RU2478575C1 - Method of producing solid aluminium chloride-containing coagulant - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to chemistry. Solid aluminium chloride-containing coagulant is obtained from a liquid colloidal solution of aluminium hydrochloride via reaction thereof with acetone in weight ratio of acetone to water in the aluminium hydrochloride solution of 1:(0.17-0.27) at room temperature. The method enables to turn liquid aluminium hydrochloride into a solid state at room temperature.

EFFECT: invention enables to obtain solid aluminium hydrochloride with an improved cost/performance ratio.

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Description

The invention relates to methods for producing a coagulant based on basic aluminum chlorides. This coagulant can be used to purify natural and wastewater from suspensions and dissolved organic and inorganic substances.

A known method of producing aluminum hydroxychloride, which consists in the processing of aluminum metal with hydrochloric acid of various concentrations (AS USSR, No. 618343, class C01F 7/56, publ. 05.08.78).

However, in this case, liquid GOHA is obtained, which has increased corrosion activity due to free hydrochloric acid formed due to the hydrolysis of GOA. This requires the use of special return packaging packaging, causing many problems when delivering it to the place of consumption.

To eliminate these inconveniences, it is necessary to convert the coagulant into a more convenient solid form.

A known method of producing solid GOA by periodically heating to 70 ° C followed by cooling to 0 ° C of an aqueous solution of aluminum chloride. Over time, at 30-40 ° C, solid GOHA is released (Patent No. 49-43478, Japan, publ. 11/21/1974).

The disadvantage of this method is the high energy costs associated with the need for both heating and cooling the reaction mass, which also increases the duration of the process to obtain the final product.

There is also known a method for producing solid GOHA by boiling a solution of aluminum chloride for 2-4 hours, followed by spray drying (US Patent No. 3,094,741, publ. 09.09.70).

The disadvantage of this method is the use of special equipment for drying a liquid product, high energy costs and a long time to transfer GOHA from a liquid to a solid state.

The closest is a method for producing solid GOHA by treating a liquid solution of aluminum hydroxide with sulfates or metal chlorides or natural bischofite (Patent RU No. 2210539, MKI C01F 7/58, 7/00, publ. 08/20/2003, bull. No. 23).

The reasons that impede the achievement of the required technical result when using known methods include the following:

firstly, the addition of various salts increases the cost of a solid product;

secondly, all available moisture in the initial liquid aluminum hydroxychloride (54-70%) in the bound state remains in the finished product, which increases transport costs for the delivery of GOX to its place of use;

thirdly, when using sulfates and metal chlorides, as well as natural bischofite as gel-forming components, an increase in salt content in the treated water is observed, leading to stabilization of suspended particles due to adsorption, which requires an additional consumption of GOA;

fourthly, the dosage interval decreases, which either leads to stabilization of the dispersion or to a sharp increase in the hydrolysis rate of GOX due to an increase in the ionic strength of the solution at the stage of introducing the coagulant and mixing. The resulting floccules from the products of GOX hydrolysis and the dispersed phase of the purified water are destroyed, it is difficult to settle in sedimentation tanks. This results in reduced filter performance. In addition, the filter cycle time is drastically reduced;

fifthly, some metal sulfates and chlorides and natural bischofite, introduced into GOHA to put it in a solid state, give it hygroscopicity, which leads to caking during prolonged storage under adverse conditions.

The present invention solves the important task of developing a cost-effective method for producing solid basic aluminum chloride, used as a coagulant for the purification of natural and wastewater from suspensions and dissolved organic and inorganic substances.

When implementing the proposed method for producing solid basic aluminum chloride, the following technical result is obtained:

firstly, the absence of crystallization water in the composition of solid GOHA obtained by this method improves its technical and economic indicators, because to obtain high quality water treatment, smaller doses of coagulant are required;

secondly, the process of obtaining a solid product proceeds at room temperature, which does not require additional energy costs;

thirdly, this coagulant does not additionally introduce substances into the purified water that impair the quality of the treatment (in particular, it does not increase its salinity), because unlike the prototype does not contain as gelling components of various salts.

The specified technical result in the implementation of the invention is achieved by the fact that a liquid colloidal solution of aluminum hydroxochloride (GOHA) is subjected to interaction with acetone in a mass ratio of acetone: water in a solution of GOHA equal to 1: (0.11-0.27), respectively, at room temperature.

When a colloidal solution of GOXA with a dynamic viscosity of 90-180 Pa · s is added to acetone in various quantities, an increase in the viscosity of GOXA is observed, and when an optimal dose of GOXA (the claimed ratio) is added, it goes into a solid state.

The process of obtaining solid coagulant proceeds at room temperature without energy consumption for a short time (2-7 minutes). The resulting product is easy to tablet, which is convenient for individual use in extreme conditions for drinking water.

Liquid chloroaluminous coagulant is obtained by the interaction of aluminum with hydrochloric acid. 1.5 L of 10% hydrochloric acid was added to a 2 L flask equipped with a reflux condenser and granulated aluminum was added in portions until the dynamic viscosity of the solution was 90-180 Pa · s. The temperature of the dissolution process is 70-95 ° C. In our case, for further studies, a high viscosity liquid GOHA colloidal solution was obtained having the following parameters: content of the main substance (polymer Al ₂ (OH) ₅ Cl) 54%, which is 10.6% for aluminum and 5.5% for chloride ions; the percentage ratio in the main product was equal to Al ³⁺ : Cl ^- = 1: 0.519.

The method is as follows.

The obtained colloidal solution of GOX is transferred to a solid state by adding it to acetone with stirring for uniform distribution throughout the volume.

The invention is illustrated by the following examples.

EXAMPLE 1. In this example, the preparation of solid GOA is determined by converting it from a liquid colloidal state to a solid state under the action of acetone.

In a glass with a capacity of 200 ml, 100 ml (79 g) of acetone are added and various amounts of GOA are added to it according to Table 1. Mixing temperature 20 ° C.

From table 1 it is seen that the degree of conversion of GOHA from a liquid to a solid state is strongly affected by the amount of acetone present in the mixture.

Table 1 The effect of the ratio in the acetone: water system on the formation of solid GOHA No. p / p The mass of the GOX solution (g) added to 100 ml of acetone The mass of water (g) introduced with GOHA The ratio of acetone: water, parts by weight Note one 19,2 8.8 1: 0.11 98.6% solid GOA is formed 2 29.6 13.6 1: 0.17 95.7% solid GOA is formed 3 46.1 21,2 1: 0.27 88.7% solid GOA is formed four 62.6 28.8 1: 0.36 The system is divided into two phases: 54% sediment and gel 5 76.9 35,4 1: 0.45 The system was divided into two phases: 27% sediment and a highly viscous gel, which has great adhesion to glass and filter material

Incomplete isolation of solid GOA is observed in those cases where the action of water prevails, because in water, as in a more polar solvent, the solubility of GOA is high.

Upon reaching the acetone: water ratio from 1: 0.11 to 1: 0.27 (experiments 1-3), solid GOHA is released, which is well filtered. In this case, the degree of transition of GOX to the solid state is high.

When the acetone: water ratio is from 1: 0.36 to 1: 0.45, the amount of precipitate formed sharply decreases, and adhesion to glass and filter material increases. This indicates that the concentration of water in the system exceeded the concentration of acetone and the solubility of GOA decreased significantly, so it remains in solution, forming a highly viscous gel. That is, when the ratio of acetone water is higher than 1: 0.27, a large amount of GOHA (50-80%) remains in solution and is taken out together with the filtrate. This is due to the fact that acetone evaporates faster than water and in this heterogeneous system the water concentration increases, the GOHA precipitate begins to dissolve and eventually disappears. As a result, GOHA is formed in the form of a highly viscous gel.

EXAMPLE 2. In this example, due to the constant composition of various fractions during the allocation of solid GOA.

In order to determine the possible change in the composition of GOA during its isolation from the solution with acetone, a chemical analysis of various fractions was carried out, the results of which are presented in Table 2.

table 2 The percentage of ions Al ³⁺ : Cl ^- in various fractions Fraction The content of components, wt.% The percentage ratio of Al ³⁺ : Cl ^- in the fraction Al ³⁺ Сl ^- Source 10.6 5.50 1: 0.519 GOX solution Solid GOHA isolated 22.1 11.50 1: 0.520 acetone Filtrate 0.1 0.056 1: 0.560

As can be seen from table 2, the percentage ratio of Al ³⁺ : Cl ^- ions in the liquid and solid states is the same, i.e. treatment with acetone does not change the chemical composition of GOA. Analysis of the filtrate showed a slight increase in chloride ions in it compared to their initial concentration and concentration in the solid product. This may be due to the transition of a part of hydrochloric acid from the GOX solution to the filtrate.

Based on the above examples, it follows:

firstly, the method of producing solid chloraluminium-containing coagulants, which consists in mixing a liquid colloidal solution of GOHA with acetone, allows one to obtain solid GOHA without crystallization water in the composition, which sharply reduces the cost of transportation costs for delivering the coagulant to its place of use;

secondly, the resulting product has the best technical and economic indicators, because the absence of crystallization water in its composition allows to reduce the dose to obtain high quality water treatment;

thirdly, in comparison with the prototype, the salinity in it does not increase when treating water, since acetone does not dissociate into ions;

fourthly, in contrast to the prototype due to the lack of additional inorganic salts in the resulting product, it does not have increased hygroscopicity, which allows it to be stored for a long time under adverse conditions.

Claims (1)

A method of obtaining a solid chloroaluminous coagulant from a liquid colloidal solution by converting it to a solid state, characterized in that the aluminum hydroxochloride solution (GOXA) is reacted with acetone in a mass ratio of acetone: water in a GOXA solution of 1: (0.11-0, 27), respectively, at room temperature.