RU2061660C1 - Method for treatment of sewage water to remove ions of heavy metals - Google Patents

Abstract

FIELD: treatment of sewage water to remove ions of heavy metals. SUBSTANCE: to remove ions of heavy metals and chromium (YI), sewage water is subjected to two-stage electrochemical treatment with different materials of galvanic pairs, and settling after each stage and separate regulation of pH at the stage of electrochemical cleaning and settling. EFFECT: higher efficiency.

Description

 The invention relates to wastewater treatment technology, and in particular, to methods for wastewater treatment from heavy metal ions, including chromium / VI /.

 In recent years, effective and economical methods of galvanochemical treatment have been used to treat wastewater from heavy metal ions.

 A known method of purification of acidic electrolytes containing ions of chromium / VI /, copper, zinc, as well as chromium / VI /, copper and ammonium in a chip reactor, which contains steel and copper chips in a ratio of 3: 1. The chip reactor is a rotating drum mounted in a special container to separate the reacted chips. / N.I. Bunin. Neutralization of spent electrolytes in galvanic production in chip reactors. Mater. Semin. / Environmental Protection environment from waste galvanic. pr-va. Knowledge Island, Mosk. DNTP M, 1990, p. 60-64 /. After separation of the precipitate in the filter unit, it is necessary to purify the filtrate in the reaction chambers with the supply of electro-generated iron hydroxide / II /.

 The effectiveness of treatment by a known method depends, as the author has shown, on the composition of the wastewater; in addition, the second stage of purification requires energy and is associated with the additional introduction of iron ions into the treated water.

 There is also known a method of treating wastewater from chromium ions and heavy metals by filtering through a special particle feed from a mixture of two types of metals in order to remove ions of trivalent chromium and iron and subsequent processing for 30-40 minutes in the electrodialysis apparatus. / N. E. Korobchanskaya, A. Ya. Shostenko, R.V. Vergunova. A closed water supply system for galvanic production is an effective factor in protecting the environment from galvanic production waste. Mater.semin. / Environmental protection from waste galvanic. pr-va. Knowledge Island, Mosk. DNTP-M, 1990, p. 30-35 /.

 This method is structurally complex and also requires additional energy costs.

A known method of wastewater treatment from ions of heavy metals and chromium / VI / by their two-stage galvanochemical treatment / Inform. leaflet on scientific and technological achievement N 89-34. Method of galvanochemical wastewater treatment. Chelyabinsk Interdisciplinary Territorial Center STIP, 1989 / - prototype. The first stage of purification of averaged acid-base and chromium-containing wastewater from chromium / VI / is carried out continuously in the presence of iron-copper scrap with a mass ratio of 4: 1. Then, in a pre-assembled capacity, the pH of the wastewater is adjusted to 5-6, and the temperature is up to 40-50 ^o C. To increase the degree of purification, the wastewater is re-passed through a step reactor with the same load / second stage /. Polyacrylamide is used to intensify the deposition process.

 The disadvantages of this method include the lack of significant differences in the conditions of water treatment at each stage of a two-stage treatment scheme, i.e. in the known method, wastewater is treated at each stage of galvanochemical treatment in a field of equal galvanic couples, both stages of treatment are carried out in an acidic or neutral pH region, which reduces the possibility of effective treatment of ions of various heavy metals, leads to an increased residual content of iron ions in purified water and sediment volume, since the optimal conditions for the precipitation and flocculation of hydroxides are not observed. In addition, the hydroxides formed in the first stage of purification do not separate, but enter the chip reactor of the second degree, where they slow down the process of galvanocoagulation by their presence. The implementation of the method requires maintaining a relatively high temperature of the treated wastewater, which is associated with additional energy costs.

 The aim of the present invention is to increase the degree of purification and reduce energy costs.

 The goal is achieved in that the wastewater from heavy metal ions and chromium / VI / is carried out by galvanochemical treatment in two stages with different materials of galvanic couples, settling at each stage and separate pH control at each stage of treatment. The entire cleaning process is carried out without additional heating of the wastewater.

 The proposed galvanochemical method of wastewater treatment is that in the first stage, wastewater containing heavy metal ions and chromium / VI / is treated in the field of a galvanic cell formed by a mixture of iron and copper chips in a weight ratio of 3-4: 1 for 10-12 minutes after which the pH of the treated water is adjusted to 8.9-9.3, sedimentation is carried out for 15-30 minutes. in the presence of polyacrylamide and separation of the precipitate. At the second stage, the purified water without pH adjustment is subjected to processing in the field of a galvanic cell from a mixture of aluminum and copper chips in a ratio by weight of 2: 1 for 10-12 minutes. after which the pH of the treated water is adjusted to 6.5-7, it is left to stand in the presence of polyacrylamide for 30-35 minutes and the precipitate is separated.

 Such a two-stage galvanochemical treatment ensures the efficient purification of a mixed runoff containing ions of various heavy metals and chromium / VI /. This was confirmed by experiments on the purification of both model and real wastewater from heavy metal ions and chromium / VI /.

 Examples of the method.

Example 1. Processing by the specified method was subjected to a model solution of the following composition, mg / l: Cr / VI / 14.2; Cr / III / 34.3; Fe / III / 84.7; Cu / II / 2.5; Zn / II / 6.3; Cd / II / 9.6; NH $\genfrac{}{}{0ex}{}{\text{+}}{\text{4}}$ 11.1.

 The pH of the solution was adjusted to 4.8 by the addition of hydrochloric acid. Then, the prepared solution was subjected to galvanochemical treatment in the field of a galvanic cell of iron and copper chips, taken in the ratio / by weight / 4: 1 for 10 minutes. After treatment, the pH was adjusted to 9.0 with an alkali solution and sedimentation was carried out for 30 minutes. in the presence of polyacrylamide / 0.01% /. Decantate without additional pH adjustment was subjected to galvanochemical treatment in the field of a galvanic cell made of aluminum and copper chips in a ratio of / by weight / 2: 1 for 10 minutes. after which the pH of the treated water was adjusted to 6.5 and subjected to sedimentation for 30 minutes. in the presence of polyacrylamide.

 In a chemical analysis of treated water, ions of these metals were not detected.

Example 2. The treatment according to example 1 was subjected to wastewater of galvanic production with an initial pH of 2.2 and ion content, mg / l: Cr / VI / 10.6; Cr / III / 28.2; Zn / II / 4.5; Cu / II / 8.7; Ni / II / 1.5; Cd / II / 1.9; Fe _commonly 19.1; NH ⁺ ₄ 14.9.

 Wastewater was treated in the field of a galvanic cell from a mixture (in a weight ratio of 3: 1) of iron and copper chips without additional pH adjustment. After treatment, the pH was adjusted with alkali to 9.1 and the treated water was sedimented for 30 minutes. Then the decantate was subjected to galvanochemical treatment in the second stage; The pH of the treated water was 8.1. The pH was lowered with an acid solution to 7.0 and settled for 35 minutes.

 Chemical analysis showed the absence of these metal ions.

Example 3. The treatment according to example 1 was subjected to wastewater from the galvanic production of an electrical appliance plant of the following composition, mg / l: Cr _total. 46.2; Cr / VI / 34.0; Fe _commonly 89.5; Cu / II / 13.8; Ni / II / 2.0; Zn 30.0; Cd 5.4. The pH of the source water is 3.0. the pH of the sedimentation after the first stage of galvanochemical treatment of 9.3; The pH of the sedimentation after the second stage of 6.8. In purified wastewater, mg / l: Cr _total. 0.05; Fe 0.35; Cu 0.05. No ions of other metals were detected.

Example 4. The treatment according to example 1 was subjected to wastewater from the galvanic production of PO Elektroapparat the following composition, mg / l: Zn 0.1; Cu / II / 1.8; Ni / II / 0.42; Cr / VI / 6.4; Cr _total 10.5; Fe _commonly 16.0; Cd 0.3; petroleum products 8.8; suspended solids 316. The pH of the source water is 4.0. pH of sedimentation after the first stage of galvanic treatment is 8.9; The pH of the sediment after the second stage is 6.5. In the treated waste water ppm / l: Cu / II / 0.015; Cr _total 0.01; petroleum products 2.1; suspended solids - 11. No other metal ions were detected.

 Using the proposed method will allow for efficient wastewater treatment of engineering, galvanic and other industries from ions of heavy metals and chromium / VI /, to clean mixed effluents of galvanic production without prior separation, to reduce the time of galvanochemical treatment, to reduce energy costs, to simplify the hardware design of the cleaning process.

Claims (1)

 The method of purification of snow water from heavy metal ions, including its two-stage treatment in the field of a galvanic cell using a galvanic cell from a mixture of iron and copper chips at the first processing stage, settling in the presence of polyacrylamide and separating the precipitate, characterized in that as a galvanic cell to the second the processing steps use a mixture of aluminum and copper chips, and sedimentation and separation of the precipitate is carried out after each processing step, the treatment at the first stage is carried out at 2.0 5.0 before settling adjust pH to 8.9 - 9.3, and after separation of the precipitate water is directed into the second treatment step with subsequent adjustment of pH to 7.0 to 6.5 by settling.