CN102701329A - A kind of preparation method and application of porous nanocrystalline electrode - Google Patents

Abstract

The invention discloses a porous nanocrystalline Ti/SnO₂-Sn/Ce-PbO₂A preparation method of an electrode and a method for degrading and mineralizing perfluorooctanoic acid in water by using the electrode, belonging to the technical field of electrochemistry. With porous nanocrystalline Ti/SnO₂-Sn/Ce-PbO₂The electrode is an anode, Ti or 304 stainless steel is a cathode, and the electrolytic oxidation treatment is carried out on the wastewater containing the perfluorooctanoic acid, and the method is characterized by efficiently mineralizing the perfluorooctanoic acid under mild conditions. The invention adopts an electrochemical oxidation method, and has the advantages of simple process flow, convenient operation, mild reaction conditions, good treatment effect, stability and reliability, and easy realization of industrial application. The porous nanocrystalline Ti/SnO adopted₂-Sn/Ce-PbO₂The electrode has the advantages of strong oxidizing ability, long service life, easy processing, low price and the like.

Description

A kind of preparation method and application of porous nanocrystalline electrode

technical field

The invention belongs to the technical field of electrochemistry, and in particular relates to a preparation method of a porous nanocrystal electrode and a method for electrochemically oxidizing and efficiently mineralizing perfluorooctanoic acid in water.

Background technique

Perfluorooctanoic acid (PFOA, C7F15COOH) has been produced and used for more than fifty years as a surfactant, antifouling agent, additive, foam fire extinguishing agent, polymer emulsifier and insecticide. As one of the main destinations of perfluorinated compounds (PFCs) in the environment, perfluorooctanoic acid is widely present in natural water bodies, sediments, animals and human bodies due to its stable chemical properties, non-volatile and non-degradable characteristics of the ecosystem. Threats to the ecological environment and human health. At present, global PFOA pollution and its impact on human health have attracted great attention from governments and the scientific community. In June 2000, the U.S. Environmental Protection Agency (USEPA) began to notice the possible harm of PFOA and proposed low-level PFOA and its salts. Exposure may be harmful to human health, and PFOA will remain in the human body for a long time. Therefore, according to the "US Toxic Substances Control Act", PFOA was listed in the list of banned chemicals in 2003. On December 30, 2009, USEPA released the first A Chemicals Action Plan will address the health and environmental concerns caused by long-chain PFCs, including PFOA. In addition, on December 27, 2006, the European Union jointly issued the "Instructions on Restricting the Sales and Use of Perfluorooctane Sulfonic Acid" in the European Parliament and the Council of Ministers, suspecting that PFOA and its salts also have substances similar to PFOA. sulphonic acid risk levels and pledged to reduce emissions of PFOA and its content in products by 95% by 2010 and to eliminate it completely by 2015.

At present, there is only one relevant domestic patent record for the degradation technology of perfluorooctanoic acid in water, the patent application number is 200510011126.X (authorized announcement number CN 100347137C), and the name is "a method for defluorination and degradation of perfluorinated compounds" , discloses a degradation method for photolysis and photocatalysis of perfluorooctanoic acid or perfluorooctane sulfonate under 185nm and 172nm ultraviolet conditions.

So far, there is no report on the high-efficiency mineralization and purification technology of PFOA in water by electrochemistry.

Contents of the invention

The purpose of the present invention is to prevent and control the environmental pollution of perfluorooctanoic acid, aiming at the deficiencies of the prior art, to provide a new purification technology capable of efficiently mineralizing perfluorooctanoic acid in water under mild conditions.

The object of the present invention is achieved in that a kind of porous nanocrystalline Ti/SnO ₂ -Sn/Ce-PbO ₂ electrode preparation method comprises the following steps:

① Ti substrate pretreatment: Firstly, sand the Ti substrate with sandpaper to remove surface oxides, then immerse in 5% to 10% sodium hydroxide solution at 100°C for 1 to 2 hours to remove surface oil stains, take it out and wash it with distilled water , and then etched in 10% to 15% 100°C oxalic acid solution for 2 to 3 hours to obtain a gray flat surface;

②Preparation of tin-antimony polymerization precursor sol: Dissolve a certain amount of citric acid in ethylene glycol at a temperature of 50-70°C (the molar ratio of citric acid to ethylene glycol is 1:4-6), and after complete dissolution Keep the temperature constant for 30-60 minutes to fully lipidate, then heat to 90°C, add SnCl ₄ 5H ₂ O and SbCl ₃ (the molar ratio of citric acid to SnCl ₄ 5H ₂ O is 1:0.05-0.1; SnCl ₄ 5H ₂ The molar ratio of O to _SbCl3 is 1:0.1～0.2), fully stirred until the dissolution is completed, then the temperature is raised to 100°C and kept at a constant temperature for 1～3h, and the polymer precursor sol containing tin and antimony is obtained after natural cooling;

③Preparation of Ti/SnO ₂ -Sb electrode: The prepared tin-antimony-containing polymeric precursor sol is coated on the Ti substrate by the pulling method, and then kept in an oven at 120-160°C for 10-20 minutes to turn the sol into a gel. Then transfer to a muffle furnace at 450-550°C and roast in an air atmosphere for 10-30 minutes, take it out for natural cooling, wash and dry, and then repeat the previous process, repeating 20-40 times, and the last roasting time is 1-3 hours and natural annealing, that is Prepare Ti/SnO ₂ -Sb electrode;

④Preparation of porous nanocrystalline Ti/SnO ₂ -Sn/Ce-PbO ₂ electrode: first prepare electrodeposition solution, composed of 0.5mol/L lead nitrate, 0.001mol/L cerium nitrate and 0.2-1.0g/L sodium fluoride, and use Adjust the pH value to 1.2-1.8 with nitric acid, use the Ti/SnO ₂ -Sb electrode as the base electrode, use Ti as the cathode, and conduct electrodeposition at a current of 100-200A/ ^m2 for 10-30 minutes to prepare porous nanocrystalline Ti/ SnO ₂ -Sn/Ce-PbO ₂ electrode.

Technical scheme for electrochemical oxidation of PFOA in mineralized water: use 1.0-2.0 g/L sodium perchlorate as supporting electrolyte to prepare a solution containing 5-1000 mg/L PFOA. Use the prepared porous nanocrystalline Ti/SnO ₂ -Sn/Ce-PbO ₂ electrode as an anode, and use Ti or 304 stainless steel as a cathode to perform electrochemical oxidation and mineralization treatment on wastewater containing perfluorooctanoic acid at room temperature. The operating current is 5-40mA/ cm ² , and the distance between the plates is 5-20mm.

It can be seen from the above-mentioned technical solution provided by the present invention that the method for efficiently mineralizing PFOA in water provided by the present invention has the advantages of simple process flow, convenient operation, mild reaction conditions, good treatment effect and stable reliability due to the use of electrochemical oxidation method. Easy to realize industrial application. The adopted porous nanocrystalline Ti/SnO ₂ -Sn/Ce-PbO ₂ electrode has the advantages of strong oxidation ability, long service life, easy processing, low cost and the like.

Description of drawings

Fig. 1 is the surface morphology of the porous nanocrystalline Ti/SnO ₂ -Sn/Ce-PbO ₂ electrode.

Fig. 2 is a device diagram of an electrochemical oxidation highly efficient mineralization of perfluorooctanoic acid in water provided by an embodiment of the present invention, wherein: 1-DC power supply, 2-electrolyzer, 3-terminal, 4-gas outlet, 5-cathode, 6-anode .

Figure 3 is a graph showing the relationship between the degradation and mineralization effects of electrochemical oxidation on perfluorooctanoic acid and the treatment time.

Detailed ways

Embodiments of the present invention will be further described in detail below in conjunction with the accompanying drawings.

A method for electrochemically oxidizing and efficiently mineralizing perfluorooctanoic acid in water according to the present invention, and its preferred specific implementation method includes steps:

Porous nanocrystalline Ti/SnO ₂ -Sn/Ce-PbO ₂ electrode preparation:

① First, polish the Ti substrate with 200-mesh sandpaper, then immerse it in 8% sodium hydroxide solution at 100°C for 1 hour, take it out and wash it with distilled water, and then etch it in 10% oxalic acid solution at 100°C for 2.5 hours;

② Dissolve a certain amount of citric acid in ethylene glycol at 60°C, keep the temperature constant for 30 minutes after complete dissolution, then heat to 90°C, add SnCl ₄ 5H ₂ O and SbCl ₃ , stir well until the dissolution is complete, Then raise the temperature to 100°C and keep the temperature constant for 1-3 hours. After natural cooling, a polymeric precursor sol containing tin and antimony can be obtained, wherein ethylene glycol:citric acid:SnCl ₄ 5H ₂ O:SbCl ₃ (molar ratio) is 120:30 :9:1;

③The prepared tin-antimony-containing polymer precursor sol was coated on the Ti substrate by the pulling method, and then kept in an oven at 140°C for 15 minutes to convert the sol into a gel, and then transferred to a muffle furnace at 500°C in an air atmosphere. Medium-roasting for 15 minutes, taking it out for natural cooling, cleaning and drying, and then repeating the previous process for 20 times. The last time of calcination was 2 hours and natural annealing, and the Ti/SnO ₂ -Sb electrode was obtained;

④ Prepare an electrodeposition solution composed of 0.5mol/L lead nitrate, 0.001mol/L cerium nitrate and 0.5g/L sodium fluoride, adjust the pH value to 1.4 with nitric acid, use Ti/SnO ₂ -Sb electrode as the base electrode, and Ti is the cathode, and the porous nanocrystalline Ti/SnO ₂ -Sn/Ce-PbO ₂ electrode is prepared by electrodeposition at a current of 200A/m ² for 20 minutes.

The surface morphology of the prepared porous nanocrystalline Ti/SnO ₂ -Sn/Ce-PbO ₂ electrode is shown in Fig. 1 . It can be seen from Figure 1 that the surface of the electrode is porous, which is conducive to the adsorption of pollutants on the surface of the electrode; the particle size of PbO ₂ is hundreds of nanometers, which is nano-state and the surface is dense, which greatly increases the reactive sites.

Electrochemical oxidation of perfluorooctanoic acid in mineralized water technical scheme: prepare a solution containing 1.4g/L sodium perchlorate and 100mg/L perfluorooctanoic acid. Take 100mL and pour it into the electrolytic cell shown in Figure 2. The prepared porous nanocrystalline Ti/SnO ₂ -Sn/Ce-PbO ₂ electrode is used as the anode, and Ti or 304 stainless steel is used as the cathode. Both electrodes have an area of 60cm ² . Adjust the distance between the plates to 10mm, turn on the power supply and adjust the current to keep the output current density at 10mA/cm ² , perform electrolytic treatment at room temperature for 90min, and use for analysis at intervals of 15-30min.

Figure 3 is the relationship between the degradation and mineralization effect of the present invention on perfluorooctanoic acid and the treatment time. It can be seen from Figure 3 that the removal rate of PFOA after 90min treatment is greater than 99.9%, and the defluorination rate is close to 90%, which is equivalent to 15 fluorine contained in the PFOA molecule 13.5 fluorines have been shed into the solution with a 92.6% reduction in TOC.

The above description of the embodiments is for those of ordinary skill in the technical field to understand and apply the present invention. Any person skilled in the art can easily make various modifications to this embodiment within the technical scope disclosed in the present invention, and apply the principles described here to other embodiments without creative efforts. Therefore, the present invention is not limited to the embodiments herein, and improvements and modifications made without departing from the scope of the present invention shall be covered within the protection scope of the present invention.

Claims (2)

1. a porous is received brilliant Ti/SnO ₂-Sn/Ce-PbO ₂The preparation method of electrode is characterized in that, may further comprise the steps:

Ti substrate pretreated: at first be that the Ti matrix is polished with sand paper; Remove oxide on surface; Immerse 1～2h in 100 ℃ 5%～10% the sodium hydroxide solution then,, take out and clean with zero(ppm) water to remove the greasy dirt on surface; Etching 2～3h in 100 ℃ of oxalic acid solutions of 10%～15% afterwards is to obtain the grey even curface;

The polymerization forerunner colloidal sol preparation of tin antimony: under 50～70 ℃ of temperature; A certain amount of Hydrocerol A is dissolved in (Hydrocerol A and terepthaloyl moietie mol ratio are 1: 4～6) in the terepthaloyl moietie, and dissolving back steady temperature 30～60min is with abundant fatization fully; Be heated to 90 ℃ then, add SnCl ₄5H ₂O and SbCl ₃, Hydrocerol A and SnCl ₄5H ₂The O mol ratio is 1: 0.05～0.1; SnCl ₄5H ₂O and SbCl ₃Mol ratio is 1: 0.1～0.2, fully stirs until accomplishing dissolving, is warming up to 100 ℃ and constant temperature 1～3h afterwards, promptly obtains the polymeric precursor colloidal sol of stanniferous antimony behind the naturally cooling;

Ti/SnO ₂-Sb electrode preparation: adopt and draw formulation that the polymeric precursor colloidal sol of the stanniferous antimony of preparation is overlayed on the Ti matrix; In 120～160 ℃ baking oven, keep 10～20min to make colloidal sol transfer gel to afterwards; Change in 450～550 ℃ of retort furnaces roasting 10～30min in air atmosphere then over to, repeat preceding process again, 20～40 times repeatedly after taking out the naturally cooling cleaning, drying; 1～3h and annealing naturally promptly make Ti/SnO during roasting for the last time ₂-Sb electrode;

Porous is received brilliant Ti/SnO ₂-Sn/Ce-PbO ₂Electrode preparation: at first prepare electrodeposit liquid, consist of 0.5mol/L lead nitrate, 0.001mol/L cerous nitrate and 0.2～1.0g/L Sodium Fluoride, and with nitre acid for adjusting pH value to 1.2～1.8, with Ti/SnO ₂-Sb electrode is negative electrode as base electrode with Ti, is 100～200A/m at electric current ²Under carry out galvanic deposit 10～30min and promptly prepare porous and receive brilliant Ti/SnO ₂-Sn/Ce-PbO ₂Electrode.

2. the method for Perfluorocaprylic Acid in the electrochemical oxidation degree of depth mineralized water is characterized in that, is supporting electrolyte with 1.0～2.0g/L sodium perchlorate, receives brilliant Ti/SnO with the porous of preparation in the claim 1 ₂-Sn/Ce-PbO ₂Electrode is an anode, is that negative electrode at room temperature carries out the processing of electrochemical oxidation mineralising to containing Perfluorocaprylic Acid waste water with Ti or 304 stainless steels, and actuating current is 5～40mA/cm ², the electrode pad spacing is 5～20mm.

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