RU2529536C2 - Method of producing water-soluble reagent for treating natural and waste water and separating phases - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention can be used to treat low-turbidity water, in treating water for household purposes from natural surface sources, in treating industrial waste water with high content of a dispersed phase from suspended matter, petroleum products, fat, protein and other impurities of mineral and organic nature. The method is carried out by mixing (0.1-0.2)% aqueous solution of a weakly charged polycationite with a cationic charge (1.65-9.23) with an aluminium salt, taken in the form of aluminium pentahydroxochloride sol in molar ratio Al³⁺:polycationite link equal to (2-6:1).

EFFECT: method improves efficiency of using high-molecular polyelectrolytes and reduces the dosage thereof while improving degree purity of water.

2 dwg, 5 ex, 5 tbl

Description

The invention relates to methods for producing water-soluble reagents used for the purification of natural and wastewater from suspensions, petroleum products, fatty, protein and other pollution of mineral and organic origin. The proposed reagent can be used both for the treatment of low-turbid waters, for example, for the preparation of household water from natural surface sources, and for the treatment of wastewater with a high content of the dispersed phase, for example, for the treatment of industrial wastewater and for the treatment of domestic wastewater.

In the reagent technology of water treatment and water purification, the efficiency of the process is determined by the degree of purification of water from impurities, the duration of the process of sedimentation of impurities, the duration of the filtering cycle of purified water and other factors. One of the main ones is the dose of the reagent, which must be minimal in order to achieve a sufficient degree of purification, which is determined not only by economic considerations, but also by the requirements of the inspecting authorities for the quality of purified water, as well as sanitary standards for the residual amount of reagent in purified water. From these positions, the dose of the reagent should be minimal, but providing standards for purified water [Ksenofontov B.S. Water use and treatment of industrial waste // Life safety. - 2003. - No. 9. - S.1-10].

The magnitude of the required dose of the reagent depends on its activity associated with the chemical structure of the reagent and the mechanism of its interaction with colloidal impurities. The most common water-soluble reagents include inorganic salts of iron and aluminum, as well as water-soluble polymers of organic nature [Zapolsky AK, Baran A.L. Coagulants and flocculants in water purification processes. L .: Chemistry. 1987]. First, by neutralizing the surface charge of colloidal particles, they destabilize the disperse system, which is natural surface water and most wastewater, which leads to the formation of "primary" particles in the treated water.

The second - water-soluble organic polymers - combine particles into large flocs, helping to accelerate their sedimentation. Among the water-soluble polymers used for these purposes, a significant place is occupied by acrylamide copolymers having ionic groups, the so-called polyelectrolytes [Butova S.A. Reference manual, ed. A.I. Krotova. M .: Stroyizdat. - 1997. - 196 p.].

However, the separate use of these two reagents in the purification process is associated with a number of technical difficulties and may be accompanied by both a synergistic and antagonistic effect during purification [V. A. Softenkov, G. V. Bulidorova. Chem. and technol. water. 1997.V.17. No. 5. S.583]. One way to solve this problem is to create composite reagents that combine the properties of an inorganic coagulant and an organic polymer flocculant.

It is known to use compositions of aluminum chloride with one of the water-soluble cationic amine-type polymers for treating water with a low suspension content (less than 0.1%) [Pat. 341357 EPO, C02F 1/52, 1989].

The disadvantage of this method is the use of aluminum chloride and an organic polymer, which by toxic properties cannot be used to prepare household water, and the marked synergistic effect during coagulation is observed only in the case of low turbidity dispersions (4.0-4.5 turbidity units).

A known method of obtaining a water-soluble reagent by polymerization of acrylamide under the action of a radical initiator in an aqueous solution of aluminum hydroxochloride. The process is carried out at temperatures of 60-90 ° C in a certain range of hydroxyalkyl tert-butyl peroxide-iron ratios and with an acrylamide content of aluminum oxychloride from 3.2% wt. up to 34.9% wt. [Pat. 2174105 RF, C02F 1/52, C02F 1/56, C02F 103/02, 09/27/2001].

The disadvantages of this method include the following:

- the reaction of obtaining a reagent requires the use of heat exchange equipment, the use of a coolant, the energy consumption of the process;

- insufficiently high molecular weight of the polymer product (as evidenced by the value of the characteristic viscosity [η] ≤ 2.85) is the reason for the low efficiency of the reagent in the process of flocculation of suspensions.

The closest is a method of obtaining a water-soluble reagent by mixing aluminum oxychloride with an aqueous solution of polyacrylamide (PAA) of molecular weight 3 · 15 ⁵ ÷ 2 · 10 ⁶ with a molar ratio of Al ³⁺ : polyacrylamide unit equal to (2 ÷ 4): 1 [Pat. 2288181 RF, C02F 1/58, B01D 21/01, 11/27/2006]. At the same time, a sol of highly basic aluminum pentahydroxochloride (PHCA) containing colloidal particles of polynuclear aluminum complexes is used as aluminum oxychloride. As a result of the cooperative reaction of particles with polyacrylamide macromolecules, a polymer-colloidal complex is formed that combines the properties of an inorganic coagulant and an organic polymer flocculant.

The disadvantage of this method is the use of nonionic polyacrylamide of low molecular weight, while it is well known that the increased molecular weight of the organic flocculant is the primary factor affecting the efficiency of flocculation.

Polyacrylamide is mainly used for cleaning dispersed systems containing particles of a dispersed phase with a positive surface charge, such as kaolin.

In modern water treatment practice, ultra-high molecular weight polyelectrolytes (molecular weight 10 ÷ 20 · 10 ⁶ ) are widely used, which include nanogenic groups - polycationites and polyanionites [Gandurina L.V. Wastewater treatment using synthetic flocculants. M .: Publishing. CJSC “Dar Vod. geo". - 2007. - 198 p.].

Polyelectrolytes have a much wider spectrum of action and are effective in treating waters containing not only inorganic suspensions, but also organic pollutants (phytoplankton). However, polyelectrolytes used in pure form are not effective in the case of complex dispersed systems - wastewater containing fats, hydrocarbons, oil and oils, forming stable hard-to-break dispersions in the form of emulsions. In such cases, inorganic aluminum salts are added simultaneously or alternately to the water to be purified to increase the cleaning efficiency. Such a two-reagent wastewater treatment method inevitably leads to a complication of the technological solution of the treatment process and introduces an additional risk of error with respect to compliance with the technological parameters.

The present invention solves the important task of increasing the efficiency of high molecular weight polyelectrolytes in the processes of water treatment and water purification in order to reduce their dose while increasing the degree of water purification.

The technical result achieved is achieved in a method for producing a water-soluble reagent for purification of natural and waste waters and phase separation by mixing an aqueous polymer solution with an aluminum salt taken in the form of an aluminum pentahydroxochloride sol, characterized in that (0.1 ÷ 0.2) is used as the polymer % aqueous solution of a lightly charged polycationite with a cationic charge (1.65 ÷ 9.23) and they are mixed at a molar ratio of Al ³⁺ : polycationite unit equal to (2 ÷ 6: 1).

In the process of implementing the proposed method, the interaction between the polyelectrolyte and colloidal particles of the sol of polyhydroxychloride aluminum occurs due to non-covalent bonds of the reaction centers of the polyelectrolyte macromolecules with the surface of positively charged nanosized particles of the PHCA sol and leads to the formation of mixed organo-inorganic polycomplexes. The interaction of polyelectrolyte macromolecules with sol particles occurs at the molecular level, and the cooperative nature of the resulting chemical bonds ensures high stability of the resulting polycomplexes, which are individual compounds. The formation of polycomplexes occurs spontaneously with simple mixing of their aqueous solutions.

The interaction of positively charged colloidal particles of the pentahydroxochloride sol with negatively charged groups of polyanionites is very strong and leads to the formation of insoluble polycomplexes. Interaction with fully or highly charged polycationites does not occur due to the repulsive forces of the same charged reagents. In the case of weakly charged polycationionites, the electrostatic repulsive forces become small due to the rare arrangement of cationic groups in the long chain of the polyelectrolyte and do not impede the implementation of other types of non-covalent bonds - hydrogen, donor-acceptor, van der Waals bonds, which ensure self-assembly of the polycomplex. The ultra-high molecular weight of the polyelectrolyte, which determines the presence of uncharged sections in the long polymer chain, promotes the formation of strong polycomplexes.

Polycomplexes of colloidal particles of PHA with macromolecules of polyelectrolytes are a hybrid reagent that carries the functions of an inorganic coagulant - a polyvalent metal and an organic flocculant - a high molecular weight polyelectrolyte and, therefore, can be used to clean both low-dispersion dispersions and highly concentrated complex dispersions.

The invention is illustrated by the following examples.

Example 1. In this example, due to the influence of the nature of the polyelectrolyte (table 1) on its ability to form soluble polymer-colloidal complexes with colloidal particles of PGA sol.

Table 1
Characteristics of Polyelectrolytes №№ Commercial name Molecular mass* [η] in 10% NaCl Ion charge mEq. one Praestol-611 BC ~ 6 · 10 ⁶ 7.54 6.52 2 Organopol 6405 - 11.71 1.65 3 Zetag-92 18 ÷ 20 · 10 ⁶ 18.12 9.23 four Praestol-2500 14 · 10 ⁶ - -1.10 5 Superflock-N300 16 · 10 ⁶ - -3.73 6 Magnaflock 10 20 · 10 ⁶ - -2.13 7 KF-99 1 · 10 ⁶ - 100.0 * according to the manufacturer

The interaction is carried out by mixing a dilute aqueous solution of the polymer with a PHCA sol, for which a 0.5% solution of PHCA is added dropwise to a solution of a polymer with a concentration of 0.02 g / dl in 1% NaCl. The titrant volume is converted to the molar ratio Al ³⁺ : polymer unit. An aliquot of the resulting mixture (5 cm ³ ) was taken into a cuvette and the optical density was determined using a Specol-1300 spectrophotometer at a wavelength of 540 nm. Figure 1 shows the light scattering curves for cationic polyelectrolytes - Praestol-611 BC, Organopol-6405, Zetag-92, anionic polyelectrolytes - Superflock-N300, Magnaflock-10 and non-ionic polymer - Praestol-2500. From the experimental data it follows that when a PHHA sol is mixed with anionic polyelectrolytes - Superflock-N300 and Magnaflock-10, a polycomplex that is insoluble in water forms. When a PHHA sol is mixed with cationic polyelectrolytes - Praestol-611 BC and Organopol-6405, as well as with the non-ionic polymer Praestol-2500, no precipitate is formed, which may indicate the formation of a soluble polycomplex.

Example 2. In this example, evidence of the formation of soluble polymer-colloidal complexes (PACs) is presented, based on the fact that if the interaction of particles of a PHA sol with macromolecules of a polyelectrolyte takes place, then it should be accompanied by the compaction of tangles of polymer macromolecules, which will lead to a decrease in the solution specific viscosity mixtures. The quantitative characteristic of this process is the parameter F = (η _exp. / Η _calc. ) -1, where

η _exp. the specific viscosity of the solution of the mixture of reagents,

η _exp. - the sum of the specific viscosities of aqueous solutions of the polymer and PHCA at the same concentrations, measured separately.

Figure 2 shows the dependence of the parameter F on the molar ratio of Al ³⁺ : polycationite unit for cationic polyelectrolytes: Praestol-611 BC, Organopol-6405, Zetag-92 and for fully charged (100% cationic groups) polycationite - KF-99. As follows from these data, with an increase in the cationic charge, an ever smaller decrease in the specific viscosity is observed, and for a fully charged KF-99, the viscosity does not change at all, i.e. the interaction of PHCA particles with polymer macromolecules does not occur. Evidence of the formation of polycomplexes with lightly charged polycationites is an elemental analysis of the reaction products isolated from the reaction mixture (table 2). For this purpose, a concentrated solution of NaCl (30% by mass) is added to the solution of the mixture of reagents. In this case, the complex will precipitate from the solution. It is separated by centrifugation, dried and analyzed for aluminum content.

table 2
The aluminum content in the PAC depending on the molar ratio of the reactants in the mixtures of PHCA and polyelectrolyte No. Al ³⁺ molar ratio: polyelectrolyte unit Al ³⁺ (%) Praestol-611BC Organopol-6405 Zetag-92 one 0.2: 1 - - 1.9 2 0.5: 1 3.5 5.9 2.5 3 1.1 4.6 6.3 7.5 four 2.1 7.6 11.1 12.3 5 4.1 12.0 12.1 12.7 6 6.1 12.1 12.2 12.7 7 10.1 12.5 12.2 12.7

From the data of Table 2 it follows that the Al ³⁺ content in polycomplexes increases with an increase in the Al ³⁺ : polyelectrolyte unit ratio, reaching a maximum for a ratio of 2: 1 ÷ 4: 1 for different polycationites. A further increase in the amount of PHCA does not lead to a change in the composition of the polycomplex, and the polycomplex and excess salt of PHCA will be in the solution.

Example 3. In this example, the use of polymer-colloidal complexes based on lightly charged polycationites as flocculants in the separation of concentrated dispersions is caused. To evaluate the effectiveness of the reagents, the spectrophotometric method is used, in which the absorbance of the supernatant is measured after a certain dispersion settling time with and without flocculant added. After that, the dimensionless parameter is calculated - the clarification effect:

, $$E_{\mathrm{about}\mathrm{from}\mathrm{at}.}=\frac{{\mathrm{<figure-callout\; id="0"\; label="\tau \; D"\; filenames="00000003.png,00000004.png"\; state="\{\{state\}\}">\tau \; </figure-callout>}}_D^{}}{{\tau }_D}-\mathrm{one}$$

,

, τ_D - оптическая мутность насадочной жидкости после осаждения без добавления и при добавлении реагента [Новаков И.А., Радченко С.С., Радченко Ф.С. Журнал прикладной химии. 2004. Т.77. №10. С. 1699].Where $${\tau }_{\mathrm{<figure-callout\; id="0"\; label="D"\; filenames="00000003.png,00000004.png"\; state="\{\{state\}\}">D</figure-callout>}}^0$$

, τ _D is the optical turbidity of the packed liquid after deposition without addition and with the addition of a reagent [Novakov I.A., Radchenko S.S., Radchenko F.S. Journal of Applied Chemistry. 2004. V.77. No. 10. S. 1699].

Flocculation of kaolin dispersion is carried out in the mode of free deposition, pre-determine the optimal dose of reagents, which is 6 mg / DM ³ . Table 3 shows the values of E _ov. for low-charged polyelectrolytes and their polycomplexes with particles of PHCA sols for various compositions of the corresponding polycomplexes.

Table 3
Effects of clarification ( _Osw. ) _Upon flocculation of kaolin dispersion (0.6 wt.%) With polycationionites and their polycomplexes with PLCA sol at various Al ³⁺ ratios: polycationite unit (mol.) The ratio of Al ³⁺ : polycationite link, mol. E _con. for polycationites and their polycomplexes Praestol-611 BC Praestol-851 BC Organopol-6400 Organopol-6405 0: 1 190 170 130 170 1: 1 250 180 320 380 2: 1 370 300 415 560 3: 1 520 410 400 680 4: 1 780 600 370 370 5: 1 260 280 280 215 6: 1 240 170 200 -

The data in Table 3 show that the polycomplexes of lightly charged polycationites in flocculating ability significantly exceed individual polycationites (E _{ov. =} 415 ÷ 780 against 130 ÷ 190). Moreover, polycomplexes are more active at Al ³⁺ : polymer unit ratios of 2: 1 ÷ 4: 1 (mol.) For various polycationites, which corresponds to the optimal composition determined by the chemical method (table 2).

Example 4. In this example, the use of polymer-colloidal complexes based on lightly charged polycationites with their optimal composition (Al ³⁺ : polycationite unit) as flocculants in the separation of a concentrated dispersion of kaolin (0.6 wt.%) In comparison with polyacrylamide and its polycomplex with particles of PGA sol (prototype). Flocculation is carried out analogously to example 3 (table 4).

Table 4
Effects of clarification ( _Osw. ) _Upon flocculation of kaolin dispersion (0.6 wt.%) Of the polyacrylamide polycomplex (prototype) and lightly charged polycationites with their optimal composition (Al ³⁺ : polymer unit) The ratio of Al ³⁺ : polymer unit, mol. E _con. for polymers and their polycomplexes * Polyacrylamide Praestol-611 BC Praestol-851 BC Organopol-6400 Organopol-6405 0: 1 twenty - - - - 2: 1 205 - - - - 0: 1 - 190 - - - 4: 1 - 780 - - - 0: 1 - - 170 - - 4: 1 - - 600 - - 0: 1 - - - 130 - 3: 1 - - - 400 - 0: 1 - - - - 170 3: 1 - - - - 680 * flocculant dose - 6 mg / l

As follows from these data, the polycomplexes of lightly charged polycationionites significantly exceed the polyacrylamide-based polycomplex in flocculating activity.

Example 5. In this example, the use of PAC in the process of coagulation of a low-concentration dispersion that simulates natural water is caused. The dispersion is prepared on the basis of 0.8% kaolin dispersion, which is upheld for 24 hours. The upper layer is decanted and sedimentation analysis is carried out, according to which the content of the dispersed phase in the dispersion is 30-40 mg / dm ³ , the particle size of the dispersed phase lies in the range of 1.6-2.5 μm. The effectiveness of coagulants is evaluated by the change in the turbidity of the water after treatment with reagents. Table 5 presents data on changes in the turbidity of kaolin dispersion depending on the type of coagulant.

Table 5
The change in turbidity of the model of low concentrated kaolin dispersion after processing it with reagents. Dose - 10 ml / l. The initial turbidity τ ₀ = 40.0 ml / L. Reagent (polycomplex based on polycationite) Turbidity after treatment with reagent, mg / l The degree of purification,% Polyacrylamide (prototype) 9.5 76,2 Praestol-611 BC 1.8 95.5 Praestol-851 BC 2.1 94.7 Organopol-6400 2.2 94.5 Organopol-6405 2.0 95.0

Thus, polymer-colloidal complexes of weakly charged polycationites with particles of PHCA sols are effective reagents in the purification of both concentrated dispersions and low-haze kaolin dispersions.

Claims (1)

A method of obtaining a water-soluble reagent for purification of natural and wastewater and phase separation by mixing an aqueous polymer solution with an aluminum salt taken in the form of an aluminum pentahydroxochloride sol, characterized in that (0.1 ÷ 0.2)% aqueous solution is used as the polymer lightly charged polycationion with a cationic charge (1.65 ÷ 9.23) and mix at a molar ratio of Al ³⁺ : polycationite link equal to (2 ÷ 6: 1).

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