Preparation of a nickel-iron-calcium composite catalyst for treating wastewater containing metal complexes

Abstract

The invention discloses a formula of a nickel-iron-calcium composite catalyst for treating wastewater containing metal complexes, comprising the following steps: mixing nickel salt, iron salt, calcium salt and distilled water according to a certain weight ratio to obtain solution A, mixing sodium hydroxide and distilled water to obtain solution B, adding solution B dropwise into solution A under magnetic stirring conditions, continuously stirring to obtain solution C, transferring solution C to a stainless steel autoclave lined with polytetrafluoroethylene, hydrothermally reacting to obtain precipitate D, washing precipitate D with distilled water and anhydrous alcohol solution for multiple times to obtain precipitate E, placing precipitate E in a vacuum drying oven for constant temperature drying to obtain dry solid F, and grinding solid F into powder for standby use. The nickel-iron-calcium composite catalyst of the invention greatly improves the catalytic oxidation efficiency and the metal complex removal rate.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment, in particular to the preparation of a nickel-iron-calcium composite catalyst for treating wastewater containing metal complexes. Background Art

[0002] In recent years, with the increase of human activities, the environmental pollution problems caused are also increasing. In particular, the pollution of heavy metals in water bodies has greatly threatened the global ecosystem and human health. With the diversification of drug use in industrial industries, especially in the electroplating industry, when there are strong ligands in the water body, heavy metals in the water body are very easy to combine with it to form metal complexes with extremely high stability, resulting in the inability of traditional treatment technologies to have an effect on them. At present, advanced oxidation methods have a good removal effect on metal complexes, among which hypochlorous acid oxidation method is often used to treat electroplating wastewater, but the existing catalysts are still difficult to reach the trace standard for the removal of metal complexes in wastewater. Therefore, it is necessary to create a new catalyst formula that can apply hypochlorous acid oxidation technology to the efficient removal of metal complexes. Summary of the invention

[0003] The purpose of the present invention is to provide a preparation of a nickel-iron-calcium composite catalyst for degrading metal complexes, so as to solve the problem that the catalytic oxidation effect is poor when the above-mentioned hypochlorous acid oxidation technology is applied to the removal of metal complexes.

[0004] To achieve the above object, the present invention provides a preparation method of a nickel-iron-calcium composite catalyst for degrading metal complexes in electroplating wastewater, comprising the following steps:

[0005] (1) adding nickel salt, iron salt and calcium salt in a certain weight ratio to distilled water and stirring to obtain solution A, and mixing sodium hydroxide with distilled water to obtain solution B. Adding solution B dropwise to solution A under magnetic stirring, and continuing stirring to obtain solution C;

[0006] (2) transferring the solution C obtained in step (1) into a stainless steel autoclave lined with polytetrafluoroethylene, and subjecting the solution C to a hydrothermal reaction to obtain a precipitate D;

[0007] (3) washing the precipitate D obtained in step (2) with distilled water and anhydrous alcohol solution multiple times to obtain a precipitate E;

[0008] (4) placing the precipitate E obtained in step (3) into a vacuum drying oven for constant temperature drying to obtain a dry solid F;

[0009] (5) Grinding the solid F obtained in step (4) into powder to obtain a nickel-iron-calcium composite catalyst.

[0010] Preferably, in step (1), the mass ratio of calcium salt to distilled water is 1:50-200, the mass ratio of iron salt to distilled water is 1:25-100, and the mass ratio of nickel salt to distilled water is 1:10-50.

[0011] Preferably, the calcium salt is one or more of calcium nitrate, calcium hypochlorite and calcium carbonate.

[0012] Preferably, the iron salt is one or more of ferric chloride, ferric sulfate and ferric nitrate.

[0013] Preferably, the nickel salt is one or more of nickel sulfate and nickel chloride.

[0014] Preferably, the mass ratio of calcium salt to iron salt is 1-15; the mass ratio of calcium salt to nickel salt is 1-25; the mass ratio of nickel salt to iron salt is 1-20.

[0015] Preferably, the stirring steps in step (1) are all magnetic stirring, and the stirring time is continuous for 1 to 3 hours.

[0016] Preferably, the hydrothermal reaction temperature in step (2) is 90 to 150° C., and the hydrothermal reaction time is 2 to 12 hours.

[0017] Preferably, in the washing step in step (3), a high-speed centrifuge is used to wash the precipitate at a rotation speed of 10,000 r / min.

[0018] Preferably, the temperature of the vacuum drying step in step (4) is 30 to 90° C., and the drying time is 6 to 18 hours.

[0019] Therefore, the present invention adopts the above-mentioned structure to prepare a nickel-iron-calcium composite catalyst for degrading metal complexes in electroplating wastewater, which has the following beneficial effects:

[0020] (1) The iron material is doped with calcium and nickel to form a nickel-iron-calcium composite catalyst, and then the hypochlorous acid oxidation technology is applied to the removal of metal complexes in electroplating wastewater. The degradation effect of the material and the decomposition of hypochlorous acid can be affected by the doping amount of iron, calcium and nickel.

[0021] (2) The nickel-iron-calcium composite catalyst has low cost, simple preparation method, low equipment requirements, good operability, stable material structure in the hypochlorous acid oxidation system, and no ion leaching of iron, nickel, calcium ions, etc.

[0022] (3) The nickel-iron-calcium composite catalyst is magnetic, which is conducive to the subsequent recovery and reuse of materials.

[0023] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a preparation flow chart of the nickel-calcium-iron composite catalyst of the present invention;

[0025] Figure 2 This is a SEM image of the nickel-calcium-iron composite catalyst of the present invention at 2 μm before reaction;

[0026] Figure 3 This is an infrared spectrum of the nickel-calcium-iron composite catalyst before and after the reaction of the present invention;

[0027] Figure 4 The adsorption removal rate and catalytic oxidation removal rate of pollutants by the nickel-calcium-iron composite catalyst of the present invention at different pH values;

[0028] Figure 5 The degradation effect of the nickel-calcium-iron composite catalyst of the present invention on pollutants at different nickel, iron and calcium salt mass ratios;

[0029] Figure 6 This is a diagram showing the free radical shielding results of the nickel-calcium-iron composite catalyst of the present invention;

[0030] Figure 7 It is the free radical EPR test spectrum of the nickel-calcium-iron composite catalyst of the present invention. DETAILED DESCRIPTION

[0031] The present invention will be further described below. It should be noted that this embodiment is based on the technical solution and provides a detailed implementation method and a specific operation process, but the present invention is not limited to this embodiment.

[0032] Example 1

[0033] (1) adding nickel sulfate, ferric nitrate and calcium hypochlorite to distilled water and stirring to obtain solution A, then mixing sodium hydroxide with distilled water to obtain solution B, wherein the mass fraction of calcium in solution A is 0.5wt%, the mass fraction of nickel is 2.1wt%, the mass fraction of iron is 0.25wt%, and the mass ratio of nickel salt, iron salt and calcium salt is 2:1:1, and solution A is added dropwise to solution B during stirring, and stirring is continued for 3 hours to obtain solution C, wherein solution C is a uniform suspension;

[0034] (2) transferring the solution C obtained in step (1) into a stainless steel autoclave lined with polytetrafluoroethylene, sealing it, and subjecting it to a hydrothermal reaction at 120° C. for 12 hours to obtain a precipitate D;

[0035] (3) washing the precipitate D obtained in step (2) with distilled water and anhydrous ethanol for multiple times, and collecting the precipitate E by centrifugation at 10000 r / min;

[0036] (4) placing the precipitate E obtained in step (3) into a vacuum drying oven at 60° C. for constant temperature drying for 12 hours to obtain a dry solid F;

[0037] (5) Grinding the solid F obtained in step (4) into powder to obtain a calcium-iron composite catalyst.

[0038] Example 2

[0039] The difference between Example 2 and Example 1 is that the mass ratio of calcium salt, iron salt and nickel salt is 1:0:4 to 1:4:4.

[0040] Example 3

[0041] The difference between Example 3 and Example 1 is that the mass ratio of calcium salt, iron salt and nickel salt is 0:1:2 to 1:1:2.

[0042] Example 4

[0043] The difference between Example 4 and Example 1 is that the mass ratio of calcium salt, iron salt and nickel salt is 1:1:0 to 1:1:5.

[0044] The calcium iron composite catalyst prepared in Example 1 was subjected to various tests. Figure 2 It can be seen that the nickel-iron-calcium composite material before the reaction presents an irregular block structure and particle agglomeration occurs, wherein the dispersed particle size is about 0.5 to 1.0 μm. Figure 3 It can be seen that the 430cm -1 、873cm -1 ,1111cm -1 The characteristic peak at is generated by the vibration of Fe-OH and Fe-O in FeOOH; before the reaction, it is about 618cm -1 The deep peak at 583 cm is generated by the vibration of Ni-OH. -1 The stretching vibration peak is generated by the stretching vibration of Ni-OH; before and after the reaction, it is around 3450cm -1 The broad peak at about 1630 cm -1 The tiny peaks appearing at the bottom are all caused by the bending vibration of H2O molecules. Overall, the number of peak points decreases after the reaction, indicating that the functional groups on the surface of the material are replaced during the reaction, thereby improving the surface stability of the material.

[0045] The calcium iron composite catalyst prepared in Example 1 was applied to remove metal complexes in electroplating wastewater. Figure 4 The figure shows the adsorption effect and catalytic oxidation removal effect of calcium iron catalyst on complex nickel at different pH values. It can be seen from the figure that the adsorption removal effect of the catalyst for complex copper is very good when the pH value is between 7-12, and the oxidation removal effect of the catalyst for complex copper is also very good when the pH value is between 7-12.

[0046] The catalysts prepared in Example 1, Example 2, Example 3 and Example 4 were respectively used to remove complex copper. Figure 5 It can be seen that the degradation effect of catalysts made with different calcium-iron molar ratios, when the mass ratio of calcium salt, iron salt and nickel salt is 1:1:2, the calcium-iron composite catalyst has a better effect in degrading and removing complex copper, and the removal rate of complex copper is close to 100% within one hour.

[0047] Example 1 was applied to the removal experiment of complex copper. Before the degradation experiment, shielding agents of the same concentration were added to the solution, wherein the shielding agents were ascorbic acid (ROS spectrum shielding agent), L-histidine ( 1 O2 shielding agent), methanol, tert-butyl alcohol, from Figure 6 It can be seen that when L-histidine was added during the degradation experiment, the degradation of complex copper was significantly inhibited, while other shielding agents did not have a significant effect. 1 O2 is the main active substance in the experimental system. The calcium iron composite catalyst prepared in Example 1 was used for EPR testing. The test results are shown in Figure 7 ,from Figure 7 It can be seen that when using TEMPO capture agent, a large number of 1:1:1 signal peaks appear, indicating that 1 O2 is the main active substance in the experimental system, which is consistent with the results of the shielding experiment.

[0048] Therefore, the present invention adopts the above-mentioned structure to prepare a nickel-iron-calcium composite catalyst for degrading pollutants in electroplating wastewater. The preparation cost is low, the preparation method is simple, the equipment requirements are low, the operability is good, the material structure is stable in the hypochlorous acid oxidation system, and there is no ion leaching of nickel, iron, calcium ions, etc.

[0049] The above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. Application of a nickel-iron-calcium composite catalyst in catalytic hypochlorous acid oxidation treatment of wastewater containing metal complexes, characterized in that: The following steps are involved: (1) adding nickel salt, iron salt and calcium salt in a certain weight ratio to distilled water and stirring to obtain solution A, mixing sodium hydroxide with distilled water to obtain solution B; adding solution B dropwise to solution A under magnetic stirring conditions, and continuously stirring to obtain solution C; in step (1), the mass ratio of Ca salt to distilled water is 1:50-200, the mass ratio of Fe salt to distilled water is 1:25-100, and the mass ratio of Ni salt to distilled water is 1:10-50; (2) transferring the solution C obtained in step (1) to a stainless steel high-pressure reactor lined with polytetrafluoroethylene, and performing a hydrothermal reaction to obtain a precipitate D; the hydrothermal reaction temperature in step (2) is 90 to 150° C., and the hydrothermal reaction time is 2 to 12 h; (3) washing the precipitate D obtained in step (2) with distilled water and anhydrous alcohol solution multiple times to obtain a precipitate E; (4) placing the precipitate E obtained in step (3) into a vacuum drying oven for constant temperature drying to obtain a dry solid F; (5) grinding the solid F obtained in step (4) into powder to obtain a nickel-iron-calcium composite catalyst; The nickel-iron-calcium composite catalyst is used for catalyzing hypochlorous acid oxidation to treat wastewater containing metal complexes.

2. The use of a nickel-iron-calcium composite catalyst according to claim 1 in catalyzing hypochlorous acid oxidation treatment of wastewater containing metal complexes, characterized in that: The calcium salt is one or more of calcium nitrate, calcium hypochlorite and calcium carbonate.

3. The use of a nickel-iron-calcium composite catalyst according to claim 1 in catalyzing hypochlorous acid oxidation treatment of wastewater containing metal complexes, characterized in that: The iron salt is one or more of ferric chloride, ferric sulfate and ferric nitrate.

4. The use of a nickel-iron-calcium composite catalyst according to claim 1 in catalyzing hypochlorous acid oxidation treatment of wastewater containing metal complexes, characterized in that: The nickel salt is one or more of nickel sulfate and nickel chloride.

5. The use of a nickel-iron-calcium composite catalyst according to claim 1 in catalyzing hypochlorous acid oxidation treatment of wastewater containing metal complexes, characterized in that: The mass ratio of the calcium salt to the iron salt is 1-15; the mass ratio of the calcium salt to the nickel salt is 1-25; and the mass ratio of the nickel salt to the iron salt is 1-20.

6. The use of a nickel-iron-calcium composite catalyst according to claim 1 in catalyzing hypochlorous acid oxidation treatment of wastewater containing metal complexes, characterized in that: The stirring steps in step (1) are all magnetic stirring, and the stirring time is continuous for 1 to 3 hours.

7. The use of a nickel-iron-calcium composite catalyst according to claim 1 in catalyzing hypochlorous acid oxidation treatment of wastewater containing metal complexes, characterized in that: In step (3), the precipitate is washed using a high-speed centrifuge at a rotation speed of 8000 to 12000 r / min.

8. The use of a nickel-iron-calcium composite catalyst according to claim 1 in catalyzing hypochlorous acid oxidation treatment of wastewater containing metal complexes, characterized in that: The temperature of the vacuum drying step in step (4) is 30 to 90° C., and the drying time is 6 to 18 hours.

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