CN101302051B - A graphite electrode for electrochemical treatment of phenolic wastewater - Google Patents

Abstract

The invention discloses a graphite electrode for phenolic wastewater electrochemistry treatment. The electrode uses graphite, epoxy resin and firming agent as main raw material and is prepared by the steps of mixing, molding, solidification, roasting, activation and re-roasting, wherein, the activation is electrochemical activation. The graphite electrode has high electrochemical activation for phenol in water, shows good removing effect and also has good removing effect on an intermediate product degraded by the phenol. The novel graphite electrode has widespread raw material, low price, simple processing and manufacturing process and the marked effect of phenolic wastewater treatment and can be used as the electrode for treating the phenolic wastewater by an electrochemical method.

Description

A graphite electrode for electrochemical treatment of phenolic wastewater

technical field

The invention belongs to the field of organic wastewater treatment, and in particular relates to a graphite electrode for electrochemical treatment of phenol-containing wastewater.

Background technique

With the rapid development of modern industry and agriculture, a large amount of organic wastewater is produced every day. If the generated organic wastewater is discharged directly without treatment, it will pollute the environment and endanger human health. Phenol is an important industrial raw material, which is widely used in all aspects of the national economy. Phenol can be used to make phenolic resin and caprolactam, and can also be used to produce halogenated phenols. The obtained chlorophenols can be used as raw materials for the production of herbicides such as 2,4-dichlorophenoxyacetic acid and 2,4,5-trichlorophenoxyacetic acid, wood preservatives, acaricides, leather preservatives and fungicides agent etc. Phenol can also be used to prepare alkylphenols and further prepare alkylphenols and formaldehyde polymers, which can be used as antioxidants, nonionic surfactants, plasticizers, and petroleum product additives. Phenol is also a raw material for many medicines (such as salicylic acid, aspirin and sulfa drugs, etc.), synthetic spices and dyes. In addition, dilute aqueous solutions of phenol can be directly used as antiseptics and disinfectants.

If the wastewater containing phenol is directly discharged without treatment, it will cause harm to aquatic organisms and affect human health through the food chain. Phenol has become one of the 129 priority pollutants listed by the U.S. Environmental Protection Agency due to its high toxicity, high oxygen demand (theoretical oxygen demand per mg of phenol is 2.38 mg) and refractory biodegradability. my country will also contain Phenol wastewater is listed as one of the harmful wastewater that needs to be addressed. Research and development of economical and practical phenol removal methods have very important practical significance. Phenol is a kind of organic matter that is difficult to treat thoroughly. At present, the main treatment methods include biological method, coagulation precipitation method, activated carbon adsorption method, ozone oxidation method, foam separation method, ion exchange method, reverse osmosis method and ultrafiltration method. In the methods, either the treatment effect is poor, the cost is too high, or there is secondary pollution, and the follow-up treatment is difficult, which makes it difficult for these methods to be practically popularized and applied.

Advanced Oxidation Technology (AOPs) can effectively degrade phenolic wastewater. At present, it is recognized that the AOPs with outstanding treatment effects include ozone oxidation, Fenton reagent method, photocatalytic oxidation method, supercritical water oxidation method and electrochemical method. Ozone oxidation The power consumption of ozone generation equipment is very high, and the utilization rate of electric energy is very low, which makes the treatment cost high. Although the Fenton reagent method can remove the target pollutants; but the removal rate of TOC is low under normal temperature and pressure; the photocatalytic method is difficult Effectively inhibit the recombination of photogenerated electrons and holes, and the photocatalytic efficiency is very low; the supercritical water oxidation method has extremely high requirements on the material of the reactor, and it is still difficult to find an ideal reactor material that can withstand long-term corrosion resistance, high temperature resistance, and high pressure resistance , and there is still a certain distance from wide application. The electrochemical method has the advantages of high treatment efficiency, low cost, simple equipment, easy operation, less land occupation, easy automation, and environmental friendliness. It has shown its unique advantages in the treatment of biodegradable wastewater and is gradually favored. In the electrochemical treatment of organic wastewater, the electrode is a key factor. Materials used as electrodes are required to have the characteristics of good electrical conductivity, high electrochemical activity, and stable physical and chemical properties. At present, the electrodes in the electrochemical method are mainly obtained by using some rare and precious metals and undergoing a series of modifications. The cost is high, the manufacturing process is complicated, and the working surface of the electrode is positively limited, so it is difficult to greatly improve the processing efficiency. The application of electrochemical methods is limited. Therefore, it is of great significance to prepare an electrode with good treatment effect, low price and wide source for the wide application of electrochemical methods. Graphite has good electrical conductivity, is widely sourced, and is cheap. It can be used as an electrode material for electrochemical treatment. However, ordinary graphite electrodes have low activity and poor treatment effect on phenol-containing wastewater, and the electrodes are unstable and easy to wear and tear. widely used

Contents of the invention

The purpose of the present invention is to study and prepare an electrode with high activity, good stability, wide range of sources and low price according to the needs of phenol-containing wastewater treatment and the problems existing in the electrochemical method, so that the electrochemical method can be more widely used. Phenol-containing wastewater can be effectively treated.

Another object of the present invention is to provide a method for preparing the above electrode.

The purpose of the present invention can be achieved through the following measures:

A graphite electrode for electrochemical treatment of phenol-containing wastewater. The electrode is prepared from graphite, epoxy resin and curing agent through the steps of mixing, molding, curing, baking, activation and rebaking. The activation described above is electrochemical activation.

A method for preparing a graphite electrode for electrochemical treatment of phenol-containing wastewater, using graphite, epoxy resin and curing agent as main raw materials, and preparing through the steps of mixing, molding, curing, baking, activation and rebaking, wherein the The activation is electrochemical activation.

Wherein the epoxy resin is 618 epoxy resin (Blue Star New Material Resin Factory), and 616, 634 or 637 can also be used, and its quality is 10-30% of graphite; the curing agent is improved amine 593 curing agent (Blue Star New Material Resin factory), other improved amine curing agents such as 590, 701, T-31 or T-33 can also be used, and its quality is 10-30% of epoxy resin; the solvent during mixing is acetone.

The curing temperature is 15-35° C. (preferably 20-30° C.), and the curing time is 8-16 hours.

The baking temperature is 130-170° C., and the baking time is 0.5-4 hours.

When the electrode is activated by electrochemical method, anhydrous sodium acetate, acetone, water and glacial acetic acid are used as the electrolyte, the electrode to be activated is fixed on the anode, placed between the cathode and the anode for electrolysis, and rinsed with acetone after electrolysis. The electrolyte solution is 0.05-0.15mol/L anhydrous sodium acetate in acetone, water and acetic acid solution, the volume ratio of acetone, water and acetic acid is 55-45:35-45:10, and the electrochemical activation voltage is 22.0-24.0V . The distance between the electrode to be activated and the cathode is 0.05-1.5 cm.

The rebaking temperature is 110-140°C, and the time is 0.5-4 hours.

The purpose of the present invention can specifically be achieved through the following measures:

(1) Mixing: high-purity graphite, epoxy resin, and curing agent are mixed. That is, first weigh the epoxy resin and curing agent, then add the solvent, stir to fully dissolve the epoxy resin, pour it into the high-purity graphite powder, and fully stir to make it evenly mixed.

(2) Compression molding: put the uniformly mixed raw materials into a mold, and press molding.

(3) Curing: The compressed graphite rod is removed from the mold, placed in the air at 20-30°C for 8-16 hours, and allowed to solidify naturally.

(4) Baking: bake the graphite rod obtained after molding and curing at 130-170°C for 0.5-4 hours.

(5) Activation: The prepared graphite rod electrode is activated by electrochemical method, and the common graphite rod is used as the anode and the cathode respectively, and the prepared graphite rod is parallel to the anode and is fastened and fixed on the anode with a cotton thread. Make the anode end level with one end of the prepared graphite rod, place the prepared graphite rod between the cathode and anode and have a distance of 0.05 to 1.5 cm (preferably 0.5 cm) from the cathode, with acetone containing 0.05 to 0.15M anhydrous sodium acetate: water : The solution of glacial acetic acid=55～45:35～45:10 (V/V/V) is the electrolyte, the glass container is the electrolyzer, the electrolysis voltage is 22.0～24.0V, and the electrolyte is heated with a water bath at a constant temperature of 25 ± 1°C. During electrolysis, the electrolysis notch is covered with polyethylene film to prevent volatilization of acetone, etc., leaving only the electrodes exposed to the outside, and the electrolysis place is 8 to 12 hours. After the electrolytic treatment, the graphite rod was rinsed axially with 60mL acetone at a rate of 0.6-0.8mL/min.

(6) Re-drying: after rinsing, place the graphite rod at 110-140°C and bake for 0.5-4 hours. At this point, the preparation of the electrode is completed.

Features of the present invention:

(1) The electrode of the present invention takes graphite powder, epoxy resin, curing agent and acetone as raw materials, has a wide range of sources, and is cheap.

(2) The electrode of the present invention is prepared through material mixing-compression molding-curing-heat treatment-activation-reheat treatment, and the unique process makes the electrode have good performance.

(3) Electrode activation of the present invention adopts electrochemical method, and electrolyte adopts anhydrous sodium acetate, acetone, water, glacial acetic acid solution, makes electrode have high activity.

(4) When the electrode of the present invention treats phenol (it can also be used for other phenols, such as phenolic compounds such as nitrophenol, chlorophenol or hydroquinone), the accumulation of intermediate products is small, the toxicity is low, and the degradation effect is good.

(5) The electrode of the present invention has high activity and good stability.

Detailed ways

Example 1 Preparation of electrodes

(1) Mixing: High-purity graphite, 618 epoxy resin, and 593 curing agent are mixed in a ratio of 100:20:5 (m/m/m). In this experiment, 20.00g of high-purity graphite, 4.00g of 618 epoxy resin, and 1.00g of 593 curing agent were actually used for electrode preparation. First weigh 20.00g of high-purity graphite powder, then weigh 4.00g of 618 epoxy resin, add 1.00g of 593 curing agent, then add 10mL of acetone, stir to fully dissolve the epoxy resin, and pour it into the high-purity graphite powder , fully stirred for 10 minutes to make it evenly mixed.

(2) Compression molding: put the uniformly mixed raw materials into a mold. In this experiment, a mold with an inner diameter of 1.7cm×9.0cm was used for compression molding at a pressure of 138.2N/cm ² .

(3) Curing: The compressed graphite rod is removed from the mold, placed in the air at room temperature for 12 hours, and allowed to solidify naturally.

(4) Baking: The graphite rod obtained after forming and curing is baked at 150° C. for 2 hours.

(5) Activation: The prepared graphite rod electrode is activated by electrochemical method, and the common graphite rod is used as the anode and the cathode respectively, and the prepared graphite rod is parallel to the anode and is fastened and fixed on the anode with a cotton thread. Make the anode end level with one end of the prepared graphite rod, place the prepared graphite rod between the cathode and the anode with a distance of 0.5 cm from the cathode, and use acetone containing 0.1M anhydrous sodium acetate: water: glacial acetic acid=50:40:10 (V/V/V) solution 250mL is the electrolyte, the glass container with a diameter of 6.8cm and a height of 9.7cm is used as the electrolytic cell, the electrolysis voltage is 23.0V, and the electrolyte is heated with a water bath at a constant temperature of 25±1°C. During electrolysis, the electrolysis notch is covered with a polyethylene film to prevent volatilization of acetone, etc., leaving only the electrodes exposed, and the electrolysis treatment lasts for 10 hours. After the electrolytic treatment, the graphite rod was rinsed axially with 60mL acetone at a rate of 0.6-0.8mL/min.

(6) Re-baking: After the rinsing, the graphite rod was baked at 125° C. for 2 hours. At this point, the preparation of the electrode was completed.

Example 2 Preparation of electrodes

(1) Mixing: High-purity graphite, 616 epoxy resin, and 701 curing agent are mixed in a ratio of 100:30:7.5 (m/m/m). In this experiment, 20.00g of high-purity graphite, 6.00g of 616 epoxy resin, and 1.50g of 701 curing agent were actually used for electrode preparation. First weigh 20.00g of high-purity graphite powder, then weigh 6.00g of 616 epoxy resin, add 1.50g of 701 curing agent, then add 10mL of acetone, stir to fully dissolve the epoxy resin, and pour it into the high-purity graphite powder , fully stirred for 10 minutes to make it evenly mixed.

(2) Compression molding: put the uniformly mixed raw materials into a mold. In this experiment, a mold with an inner diameter of 1.7cm×9.0cm was used for compression molding at a pressure of 138.2N/cm ² .

(3) Curing: The compressed graphite rod is removed from the mold, placed in the air at room temperature for 13 hours, and allowed to solidify naturally.

(4) Baking: The graphite rod obtained after molding and curing is baked at 130° C. for 3 hours.

(5) Activation: The prepared graphite rod electrode is activated by electrochemical method, and the common graphite rod is used as the anode and the cathode respectively, and the prepared graphite rod is parallel to the anode and is fastened and fixed on the anode with a cotton thread. Make the anode end level with one end of the prepared graphite rod, place the prepared graphite rod between the cathode and the anode with a distance of 0.5 cm from the cathode, and use acetone containing 0.1M anhydrous sodium acetate: water: glacial acetic acid=45:45:10 (V/V/V) solution 250mL is the electrolyte, the glass container with a diameter of 6.8cm and a height of 9.7cm is used as the electrolytic cell, the electrolysis voltage is 23.0V, and the electrolyte is heated with a water bath at a constant temperature of 25±1°C. During electrolysis, the electrolysis notch is covered with a polyethylene film to prevent volatilization of acetone, etc., leaving only the electrodes exposed, and the electrolysis treatment lasts for 10 hours. After the electrolytic treatment, the graphite rod was rinsed axially with 60mL acetone at a rate of 0.6-0.8mL/min.

(6) Re-baking: After the rinsing, the graphite rod was baked at 115°C for 3 hours, and the electrode preparation was completed at this point.

The graphite electrode prepared by the present invention is used together with the common graphite electrode for the electrolytic treatment of phenol-containing aqueous solution, and the performance of the electrode and its effect on phenol removal are compared. The electrode morphology, the removal rate of phenol, the change of intermediate products and the content of benzoquinone were used as the standard.

In the experiment, the new graphite electrode of Example 1 and the ordinary graphite electrode were used as the anode, stainless steel 304 as the cathode, and 200mg/L phenol containing 0.1M anhydrous sodium sulfate 200mL as the electrolyte, the current density was 18.9mA/ ^cm2 , and the electrolysis area It is 20.65cm ² , the distance between cathode and anode is 1.0cm, the water bath is heated at a constant temperature of 25±1°C, and magnetic stirring is used during the experiment.

Experiment 1: The removal effect of two kinds of electrode electrolysis on phenol

Under the above electrolysis experimental conditions, the phenol removal rate of the ordinary graphite electrode is 88.2%, which is higher than that of the new graphite electrode prepared by 61.3%.

Experiment 2: Changes of intermediate products in the electrolysis of phenol solution with two electrodes

Phenol and its degradation intermediate aromatic products have absorption in the ultraviolet (UV) region. Studying the UV spectrum of the degradation products can help us understand the morphological changes of the phenol degradation products. The UV scanning research was carried out on the degradation products of ordinary graphite electrodes and the prepared new graphite electrodes. Ordinary graphite electrodes have weak oxidation performance for phenol, and the degradation is not ideal, with a large amount of intermediate products accumulated and maintained at a high concentration; while new graphite electrodes have less accumulation of intermediate products and good degradation effect.

Experiment 3: The change of benzoquinone in the electrolysis of phenol solution with two electrodes

Benzoquinone is an intermediate product of phenol degradation, and is more toxic and refractory than phenol. During the electrolysis process, the ordinary graphite electrode degrades and accumulates a large amount of benzoquinone, and it is difficult to further degrade. 4.8mg/L.

Experiment 4: Adsorption effect of graphite on phenol and benzoquinone

At 25°C and neutral pH conditions, graphite has almost no adsorption effect on phenol, and the adsorption effect on p-benzoquinone is also very weak. This confirms that in the experiment of electrochemical degradation of phenol, the disappearance of phenol and its intermediate products is due to the electrochemical degradation of the graphite electrode, and also confirms the electrochemical activity of the new graphite electrode and its ability to degrade phenol.

Experiment 5: Comparison of Stability of Two Electrodes

During the electrolysis process, the ordinary graphite electrode loosens and falls off within 1 hour of electrolysis, and is easy to be worn out. After the electrolysis, there are a large number of graphite particles in the electrolyte, but the new graphite electrode prepared has no loosening and falling off phenomenon, and the electrode is stable without obvious changes. It shows that the new graphite electrode is stable and more suitable for the electrochemical treatment of phenolic wastewater.

Claims (5)

1. Graphite Electrodes that is used for the phenolic wastewater electrochemical treatment, it is characterized in that this electrode is a main raw material with graphite, Resins, epoxy and solidifying agent, through mixing, moulding, curing, baking, activation with dry by the fire step preparation again and get, wherein said activation is an electrochemical activation;

When activating, make electrolytic solution, need be fixed on the anode by activated electrode, place and carry out electrolysis between anode and cathode, use acetone drip washing after the electrolysis with sodium acetate, anhydrous, acetone, water and Glacial acetic acid with the electrochemical process counter electrode; Described electrolytic solution is acetone, water and the acetum of 0.05～0.15mol/L sodium acetate, anhydrous, wherein the volume ratio of acetone, water and acetic acid is 55～45: 35～45: 10, electrochemical activation voltage is 22.0～24.0V, and electrode to be activated and cathode distance are 0.05～1.5cm;

Wherein the quality of Resins, epoxy is 10～30% of a graphite, and the quality of solidifying agent is 10～30% of a Resins, epoxy;

The solidified temperature is 15～35 ℃, and the time is 8～16h;

The temperature of baking is 130～170 ℃, and the time is 0.5～4h;

The temperature of multiple baking is 110～140 ℃, and the time is 0.5～4h.

2. Graphite Electrodes according to claim 1 is characterized in that described Resins, epoxy is 618 Resins, epoxy, 616 Resins, epoxy, 634 Resins, epoxy or 637 Resins, epoxy, and its quality is 10～30% of a graphite.

3. Graphite Electrodes according to claim 1 is characterized in that described solidifying agent is 593 solidifying agent, 590 solidifying agent, 701 solidifying agent, T-31 solidifying agent or T-33 solidifying agent.

4. Graphite Electrodes according to claim 1, the solvent when it is characterized in that mixing are acetone.

5. method for preparing the Graphite Electrodes that is used for the phenolic wastewater electrochemical treatment, it is characterized in that with graphite, Resins, epoxy and solidifying agent be main raw material, pass through mixing, moulding, curing, baking, activation and dry by the fire the step preparation again, wherein said activation is an electrochemical activation;

When activating, make electrolytic solution, need be fixed on the anode by activated electrode, place and carry out electrolysis between anode and cathode, use acetone drip washing after the electrolysis with sodium acetate, anhydrous, acetone, water and Glacial acetic acid with the electrochemical process counter electrode; Described electrolytic solution is acetone, water and the acetum of 0.05～0.15mol/L sodium acetate, anhydrous, wherein the volume ratio of acetone, water and acetic acid is 55～45: 35～45: 10, electrochemical activation voltage is 22.0～24.0V, and electrode to be activated and cathode distance are 0.05～1.5cm;

Wherein the quality of Resins, epoxy is 10～30% of a graphite, and the quality of solidifying agent is 10～30% of a Resins, epoxy;

The solidified temperature is 15～35 ℃, and the time is 8～16h;

The temperature of baking is 130～170 ℃, and the time is 0.5～4h;

The temperature of multiple baking is 110～140 ℃, and the time is 0.5～4h.