressing mill scale into a dense volume for subsequent use as a filter element. Thermally expanded graphite is an effective sorbent for filtering oil sludge, creating an acidic environment in which heavy metal ions interact with the mill scale, forming ferrite compounds that are virtually insoluble in water and dilute aqueous solutions of strong mineral acids and alkalis. This allows, in addition to purifying wastewater from oil sludge and heavy metal ions, the developed sorbent ensures effective disposal after filtration.

[0042] The structure formed in the sorbent after water purification from heavy metal ions, unlike other filter sorbents, allows it to be placed in landfills with solid municipal waste without special packaging, which reduces the volume and cost of placement, or used as an auxiliary building material (backfilling the bottom of roads, bridge structures, etc.).

[0043] Solves the problem of industrial wastewater treatment and efficient mill scale recycling. The sorbent can be produced at the metallurgical plant, eliminating transportation and on-site scale storage costs. No special temperature conditions are required during pressing.

[0044] BRIEF DESCRIPTION OF DRAWINGS

[0045] Fig. 1 shows the appearance of thermally expanded graphite EG-350 with particle sizes of 300 ± 0.2 μm.

[0046] Fig. 2 shows the appearance of mill scale with particle sizes from 140 to 4000 µm.

[0047] Fig. 3 shows the manufactured sorbent made of thermally expanded graphite and mill scale with a component weight percentage of 15:85, respectively, in the form of a dense cylindrical volume with a diameter of 52 mm and a height of 14 mm at a pressing pressure of 5.1 MPa and a temperature of T = 23.2°C. The particle size of the TRG is 300 ± 0.2 μm, the particle size of the mill scale is from 140 to 160 μm.

[0048] Fig. 4 shows the manufactured sorbent made of thermally expanded graphite and mill scale with a component weight percentage of 5:95, respectively, in the form of a dense cylindrical volume with a diameter of 12 mm, a height of 68 mm at a pressing pressure of 58.9 MPa and a temperature of T = 23.4°C. The particle size of the TRG is 300 ± 0.2 μm, the particle size of the mill scale is from 140 to 160 μm.

[0049] IMPLEMENTATION OF THE INVENTION

[0050] Our proposed method is aimed at implementing comprehensive treatment of industrial wastewater from heavy metal ions and oil sludge using a new composite material formed from TEG and mill scale, a waste product of metallurgical production. Its disposal or reuse in process production has become an extremely complex and expensive process. The production of this sorbent does not require the use of hazardous chemicals or high energy costs, making it more in demand than previously developed sorbents.

[0051] Thermal-expanded graphite is a lead-gray or black crystalline oily powder (Fig. 1) with a metallic sheen and no odor. Experiments have shown that EG has a heterogeneous porous structure and a pronounced hydrophobic surface, which allows it to be used as a sorbent for purifying aqueous solutions from various chemical compounds. Therefore, the possibility of forming a sorbent based on thermally expanded graphite with the addition of a component that improves the properties of water purification from oil sludge and heavy metal ions was considered. Mill scale (a waste product of metallurgical production, where it is necessary to purify industrial wastewater from oil sludge and heavy metal ions) was considered as a purification-improving component. The appearance of mill scale is shown in Fig. 2.

[0052] The following steps were implemented in the production of the sorbent:

[0053] - Thermally expanding graphite grade EG-350 with a particle size of 300 ± 0.2 μm was selected;

[0054] - Mill scale containing magnetite and hematite is selected;

[0055] - To increase the stability of the sorbent structure, it was made by crushing from mill scale plates with repeated sifting to obtain particles with a size of 140 to 160 microns;

[0056] - The production of mill scale particles can be realized at a temperature of 10 to 35°C, which can meet different production conditions;

[0057] - The process of producing a mixture of TEG particles and mill scale was carried out using two-dimensional containers, into each of which these components were poured separately and weighed on scales with an error of ± 0.05 g.

[0058] - Next, another container was filled with these components at varying concentrations by weight (5 to 15% for TEG, 95 to 85% for mill scale) while manually mixing. After filling the container with the required amount to form a dense cylindrical volume (composite sorbent), the mixture was further mixed (by shaking and inversion in a gravity mixer). The uniformity (homogeneity) of the mixture's composition was determined visually and optically. Mixing was stopped when a homogeneous layer was formed on the surface of the mixture, or more precisely, until the homogeneity of the prepared mixture reached at least 5%.

[0059] - The mixture is then placed in a ferrous metal matrix shaped like a cylinder with an internal diameter of 12 to 52 mm and cold-pressed at a pressing pressure of 5.1 to 58.9 MPa. This produces a dense, cylindrical composite sorbent with a height of 14 to 68 mm, suitable for filtration. Unlike most similar sorbents, heat treatment of the composite sorbent before pressing is not required.

[0060] Fig. 3 and 4 show the external views of dense volumes in the form of cylinders obtained from a composite sorbent according to the proposed method of its manufacture.

[0061] To test the performance of the sorbent obtained according to the proposed method for purifying industrial wastewater from oil sludge and heavy metal ions, an experimental setup was developed. A cone-shaped vessel with a draining tube at its end was placed on a rigid support (22 cm above the table surface). A water collection tank was located beneath the tube. A polymer frame, rigidly attached to the vessel walls, was placed inside the vessel, into which a dense volume of composite sorbent was inserted. The height of the dense cylindrical volume should be less than the height of the frame walls. The liquid (a model solution containing heavy metal ions and oil sludge) to be purified was poured into the upper part of the vessel.

[0062] Water purification took place in the presence of air, similar to filters used in pool-type treatment facilities, such as those used in metallurgical plants. After passing through the sorbent, the water flows through a tube into a collection tank, which is exposed to air. At the plants, the purified water enters an intake pit for further filtration or for a closed production cycle. This process also occurs in the presence of air. All the conditions for a real water purification process are met. It's important to note that the filtration process, using our sorbent made from TGR and mill scale, is independent of ambient temperature (the adsorbent components are resistant to temperature changes).

[0063] To test the adsorption characteristics of the proposed composite sorbent from TRG and mill scale, an aqueous model solution was prepared with heavy metal ions and oil sludge in concentrations (Table 1) exceeding their content in the wastewater of a steel plant (PJSC Izhorskie Zavody).

[0064] Various dense cylindrical volumes were produced with different ratios of thermally expanded graphite and mill scale by weight in %: thermally expanded graphite 5-15 and mill scale 95-85.

[0065] For example, Table 1 shows the results of filtration of a model solution with a sorbent containing a percentage of TEG and mill scale by weight of 5:95, from which a dense cylindrical volume with a diameter of 12 mm, a height of 68 mm was made under a pressing pressure of 58.9 MPa and a temperature of T = 23.4 °C. The particle size of TEG is 300 ± 0.2 μm, the particle size of mill scale is from 140 to 160 μm.

[0066] Table 1. Results of water monitoring for the presence of oil products and heavy metal ions.

[0067] Elements Industrial wastewater of the enterprise Model solution Model solution after filtration MAC mg / l Oil sludge 2.433 ± 0.147 4.564 ± 0.228 0.011 ± 0.001 0.02 Copper 0.145 ± 0.014 0.345 ± 0.017 0.0061 ± 0.0001 0.03 Zinc 0.262 ± 0.025 0.546 ± 0.022 0.0032 ± 0.0001 0.01 Nickel 0.156 ± 0.014 0.234 ± 0.016 0.0043 ± 0.0001 0.02 Chromium (III) 0.298 ± 0.027 0.462 ± 0.023 0.0051 ± 0.0001 0.02 Manganese 0.547 ± 0.052 1.231 ± 0.061 0.0072 ± 0.0001 0.04 Lead 0.225 ± 0.021 0.512 ± 0.026 0.0084 ± 0.0002 0.01

[0068] A decrease in pressing pressure during the production of a sorbent in the form of a dense cylindrical volume with a diameter of 12 mm and a height of 68 mm, or an increase in the mass content of mill scale in the sorbent at a pressing pressure of 58.9 MPa leads to the destruction of the dense volume during storage.

[0069] For example, Table 2 shows the results of filtration of a model solution with a sorbent containing a percentage of TEG and mill scale by weight of 15:85, from which a dense cylindrical sorbent volume with a diameter of 52 mm, a height of 14 mm was made under a pressing pressure of 5.1 MPa and at a temperature of T = 23.2 °C. The particle size of TEG is 300 ± 0.2 μm, the particle size of mill scale is from 140 to 160 μm.

[0070] Table 2. Results of water monitoring for the presence of oil products and heavy metal ions.

[0071] Elements Industrial wastewater of the enterprise Model solution Model solution after filtration MAC mg / l Oil sludge 2.433 ± 0.147 4.564 ± 0.228 0.014 ± 0.001 0.02 Copper 0.145 ± 0.014 0.345 ± 0.017 0.0088 ± 0.0002 0.03 Zinc 0.262 ± 0.025 0.546 ± 0.022 0.0061 ± 0.0002 0.01 Nickel 0.156 ± 0.014 0.234 ± 0.016 0.0057 ± 0.0002 0.02 Chromium (III) 0.298 ± 0.027 0.462 ± 0.023 0.0083 ± 0.0002 0.02 Manganese 0.547 ± 0.052 1.231 ± 0.061 0.0123 ± 0.0002 0.04 Lead 0.225 ± 0.021 0.512 ± 0.026 0.0098 ± 0.0002 0.01

[0072] Increasing the pressing pressure when producing a sorbent in the form of a dense cylindrical volume with a diameter of 52 mm and a height of 14 mm leads to an increase in filtration time, which is impractical when conducting water purification.

[0073] The obtained results show that the manufactured sorbents with the specified percentage concentrations by weight between TEG and mill scale at pressing pressures from 5.1 to 58.9 MPa enable water purification from heavy metal ions to levels below the MAC. Based on this indicator for heavy metal ions, the water can be used for further production. The use of mill scale in the manufactured sorbent improved the filtering properties of TEG for water purification from oil sludge.

[0074] The obtained filtration results show that the water meets the standards for drinking water in terms of the content of heavy metal ions and oil sludge.

[0075] Metal mill scale (iron oxide) exhibits unique physical and chemical properties for interaction with heavy metal ions in an aqueous environment in the presence of oxygen. This forms a solid ferrite sludge, which is subsequently virtually insoluble in water and dilute aqueous solutions of strong mineral acids and alkalis, which may be present at landfills. This allows the resulting composite sorbent made of thermally expanded graphite, which filters petroleum products, to be stored with the mill scale at landfills (and, with certain technologies, used as a cushion for road construction, etc.).

Claims

1. A method for producing a composite sorbent based on thermally expanded graphite (TEG) and mill scale for purifying aqueous solutions from petroleum products and heavy metal ions, comprising the steps of taking TEG powder and magnetite- and hematite-containing mill scale of arbitrary shape and with a particle size from 140 to 4000 μm; Repeated crushing and sifting of mill scale is carried out to obtain scale particles with a size of 140 to 160 microns; a mixture of thermally expanded graphite and mill scale is prepared in such a way that the ratio between the TEG and mill scale is, by weight %: for TEG from 5 to 15, for mill scale from 95 to 85; cold pressing of the mixture is carried out using a matrix made of ferrous metals with an internal diameter of 12 to 52 mm at a pressing pressure of 5.1 to 58.9 MPa until a dense volume in the form of a cylinder with a height of 14 to 68 mm is obtained.

2. A method for producing a composite sorbent according to paragraph 1, characterized in that TRG powder with a particle size of 300±0.2 μm is taken.

3. The method for producing a composite sorbent according to paragraph 1, characterized in that at the stage of preparing the mixture, each component is pre-weighed in a separate measuring container with an error of ±0.05 g, and the mixing of the weighed TEG and mill scale is carried out by filling the container simultaneously with manual mixing.

4. A method for producing a composite sorbent according to paragraph 1, characterized in that at the stage of preparing the mixture, mixing is additionally repeated in a gravity mixer until the homogeneity of the prepared mixture is achieved at least at 5%.

5. A method for producing a composite sorbent according to paragraph 1, characterized in that the preparation of the mixture and pressing are carried out at a temperature of 10 to 35 °C.

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