CN106745538B - Method for recovering elemental phosphorus from hypophosphite wastewater - Google Patents
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Abstract
The invention provides a method for recovering elemental phosphorus from hypophosphite wastewater, which adopts Pd/g-C3N4The electrode is a cathode to construct a photoelectrocatalysis reaction system, the electron migration is enhanced and the generation amount of active hydrogen is improved through the photoelectricity synergistic effect, the hypophosphite is catalyzed to be reduced at the cathode, and a reduction product is recovered from hypophosphite wastewater in the form of simple substance phosphorus. The method provided by the invention can obtain a recovered product with higher phosphorus content, and the recovery rate reaches more than 70%. The reduction product exists in the form of simple substance phosphorus, so that a large amount of chemical sludge is avoided, and secondary pollution is reduced; and the method does not contain impurities such as heavy metals and the like, and can be directly applied to processing and utilizing phosphorus-containing products. Pd/g-C3N4The electrode has stable performance, can be repeatedly used, does not need to add excessive medicament in the process of recovering the elemental phosphorus, reduces the using amount of the medicament and improves the using rate of the medicament. The method provided by the invention is simple and convenient to operate and can be suitable for industrial production with amplification.
Description
Technical Field
The invention relates to the technical field of recovering elemental phosphorus from wastewater, in particular to a method for recovering elemental phosphorus from hypophosphite wastewater.
Background
In recent years, with the development of industry, the surface treatment industries such as electroplating and chemical plating are rapidly developed, and hypophosphite is widely applied to surface treatment due to the characteristics of low toxicity and strong reducibility. Due to the development of the surface treatment industry, more than 4.0 million cubic meters of plating bath wastewater is generated every year in a large date. In a large amount of generated plating bath wastewater, the total phosphorus concentration is higher and can reach 3000 mg/L. At present, the treatment of the plating bath wastewater focuses on the treatment of heavy metal and toxic anions, and the treatment of hypophosphite is less.
The traditional method for treating hypophosphite in the plating bath wastewater is a chemical precipitation method, and the method is characterized in that hypophosphite is oxidized into orthophosphate firstly, and then the orthophosphate is removed in a precipitation mode, wherein the step of oxidizing the hypophosphite into the orthophosphate is a control step of the method. Chemical fenton, photo-fenton and electro-fenton are used to oxidize hypophosphite, and electro-fenton has relatively good effect on hypophosphite. Phosphite with a valence of +3 is generated in the oxidation process of hypophosphite, and the phosphite has strong electrochemical inertia and is difficult to be oxidized into orthophosphate, so that the removal rate of the hypophosphite is low. In addition, phosphites are readily soluble in water and difficult to form an effective precipitate, resulting in lower removal of hypophosphite. In order to achieve better phosphorus removal effect, excessive calcium salt or iron salt is usually added in the oxidation process of hypophosphite, and although the excessive calcium salt or iron salt can increase the oxidation of the hypophosphite, the added amount is large, and the total utilization rate of the calcium salt or iron salt is not high.
In recent years, a phosphorus recovery technique by crystallization is one of effective methods for recovering soluble phosphate from sewage. In the application of the crystallization method phosphorus recovery technology, a struvite crystallization reactor, a productive fluidized bed reactor for recovering calcium phosphate or an iron phosphate Krepro precipitation device is generally arranged in a sewage treatment process, wherein the struvite crystallization reactor is arranged to be capable of recovering more than 70% of soluble phosphate in sewage; the arrangement of a productive fluidized bed reactor for recovering calcium phosphate enables the recovery of calcium phosphate with a phosphorus content of 11%; and (3) arranging a Krepro precipitation device for recovering the iron phosphate with the phosphorus content of 10 percent. However, according to practical application research, the pH of the wastewater generated by surface treatment is generally 2.0-10.0, struvite is easily formed under a strong alkaline condition with the pH of 10.0-11.0, but the optimal pH range for forming high-purity struvite is 7.0-7.5, but the rate of forming struvite is very slow when the pH is 7.0-7.5, which is about 24 hours or more, and obviously, such a reaction period is difficult to be applied in a practical engineering with a large discharge amount. Although the crystallization method phosphorus recovery technology can recover soluble phosphate in sewage, the method cannot realize the large-scale recovery of the soluble phosphate.
Disclosure of Invention
The invention provides a method for recovering simple substance phosphorus from hypophosphite wastewater, which aims to solve the problem of low recovery rate of hypophosphite due to difficult recovery of hypophosphite and low utilization rate after medicament input in the prior art.
The hypophosphite wastewater is mainly from electroplating or chemical plating bath solution wastewater or cleaning wastewater. In the hypophosphite wastewater, the content of total phosphorus is 500-3000 mg/L, the pH value of the hypophosphite wastewater is 2.0-10.0, and if the hypophosphite wastewater is directly discharged, the influence on the surrounding environment is caused, a large amount of phosphorus resources are wasted, and the recycling of substances is not facilitated.
The invention provides a method for recovering elemental phosphorus from hypophosphite wastewater, which is used for recovering phosphorus resources in the hypophosphite wastewater. The method for recovering the elemental phosphorus from the hypophosphite wastewater comprises the following steps:
constructing a photoelectrocatalysis reaction system, wherein graphite or stainless steel is used as an anode plate, and Pd/g-C3N4The electrode is a cathode plate, visible light is used as a light source, and the proton exchange membrane correspondingly isolates the photoelectrocatalysis reaction system into an anode chamber and a cathode chamber; adjusting the plate interval between the anode plate and the cathode plate to be 1-10 cm; pumping ammonium citrate, sodium sulfate and hypophosphite wastewater into the photoelectrocatalysis reaction system, and controlling the pH value of the hypophosphite wastewater to be 3.0-6.0; turning on the light source and the power supply to perform a photoelectrocatalysis reaction; collecting the precipitate in the cathode chamber after the photoelectrocatalysis reaction is finished; and (3) freezing and drying the precipitate in vacuum to obtain a recovered product containing the elemental phosphorus.
In the method for recovering the elemental phosphorus from the hypophosphite wastewater, ammonium citrate with the concentration of 1mol/L is used as a buffer solution for adjusting the pH value of the hypophosphite wastewater to 3.0-6.0, preferably 5.0. Sodium sulfate with a concentration of 0.5mol/L is used as an electrolyte to provide a conductive medium. The condition of freeze vacuum drying of the precipitate is drying for 2 hours at the temperature of-70 to-80 ℃.
In the method for recovering the elemental phosphorus from the hypophosphite wastewater, the graphite or the stainless steel is used as an anode plate, and Pd/g-C3N4The electrode is a cathode plate, visible light is used as a light source to construct a photoelectrocatalysis reaction system, and the catalytic reaction principle of the photoelectrocatalysis reaction system is as follows:
visible light excitation:
direct reduction: e.g. of the type-+H2PO2 -→P；
Indirect reduction: e.g. of the type-+H++Pd→H；
H+e-+Pd→H·；
H·+H2PO2 -→P。
In the above catalytic reaction principle, g-C is excited by visible light3N4Electrons and holes are generated, and the generated electrons catalytically reduce the hypophosphite to elemental phosphorus. The process of electronically catalyzing and reducing hypophosphite is divided into direct reduction and indirect reduction, and the indirect reduction is a main reduction process. When the hypophosphite is directly reduced, electrons directly catalyze the hypophosphite to form simple substance phosphorus; during indirect reduction, electrons are promoted to be transferred to Pd under the action of an electric field, the Pd can generate active hydrogen after obtaining the electrons, the active hydrogen catalyzes hypophosphite to be reduced on the surface of a cathode, and a reduction product recovers a recovery product containing the elemental phosphorus from hypophosphite wastewater in the form of the elemental phosphorus.
The phosphorus-containing recovered product prepared by the method for recovering elemental phosphorus from hypophosphite wastewater provided by the invention is subjected to SEM (scanning electron microscope), XRD (X-ray diffraction), XPS (X-ray photoelectron spectroscopy) and elemental analysis detection, so as to show the appearance, main phase and valence state of phosphorus in the phosphorus-containing recovered product and the content of phosphorus in the phosphorus-containing recovered product.
Referring to FIG. 1, FIG. 1 shows an SEM image of a phosphorus-containing recovered product. From the SEM image, it can be seen that the recovered phosphorus-containing product has a smooth surface and uniformly dispersed particles, and thus is easily dispersed in other solid or liquid reagents when being recycled.
Referring to FIG. 2, FIG. 2 shows an XRD pattern of a phosphorus-containing recovered product. As can be seen from the XRD patterns, the crystal structure of the C element appears at diffraction angles of 26.5 ° and 77.8 °; the crystal structure of Pd element appeared at diffraction angles of 40 °, 47.2 °, and 83.6 °; the crystal structure of the element P appeared at the diffraction angles of 54.1 ° and 68 °, and it was found that the recovered product containing phosphorus contained C, Pd and P, and had no materials such as heavy metals.
Referring to FIG. 3, FIG. 3 shows an XPS plot of phosphorus-containing recovery products. It can be seen from the XPS chart that peaks of elemental phosphorus occur at binding energies of 135.2eV, 131.2eV, and 130.4eV, and thus it is found that the valence of phosphorus in the recovered product containing phosphorus is zero.
Referring to Table 1, the elemental analysis results for the recovered product containing phosphorus are shown in Table 1.
Table 1: elements and mass concentration of phosphorus-containing recovery product
| Element(s) | Mass concentration (wt.%) |
| O | 0.0 |
| Na | 5.72 |
| P | 14.04 |
| Pd | 80.24 |
As can be seen from table 1, the phosphorus-containing recovered product contained three elements of Na, P and Pd, and the mass concentration of P was 14.04%. Due to different experimental conditions, the mass concentration of P in the prepared phosphorus-containing recycled product is different, and the mass concentration of P is generally 13-17%. No Na was detected in the XRD examination, which may be due to the Na peaks being covered by the peaks of other substances. Since XRD detection is detection in air, CO in air2The detection of the C element can be influenced, so that the characteristic diffraction peak of the C element appears in XRD detection.
The method for recovering the simple substance phosphorus from the hypophosphite wastewater provided by the invention can obtain a recovered product with higher phosphorus content, and the recovery rate is higher and can reach more than 70%. The reduction product exists in the form of simple substance phosphorus, so that a large amount of chemical sludge can be avoided, and secondary pollution is reduced, so that the pollution treatment pressure of a sewage treatment plant is relieved; and the recovered product does not contain impurities such as heavy metals and the like, and can be directly applied to the processing and utilization of phosphorus-containing products, thereby bringing certain economic benefits to pollution discharge enterprises. In addition, Pd/g-C3N4The electrode performance of the electrode is stable, and the electrode can be repeatedly used for many times, so that excessive medicament does not need to be added in the process of recovering the simple substance phosphorus from the hypophosphite wastewater, the use amount of the medicament is reduced, and the use rate of the medicament is improved. The method for recovering the simple substance phosphorus from the hypophosphite wastewater provided by the invention is simple and convenient to operate, and can be suitable for industrial production with amplification.
In the method for recovering the elemental phosphorus from the hypophosphite wastewater provided by the invention, Pd/g-C is adopted3N4The electrode is a cathode, wherein Pd/g-C3N4The preparation method of the electrode comprises the following steps:
and (2) mixing thiourea and cyanuric acid according to a mass concentration ratio of 1: 1, uniformly mixing to form a mixture a;preparing the mixture a into powder g-C by a sol-gel method3N4(ii) a Mixing the powder g-C3N4Mixing polyvinylpyrrolidone (PVP) and flake or blocky graphite to form a mixture b, wherein the addition amount of the polyvinylpyrrolidone is 0.1-1% of the total mass of the thiourea and the cyanuric acid; the mixture b is thermally polymerized for 5h at the temperature of 500 ℃ to obtain g-C3N4A graphite electrode; dissolving palladium chloride in distilled water to prepare a palladium chloride solution with the concentration of 0.1-2 mol/L; subjecting said g-C to3N4Graphite electrode is placed in the palladium chloride solution at a current density of 0.2mA/cm2Prepared by cyclic voltammetry under the condition of (1) to obtain Pd/g-C3N4And an electrode.
At Pd/g-C3N4In the preparation process of the electrode, PVP can promote g-C3N4Adhering to flake or block graphite and forming g-C by thermal polymerization3N4A graphite electrode. Lower amounts of PVP do not result in g-C3N4Completely adhere to the graphite flakes or blocks, while excess PVP adheres to the graphite flakes or blocks, resulting in g-C3N4Cannot be thermally polymerized with graphite to affect g-C3N4Quality of graphite electrode produced, therefore, Pd/g-C provided in the present invention3N4In the preparation method of the electrode, the addition amount of PVP is preferably 0.5% of the total mass of thiourea and cyanuric acid.
Referring to fig. 4, fig. 4 is a schematic diagram of a reaction device for recovering elemental phosphorus from hypophosphite wastewater, which corresponds to a photoelectrocatalysis reaction system. In the reaction device, a reactor main body 1 is formed by organic glass, the reactor main body 1 is separated into an anode chamber and a cathode chamber by a proton exchange membrane, and an anode plate 2 taking graphite or stainless steel as an anode and a Pd/g-C are respectively arranged in the anode chamber and the cathode chamber3N4The electrode is the negative plate 3 of negative pole, and the board interval between positive plate 2 and the negative plate 3 is 1 ~ 10 cm. Preferably between the anode plate 2 and the cathode plate 3The distance is 2 cm. Since the photoelectrocatalytic reaction mainly occurs in the cathode chamber, the anode chamber and the cathode chamber are set to have a volume ratio of 1: 5, in order to deposit more recovered product. Further, the proton exchange membrane adopts a perfluorosulfonic acid (Nafion) proton exchange membrane, so that the protons in the hypophosphite wastewater can completely pass through the proton exchange membrane.
In the reaction device, visible light such as fluorescent lamp light, sunlight or xenon lamp light is used as a light source 5, and the light source 5 is placed in a quartz sleeve 4 with good light transmittance. In the process of the photoelectrocatalysis reaction, the illumination intensity of the light source 5 is 10-100W. Preferably, the light intensity of visible light is 40W, so that the photoelectrocatalysis reaction is stably performed.
The anode plate 2 and the cathode plate 3 are respectively communicated with a direct current power supply 8, so that the direct current power supply 8 provides electric energy for the anode plate 2 and the cathode plate 3. In the process of the photoelectrocatalysis reaction, the current density of the direct current power supply 8 is 0.5-50 mA/cm2. Preferably, the current density of the DC power supply 8 is 2mA/cm2At this time, the cathode plate 3 can stably and continuously reduce hypophosphite in the hypophosphite wastewater, and can save electric energy.
The technical scheme provided by the embodiment of the invention can have the following beneficial effects:
the invention provides a method for recovering elemental phosphorus from hypophosphite wastewater, which comprises the following steps: constructing a photoelectrocatalysis reaction system, wherein graphite or stainless steel is used as an anode plate, and Pd/g-C3N4The electrode is a cathode plate, visible light is used as a light source, and the proton exchange membrane separates the photoelectrocatalysis reaction system into an anode chamber and a cathode chamber; adjusting the plate interval between the anode plate and the cathode plate to be 1-10 cm; pumping ammonium citrate, sodium sulfate and hypophosphite wastewater into the photoelectrocatalysis reaction system, and controlling the pH value of the hypophosphite wastewater to be 3.0-6.0; turning on the light source and the power supply to perform a photoelectrocatalysis reaction; collecting the precipitate in the cathode chamber after the photoelectrocatalysis reaction is finished; and (3) freezing and drying the precipitate in vacuum to obtain a recovered product containing the elemental phosphorus.
The invention provides a method for removing hypophosphite from wastewaterThe method for recovering simple substance phosphorus is characterized by using graphite or stainless steel as anode plate and Pd/g-C3N4The electrode is a cathode plate, visible light is used as a light source to construct a photoelectrocatalysis reaction system, and g-C is excited by the visible light3N4Electrons and holes are generated, the electrons are promoted to be transferred to Pd under the action of an electric field, active hydrogen can be generated after the Pd obtains the electrons, the active hydrogen catalyzes hypophosphite to be reduced on the surface of a cathode, and a reduction product recovers a recovery product containing the elemental phosphorus from hypophosphite wastewater in the form of the elemental phosphorus. The method for recovering the simple substance phosphorus from the hypophosphite wastewater provided by the invention can obtain a recovered product with higher phosphorus content, and the recovery rate is higher and can reach more than 70%. The reduction product exists in the form of simple substance phosphorus, so that a large amount of chemical sludge can be avoided, and secondary pollution is reduced, so that the pollution treatment pressure of a sewage treatment plant is relieved; and the recovered product does not contain impurities such as heavy metals and the like, and can be directly applied to the processing and utilization of phosphorus-containing products, thereby bringing certain economic benefits to pollution discharge enterprises. In addition, Pd/g-C3N4The electrode performance of the electrode is stable, and the electrode can be repeatedly used for many times, so that excessive medicament does not need to be added in the process of recovering the simple substance phosphorus from the hypophosphite wastewater, the use amount of the medicament is reduced, and the use rate of the medicament is improved. The method for recovering the simple substance phosphorus from the hypophosphite wastewater provided by the invention is simple and convenient to operate, and can be suitable for industrial production with amplification.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and together with the description, serve to explain the principles of the invention.
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without inventive exercise.
FIG. 1 is an SEM image of a recovered product provided by an embodiment of the present invention;
FIG. 2 is an XRD pattern of a recovered product provided by an embodiment of the present invention;
FIG. 3 is an XPS plot of recovered product as provided by an embodiment of the present invention;
FIG. 4 is a schematic diagram of a reaction apparatus for recovering elemental phosphorus from hypophosphite wastewater according to an embodiment of the present invention;
FIG. 5 is a schematic flow chart of a method for recovering elemental phosphorus from hypophosphite wastewater according to an embodiment of the present invention;
the symbols represent:
1-a reactor body, 2-an anode plate, 3-a cathode plate, 4-a quartz sleeve, 5-a light source, 6-a proton exchange membrane, 7-a pH meter, 8-a direct current power supply, 9-an absorption tank, 10-a metering pump, 11-a magnetic stirrer, 12-a raw material tank and 13-a waste liquid tank.
Detailed Description
Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the invention, as detailed in the appended claims.
Referring to FIG. 5, FIG. 5 is a schematic flow chart of a method for recovering elemental phosphorus from hypophosphite wastewater according to an embodiment of the present invention, and the following description of the embodiment is based on FIG. 1.
Example 1
The method for recovering the elemental phosphorus from the hypophosphite wastewater provided by the embodiment of the invention comprises the following steps:
s101: constructing a photoelectrocatalysis reaction system, wherein graphite is taken as an anode plate 2, and Pd/g-C3N4The electrode is a cathode plate 3, the xenon lamp is a light source 5, and a Nafion proton exchange membrane 6 correspondingly arranges a photoelectrocatalysis reaction systemThe device is isolated into an anode chamber and a cathode chamber, and the volume ratio of the anode chamber to the cathode chamber is 1: 5;
s102: adjusting the plate interval between the anode plate and the cathode plate to be 2cm, and inserting a pH meter 7 into a device corresponding to the photoelectrocatalysis reaction system;
s103: ammonium citrate, sodium sulfate and hypophosphite wastewater in a raw material pool 12 are pumped into the cathode chamber by a metering pump 10, and the pH value of the hypophosphite wastewater is controlled to be 5.0, wherein the pumping flow rate is 0.5m3/h；
S104: starting the xenon lamp and the direct current power supply 10, adjusting the illumination intensity of the xenon lamp to 40W, and adjusting the current density of the direct current power supply 10 to 2mA/cm2(ii) a Adjusting the rotation speed of the magnetic stirrer 11 to 300rpm to carry out the photoelectrocatalysis reaction;
s105: collecting the precipitate in the cathode chamber after the photoelectrocatalysis reaction is finished, discharging the waste liquid into a waste liquid pool 13, and absorbing the gas generated in the reaction by an absorption pool 9;
s106: and (3) freezing and vacuum-drying the precipitate at the temperature of-75 ℃ for 2h to obtain a recovered product containing the elemental phosphorus.
Wherein, Pd/g-C3N4The preparation method of the electrode comprises the following steps:
and (2) mixing thiourea and cyanuric acid according to a mass concentration ratio of 1: 1, uniformly mixing to form a mixture a;
preparing the mixture a into powder g-C by a sol-gel method3N4；
Mixing the powder g-C3N4Mixing polyvinylpyrrolidone with flake or blocky graphite to form a mixture b, wherein the addition amount of the polyvinylpyrrolidone is 0.5% of the total mass of thiourea and cyanuric acid;
the mixture b is thermally polymerized for 5h at a temperature of 500 ℃ to obtain g-C3N4A graphite electrode;
dissolving palladium chloride in distilled water to prepare a palladium chloride solution with the concentration of 1 mol/L;
g-C obtained by the preparation3N4Graphite electrode is placed in palladium chloride solution at current density of 0.2mA/cm2Prepared by cyclic voltammetry under the condition of (1) to obtain Pd/g-C3N4And an electrode.
The mass concentration of phosphorus in the recovered product was found to be 16.53% by elemental analysis.
Example 2
The method for recovering the elemental phosphorus from the hypophosphite wastewater provided by the embodiment of the invention comprises the following steps:
s201: constructing a photoelectrocatalysis reaction system, wherein stainless steel is taken as an anode plate 2, and Pd/g-C3N4The electrode is cathode plate 3, the fluorescent lamp is light source 5, Nafion proton exchange membrane 6 separates the corresponding device of photoelectrocatalysis reaction system into anode chamber and cathode chamber, the volume ratio of anode chamber and cathode chamber is 1: 5;
s202: adjusting the plate interval between the anode plate and the cathode plate to be 1cm, and inserting a pH meter 7 into a device corresponding to the photoelectrocatalysis reaction system;
s203: ammonium citrate, sodium sulfate and hypophosphite wastewater in a raw material pool 12 are pumped into the cathode chamber by a metering pump 10, and the pH value of the hypophosphite wastewater is controlled to 3.0, wherein the pumping flow rate is 0.5m3/h；
S204: the fluorescent lamp and the DC power supply 10 are turned on, the illumination intensity of the fluorescent lamp is adjusted to 10W, and the current density of the DC power supply 10 is 0.5mA/cm2(ii) a Adjusting the rotation speed of the magnetic stirrer 11 to 300rpm to carry out the photoelectrocatalysis reaction;
s205: collecting the precipitate in the cathode chamber after the photoelectrocatalysis reaction is finished, discharging the waste liquid into a waste liquid pool 13, and absorbing the gas generated in the reaction by an absorption pool 9;
s206: and (3) freezing and vacuum-drying the precipitate at the temperature of-70 ℃ for 2h to obtain a recovered product containing the elemental phosphorus.
Wherein, Pd/g-C3N4The preparation method of the electrode comprises the following steps:
and (2) mixing thiourea and cyanuric acid according to a mass concentration ratio of 1: 1, uniformly mixing to form a mixture a;
preparing the mixture a into powder g-C by a sol-gel method3N4；
Mixing the powder g-C3N4Mixing polyvinylpyrrolidone with flake or blocky graphite to form a mixture b, wherein the addition amount of the polyvinylpyrrolidone is 0.1% of the total mass of thiourea and cyanuric acid;
the mixture b is thermally polymerized for 5h at a temperature of 500 ℃ to obtain g-C3N4A graphite electrode;
dissolving palladium chloride in distilled water to prepare a palladium chloride solution with the concentration of 0.1 mol/L;
g-C obtained by the preparation3N4Graphite electrode is placed in palladium chloride solution at current density of 0.2mA/cm2Prepared by cyclic voltammetry under the condition of (1) to obtain Pd/g-C3N4And an electrode.
The mass concentration of phosphorus in the recovered product was 14.04% by elemental analysis.
Example 3
The method for recovering the elemental phosphorus from the hypophosphite wastewater provided by the embodiment of the invention comprises the following steps:
s301: constructing a photoelectrocatalysis reaction system, wherein graphite is taken as an anode plate 2, and Pd/g-C3N4The electrode is cathode plate 3, sunlight is light source 5, and Nafion proton exchange membrane 6 keeps apart the corresponding device of photoelectrocatalysis reaction system for anode chamber and cathode chamber, and the volume ratio of anode chamber and cathode chamber is 1: 5;
s302: adjusting the plate interval between the anode plate and the cathode plate to be 10cm, and inserting a pH meter 7 into a device corresponding to the photoelectrocatalysis reaction system;
s303: ammonium citrate, sodium sulfate and hypophosphite wastewater in a raw material pool 12 are pumped into the cathode chamber by a metering pump 10, the pH value of the hypophosphite wastewater is controlled to be 6.0, wherein the pumping flow rate is 0.5m3/h；
S304: introducing sunlight, controlling the illumination intensity of the sunlight to be 100W, starting the direct current power supply 10, and adjusting the current density of the direct current power supply 10 to be 50mA/cm2B, carrying out the following steps of; adjusting the rotation speed of the magnetic stirrer 11 to 300rpm to carry out the photoelectrocatalysis reaction;
s305: collecting the precipitate in the cathode chamber after the photoelectrocatalysis reaction is finished, discharging waste liquid into a waste liquid pool 13, and absorbing gas generated in the reaction by an absorption pool 9;
s306: and (3) freezing and vacuum-drying the precipitate at the temperature of-80 ℃ for 2h to obtain a recovered product containing the elemental phosphorus.
Wherein, Pd/g-C3N4The preparation method of the electrode comprises the following steps:
and (2) mixing thiourea and cyanuric acid according to a mass concentration ratio of 1: 1, uniformly mixing to form a mixture a;
preparing the mixture a into powder g-C by a sol-gel method3N4；
Mixing the powder g-C3N4Mixing polyvinylpyrrolidone with flake or blocky graphite to form a mixture b, wherein the addition amount of the polyvinylpyrrolidone is 1% of the total mass of thiourea and cyanuric acid;
the mixture b is thermally polymerized for 5h at a temperature of 500 ℃ to obtain g-C3N4A graphite electrode;
dissolving palladium chloride in distilled water to prepare a palladium chloride solution with the concentration of 2 mol/L;
g-C obtained by the preparation3N4Graphite electrode is placed in palladium chloride solution at current density of 0.2mA/cm2Prepared by cyclic voltammetry under the condition of (1) to obtain Pd/g-C3N4And an electrode.
The mass concentration of phosphorus in the recovered product was 15.25% by elemental analysis.
Example 4
The method for recovering the elemental phosphorus from the hypophosphite wastewater provided by the embodiment of the invention comprises the following steps:
s401: constructing a photoelectrocatalysis reaction system, wherein stainless steel is taken as an anode plate 2, and Pd/g-C3N4The electrode is cathode plate 3, sunlight is light source 5, and Nafion proton exchange membrane 6 keeps apart the corresponding device of photoelectrocatalysis reaction system for anode chamber and cathode chamber, and the volume ratio of anode chamber and cathode chamber is 1: 5;
s402: adjusting the plate interval between the anode plate and the cathode plate to be 6cm, and inserting a pH meter 7 into a device corresponding to the photoelectrocatalysis reaction system;
s403: ammonium citrate, sodium sulfate and hypophosphite wastewater in a raw material pool 12 are pumped into the cathode chamber by a metering pump 10, the pH value of the hypophosphite wastewater is controlled to be 4.0, wherein the pumping flow rate is 0.5m3/h；
S404: introducing sunlight, controlling the illumination intensity of the sunlight to be 80W, starting the direct current power supply 10, and adjusting the current density of the direct current power supply 10 to be 25mA/cm2B, carrying out the following steps of; adjusting the rotation speed of the magnetic stirrer 11 to 300rpm to carry out the photoelectrocatalysis reaction;
s405: collecting the precipitate in the cathode chamber after the photoelectrocatalysis reaction is finished, discharging waste liquid into a waste liquid pool 13, and absorbing gas generated in the reaction by an absorption pool 9;
s406: and (3) freezing and vacuum-drying the precipitate at the temperature of-80 ℃ for 2h to obtain a recovered product containing the elemental phosphorus.
Wherein, Pd/g-C3N4The preparation method of the electrode comprises the following steps:
and (2) mixing thiourea and cyanuric acid according to a mass concentration ratio of 1: 1, uniformly mixing to form a mixture a;
preparing the mixture a into powder g-C by a sol-gel method3N4；
Mixing the powder g-C3N4Mixing polyvinylpyrrolidone with flake or blocky graphite to form a mixture b, wherein the addition amount of the polyvinylpyrrolidone is 0.8 percent of the total mass of thiourea and cyanuric acid;
the mixture b is thermally polymerized for 5h at a temperature of 500 ℃ to obtain g-C3N4A graphite electrode;
dissolving palladium chloride in distilled water to prepare a palladium chloride solution with the concentration of 1.5 mol/L;
g-C obtained by the preparation3N4Graphite electrode is placed in palladium chloride solution at current density of 0.2mA/cm2Prepared by cyclic voltammetry under the condition of (1) to obtain Pd/g-C3N4And an electrode.
The mass concentration of phosphorus in the recovered product was 13.68% by elemental analysis.
Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure herein. This application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.
It will be understood that the invention is not limited to the precise arrangements described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the invention is limited only by the appended claims.
Claims (8)
1. A method for recovering elemental phosphorus from hypophosphite wastewater, comprising:
constructing a photoelectrocatalysis reaction system, wherein graphite or stainless steel is used as an anode plate, and Pd/g-C3N4The electrode is a cathode plate, visible light is used as a light source, and the proton exchange membrane separates a device corresponding to the photoelectrocatalysis reaction system into an anode chamber and a cathode chamber;
adjusting the plate interval between the anode plate and the cathode plate to be 1-10 cm;
pumping ammonium citrate, sodium sulfate and hypophosphite wastewater into the photoelectrocatalysis reaction system, and controlling the pH value of the hypophosphite wastewater to be 3.0-6.0;
turning on the light source and the power supply to perform a photoelectrocatalysis reaction;
collecting the precipitate in the cathode chamber after the photoelectrocatalysis reaction is finished;
and (3) freezing and drying the precipitate in vacuum to obtain a recovered product containing the elemental phosphorus.
2. The method of claim 1, wherein the volume ratio of the anode chamber to the cathode chamber is 1: 5.
3. the method for recovering elemental phosphorus from hypophosphite wastewater as claimed in claim 1, wherein the visible light is fluorescent lamp light, sunlight or xenon lamp light.
4. The method for recovering elemental phosphorus from hypophosphite wastewater as claimed in claim 3, wherein the illumination intensity of visible light is 10-100W.
5. The method of claim 1, wherein the proton exchange membrane is a Nafion proton exchange membrane.
6. The method for recovering elemental phosphorus from hypophosphite wastewater as claimed in claim 1, wherein the current density of the power supply is 0.5-50 mA/cm2。
7. The method for recovering elemental phosphorus from hypophosphite wastewater as claimed in claim 1, wherein the step of freeze vacuum drying the precipitate to obtain a recovered product containing elemental phosphorus comprises:
and (3) freezing and vacuum drying the precipitate for 2h at the temperature of-70 to-80 ℃ to obtain a recovered product containing the elemental phosphorus.
8. The method of claim 1, wherein the current density of the power supply is 2mA/cm2The illumination intensity of the visible light is 40W, the plate interval is 2cm, and the pH value is 5.0.
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| CN108892114B (en) * | 2018-06-28 | 2023-04-25 | 四川大学 | Method for removing arsenic by electrocatalytic oxidation of yellow phosphorus and electrocatalytic oxidation impurity removal equipment |
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| CN103586064A (en) * | 2013-11-26 | 2014-02-19 | 中国科学院福建物质结构研究所 | Metal/graphite-like carbon nitride compound catalyst and preparing method thereof |
| CN105435827A (en) * | 2015-12-20 | 2016-03-30 | 华南理工大学 | Preparation method for ternary-system TiO2/WS2/g-C3N4 composite photocatalyst with visible-light activity |
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