WO2016091159A1

WO2016091159A1 - Method for recovering perfluorinated compound from sewage

Info

Publication number: WO2016091159A1
Application number: PCT/CN2015/096724
Authority: WO
Inventors: 牛军峰; 林辉
Original assignee: 北京师范大学
Priority date: 2014-12-08
Filing date: 2015-12-08
Publication date: 2016-06-16
Also published as: CN104529031A; CN104529031B

Abstract

A method for recovering perfluorinated compound from sewage, which comprises the following steps: an electric flocculation step, using an electric flocculation method to adsorb the perfluorinated compound in an aqueous solution or a water-organic solvent mixed solution onto the surface of flocs produced by electric flocculation to form sludge; an elution step, carrying out an organic solvent elution treatment on the above-mentioned sludge containing perfluorinated compound to separate the perfluorinated compound from the sludge and form a concentrated perfluorinated compound solution; and a distillation step, distilling the produced concentrated perfluorinated compound solution to obtain perfluorinated compound solids and a distillate, the distillate being used as an elution liquid of the above-mentioned elution step. Zn(OH)₂ flocs produced in situ by electric flocculation have a very high adsorption capacity and a fast adsorption rate for the perfluorinated compound and can recover high-concentration and low-concentration perfluorinated compounds from sewage and purify the sewage simultaneously. Since the electric flocculation treatment has low costs and low sludge production amount, the large-scale application of the method is economically feasible.

Description

Method for recovering perfluorochemicals from sewage

Technical field

The invention relates to a method for recovering perfluorinated compounds from sewage, belonging to the field of electrochemical technology and environmental protection.

Background technique

Perfluorinated compounds (PFCs) have been produced and used for more than 50 years as a synthetic compound. Due to its unique physical and chemical properties such as hydrophobicity, oleophobicity and high stability, it is widely used in fire extinguishing agents, surface treatment agents for photosensitive materials, surface antifouling coatings for paper, photoresists for semiconductor industry, and anti-fogging agents for electroplating. , leather finishing agents, etc., and can be used as ingredients for insecticides, herbicides, lubricants, adhesives and cosmetics. Among them, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) are the two most frequently detected PFCs in environmental media and have been detected in many environmental media: sludge, dust, water, wildlife, air. Even the human body. Due to the polarity and mobility of the substances, they can enter the ocean or groundwater without being degraded, which is a safety hazard that seriously threatens the ecological environment and the health of the population. Therefore, it is necessary to develop a control technology that efficiently removes PFCs.

Electrocoagulation technology has been widely studied and applied due to its wide application range, simple installation, simple operation, high degree of automation, low energy consumption, and low sludge production. It is considered to be the most promising technology for the treatment of refractory wastewater. One. However, the electroflocculation technology only enriches the PFCs, and the sludge produced also contains high concentrations of PFCs. If high-concentration PFCs in these sludges can be recovered, industrial PFCs can not only reduce environmental pollution, but also reduce environmental pollution. Moreover, it can reduce production costs, turn waste into treasure, and has considerable economic benefits and important environmental significance. At present, the recycling techniques for PFCs generally include a precipitation method, an ion exchange method, a foam separation method, and a nanofiltration method. Although the precipitation process is simple, it must be added with metal salts, which is easy to cause secondary pollution and is not conducive to environmental protection. The ion exchange process requires a large amount of ammonia water to be eluted, and a large amount of concentrated sulfur is also required in the acidification process. Acid, it is easy to cause secondary pollution. The combination of the foam separation method and the nanofiltration method is complicated in design and difficult to operate continuously. Therefore, it is necessary to develop a new process that is simple in process, energy-saving, efficient, and easy to industrialize.

Summary of the invention

An object of the present invention is to provide a method for recovering a perfluoro compound from sewage, the method comprising the steps of: an electroflocculation step, using an electroflocculation method to adsorb a perfluoro compound in an aqueous solution or a water-organic solvent mixture solution to electricity The surface of the floc formed by flocculation forms sludge; in the elution step, the above-mentioned perfluoro compound-containing sludge is subjected to organic solvent elution treatment to separate the perfluoro compound from the sludge, and a concentrated perfluoro compound solution is formed; distillation In the step, the produced perfluoro compound concentrate is distilled to obtain a perfluoro compound solid and a distillate, and the distillate is used as an eluent used in the above elution step.

The method for recovering a perfluoro compound from sewage according to the present invention is characterized in that the mass concentration of the perfluoro compound in the aqueous solution or the water-organic solvent mixed solution is from 1 μg/L to 100 g/L.

The method for recovering a perfluoro compound from sewage according to the present invention is characterized in that the aqueous solution or the water-organic solvent mixed solution has a pH in the range of 3 to 11.

The method for recovering a perfluoro compound from sewage according to the present invention is characterized in that, in the electroflocculation step, the anode material of the electrode is zinc and an alloy material thereof.

The method for recovering a perfluoro compound from sewage according to the present invention is characterized in that, in the electroflocculation step, the electrolysis method is direct current electrolysis or pulse electrolysis.

The method for recovering a perfluoro compound from sewage according to the present invention is characterized in that the eluent is selected from at least one organic solvent of isopropanol and ethanol.

The method for recovering a perfluoro compound from sewage according to the present invention is characterized in that the perfluoro compound is selected from a perfluoroalkyl acid (salt) having 4 to 20 carbon atoms, and a precursor thereof At least one compound.

The method for recovering a perfluoro compound from sewage according to the present invention is characterized in that the perfluoro compound is selected from the group consisting of perfluorooctanoic acid, perfluorooctane sulfonic acid, perfluorodecanoic acid, perfluorodecanoic acid, and perfluorooctane sulfonate. At least one or more compounds of the acid fluoride and perfluorooctylethyl alcohol.

The present invention also provides a sewage treatment method which is carried out by the above method for recovering a perfluoro compound.

The sewage treatment method according to the present invention is characterized in that the method is applied to drinking water, surface water, ground water and industrial sewage.

The invention has the advantages of: 1) simple process flow, convenient operation, mild reaction condition, low energy consumption, no need to add chemical reagents, good treatment effect, stable and reliable, easy to realize industrial application; 2) wide range of adaptation, effective The perfluoro compound having a concentration of 1 μg/L to 100 g/L or even the above concentration in the solution is removed; 3) the floc has the characteristics of large specific surface area and high activity. Compared with conventional activated carbon, carbon nanotubes and resins, electrocoagulation not only has the advantages of high adsorption capacity and fast adsorption rate, but more importantly, it can easily form flocculation from electric flocculation through organic solvents. The desorption and separation of the mud is carried out to realize the recycling and reuse of PFCs in the sewage. Therefore, by this technique, the low concentration PFCs in the solution can be concentrated, thereby reducing the cost of subsequent PFCs solution treatment and improving the treatment efficiency. Due to the low cost of electrocoagulation treatment and the small amount of sludge generated, large-scale application is completely economically feasible.

DRAWINGS

Figure 1 shows the performance of isopropyl alcohol eluting PFOA/S from Zn(OH) ₂ flocs.

Figure 2 shows the performance of ethanol eluting PFOA/S from Zn(OH) ₂ flocs.

detailed description

The technical solutions in the embodiments of the present invention are described in detail below with reference to the accompanying drawings in the embodiments of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without creative efforts are within the scope of the present invention.

It is to be understood that the term "comprises", "comprising" or any other variations thereof is intended to encompass a non-exclusive inclusion, such that a process, method, article, or device that comprises a It also includes other elements that are not explicitly listed, or that are inherent to such processes, methods, items, or equipment. Elements.

Compared with common adsorbents such as activated carbon, carbon nanotubes and resins, electroflocculation not only has the advantages of high adsorption capacity and fast adsorption rate, but more importantly, floc sludge which can be easily formed from electroflocculation by organic solvents. The desorption is separated and the PFCs in the sewage are recycled or reused. On the other hand, the energy consumption of electroflocculation is extremely low, and the technology is relatively mature, and there is no technical problem in practical application. The zinc hydroxide flocs produced by the electroflocculation method have a large specific surface area, and the PFCs in the solution can be quickly adsorbed on the surface of the flocs produced. Through research, we found that the flocs produced by electrocoagulation mainly remove PFCs in solution by hydrophobic interaction and hydrogen bonding. According to this characteristic, PFCs adsorbed on the surface of flocs can be released into organic solution by elution with organic solvent. Thereby, a concentrated perfluoro compound solution is produced, thereby achieving a harmless treatment. This process can concentrate PFCs in solution hundreds of times.

Example

(1) Prepare PFOA solution with concentration of 200mg/L and 500μg/L respectively; prepare PFOS solution with concentration of 200mg/L and 800μg/L respectively; prepare PFOA, PFOS, PFNA and PFDA with concentration of 100mg/L respectively. a mixed solution of PFCs; three solutions of perfluorobutanesulfonic acid (PFBS), perfluorooctanesulfonyl fluoride (POSF) and perfluorooctylethyl alcohol (8:2 FTOH) at a concentration of 200 mg/L each Preparing a water-organic solvent mixture solution with a concentration of PFOA of 200 mg/L, containing 5% isopropanol in a mixed solution; preparing a water-organic solvent mixture solution having a PFOS concentration of 500 μg/L, and containing the mass in the mixed solution The concentration of isopropyl alcohol is 5%; the pH of the above solution is adjusted by using 0.1 mol/L NaOH solution or 0.1 mol/L HCl solution to prepare a solution under different pH conditions.

(2) Plate pretreatment. When the anode material is a zinc plate, the electrode plate is pretreated, and the passivation film on the surface of the zinc plate is removed by sanding with a sandpaper and soaking for 15 minutes at a mass concentration of 10% hydrochloric acid to achieve the purpose of activating the zinc plate.

(3) The zinc plate is used as an anode, and the iron plate, aluminum plate, stainless steel or titanium plate is used as a cathode, and the solution is electrolyzed at room temperature by a direct current power source or a pulse power source at a stirring speed of 1,500 rpm. During the experiment, when DC power is used for electrolysis, the current density is 5-20 mA/cm ² , the plate spacing is 5-50 mm, and the supporting electrolyte is 20 mmol/L sodium chloride. When the pulse power is used for electrolysis, the current is 0.5-2.0 mA. /cm ² , the duty ratio is 0.2 to 0.8, and the frequency is 0.1 to 0.5 Hz.

(4) Set the reaction time gradient to 2, 5, 7, 10, 15, 20, 30 min, timed sampling analysis, and set up three parallel experiments.

(5) The above compounds were quantitatively analyzed by liquid chromatography/triple quadrupole mass spectrometry (HPLC-MS/MS, API 3200; Applied Biosystems, USA).

In the present invention, the perfluoro compound in the solution is recovered by electrocoagulation.

The perfluoro compound solution refers to an aqueous solution of a perfluoro compound or a water-organic solvent mixed solution. Here, the concentration of the perfluoro compound is not particularly limited, and the concentration of the perfluoro compound is preferably from microgram to milligram.

The aqueous solution of the perfluoro compound or the water-organic solvent mixed solution preferably has a pH in the range of 3 to 11.

The type of the perfluoro compound is not particularly limited, and the perfluoro compound is selected from a perfluoroalkyl acid having 4 to 20 carbon atoms, a perfluoroalkyl acid salt having 4 to 20 carbon atoms, and At least one of its precursors. As a specific example, one or more of the perfluoro compounds exemplified below may be contained: perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), perfluorodecanoic acid (PFNA), perfluorodecanoic acid (PFDA) ), perfluorooctane sulfonyl fluoride (POSF) and perfluorooctylethyl alcohol (8:2 FTOH).

In addition, the present invention is also applicable to a polyfluoroalkyl compound in which the polyfluoroalkyl compound is selected from a polyfluoroalkyl compound having 4 to 20 carbon atoms. Specifically, it includes N-ethyl perfluorooctane sulfonyl fluoride (N-POSF), N-ethyl perfluorooctane sulfonamide (N-EtPOSAA), 1H, 1H, 2H, 2H-perfluorooctane Sulfonic acid (6:2FTS) and the like.

In the electroflocculation method, a zinc plate and an alloy material thereof are used for the anode material.

The power source used in the electroflocculation method may be a DC power source or a pulse power source, and there is no particular limitation on current density, plate spacing, frequency, duty ratio, and the like. When electrolysis is carried out by DC power supply, the current density is preferably 5 to 20 mA/cm ² , and the electric plate spacing is preferably 5 to 50 mm; when electrolysis is performed by pulse power supply, the current is preferably 0.5 to 2.0 mA/cm ² and the duty ratio is preferably 0.2 to 0.8, the frequency is preferably 0.1 to 0.5 Hz.

According to the invention, (1) the concentration range is wide, and the perfluoro compound having a concentration of 1 μg/L to 100 g/L or even higher in the solution can be effectively removed; (2) the floc has the characteristics of large specific surface area and high activity, Therefore, it has the effect of strengthening flocculation, so the processing speed is fast, and the reaction is 30 min. The recovery rate of the perfluoro compound in the solution was 99.9% or more. The invention adopts the electroflocculation method, has the advantages of simple process flow, convenient operation, mild reaction condition, low energy consumption, good treatment effect, stable and reliable, and easy to realize industrial application; in addition, the sludge containing perfluoro compound produced is used. Harmless treatment, no need to add chemical reagents, and dewatering treatment of sludge at the same time as harmless treatment, the equipment required is simple, and it is easy to realize automatic operation.

Example 1

Electrofluidic treatment of high concentration perfluorooctanoic acid solution.

500 mL of a concentration of 200 mg / L of perfluorooctanoic acid solution was placed in an electrolytic cell, the anode zinc plate and the cathode were titanium plates, and a DC power source was used at room temperature under a current density of 10 mA/cm ² and a plate spacing of 15 mm. Perform electrolysis, timed sampling analysis. After 30 minutes of electrolytic reaction, the recovery of PFOA in the solution was 99% or more.

Example 2

Electrolytic flocculation treatment of low concentration perfluorooctanoic acid solution.

500 mL of 500 μg/L perfluorooctanoic acid solution was placed in an electrolytic cell. The anode was made of zinc plate and the cathode was made of titanium. The current density was 5 mA/cm ² and the plate spacing was 15 mm. Electrolysis is performed underneath, and sampling is performed periodically. After 10 minutes of electrolytic reaction, the recovery of PFOA in the solution was 90% or more.

Example 3

Electrofluidic treatment of a high concentration of perfluorooctane sulfonic acid solution.

500 mL of a concentration of 200 mg/L of perfluorooctane sulfonic acid solution was placed in an electrolytic cell, the anode was a zinc plate, and the cathode was a titanium plate, and the current density was 15 mA/cm ² and the plate spacing was 15 mm. Electrolysis was carried out at room temperature using a DC power source, and timed sampling analysis was performed. After 30 minutes of electrolytic reaction, the recovery of PFOS in the solution was 99.0% or more.

Example 4

The electrofluidic method is used to treat a solution containing a low concentration of perfluorooctane sulfonic acid.

500 mL of a perfluorooctane sulfonic acid solution having a concentration of 800 μg/L was placed in an electrolytic cell, the anode was a zinc plate, and the cathode was a titanium plate under the conditions of a current density of 10 mA/cm ² and a plate spacing of 15 mm. Electrolysis was carried out at room temperature using a DC power source, and timed sampling analysis was performed. After 10 minutes of electrolytic reaction, the recovery of PFOS in the solution was 95.0% or more.

Example 5

The electroflocculation process treats a mixture containing several PFCs simultaneously.

A 500 mL solution containing PFOA, PFOS, PFNA, and PFDA was placed in an electrolytic cell, wherein each PFCs had a concentration of 100 mg/L, the anode was a zinc plate, and the cathode was a titanium plate at a current density of 20 mA/cm ² . Electrolysis was carried out at room temperature using a DC power supply with a plate spacing of 20 mm, and timed sampling analysis. After 30 minutes of electrolysis, the recovery of each component in the solution was 98.0% or more.

Example 6

The perfluorooctanoic acid solution was treated by electrocoagulation using a pulsed power source.

A 500 mL, 200 mg/L perfluorooctanoic acid solution was placed in an electrolytic cell, the anode was a zinc plate, and the cathode was made of 1060 pure aluminum material. The plate spacing was 15 mm, and the duty cycle of the pulse power source was 80%. At 0.5 Hz and a pulse current of 2.0 mA/cm ² , electrolysis was carried out at room temperature, and samples were taken for analysis at different times when the electrolysis reaction was carried out. After 30 minutes of electrolytic reaction, the recovery of PFOA in the solution was 99.0% or more.

Example 7

The perfluorooctane sulfonic acid solution was treated by electrocoagulation using a pulsed power source.

A 500 mL, 500 μg/L perfluorooctane sulfonic acid solution was placed in an electrolytic cell, the anode was a zinc plate, and the cathode was made of a pure aluminum material of 1060 type, the plate spacing was 15 mm, and the duty cycle of the pulsed power source was 40%, a pulse frequency of 0.1 Hz, and a pulse current of 0.5 mA/cm ² were subjected to electrolysis at room temperature, and samples were taken for analysis at different times when the electrolysis reaction was carried out. After 10 minutes of electrolysis, the recovery of PFOS in the solution was 90.0% or more.

Example 8

The water-organic solvent mixed solution containing perfluorooctanoic acid is treated by electroflocculation.

A 500 mL, perfluorooctanoic acid concentration of 200 mg/L, a water-organic solvent mixed solution containing 5% by weight of isopropanol was placed in an electrolytic cell, the anode was a zinc plate, and the cathode was a titanium plate at a current density of 15 mA/ With cm ² and a plate spacing of 15 mm, electrolysis was carried out at room temperature using a DC power supply, and timed sampling analysis was performed. After 30 minutes of electrolytic reaction, the recovery of PFOA in the solution was 90.0% or more.

Example 9

A water-organic solvent mixed solution containing perfluorooctane sulfonic acid was treated by electrocoagulation.

A 500 mL, perfluorooctane sulfonic acid concentration of 500 μg / L, a water-organic solvent mixed solution containing 5% by weight of isopropanol was placed in an electrolytic cell, the anode was a zinc plate, and the cathode was a titanium plate. The current density was 10 mA/cm ² and the plate spacing was 10 mm. Electrolysis was carried out at room temperature using a DC power source, and timed sampling analysis was performed. After 10 minutes of electrolytic reaction, the recovery of PFOS in the solution was 85.0% or more.

Example 10

The perfluorobutanesulfonic acid (PFBS) solution was treated by electrocoagulation.

500 mL of a perfluorobutanesulfonic acid solution having a concentration of 200 mg/L was placed in an electrolytic cell, the anode was a zinc plate, and the cathode was a titanium plate under the conditions of a current density of 10 mA/cm ² and a plate spacing of 10 mm. Electrolysis was carried out at room temperature using a DC power source, and timed sampling analysis was performed. After 30 minutes of electrolytic reaction, the recovery of PFBS in the solution was 95.0% or more.

Example 11

The perfluorooctane sulfonyl fluoride (POSF) solution was treated by electrocoagulation.

500 mL of a concentration of 200 mg/L of perfluorooctane sulfonyl fluoride solution was placed in an electrolytic cell, the anode was a zinc plate, and the cathode was a titanium plate. The current density was 15 mA/cm ² and the plate spacing was 15 mm. Electrolysis was carried out at room temperature using a DC power supply, and timed sampling analysis was performed. After 30 minutes of electrolysis, the recovery of POSF in the solution was 98.0% or more.

Example 12

The solution of perfluorooctylethyl alcohol (8:2 FTOH) was treated by electrocoagulation.

500 mL of a concentration of 200 mg/L of perfluorooctylethyl alcohol solution was placed in an electrolytic cell, the anode was a zinc plate, and the cathode was a titanium plate. The current density was 15 mA/cm ² and the plate spacing was 10 mm. Electrolysis was carried out at room temperature using a DC power supply, and timed sampling analysis was performed. After 30 minutes of electrolytic reaction, the recovery of perfluorooctylethyl alcohol in the solution was 97.0% or more.

According to the invention, the concentration range is wide, and the perfluoro compound having a concentration of 1 μg/L to 100 g/L or even the above concentration in the solution can be effectively removed; the floc has the characteristics of large specific surface area and high activity, and therefore, has enhanced flocculation. The effect is fast, and the recovery rate of the perfluoro compound in the solution after the reaction for 30 minutes is 99.9% or more. The invention adopts the electroflocculation method, has the advantages of simple process flow, convenient operation, mild reaction condition, low energy consumption, good treatment effect, stable and reliable, and easy to realize industrial application; in addition, the sludge containing perfluoro compound produced is used. Harmless treatment, no need to add chemical reagents, and dewatering treatment of sludge at the same time as harmless treatment, the equipment required is simple, and it is easy to realize automatic operation. Meanwhile, Zn (OH) ₂ generated in situ flocs electrocoagulation adsorption capacity of the perfluoro compound is extremely high, fast adsorption rate can be recovered from the high and low concentration in the effluent concentration of perfluoro compound, while purifying waste water. Due to the low cost of electrocoagulation treatment and the small amount of sludge generated, large-scale application is completely economically feasible.

Claims

A method for recovering perfluorinated compounds from sewage, characterized in that the method comprises the following steps:

The electroflocculation step uses an electro-flocculation method to adsorb a perfluoro compound in an aqueous solution or a water-organic solvent mixture solution to form a sludge on the surface of the floc produced by electroflocculation;

In the elution step, the above-mentioned perfluoro compound-containing sludge is subjected to organic solvent elution treatment to separate the perfluoro compound from the sludge, and a concentrated perfluoro compound solution is formed;

In the distillation step, the produced perfluoro compound concentrate is distilled to obtain a perfluoro compound solid and a distillate, and the distillate is used as an eluent used in the above elution step.
The method for recovering a perfluoro compound from sewage according to claim 1, wherein the perfluoro compound has a mass concentration of 1 μg/L to 100 g/L in an aqueous solution or a water-organic solvent mixed solution.
The method for recovering a perfluoro compound from sewage according to claim 1, wherein the aqueous solution or the water-organic solvent mixed solution has a pH in the range of 3 to 11.
The method for recovering a perfluoro compound from sewage according to claim 1, wherein in the electroflocculation step, the anode material of the electrode is zinc and an alloy material thereof.
The method for recovering a perfluoro compound from sewage according to claim 1, wherein in the electroflocculation step, the electrolysis method is direct current electrolysis or pulse electrolysis.
The method for recovering a perfluoro compound from sewage according to claim 1, wherein the eluent is at least one organic solvent selected from the group consisting of isopropyl alcohol and ethanol.
The method for recovering a perfluoro compound from sewage according to claim 1, wherein the perfluoro compound is selected from the group consisting of perfluoroalkyl acids (salts) having 4 to 20 carbon atoms, and precursors thereof At least one compound in the body.
The method for recovering a perfluoro compound from sewage according to any one of claims 1 to 7, wherein the perfluoro compound is selected from the group consisting of perfluorooctanoic acid, perfluorooctane sulfonic acid, perfluorodecanoic acid, and perfluorocarbon. At least one of the above compounds of capric acid, perfluorooctanesulfonyl fluoride and perfluorooctylethyl alcohol.
A sewage treatment method by the recovery of perfluorination according to any one of claims 1-8 Method of implementation of the compound.
The sewage treatment method according to claim 9, wherein the water body comprises drinking water, surface water, ground water, and industrial sewage.