RU2182130C2 - Method of treatment of sewage containing copper ions - Google Patents

Abstract

FIELD: metallurgy, ecology. SUBSTANCE: invention relates to utilization of waste containing copper ions from galvanic and other kinds of manufactures and can be used in metallurgy and other kinds of manufacture. Method involves the contact of sewage containing copper ions with natural calcium carbonates followed by treatment of precipitate by live steam, water slaking and granulation. Obtained precipitate is fixed on gypsum- carbonate matrix. Obtained precipitates can be stored for a long time and for the secondary using in nonferrous metallurgy plants. EFFECT: improved and simplified method of treatment.

Description

 The invention relates to chemical technology, namely to the disposal of liquid waste from galvanic and other industries containing copper ions, and can be used in metallurgical, metalworking and other industries for the treatment of wastewater from copper and to increase the chemical stability of precipitation obtained during long-term storage, and to enable recycling of precipitated copper.

 Most modern methods of wastewater treatment from heavy non-ferrous metal ions are based on their precipitation in the form of hydroxides during alkalization, followed by coagulation, separation of the precipitate and post-treatment [1]. Hydrolytic methods have sufficient deposition rate and depth, however, when disposing of sediments, problems arise associated with leaching of ions with weakly acidic natural waters during their long-term storage, especially in open areas.

There is a method of increasing the stability of precipitation of hydroxides due to their ferritization during oxidation of ferrous sulfate with oxygen in the presence of potassium permanganate or its mixture with pyrolusite at pH 10-11 (sparging the suspension with air at a temperature of 85-95 ^o C) [2]. Ferrites of non-ferrous metals are resistant to atmospheric and hydrospheric effects, however, the secondary use of copper is difficult due to its low content in the sediment. The disadvantages of this method are the use of an expensive reagent (permanganate), the high cost of alkalizing and heating solutions, complicated hardware design.

 A known method of treating wastewater from copper by treatment of solutions with a suspension of limestone and cement clinker with a concentration of at least 1 wt.% [3], with the deposition of copper in the form of double salts: calcium aluminum silicates, practically insoluble in any salt composition of water. The advantages of this method is to carry out the process in one stage without preliminary alkalization and the possibility of long-term storage of the formed cement stone in natural conditions. Disadvantages - the use of a rather expensive reagent (cement clinker - not less than 30%), the need to thicken fine precipitates and the inability to reuse the deposited metals due to their low concentration in the silicate matrix, and its applicability only in slightly concentrated solutions (1% suspension) . This method is selected for the prototype.

The aim of the invention is to simplify the process, reduce costs and obtain precipitation suitable for long-term storage and recycling in non-ferrous metallurgy. This goal is achieved in that the deposition of copper is carried out by contacting the wastewater with natural calcium carbonates, and the precipitate, unlike the prototype, is not fixed in a calcium silicate (cement), but in a gypsum carbonate matrix by its additional treatment with hot steam followed by mixing with water and granulation. In this case, a gypsum binder is not added, but is formed directly during the deposition of copper from acidic and neutral solutions on natural calcium carbonates:
3CaCO ₃ + 4CuSO ₄ + 10H ₂ O = Cu ₄ SO ₄ (OH) ₆ • H ₂ O + 3CaSO ₄ • 2H ₂ O + 3CO ₂
The precipitant is used repeatedly, which allows to obtain precipitation highly concentrated on copper. After the precipitator's resource is developed, the precipitate is a mixture of basic copper sulfates, gypsum and calcite residues (gypsum-limestone mixture) with a copper content of 10-30%.

The resulting mixture is treated with hot steam at a temperature of 145-160 ^o With, as a result of which the two-water calcium sulfate goes into semi-water, which has astringent properties, and the main copper sulfate - in copper oxide, stable under natural conditions. After cooling, the resulting material is closed with water in the usual ratio for typical binders, pelletized and sent for storage. In the resulting granules, copper is bound into oxide, which determines its increased resistance to leaching during long-term storage. The impact of slightly acidic soil water is compensated by a gypsum carbonate buffer, fixing the pH at a level of 6.4-6.6, at which dissolution of copper oxide is excluded. Additional binder application during pelletizing is not required since sufficient mechanical strength of the granules is provided by a gypsum binder formed during the deposition of copper.

 The high concentration of copper in the granules makes it possible to recycle it at non-ferrous metallurgy enterprises as an additive to the charge of reflective or other smelting. The mechanical strength of the granules determines the possibility of their long-term storage and convenient transportation over long distances. The presence in the granules of carbonate and calcium sulfate provides an additional reduction in the consumption of fluxes during melting.

 An example of a specific implementation of the method.

1. To the wastewater of the etching line of duralumin rolled products without preliminary alkalization, ground limestone is added in an amount depending on the copper content in the solution. At the end of the reaction (upon reaching a residual copper concentration below 0.01 mg / l), the precipitate is separated from the solution and treated with direct steam (145-160 ^o C) without preliminary drying. The resulting loose mass containing semi-aqueous calcium sulfate and up to 30% copper in the form of oxide is closed with water at a water-solid ratio of 1: 5-1: 2 and granulated. The obtained gypsum carbonate granules are sent for long-term storage or processing.

2. The copper deposition reactor, which is a column filled with crushed to 2-5 cm limestone, onto which the copper wastewater circuit is closed, is built into the current galvanic production flow chart. When the solution is filtered through a layer of limestone, copper is precipitated as basic sulfate. The copper content in the water leaving the column is below the detection limit by atomic absorption method. The operation of the column is carried out until the life of the precipitant is determined, which is determined by the appearance of copper in the wash water at the outlet, after which the column is dried and blown from below with hot steam to heat the material filling the column to a temperature of 145-160 ^o С. The resulting mass is unloaded, shut off with water at W: T = 1: 6 ÷ 1: 2 and pelletized on a disk or other granulator. Granular material is sent for long-term storage in a dump or for metallurgical processing. The column is filled with a fresh portion of limestone, the technological cycle is repeated.

References
1. Kogan B. I. Modern methods of wastewater treatment from heavy metal ions. Overview inf. Institute "Color Metinformation". Series "Environmental Protection". - M., 1975.

 2. Copyright certificate 1549925.

 3. Copyright certificate 1214605.

Claims (1)

 A method of treating wastewater containing copper ions, including its deposition on natural calcium carbonates, characterized in that the precipitate is subjected to direct steam treatment followed by mixing with water and granulation.