Method for removing chlorinated PPCPs through electrochemical hydrodechlorination of Pd / NiMn-LDH-Ov / NF composite electrode

Abstract

The invention discloses a preparation method and application of a composite electrode for removing chlorinated PPCPs in water through electro-catalytic hydrodechlorination, and the preparation method of an electrochemical cathode comprises the following steps: placing foamed nickel in a mixed solution of nickel nitrate hexahydrate and manganese sulfate for electro-deposition, and after the reaction is finished, drying the foamed nickel to obtain a NiMn-LDH / NF electrode, and placing the NiMn-LDH / NF electrode and anhydrous sodium hypophosphite in a tubular furnace, carrying out calcination phosphorization in a nitrogen atmosphere, placing the electrode in a mixed solution of palladium chloride and sodium chloride, and carrying out electro-deposition palladium loading to finally obtain the Pd / NiMn-LDH-Ov / NF composite electrode. The Pd / NiMn-LDH-Ov / NF composite electrode prepared by the method has good electro-catalytic performance, the removal rate of losartan potassium can reach 96.45%, meanwhile, the Pd / NiMn-LDH-Ov / NF composite electrode has excellent recycling performance, and secondary pollution is avoided.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of electrochemical water treatment, in particular to a preparation method and application of a composite electrode for removing chlorinated PPCPs in water through electrocatalytic hydrogenation dechlorination BACKGROUND

[0002] Pharmaceutical and Personal Care Products (PPCPs) are composed of a variety of environmental chemicals, among which a large number of emerging chlorinated PPCPs are derived. These chlorinated PPCPs in water are ubiquitous, although their concentrations are very low. This type of new pollutants is persistent and highly toxic, and even at low concentrations, they still have high ecological toxicity. Therefore, their toxic effects on organisms have become one of the hotspots in the field of environmental pollution research. In the field of environmental protection, how to reduce the operating cost while improving the removal efficiency of chlorinated PPCPs s is an urgent issue to be solved at present. The electrocatalytic reduction dechlorination technology can only remove the carbon-chlorine bond on the pollutants, can effectively reduce the toxicity of chlorinated PPCPs s , and is considered as a promising advanced water treatment method because it is simple in equipment, low in energy consumption, green and free of secondary pollution.

[0003] Although the electrocatalytic hydrogenation dechlorination technology can rapidly and efficiently decompose chlorinated PPCPs, it still faces some core challenges. Among them, how to prepare a catalyst with high activity and stability has always been a difficulty. Palladium is a valuable precious metal. Placing palladium alone on the substrate to make an electrode may cause palladium particles to aggregate, thereby causing problems such as less active sites and low utilization rate. At the same time, the palladium on the foamed nickel is easy to fall off, which is not conducive to the long-term stable reaction and has the risk of secondary water pollution. SUMMARY

[0004] The application provides a preparation method and application of a composite electrode for removing chlorinated PPCPs in water through electrocatalytic hydrogenation dechlorination, the prepared electrode has good electrocatalytic performance and excellent cyclic use performance, and does not cause secondary pollution.

[0005] The application provides a preparation method of a composite electrode for removing chlorinated PPCPs in water through electrocatalytic hydrogenation dechlorination, characterized by comprising the following preparation steps:

[0006] S1: in a three-electrode system, taking foamed nickel as a working electrode, a platinum sheet electrode (3x3cm 2 ) as a counter electrode, and an Ag / AgCl electrode (3.0mol·L -1KCl) as a reference electrode, both of which are immersed in the electrodeposition solution, and electrodeposition is carried out at room temperature, and then the electrode is dried to obtain a NiMn-LDH / NF composite electrode;

[0007] S2: The NiMn-LDH / NF composite electrode and anhydrous sodium hypophosphite are placed in two square bores and placed downstream and upstream of a tube furnace. Calcination phosphorization is carried out under an N2 atmosphere to obtain a NiMn-LDH-Ov / NF composite electrode;

[0008] S3: The NiMn-LDH-Ov / NF composite electrode is used as a cathode, and a platinum sheet (1 cm x 2 cm) is used as an anode, both of which are immersed in a metal palladium deposition stock solution, and electrodeposition is carried out to obtain an electrode dried for standby, and a Pd / NiMn-LDH-Ov / NF composite electrode is prepared.

[0009] In some specific embodiments of the present application, the electrodeposition solution preparation method in step S1 is: 3.4884 g of nickel nitrate hexahydrate powder and 1.014 g of manganese sulfate powder are dissolved in deionized water, and the volume is made up to 100 mL in a volumetric flask.

[0010] In some specific embodiments of the present application, the electrodeposition time in step S1 is 30-180 s.

[0011] In some specific embodiments of the present application, in step S2, the heating rate under an N2 atmosphere is 2℃·min -1 to 300℃, and the reaction time is 2h.

[0012] In some specific embodiments of the present application, in step S2, the phosphorus doping amount is 0-18 mmol.

[0013] In some specific embodiments of the present application, in step S3, the preparation method of the metal palladium deposition stock solution is: 0.1773 g of palladium chloride powder and 0.1753 g of sodium chloride powder are dissolved in deionized water, and the volume is made up to 100 mL in a volumetric flask, and the palladium chloride is completely dissolved by stirring in a 40℃ water bath for 10h, and the solution is refrigerated for standby;

[0014] In some specific embodiments of the present application, the chlorinated PPCPs are losartan potassium.

[0015] Compared with the prior art, the excellent effects of the present application are:

[0016] 1. The composite electrode prepared in the present application reduces the amount of palladium used while ensuring high removal rate, reduces the implementation cost, and has good electrocatalytic activity.

[0017] 2. The composite electrode prepared in the present application can remove most of the chlorinated PPCPs in water after 2h of electrocatalytic hydrogenation dechlorination reaction.

[0018] 3. The composite electrode prepared by the method has good stability and is not prone to secondary pollution.

[0019] The electrocatalytic performance of the NiMn-LDH-Ov / NF composite electrode prepared in the application is evaluated by the removal rate of losartan potassium. The electrocatalytic hydrogenation dechlorination reaction of losartan potassium is carried out by taking the Pd / NiMn-LDH-Ov / NF composite electrode as a working electrode and a platinum sheet electrode (1*2 cm 2 ) as a counter electrode. 50 mL of solution is added to the anode chamber and the cathode chamber, the anode is 0.05 mol·L -1 Na2SO4 aqueous solution, and the cathode is a mixed solution of 20 mg·L -1 losartan potassium and 0.05 mol·L -1 Na2SO4·5H2O. During the reaction process, a stirring rod is added to the cathode chamber to make the reaction solution more uniform. The anode chamber and the cathode chamber are separated by a cation exchange membrane in order to prevent the diffusion of Cl- generated by the cathode electrolysis to the anode. The electrochemical hydrogenation dechlorination reaction is carried out in a 40℃ constant temperature water bath under a constant current of 7 mA. Each group of experiments is repeated three times to ensure the accuracy of the experiments.

[0020] Removal rate of losartan potassium

[0021] wherein C is the final concentration of losartan potassium, mg / L; C0 is the initial concentration of losartan potassium, mg / L; BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a SEM diagram of the Pd / NiMn-LDH-Ov / NF composite electrode;

[0023] Figure 2 is an influence relationship diagram of the removal of losartan potassium by the Pd / NiMn-LDH-Ov / NF composite electrode with different electrodeposition times;

[0024] Figure 3 is an influence relationship diagram of the removal of losartan potassium by the Pd / NiMn-LDH-Ov / NF composite electrode with different phosphorus doping amounts;

[0025] Figure 4 is an electrode stability diagram of the Pd / NiMn-LDH-Ov / NF composite electrode;

[0026] Figure 5 is a mechanism diagram of the Pd / NiMn-LDH-Ov / NF composite electrode. DETAILED DESCRIPTION

[0027] The application will be further described in detail below in conjunction with the embodiments and drawings. It should be understood that the following embodiments are only preferred embodiments of the application, and the scope of protection claimed by the application is not limited only to this.

[0028] Example 1: Preparation of a composite electrode for electrocatalytic hydrogenation dechlorination to remove chlorinated PPCPs in water, which is as follows:

[0029] S1: 3.4884 g of nickel nitrate hexahydrate powder and 1.014 g of manganese sulfate powder were weighed respectively, dissolved in a certain amount of deionized water, transferred to a 100 mL volumetric flask, and then placed at room temperature after constant volume.

[0030] S2: A three-electrode system was used, with foamed nickel as the working electrode, a platinum sheet electrode (3 × 3 cm 2 ) as the counter electrode, and an Ag / AgCl electrode (3.0 mol·L -1 KCl) as the reference electrode, all of which were immersed in the mixed solution of step S1. Electrodeposition was carried out at room temperature for 120 s at a constant voltage of 1.0 V, and then the electrode was dried for standby. The obtained electrode was named 120s-NiMn-LDH / NF;

[0031] S3: The NiMn-LDH / NF composite electrode and anhydrous sodium hypophosphite were placed in two square bores downstream and upstream of a tube furnace. The temperature was raised to 300℃ at a heating rate of 2℃·min -1 under N2, and the heating was maintained for 2 h. A NiMn-LDH-Ov / NF composite electrode was obtained;

[0032] S4: 0.1773 g of palladium chloride powder and 0.1753 g of sodium chloride powder were dissolved in deionized water, and then constant volume was performed in a 100 mL volumetric flask. The palladium chloride was completely dissolved by stirring in a 40℃ water bath for 10 h, and then the solution was refrigerated for standby;

[0033] S5: The NiMn-LDH-Ov / NF composite electrode was used as the cathode, and a platinum sheet (1 cm × 2 cm) was used as the anode, both of which were immersed in the palladium deposition reserve solution of step S4. An electrodeposition reaction was carried out to obtain a Pd / NiMn-LDH-Ov / NF composite electrode which was dried for standby.

[0034] Example 2: Characterization of the NiMn-LDH-Ov / NF composite electrode prepared in Example 1, which is as follows:

[0035] The NiMn-LDH-Ov / NF composite electrode was characterized by scanning electron microscopy (SEM) (as shown in Figure 1 ). The surface presents a multi-layer nanoflower structure, which significantly increases the specific surface area of the electrode, provides more active sites, promotes the dispersion of palladium on the surface of the catalyst, and improves the electrocatalytic performance.

[0036] Example 3: Investigating the effect of different electrodeposition times of the Pd / NiMn-LDH-Ov / NF composite electrode on the removal of losartan potassium. The details are as follows:

[0037] In this implementation example, a 20 mg / L aqueous solution of losartan potassium was prepared, and the potassium was removed using a composite electrode with electrodeposition times of 30 s, 60 s, 120 s, and 180 s. Liquid samples were periodically taken from the reactor, and the residual losartan potassium concentration was determined by high-performance liquid chromatography (HPLC). Please refer to the sampling time guidelines. Figure 2 Experimental results: The composite electrodes with electrodeposition times of 30s, 60s, 120s, and 180s achieved removal rates of 85.27%, 87.16%, 96.45%, and 89.16% for losartan potassium, respectively, with a deposition time of 120s showing the best removal efficiency. Prolonged electrodeposition times can lead to overly tight packing of NiMn-LDH nanosheets, which is detrimental to subsequent palladium loading and causes palladium agglomeration, also hindering the electrocatalytic hydrodechlorination reaction.

[0038] Example 3: Investigating the effect of different phosphorus doping amounts on the removal of losartan potassium in a Pd / NiMn-LDH-Ov / NF composite electrode. Details are as follows:

[0039] In this implementation example, a 20 mg / L aqueous solution of losartan potassium was prepared, and the potassium was removed using composite electrodes with phosphorus doping levels of 0 mmol, 6 mmol, 12 mmol, and 18 mmol, respectively. Liquid samples were periodically taken from the reactor, and the residual losartan potassium concentration was determined by high-performance liquid chromatography (HPLC). Please refer to the sampling time guidelines. Figure 3 Experimental results: Electrodes with phosphorus doping levels of 0 mmol, 6 mmol, 12 mmol, and 18 mmol achieved removal rates of 84.97%, 90.12%, 96.45%, and 95.16% for losartan potassium, respectively. Electrodes with phosphorus doping levels of 120 mmol showed the best removal efficiency for losartan potassium, and further increasing the phosphorus doping level had no significant effect on improving the removal efficiency.

[0040] Example 4: To investigate the stability of the Pd / NiMn-LDH-Ov / NF composite electrode in the electrocatalytic hydrodechlorination reaction, five consecutive electrocatalytic hydrodechlorination experiments were conducted on losartan potassium using the Pd / NiMn-LDH-Ov / NF composite electrode, each cycle lasting 120 min, while keeping the reaction conditions constant. Liquid samples were periodically taken from the reactor, and the residual losartan potassium concentration in the samples was determined by high-performance liquid chromatography (HPLC). Please refer to [reference needed for sampling time]. Figure 4The experimental results show that after 5 cycles, the removal efficiency of Pd / NiMn-LDH-Ov / NF composite electrode to losartan potassium still reaches 92.95%. With the increase of cycle number, the electrocatalytic performance of the electrode slightly decreases, but the electrode still has high catalytic dechlorination activity, showing excellent stability.

[0041] Example 5: To study the electrocatalytic reduction pathway of Pd / NiMn-LDH-Ov / NF composite electrode, a quenching experiment was carried out by using tert-butyl alcohol as a capture agent to verify the reaction pathway. When the concentration of TBA increases from 0 mol / L to 1.0 mol / L, the removal efficiency of Pd / NiMn-LDH-Ov / NF electrode to losartan potassium gradually decreases. When the concentration of TBA increases to 1.0 mol / L, the removal efficiency of losartan potassium decreases from 96.45% to 61.97%. This shows that in the process of electrocatalytic hydrogenation dechlorination, active H* plays a leading role and indirect reduction is carried out.

Claims

1. A method for preparing a catalyst for removing chlorinated PPCPs from water using electrocatalytic hydrodechlorination, the method comprising the following steps: S1: In a three-electrode system, using nickel foam as the working electrode and a platinum sheet electrode (3×3cm) 2 ) is the counter electrode, Ag / AgCl electrode (3.0 mol·L -1 KCl was used as the reference electrode. Both electrodes were immersed in the electrodeposition solution and electrodeposition was performed at room temperature. The electrodes were then dried to obtain the NiMn-LDH / NF composite electrode. S2: The NiMn-LDH / NF composite electrode and anhydrous sodium hypophosphite were placed in two boats, one downstream and one upstream of a tube furnace. Calcination and phosphating were performed under a N2 atmosphere to obtain the NiMn-LDH-Ov / NF composite electrode. S3: Using a NiMn-LDH-Ov / NF composite electrode as the cathode and a platinum sheet (1cm×2cm) as the anode, both are immersed in a palladium deposition reserve solution to carry out an electrodeposition reaction. The electrodes are then dried for later use, thus obtaining a Pd / NiMn-LDH-Ov / NF composite electrode.

2. The method for removing chlorinated PPCPs from water using electrocatalytic hydrogenation and dechlorination with a Pd / NiMn-LDH-Ov / NF composite electrode according to claim 1, characterized in that, The electrodeposition solution in step S1 is prepared by dissolving 3.4884g of nickel nitrate hexahydrate powder and 1.014g of manganese sulfate powder in deionized water and making up to 100mL in a volumetric flask.

3. The method for removing chlorinated PPCPs from water by electrocatalytic hydrogenation and dechlorination using a Pd / NiMn-LDH-Ov / NF composite electrode according to claim 1, characterized in that: In step S1, the electrodeposition time is 30–180 s.

4. The method for removing chlorinated PPCPs from water by electrocatalytic hydrogenation and dechlorination using a Pd / NiMn-LDH-Ov / NF composite electrode according to claim 1, characterized in that: In step S2, the temperature is 2°C·min under an N2 atmosphere. -1 The heating rate was increased to 300℃, and the reaction time was 2 hours.

5. The method for removing chlorinated PPCPs from water by electrocatalytic hydrogenation and dechlorination using a Pd / NiMn-LDH-Ov / NF composite electrode according to claim 1, characterized in that: In step S2, the phosphorus doping amount is 0–18 mmol.

6. The method for removing chlorinated PPCPs from water by electrocatalytic hydrogenation and dechlorination using a Pd / NiMn-LDH-Ov / NF composite electrode according to claim 1, characterized in that, The preparation method of palladium deposition stock solution in step S3 is as follows: Dissolve 0.1773g palladium chloride powder and 0.1753g sodium chloride powder in deionized water, make up to 100mL in a volumetric flask, stir in a 40℃ water bath for 10h to completely dissolve the palladium chloride, and store for later use.

7. The method for removing chlorinated PPCPs from water by electrocatalytic hydrogenation and dechlorination using a Pd / NiMn-LDH-Ov / NF composite electrode according to claim 1, characterized in that: The chlorinated PPCPs are losartan potassium.

Images