Sorption material for fluoride removal from aqueous environments

Abstract

FIELD: environmental protection.SUBSTANCE: invention relates to sorption materials for removing fluorine from natural water systems and wastewater from various enterprises. The sorption material for purifying aquatic environments from fluoride consists of carriers in the form of minerals and rocks, as well as active components. Augite and volcanic pumice are used as carriers, and aluminium oxyhydroxide and aluminium hydroxide are used as active components, with the following ratio of components, wt.%: aluminium oxyhydroxide 5; aluminium hydroxide 10; augite 45; volcanic pumice 40.EFFECT: increase in the capacity of the sorption material for purifying aqueous media from fluorine is ensured with a reduction in its hydrodynamic resistance.1 cl, 1 tbl, 1 ex

Description

[0001] This invention relates to environmental protection, specifically to sorption materials for removing fluoride from natural water systems and wastewater from various industries. The claimed invention can find application in local water intakes, various industrial facilities, medium- and large-scale water treatment plants, and individual drinking water treatment systems.

[0002] A METHOD FOR PURIFYING NATURAL OR WASTE WATER FROM FLUORINE AND / OR PHOSPHATES is known (RU 2528999 dated 02 / 28 / 2013, published 09 / 20 / 2014), according to which the sorbent consists of calcium sulfate particles immobilized on fibrillated cellulose fibers containing in wt.% at least 95% of fibers with a length of no more than 1.2 mm and at least 55% of fibers with a length of no more than 0.6 mm, in an amount of 100-1200 parts by weight of calcium sulfate per 100 parts by weight of fibers.

[0003] The disadvantage of the claimed sorbent is that the material has a fibrous base and there are difficulties in using it in many water purification technologies and equipment, in practical water purification.

[0004] A SORBENT FOR PURIFYING WATER FROM HEAVY METAL IONS is known (RU 2328341 dated 01 / 09 / 2007, published 07 / 10 / 2008), consisting of crushed zeolite and nanophase material, which includes iron hydroxide, and also additionally contains nanophase boehmite in the following ratio of components, wt. %: nanophase iron hydroxide 12-18; nanophase boehmite 5-13; zeolite is the rest.

[0005] The disadvantages of this sorbent include the small cross-sectional area of ​​the carrier pores, which prevents the penetration of iron and aluminum compounds and the formation of iron and aluminum hydroxides on the inner surface of the zeolite. As a result, the active components settle on the outer surface of the zeolite, reducing the effective surface area of ​​the sorbent and, consequently, the sorption capacity. Furthermore, the presence of free nanoparticles in the sorbent, although increasing the effective surface area, significantly impairs the hydrodynamic performance of the purification process.

[0006] A SORBENT FOR PURIFYING AQUEOUS ENVIRONMENTS FROM FLUORINE is known (RU 2838080 dated 18.10.2024, published 10.04.2025), consisting of mineral carriers and an active component, characterized in that grossite and aragonite are used as mineral carriers, and aluminum oxyhydroxide nanofibers are used as the active component, with the following ratio of components, wt. %: aluminum oxyhydroxide nanofibers - 8; grossite - 46; aragonite - 46.

[0007] The disadvantages of this sorbent include the small cross-sectional area of ​​the carrier pores, which prevents the penetration of aluminum compounds and the formation of active sites on the inner surface of the minerals. As a result, the active components settle on the outer surface of the carriers, reducing the effective surface area of ​​the sorbent. Furthermore, the presence of free nanoparticles in the sorbent, although increasing the effective surface area, significantly impairs the hydrodynamic performance of the purification process.

[0008] The aim of the invention is to create a new sorption material that could effectively remove fluorine from an aqueous environment, with high initial concentrations for purifying aqueous environments from fluorine.

[0009] The technical result of the invention is an increase in the capacity of the developed sorption material for purifying aqueous media from fluorine with a reduction in its hydrodynamic resistance.

[0010] The technical result is achieved in that the sorption material for fluoride removal from aqueous media consists of mineral and rock carriers, as well as active components. Augite is used as the mineral carrier, volcanic pumice is the rock carrier, and aluminum oxyhydroxide and iron hydroxide are used as the active components, in the following ratio of components, by weight: aluminum oxyhydroxide - 5; aluminum hydroxide - 10; augite - 45; volcanic pumice - 40.

[0011] The claimed invention makes it possible to obtain a technical result that increases the efficiency of purifying aqueous media from fluoride ions and increases its capacity due to an increase in the active surface area.

[0012] Using a carrier of crushed augite mineral containing calcium silicate, this sorption material for aquatic environments is capable of more effectively removing fluoride from water. Volcanic pumice, used as a secondary carrier, also has sorption properties for fluoride extraction. Using both carriers increases the efficiency of fluoride extraction from aquatic environments during the use of the sorption material.

[0013] Using a carrier made from the mineral augite, which contains calcium silicate, which is capable of purifying aquatic environments from fluoride ions, the final sorption material exhibits enhanced sorption properties. The process of removing fluoride from water using calcium silicate involves several stages: 1. Chemical precipitation - calcium silicate decomposes into its constituent parts, the resulting calcium ions react with fluoride ions to form poorly soluble fluoride compounds. 2. Fluoride sorption - fluorine from the solution is sorbed on the surface of calcium hydrosilicate and silicon dioxide. 3. Anion exchange - anion exchange occurs on the surface of calcium hydrosilicate, which additionally removes some fluoride from the solution. The combination of these factors gives augite enhanced water purification properties.

[0014] Using volcanic pumice, a rock containing silicon dioxide, which is capable of binding fluoride ions from water, forming water-insoluble compounds. This occurs due to charged functional groups on the surface of the SiO2 particles, which attract fluoride ions.

[0015] The selected carriers have the properties of removing fluoride ions from an aqueous environment and, while being sufficiently strong, have reduced hydrodynamic resistance compared to analogues.

[0016] Using aluminum oxyhydroxide nanofibers as the active component, the resulting sorbent is given enhanced sorption properties for extracting fluoride ions from aqueous media. This is achieved by selectively binding fluoride ions into stable aluminofluoride complexes on the surface of the mineral carrier. Since the aluminum oxyhydroxide is present in a nanophase state, the sorption properties are significantly enhanced. Aluminum oxyhydroxide nanofibers alone cannot be used in practical water treatment due to their small size. However, when immobilized on the surface of a mineral carrier capable of extracting fluoride ions from water, they significantly increase the mineral's active surface area and, therefore, its water treatment properties.

[0017] By using aluminum hydroxide as the active component, the resulting material has enhanced sorption properties for extracting fluoride ions from aqueous media. This occurs through the formation of aluminum hydroxofluoride complexes during the interaction of fluoride ions in the aqueous medium with the aluminum hydroxide surface of the sorption material.

[0018] This combination of the presented components best ensures the result of extracting fluoride ions from the aqueous environment.

[0019] The result is a sorption material containing a sufficient amount of aluminum oxyhydroxide on the surface of the augite mineral carrier, significantly increasing the product's effective surface area and allowing for a higher content of the active component in the form of nanofibers, compared to similar sorbents. Furthermore, aluminum hydroxide is immobilized on the second carrier, porous volcanic pumice, both on the outer surface and within the pores. This combination ensures highly effective removal of fluoride ions from aqueous media.

[0020] The production of sorption material for purifying aqueous media from fluorine is solved as follows.

[0021] Take augite as a carrier mineral and volcanic pumice as a rock and crush them separately in an agate mortar. The crushed carriers are then sieved to the required granule size in a 1 to 1.5 mm range.

[0022] Synthesis Stage 1. A 10 g sample of the first crushed augite carrier is placed in a 2 dm3 laboratory glass beaker. 3 , followed by adding 1 dm3 of distilled water to it 3The bottom of the glass beaker containing the mixture is wrapped in basalt cloth and placed on an electric hotplate, heating the mixture to 70°C. An aqueous NaOH solution (20 grams per liter) is then added, bringing the mixture to a pH of 10. Pre-weighed AD1 food-grade aluminum powder (with a particle size of less than 0.1 mm) is added to the mixture in an amount of 0.84 grams. The synthesis is carried out under these conditions for 1 hour with occasional stirring. The temperature is monitored with a thermometer. After the synthesis, the hotplate is turned off, and the reaction mixture is cooled to room temperature. The beaker contents are then emptied onto a viscose filter, and the product is washed (filtered) using a Buchner funnel and a Bunsen flask. Filtration is carried out with distilled water until the product reaches a neutral pH, using a vacuum pump.After washing, the filtered material is dried in a drying oven at 180°C until all moisture is removed. This first synthesis stage results in the formation and immobilization of aluminum oxyhydroxide nanofibers on the surface of the mineral support, giving it additional active surface area and thereby enhancing its sorption properties.

[0023] Synthesis Stage 2. Take a 40 g sample of the second carrier in the form of crushed volcanic pumice and place it in a 1 dm3 glass beaker. 3 , which is placed in an ultrasonic bath filled with water. Take 17.3 g of aluminum chloride (AlCl3) and place it in a 500 cm3 glass beaker. 3 Then pour 200 cm into a glass with aluminum chloride. 3distilled water and stir with a glass rod until the reagent is completely dissolved. Next, pour the aqueous solution of aluminum chloride into a beaker containing a sample of volcanic pumice and turn on the ultrasound to better mix the contents. Then take a 25% solution of ammonia (NH₄OH) and slowly add it to the beaker with the contents while constantly stirring with a glass rod. The process is carried out at room temperature. Using a pH meter, monitor the pH of the medium and observe the precipitation of a white precipitate of aluminum hydroxide (Al(OH)3). The following reaction occurs: AlCl3 + 3NH4OH → Al(OH)3↓ + 3NH4Cl. Precipitation of aluminum hydroxide begins at a pH of ≈ 4-5. Complete precipitation is achieved at a pH of ≈ 6-7. Upon reaching a pH of ≈ 7, stop adding the aqueous solution of ammonia and leave the contents of the beaker for 10 minutes with the ultrasound turned on.After the synthesis process, the ultrasound is turned off, the precipitate is allowed to settle, and the contents of the beaker are filtered through a funnel fitted with a viscose filter. The precipitate is washed with distilled water until a negative reaction for chloride ions, as determined colorimetrically, is observed. The precipitate is dried in a water bath at 60°C and then cooled in a desiccator. This second synthesis stage results in the formation and immobilization of aluminum hydroxide both on the outer surface of the volcanic pumice and within its pores. This combination allows for more effective removal of fluoride ions from aqueous media with a short contact time.

[0024] Then the obtained materials after the first and second stages of synthesis are combined in equal proportions of 50 wt.%: 50 wt.% and used for further research.

[0025] This combination of carriers with properties for extracting fluoride ions from an aqueous medium and active components with high sorption characteristics in relation to fluorine, as well as their optimal combination, in the developed sorption material gives the final material qualitatively different water purification properties.

[0026] An example of practical implementation of obtaining a sorption material and its adsorption activity is given below.

[0027] Example

[0028] To obtain the stated sorption material, crushed mineral, augite and volcanic pumice rock are taken for one load in the following ratio of components, wt. %: aluminum oxyhydroxide - 5; aluminum hydroxide - 10; augite - 45; volcanic pumice - 40.

[0029] The mineral augite and the volcanic pumice rock are crushed in an agate mortar, then sieved on sieves (mesh size 1 mm and 1.5 mm) to the desired fraction of granules of 1-1.5 mm.

[0030] Synthesis Stage 1. Take a 10 g sample of crushed augite and immobilize aluminum oxyhydroxide nanofibers on its surface. For this purpose, place a sample of the crushed mineral carrier in a laboratory glass beaker (2 dm3). 3 ), pour 1 dm3 of distilled water into it 3 An aqueous NaOH solution with a concentration of 20 grams per liter is added until the pH reaches 10. The bottom of the beaker is then wrapped in basalt cloth and placed on an electric hotplate, heating the contents. The reaction mixture is heated to 70°C, followed by the addition of 0.84 grams of AD1 food-grade aluminum powder with a particle size of less than 0.1 mm.

[0031] The contents of the beaker are synthesized with periodic stirring for 1 hour, maintaining a temperature of 70°C. The resulting sorbent is then washed repeatedly with distilled water until the washing water reaches a neutral pH. The precipitate is then filtered on a Buchner funnel using a vacuum pump. The filtered precipitate is dried at a temperature of 180°C until completely free of moisture.

[0032] Synthesis Stage 2. Take a 40 g sample of the second carrier in the form of crushed volcanic pumice and place it in a 1 dm3 glass beaker. 3 , which is placed in an ultrasonic bath filled with water. Next, take 17.3 g of aluminum chloride (AlCl3) and place it in a 500 cm3 glass beaker. 3 Then pour 200 cm into a glass with aluminum chloride. 3distilled water and stir with a glass rod until the reagent is completely dissolved. Next, pour the aqueous aluminum chloride solution into a beaker containing a sample of volcanic pumice and turn on the ultrasound to better mix the contents. Then take a 25% ammonia solution (NH4OH) and slowly add it to the beaker with the contents while constantly stirring with a glass rod. The process is carried out at room temperature. Using a pH meter, monitor the pH of the medium and observe the formation of a white precipitate of aluminum hydroxide (Al(OH)3). Precipitation of aluminum hydroxide begins at a pH of ≈ 4-5. Complete precipitation is achieved at a pH of ≈ 6-7. When a pH of ≈ 7 is reached, stop adding the aqueous ammonia solution and leave the contents of the beaker for 10 minutes with the ultrasound turned on.After the synthesis process, turn off the ultrasound, allow the precipitate to settle, and filter the contents of the beaker through a funnel fitted with a viscose filter. The precipitate is washed with distilled water until a negative reaction for chloride ions, as determined colorimetrically, is achieved. Dry the precipitate in a water bath at 60°C and then cooled in a desiccator.

[0033] Then the obtained materials after the first and second stages of synthesis (augite modified with aluminum oxyhydroxide and volcanic pumice modified with aluminum hydroxide) are combined in equal proportions of 50 wt.%: 50 wt.% and used for further research.

[0034] The specific surface area and specific pore volume of the presented sorption material are determined using the thermal desorption method of nitrogen, using the SORBTOMETER M device. Specific surface area is 47.14 m 2 / g; specific pore volume - 0.02 cm 3 / G.

[0035] The studies of the developed sorption material and analogous materials to determine their static sorption capacity when extracting fluoride ions from an aqueous medium are carried out as follows.

[0036] A 1 g sample of the sorbent being studied is immersed in a glass beaker (200 cm 3 ), where the model solution is then poured in an amount of 100 cm 3 The beaker is then placed on a magnetic stirrer and stirred for 150 minutes. Model solutions containing fluoride ions are prepared in distilled water using sodium fluoride (NaF) at a concentration of 250.7 mg / dm3. 3 After mixing, the solution in the funnel was filtered through a blue ribbon filter paper. Fluoride ion content in the analyzed model and filtered solutions was analyzed using an Expert-001 pH meter and ion meter.

[0037] The test result is taken as the arithmetic mean of the results of three parallel determinations, the permissible difference between which should not exceed 5%.

[0038] The table provides a comparative analysis of the static sorption capacity of the claimed sorption material with analogues.

[0039] Table

[0040] Name of material Concentration of fluoride ions in the model solution, mg / dm3 Static sorption capacity, mg / g The claimed sorbent 250,7 23,4 Analogue 1 21,8 Analogue 2 15,1

[0041] As can be seen from the results of the tabular data, the developed sorption material for purifying aqueous media from fluoride has values ​​for static sorption capacity significantly higher than those of the materials of analogue 1 according to patent RU 2838080 and analogue 2 according to patent RU 2328341.

Claims

A sorption material for purifying aqueous media from fluoride, consisting of carriers in the form of a mineral and rock, as well as active components, characterized in that augite and volcanic pumice are used as carriers, and aluminum oxyhydroxide and aluminum hydroxide are used as active components, with the following ratio of components, wt.%: aluminum oxyhydroxide 5 aluminum hydroxide 10 augite 45 volcanic pumice 40