RU2519383C1 - Method of purifying water and water solutions from anions and cations - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: purification of water and water solutions from anions and cations is carried out by electrolysis by alternating asymmetric current with application of insoluble electrodes, electrolysis process is performed with air barbotage with bubble diameter larger than interelectrode distance with further introduction into solution of complexing agent -bivalent iron salt (FeSO₄) with ratio 5:1 with respect to initial concentration of purified ion and further precipitation of solution for 8 days.

EFFECT: increased degree of purification and reduction of specific energy consumption.

1 tbl, 6 ex

Description

The invention relates to the purification of water and aqueous solutions from anions and cations and can be used to purify natural waters, effluents of metallurgical, engineering and other industries.

Known methods of purification of water and aqueous solutions, which are electrocoagulation treatment, providing a degree of purification of 90-95% [Smirnov GN, Genkin V.E. Wastewater treatment in metal processing. M.: Metallurgy, 1989. 224 p.]. Their disadvantages are the use of direct electric current, which requires additional devices for converting alternating electric current, and the need for aeration of wastewater after electrocoagulation treatment before clarification.

Known methods for coagulation treatment of water and aqueous solutions, carried out by adding a complexing agent to the solution, followed by sedimentation [Smirnov GN, Genkin V.E. Wastewater treatment in metal processing. M .: Metallurgy, 1989.222 s .; Technical notes on water issues / K. Barak [et al.]; under the editorship of T.A. Karyukhina, I.N. Churbanova. M.: Stroyizdat, 1983. 607 p.]. The disadvantage of these methods is the high consumption of reagents and a low degree of purification.

A known method of purifying water and aqueous solutions from metal ions by electrolysis using insoluble electrodes when applying an alternating sinusoidal voltage [Method of electrochemical purification of water and aqueous solutions from heavy metal ions. Auth. St. USSR No. 1724591, cl. C02F 1/46, 1991]. This method is taken as a prototype. The main disadvantage of this method is the low degree of purification and significant energy consumption (1.5-2 (kW · h) / m ³ ).

The objective of the invention is to increase the degree of purification and reduce specific energy consumption.

This is achieved by purifying water and aqueous solutions with an alternating asymmetric current by electrolysis using pairs of insoluble heterogeneous electrodes and sparging the solution with air, after which a complexing agent is introduced into the solution and sedimentation is carried out.

As a complexing agent, an iron salt of divalent FeSO _{4 is used} [Glykina F.B. Chemistry of complex compounds: textbook. manual for universities. M .: Education, 1982. 160 p.]. The ratio of the initial concentrations of the complexing agent and the purified ion is 5: 1.

Sparging of the solution to be cleaned is carried out under the condition that the diameter of the air bubbles should be greater than the distance between the electrodes.

The settling time of the aqueous solution is 8 days.

Experimental data showed that a further increase in the ratio of initial concentrations and settling time does not significantly increase the degree of purification, and when the ratio of initial concentrations is less than 5: 1 and the settling time is less than 8 days, the degree of purification is much lower. When bubbling the solution with air, if the diameter of the bubbles is less than the distance between the electrodes, the degree of purification decreases.

To implement the proposed method, the cleaning process is carried out in an electrolyzer of alternating electrodes made in the form of plates. Electrode material: stainless steel 12X18H10T, titanium alloy OT 4-0. Water temperature 20-25 ° C. The distance between the electrodes is 12 mm. The volume of the poured aqueous solution is 1 liter. The duration of the electrolysis is 10 minutes with a current strength of 0.5 A and a voltage at the terminals of the electrodes of 4.1 V.

Aqueous solutions containing cadmium (II), copper (II), nickel (II) and chromium (VI) ions were treated. The initial concentration of each ion in a solution of 0.5 mg / L.

Example 1. The electrolysis was subjected to an aqueous solution at the parameters indicated above, with air sparging. The solution was bubbled under the condition that the diameter of the bubbles was greater than the distance between the electrodes (> 12 mm). After electrolysis, the FeSO ₄ complexing agent was introduced. The ratio of the initial concentrations of the complexing ion and the purified ion was 5: 1. The initial concentration of the complexing ion in the solution was 10 mg / L. The settling time is 8 days.

The degree of purification was determined by the formula,%:

$$Y=\left(\frac{C_o-C_{\mathrm{to}}}{{\mathrm{FROM}}_{\mathrm{about}}}\right)\mathrm{one\; hundred}$$

where C _o , C _to - the initial and final concentration of the purified metal ion, mg / L.

The specific energy consumption W was determined by the formula, (kW · h) / m ³ :

$$W=\frac{IU\tau }{V}{10}^{-3}$$

where I is the current strength, A;

U is the voltage at the terminals of the electrodes, V;

τ is the duration of electrolysis, h;

V is the volume of the poured aqueous solution, m ³ ;

10 ^-3 is the conversion factor from W to kW.

The degree of purification of the aqueous solution is equal: for nickel, Y _Ni = 34.44%, for cadmium Y _Cd = 63.44%, for copper Y _Cu = 99.56%, for chromium Y _Cr = 99.98% and for iron Y _Fe = 99.28%. The specific energy consumption is W = 0.47 (kW · h) / m ³ .

Example 2. The electrolysis was subjected to an aqueous solution at the parameters indicated above, with air sparging. The solution was bubbled under the condition that the diameter of the bubbles was greater than the distance between the electrodes (> 12 mm). After electrolysis, the FeSO ₄ complexing agent was introduced. The ratio of the initial concentrations of the complexing ion and the purified ion was 6: 1. The initial concentration of the complexing ion in the solution was 12 mg / L. The settling time is 8 days.

The degree of purification of the aqueous solution is equal: for nickel, Y _Ni = 34.62%, for cadmium Y _Cd = 63.74%, for copper Y _Cu = 99.63%, for chromium Y _Cr = 99.99% and for iron Y _Fe = 99.88%. The specific energy consumption is W = 0.47 (kW · h) / m ³ .

Example 3. The electrolysis was subjected to an aqueous solution at the parameters indicated above, with air sparging. The solution was bubbled under the condition that the diameter of the bubbles was greater than the distance between the electrodes (> 12 mm). After electrolysis, the FeSO ₄ complexing agent was introduced. The ratio of the initial concentrations of the complexing ion and the purified ion was 2.5: 1. The initial concentration of the complexing ion in the solution was 5 mg / L. The settling time is 8 days.

The degree of purification of the aqueous solution is equal: for nickel, Y _Ni = 24.23%, for cadmium Y _Cd = 46.75%, for copper Y _Cu = 81.23%, for chromium Y _Cr = 74.32% and for iron Y _Fe = 92.21%. The specific energy consumption is W = 0.47 (kW · h) / m ³ .

Example 4. The electrolysis was subjected to an aqueous solution at the parameters indicated above, with air sparging. The solution was bubbled under the condition that the diameter of the bubbles was greater than the distance between the electrodes (> 12 mm). After electrolysis, the FeSO ₄ complexing agent was introduced. The ratio of the initial concentrations of the complexing ion and the purified ion was 5: 1. The initial concentration of the complexing ion in the solution was 10 mg / L. The settling time is 10 days.

The degree of purification of the aqueous solution is equal to: for nickel Y _Ni = 35.24%, for cadmium Y _Cd = 64.22%, for copper Y _Cu = 99.16%, for chromium Y _Cr = 99.98% and for iron Y _Fe = 99.58%. The specific energy consumption is W = 0.47 (kW · h) / m ³ .

Example 5. The electrolysis was subjected to an aqueous solution at the parameters indicated above, with air sparging. The solution was bubbled under the condition that the diameter of the bubbles was greater than the distance between the electrodes (> 12 mm). After electrolysis, the FeSO4 complexing agent was introduced. The ratio of the initial concentrations of the complexing ion and the purified ion was 5: 1. The initial concentration of the complexing ion in the solution was 10 mg / L. The settling time is 4 days.

The degree of purification of the aqueous solution is equal: for nickel, Y _Ni = 29.17%, for cadmium Y _Cd = 51.24%, for copper YC _u = 91.76%, for chromium Y _Cr = 86.88% and for iron Y _Fe = 99.18%. The specific energy consumption is W = 0.47 (kW · h) / m ³ .

Example 6. The electrolysis was subjected to an aqueous solution at the parameters indicated above, with air sparging. The solution was bubbled under the condition that the diameter of the bubbles was 3 mm. After electrolysis, the FeSO ₄ complexing agent was introduced. The ratio of the initial concentrations of the complexing ion and the purified ion was 5: 1. The initial concentration of the complexing ion in the solution was 10 mg / L. The settling time is 8 days.

The degree of purification of the aqueous solution is equal to: for nickel, Y _Ni = 26.93%, for cadmium Y _Cd = 52.44%, for copper Y _Cu = 84.79%, for chromium Y _Cr = 77.83% and for iron Y _Fe = 99.3%. The specific energy consumption is W = 0.47 (kW · h) / m ³ .

Quantification of the ions contained in the aqueous solution after purification was carried out on an Agilent 7500 ICP-MS mass spectrometer.

The results of experiments on cleaning the solution from chromium (VI) in comparison with the prototype are shown in the table.

The results of experiments on cleaning from Cr ⁶⁺ in comparison with the prototype Way C _o , mg / l C _to , mg / l MPC, mg / l Y% W, (kWh) / m ³ According to the prototype 0.5 0.02 0.001 96 1,5-2 The proposed method 0.5 0.0001 99.98 0.47

Experimental data showed that the maximum degree of purification is achieved by electrolysis of water and aqueous solutions by sparging with air with a bubble diameter greater than the interelectrode distance, introducing a complexing agent - ferrous iron salt (FeSO ₄ ), in the ratio 5: 1 and settling the solution for 8 days. The degree of purification of the aqueous solution is equal to: for nickel Y _Ni = 34.44%, for cadmium Y _Cd = 63.44%, for copper Y _Cu = 99.56%, for chromium Y _Cr = 99.98% and for iron Y _Fe = 99.28%. The specific energy consumption is W = 0.47 (kW · h) / m ³ .

Claims (1)

The method of purification of water and aqueous solutions from anions and cations by electrolysis by alternating asymmetric current using insoluble electrodes, characterized in that the electrolysis process is carried out with bubbling air with an air bubble diameter greater than the interelectrode distance, followed by the introduction of a complexing agent - a divalent iron salt (FeSO ₄ ) - in a ratio of 5: 1 with respect to the initial concentration of the ion being purified and further settling of the solution for 8 days.