CN111115763A

CN111115763A - Preparation of modified palladium cathode material and method for applying modified palladium cathode material in electrocatalysis

Info

Publication number: CN111115763A
Application number: CN202010013026.5A
Authority: CN
Inventors: 黄耀霈; 张永刚
Original assignee: Tianjin Polytechnic University
Current assignee: Tianjin Polytechnic University
Priority date: 2020-01-07
Filing date: 2020-01-07
Publication date: 2020-05-08

Abstract

The invention discloses a preparation method of electro-Fenton cathode material of a modified palladium electrode, which comprises the following steps: (1) pretreatment: soaking the foamed nickel in a 5% hydrochloric acid solution for ultrasonic cleaning for 30min, then ultrasonically cleaning the foamed nickel by using acetone and ethanol for 30min, and finally ultrasonically cleaning the foamed nickel by using deionized water for 30 min. (2) Electro-deposition: first, a solution containing 6mm HCLO was prepared₄And 3mmPdCl₂To which PdCl is added₂Polyethylene glycol with the molar ratio of 1: 3 is fully stirred to form a deposition solution; secondly, putting the cleaned foam nickel into a deposition solution at 20 ℃, and carrying out electrodeposition for 120min by using a three-electrode electrochemical workstation at a constant potential of 0.5V; finally, the samples were taken out after the electrodeposition was completed and dried in a vacuum oven at 60 ℃ for 6 hours. The invention has the advantages that: promotion ofThe organic pollutants can be efficiently degraded due to the electrocatalysis effect.

Description

Preparation of modified palladium cathode material and method for applying modified palladium cathode material in electrocatalysis

Technical Field

The invention belongs to an electro-deposition method for loading palladium nano particles, foam nickel is taken as a carrier, and the crystal morphology and the lattice structure of palladium deposited on the foam nickel are changed by regulating the type and the concentration of an additive to obtain a required electro-catalytic cathode material; the two-dimensional electrode reactor is used as a processing device, and the Phenacetin (PNT) is used as a target organic pollutant, so that the electrocatalysis efficiency is improved, the yield of oxidation products is increased, and the organic pollutant is efficiently and effectively degraded.

Background

As is well known, the earth is the only place where humans can live today, but it faces an extremely severe environmental problem-water resource problem. Water resource problems are one of the most compelling problems in the world. At present, the situation of water resources in China is very severe, due to rapid development of economy and rapid growth of population, the occupied amount of water resources per capita is very small, water resources at the south, north, east and west geographic positions are not uniformly distributed, water using efficiency in most industries is not high, the problem of water resources becomes a main obstacle restricting the way of sustainable development of China, and in addition, the problems of industrial wastewater discharge and pollution are increasingly aggravated, so that the dilemma of water resource shortage of China is further deepened. The industry is still an important support for supporting the economic development of China, but the produced wastewater consumes a large amount of fresh water resources and generates large-scale high-pollution wastewater which is difficult to treat.

With the development and improvement of wastewater treatment technology, biodegradable organic wastewater with simple components is effectively controlled, but the treatment of organic wastewater with difficult biodegradation, high salinity and high concentration still lacks economic and effective practical technology. With the development of wastewater treatment technology, many mature processes have been developed. At present, the treatment technology of organic wastewater includes physical method, chemical method, biological method and the like. These methods are suitable for treating wastewater with single component, good biochemical properties and low concentration, but they are challenging for high concentration of recalcitrant or toxic and harmful pollutants. The method has the advantages of high energy consumption, high treatment cost, complex operation, easy generation of secondary pollution and the like, and the effect of only using one method is not combined with a plurality of methods for use from the perspective of comprehensive management, so that the method is safe, reliable and good in effect. With the increasing awareness of the human environment, the standards for the emission of pollutants are becoming higher and higher, and new methods for treating these recalcitrant organic wastewaters are required. Therefore, developing new methods of research presents scientists with new challenges.

Electrocatalysis is a novel electrochemical advanced oxidation technology, and a strong oxidant hydroxyl radical (. OH) is generated on the surface of an electrode in a solution at the same time, so that most organic pollutants in a water body are subjected to non-selective oxidative decomposition. In addition, the reaction condition of the technology is mild, the technology can be carried out repeatedly at normal temperature generally, no toxic or harmful chemical reagent is required to be added in the reaction process, and the technology is a green and friendly degradation process. Has wide development space in the technical field of water treatment, in particular to the field of organic matters difficult to biodegrade.

In recent years, various scholars have carried out a great deal of research in the relevant field of electrocatalysis technology, but the current efficiency of a reaction system is generally low on the one hand because of the limitation of factors such as electrode materials, the concentration of dissolved oxygen in water and the like; on the other hand, Fe²⁺The cathode reduction regeneration performance is poor, a large amount of iron sludge is generated, the quality efficiency of a system is influenced, the process cost is increased by subsequent sludge treatment, almost all research achievements stay in laboratory research at present, and the further popularization is difficult. Thus, H of high current efficiency is optimized₂O₂Electrode materials and process conditions promoting Fe²⁺The reduction and regeneration of (2) is the key to the large-scale popularization of the electrocatalytic technology.

Disclosure of Invention

The invention mainly solves the technical problem of improving the crystal morphology modified cathode of the catalyst, increasing the current efficiency in an electrocatalysis system and thoroughly mineralizing organic pollutants.

The novel method of the invention is operated according to the following steps in sequence:

(1) the method adopts high-performance, high-specific surface area and high-porosity foamed nickel as a cathode carrier, and the foamed nickel is pretreated before preparation: ultrasonically cleaning with 5% hydrochloric acid, acetone, ethanol and deionized water for 30min, and vacuum drying.

(2) Preparing an electrode by an electrodeposition method, using a CHI660E electrochemical workstation, adopting a three-electrode system, taking a pretreated foamed nickel material as a working electrode, taking a platinum sheet as a counter electrode and a saturated calomel electrode as a reference electrode, performing electrodeposition work by adopting constant potential i-t parameters, and controlling the crystal morphology of palladium nanoparticles of a catalyst by regulating and controlling the concentration ratio of an additive (PEG-10000) to prepare the foamed nickel gas diffusion electrode of the palladium catalyst with a special crystal morphology.

(3) Through comparative analysis of performances of generating hydroxyl free radicals (OH), PNT removal rate and TOC removal rate by in-situ electrocatalysis of different electrodes of foamed nickel, unmodified palladium/foamed nickel and PEG modified palladium/foamed nickel for 3 minutes, an electrochemical oxidation action mechanism is discussed and verified.

(4) Study of electrocatalysis under different conditionsEfficiency of oxidation of PNT. The optimum reaction conditions of electrocatalysis are searched, (current density, pH, FeSO)₄Addition amount of Na₂SO₄The amount of (c) is added.

(5) And analyzing the degradation process, the first-order reaction kinetics and the energy consumption of the degradation PNT.

(6) And verifying the promoting effect of the electrode on an electrocatalysis system after the morphology of the Pd catalyst is changed.

The invention aims to search the water quality characteristics of the phenacetin wastewater and a reasonable and efficient electrocatalysis treatment process. Not only provides theoretical and technical support, but also fills up the blank of relevant research reports on degrading the pharmaceutical wastewater of the phenacetin; the method has more important social significance for the reclamation of pharmaceutical wastewater and the safety of an ecosystem, and provides a new idea for future electrocatalysis.

Detailed Description

The following is a specific example for further illustrating the methods described herein, but the invention is not meant to be so limited.

Example 1 the increase in current density resulted in a higher rate of degradation of the phenacetin as verified by a single factor experiment. When the current density is from 1mA/cm²Increased to 2.5mA/cm²When the method is used, the degradation rate of the phenacetin in the cathode is improved to 81.26%; it was demonstrated that as the current density continued to increase to 4mA/cm²On the other hand, the extent of degradation of the phenacetin is reduced, probably due to the high current density which causes a number of side reactions, including O₂Direct four-electron reduction reaction, hydrogen evolution reaction, H₂O₂And (4) carrying out decomposition reaction. These side reactions may react with O₂Compete with the main two electron reducing phase of (1), hindering H₂O₂Thereby inhibiting further increases in the degradation rate. Comprehensively considering the energy consumption and the rate of degradation, 2.5mA/cm is selected²For optimal current density.

Example 2 study of the effect of initial pH on the degradation of phenacetin, the change in concentration of phenacetin was first decreased and then increased as the pH increased from 1 to 9; when the pH value is 3, the concentration of the degraded phenacetin is lowestSince, in electrocatalytic systems, the precondition is that the system consists of a certain amount of H⁺Namely, the cathode electrocatalytic reaction is carried out under an acidic condition, but the hydrogen evolution side reaction is promoted to occur due to the low H + concentration in the system; when the pH is 9, H₂O₂Very low yield of (3), production of Fe (OH) in the system₃The precipitate, flocculent precipitate, is dispersed in the solution, which has a great hindrance to the reaction. Thus, the optimal pH for the degradation of phenacetin was determined to be 3, which was concluded to be consistent with the mechanism and theory of electrocatalysis.

Example 3 the effect of different iron ion concentrations on the removal of phenacetin was studied and the degradation curves at 0.01M, 0.05M, 0.1M were all very close as a whole, indicating a low concentration of Fe₂ ⁺The degree of influence is not very great. At 0.1MFe₂ ⁺When the removal effect of the phenacetin is slightly better than that of 0.01MFe₂ ⁺And 0.05MFe₂ ⁺The removal rate can reach 81.26 percent better. With Fe₂ ⁺If the addition of the catalyst is continued to 0.15M, the effect of the treatment is rather inferior to that of 0.1M, because Fe2 is generated in the OH formation reaction⁺And H₂O₂There is an optimum ratio. When Fe₂ ⁺When the dosage is proper, the generation of OH is obvious, but Fe₂ ⁺When the amount of the catalyst is too large, a side reaction occurs, and OH is consumed unnecessarily. Therefore, Fe₂ ⁺The best effect is obtained when the adding amount is 0.1 mol/L.

Example 4 study of Na₂SO₄Effect of electrolyte concentration on the degradation of phenacetin. Na (Na)₂SO₄When the concentration is increased from 0.01M to 0.20M, the concentration of the phenicol is 0.1M Na₂SO₄The removal efficiency is highest, and the concentration is degraded from 50mg/L to 9.37 mg/L. This phenomenon can be explained from the following two aspects. On one hand, the increase of the concentration of the electrolyte in a certain range is beneficial to the enhancement of electron transmission and mass transfer, thereby improving the reaction rate of electrocatalytic degradation; on the other hand, the improvement of the solution conductivity is beneficial to reducing the battery voltage and reducing the hydrogen evolution; and moreover, the energy consumption can be saved by reducing the voltage of the battery, and the application of the battery in the actual wastewater treatment is facilitated. However, N is further increaseda₂SO₄Concentrations, 0.15M and 0.2M, resulted in a decrease in the rate of degradation of the phenacetin. The possible reason for this is excessive Na₂SO₄The electrolyte may cause the cathode to be coupled with Na⁺Over-adsorption of Na₂SO₄Excessive salt encapsulation of the electrode will reduce the reactive sites and block the cathode H₂O₂And formation of OH.

Claims

1. A preparation method of a modified palladium cathode material and a method thereof in electrocatalysis application. The preparation method of the electro-Fenton cathode material is characterized by comprising the following steps: adopts a self-made electro-Fenton electrode reactor, adopts graphite as the anode of the reactor and adopts modified nano palladium catalyst loaded foam nickel as a catalytic cathode material, optimizes the process conditions of electrochemically degrading organic matters, and investigates the current density, the pH value and the [ Fe ]²⁺]、[Na₂SO₄]Influence of factors on the degradation effect of the phenacetin, and in addition, the first-order reaction kinetics of the change process of the ultraviolet spectrum are analyzed. The conclusion is as follows: the optimal reaction conditions were determined: current density 2.5mA/cm²、[Fe² ⁺]＝0.1mmol·L^-1pH 3 and [ Na ═₂SO₄]＝0.1mol·L^-1. Through UV-Vis spectral change analysis, the peak value of the phenacetin is gradually decreased along with the lapse of reaction time, and the phenacetin shows good degradation performance in electrochemical catalytic oxidation reaction. The process of degrading the phenacetin by the electricity-Fenton accords with the first-order reaction kinetics of degradation, the first-order reaction kinetics constant is 0.0493, R²Is 0.9971.

2. The preparation of the modified palladium cathode material of claim 1 comprising: (1) pretreatment: soaking the foamed nickel in a 5% hydrochloric acid solution for ultrasonic cleaning for 30min, then ultrasonically cleaning the foamed nickel by using acetone and ethanol for 30min, and finally ultrasonically cleaning the foamed nickel by using deionized water for 30 min. (2) Electro-deposition: first, a solution containing 6mm HCLO was prepared₄And 3mmPdcl₂Adding 1mM of pvp and 0.12g of polyethylene glycol to the aqueous solution, and fully stirring to form a deposition solution; secondly, putting the cleaned foam nickel into the deposition solution at 20 DEG CIn the method, electrodeposition is carried out for 120min by using a three-electrode electrochemical workstation with a constant potential of 0.5V; finally, the samples were taken out after the electrodeposition was completed and dried in a vacuum oven at 60 ℃ for 6 hours.

3. The method of claim 1, wherein the modified palladium cathode material is used in electrocatalytic applications, further characterized by: in the electrolysis of 3 different cathodes (Ni, Ni/Pd, modified Ni/Pd), H₂O₂The concentration of (c) varies with the electrolysis time. As the electrolysis proceeds, H₂O₂The content in the system is increased. At 0-80min, H₂O₂The concentration of (A) is continuously increased, and the concentration is in an equilibrium state after 80 min; for the modified palladium/nickel foam electrode system, H₂O₂The concentration of (B) was 6.91 mg.L, which reached a maximum after 120min^-1。

4. The method of claim 1, wherein the modified palladium cathode material is used in electrocatalytic applications, further characterized by: the effect of. OH yield, PNT removal, COD removal and TOC removal during electrolysis of 3 different cathodes (Ni, Ni/Pd, modified Ni/Pd) was analyzed.

5. The preparation of modified palladium cathode materials and their method of electrocatalytic application as set forth in claim 1 further characterized by: effect of different Current Density on Phenantenine degradation when Current Density is from 1mA/cm²Increased to 2.5mA/cm²When the method is used, the degradation rate of the phenacetin in the cathode is improved to 81.26%; it was demonstrated that as the current density continued to increase to 4mA/cm²On the other hand, the extent of degradation of the phenacetin is reduced due to the high current density which causes a number of side reactions, including O₂Direct four-electron reduction reaction, hydrogen evolution reaction, H₂O₂And (4) carrying out decomposition reaction. These side reactions may react with O₂Compete with the main two electron reducing phase of (1), hindering H₂O₂Thereby inhibiting further increases in the degradation rate.

6. The preparation of modified palladium cathode materials and their method of electrocatalytic application as set forth in claim 1 further characterized by: effect of different pH (1-9) values on the degradation of phenacetin. As the pH increases from 1 to 9, the change in concentration of the phenacetin is first smaller and then larger; when the pH value is 3, the concentration of the degraded phenacetin is the lowest.

7. The preparation of modified palladium cathode materials and their method of electrocatalytic application as set forth in claim 1 further characterized by: effect of different iron ion concentrations (0.01M, 0.05M, 0.1M) on Phenantoxetine removal at 0.1MFe²⁺When the removal effect of the phenacetin is slightly better than that of 0.01MFe²⁺And 0.05MFe²⁺The removal rate can reach 81.26 percent better. With Fe²⁺If the addition of the catalyst is continued to 0.15M, the effect of the treatment is rather inferior to that of 0.1M, because Fe is generated in the OH formation reaction²⁺And H₂O₂There is an optimum ratio.

8. The preparation of modified palladium cathode materials and their method of electrocatalytic application as set forth in claim 1 further characterized by: effect of different electrolyte concentrations on Phenacin degradation, Na₂SO₄When the concentration is increased from 0.01M to 0.20M, the concentration of the phenicol is 0.1M Na₂SO₄The removal efficiency is highest, and the concentration is degraded from 50mg/L to 9.37 mg/L.