RU2522630C1 - Method of purifying technogenic waters - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method of purifying technogenic waters includes dissolution of polyethyleneglycol terephthalate in an organic solvent, supply of the obtained mixture into water to be purified and further floatation of the processed water at pH 708 with separation of ions of heavy metals. Polyethyleneglycol terephthalate is dissolved in glycerol in a ratio 1:1-1:3, with supply of the obtained mixture into water to be purified in an amount of 0.2-0.4 l/m³.

EFFECT: invention makes it possible to increase transparency of the purified water and increase concentration of oxygen dissolved in it with preservation of a high degree of purification.

2 tbl

Description

The invention relates to the field of treatment of man-made waters, namely wastewater from metallurgical, galvanic and other industrial industries, quarry and mine waters from a wide range of toxic heavy metals, and can be used in mining and metallurgical enterprises.

A known method of wastewater treatment from heavy metal ions, including the treatment of water with a flotation reagent and subsequent flotation. In this case, as a flotation reagent, a composition containing synthetic fatty acid salts with a hydrocarbon radical length of more than C ₂₁ in an amount of 85-85 wt.%, A mixture of pyran and dioxane alcohols in an amount of 5-15 wt.% Is used (see RF patent No. 2038328 , C02F 1/62).

The known method, although it provides a sufficiently high degree of water purification, but only from some heavy metals. At the same time, such toxic metals as lead and cadmium, as well as a large number of suspended particles, which reduce the transparency of the water, completely remain in the water, and therefore the discharge of such water into water bodies can lead to their pollution and siltation, which adversely affects the fauna of the aquatic pool.

The closest analogue to the claimed object is a method of treating wastewater from heavy metal ions, including pre-dissolving polyethylene glycol terephthalate in an organic solvent, feeding the resulting mixture into purified water and subsequent flotation of the treated water at pH 7-8 with separation of zinc and copper ions. In this case, ethylene glycol is used as an organic solvent, the resulting mixture is fed into purified water in an amount of 0.3-0.5 l / m ³ , and flotation is carried out in two stages: at pH 2-3 and pH 7-8 with selective separation of ions heavy metals (see RF patent No. 2359920, C02F 1/62).

The known method, providing a sufficiently high degree of purification of water from copper (II) ions and zinc, however, has the disadvantage that it is impossible to completely remove other toxic heavy metals, such as nickel, lead, cadmium, iron, from purified water. In addition, a significant amount of suspended particles remains in the water purified by a known technology, which reduces its transparency, and the concentration of dissolved oxygen in it is negligible. All this worsens the quality of treated water, limits the possibility of discharge of such water into natural water bodies due to its non-compliance with MPC standards. In addition, ethylene glycol used as a solvent for polyethylene glycol terephthalate is toxic and belongs to the third hazard class. It has a narcotic effect and, if ingested through the skin, can cause chronic poisoning with damage to vital human organs (blood vessels, kidneys, nervous system), which is unsafe for workers.

The problem solved by the invention is to improve the quality of purified water, ensuring its environmentally safe use.

The technical result created by the claimed invention is to create conditions for simultaneously increasing the transparency of purified water and increasing the concentration of dissolved oxygen in it while maintaining a high degree of purification from a wide range of toxic heavy metals contained in it.

The problem is solved in that in the known method for purifying man-made waters, including dissolving polyethylene glycol terephthalate in an organic solvent, feeding the resulting mixture into purified water and then flotating the treated water at pH 7-8 with the separation of toxic heavy metal ions, according to the invention, polyethylene glycol terephthalate is dissolved in glycerol, and in the purified water, the resulting mixture is fed in an amount of 0.2-0.4 l / m ³ .

Polyethylene glycol terephthalate belongs to the group of aliphatic-aromatic polyesters. Polyethylene glycol terephthalate as a solid household waste of used PET containers, films, fibers is a thermoplastic with a melting point t _PL = 260 ° C and a density of 1.38-1.4 g / cm ³ . This household waste accounts for up to 40% of the total volume of garbage at the landfills of the country and is usually subject to burial or incineration, as a result of which its decomposition products have a harmful effect on the environment and, therefore, worsen the ecological situation.

Glycerin is a solvent and is a colorless transparent, viscous, odorless sweet taste with a melting point t _PL = 17.9 ° C and a boiling point t _Kip = 290 ° C. The advantage of using glycerol as an organic solvent is its non-toxicity.

The mixture of dissolved polyethylene glycol terephthalate in glycerol is a stable, odorless, light yellow emulsion with a boiling point t _boiling point = 295 ° C and a density of 1.37-1.52 g / cm ³ . Acylglycerols formed during the destruction of polyethylene glycol terephthalate have low toxicity (hazard class 4).

It is known to use glycerol as a component in the manufacture of explosives, alkyd resins, polyurethanes, acrolein, emulsifiers, antifreezes, lubricants, creams for shoes, soaps and adhesives, perfumes and cosmetics, medical ointments, liquors and confectionery, as a fabric softener, leather, paper; as a plasticizer in the production of plastics; as a solvent for extracts, flavorings and food colors (see. Great Encyclopedic Dictionary. M: Chemistry, 1998, p.138).

In the inventive method, glycerol, when reacted with polyethylene glycol terephthalate, exhibits a known solvent property. However, along with the well-known technical property in a mixture with polyethylene glycol terephthalate, glycerol contributes to the creation of nucleophilic reaction centers that ensure the simultaneous manifestation of the above mixture of a complex of new technical properties: collective, foaming and aggregating properties.

This is due to the fact that polyethylene glycol terephthalate in a mixture with glycerin undergoes degradation to form a number of compounds containing nucleophilic reaction centers, such as hydroxyl-OH, ester-C (O) O-, carboxyl-C (O) OH - groups, and also aromatic structures. The molecules of the degradation products belong to the Lewis bases and are nucleophilic reagents with electron-donating active centers. Heavy metal ions in flotation systems at pH 7-8 are in the form of aquacations and aquahydroxocomplexes; they are Lewis acids containing electrophilic centers with electron-withdrawing properties. The electron-withdrawing nucleophilic groups formed during the degradation of polyethylene glycol terephthalate in glycerol form chelate complexes with heavy metals such as copper, zinc, nickel, lead, iron, cadmium, and simultaneously with suspended particles such as clay, sand, silt particles, suspended organic and inorganic substances located in the treated water. The molecules of the compounds that make up the mixture are ligands that bind aquacations and aquahydroxocomplexes of toxic heavy metals of purified water into sublates due to chemical and nonspecific interactions. The resulting complex compounds are characterized by high stabilization energy by the field of ligands, since they do not have an external sphere, and, consequently, solvation centers, which prevents their dissolution in water. Moreover, their high stability is a consequence of the screening of heavy metal ions by ligands. Glycerin promotes the formation of finely dispersed hydrophobic precipitates of metal ions with a low density and large surface area (sublates) and, during subsequent flotation of the purified water, small air bubbles, floating in the water volume, interact with the sublates and bring them to the surface, forming a three-phase stable foam, which subsequently subjected to thickening and filtering.

Due to the presence of three hydroxyl groups in the molecule, glycerol gives three rows of derivatives, and mono- and dipro derivatives can exist as two structural isomers, and glycerol derivatives of the type CH ₂ XCHOHCH ₂ OH or CH ₂ XCHXCH ₂ OH as optical isomers.

Mono- and dipro derivatives of glycerol contain free hydroxyl groups located in the transposition and are reaction centers for active centers of suspended particles, such as clay, sand, silt, suspended organic and inorganic substances present in water. As a result of a specific interaction between them, agglomerates are formed, which are also captured by foam bubbles and are removed from the water in the form of flocculated particles. The synergistic effect of a mixture of polyethylene glycol terephthalate in glycerol is due to the formation of porous nanostructures having the appearance of cell cells, which then, due to self-organization processes, form more complex bulk structures with flocculation activity.

Along with the collective properties of the inventive mixture exhibits foaming properties. The combination of a mixture of polyethylene glycol terephthalate formed in the process of degradation in glycerol, alkoxy and hydroxy groups synergistically increases the foaming properties of this mixture. Adsorbed at the water-air interface, alkoxy and hydroxy groups are oriented to the water phase. Interacting with these polar groups, water dipoles hydrate them, creating a skeleton of a cellular film-channel structure of known stiffness and contributing to the strengthening of the surface adsorption layer of the air bubble. Glycerin, having a high viscosity, concentrates on the surface of the water - air, locally increasing the viscosity and, therefore, the stability of the foams. The presence of three hydroxyl groups of glycerol, which carry a significant negative charge on the oxygen atoms, and the high polarization of the molecules of the claimed mixture increase its dispersion and stability of the resulting foam bubbles due to the high surface activity of glycerol with respect to the liquid-gas phase boundary, which makes the three-phase highly stable foam and allows for the efficient purification of man-made waters not only from toxic heavy metals, but also from suspended particles in them, which considerably increases the transparency of the purified water. At the same time, water molecules freed from various types of interactions with metal ions and suspended particles form stable hydrogen bonds with oxygen molecules, which provides an increase in the degree of saturation of purified water with oxygen.

In addition, the mixture of polyethylene glycol terephthalate with glycerin has a high affinity for heavy metal ions and suspended particles, so the consumption of the mixture for water purification is extremely small. Glycerin, unlike ethylene glycol, is non-toxic (used in the food industry), more accessible. Thus, in the inventive method for purifying man-made waters, the reagent and technological modes allow to ensure high quality of purified water due to its simultaneous high degree of purification from a wide range of toxic heavy metals, increasing the transparency of water and increasing the concentration of dissolved oxygen in it. At the same time, glycerin is non-toxic and its use for water purification is safe. All this allows the use of purified water not only as recycle for industrial conditions, but also as environmentally friendly for discharge into rivers and lakes, which will ensure the safety of the fauna of water pools.

Based on the above analysis, we can conclude that for a specialist, the inventive method for purifying man-made waters does not follow explicitly from the prior art, and therefore meets the patentability condition “inventive step”.

An example of the method

Polyethylene glycol terephthalate, for example, in the form of fiber or solid PET containers, is crushed and pre-dissolved in glycerol in a ratio of 1: 1-1: 3 at a temperature of 200 ° C. The resulting mixture is a stable emulsion of light yellow color.

The dissolution of polyethylene glycol terephthalate in glycerol in the claimed amount of 1: 1-1: 3 allows you to get a mixture that simultaneously has a set of technical properties: collective, foaming and aggregating. This will ensure the extraction of a wide range of heavy toxic metals from purified water, such as copper, zinc, nickel, lead, iron, cadmium, increase its transparency and increase the concentration of oxygen dissolved in water. All this improves the quality of purified water, ensuring environmental safety of its use.

It is not advisable to mix polyethylene glycol terephthalate with glycerin in a ratio of less than 1: 1, since polyethylene glycol terephthalate is not completely degraded in the mixture, solid particles of polyethylene glycol terephthalate remain in the mixture, which leads to the extraction of an insignificant part of heavy metals, and suspended particles completely remain in water, in As a result, the quality of purified water is sharply reduced.

Mixing polyethylene glycol terephthalate with glycerin in a ratio of more than 1: 3 is also impractical, because, firstly, an excess of glycerol in the mixture will lead to a higher cost of technology. Secondly, glycerol molecules in the treated water will form hydrophilic complex compounds with heavy metal ions, which will reduce the degree of water purification from them, while highly toxic heavy metals such as lead and cadmium will remain completely in the purified water. In addition, glycerin adsorbed on the surface of suspended particles will form a protective shell, which is a kind of structural and mechanical barrier to the formation of agglomerates, and this will reduce the quality of purified water and exclude the possibility of its discharge into natural water bodies without additional purification.

In the inventive method, after dissolving the polyethylene glycol terephthalate in glycerol, the resulting mixture in an amount of 0.2-0.4 l / m ^{3 is} fed into the chamber of a flotation machine with purified technogenic water. Then carry out the flotation process at pH 7-8.

Technogenic water and the mixture are floated for 5 minutes until the formation of a foam product containing sublates of heavy metals and suspended particles. After that, the resulting foam products containing valuable components such as copper, zinc, nickel, lead, iron, cadmium and representing commercial products are dried and sent for subsequent use in metallurgical processes.

At the same time, purified water can be used: firstly, as circulating water in production processes or as technical water - for use in heating systems, and secondly, as environmentally friendly because of high transparency and saturation with sufficient oxygen, purified water can be discharged into rivers and lakes , including in reservoirs of fishery enterprises.

The supply of the mixture in the claimed amount to the flotation process allows to improve adsorption due to the interaction of polar atoms and functional groups of its molecules with electrophilic centers of heavy metals. Improving the adsorption conditions of the collector allows to increase hydrophobization and floatability, and therefore, allows to extract all toxic heavy metals and suspended particles from the purified water at the same time.

Serving a mixture of polyethylene glycol terephthalate with glycerol in an amount of less than 0.2 l / m ^{3 is} impractical, since this reduces the degree of water purification, which is explained by the deficiency of active nucleophilic centers.

It is not advisable to increase the flow rate of the mixture by more than 0.4 l / m ³ , since there is an excess of the mixture in the treated water, which reduces the transparency of the water and increases the cost of additional water treatment.

To substantiate the advantages of the proposed method for purifying man-made waters in comparison with the method taken as a prototype, laboratory tests were carried out.

Technogenic water was purified, containing, mg / L: copper 250, zinc 170, iron 220, nickel 2, lead 0.5, cadmium 0.6.

For water purification, a mixture of dissolved polyethylene glycol terephthalate in glycerol was used.

In the process of laboratory tests, 16 experiments were carried out, including: experiments No. 1-9 - with the claimed technological modes; experience No. 10, 11, 12 - with modes that go beyond the minimum declared values; experience No. 13, 14, 15 - with modes that go beyond the maximum declared values; experience No. 16 - with the modes of the method taken as a prototype.

In the method taken as a prototype, a flotation reagent obtained by dissolving polyethylene glycol terephthalate in ethylene glycol in an amount of 0.5 l / m ^{3 was} fed into the chamber of a flotation machine with purified technogenic water.

The flotation process according to the claimed method and prototype was carried out at pH 7-8 for 5 minutes. In laboratory experiments, the foam product by gravity went to the filtration unit, and purified water went to the control.

The compositions of the mixtures and technological modes of the investigated methods of water purification are presented in table No. 1.

The results of laboratory tests are shown in table No. 2.

As can be seen from the test results shown in table 2, the inventive method of purification of industrial wastewater (experiments No. 1-No. 9) compared with the prototype (experiment No. 14) can improve the quality of purified water due to:

- a high degree of water purification from all heavy metals;

- increase the transparency of purified water up to 24-30 cm;

- increase the content of dissolved oxygen in water to 4.2-6 mg / l. In addition, the inventive method of treating man-made waters is safe and technologically simple to implement, allows you to dispose of solid household waste polyethylene glycol terephthalate (PET containers), as well as to obtain marketable products consisting of valuable metals for the production needs of metallurgical enterprises.

Using the inventive method for purifying man-made waters with technological regimes that go beyond the stated limits is impractical, since the quality of the water being purified is significantly reduced (experiments No. 10-15).

Thus, the claimed method can improve the quality of purified water, ensuring environmental safety of its use when discharged into natural and artificial water basins, as well as when using it in an industrial environment.

Claims (1)

A method for purifying man-made waters, including dissolving polyethylene glycol terephthalate in an organic solvent, feeding the resulting mixture into purified water and subsequent flotation of the treated water at pH 7-8 with separation of heavy metal ions, characterized in that the polyethylene glycol terephthalate is dissolved in glycerol in a ratio of 1: 1-1: 3, and in the purified water the resulting mixture is fed in an amount of 0.2-0.4 l / m ³ .