Electrochemical treatment method and application of high-salt-content coal chemical wastewater

Abstract

The invention belongs to the technical field of wastewater treatment, and discloses an electrochemical treatment method and application of high-salt-content coal chemical wastewater, the electrochemical treatment method comprises the following steps: (1) injecting the high-salt-content coal chemical wastewater into an electrochemical reactor, taking a soluble metal electrode as an anode and a dimensionally stable electrode as a cathode to carry out an electric flocculation reaction, meanwhile, fluorine ions in the wastewater are removed in cooperation with the adsorption effect of a particle electrode; (2) after the wastewater is treated in the step (1), electrode reversal is performed on an electrode in an electrochemical reactor, an electrooxidation reaction is performed by taking a dimensionally stable electrode as an anode and a soluble metal electrode as a cathode, and meanwhile, the adsorption and electrooxidation degradation effects of a particle electrode are matched, so that refractory organic matters in the wastewater are removed; and (3) feeding the wastewater treated in the step (2) into a filtering device, filtering, and discharging. The method disclosed by the invention is simple and convenient in operation steps, small in occupied area and suitable for treating the refractory organic matters in the high-salt-content coal chemical wastewater.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and more specifically, to an electrochemical treatment method and application of high-salt coal chemical wastewater. Background Art

[0002] High-salinity wastewater from coal chemical industry mainly comes from drainage of chemical water station, drainage of circulating water system and gasification wastewater formed in coal gasification process. The main pollutants are total dissolved solids (TDS) and refractory organic matter. The mass concentration of TDS is 10000-100000 mg / L, even up to 200000 mg / L or more, and the mass concentration of COD is 100-5000 mg / L. COD has complex composition and high concentration, which may cause membrane pollution and bring difficulties to subsequent evaporation and crystallization, such as severe foaming, poor quality of crystallized salt, and inability to reuse, which limits the further concentration or resource utilization of wastewater. Before membrane treatment and subsequent evaporation and crystallization, organic matter in high-salinity wastewater must be removed. However, the current common water treatment technologies, such as activated carbon adsorption and biological methods, have high operating costs and cannot achieve the expected treatment effect for the treatment of high-salinity wastewater. Electrocatalytic oxidation has a good removal effect on organic matter in wastewater, and the treatment process only consumes electricity and no reagents, which is an ideal treatment method.

[0003] Coal chemical wastewater has complex composition and high COD concentration, among which the fluoride ion concentration of gasification wastewater is relatively high. Fluoride ions have a corrosive effect on the anode in electrocatalytic oxidation, seriously affecting the service life of the anode. Therefore, it is necessary to reduce the fluoride ion content in the water to meet the water inlet requirements of electrochemical oxidation treatment. Among the current water defluorination process technologies, adsorption and coagulation precipitation methods are widely studied and applied, among which coagulation precipitation is one of the most widely used process technologies for treating fluoride-containing wastewater. Moreover, the current wastewater defluorination technology is mainly used to treat medium and high concentration fluoride-containing wastewater. It is relatively easy to achieve a fluoride concentration of ≤15mg / L after treatment. When continuing to treat to a lower concentration, the dosage increases and the difficulty increases. Therefore, it is necessary to develop a new technology for the electrochemical treatment of difficult-to-degrade organic matter in high-salt coal chemical wastewater. Summary of the invention

[0004] The purpose of the present invention is to provide an electrochemical treatment method for high-salt coal chemical wastewater and its application. The high-salt coal chemical wastewater has high fluoride ion content and high sulfate content. The high sulfate content will affect the removal of fluoride ions. The treatment method of the present invention first removes most of the fluoride ions through an electric flocculation reaction and the adsorption effect of a particle electrode, so that the fluoride ion concentration reaches the electrochemical oxidation water inlet requirement, and then treats the difficult-to-degrade organic matter in the wastewater by performing an electric oxidation reaction through electrode reversal and coordinating the adsorption and electric oxidation degradation effects of the particle electrode. The method of the present invention has simple operation steps and occupies a small area, and is suitable for treating difficult-to-degrade organic matter in high-salt coal chemical wastewater.

[0005] In order to achieve the above object, one aspect of the present invention provides an electrochemical treatment method for high-salt coal chemical wastewater, the electrochemical treatment method comprising:

[0006] (1) injecting the high-salt coal chemical wastewater into an electrochemical reactor, using a soluble metal electrode as an anode and a shape-stable electrode as a cathode to perform an electric flocculation reaction, and simultaneously cooperating with the adsorption effect of the particle electrode to remove fluoride ions in the wastewater;

[0007] (2) After the treatment in step (1), the electrodes are reversed in the electrochemical reactor, and an electro-oxidation reaction is performed with the shape-stable electrode as the anode and the soluble metal electrode as the cathode, and the adsorption and electro-oxidation degradation effects of the particle electrode are combined to remove the difficult-to-degrade organic matter in the wastewater;

[0008] (3) The wastewater treated in step (2) is passed into a filtering device and discharged after being filtered.

[0009] Another aspect of the present invention provides application of the electrochemical treatment method in treating high-salt coal chemical wastewater.

[0010] The technical solution of the present invention has the following beneficial effects:

[0011] In the present invention, the electrocoagulation and electrochemical oxidation are arranged in the same electrochemical reactor, and the cathode and anode conversion of the electrode plate is realized by converting the positive and negative electrodes of the power supply. When the soluble metal electrode is used as the anode, the electrocoagulation occurs to remove the fluoride ions in the water, and the particle electrode also has an adsorption effect on the fluoride ions. After the fluoride ion concentration reaches the electrochemical oxidation water inlet requirement, the shape-stable electrode is used as the anode to treat the difficult-to-degrade organic matter in the wastewater. On the one hand, the particle electrode plays the role of adsorbing the difficult-to-degrade organic matter, and on the other hand, it effectively utilizes the electrolysis space and plays the role of strengthening the electric field, so that the organic matter in the wastewater can be oxidized and degraded. The reversal treatment of the two electrodes can prevent the occurrence of electrode passivation and also play a role in regenerating the particle electrode.

[0012] The equipment of the present invention has simple process, easy operation, low energy consumption, no need to add reagents during the treatment process, low sludge production, no secondary pollution, and can achieve green and efficient treatment of difficult-to-degrade organic matter in high-salt coal chemical wastewater.

[0013] Other features and advantages of the present invention will be described in detail in the following detailed description. DETAILED DESCRIPTION

[0014] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0015] One aspect of the present invention provides an electrochemical treatment method for high-salt coal chemical wastewater, the electrochemical treatment method comprising:

[0016] (1) injecting the high-salt coal chemical wastewater into an electrochemical reactor, using a soluble metal electrode as an anode and a shape-stable electrode as a cathode to perform an electric flocculation reaction, and simultaneously cooperating with the adsorption effect of the particle electrode to remove fluoride ions in the wastewater;

[0017] (2) After the treatment in step (1), the electrodes are reversed in the electrochemical reactor, and an electro-oxidation reaction is performed with the shape-stable electrode as the anode and the soluble metal electrode as the cathode, and the adsorption and electro-oxidation degradation effects of the particle electrode are combined to remove the difficult-to-degrade organic matter in the wastewater;

[0018] (3) The wastewater treated in step (2) is passed into a filtering device and discharged after being filtered.

[0019] In the present invention, electrochemical flocculation and electrochemical oxidation treatment are carried out in the same electrochemical reactor, the operation steps are simple and the occupied area is small.

[0020] In the present invention, the polarity reversal is achieved by switching the positive and negative poles of the power supply, that is, the positive and negative poles of the electrode plate are switched. The switching of the positive and negative poles of the power supply can be achieved manually, or the automatic switching of the positive and negative poles of the power supply can be set.

[0021] According to the present invention, preferably, when the fluoride ion concentration in the wastewater treated in step (1) reaches the electrochemical oxidation water inlet requirement, the electrode reversal is performed; further preferably, when the fluoride ion concentration in the wastewater treated in step (1) is below 5 mg / L, the electrode reversal is performed.

[0022] According to the present invention, preferably, the soluble metal electrode is an aluminum electrode, an iron electrode or an aluminum-iron alloy electrode;

[0023] The shape-stable electrode is a titanium-based metal-coated oxide electrode or a boron-doped diamond film electrode; the metal-coated oxide is preferably one or more oxides of ruthenium, iridium, titanium, rhodium, tin, antimony, platinum and lead;

[0024] The particle electrode is activated alumina and / or activated carbon.

[0025] According to the present invention, preferably, the anode and cathode in the electrochemical reactor are one or more groups;

[0026] When the anode and cathode are a group, the particle electrode is arranged between the plates of the anode and cathode;

[0027] When there are multiple groups of anodes and cathodes, the anodes and cathodes are arranged crosswise; and the particle electrode is arranged between two adjacent electrode plates.

[0028] According to the present invention, preferably, the distance between the anode and cathode plates is 3.0-10.0 cm.

[0029] In the present invention, preferably, when the anode and cathode are in multiple groups, the distance between two adjacent electrode plates is 3.0-10.0 cm.

[0030] According to the present invention, preferably, the dosage of the particle electrode is 20-40 g / L.

[0031] In the present invention, the dosage of the particle electrode is 20-40 g / L, which means that relative to 1 L of high-salt coal chemical wastewater, the dosage of the particle electrode is 20-40 g.

[0032] According to the present invention, preferably, the current density of the electrochemical reactor is 25-50 mA / cm 2 .

[0033] According to the present invention, preferably, the time of the electro-flocculation reaction and the electrochemical oxidation reaction are independently 10-40 minutes.

[0034] In the present invention, the time of the electro-flocculation reaction and the electrochemical oxidation reaction is adjusted according to the fluoride ion content and the organic matter content in the wastewater.

[0035] According to the present invention, preferably, the fluorine content in the high-salt coal chemical wastewater is 60-180 mg / L.

[0036] Another aspect of the present invention provides application of the electrochemical treatment method in treating high-salt coal chemical wastewater.

[0037] The present invention will be described in detail below through examples.

[0038] The water quality of high-salinity coal chemical wastewater is shown in Table 1.

[0039] Table 1

[0040] Wastewater <![CDATA[Ca 2+ ]]> Total Alkalinity <![CDATA[Cl - ]]> <![CDATA[SO4 2- ]]> pH Conductivity <![CDATA[F - ]]> COD 1 26.1 954 4473.7 17702.8 8.3 38.55 94.9 120 2 8.9 1180.4 3140.1 13791.1 9.0 35.96 154 105

[0041] Note: pH has no unit, conductivity unit is ms / cm, other units are mg / L, Ca 2+ , total alkalinity are all calculated as CaCO3, the same below. 2+ Represents calcium hardness, the same below. The determination methods of each parameter are as follows: Ca 2+ : Reference standard GB / T 6910-2006; Total alkalinity: Reference standard GB / T 15451-2006; Cl - : Reference standard GB / T 15453-2008; SO4 2- : Reference standard GB / T14642-2009; pH value: Reference standard GB / T 6920-1986; Conductivity: Reference standard GB / T 6908-2008; F - : Reference standard GB / T 7484-1987; COD: Reference standard GB 11914-89.

[0042] In the following embodiments, the electrochemical reactor used is provided with a cathode plate, an anode plate and a particle electrode, and the particle electrode is arranged between the cathode plate and the anode plate.

[0043] In the following embodiments, F - The concentration of is tested according to the standard GB / T 7484-1987; the concentration of COD is tested according to the standard GB 11914-89.

[0044] Example 1

[0045] It is used for electrochemical treatment of refractory organic matter in high-salinity coal chemical wastewater. The method is as follows: 1L of high-salinity coal chemical wastewater 1 is injected into the electrochemical reactor, and an aluminum electrode is used as the anode and a titanium-based ruthenium iridium titanium oxide coating electrode is used as the cathode for electrocoagulation reaction. At the same time, the adsorption effect of the activated carbon particle electrode is combined to remove fluoride ions in the wastewater. The addition amount of the particle electrode is 20g / L, the distance between the anode and cathode plates is 3cm, and the plate area of ​​the anode and cathode is 100cm 2 , current density is 25mA / cm 2, the reaction time is 10min, at this time, the fluoride ion concentration in the wastewater is below 5mg / L; then, the electrodes are reversed, and the titanium-based ruthenium iridium titanium oxide coated electrode is used as the anode and the aluminum electrode is used as the cathode for electro-oxidation reaction, the reaction time is 30min, and at the same time, the activated carbon particle electrode is used for adsorption and electro-oxidation degradation of organic matter to remove the difficult-to-degrade organic matter in the wastewater; finally, the treated wastewater enters the filtration device and is discharged after filtration. The fluoride ion and COD results of the effluent are listed in Table 2.

[0046] Example 2

[0047] It is used for the electrochemical treatment of refractory organic matter in high-salinity coal chemical wastewater. The method is as follows: 1L of high-salinity coal chemical wastewater 1 is injected into the electrochemical reactor, and the iron electrode is used as the anode and the titanium-based lead dioxide electrode is used as the cathode for electrocoagulation reaction. At the same time, the adsorption effect of the activated alumina particle electrode is used to remove the fluoride ions in the wastewater. The addition amount of the particle electrode is 25g / L, the distance between the anode and cathode plates is 5cm, and the plate area of ​​the anode and cathode is 100cm 2 , current density is 30mA / cm 2 , the reaction time is 20min, at this time, the fluoride ion concentration in the wastewater is below 5mg / L; then, the electrodes are reversed, and the titanium-based lead dioxide electrode is used as the anode and the iron electrode is used as the cathode for electro-oxidation reaction, the reaction time is 20min, and at the same time, the activated carbon particle electrode is used for adsorption and electro-oxidation degradation of organic matter to remove the difficult-to-degrade organic matter in the wastewater; finally, the treated wastewater enters the filtration device and is discharged after filtration. The fluoride ion and COD results of the effluent are listed in Table 2.

[0048] Example 3

[0049] It is used for electrochemical treatment of refractory organic matter in high-salinity coal chemical wastewater. The method is as follows: 1L high-salinity coal chemical wastewater 1 is injected into the electrochemical reactor, and the aluminum-iron alloy electrode is used as the anode and the titanium-based tin antimony oxide coating electrode is used as the cathode for electrocoagulation reaction. At the same time, the adsorption effect of the activated carbon particle electrode is combined to remove the fluoride ions in the wastewater. The addition amount of the particle electrode is 30g / L, the distance between the anode and cathode plates is 8cm, and the plate area of ​​the anode and cathode is 100cm 2 , current density is 35mA / cm 2 , the reaction time is 30min, at this time, the fluoride ion concentration in the wastewater is below 5mg / L; then, the electrodes are reversed, with the titanium-based tin antimony oxide coated electrode as the anode and the aluminum-iron alloy electrode as the cathode for electro-oxidation reaction, the reaction time is 10min, and at the same time, the activated carbon particle electrode is used for adsorption and electro-oxidation degradation of organic matter to remove the difficult-to-degrade organic matter in the wastewater; finally, the treated wastewater enters the filtration device and is discharged after filtration. The fluoride ion and COD results of the effluent are listed in Table 2.

[0050] Example 4

[0051] It is used for electrochemical treatment of refractory organic matter in high-salinity coal chemical wastewater. The method is as follows: 1L high-salinity coal chemical wastewater 2 is injected into the electrochemical reactor, and an aluminum electrode is used as the anode and a titanium-based ruthenium iridium oxide coating electrode is used as the cathode for electrocoagulation reaction. At the same time, the adsorption effect of the activated alumina particle electrode is combined to remove fluoride ions in the wastewater. The addition amount of the particle electrode is 35g / L, the distance between the anode and cathode plates is 10cm, and the plate area of ​​the anode and cathode is 100cm 2 , current density is 40mA / cm 2 , the reaction time is 20min, at this time, the fluoride ion concentration in the wastewater is below 5mg / L; then, the electrodes are reversed, and the titanium-based ruthenium-iridium oxide coated electrode is used as the anode and the aluminum electrode is used as the cathode for electro-oxidation reaction, the reaction time is 20min, and at the same time, the activated carbon particle electrode is used for adsorption and electro-oxidation degradation of organic matter to remove the difficult-to-degrade organic matter in the wastewater; finally, the treated wastewater enters the filtration device and is discharged after filtration. The fluoride ion and COD results of the effluent are listed in Table 2.

[0052] Example 5

[0053] It is used for electrochemical treatment of refractory organic matter in high-salinity coal chemical wastewater. The method is as follows: 1L high-salinity coal chemical wastewater 2 is injected into the electrochemical reactor, and the aluminum-iron alloy electrode is used as the anode and the titanium-based lead dioxide electrode is used as the cathode for electrocoagulation reaction. At the same time, the adsorption effect of the activated alumina particle electrode is combined to remove fluoride ions in the wastewater. The addition amount of the particle electrode is 40g / L, the distance between the anode and cathode plates is 6cm, and the plate area of ​​the anode and cathode is 100cm 2 , current density is 50mA / cm 2 , the reaction time is 15min, at this time, the fluoride ion concentration in the wastewater is below 5mg / L; then, the electrodes are reversed, and the titanium-based lead dioxide electrode is used as the anode and the aluminum-iron alloy electrode is used as the cathode for electro-oxidation reaction, the reaction time is 15min, and at the same time, the activated carbon particle electrode is used for adsorption and electro-oxidation degradation of organic matter to remove the difficult-to-degrade organic matter in the wastewater; finally, the treated wastewater enters the filtration device and is discharged after filtration. The fluoride ion and COD results of the effluent are listed in Table 2.

[0054] Table 2

[0055] Example <![CDATA[Effluent F - , mg / L]]> Outlet COD, mg / L Example 1 3.8 24.0 Example 2 3.1 23.5 Example 3 2.9 23.8 Example 4 3.3 26.9 Example 5 3.5 25.1

[0056] The Beijing Municipal Integrated Wastewater Discharge Standard stipulates that the COD discharge limit for discharge into surface water bodies is 30 mg / L. From the results in Table 2, it can be seen that the electrochemical treatment of high-salt coal chemical wastewater according to the method of the present invention can treat the organic matter in the wastewater to below 30 mg / L, meeting the Beijing Municipal Integrated Wastewater Discharge Standard.

[0057] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. An electrochemical treatment method for high-salt coal chemical wastewater, It is characterized in that The electrochemical treatment method comprises: (1) injecting the high-salt coal chemical wastewater into an electrochemical reactor, using a soluble metal electrode as an anode and a shape-stable electrode as a cathode to perform an electric flocculation reaction, and simultaneously cooperating with the adsorption effect of the particle electrode to remove fluoride ions in the wastewater; (2) After the treatment in step (1), the electrodes are reversed in the electrochemical reactor, and an electro-oxidation reaction is performed with the shape-stable electrode as the anode and the soluble metal electrode as the cathode, and the adsorption and electro-oxidation degradation effects of the particle electrode are combined to remove the difficult-to-degrade organic matter in the wastewater; (3) The wastewater treated in step (2) is passed into a filtering device and discharged after being filtered.

2. The electrochemical treatment method according to claim 1, in, When the fluoride ion concentration in the wastewater treated in step (1) reaches the electrochemical oxidation water inlet requirement, the electrode is reversed; preferably, when the fluoride ion concentration in the wastewater treated in step (1) is below 5 mg / L, the electrode is reversed.

3. The electrochemical treatment method according to claim 1, in, The soluble metal electrode is an aluminum electrode, an iron electrode or an aluminum-iron alloy electrode; The shape-stable electrode is a titanium-based metal-coated oxide electrode or a boron-doped diamond film electrode; the metal-coated oxide is preferably one or more oxides of ruthenium, iridium, titanium, rhodium, tin, antimony, platinum and lead; The particle electrode is activated alumina and / or activated carbon.

4. The electrochemical treatment method according to claim 1, in, The anode and cathode in the electrochemical reactor are one or more groups; When the anode and cathode are a group, the particle electrode is arranged between the plates of the anode and cathode; When there are multiple groups of anodes and cathodes, the anodes and cathodes are arranged crosswise; and the particle electrode is arranged between two adjacent electrode plates.

5. The electrochemical treatment method according to claim 1, in, The distance between the anode and cathode plates is 3.0-10.0 cm.

6. The electrochemical treatment method according to claim 1, in, The dosage of the particle electrode is 20-40 g / L.

7. The electrochemical treatment method according to claim 1, in, The current density of the electrochemical reactor is 25-50 mA / cm 2 .

8. The electrochemical treatment method according to claim 1, in, The time of the electrocoagulation reaction and the electrochemical oxidation reaction are independently 10-40 minutes.

9. The electrochemical treatment method according to claim 1, in, The fluorine content in the high-salt coal chemical wastewater is 60-180 mg / L.

10. Application of the electrochemical treatment method according to any one of claims 1 to 9 in treating high-salt coal chemical wastewater.