CN115849518A - Transition metal sewage treatment method and transition metal recovery method - Google Patents

Abstract

The invention discloses a transition metal sewage treatment method and a transition metal recovery method. A transition metal sewage treatment method comprises the following steps: under the conditions of light irradiation and electrification, treating the transition metal sewage by using a photocatalytic system comprising a photocatalytic anode, and depositing transition metal on the surface of the photocatalytic anode; the photocatalytic anode comprises conductive glass loaded with a titanium dioxide nanorod array. The transition metal complex breaking process is carried out in the anode chamber, when the photocatalysis anode is under the condition of illumination, photoproduction cavities with strong oxidizing property and active oxygen are generated, the transition metal complex is oxidized to separate organic groups from the transition metal, the organic groups are converted into inorganic matters, thereby realizing the removal of the transition metal complex and simultaneously finishing the deposition of the transition metal on the photoanode.

Description

Transition metal sewage treatment method and transition metal recovery method

technical field

The invention relates to the technical field of sewage treatment, in particular to a transition metal sewage treatment method and a transition metal recovery method.

Background technique

Nickel has the characteristics of high mechanical strength, corrosion resistance, good ductility, and high chemical stability. Electroplating nickel can form a stable coating on the surface of the plated parts, which has an ideal protective effect. Its structure is compact and meticulous, with strong corrosion resistance and wear resistance. Excellent properties, widely used in industry. At the same time, a large amount of complexing agents are often used in the production process of the nickel electroplating industry, and the heavy metals in the wastewater mainly exist in a complexed state. Compared with free heavy metal nickel, complexed heavy metal nickel is firmly bound to complexing agent ligands, and it is difficult to be effectively removed by traditional heavy metal treatment technologies, such as alkali precipitation, ion exchange and adsorption. Taking Ni(Ⅱ)-EDTA as an example, flocculation and ion exchange can only remove 5% of metal complexes, while for membrane filtration and electrodialysis technology, only the sewage can be concentrated, and Ni(Ⅱ)- The effective removal of EDTA will also produce secondary pollutants such as high-concentration metal complex concentrates. At the same time, due to its high stability, metal nickel complexes are difficult to be trapped by soil and sediment, and have higher mobility and long-distance transport capabilities than free metal ions in water environments. Excessive nickel in the water environment can affect the growth and development of plants, and even lead to the death of plants; excessive intake of nickel-containing substances can lead to nickel poisoning, which can cause serious diseases such as dermatitis, respiratory cancer, and degeneration of the human nervous system. Studies have shown that metal complexes can further enhance the biological toxicity of heavy metals to biological cells, bacteria and plants. When the nickel complex enters the water environment, due to its refractory biodegradation and high stability, it can remain in the water environment for a long time, and accumulate and pass through the food chain through bioaccumulation, thereby affecting the ecological environment and human health. Health has lasting and far-reaching consequences. Therefore, the research and development of new nickel complex wastewater treatment technology to realize the high-efficiency and low-consumption treatment and resource utilization of nickel complex wastewater not only has scientific research value, but also has great environmental significance.

Contents of the invention

In order to overcome the problem that nickel complex wastewater cannot be effectively treated in the prior art, the first aspect of the present invention provides a transition metal sewage treatment method, and the second aspect of the present invention provides a transition metal recovery method.

In order to achieve the above object, the technical scheme that the present invention takes is:

A first aspect of the present invention provides a transition metal sewage treatment method, comprising the following steps:

Under light irradiation and electrification, the transition metal sewage is treated with a photocatalytic system including a photocatalytic anode, and transition metals are deposited on the surface of the photocatalytic anode;

The photocatalytic anode includes conductive glass loaded with titania nanorod arrays.

Preferably, in the transition metal sewage treatment method, the conductive glass includes at least one of FTO conductive glass and ITO conductive glass.

Preferably, in this transition metal sewage treatment method, the loading amount of titanium element on the photocatalytic anode is 12-20 mg/cm ² ; further preferably, the loading amount of titanium element on the photocatalytic anode is 14-18 mg/cm ² .

Preferably, in the transition metal sewage treatment method, the transition metal sewage contains at least one of free metal ions and/or complexed metal ions of nickel, copper, manganese, and cobalt.

In the present invention, photocatalytic anodes are used to generate photogenerated holes with strong oxidative properties under the condition of light, and transition metals such as manganese (Mn ²⁺ ) ions, nickel (Ni ²⁺ ) ions, cobalt ( Co ²⁺ ) oxidation to trivalent manganese (Mn ³⁺ ) or tetravalent manganese (Mn ⁴⁺ ), tetravalent nickel (Ni ⁴⁺ ), trivalent cobalt (Co ³⁺ ) or tetravalent cobalt (Co ⁴⁺ ) Morphology, the corresponding transition metal-containing oxides are formed and adsorbed on the surface of the photocatalytic anode, so as to achieve the selective removal of transition metals and the enrichment of transition metals on the anode surface.

Preferably, in the transition metal sewage treatment method, the pH of the transition metal sewage is 7-12; further preferably, the pH of the transition metal sewage is 8-9.

Preferably, in this transition metal sewage treatment method, the complexing agent combined with the complexed metal ion includes at least one of EDTA, phosphate, hydroxycarboxylate, aminocarboxylate; further preferably, the complexing The complexing agent combined with state metal ions is EDTA.

Preferably, in this transition metal sewage treatment method, ultraviolet light is used for light irradiation; further preferably, weak ultraviolet light is used for light irradiation, and the wavelength of weak ultraviolet light is 320nm-400nm.

Preferably, in this transition metal sewage treatment method, direct current is used for electrification; the current density of direct current is 0.2mA/cm ² -2.0mA/cm ² . If the current is too small, the effect of breaking transition metal complexes in sewage is not obvious, and the removal effect of transition metals is not good. If the current is too large, although a good breaking effect can be achieved, it is a waste of power.

Preferably, in this transition metal sewage treatment method, the time for electrification and electrolysis is 120-200 minutes.

Preferably, in this transition metal sewage treatment method, the preparation method of photocatalytic anode comprises the following steps:

Put the titanium source solution and the conductive glass in the reaction container, and carry out the hydrothermal reaction to obtain the photocatalytic anode.

Preferably, in this photocatalytic anode preparation method, the conductive glass is cleaned before the reaction; the cleaning solution can be ultrapure water, acetone, alcohol or a mixed solution of any combination thereof, and the ultrasonic cleaning time is 10-30 minutes.

Preferably, in this photocatalytic anode preparation method, the titanium source solution is a tetrabutyl titanate solution, and the concentration of the tetrabutyl titanate solution is 2-4mol/L; further preferably, the concentration of the tetrabutyl titanate solution is is 2.5-3.5 mol/L; still more preferably, the concentration of the tetrabutyl titanate solution is 2.8-3.1 mol/L.

Preferably, in this photocatalytic anode preparation method, the hydrothermal reaction time is 4-6 hours; more preferably, the hydrothermal reaction time is 4.5-5.5 hours.

Preferably, in this photocatalytic anode preparation method, the temperature of the hydrothermal reaction is 500-600°C; more preferably, the temperature of the hydrothermal reaction is 520-580°C.

The second aspect of the present invention provides a transition metal recovery method, which includes the following steps: after the transition metal sewage treatment method above, apply a reverse current or take out the photoanode and place it in an acid solution to realize transition metal recovery.

The beneficial effects of the present invention are:

The transition metal sewage treatment method of the present invention can be used to break complexes of transition metal complexes. The process of breaking complexes of transition metal complexes in the present invention occurs in the anode chamber. When the photocatalytic anode is illuminated, it produces Photogenerated holes and reactive oxygen species are used to oxidize the transition metal complex to separate the organic group from the transition metal, and the organic group is converted into an inorganic substance, thereby realizing the removal of the transition metal complex, and at the same time, it is completed at the photoanode Deposition of transition metals.

The invention belongs to photoelectric catalysis, which can achieve the effect of saving electric energy; and adopts electric assisted photocatalysis, which can reduce the hole recombination rate, strengthen the generation process of photogenerated holes, and improve the processing efficiency of transition metal ions.

The invention can obtain the nickel oxide directly falling off the surface of the anode when removing high-concentration nickel ions or continuously removing low-concentration, and can realize direct recovery.

Description of drawings

Fig. 1 is the device diagram of the photocatalytic system of the embodiment.

FIG. 2 is a scanning electron micrograph of the photoanode of Example 1.

Fig. 3 is the photoanode energy spectrum analysis chart of embodiment 1.

Fig. 4 is the Ni(II)-EDTA degradation rate trend diagram of Example 2.

Attachment 1 marks:

100-first acrylic plate, 200-first spacer, 300-photoanode, 400-second spacer, 500-anode reaction chamber, 600-third spacer, 700-proton membrane, 800-fourth spacer , 900-cathode reaction chamber, 1000-the fifth spacer, 1100-the second acrylic plate.

Detailed ways

The content of the present invention will be described in further detail below through specific examples. The raw materials, reagents or devices used in the examples and comparative examples can be obtained from conventional commercial channels or obtained by prior art methods unless otherwise specified. Unless otherwise specified, experiments or testing methods are conventional methods in the art.

Adopt the photocatalytic system shown in accompanying drawing 1 to carry out transition metal sewage treatment, as shown in Figure 1, the whole reactor is assembled, sewage enters from the small hole above the anode reaction chamber 500, and the cathode reaction chamber 900 adds sodium bicarbonate buffer At the same time, direct current and ultraviolet light are turned on according to the reaction conditions. During the reaction, continuous sampling is carried out at the small hole above the anode reaction chamber 500. After the reaction is completed, the reacted sewage is taken out from the small hole above the anode reaction chamber 500 for correlation. Data detection.

Example 1

The present embodiment provides the preparation method of FTO deposition TiO _nanorod array (photoanode), specifically comprises the following steps:

Clean the FTO conductive glass ultrasonically for 20 minutes in a mixed solution composed of ultrapure water, acetone and isopropanol (the concentration of the solution is not required), and then place the ultrasonically cleaned FTO conductive glass in hydrochloric acid, ultrapure water and tetratitanate In a mixed solution of butyl ester (2.94mol/L), put it into a polytetrafluoroethylene pressure cooker, and put it in a drying oven to set the temperature at 550°C for hydrothermal reaction for 5 hours to prepare the FTO deposited _TiO2 nanorod array photoanode .

The scanning electron microscope image of the photoanode is shown in Figure 2, and the energy spectrum analysis image is shown in Figure 3. The photoanode prepared in this example is used in the following examples.

Example 2

A kind of treatment method that contains Ni(II)-EDTA sewage, concrete process is:

Using the photocatalytic system device shown in Figure 1, the FTO-deposited TiO _nanorod array is used as the photoanode, the platinum electrode is used as the cathode, and the Ni-EDTA electrolyte is 5ppm. The photocatalytic anode is irradiated with 384nm ultraviolet light and supplemented by 2.8mA direct current, adjust the pH of the solution to 8.5 with sulfuric acid and sodium hydroxide, electrolyze for 150 minutes, the degradation rate of Ni(II)-EDTA can reach 80%, and the recovery rate of cationic deposited nickel can reach 40%.

The recovery of Ni ²⁺ ions in the present invention occurs in the anode reaction chamber. When the device is working, since the alkali metal, alkaline earth metal ions and iron ions cannot be oxidized by photocatalysis, the deposition of alkali metal, alkaline earth metal ions and iron ions on the electrode can be avoided , to achieve selective recovery of Ni ²⁺ ions.

The invention utilizes the photocatalytic anode to generate photogenerated holes with strong oxidation property under the condition of light, and oxidizes divalent nickel (Ni ²⁺ ) ions in the anolyte to trivalent nickel (Ni ³⁺ ) or tetravalent nickel (Ni ⁴⁺ ) form, forming the corresponding nickel-containing oxide and adsorbing on the surface of the photocatalytic anode, thereby realizing the selective removal of metallic nickel and the enrichment of nickel on the anode surface.

Example 3

A kind of treatment method that contains Ni(II)-EDTA sewage, concrete process is:

Using the photocatalytic system device shown in Figure 1, the FTO-deposited _TiO2 nanorod array was used as the photoanode, the platinum electrode was used as the cathode, and the Ni(II)-EDTA electrolyte was 5ppm. With a direct current of 0 mA, the pH of the solution was adjusted to 8.5 with sulfuric acid and sodium hydroxide, and the electrolysis was performed for 150 minutes, and the degradation rate of Ni(II)-EDTA could reach 10%.

Example 4

A kind of treatment method that contains Ni(II)-EDTA sewage, concrete process is:

Using the photocatalytic system device shown in Figure 1, the FTO-deposited _TiO2 nanorod array is used as the photoanode, the platinum electrode is used as the cathode, and the Ni(II)-EDTA electrolyte of 5ppm is oxidized with sulfuric acid and hydrogen at a direct current of 2.8mA. The pH of the solution was adjusted to 8.5 by sodium, the electrolysis was performed for 150 minutes, the degradation rate of Ni(II)-EDTA was 30%, and the recovery rate of cationic deposited nickel could reach 10%.

Example 5

A treatment method for nickel ion-containing sewage, the specific process is:

Using the photocatalytic system device shown in Figure 1, the FTO-deposited _TiO2 nanorod array is used as the photoanode, the platinum electrode is used as the cathode, and the nickel nitrate electrolyte is 10ppm. Direct current, adjust the pH of the solution to 7 with sulfuric acid and sodium hydroxide, electrolyze for 120 minutes, and the removal rate of nickel ions can reach 90%.

Example 6

A treatment method for nickel ion-containing sewage, the specific process is:

Using the photocatalytic system device shown in Figure 1, the FTO-deposited _TiO2 nanorod array is used as the photoanode, the platinum electrode is used as the cathode, and the nickel nitrate electrolyte is 10ppm. direct current, adjust the pH of the solution to 7 with sulfuric acid and sodium hydroxide, electrolyze for 150 minutes, and the removal rate of nickel ions can reach 92%.

Example 7

A treatment method for nickel ion-containing sewage, the specific process is:

Using the photocatalytic system device shown in Figure 1, the FTO-deposited _TiO2 nanorod array is used as the photoanode, the platinum electrode is used as the cathode, and the nickel nitrate electrolyte is 10ppm. Direct current, adjust the pH of the solution to 7 with sulfuric acid and sodium hydroxide, electrolyze for 150 minutes, and the removal rate of nickel ions can reach 81%.

Example 8

A kind of recovery method of nickel ion, concrete process is:

Use the nickel oxide attached in the above-mentioned Example 2 as the photocatalytic anode, the platinum electrode as the cathode, and sodium sulfate as the electrolyte. The photocatalytic anode is irradiated with 384nm ultraviolet light and supplemented with a direct current of -1mA. After 1min, it adheres to the titanium dioxide The nickel oxide on the nanorod array photoanode is completely released.

Example 9

A kind of recovery method of nickel ion, concrete process is:

The titanium dioxide nanorod array photoanode deposited with nickel oxide after the reaction in Example 2 above was placed in the reactor, and 0.1M dilute sulfuric acid was added to react for 10 minutes, and the nickel oxide attached to the titanium dioxide nanorod array photoanode was completely electrolyzed. release, and complete the recovery.

The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the above-mentioned embodiment, and any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention , should be equivalent replacement methods, and should be included within the protection scope of the present invention.

Claims (10)

1. a transition metal sewage treatment method, is characterized in that, comprises the following steps: Under light irradiation and electrification, the transition metal sewage is treated with a photocatalytic system including a photocatalytic anode, and transition metals are deposited on the surface of the photocatalytic anode; The photocatalytic anode includes conductive glass loaded with titania nanorod arrays. 2 . The transition metal sewage treatment method according to claim 1 , characterized in that, the loading amount of titanium element on the photocatalytic anode is 12-20 mg/cm ² . 3. The transition metal sewage treatment method according to claim 1, characterized in that, the transition metal sewage contains at least one of free metal ions and/or complexed metal ions of nickel, copper, manganese, and cobalt. 4. The transition metal sewage treatment method according to claim 3, characterized in that the pH of the transition metal sewage is 7-12. 5. transition metal sewage treatment method according to claim 3, is characterized in that, the complexing agent that described complexed state metal ion is combined comprises at least in EDTA, phosphoric acid salt, hydroxycarboxylate, aminocarboxylate A sort of. 6. The transition metal sewage treatment method according to claim 1, characterized in that, said light irradiation adopts ultraviolet light. 7 . The method for treating transition metal sewage according to claim 1 , wherein direct current is used for the electrification; the current density of the direct current is 0.2mA/cm ² -2.0mA/cm ² . 8. the transition metal sewage treatment method according to claim 1 or 2, is characterized in that, the preparation method of described photocatalytic anode comprises the following steps: Put the titanium source solution and the conductive glass in the reaction container, and carry out the hydrothermal reaction to obtain the photocatalytic anode. 9. The transition metal sewage treatment method according to claim 8, characterized in that, the hydrothermal reaction time is 4-6h. 10. A transition metal recovery method, characterized in that it comprises the following steps: after being treated by the transition metal sewage treatment method described in any one of claims 1 to 9, applying a reverse current or taking out the photoanode and placing it in an acid solution , to achieve the recovery of transition metals.

Images