Electroreduction method of hexavalent chromium and application thereof

Abstract

The invention discloses an electroreduction method of hexavalent chromium and application of the electroreduction method, and belongs to the technical field of electrochemistry. The electroreduction method of the hexavalent chromium comprises the following steps: taking an active electrode as a working electrode, and carrying out electroreduction on the hexavalent chromium under an alternating voltage condition, the preparation raw materials of the active electrode comprise a hexavalent chromium adsorption material; the alternating voltage condition is that the positive potential and the negative potential are periodically converted. The hexavalent chromium adsorption material can adsorb hexavalent chromium, the hexavalent chromium adsorption material is prepared into the working electrode, and the hexavalent chromium is electrically reduced under the alternating voltage condition, so that the method has the advantages of high treatment rate and high treatment capacity, the hexavalent chromium can be effectively reduced into trivalent chromium, the removal rate of the hexavalent chromium is high, and the method is suitable for industrial production. The method provided by the invention has a good application prospect in chromium-containing wastewater treatment.

Description

Technical Field

[0001] The invention belongs to the technical field of electrochemistry, and in particular relates to a hexavalent chromium electroreduction method and application thereof. Background Art

[0002] Chromium salt is one of the important industrial raw materials. Its production and use process consumes a lot of water resources and produces a large amount of wastewater containing heavy metal chromium. Direct discharge into the water body will cause water pollution and aggravate the scarcity of water resources. Therefore, it is urgent to treat chromium-containing wastewater.

[0003] Chromium is usually present in trivalent and hexavalent states in water, of which hexavalent chromium (Cr(VI)) is highly toxic and highly mobile. The common treatment method is to reduce it to trivalent chromium (Cr(III)) with lower toxicity, such as chemical reduction, photocatalytic reduction, biological reduction and electroreduction. Electroreduction is a clean and green reduction method that directly uses electrons as reducing agents. It has the advantages of no need to add additional chemical reagents, mild reaction conditions, simple operation and low cost.

[0004] However, due to the non-negligible electrostatic repulsion between Cr(VI) oxygen-containing anions and the cathode during the electroreduction process, the reduction of Cr(VI) is hindered, resulting in a decrease in the Cr(VI) removal rate. Therefore, it is urgent to develop a Cr(VI) electroreduction method that effectively improves the Coulomb repulsion problem. Summary of the invention

[0005] In order to overcome at least one of the problems existing in the above-mentioned prior art, one of the objects of the present invention is to provide a method for the electro-reduction of hexavalent chromium, which can effectively suppress the Coulomb repulsion between Cr(VI) and the electrode during the electro-reduction process and improve the removal rate of hexavalent chromium.

[0006] A second object of the present invention is to provide an application of the above-mentioned hexavalent chromium electroreduction method.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] The first aspect of the present invention provides a method for electro-reduction of hexavalent chromium, comprising the following steps: using an active electrode as a working electrode, electro-reducing hexavalent chromium under alternating voltage conditions; the raw material for preparing the active electrode includes a hexavalent chromium adsorption material; the alternating voltage condition is a periodic change between positive potential and negative potential.

[0009] The principle of the present invention is that the hexavalent chromium adsorption material can adsorb hexavalent chromium, and the working electrode is prepared by using the hexavalent chromium adsorption material, and the hexavalent chromium is electro-reduced under alternating voltage conditions. When the potential is positive, the hexavalent chromium anions are adsorbed to the surface of the working electrode; when the potential changes to negative, a large amount of hexavalent chromium enriched on the electrode surface is reduced to trivalent chromium. As the electrode potential changes from positive to negative, the continuous conversion of the electrode surface electro-adsorption and electro-reduction process is realized during the treatment process, achieving the effect of alleviating the Coulomb repulsion phenomenon in the electro-reduction process.

[0010] Preferably, the positive potential is +0 to +2 V (vs. Ag / AgCl); more preferably, it is +0 to +0.8 V (vs. Ag / AgCl); and even more preferably, it is +0 to +0.4 V (vs. Ag / AgCl).

[0011] Preferably, the negative potential is -0.1 to -3 V (vs. Ag / AgCl); more preferably, it is -0.5 to -2 V (vs. Ag / AgCl); and even more preferably, it is -1.0 to -1.5 V (vs. Ag / AgCl).

[0012] Preferably, the ratio of the duration of the positive potential to the duration of the negative potential is 1:(0.5-8); more preferably, it is 1:(0.8-6); and even more preferably, it is 1:(1-4).

[0013] Preferably, within a single conversion cycle of the alternating voltage, the duration of the positive potential is 0.1 to 10 s; more preferably, 0.2 to 5 s; and even more preferably, 0.3 to 1 s.

[0014] Preferably, within a single conversion cycle of the alternating voltage, the duration of the negative potential is 0.1 to 10 s; more preferably, 0.2 to 8 s; and even more preferably, 0.3 to 6 s.

[0015] Preferably, the total time of the electro-reduction is 10 to 60 min; more preferably 12 to 40 min; and even more preferably 15 to 30 min.

[0016] Preferably, the hexavalent chromium is electro-reduced in the form of a hexavalent chromium solution.

[0017] Preferably, the concentration of the hexavalent chromium solution is 0.1 to 80 mg / L; more preferably, 5 to 50 mg / L.

[0018] Preferably, the pH value of the hexavalent chromium solution is 1-4; more preferably 2-3.

[0019] Preferably, the hexavalent chromium adsorption material is selected from modified chitosan materials; further preferably, the modified chitosan material includes phosphorus-modified chitosan materials, chitosan / polyaniline composite materials or a combination thereof.

[0020] Modified chitosan materials have good affinity for hexavalent chromium, and using them to prepare working electrodes can achieve good enrichment of hexavalent chromium. Among them, phosphorus-modified chitosan materials and chitosan / polyaniline composite materials have more excellent affinity for hexavalent chromium, which can achieve more enrichment and reduction of hexavalent chromium.

[0021] Preferably, the raw materials for preparing the phosphorus-modified chitosan material include a phosphorus modifier and chitosan.

[0022] Preferably, the phosphorus modifier is a phosphorus modifier containing a phosphorus cationic group; further preferably, the phosphorus modifier is selected from tetrakis hydroxymethyl phosphonium sulfate (THPS).

[0023] The phosphorus-containing cationic groups of the phosphorus modifier are grafted onto the chitosan molecules, which is beneficial to improving the adsorption capacity and adsorption rate of the material for hexavalent chromium-containing pollutants.

[0024] Preferably, the mass ratio of the phosphorus modifier to the chitosan is (30-50):1; more preferably (35-45):1.

[0025] Preferably, the phosphorus-modified chitosan material is prepared by a method comprising the following steps: dissolving chitosan in acid to obtain a chitosan solution, mixing a phosphorus-modifying agent and the chitosan solution, and heating the mixture to obtain the phosphorus-modified chitosan material.

[0026] Preferably, the reaction temperature of the heating reaction is 60-80°C; more preferably 65-75°C.

[0027] Preferably, the reaction time of the heating reaction is 10 to 50 min; more preferably, it is 20 to 40 min.

[0028] Preferably, the raw materials for preparing the chitosan / polyaniline composite material include aniline, an initiator and chitosan.

[0029] Preferably, the initiator includes at least one of ammonium peroxodisulfate, potassium dichromate, ferric chloride, manganese dioxide or benzoyl peroxide; further preferably, the initiator is selected from ammonium peroxodisulfate.

[0030] Preferably, the mass ratio of the aniline to the chitosan is (0.5-3):1; more preferably (1-2):1.

[0031] Preferably, the mass ratio of the aniline to the initiator is 1:(1-4); more preferably, it is 1:(2-3).

[0032] Preferably, the chitosan / polyaniline composite material is prepared by a method comprising the following steps: dissolving chitosan in acid to obtain a chitosan solution, mixing aniline, an initiator and the chitosan solution, and performing a polymerization reaction to obtain the chitosan / polyaniline composite material.

[0033] Preferably, the polymerization reaction temperature is 15 to 35°C; more preferably 20 to 30°C.

[0034] Preferably, the polymerization reaction time is 12 to 36 hours; more preferably, it is 18 to 30 hours.

[0035] Preferably, the raw materials for preparing the active electrode further include a binder, a conductive agent, a solvent and an electrode substrate.

[0036] Preferably, the binder is selected from at least one of polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), polyacrylic acid (PAA) or polyacrylonitrile (PAN); further preferably, the binder is selected from polyvinylidene fluoride (PVDF).

[0037] Preferably, the conductive agent includes at least one of conductive carbon black, acetylene black, carbon nanotubes, graphite or graphene; further preferably, the conductive agent is selected from conductive carbon black.

[0038] Preferably, the solvent is selected from an organic solvent; further preferably, the organic solvent includes at least one of N-methylpyrrolidone (NMP), dimethyl carbonate (DMC), tetrahydrofuran (THF) or methyl formate (MF); further preferably, the organic solvent is selected from N-methylpyrrolidone (NMP).

[0039] Preferably, the mass ratio of the hexavalent chromium adsorbing material to the binder is 1:(0.05-0.5); more preferably, it is 1:(0.1-0.3).

[0040] Preferably, the mass ratio of the hexavalent chromium adsorption material to the conductive agent is 1:(0.05-0.5); more preferably, it is 1:(0.1-0.3).

[0041] Preferably, the usage ratio of the hexavalent chromium adsorbent material to the solvent is 1 mg: (30-50) μL; more preferably, it is 1 mg: (35-40) μL.

[0042] Preferably, the electrode substrate is selected from carbon paper.

[0043] Preferably, the size of the electrode substrate is (1-5) cm×(1-5) cm; more preferably, it is (2-3) cm×(2-3) cm.

[0044] Preferably, the application density of the hexavalent chromium adsorbent on the electrode substrate is 0.4-1 mg / cm 2 ; More preferably, 0.51 to 0.83 mg / cm 2 .

[0045] Preferably, the active electrode is prepared by a method comprising the following steps: mixing a hexavalent chromium adsorbing material, a binder, a conductive agent and a solvent to obtain an electrode slurry, applying the electrode slurry on an electrode substrate, and drying to obtain the active electrode.

[0046] Preferably, the drying temperature is 40-80°C; more preferably 50-70°C.

[0047] Preferably, the drying time is 2 to 10 hours; more preferably, it is 4 to 8 hours.

[0048] Preferably, the drying method is vacuum drying.

[0049] The second aspect of the present invention provides an application of the method described in the first aspect of the present invention in the treatment of chromium-containing wastewater.

[0050] Preferably, the chromium-containing wastewater contains hexavalent chromium; further preferably, the concentration of hexavalent chromium in the chromium-containing wastewater is 0.1 to 80 mg / L; further preferably, it is 5 to 50 mg / L.

[0051] The beneficial effects of the present invention are as follows: the present invention utilizes hexavalent chromium adsorption material to adsorb hexavalent chromium, makes the hexavalent chromium into a working electrode, and electrically reduces the hexavalent chromium under alternating voltage conditions. The method has the advantages of fast processing rate and high processing capacity, can effectively reduce the hexavalent chromium to trivalent chromium, and has a high hexavalent chromium removal rate. The method provided by the present invention has good application prospects in the treatment of chromium-containing wastewater.

[0052] Specifically, compared with the prior art, the present invention has the following advantages:

[0053] (1) The present invention uses a material with good hexavalent chromium adsorption performance and a carbon paper substrate to prepare a working electrode, thereby increasing the specific surface area of ​​the electrode and the electrode's ability to enrich hexavalent chromium.

[0054] (2) The present invention uses an asymmetric alternating voltage to treat hexavalent chromium in chromium-containing wastewater. The reciprocating change of the electrode potential is accompanied by the cyclic alternation of adsorption, enrichment and reduction of hexavalent chromium anions on the surface of the working electrode, thereby effectively alleviating the electrostatic repulsion and improving the removal rate of hexavalent chromium.

[0055] (3) The method provided by the present invention has good applicability to medium and low concentrations of Cr(VI) and can achieve good Cr(VI) removal effect.

[0056] (4) Through simple immersion in chemical reagents, the materials can be regenerated and reused, which is more environmentally friendly and effectively reduces costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 This is a SEM image of the carbon paper of Example 1 of the present invention.

[0058] Figure 2 This is a SEM image of the phosphorus-modified chitosan electrode of Example 1 of the present invention.

[0059] Figure 3 This is a comparison chart of the removal effect of Cr(VI) under different voltage conditions in Example 1 of the present invention.

[0060] Figure 4 This is a comparison chart of the removal effect of Cr(VI) under different positive potential conditions in Example 1 of the present invention.

[0061] Figure 5 This is a comparison chart of the removal effect of Cr(VI) under different negative potential conditions in Example 1 of the present invention.

[0062] Figure 6 Schematic diagram of asymmetric alternating voltage according to embodiment 1 of the present invention.

[0063] Figure 7 This is a diagram showing the treatment effects at different Cr(VI) concentrations in Example 1 of the present invention.

[0064] Figure 8 This is a comparison chart of the removal effect of Cr(VI) under different voltage conditions in Example 2 of the present invention.

[0065] Fig. 9 This is a comparison chart of the removal effect of Cr(VI) under different positive potential conditions in Example 2 of the present invention.

[0066] Fig.10 This is a comparison chart of the removal effect of Cr(VI) under different negative potential conditions in Example 2 of the present invention. DETAILED DESCRIPTION

[0067] The content of the present invention is further described in detail below through specific examples. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the principles set forth in the present invention all belong to the scope of protection of the present invention. The specific process parameters and the like in the following examples are also only examples within a suitable range, that is, those skilled in the art can make a selection within a suitable range through the description herein, and are not limited to the specific data exemplified below. The raw materials, reagents or devices used in the following examples and comparative examples, unless otherwise specified, can all be obtained from conventional commercial sources, or can be obtained by existing known methods.

[0068] Example 1

[0069] A method for electroreduction of hexavalent chromium, the specific steps are as follows:

[0070] S1. Preparation of phosphorus-modified chitosan:

[0071] Add 2g of chitosan to 400mL of 0.1mol / L acetic acid solution and stir until it is completely dissolved. Add 100mL of 75wt% THPS solution to the chitosan solution, stir evenly and heat in a water bath to 70°C and keep for 30min. After the reaction solution is cooled, the precipitate is separated by centrifugation. Wash the precipitate with deionized water and then dry it in a vacuum drying oven at 80°C for 48h. The dried product is crushed using a grinder and passed through a 100-mesh sieve to obtain phosphorus-modified chitosan.

[0072] S2. Preparation of phosphorus-modified chitosan electrode:

[0073] Take 40 mg of the phosphorus-modified chitosan prepared in step S1, mix and grind with 5 mg of PVDF and 5 mg of conductive carbon black, then add 1500 μL of NMP solution and continue grinding until the slurry is mixed evenly. The slurry is evenly coated on a carbon paper of size 2.5 cm*2.5 cm washed with ethanol. The phosphorus-modified chitosan loading density of each electrode is 0.67 mg / cm 2 , and then dried in a vacuum drying oven at 60°C for 6 h.

[0074] S3. Treatment of Cr(VI) in water using phosphorus-modified chitosan electrodes under asymmetric alternating voltage conditions:

[0075] The phosphorus-modified chitosan electrode prepared in step S2 was used as the working electrode, the Pt sheet was used as the counter electrode, and the Ag / AgCl electrode was used as the reference electrode.

[0076] like Figure 1 As shown in the figure, the cleaned carbon paper is a smooth bundle of carbon fibers. Figure 2As shown, the surface of the electrode prepared by coating phosphorus-modified chitosan on the surface of carbon paper is loaded with a large amount of micron-sized phosphorus-modified chitosan.

[0077] like Figure 3 As shown, 50 mL of 50 mg / LCr(VI) with a pH of 2.9 was treated under the voltage conditions of -1.5 V DC voltage, +0 V (vs. Ag / AgCl) and -1.5 V (vs. Ag / AgCl) for 0.5 s and 0.5 s respectively (i.e. 1:1), +0 V (vs. Ag / AgCl) and -1.5 V (vs. Ag / AgCl) for 0.5 s and 1.0 s respectively (i.e. 1:2), +0 V (vs. Ag / AgCl) and -1.5 V (vs. Ag / AgCl) for 0.5 s and 2.0 s respectively (i.e. 1:4), +0 V (vs. Ag / AgCl) and -1.5 V (vs. Ag / AgCl) for 0.5 s and 4.0 s respectively (i.e. 1:8), and the treatment time was 60 min. Figure 3 It can be seen that compared with the common direct voltage electroreduction, the alternating voltage electroreduction achieved better results. Moreover, the best effect was achieved when the ratio of the positive and negative potential duration was 1:2, and the removal rate of Cr(VI) reached 99.2% after 60 minutes of treatment.

[0078] Furthermore, if Figure 4 As shown, the negative potential was fixed at -1.5 V, and the removal effect of the system on 50 mL of 50 mg / LCr(VI) with a pH of 2.9 was compared when the positive potential was +0 to +0.8 V. When the positive potential was +0 V, the best effect was achieved, and the removal rates of Cr(VI) were 75.5% and 99.0% at 10 min and 40 min, respectively.

[0079] Furthermore, if Figure 5 As shown in the figure, the positive potential was fixed at +0V, and the removal effect of the system on 50mL of 50mg / LCr(VI) with a pH of 2.9 was compared when the negative potential was -0.5 to -2.0V. When the negative potential was -1.0V or -1.5V, better results were achieved. After 40min of treatment, the Cr(VI) removal rates reached 99.5% and 99.0%, respectively. In view of the energy consumption problem, the asymmetric alternating voltage condition of +0V (vs.Ag / AgCl) for 0.5s and -1.0V (vs.Ag / AgCl) for 1.0s was used to obtain a better comprehensive effect. The voltage-time curve under this condition is shown in the figure. Figure 6 shown.

[0080] like Figure 7As shown, using the phosphorus-modified chitosan electrode prepared in step S2 of Example 1 to treat 50 mL of 5-50 mg / LCr(VI) at a pH of 2.9 under asymmetric alternating voltage conditions, the concentration of residual Cr(VI) can reach the discharge concentration standard (<0.5 mg / L) within 15-30 minutes, indicating the applicability of this method in treating medium and low concentration Cr(VI) contaminated wastewater.

[0081] Example 2

[0082] A method for electroreduction of hexavalent chromium, the specific steps are as follows:

[0083] S1. Preparation of chitosan / polyaniline composite materials:

[0084] Add 2.4g chitosan to 400mL of 1M HCl solution, stir ultrasonically until chitosan is completely dissolved, then add 3.7mL aniline and stir for 0.5h to make it evenly distributed. Take 9.128g ammonium persulfate and dissolve it in 400mL of 1M HCl solution, and stir ultrasonically until it is completely dissolved. Then slowly add the ammonium persulfate solution to the chitosan / aniline mixed solution and stir the reaction for 24h. Use suction filtration to separate the solid and liquid to obtain a dark green precipitate. Use 10% ethanol solution to repeatedly wash the dark green precipitate until the separated supernatant is colorless and transparent. The washed precipitate is placed in a 60℃ oven and dried for 48h, then crushed with a ball mill and sieved through a 100-mesh sieve to obtain a chitosan / polyaniline composite material.

[0085] S2. Preparation of chitosan / polyaniline composite electrode:

[0086] Take 40 mg of the chitosan / polyaniline composite material prepared in step S1, mix and grind it with 5 mg PVDF and 5 mg conductive carbon black, then add 1500 μL of NMP solution and continue grinding until the slurry is mixed evenly. The slurry is evenly coated on a carbon paper of size 2.5 cm*2.5 cm that has been washed with ethanol. The chitosan / polyaniline loading density of each electrode is 0.67 mg / cm 2 , and then dried in a vacuum drying oven at 60°C for 6 h.

[0087] S3. Treatment of Cr(VI) in water using chitosan / polyaniline composite electrode under asymmetric alternating voltage conditions:

[0088] The chitosan / polyaniline composite electrode prepared in step S2 was used as the working electrode, the Pt sheet was used as the counter electrode, and the Ag / AgCl electrode was used as the reference electrode.

[0089] like Figure 8As shown, 50 mL of 50 mg / LCr(VI) with a pH of 2.9 was treated under the voltage conditions of -1.5 V DC voltage, +0 V (vs. Ag / AgCl) and -1.5 V (vs. Ag / AgCl) for 0.5 s and 0.5 s respectively (i.e. 1:1), +0 V (vs. Ag / AgCl) and -1.5 V (vs. Ag / AgCl) for 0.5 s and 1.0 s respectively (i.e. 1:2), +0 V (vs. Ag / AgCl) and -1.5 V (vs. Ag / AgCl) for 0.5 s and 2.0 s respectively (i.e. 1:4), and +0 V (vs. Ag / AgCl) and -1.5 V (vs. Ag / AgCl) for 0.5 s and 4.0 s respectively (i.e. 1:8), and the treatment time was 60 min. Compared with the common direct voltage electroreduction, alternating voltage electroreduction achieved better results. Moreover, the best effect was achieved when the ratio of positive and negative potential duration was 1:2, and the removal rate of Cr(VI) reached 98.0% after 50 minutes of treatment.

[0090] Furthermore, if Fig. 9 As shown, the negative potential was fixed at -1.5 V, and the removal effect of the system on 50 mL of 50 mg / LCr(VI) with a pH of 2.9 was compared when the positive potential was +0 to +0.8 V. The effect was optimal when the positive potential was +0 V, and the removal rates of Cr(VI) were 69.1% and 99.3% at 10 min and 40 min, respectively.

[0091] Furthermore, if Fig.10 As shown, the positive potential was fixed at +0V, and the removal effect of the system on 50mL of 50mg / LCr(VI) with a pH of 2.9 was compared when the negative potential was -0.5 to -2.0V. Similarly, when the negative potential was -1.0V or -1.5V, better results were achieved. After 40min of treatment, the Cr(VI) removal rates reached 99.1% and 99.3%, respectively, and the kinetics were faster under the -1.5V condition. Therefore, for this electrode, the optimal asymmetric alternating voltage treatment condition is a periodic cycle of +0V (vs.Ag / AgCl) for 0.5s and -1.5V (vs.Ag / AgCl) for 1.0s.

[0092] The embodiment of the present invention uses a material with good hexavalent chromium adsorption performance and a carbon paper substrate to prepare a working electrode, which improves the specific surface area of ​​the electrode and the electrode's ability to enrich hexavalent chromium; and, in combination with an asymmetric alternating voltage to treat hexavalent chromium in chromium-containing wastewater, the reciprocating change of the electrode potential is accompanied by the adsorption enrichment and reduction cycle of hexavalent chromium anions on the surface of the working electrode, thereby effectively alleviating the electrostatic repulsion and improving the removal rate of hexavalent chromium. In addition, the method provided in the embodiment of the present invention has good applicability to medium and low concentrations of Cr(VI), and can achieve good Cr(VI) removal effects. Through simple chemical reagent immersion, the regeneration and reuse of materials can be achieved, which is more environmentally friendly and effectively reduces costs.

[0093] In summary, the present invention utilizes hexavalent chromium adsorption material to adsorb hexavalent chromium, makes it into a working electrode, and electro-reduces the hexavalent chromium under alternating voltage conditions. This method has the advantages of fast processing rate and high processing capacity, can effectively reduce hexavalent chromium to trivalent chromium, and has a high hexavalent chromium removal rate. The method provided by the present invention has good application prospects in the treatment of chromium-containing wastewater.

Claims

1. A method for electroreduction of hexavalent chromium, characterized in that: The method comprises the following steps: using the active electrode as the working electrode to electro-reduce hexavalent chromium under alternating voltage conditions; the raw material for preparing the active electrode comprises a hexavalent chromium adsorption material; The alternating voltage condition is that positive potential and negative potential are periodically switched.

2. The method according to claim 1, characterized in that The positive potential is +0 to +2 V (vs. Ag / AgCl); And / or, the negative potential is -0.1 to -3 V (vs. Ag / AgCl); And / or, the ratio of the duration of the positive potential to that of the negative potential is 1:(0.5-8).

3. The method according to claim 1, characterized in that The total time of the electroreduction is 10 to 60 minutes.

4. The method according to claim 1, characterized in that The hexavalent chromium is electro-reduced in the form of a hexavalent chromium solution; preferably, the concentration of the hexavalent chromium solution is 0.1-80 mg / L; and / or the pH value of the hexavalent chromium solution is 1-4.

5. The method according to claim 1, characterized in that The hexavalent chromium adsorption material is selected from modified chitosan materials.

6. The method according to claim 5, characterized in that The modified chitosan material includes phosphorus-modified chitosan material, chitosan / polyaniline composite material or a combination thereof.

7. The method according to claim 6, characterized in that The raw materials for preparing the phosphorus-modified chitosan material include a phosphorus modifier and chitosan; the phosphorus modifier is preferably a phosphorus modifier containing a phosphorus cationic group; And / or, the raw materials for preparing the chitosan / polyaniline composite material include aniline, an initiator and chitosan.

8. The method according to claim 1, characterized in that The raw materials for preparing the active electrode also include a binder, a conductive agent, a solvent and an electrode substrate.

9. The method according to claim 8, characterized in that The mass ratio of the hexavalent chromium adsorption material to the binder is 1:(0.05-0.5); and / or, the mass ratio of the hexavalent chromium adsorption material to the conductive agent is 1:(0.05-0.5); and / or, the usage ratio of the hexavalent chromium adsorbent material to the solvent is 1 mg: (30-50) μL; And / or, the application density of the hexavalent chromium adsorbent material on the electrode substrate is 0.4-1 mg / cm 2 .

10. Use of the method according to any one of claims 1 to 9 in the treatment of chromium-containing wastewater.

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