CN107720891A - A kind of method for promoting the reduction of heavy metal chromium ion electrochemical - Google Patents

Abstract

The invention relates to a method for promoting the electrochemical reduction of heavy metal chromium ions, which uses waste pop cans to electrochemically treat hexavalent chromium sewage under the constant potential condition of -1.5V. The experimental results are as follows: the traditional chemical method can reach more than 90% of the hexavalent chromium component processing efficiency in more than 90 minutes; and the hexavalent chromium can reach 93% in 60 minutes under the condition of an external ‑1.5V constant potential; it is worthwhile It should be noted that under the condition of adding 0.001M oxalic acid, the electrochemical method can completely remove the hexavalent chromium component in the sewage within 60 minutes; The consumption is 10% of the condition without adding, which realizes the treatment effect of high efficiency and energy saving.

Description

A method for promoting the electrochemical reduction of heavy metal chromium ions

technical field

The invention relates to a method for promoting the electrochemical reduction of heavy metal chromium ions.

Background technique

In college students' experiments and scientific research activities, heavy metals such as hexavalent chromium are widely used to prepare coating solutions, corrosion inhibitors and catalysts. However, hexavalent chromium is a highly toxic and carcinogenic environmental pollutant, which seriously threatens human health. At present, colleges and universities lack simple and efficient methods for the treatment of hexavalent chromium sewage, so that they rely too much on external cooperation units. Once the processing time of the outsourcing unit is delayed, the storage of hexavalent chromium sewage will bring extremely high safety risks to colleges and universities.

Contents of the invention

The invention provides a method for promoting the electrochemical reduction of heavy metal chromium ions, and realizes efficient removal and safe discharge of laboratory hexavalent chromium sewage.

A method for promoting the electrochemical reduction of heavy metal chromium ions is to carry out electrochemical treatment in chromium-containing sewage under the constant potential condition of -1.5V. In the experiment, the electrochemical workstation and ultraviolet spectrophotometer were used to test and compare the electrochemical treatment ability of cans waste aluminum flakes and oxalic acid additives to chromate. The experimental results are as follows: the traditional chemical method takes 90-120 minutes to process hexavalent chromium to reach a treatment efficiency of more than 90%; while the treatment of hexavalent chromium with aluminum sheet can reach 93% in 60 minutes under the condition of an external -1.5V constant potential; it is worth Note that under the condition of adding 0.001M oxalic acid, the electrochemical method can completely remove the hexavalent chromium component in the sewage; in addition, the comparison of energy consumption of electrochemical treatment within 60 minutes found that the energy consumption under the condition of adding oxalic acid was zero. Adding 10% of the condition realizes the treatment effect of high efficiency and energy saving.

The comparative analysis shows that the electrochemical treatment method achieves high efficiency and energy saving treatment under the constant potential condition of -1.5V, especially when oxalic acid additive is present in the chromium-containing sewage, the electrochemical treatment efficiency is significantly improved.

The present invention has the following advantages:

(1) The preparation process is simple, the operation is convenient, the oxalic acid organic compound is cheap and easy to obtain, and the electrode potential of -1.5V is easy to control.

(2) The present invention efficiently treats hexavalent chromium pollutants through a constant potential electrochemical treatment method, and realizes high efficiency and energy saving in the electrochemical treatment process by adding a reducing oxalic acid reagent.

Description of drawings

Figure 1 is a schematic diagram of treating hexavalent chromium sewage by using a three-electrode system and a constant potential electrochemical method.

Detailed ways

A method for promoting the electrochemical reduction of heavy metal chromium ions, the specific operations are as follows:

a. Use an electronic balance and filter paper to weigh 0.0197g of potassium dichromate, put it into a beaker, use an aqueous solution, and finally pour it into a 1000mL volumetric flask, and titrate to the marked line. The concentration of the prepared Cr ⁶⁺ solution is 100 μM;

b. Using a three-electrode system (the working electrode is an aluminum sheet (the exposed area is ~2.25cm ² ); the reference electrode is a saturated calomel electrode (SCE, 0.24V vs. NHE) and a graphite rod counter electrode), the experiment uses electrochemical The workstation provides a constant potential of -1 ~ -3V to apply electricity on the surface of the working electrode. As shown in Figure 1;

c. Use the electrochemical workstation to record the change curve of current density with time within 0-60 minutes, and then calculate the power and energy consumption within a certain period of time;

d. Weigh 0.5g of diphenylcarbazide with an electronic balance and filter paper, measure 50mL of acetone with a 200mL graduated cylinder, dissolve diphenylcarbazide in acetone, and add 50mL of ultrapure water with a 200mL graduated cylinder to In acetone, finally add 4.0mL of strong acid mixed solution formed by mixing 1mLH ₃ PO ₄ , 1mL H ₂ SO ₄ , and 2mL H ₂ O to prepare the developer solution;

e. Before the experiment, prepare 5, 10, 20, 50, and 100 μM hexavalent chromium solutions in sequence, take out 1.0 mL of solution samples, add 2.0 mL of chromogenic agent, shake well and let stand for 15 minutes to develop color. After 15 minutes, add the test solution after standing still to the cuvette, and measure its absorbance at a wavelength of 540nm with a blank solution as a reference. Draw a standard curve with the concentration of hexavalent chromium as the abscissa and the corresponding absorbance as the ordinate. The standard curve of this experiment was determined as,

Note: A(Cr ⁶⁺ ) is the absorbance of Cr ⁶⁺ solution

f. Use spectrophotometer and colorimetry (volume ratio of sewage and color developer 1:2) to test the absorbance intensity in the solution after 10, 20, 30, and 60 minutes, and compare the above standard curve to obtain the corresponding concentration of hexavalent chromium ;

g. Comparative study of the energy consumption and treatment efficiency of the hexavalent chromium sewage added with 0.001M oxalic acid solution in the electrochemical treatment of aluminum sheets.

Claims (4)

1. This patent relates to a method for promoting the electrochemical reduction of heavy metal chromium ions. The specific operations are as follows: a. Use an electronic balance and filter paper to weigh 0.0197g of potassium dichromate, put it into a beaker, use an aqueous solution, and finally pour it into a 1000mL volumetric flask, and titrate to the marked line. The concentration of the prepared Cr ⁶⁺ solution is 100 μM; b. Using a three-electrode system (the working electrode is an aluminum sheet (the exposed area is ~2.25cm ² ); the reference electrode is a saturated calomel electrode (SCE, 0.24V vs. NHE) and a graphite rod counter electrode), the experiment uses electrochemical The workstation provides a constant potential of -1 ~ -3V to apply electricity on the surface of the working electrode. As shown in Figure 1; c. Use the electrochemical workstation to record the change curve of current density with time within 0-60 minutes, and then calculate the power and energy consumption within a certain period of time; d. Weigh 0.5g of diphenylcarbazide with an electronic balance and filter paper, measure 50mL of acetone with a 200mL graduated cylinder, dissolve diphenylcarbazide in acetone, and add 50mL of ultrapure water with a 200mL graduated cylinder to In acetone, finally add 4.0mL of strong acid mixed solution formed by mixing 1mLH ₃ PO ₄ , 1mL H ₂ SO ₄ , and 2mL H ₂ O to prepare the developer solution; e. Before the experiment, prepare 5, 10, 20, 50, and 100 μM hexavalent chromium solutions in sequence, take out 1.0 mL of solution samples, add 2.0 mL of chromogenic agent, shake well and let stand for 15 minutes to develop color. After 15 minutes, add the test solution after standing still to the cuvette, and measure its absorbance at a wavelength of 540nm with a blank solution as a reference. Draw a standard curve with the concentration of hexavalent chromium as the abscissa and the corresponding absorbance as the ordinate. The standard curve of this experiment was determined as, <mrow><msub><mi>C</mi><mrow><mo>(</mo><mi>c</mi><mi>o</mi><mi>n</mi><mi>c</mi><mi>e</mi><mi>n</mi><mi>t</mi><mi>r</mi><mi>a</mi><mi>t</mi><mi>i</mi><mi>o</mi><mi>n</mi><mo>)</mo></mrow></msub><mo>=</mo><mn>55.6</mn><mo>&amp;times;</mo><msub><mi>A</mi><mrow><mo>(</mo><msup><mi>Cr</mi><mrow><mn>6</mn><mo>+</mo></mrow></msup><mo>)</mo></mrow></msub><mo>-</mo><mn>0.223</mn><mo>-</mo><mo>-</mo><mo>-</mo><mrow><mo>(</mo><mn>1</mn><mo>)</mo></mrow></mrow> Note: A(Cr ⁶⁺ ) is the absorbance of Cr ⁶⁺ solution f. Use spectrophotometer and colorimetry (volume ratio of sewage and color developer 1:2) to test the absorbance intensity in the solution after 10, 20, 30, and 60 minutes, and compare the above standard curve to obtain the corresponding concentration of hexavalent chromium ; g. Comparative study of the energy consumption and treatment efficiency of the hexavalent chromium sewage added with 0.001M oxalic acid solution in the electrochemical treatment of aluminum sheets. 2. A method for promoting the electrochemical reduction of heavy metal chromium ions as claimed in claim 1, characterized in that the preparation process is simple, easy to operate, oxalic acid organic matter is cheap and easy to get, and the electrode potential of -1.5V is easy to control. 3. A method for promoting the electrochemical reduction of heavy metal chromium ions as claimed in claim 1, characterized in that the waste and old pop can aluminum flakes are used to realize hexavalent chromium sewage treatment to achieve good economic and social benefits. 4. A method for promoting the electrochemical reduction of heavy metal chromium ions as claimed in claim 1, characterized in that the hexavalent chromium sewage is efficiently and energy-savingly treated, which facilitates the on-site treatment of laboratory hexavalent chromium pollutants.