RU2453502C2 - Method of cleaning waste water from heavy and nonferrous metal ions and apparatus for realising said method - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: waste water containing nonferrous and heavy metal ions, particularly cadmium Cd²⁺, nickel Ni²⁺, zinc Zn²⁺, copper Cu²⁺, chromium Cr³⁺ and iron Fe²⁺, Fe³⁺, undergoes electrochemical neutralisation, after which N,N-dimethyl-N-prop-2-enylprop-2-ene-1-ammonium chloride is added into the purified water, with weight ratio of the extracted metal to the added substance of 1 :(0.002-0.003), after which electrofloatation treatment is carried out. The apparatus has a housing divided into sections for preliminary electro-treatment in form of the cathode chamber of a diaphragm cell and electrofloatation treatment. The apparatus is fitted with a pipe which connects the section for electrofloatation treatment with the anode chamber of the diaphragm cell, wherein the anode chamber is fitted with pipes for inlet of alkaline treated water and outlet of neutralised water. The apparatus is fitted with a mixing chamber, lying after the cathode chamber of the diaphragm cell, formed by three vertical overflow partitions, wherein the last two partitions on the path of the purified water are made from electroconductive material and are used as electrodes. The mixing chamber is fitted with a pipe in its bottom part for inlet of N,N-dimethyl-N-prop-2-enylprop-2-ene-1-ammonium chloride.

EFFECT: high degree of purity of water from nonferrous and heavy metal ions.

2 cl, 1 dwg, 2 tbl, 1 ex

Description

The invention relates to methods and devices for wastewater treatment from heavy and non-ferrous metal ions, in particular cadmium Cd ²⁺ , nickel Ni ²⁺ , zinc Zn ²⁺ , copper Cu ²⁺ , chromium Cr ³⁺ , iron Fe ²⁺ , Fe ³⁺ , and can be used in enterprises of mechanical engineering, instrument manufacturing, ferrous and non-ferrous metallurgy, radio electronics, the electrical industry, having galvanic production for the creation of water purification and reverse water supply systems.

A known method of treating wastewater containing emulsified and suspended impurities, including electroflotation in a device with perforated electrodes and preliminary electric treatment using insoluble anodes (SU, Copyright certificate No. 966025, C02F 1/46, 1982). The specified method does not provide a high degree of purification from non-ferrous and heavy metal ions.

The closest in technical essence and the achieved result is a method for treating wastewater from non-ferrous and heavy metal ions and a device for its implementation, including electrochemical neutralization at a volume current density in the cathode chamber of 0.4-10 A / L and subsequent electroflotation treatment at a bulk density current component of 0.2-0.6 of the current density in the cathode chamber. A device for treating wastewater from metal ions comprises a housing divided into sections for preliminary electric water treatment and electroflotation treatment with a set of insoluble horizontal electrodes placed in it, nozzles for supplying waste water and removal of purified water and a device for removing sludge, the preliminary electric treatment section is made in the form a diaphragm electrolyzer using an anion exchange membrane, wherein the wastewater inlet pipe is located at the bottom of the cathode chamber, and the latter is located at the same level with the electroflotation cleaning section and is separated from it by an overflow partition with a height of 0.3-0.8 from the height of the electroflotation cleaning section, and the anode chamber is equipped with nozzles for input and output of electrolyte, and the ratio of the volumes of the anode, cathode chambers and section electroflotation purification is 1: 2-4: 7-15, respectively (SU, Copyright certificate No. 1675215, C02F 1/46, 1991).

The specified method and device does not provide a high degree of purification from ions of non-ferrous and heavy metals. This method and device selected for the prototype.

The objective of the invention is to develop a method and device for treating wastewater from non-ferrous and heavy metal ions, which allows to increase the degree of purification.

The problem is solved in that in the proposed method, after electrochemical neutralization of water, a reagent is additionally introduced into the purified water: organic substance N, N-Dimethyl-N-prop-2-enylprop-2-en-1-aminium chloride in the mass ratio of the recoverable metal to the introduced substance 1: (0.002-0.003).

The action of N, N-Dimethyl-N-prop-2-enylprop-2-en-1-aminium chloride reduces to the adsorption recharging of the surface of hydrogen gas bubbles and to the appearance of electrostatic attractive forces between oppositely charged metal hydroxide particles and bubbles, as well as to a decrease in size bubbles and their ascent rate, which leads to an increase in the efficiency of collisions between particles and bubbles and the formation of particle-bubble flotation complexes, i.e. the flotation component is intensified, which increases the degree of water purification from metals.

The method is carried out using the device shown in the figure.

The device consists of a housing 1, separated by an overflow partition 2 into sections of preliminary electric processing and electroflotation cleaning with a set of insoluble horizontal electrodes placed in it 3. The housing of the device is equipped with nozzles 4, 5, 12, respectively, for introducing wastewater and discharging purified water, introducing a reagent solution N , N-Dimethyl-N-prop-2-enylprop-2-en-1-aminium chloride and a device 6 for collecting and discharging flotation sludge. The pre-treatment section is a cathode chamber of a diaphragm electrolyzer and provides separation of the products of electrode reactions using an anion-exchange membrane 7, which separates the cathode chamber from the anode.

The anode chamber is equipped with a vertical insoluble electrode (anode) 8 and nozzles 10 and 11, respectively, for the introduction of alkaline purified water and the output of neutralized water.

The cathode chamber is equipped with a vertical insoluble electrode (cathode) 9 and a wastewater inlet pipe 4, which is located at the bottom of the cathode chamber, the latter being located at the same level as the electroflotation treatment section.

After the cathode chamber of the diaphragm electrolyzer there is a mixing chamber formed by three vertical overflow partitions 2, 13 and 14 and equipped with a nozzle 12 located in its lower part and intended for introducing a solution of reagent N, N-Dimethyl-N-prop-2-enylprop- 2-en-1-aminium chloride. The partition 13 has a gap between the bottom of the apparatus and its lower edge for the flow of wastewater. The last two partitions 13 and 14 in the direction of the purified water are made of electrically conductive material and used as electrodes to provide additional generation of gas bubbles. The partition 13 is used as an oxide-ruthenium-titanium anode, and the partition 14 is used as a stainless steel cathode, respectively.

The device is equipped with a pipe 15 connecting the electroflotation cleaning section with the anode chamber of the diaphragm electrolyzer.

сопровождающая выделением пузырьков водорода и образованием гидроксил-ионов, что обеспечивает подщелачивание воды до величины pH 8-10, при которой происходит образование частиц гидроксида металла. Одновременно происходит флотация частиц пузырьками водорода.The device operates as follows. Wastewater with a pH of 5-7 containing ions of one of the metals: Cd ²⁺ , Cu ²⁺ , Ni ²⁺ , Cr ³⁺ , Zn ²⁺ , Fe ²⁺ , Fe ³⁺ , at a concentration of 10-500 mg / l fed through pipe 4 to the cathode chamber of the diaphragm electrolyzer. As a result of electrolysis at the cathode 9, a discharge reaction of water molecules occurs

accompanying the release of hydrogen bubbles and the formation of hydroxyl ions, which provides alkalization of water to a pH of 8-10, at which the formation of metal hydroxide particles occurs. At the same time, flotation of particles by hydrogen bubbles occurs.

Next, the waste water is poured through the partition 2 and enters the mixing chamber. When moving upward between the partitions 13 and 14, the wastewater is mixed with the reagent solution N, N-Dimethyl-N-prop-2-enylprop-2-en-1-aminium chloride entering through the pipe 12.

From the mixing chamber, the waste water is poured through the partition 14 into the electroflotation treatment section, where particles of metal hydroxides are removed to the surface of the water due to the operation of the electrode unit 3, generating gas bubbles of hydrogen and oxygen.

In the section of electroflotation cleaning, a downward movement of water is provided with its removal from under the electrode block 3. At the same time, an additional cleaning effect is observed associated with filtering water through a dense filter of electrolytic bubbles.

Partitions 13 and 14, used as electrodes, provide additional generation of gas bubbles of oxygen and hydrogen, respectively.

что сопровождается нейтрализацией pH до величины 6,5-7,0. Нейтрализованная и очищенная вода выводится из установки через патрубок 11.Purified water from particles of metal hydroxides with a pH of 8-10 flows from the electroflotation cleaning section through pipe 5 and through pipe 15 connecting the electroflotation cleaning section to the anode chamber of the diaphragm electrolyzer, enters it through pipe 10. In the anode chamber on anode 8 as a result of discharge hydroxyl ions the formation of a water molecule and the evolution of oxygen

which is accompanied by neutralization of the pH to a value of 6.5-7.0. Neutralized and purified water is discharged from the installation through the pipe 11.

Floating in the process of electroflotation to the water surface of the cathode chamber and the electroflotation cleaning section, including the mixing chamber, the dispersed phase of contaminants in the form of metal hydroxides is formed into a foam layer (flotation sludge), which is removed by means of device 6.

The invention is illustrated by the following example.

Example. The consumption of purified water is 10 l / h. The volumetric current density in the cathode chamber of the electrolyzer is 0.45 A / L, in the electroflotation cleaning section 0.2 A / L, which is 0.44 of the current density in the cathode chamber. The ratio of nickel ion to the introduced reagent N, N-Dimethyl-N-prop-2-enylprop-2-en-1-aminium chloride is 1: 0.002.

сопровождающая выделением пузырьков водорода и образованием гидроксил-ионов, что обеспечивает нейтрализацию (подщелачивание) воды до величины pH 10, при которой происходит образование частиц гидроксида никеля (2OH^- + Ni²⁺ = Ni(OH)₂). Одновременно происходит флотация частиц пузырьками водорода.Wastewater containing Ni ^{2+ ions} at a concentration of 50 mg / L at pH 5 is supplied through pipe 4 to the cathode chamber of the diaphragm electrolyzer. As a result of electrolysis at the cathode 9, a discharge reaction of water molecules occurs

accompanying the release of hydrogen bubbles and the formation of hydroxyl ions, which ensures the neutralization (alkalization) of water to a pH of 10 at which the formation of particles of nickel hydroxide (2OH ^- + Ni ²⁺ = Ni (OH) ₂ ). At the same time, flotation of particles by hydrogen bubbles occurs.

Next, the waste water is poured through the partition 2 and enters the mixing chamber, where it is mixed with a solution of the reagent N, N-Dimethyl-N-prop-2-enylprop-2-en-1-aminium chloride entering through the pipe 12.

From the mixing chamber, the waste water is poured through the partition 14 into the electroflotation treatment section, where particles of nickel hydroxide are removed to the surface of the water due to the operation of the electrode unit 3 generating gas bubbles of hydrogen and oxygen.

что сопровождается нейтрализацией (подкислением) воды pH до величины 7,0. Нейтрализованная и очищенная вода выводится из установки через патрубок 11.Purified water from particles of nickel hydroxide with a pH of 10 flows from the electroflotation purification section through pipe 5 and through a pipe 15 connecting the electroflotation purification section to the anode chamber of the diaphragm electrolyzer, enters it through pipe 10. In the anode chamber on anode 8, the hydroxyl ion formation of a water molecule and oxygen evolution

which is accompanied by neutralization (acidification) of water pH to a value of 7.0. Neutralized and purified water is discharged from the installation through the pipe 11.

The slurry in the form of nickel hydroxide is removed from the water surface of the cathode chamber and the electroflotation cleaning section, including the mixing chamber with the device 6.

Purified water is analyzed for nickel by atomic absorption spectroscopy. The degree of purification from nickel is 99.99%, which corresponds to a residual concentration of 0.005 mg / L.

Similar experiments are carried out at a ratio of nickel ion to the introduced reagent 1: 0.001, 1: 0.003, 1: 0.004. Similar experiments as in example 1 are carried out in the presence of ions, Cd ²⁺ , Cu ²⁺ , Cr ³⁺ , Fe ²⁺ , Fe ³⁺ . The experimental conditions and the results are summarized in table 1.

TABLE 1 Allocated metal hydroxide, concentration of 50 mg / l The degree of purification from metals,% at various ratios of metal to N, N-Dimethyl-N-prop-2-enylprop-2-en-1-aminium chloride 1: 0.001 1: 0.002 1: 0.003 1: 0.004 Cd ²⁺ 99.60 99,99 99,99 99.63 Ni ²⁺ 99.69 99,99 99,99 99.56 Cu ²⁺ 99.59 99,99 99,99 99.48 Zn ²⁺ 99.71 99,99 99,99 99.58 Cr ³⁺ 99.68 99,99 99,99 99.72 Fe ²⁺ 99.82 99,99 99,99 99.86 Fe ³⁺ 99.76 99,99 99,99 99,99

The maximum degree of purification from metals of 99.99% is achieved with a mass ratio of recoverable metal to the introduced substance N, N-Dimethyl-N-prop-2-enylprop-2-en-1-aminium chloride 1: (0.002-0.003). In the zone of low and high ratios, the signs of particle and bubble charges coincide, and electroflotation is less effective. In the zone of intermediate ratios, the particle charge is negative, and the hydrogen bubbles are positive, which leads to an increase in the degree of purification.

Comparative results of the effectiveness of the known and proposed methods are presented in table.2.

TABLE 2 Cleaning method The degree of purification from metals,% Cd ²⁺ Zn ²⁺ Ni ²⁺ Cu ²⁺ Cr ³⁺ Fe ³⁺ Fe ²⁺ Famous 99.90 99.90 99.55 99.88 99.80 99.80 99.80 Proposed 99,99 99,99 99,99 99,99 99,99 99,99 99,99

As can be seen from table 2, the proposed method and device ensure the achievement of a high degree of purification of 99.99%, which is 0.09-0.44% more than in the known.

Claims (2)

1. A method of treating wastewater from ions of heavy and non-ferrous metals, including electrochemical neutralization and electroflotation treatment, characterized in that after electrochemical neutralization, N, N-dimethyl-N-prop-2-enylprop-2-en-1 is introduced into the purified water -aminochloride with a mass ratio of recoverable metal and introduced substance 1: (0.002-0.003). 2. A device for treating wastewater from ions of heavy and non-ferrous metals, comprising a housing divided into sections of preliminary electric treatment in the form of a cathode chamber of a diaphragm electrolyzer and electroflotation treatment, characterized in that the device is equipped with a pipeline connecting the electroflotation treatment section to the anode chamber of the diaphragm electrolyzer, wherein the anode chamber is equipped with nozzles for entering alkaline purified water and withdrawing neutralized water and a mixing chamber located after cat one chamber of the diaphragm electrolyzer, formed by three vertical overflow partitions, while the last two partitions in the direction of the purified water are made of electrically conductive material and used as electrodes, and equipped with a nozzle located in its lower part, designed to enter the reagent solution N, N- limethyl-N-prop-2-enylprop-2-en-1-aminium chloride.

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