CN114477568B

CN114477568B - Method for recycling bromine-containing wastewater

Info

Publication number: CN114477568B
Application number: CN202011149981.8A
Authority: CN
Inventors: 王镭; 宋小飞; 钟林; 李建华; 安婷婷
Original assignee: Sinopec Beijing Research Institute of Chemical Industry; China Petroleum and Chemical Corp
Current assignee: Sinopec Beijing Research Institute of Chemical Industry; China Petroleum and Chemical Corp
Priority date: 2020-10-23
Filing date: 2020-10-23
Publication date: 2023-05-12
Anticipated expiration: 2040-10-23
Also published as: CN114477568A

Abstract

The invention relates to the technical field of environmental protection, and discloses a method for recycling bromine-containing wastewater, which comprises the following steps: (1) Pretreating bromine-containing wastewater to remove solid suspended matters in the bromine-containing wastewater; (2) Ultrafiltering the pretreated wastewater to remove colloid, macromolecular organic matters and microorganisms in the pretreated wastewater; (3) Performing reverse osmosis or sequentially performing reverse osmosis and electrodialysis on the filtrate obtained by ultrafiltration to obtain concentrated wastewater and purified water meeting the discharge standard or recycling standard; (4) And converting the bromide ions in the concentrated wastewater into bromine simple substances through electrolysis in an electrolytic tank, and simultaneously obtaining byproduct sodium hydroxide solution and hydrogen, wherein the electrolytic tank is an ion exchange membrane electrolytic tank. The invention can convert the bromine ions in the bromobutyl condensed wastewater into bromine simple substance and recycle the bromine simple substance, and simultaneously obtains produced water (purified water) meeting the requirement of circulating water and a small amount of wastewater which can be treated by a common sewage treatment plant.

Description

Method for recycling bromine-containing wastewater

Technical Field

The invention relates to the technical field of environmental protection, in particular to a method for recycling bromine-containing wastewater.

Background

Bromobutyl is a modified product of butyl rubber, which is produced by reacting butyl rubber with liquid bromine in a solution state. The basic process of producing brominated butyl rubber includes basic rubber production, sol, bromination reaction, neutralization, coagulation and drying. The liquid bromine reacts with butyl rubber to generate butyl bromide and byproduct hydrogen bromide, sodium bromide is generated in the glue solution after the byproduct hydrogen bromide is neutralized by sodium hydroxide solution, and when the glue solution is condensed by steam, the sodium bromide enters water in a condensation kettle to pollute condensation water. The condensed water is quantitatively discharged according to the balance principle of the material system to form bromine-containing salt sewage (namely bromine-containing wastewater) discharged from the butyl bromide device. As the effect of biochemical treatment is affected by the high concentration of bromine ions, the bromine-containing sewage cannot be directly discharged to a common sewage system for treatment. Bromine is needed to be separated out and then treated as common sewage.

At present, bromine-containing wastewater generated in the production process of brominated butyl rubber is mostly treated by a liquid-liquid extraction method (such as CN 103613071A) or membrane methods such as reverse osmosis and electrodialysis, but the methods have some problems. The liquid-liquid extraction method has large investment in equipment and very high running cost. The membrane method has the problem that concentrated wastewater is difficult to dispose.

Disclosure of Invention

The invention aims to solve the problem of difficult treatment of concentrated wastewater in the prior art, and provides a method for recycling bromine-containing wastewater.

In order to achieve the above object, the present invention provides a method for recycling bromine-containing wastewater, comprising the steps of:

(1) Pretreating bromine-containing wastewater to remove solid suspended matters in the bromine-containing wastewater;

(2) Ultrafiltering the pretreated wastewater to remove colloid, macromolecular organic matters and microorganisms in the pretreated wastewater;

(3) Performing reverse osmosis or sequentially performing reverse osmosis and electrodialysis on the filtrate obtained by ultrafiltration to obtain concentrated wastewater and purified water meeting the emission standard or the recycling standard, wherein the concentration of bromide ions in the concentrated wastewater is not lower than 10000mg/L;

(4) And converting the bromide ions in the concentrated wastewater into bromine simple substances through electrolysis in an electrolytic tank, and simultaneously obtaining a byproduct sodium hydroxide solution and hydrogen, wherein the electrolytic tank is an ion exchange membrane electrolytic tank.

Through the technical scheme, the method can convert the bromine ions in the bromobutyl coagulation wastewater into bromine simple substances and recycle the bromine simple substances, and meanwhile, the produced water (purified water) meeting the requirement of the circulating water is obtained.

Detailed Description

The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and are understood to encompass values approaching those ranges or values. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein.

The invention provides a method for recycling bromine-containing wastewater, which is characterized by comprising the following steps:

According to the present invention, in step (1), the pretreatment may include: at least one of grid filtration, gel separation treatment, flocculation precipitation, air floatation, sand filtration, active carbon filtration, filter cotton filtration and microfiltration. Preferably, the pretreatment includes sequentially performing: grid filtration, gel separation treatment, air floatation, flocculation precipitation, sand filtration and active carbon filtration.

Specifically, there is no particular requirement for the grid filtration, as long as large particle suspensions (particles having a particle diameter of more than 2 mm) of the wastewater species can be removed.

There is no particular requirement for the rubber barrier treatment, so long as rubber particles possibly present in the wastewater can be removed.

The conditions of the air flotation are not particularly limited as long as small particle suspended matters (particles having a particle diameter of 0.01 to 2 mm) in the wastewater can be removed.

There is no particular requirement for flocculation precipitation, and conventional flocculants such as polyaluminum chloride and/or polyacrylamide may be used.

The sand filtration can be performed by adopting quartz sand with the particle size of 0.5-1 mm.

The specific surface area of the activated carbon can be 800-1200m ² Activated carbon per gram.

By performing the pretreatment in the preferred manner described above, a portion of dissolved impurities, such as charged macromolecular organics, are removed while removing solid suspended matter from the bromine-containing wastewater.

According to the present invention, in the step (2), specific conditions for ultrafiltration are not particularly limited, and in order to more effectively remove colloid, macromolecular organic matters and microorganisms in the wastewater after pretreatment, it is preferable that the ultrafiltration membrane used for the ultrafiltration has a molecular weight cut-off of 60000-100000, an operation temperature of 0-40 ℃ and an operation pressure of 0.05-0.5MPa.

According to a preferred embodiment of the present invention, in step (3), the conditions of reverse osmosis include: the operating temperature is 0-40 ℃ and the operating pressure is 0.5-7MPa. The pore size of reverse osmosis membranes is typically 0.5-10nm.

According to a preferred embodiment of the invention, in step (3), the conditions of electrodialysis comprise: the membrane stack is formed by alternately forming homogeneous female membranes and homogeneous male membranes, the operating voltage is less than or equal to 250V, and the operating current is less than or equal to 100A.

According to a preferred embodiment of the present invention, in step (3), the conditions of reverse osmosis or reverse osmosis and electrodialysis are controlled so that the water quality of the concentrated wastewater is: the Chemical Oxygen Demand (COD) is less than or equal to 5000mg/L, the total organic matters (TOC) is less than or equal to 1000mg/L, the total dissolved solids (total dissolved solids, TDS) is less than or equal to 500000mg/L, the concentration of bromide ions is more than or equal to 10000mg/L, and the pH value is 4-11. More preferably, in the step (3), the conditions of reverse osmosis or reverse osmosis and electrodialysis are controlled so that the water quality of the concentrated wastewater is: the chemical oxygen demand is 200-2500mg/L, more preferably 300-900mg/L, the total organic matters are 200-1000mg/L, more preferably 250-300mg/L, the total dissolved solids are 25000-200000mg/L, more preferably 150000-180000mg/L, the concentration of bromine ions is 100000-150000mg/L, more preferably 116000-126000mg/L, and the pH value is 8-10, more preferably 9-9.75.

According to the present invention, the temperature of the bromine-containing wastewater to be treated may be high, typically above 70 ℃, and therefore, in order to maintain the operating temperature of step (2) or step (3) within a preferred range, the temperature of the wastewater may be lowered at the same time as or after the removal of the solid suspended matter in the bromine-containing wastewater in step (1).

According to the invention, in the step (4), the electrolytic tank is an ion exchange membrane electrolytic tank and mainly comprises an anode, a cathode, an ion exchange membrane, an electrolytic tank frame, a conductive copper rod and the like. There is no particular requirement on the number of unit cells of the electrolytic cell, but preferably the electrolytic cell is a two-compartment ion exchange membrane electrolytic cell or a three-compartment ion exchange membrane electrolytic cell. In the double-chamber ion exchange membrane electrolyzer, electrodialysis concentrate is introduced into an anode chamber, liquid bromine is obtained from the bottom of the anode chamber after electrolysis is finished, hydrogen is obtained from the upper part of a cathode chamber, and sodium hydroxide solution is obtained from the liquid in the cathode chamber. In the three-chamber ion exchange membrane electrolyzer, electrodialysis concentrate is introduced into an intermediate chamber, liquid bromine is obtained from the bottom of an anode chamber after electrolysis is finished, hydrogen is obtained from the upper part of a cathode chamber, sodium hydroxide solution is obtained from the liquid in the cathode chamber, wastewater containing sodium bromide with lower concentration is obtained from the intermediate chamber and is mixed with the original wastewater, and then the wastewater is returned to a pretreatment stage.

In order to obtain higher current efficiency, the membrane of the electrolytic cell is preferably an anion exchange membrane. Further preferably, the membrane of the electrolytic cell is a quaternary ammonium type anion exchange membrane.

According to the invention, in step (4), inert electrodes, such as carbon aerogel electrodes or graphite electrodes, are used for both the cathode and anode in the electrolytic cell.

According to a preferred embodiment of the present invention, in step (4), the conditions of electrolysis include: the temperature is 40-95deg.C, more preferably 45-55deg.C, the voltage is 1.1-1.5V, more preferably 1.2-1.4V, and the time is 60-120min, more preferably 80-100min.

According to the invention, the water quality of the sodium bromide wastewater can be: the chemical oxygen demand is 500-2000mg/L, preferably 930-1540mg/L, the total organic matter is 200-1000mg/L, preferably 270-340mg/L, the total dissolved solids is 5000-10000mg/L, preferably 6000-9260mg/L, the concentration of bromine ions is 3000-6000mg/L, preferably 3590-5530mg/L, and the pH value is 4-11, preferably 9-9.75. The present invention is particularly suitable for treating brominated butyl rubber coagulation waste water, and therefore, preferably, the sodium bromide waste water is brominated butyl rubber coagulation waste water.

The present invention will be described in detail by examples.

In the following examples, other water quality parameters except bromide ion concentration were tested according to the methods specified in GB3838-2002, quality Standard for surface Water environments;

the method for measuring the concentration of the bromide ions in the water by adopting the ion chromatography comprises the following specific steps: an aqueous solution containing 1.9mmol/L sodium carbonate and 3mmol/L sodium bicarbonate was used as a eluent, the flow rate of which was 0.8mL/min. Preparing sodium bromide solutions with the bromide concentrations of 1mg/L, 10mg/L, 20mg/L, 40mg/L, 60mg/L, 80mg/L and 100mg/L respectively, injecting the sodium bromide solutions into an ion chromatograph respectively to measure the peak areas of the bromide ions, and obtaining a standard curve through linear fitting by taking the bromide concentration as an abscissa and the peak areas as an ordinate. Filtering a water sample to be detected through a 0.45 mu m microporous filter membrane, injecting the filtered water sample into an ion chromatograph, measuring the peak area of bromide ions, and substituting the peak area into a standard curve equation to obtain the concentration of the bromide ions. If the concentration is more than 100mg/L, diluting the water sample by a certain multiple so that the concentration of the bromide ions after dilution is less than 100mg/L, measuring again, and multiplying the measured concentration of the bromide ions by the dilution multiple to obtain the concentration of the bromide ions of the water sample.

In the following examples, the amount of wastewater added, the yield of elemental bromine, and the current through the electrolytic cell were measured over a certain time t when the electrolytic reaction was stabilized, to calculate the yield of bromine and the current efficiency.

The bromine yield Y is calculated according to formula (I):

wherein m is _Br Yield of bromine per unit time (kg), m _w The input amount (kg) of the concentrated wastewater in unit time is represented by ρ, which is the density (kg/L) of the wastewater, and c, which is the concentration (mg/L) of bromide ions in the concentrated wastewater.

The current efficiency η is calculated according to formula (II):

wherein I is the current (A) through the cell, t is the time(s), M _NaOH The relative molecular mass (g/mol) of sodium hydroxide, F is the Faraday constant (C/mol). The final result is the average value.

Example 1

(1) The wastewater quality is shown in Table 1. The waste water 1 firstly enters a grid canal, is filtered by a coarse grid with a gap of 10mm and a fine grid with a gap of 2mm, then enters a rubber isolation pool, rubber particles in the water are scraped by a rotary scraping plate in the rubber isolation pool, then small particle suspended matters (particles with the particle size of 0.01-2 mm) are removed by an air floatation device, and then enters a buffer pool. The buffer pool is internally provided with a heat exchange pipe, and circulating water is communicated in the pipe to reduce the water temperature in the buffer pool to below 45 ℃. The water in the buffer tank was sent to a flocculation precipitation tank, and 800mg/L of polyaluminium chloride (polymerization) was addedAluminum chloride 28, purchased from the filter industry Co., ltd.) and 5mg/L polyacrylamide (molecular weight 800-2000, purchased from the filter industry Co., ltd.) were stirred for 8min, flocculated and precipitated for 25min, the precipitate was pumped out by a sludge pump, and the produced water was introduced into an intermediate pond through an overflow pipe. Pumping water in the middle water tank to a multimedia filter (containing quartz sand (particle diameter of 0.5-1 mm) and activated carbon (specific surface area of 1000 m) ² And/g)) are filtered in sequence and then enter the step (2).

(2) Pumping the produced water in the step (1) into a ultrafiltration system by using a centrifugal pump. By Ke' s

MP 8081-102 ultrafiltration membrane (molecular weight cut-off 100000), operating temperature 30deg.C, operating pressure 0.2MPa. And (3) returning the concentrated water to the buffer pool, and enabling the produced water to enter the step (3).

(3) Mixing the produced water in the step (2) and the fresh water in the step (4), pressurizing to 2MPa by a high-pressure pump, and delivering the mixture into a reverse osmosis system. Adopts a Heidel energy LFC3-LD reverse osmosis membrane. The reverse osmosis was operated at a temperature of 30 ℃. The water quality of the reverse osmosis produced water after the device is operated for 3 days is shown in table 2, and the water quality of the reverse osmosis produced water after the device is operated for 90 days is shown in table 3. And (4) introducing reverse osmosis concentrated water into the step (4).

(4) And (3) injecting the reverse osmosis concentrated water obtained in the step (3) into an electrodialysis system. The electrodialysis system adopts a tympany BTE high-efficiency concentration electrodialysis system. The ion exchange membrane is a membrane stack consisting of homogeneous phase positive membranes and homogeneous phase negative membranes alternately produced by Huntington's membrane technology development Co. The water is divided into two parts and is respectively put into a thick chamber and a thin chamber, the thick chamber is continuously supplemented with liquid under the premise of ensuring that the concentration is not lower than 2.5g/L, and the concentration of bromide ions in the thick chamber is concentrated to 116505mg/L and then the concentration is maintained. The current is controlled to 80-100A by adjusting the voltage at the beginning of the electrodialysis operation, and as the electrodialysis proceeds, the voltage can be raised to maintain the current, but at most 250V must not be exceeded. The concentrated water enters the step (5), and the fresh water returns to the step (3). The electrodialysis concentrate quality is shown in Table 4.

(5) And (3) injecting the electrodialysis concentrated water obtained in the step (4) into an electrolytic tank for electrolysis. The electrolytic tank is a double-chamber ion exchange membrane electrolytic tank, the diaphragm is an anion exchange membrane (A41 negative membrane, purchased from golden autumn environmental protection water treatment Co., ltd.), the cathode and the anode are both carbon aerogel electrodes, the voltage is 1.3V, the time is 90min, and the electrolytic temperature is 50 ℃. The liquid bromine produced was taken from the bottom of the anode chamber, hydrogen gas was taken from the top of the cathode chamber, and sodium hydroxide solution was obtained from the cathode chamber liquid. Bromine yields and current efficiencies were calculated as shown in table 5.

Example 2

The wastewater 2 was treated in the same manner as in example 1.

Example 3

The treatment was carried out in the same manner as in example 1, except that the concentration of bromide ions in the electrodialysis concentration cell was controlled to be in the range of 139806mg/L in step (4).

Example 4

The treatment was carried out in the same manner as in example 1, except that the reverse osmosis system in step (3) was carried out in two stages. The operation pressure of the first stage is 5MPa, the produced water of the first stage enters the second stage reverse osmosis, the concentrated water directly enters the step (5) and the step (4) is omitted, and the water quality of the concentrated water is shown in the table 4; the operating pressure of the second stage is 2MPa, the concentrated water of the second stage returns to the first stage reverse osmosis, the water quality of the produced water after the device is operated for 3 days is shown in a table 2, and the water quality of the produced water after the device is operated for 90 days is shown in a table 3.

Example 5

The treatment was carried out in the same manner as in example 1, except that DuPont Integrated Flux was used in step (2) ^TM SFP-2880XP ultrafiltration membrane (molecular weight cut-off is 100000), and east TML reverse osmosis membrane is adopted in step (3).

Example 6

The treatment was carried out in the same manner as in example 1, except that the interelectrode voltage in step (5) was 1.2V.

Example 7

The treatment was carried out in the same manner as in example 1, except that the interelectrode voltage in step (5) was 1.4V.

Example 8

The same procedure as in example 1 was followed except that in step (5) the electrolytic cell was a three-compartment ion exchange membrane electrolytic cell, the electrodialysis concentrate was introduced into the intermediate compartment, liquid bromine was obtained from the bottom of the anode compartment after the electrolysis was completed, hydrogen was obtained from above the cathode compartment, sodium hydroxide solution was obtained from the cathode compartment liquid, wastewater containing sodium bromide at a relatively low concentration was obtained from the intermediate compartment and was mixed with the wastewater before being returned to the flocculation precipitation of step (1), and the treatment was continued.

Example 9

The same procedure as in example 1 was followed, except that the cell gap voltage was 1.6V.

Example 10

The same procedure as in example 1 was followed, except that the anode of the electrolytic cell was an iridium-plated titanium plate and the cathode was a stainless steel plate.

Example 11

The same procedure as in example 1 was followed, except that the membrane of the cell was a cation exchange membrane (CMB, available from ASTOM).

Example 12

The same procedure as in example 1 was followed, except that the wastewater was not subjected to heat exchange and temperature reduction before entering step (2). As a result, the reverse osmosis membrane was destroyed after 7 days of operation.

Comparative example 1

The same procedure as in example 1 was followed except that the cell was a homogeneous membrane cell (membrane was a ceramic membrane available from NIKKATO Co.).

TABLE 1

TABLE 2

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TABLE 3 Table 3

TABLE 4 Table 4

TABLE 5

Examples numbering	Bromine yield (%)	Current efficiency (%)
			Example 1	93.6	80.3
Example 2	94.2	80.5
			Example 3	94.8	83.2
Example 4	94.6	74.3
			Example 5	92.3	79.6
Example 6	96.2	78.1
			Example 7	94.5	81.6
Example 8	93.4	79.1
			Example 9	92.1	65.8
Example 10	86.5	67.2
			Example 11	89.5	65.5
Example 12	82.6	65.9
			Comparative example 1	55.6	48.6

From the results, the embodiment of the method disclosed by the invention is used for treating the brominated butyl rubber coagulation wastewater, so that the produced water has good quality, can be used as process water or circulating water for recycling, can realize recycling of concentrated wastewater, and has good yield.

The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, a number of simple variants of the technical solution of the invention are possible, including combinations of the individual technical features in any other suitable way, which simple variants and combinations should likewise be regarded as being disclosed by the invention, all falling within the scope of protection of the invention.

Claims

1. A method for recycling bromine-containing wastewater, which is characterized by comprising the following steps:

the bromine-containing wastewater is brominated butyl rubber coagulation wastewater;

wherein in the step (2), the molecular weight cut-off of an ultrafiltration membrane used for ultrafiltration is 60000-100000, the operating temperature is 0-40 ℃, and the operating pressure is 0.05-0.5MPa;

(4) Converting bromide ions in the concentrated wastewater into bromine simple substances through electrolysis in an electrolytic tank, and simultaneously obtaining byproduct sodium hydroxide solution and hydrogen, wherein the electrolytic tank is an ion exchange membrane electrolytic tank;

the electrolytic tank is a double-chamber ion exchange membrane electrolytic tank or a three-chamber ion exchange membrane electrolytic tank;

the diaphragm of the electrolytic cell is a quaternary ammonium type anion exchange membrane;

in step (4), the conditions of the electrolysis include: the temperature is 45-55deg.C, the voltage is 1.2-1.4V, and the time is 80-100min.

2. The method of claim 1, wherein in step (1), the pretreatment mode includes: at least one of grid filtration, gel separation treatment, flocculation precipitation, air floatation, sand filtration, active carbon filtration, filter cotton filtration and microfiltration.

3. The method of claim 1, wherein in step (3), the conditions of reverse osmosis comprise: the operating temperature is 0-40 ℃ and the operating pressure is 0.5-7MPa.

4. The method of claim 1, wherein in step (3), the electrodialysis conditions comprise: the membrane stack is formed by alternately forming homogeneous female membranes and homogeneous male membranes, the operating voltage is less than or equal to 250V, and the operating current is less than or equal to 100A.

5. The method of claim 1, wherein,

in the step (3), the water quality of the concentrated wastewater is as follows: the chemical oxygen demand is 200-2500mg/L, the total organic matter is 200-1000mg/L, the total dissolved solids is 25000-200000mg/L, the concentration of bromine ions is 100000-150000mg/L, and the pH value is 8-10.

6. The method according to claim 1 or 5, wherein in step (3), the water quality of the concentrated wastewater is: the chemical oxygen demand is 300-900mg/L;

and/or, in the step (3), the water quality of the concentrated wastewater is: the total organic matter is 250-300mg/L;

and/or, in the step (3), the water quality of the concentrated wastewater is: the total dissolved solid is 150000-180000mg/L;

and/or, in the step (3), the water quality of the concentrated wastewater is: the concentration of bromide ion is 116000-126000mg/L;

and/or, in the step (3), the water quality of the concentrated wastewater is: the pH value is 9-9.75.

7. The method of claim 1, wherein in step (4), both the cathode and anode of the electrolysis employ inert electrodes.

8. The method of claim 1 or 7, wherein in step (4), both the cathode and anode of the electrolysis employ carbon aerogel electrodes or graphite electrodes.

9. The method of claim 1, wherein the bromine-containing wastewater has a water quality of: the chemical oxygen demand is 500-2000mg/L, the total organic matter is 200-1000mg/L, the total dissolved solids is 5000-10000mg/L, the concentration of bromine ions is 3000-6000mg/L, and the pH value is 4-11.

10. The method of claim 9, wherein the bromine-containing wastewater has a water quality of: the chemical oxygen demand is 930-1540mg/L;

and/or, the water quality of the bromine-containing wastewater is: the total organic matter is 270-340mg/L;

and/or, the water quality of the bromine-containing wastewater is: the total dissolved solid is 6000-9260mg/L;

and/or, the water quality of the bromine-containing wastewater is: the concentration of the bromide ion is 3590-5530mg/L;

and/or, the water quality of the bromine-containing wastewater is: the pH value is 9-9.75.