A device and method for coupling pyrite to electrochemically activate monopersulfate

Abstract

The application discloses a device and method for coupling pyrite and electrochemically activated monopersulfate, which comprises the following steps: pretreatment of pyrite, construction of an electrochemically activated monopersulfate system, and coupling of pyrite and the electrochemically activated monopersulfate system. The application couples pyrite and the electrochemically activated monopersulfate system, and divalent iron is released into an electrolyte by the reaction of pyrite and monopersulfate, the divalent iron can activate monopersulfate and can be regenerated by cathode reduction to continuously activate monopersulfate; after the pyrite is coupled with electricity, abundant reactive species are generated in the system, and new pollutants can be effectively degraded. The method is simple to operate, raw materials are widely available, easy to obtain and cheap, and is easy to popularize and apply.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of environmental organic pollutant treatment, and relates to activation of monopersulfate, in particular to a device and method for activating monopersulfate by coupling pyrite with electrochemistry. BACKGROUND

[0002] In recent years, emerging contaminants (ECs) have been frequently detected in environmental water bodies, and thus have attracted extensive attention. Unlike conventional organic pollutants, ECs have low concentrations in environmental water bodies, generally at the mg / L or ng / L level, but are generally persistent, non-degradable, high-risk and potentially toxic, which brings great hidden dangers to human health and ecological safety.

[0003] The conventional treatment process in urban water plants and sewage plants is not ideal for the treatment of emerging contaminants. Electrochemical activation of monopersulfate is a new emerging monopersulfate activation method, which can utilize the rich reactive species in the system to degrade organic pollutants, and is a potential emerging contaminant removal technology.

[0004] The currently reported electrochemical activation of persulfate systems only considers the activation of persulfate by electrodes, and ignores the possibility of adding reagents to strengthen the activation of persulfate in electrolyte. For example, in the method for degrading organic pollutants in water by electrochemical cathode activation of persulfate disclosed in CN103342405A, the persulfate is activated by applying a voltage to a metal or metal oxide cathode to degrade organic pollutants, but the above method only utilizes the metal or metal oxide cathode, and the activation efficiency of persulfate is low.

[0005] For example, in the method for treating organic wastewater by electrochemical activation of persulfate disclosed in CN102249378B, iron sheets are used as anode and cathode, and Fe 2+ Catalyst and reduction reaction of persulfate at the cathode to co-activate persulfate, the above method utilizes both anode and cathode, but the catalytic activity of iron electrode is not high, and using iron sheet as anode will cause rapid wear of iron electrode, which requires frequent replacement of anode.

[0006] The existing electrochemical activation of persulfate method mainly relies on electrodes, but is limited by the catalytic activity, effective area and mass transfer efficiency of monopersulfate of the electrode, and there is still a great space for improvement in efficiency. SUMMARY

[0007] The present application aims at the problem of poor efficiency of existing electrochemical activation of persulfate, and provides a device and method for pyrite coupled electrochemical activation of monopersulfate.

[0008] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0009] The present application first provides a device for pyrite coupled electrochemical activation of monopersulfate, which comprises a power supply, an electrolytic cell, a constant-temperature water tank, a titanium-based iridium tantalum anode connected to the positive pole of the power supply, and a titanium-based iridium tantalum cathode connected to the negative pole of the power supply, wherein the titanium-based iridium tantalum anode and the titanium-based iridium tantalum cathode are suspended in the electrolytic cell, the electrolytic cell is arranged in the constant-temperature water tank, and the electrolyte is added with pretreated pyrite.

[0010] As a preferred scheme of the present application, the power supply is a direct current power supply, and the electrolytic cell is further provided with a stirring device.

[0011] The present application further provides a method for pyrite coupled electrochemical activation of monopersulfate, which activates monopersulfate by using the above-mentioned device, and comprises pretreatment of pyrite, construction of an electrochemical activation monopersulfate system, and coupling of pyrite and the electrochemical activation monopersulfate system.

[0012] As a preferred scheme of the present application, the method comprises the following steps:

[0013] 1) Pretreatment of pyrite: crushing natural pyrite into particles, soaking the obtained pyrite particles in an acid solution, washing with pure water, vacuum drying, grinding into powder, sieving, and obtaining pyrite powder with uniform particles;

[0014] 2) Construction of an electrochemical activation monopersulfate system: using a titanium-based iridium tantalum electrode as an anode and a cathode, preparing an electrolyte, controlling the temperature in the constant-temperature water tank, and supplying power at 80 mA and a current density of 5 mA / cm 2 ;

[0015] 3) Coupling of pyrite and the electrochemical activation monopersulfate system: adding the pyrite powder obtained in step 1) to the electrolyte in step 2), stirring uniformly, turning on the power supply, and starting activation.

[0016] As a preferred scheme of the present application, in step 1), the acid solution is a dilute hydrochloric acid solution with a concentration of 1M.

[0017] As a preferred scheme of the present application, in step 1), the natural pyrite is crushed into particles with a particle size less than 1 cm, and the mesh number of the screening is 300 meshes.

[0018] As a preferred scheme of the present application, in step 2), the electrolyte is an aqueous solution containing a monopersulfate salt with a concentration of 1 mM and sodium perchlorate with a concentration of 5 mM.

[0019] As a preferred scheme of the present application, in step 2), the temperature of the constant-temperature water tank is 25℃, the rotating speed of the stirring device is 300 r / min, and the power-on duration is 30 min.

[0020] As a preferred scheme of the present application, in step 3), the concentration of the pyrite powder is 100 mg / L.

[0021] As a preferred scheme of the present application, the monopersulfate salt is a monopersulfate salt potassium hydrogen compound salt with KHSO5≥47%.

[0022] Compared with the prior art, the present application has the following beneficial effects:

[0023] 1) The device of the present application is simple and easy to obtain and set up.

[0024] 2) The present application couples the pyrite with the electrochemically activated monopersulfate salt system, the reaction of the pyrite with the monopersulfate salt releases divalent iron into the electrolyte, the divalent iron can activate the monopersulfate salt and can be regenerated by reduction at the cathode to continuously activate the monopersulfate salt; after the pyrite is coupled with electrochemistry, abundant reactive species are generated in the system, which can effectively degrade new pollutants.

[0025] 3) The method of the present application is simple to operate, the raw materials are widely available, easy to obtain and cheap, and easy to popularize and apply. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a schematic diagram of the present application.

[0027] Figure 2 is the degradation of new pollutants before and after the pyrite is coupled with electrochemistry.

[0028] Figure 3 is the release of iron in the pyrite-electrochemical coupling system.

[0029] Figure 4 is the reactive species in the pyrite-electrochemical coupling system.

[0030] Figure 5 is the degradation of sulfonamides by the coupling system when the pyrite is reused.

[0031] In the figure, 1. natural pyrite; 2. pyrite powder; 3. titanium-based iridium tantalum anode; 4. titanium-based iridium tantalum cathode; 5. electrolyte; 6. direct current power supply; 7. magnetic stirrer; 8. constant temperature water tank; 9. electrolytic cell. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0033] Reference Figure 1 The present application first provides a device for activating persulfate by pyrite coupling electrochemistry, which comprises a direct current power supply 6, an electrolytic cell 9, a constant temperature water tank 8, a titanium-based iridium tantalum anode 3 connected to the positive electrode of the direct current power supply 6, and a titanium-based iridium tantalum cathode 4 connected to the negative electrode of the direct current power supply 6, wherein the titanium-based iridium tantalum anode 3 and the titanium-based iridium tantalum cathode 4 are suspended in the electrolytic cell 9, the electrolytic cell 9 is arranged in the constant temperature water tank 8, and the bottom of the electrolytic cell 9 is further provided with a magnetic stirrer 7.

[0034] The present application further provides a method for activating persulfate by pyrite coupling electrochemistry, which comprises pretreatment of natural pyrite 1, construction of an electrochemically activated persulfate system, and coupling of pyrite and the electrochemically activated persulfate system.

[0035] The natural pyrite 1 is first crushed into particles with a particle size of less than 1 cm by a crusher; the obtained pyrite particles are soaked in dilute hydrochloric acid with a concentration of 1M for 15 min to remove impurities and iron oxides on the surface of the particles, and then washed with pure water until the pH remains unchanged; the obtained pyrite is vacuum dried for 8 h, and then ground into powder by a ball mill; and the obtained pyrite powder is sieved by a 300-mesh sieve to obtain pyrite powder 2 with uniform particles.

[0036] Then, a titanium-based iridium tantalum electrode with a size of 2 cm x 4 cm is used as a cathode and an anode respectively, an aqueous solution containing 1 mM of persulfate and 5 mM of sodium perchlorate is used as an electrolyte, the pyrite powder with a concentration of 100 mg / L is uniformly dispersed into the electrolyte by stirring, the constant temperature water tank is used to control the reaction temperature to be 25°C, the magnetic stirrer with a rotation speed of 300 r / min is used to stir the solution, and the stabilized direct current power supply is used to provide 80 mA direct current, so that the current density is 5 mA / cm 2 , and the power-on duration is 30 min.

[0037] Example 1

[0038] The embodiment provides a comparison of degradation of new pollutants before and after pyrite and electrochemical coupling

[0039] The four new pollutants, sulfamethoxazole, carbamazepine, propranolol and ibuprofen, are degraded by using the electrochemically activated persulfate system, and the initial concentration of the new pollutants is 5 μM; then, the four new pollutants are degraded by using the pyrite coupled with the electrochemically activated persulfate.

[0040] Figure 2 The degradation results of the new pollutants before and after the pyrite and electrochemical coupling are shown in Table 1. Figure 2 It can be known that the removal rates of the four new pollutants by the electrochemically activated persulfate are 63.30%, 81.66%, 70.55% and 59.24% respectively, and the removal rates of the four new pollutants by the pyrite coupled with the electrochemical coupling are 90.31%, 99.17%, 97.13% and 90.16% respectively, and the removal rates are increased by 20.92%-27.51%.

[0041] The coupling of the pyrite and the electrochemistry can improve the removal efficiency of the new pollutants, and the pyrite coupled with the electrochemically activated persulfate has a broad spectrum on the new pollutants, which is beneficial to the popularization and application of the present application.

[0042] Figure 3 The release of iron in the pyrite and electrochemical coupling system is shown in Table 2. Figure 3 It can be known that the total iron concentration in the pyrite and electrochemical coupling system is increased with the increase of the reaction time. The divalent iron can activate the persulfate, and the divalent iron is oxidized into trivalent iron, and the trivalent iron can be reduced into divalent iron by obtaining electrons at the cathode. That is, the existence of iron can continuously accelerate the activation of the persulfate. Therefore, the pyrite can release iron elements into the electrolyte, so as to accelerate the activation of the persulfate and the degradation of the new pollutants.

[0043] Embodiment 2

[0044] The embodiment provides a reaction active species in the pyrite and electrochemical coupling system

[0045] The free radicals in the coupling system are identified by electron paramagnetic resonance. 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) is added to the coupling system to capture hydroxyl radicals, sulfate radicals and superoxide radicals in the system, and 2,2,6,6-tetramethylpiperidine (TEMP) is added to capture singlet oxygen in the system, to form corresponding adducts. Sampling is performed and electron paramagnetic resonance spectrometer is used for determination. If there is a certain free radical, corresponding signal peaks will appear in the electron paramagnetic resonance spectrum. Since the adduct of DMPO and superoxide radical is unstable in aqueous solution, the determination of superoxide radical is carried out in 85% methanol solution.

[0046] Figure 4 (a) and Figure 4 (b) are the electron paramagnetic resonance spectra of the coupling system in aqueous solution and 85% methanol solution, respectively. It can be seen from Figure 4 (a) and Figure 4 (b) that there are hydroxyl radicals, sulfate radicals, singlet oxygen and superoxide radicals in the coupling system.

[0047] There are a variety of reactive species in the coupling system, which have strong oxidizing ability and broad spectrum, so that the pyrite coupled electrochemical activation of persulfate has excellent removal effect and broad spectrum on new pollutants.

[0048] Example 3

[0049] This example provides a determination by a probe whether there is ferric iron in the coupling system.

[0050] Methyl phenyl sulfoxide (PMSO) is used as a probe for ferric iron, because PMSO will be oxidized to methyl phenyl sulfone (PMSO2) by ferric iron specifically, while other free radicals will react with PMSO to form corresponding biphenyl and hydroxylated products. Therefore, if PMSO2 is detected, it indicates that there is ferric iron in the coupling system.

[0051] Figure 4 (c) is the result of the probe test. It can be seen from Figure 4 (c) that the concentration of PMSO gradually decreases and the concentration of PMSO2 gradually increases with the progress of the reaction, indicating that there is ferric iron in the coupling system. Ferric iron has strong oxidizing ability and can quickly oxidize new pollutants.

[0052] Example 4

[0053] This example provides a verification of the reusability of pyrite

[0054] After each use, the pyrite powder is suspended or floated in the electrolyte of the coupling system, and the used pyrite is recovered by filtration, washing and drying, and is repeated. Figure 5 The degradation of sulfamethazine by the coupling system when the pyrite is reused. It can be seen from Figure 5It can be seen that the removal rate of sulfamethazine in the coupling system was 98.74% when pyrite was used for the first time, and the removal rates of sulfamethazine were 97.47%, 91.33%, 89.25% and 85.75% when pyrite was used for the second to fifth times. In the repeated use of pyrite, the removal rate of sulfamethazine in the coupling system always maintained at a high level, indicating that pyrite could always effectively promote the activation of persulfate in the repeated use process. In other words, pyrite has good stability and reusability in the coupling system.

[0055] Example 5

[0056] The present embodiment provides the operation cost accounting of the coupling system

[0057] The operation cost of the electrochemically activated persulfate system and the coupling system mainly includes two parts of electric energy consumption and reagent consumption. Among them, the electric energy consumption can be evaluated by the unit electric energy consumption (EE / O), which means the electric energy consumed to reduce the pollutant concentration to 1 / 10 of its initial concentration. The calculation formula is as follows: 3 The electric energy consumed to reduce the pollutant concentration to 1 / 10 of its initial concentration, the calculation formula is as follows:

[0058]

[0059] Wherein, P represents the total power (kW), t represents the reaction time (min), V represents the solution volume (L), C0 represents the initial concentration of the pollutant, C t represents the pollutant concentration at t time, and k represents the rate constant of the pollutant degradation (min -1 ).

[0060] The EE / O calculation parameters and values of the electrochemically activated persulfate system and the coupling system for degrading sulfamethazine are shown in Table 1.

[0061] Table 1 EE / O calculation of the electrochemically activated persulfate system and the coupling system for degrading sulfamethazine

[0062]

[0063] In order to more intuitively compare the electric energy consumption and the reagent consumption, the reagent consumption is evaluated by the unit reagent consumption (Reagent / O), which means the amount of reagent consumed to reduce the pollutant concentration to 1 / 10 of its initial concentration. The calculation formula is as follows:

[0064]

[0065] Wherein, [Reagent]0 and [Reagent] t represent the concentrations of the reagent at the beginning of the reaction and at t time, and C0 and C tC0 and Ct represent the concentration of pollutants at the beginning of the reaction and at time t, respectively, Reagent / O is in kg m -3 .

[0066] The reagent consumed in the electrochemically activated persulfate system is persulfate, and the reagent consumed in the coupling system includes persulfate and pyrite. The Reagent / O calculation parameters and calculated values of the two systems for degrading sulfamethazine are shown in Table 2 and Table 3, respectively.

[0067] Table 2 Reagent / O calculation of electrochemically activated persulfate for degrading sulfamethazine

[0068]

[0069] Table 3 Reagent / O calculation of pyrite coupled electrochemically activated persulfate for degrading sulfamethazine

[0070]

[0071] In sewage treatment plants, industrial electricity is generally charged by ladder, and the average is 0.7 yuan per degree; the price of potassium peroxymonosulfate composite salt is between 5-7 yuan per kilogram, and the intermediate value is 6 yuan per kilogram; and the price of pyrite is about 500 yuan per ton. Therefore, the actual cost of the two systems can be calculated, and the results are shown in Table 4.

[0072] Table 4 Cost of electrochemically activated persulfate system and coupling system for degrading sulfamethazine

[0073]

[0074] As can be seen from Table 1, Table 2, Table 3 and Table 4, although the coupling system increases the addition of pyrite on the basis of the electrochemically activated persulfate system, the total cost is actually decreased. Compared with the electrochemically activated persulfate system, the electricity cost and reagent cost of the coupling system are decreased by 69.62% and 63.16%, respectively, indicating that the present application has great advantages in economy compared with the simple electrochemically activated persulfate, and is conducive to its popularization and application.

[0075] The above merely describes preferred embodiments of the present application, and is not intended to limit the present application in any form or in essence. It should be noted that those skilled in the art can make some improvements and supplements without departing from the method of the present application, and these improvements and supplements should also be considered as the protection scope of the present application. For those skilled in the art, some slight changes, modifications and equivalent changes made by using the disclosed technical content without departing from the spirit and scope of the present application are equivalent embodiments of the present application; meanwhile, any equivalent changes, modifications and evolution made according to the essential technology of the present application to the above embodiments are still within the scope of the technical solutions of the present application.

Claims

1. A method for electrochemically activating persulfate coupled with pyrite, characterized in that, The method includes the following steps: 1) Pretreatment of pyrite: Natural pyrite is crushed into particles, the obtained pyrite particles are soaked in acid solution, washed with pure water, vacuum dried, ground into powder, and sieved to obtain uniform pyrite powder. 2) Construction of the electrochemically activated monopersulfate system: A 2cm × 4cm titanium-based iridium-tantalum electrode was used as the anode and cathode. An electrolyte was prepared, the temperature in the constant-temperature water bath was controlled, and an 80mA power supply was used with a current density of 5mA / cm². 2 The electrolyte is an aqueous solution containing 1 mM monopersulfate and 5 mM sodium perchlorate. The monopersulfate is a potassium hydrogen monopersulfate complex salt with KHSO5 ≥ 47%. 3) Coupling of pyrite with electrochemically activated monopersulfate system: Add the pyrite powder obtained in step 1) to the electrolyte in step 2), stir evenly, turn on the power, and start activation; The apparatus used includes a power supply, an electrolytic cell, a constant temperature water bath, a titanium-based iridium-tantalum anode connected to the positive terminal of the power supply, and a titanium-based iridium-tantalum cathode connected to the negative terminal of the power supply. The titanium-based iridium-tantalum anode and cathode are suspended in the electrolytic cell, which is located in the constant temperature water bath. Pretreated pyrite is added to the electrolyte. The power supply is a DC power supply, and the electrolytic cell is also equipped with a stirring device.

2. The method for coupled electrochemical activation of persulfate with pyrite according to claim 1, characterized in that, In step 1), the acid solution is a 1M dilute hydrochloric acid solution.

3. The method for coupled electrochemical activation of persulfate with pyrite according to claim 1, characterized in that, In step 1), natural pyrite is crushed into particles with a diameter of less than 1 cm and sieved through a 300-mesh screen.

4. The method for coupled electrochemical activation of persulfate monosulfate with pyrite according to claim 1, characterized in that, In step 2), the temperature of the constant temperature water bath is 25℃, the speed of the stirring device is 300r / min, and the power-on time is 30min.

5. The method for coupled electrochemical activation of persulfate with pyrite according to claim 1, characterized in that, In step 3), the concentration of pyrite powder is 100 mg / L.

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