RU2641930C2 - Method of clearing water from sulphates by reagent method - Google Patents

Abstract

FIELD: mining.

SUBSTANCE: water is treated with lime and an alumina-containing component, after which water is treated with calcium hydroxy aluminate in an amount necessary to effectively bind the sulfates, and aluminium hydroxide, which co-precipitates calcium sulfate and calcium hydroxy aluminate in an alkaline environment. The water is clarified by settling and filtration.

EFFECT: increasing the efficiency of water purification from sulfates with effective water softening, which leads to a significant decrease in the level of mineralization of the treated water.

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Description

The present invention relates to methods for purifying water from hardness ions and sulfate ions and can be used in the mining, processing industry, utilities and energy for the purification of mineralized sulfate-containing waters with high hardness.

Known reagent methods for purifying water from sulfates, based on the treatment of water with lime and aluminum coagulants (Salnikova E.O., Selection of a precipitant during wastewater treatment from calcium sulfate / E.O. Salnikova, O.G. Peredery // Non-ferrous metals, - 1983 . - No. 12. - p. 22-24).

The disadvantages of such methods include secondary pollution of water with chlorides when using aluminum hydroxochlorides and sodium ions when using sodium hydroxoaluminate. When using sodium hydroxoaluminate, significant alkalization of water occurs.

The closest in technical essence to this invention is a method of purifying water from sulfates using lime and amorphous aluminum hydroxide (RU 2322398, IPC C02F 1/66 (2006.01), C02F 1/57 (2006.01), publ. 04/20/2008). The disadvantages of this method include the use of freshly precipitated aluminum hydroxide. This reagent quickly loses its reactivity, and when it is obtained by hydrolysis of aluminum salts, saline waste forms that are difficult to dispose of. In addition, after treating the water with lime and aluminum hydroxide to neutralize the water, carbon dioxide or air is blown through it, which greatly complicates the technology.

The basis of the invention is the task of effectively purifying water from sulfates with effective softening of water, which will significantly reduce the level of mineralization of water.

The problem is solved in that in the method of softening and purifying water from sulfates, including treating water with lime and aluminum hydroxide, in accordance with the invention, after treating the water with lime, sodium hydroxoaluminate and aluminum hydrochloride are added to it. The water is clarified by settling and filtering.

The essence of the method lies in the fact that, by choosing the ratio between sodium hydroxoaluminate and aluminum hydroxochloride, the content of chloride and sodium ions in purified water can be controlled by adding the amount of aluminum component (hydroxoaluminate) necessary for the effective binding of sulfates. At the same time, in an alkaline medium, aluminum hydroxochloride is converted to calcium hydroxoaluminate, which improves the efficiency of purification from sulfates due to the coprecipitation of calcium sulfate and hydroxyaluminate. This contributes not only to an increase in the efficiency of sulfate removal and water softening, but also leads to a decrease in the pH of the medium without using carbon dioxide.

The method is implemented as follows. Lime, sodium hydroxoaluminate and aluminum hydroxo chloride were added to the water with stirring. The solution was stirred for two hours. The precipitate was separated by settling. The clarified water was filtered, the filtrate was analyzed for sulfates, chlorides, and stiffness ions and the residual alkalinity of the solution was determined. The effectiveness of water purification by the proposed method and the effectiveness of its softening can be judged from the above example.

Example. Before samples of concentrates formed during the treatment of mine water by the baromembrane method ([SO ₄ ^2- ] = 26.2-65.0 mEq / dm ³ , W = 24-36 mEq / dm ³ , [Cl ^- ] = 87.0 mEq / dm ³ , U = 3-20 mEq / dm ³ , mineralization (M) = 2200-6700 mg / dm ³ ) with a volume of 1 dm ^{3, the} calculated amount of lime, sodium hydroxoaluminate and 2 were added with stirring / 3 aluminum hydroxychloride (in some cases 5/6 aluminum hydroxychloride). The mixture was stirred for two hours and settled for three hours. The clarified water was filtered. In purified water, the residual content of sulfates, chlorides (or mineralization), residual hardness and alkalinity were determined. The results obtained using 2/3 of aluminum hydroxychloride are shown in table 1, using 5/6 of aluminum hydroxychloride are shown in table 2.

Claims (1)

A method for purifying water from sulfates by the reagent method, including treating water with lime and an aluminum-containing component, characterized in that after treating the water with lime, the amount of sodium hydroxoaluminate necessary for effective binding of sulfates and aluminum hydroxochloride, which precipitates calcium sulfate and calcium hydroxoaluminate in an alkaline medium .