CN114477568A

CN114477568A - Method for recycling bromine-containing wastewater

Info

Publication number: CN114477568A
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: 2022-05-13
Anticipated expiration: 2040-10-23
Also published as: CN114477568B

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 suspended solids in the bromine-containing wastewater; (2) performing ultrafiltration on the pretreated wastewater to remove colloids, 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 reuse standard; (4) converting bromine ions in the concentrated wastewater into bromine simple substance by electrolysis in an electrolytic cell, and simultaneously obtaining by-products of sodium hydroxide solution and hydrogen, wherein the electrolytic cell is an ion exchange membrane electrolytic cell. The invention can convert the bromide ions in the butyl bromide coagulation wastewater into bromine and recycle the bromine, and simultaneously obtain the 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

The brominated butyl is a modified product of butyl rubber and is generated by reacting butyl rubber with liquid bromine in a solution state. The basic process for producing the brominated butyl rubber comprises base rubber production, sol, bromination reaction, neutralization, condensation and drying. Butyl bromide and a byproduct hydrogen bromide are generated in the reaction process of liquid bromine and butyl rubber, sodium bromide is generated after the byproduct hydrogen bromide is neutralized by using a sodium hydroxide solution and exists in a glue solution, and when the glue solution is condensed by using steam, the sodium bromide enters water in a condensation kettle to pollute condensed water. The condensed water is quantitatively discharged according to the balance principle of a material system to form the bromine salt-containing sewage (namely bromine-containing wastewater) discharged by the bromobutyl device. Because the effect of biochemical treatment can be influenced by the bromide ions with higher concentration, the bromine-containing sewage can not be directly discharged into a common sewage system for treatment. The bromine needs to be separated out and then treated as ordinary sewage.

At present, bromine-containing waste water generated in the production process of brominated butyl rubber is treated by liquid-liquid extraction methods (such as CN103613071A) or membrane methods such as reverse osmosis, electrodialysis and the like, but the methods have some problems. The liquid-liquid extraction method has large investment and very high operation cost. The membrane method has a problem that the concentrated wastewater is difficult to dispose.

Disclosure of Invention

The invention aims to overcome the problem of difficult treatment of concentrated wastewater in the prior art and provide 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) performing ultrafiltration on the pretreated wastewater to remove colloids, 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 reuse standard, wherein the concentration of bromide ions in the concentrated wastewater is not lower than 10000 mg/L;

(4) converting bromide ions in the concentrated wastewater into elemental bromine through electrolysis in an electrolytic cell, and simultaneously obtaining by-products of sodium hydroxide solution and hydrogen, wherein the electrolytic cell is an ion exchange membrane electrolytic cell.

Through the technical scheme, bromide ions in the butyl bromide coagulation wastewater can be converted into elemental bromine and recycled, and water (purified water) meeting the requirement of circulating water is obtained.

Detailed Description

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For numerical ranges, each range between its endpoints and individual point values, and each individual point value can be combined with each other to give one or more new numerical ranges, and such numerical ranges should be construed 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 the step (1), the pretreatment may include: at least one of grid filtration, glue separation treatment, flocculation and precipitation, air flotation, sand filtration, activated carbon filtration, filter cotton filtration and microfiltration. Preferably, the pretreatment comprises sequentially performing: grid filtration, glue separation treatment, air flotation, flocculation precipitation, sand filtration and active carbon filtration.

Specifically, there is no particular requirement for the grid filtration as long as it is capable of removing large-particle suspended matter (particles having a particle size of more than 2 mm) of the wastewater species.

There is no particular requirement for the rubber-separating treatment, so long as it is capable of removing rubber particles that may be present in the wastewater.

The conditions of the air flotation are not particularly limited as long as it is possible to remove suspended small particles (particles having a particle diameter of 0.01 to 2 mm) in the wastewater.

The flocculation is not particularly critical and can be carried out using conventional flocculating agents, such as polyaluminium chloride and/or polyacrylamide.

The sand filtration can adopt quartz sand with the grain diameter of 0.5-1 mm.

The activated carbon filtration can adopt the specific surface area of 800-²Per gram of activated carbon.

By adopting the above preferred mode for pretreatment, while removing solid suspended matters in the bromine-containing wastewater, a part of dissolved impurities such as charged macromolecular organic matters are removed.

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

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

According to a preferred embodiment of the present invention, in step (3), the conditions of the electrodialysis include: the membrane stack is formed by alternating homogeneous negative membranes and positive 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 the step (3), the conditions of reverse osmosis or reverse osmosis and electrodialysis are controlled such that the quality of the concentrated wastewater is: chemical Oxygen Demand (COD) is less than or equal to 5000mg/L, total organic matter (TOC) is less than or equal to 1000mg/L, total dissolved solids (total dissolved solids, TDS) is less than or equal to 500000mg/L, bromide ion concentration is more than or equal to 10000mg/L, and pH value is 4-11. More preferably, in the step (3), the conditions of reverse osmosis or reverse osmosis and electrodialysis are controlled in sequence 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 matter is 200-1000mg/L, more preferably 250-300mg/L, the total dissolved solid is 25000-200000mg/L, more preferably 150000-180000mg/L, the bromide ion concentration is 100000-150000mg/L, more preferably 116000-126000mg/L, 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, generally above 70 ℃, and therefore, in order to maintain the operation temperature of step (2) or step (3) within the preferred range, the temperature of the wastewater may be lowered simultaneously with 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 cell is an ion exchange membrane electrolytic cell which mainly comprises an anode, a cathode, an ion exchange membrane, an electrolytic cell frame, a conductive copper bar and the like. The number of the unit cells of the electrolytic cell is not particularly required, but preferably, the electrolytic cell is a two-compartment ion exchange membrane electrolytic cell or a three-compartment ion exchange membrane electrolytic cell. For the double-chamber ion exchange membrane electrolytic cell, electrodialysis concentrated water is introduced into the anode chamber, liquid bromine is taken from the bottom of the anode chamber after electrolysis is finished, hydrogen is taken from the upper part of the cathode chamber, and sodium hydroxide solution is taken from the liquid in the cathode chamber. For a three-chamber ion exchange membrane electrolytic cell, electrodialytic concentrated water 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, a sodium hydroxide solution is obtained from cathode chamber liquid, and waste water containing sodium bromide with lower concentration is obtained from the intermediate chamber and is mixed with original waste water to return to a pretreatment stage.

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

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

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

According to the invention, the water quality of the sodium bromide wastewater can be as follows: 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 solid is 5000-10000mg/L, preferably 6000-9260mg/L, the bromine ion concentration is 3000-6000mg/L, preferably 3590-5530mg/L, the pH value is 4-11, preferably 9-9.75. The method is particularly suitable for treating the waste water generated by coagulating the brominated butyl rubber, and therefore, preferably, the sodium bromide waste water is the waste water generated by coagulating the brominated butyl rubber.

The present invention will be described in detail below by way of examples.

In the following examples, water quality parameters other than bromide ion concentration were measured according to the method specified in GB3838-2002 "environmental quality Standard for surface Water";

the method for measuring the concentration of bromide ions in water by adopting ion chromatography comprises the following specific steps: an aqueous solution containing 1.9mmol/L sodium carbonate and 3mmol/L sodium bicarbonate was used as the eluent at a flow rate of 0.8 mL/min. Preparing sodium bromide solutions with bromide ion concentrations of 1mg/L, 10mg/L, 20mg/L, 40mg/L, 60mg/L, 80mg/L and 100mg/L respectively, injecting the solutions into an ion chromatograph to measure the peak area of bromide ions respectively, and obtaining a standard curve through linear fitting by taking the bromide ion concentration as a horizontal coordinate and the peak area as a vertical coordinate. And (3) filtering a water sample to be detected through a 0.45-micron 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 bromide ion concentration. And if the concentration is more than 100mg/L, diluting the water sample by a certain multiple, measuring the diluted bromide ion concentration again after the diluted bromide ion concentration is less than 100mg/L, and multiplying the measured bromide ion concentration by the dilution multiple to obtain the bromide ion concentration of the water sample.

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

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

wherein m is_BrIs the yield of bromine per unit time (kg), m_wThe input amount (kg) of the concentrated wastewater in unit time is defined as ρ the density (kg/L) of the wastewater, and c is the concentration (mg/L) of bromide ions in the concentrated wastewater.

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

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

Example 1

(1) The wastewater quality is shown in Table 1. Waste water 1 firstly enters a grid channel, is filtered by a coarse grid with a gap of 10mm and a fine grid with a gap of 2mm, then enters a glue separating tank, a rotating scraper blade in the glue separating tank scrapes away rubber particles in water, then enters an air floatation device to remove small particle suspended matters (particles with the particle diameter of 0.01-2 mm), and finally enters a buffer tank. The heat exchange pipe is arranged in the buffer pool, and circulating water is introduced into the pipe to reduce the temperature of water in the buffer pool to below 45 ℃. Sending the water in the buffer tank to a flocculation sedimentation tank, adding 800mg/L of polyaluminium chloride (polyaluminium chloride 28, available from filter material industry Co., Ltd., Highuai) and 5mg/L of polyaluminium chloridePolyacrylamide (molecular weight 800-. Pumping the water in the intermediate water tank to a multi-media filter (containing quartz sand (with particle size of 0.5-1mm) and activated carbon (with specific surface area of 1000 m)²/g)) are filtered in sequence and then enter the step (2).

(2) Pumping the produced water in the step (1) into an ultrafiltration system by using a centrifugal pump. By means of Coriolis

MP 8081-102 ultrafiltration membrane (molecular weight cutoff is 100000), the operation temperature is 30 ℃, and the operation pressure is 0.2 MPa. Returning the concentrated water to the buffer pool, and making the produced water enter the step (3).

(3) And (3) mixing the produced water in the step (2) with the fresh water in the step (4), pressurizing to 2MPa through a high-pressure pump, and sending into a reverse osmosis system. The Heideneng LFC3-LD reverse osmosis membrane is adopted. The operating temperature for reverse osmosis was 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) feeding reverse osmosis concentrated water into the step (4).

(4) And (4) injecting the reverse osmosis concentrated water obtained in the step (3) into an electrodialysis system. The electrodialysis system adopts a Tingrun BTE high-efficiency concentration electrodialysis system. The ion exchange membrane is a membrane stack which is produced by Tingrun membrane technology development corporation and consists of homogeneous positive membranes and homogeneous negative membranes alternately. Dividing the inlet water into two parts, respectively placing the two parts into a concentration chamber, continuously replenishing the solution in the dilution chamber on the premise of ensuring the concentration to be not lower than 2.5g/L, and replenishing the solution to maintain the concentration after the concentration of the bromide ions in the concentration chamber is concentrated to 116505 mg/L. The current is controlled to 80-100A by adjusting the voltage in the initial period of electrodialysis operation, and the voltage can be increased to maintain the current as the current decreases, but not more than 250V at most. And (5) enabling the concentrated water to enter the step (5), and returning the fresh water to the step (3). The quality of the electrodialysis concentrate is shown in Table 4.

(5) And (4) injecting the electrodialysis concentrated water in the step (4) into an electrolytic bath for electrolysis. The electrolytic cell is a double-chamber ion exchange membrane electrolytic cell, the diaphragm is an anion exchange membrane (A41 cathode membrane, purchased from 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 electrolysis temperature is 50 ℃. The generated liquid bromine is taken from the bottom of the anode chamber, the hydrogen is taken from the top of the cathode chamber, and the sodium hydroxide solution is obtained from the cathode chamber liquid. The bromine yield and current efficiency were calculated and are shown in table 5.

Example 2

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 compartment was controlled 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) employed two-stage reverse osmosis. The operating 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 quality of the concentrated water is shown in a table 4; the operating pressure of the second stage is 2MPa, the concentrated water of the second stage returns to the reverse osmosis of the first stage, the water quality of the produced water after the device operates for 3 days is shown in a table 2, and the water quality of the produced water after the device operates for 90 days is shown in a table 3.

Example 5

The same procedure as in example 1 was conducted, except that DuPont IntegraFlux was used in the step (2)^TMSFP-2880XP ultrafiltration membrane (with the molecular weight cutoff of 100000) and Dongli TML reverse osmosis membrane is adopted in the step (3).

Example 6

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

Example 7

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

Example 8

The treatment was carried out in the same manner as in example 1 except that the electrolytic bath in step (5) was a three-compartment ion exchange membrane electrolytic bath, the electrodialyzed concentrated water was passed through an intermediate compartment, liquid bromine was taken from the bottom of the anode compartment after completion of the electrolysis, hydrogen gas was taken from the upper side of the cathode compartment, a sodium hydroxide solution was taken from the liquid in the cathode compartment, and the wastewater containing sodium bromide at a lower concentration was taken from the intermediate compartment and returned to the step (1) before the flocculation and precipitation and then mixed with the wastewater for further treatment.

Example 9

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

Example 10

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

Example 11

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

Example 12

The same treatment as in example 1 was carried out except that the wastewater was not subjected to heat exchange for 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 electrolytic cell was a uniform-membrane electrolytic cell (the separator was a ceramic separator and was obtained from NIKKATO Co., Ltd.).

TABLE 1

TABLE 2

TABLE 3

TABLE 4

TABLE 5

Example 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

The results show that the treatment of the butyl bromide rubber coagulation wastewater by adopting the embodiment of the method of the invention has good water quality of produced water, can be used as process water or circulating water for recycling, can realize resource utilization of concentrated wastewater and has good yield.

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.

Claims

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

2. The method according to claim 1, wherein in step (1), the preprocessing comprises: at least one of grid filtration, glue separation treatment, flocculation precipitation, air flotation, sand filtration, activated carbon filtration, cotton filtration and microfiltration.

3. The method as claimed in claim 1, wherein, in step (2), the ultrafiltration membrane used in the ultrafiltration has a molecular weight cut-off of 60000-100000, an operating temperature of 0-40 ℃ and an operating pressure of 0.05-0.5 MPa.

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

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

6. The method as claimed in claim 1, wherein in the step (3), the quality of the concentrated wastewater is: the chemical oxygen demand is less than or equal to 5000mg/L, the total organic matter is less than or equal to 1000mg/L, the total dissolved solid is less than or equal to 500000mg/L, and the pH value is 4-11;

in the step (3), the water quality of the concentrated wastewater is as follows: the chemical oxygen demand is 200-2500mg/L, preferably 300-900mg/L, the total organic matter is 200-1000mg/L, preferably 250-300mg/L, the total dissolved solid is 25000-200000mg/L, preferably 150000-180000mg/L, the bromine ion concentration is 100000-150000mg/L, preferably 116000-126000mg/L, and the pH value is 8-10, preferably 9-9.75.

7. The process of claim 1, wherein in step (4), the electrolyzer is a two-compartment ion exchange membrane electrolyzer or a three-compartment ion exchange membrane electrolyzer;

preferably, the diaphragm of the electrolytic cell is an anion exchange membrane;

more preferably, the diaphragm of the electrolytic cell is a quaternary ammonium type anion exchange membrane.

8. The method of claim 1, wherein in step (4), inert electrodes, preferably carbon aerogel electrodes or graphite electrodes, are used as the cathode and the anode of the electrolysis.

9. The method of claim 1, wherein in step (4), the conditions of the electrolysis comprise: the temperature is 40-95 deg.C, preferably 45-55 deg.C, the voltage is 1.1-1.5V, preferably 1.2-1.4V, and the time is 60-120min, preferably 80-100 min.

10. The method of claim 1, wherein the bromine-containing wastewater has a water quality of: 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 solid is 5000-10000mg/L, preferably 6000-9260mg/L, the bromine ion concentration is 3000-6000mg/L, preferably 3590-5530mg/L, the pH value is 4-11, preferably 9-9.75;

preferably, the sodium bromide wastewater is brominated butyl rubber coagulation wastewater.