CN111875009B - Method for treating nitrate radical in industrial wastewater - Google Patents
Method for treating nitrate radical in industrial wastewater Download PDFInfo
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Abstract
The invention belongs to the technical field of wastewater treatment, and particularly relates to a method for treating nitrate radicals in industrial wastewater. The treatment unit for nitrate radical in industrial wastewater is composed of at least one adsorption unit; the adsorption unit comprises a fixed plate, an adsorption polar plate and an induction titanium wire mesh electrode; an induction titanium wire mesh electrode is arranged between the two fixing plates, and adsorption polar plates are respectively arranged on two sides of the induction titanium wire mesh electrode. The treatment method is characterized in that anions such as nitrate radical and the like in the wastewater are adsorbed and removed in the electric field environment of the treatment unit. The treatment method is suitable for removing nitrate radicals in production wastewater in the electroplating industry, the pesticide industry, the fertilizer manufacturing industry, the electronic component production industry and other industries, the removal rate of the nitrate radicals is more than or equal to 75 percent, and meanwhile, a plurality of anions such as the nitrate radicals, fluoride ions, chloride ions and the like in the wastewater are removed; effectively reduces nitrate radical, salt and conductivity of the wastewater.
Description
Technical Field
The invention belongs to the technical field of wastewater treatment, and particularly relates to a method for treating nitrate radicals in industrial wastewater.
Background
The electroplating industry, the pesticide industry, the fertilizer manufacturing industry, the electronic component production industry and other industries can generate a large amount of nitrate-containing wastewater. Nitrate content in natural surface water is generally lower than 1 mu mol/L, and in recent years, nitrate pollution in underground water and surface water is attracting attention all over the world. Nitric acidSalts are very soluble in water and too high a nitrate concentration can pose a serious threat to human health. Nitrate has a plurality of hazards to human health, nitrate taken into a body can be converted into nitrosamine with carcinogenicity in stomach, nitrate can also oxidize hemoglobin in blood into methemoglobin, the oxygen carrying capacity of red blood cells is reduced, the methemoglobin and oxygen are irreversibly combined to cause methemoglobinemia, and hypoxia death can be caused in serious cases. And the ammonium nitrite and the like formed in the nitrate conversion process also have the harmful effects of carcinogenesis, teratogenesis, genogenesis mutation and the like. Too much nitrate also has some effect on the growth of crops. The phenomena of eutrophication, water aging and the like caused by the over-high nitrogen content in the environmental water body also bring about serious ecological influence. At present, the first-grade A discharge standard of sewage put forward at the national level makes the comprehensive upgrading and reconstruction work of sewage treatment plants in China more urgent, wherein, NO with too high concentration 3 - the-N becomes an important factor for restricting the standard reaching of the TN.
At present, the nitrate is removed from water by biological denitrification, reverse osmosis, chemical reduction, electrodialysis, ion exchange, evaporative concentration, etc. At present, the methods for carrying out denitration treatment on the nitric acid-containing wastewater mainly comprise a biological denitrification method, a chemical reduction method, a neutralization method and the like. The most widely used method is the biological denitrification method, which utilizes the denitrification of denitrifying bacteria to reduce nitrate nitrogen into nitrogen gas which is released into the atmosphere. However, due to the limitations of slow growth speed of denitrifying bacteria, low denitrifying efficiency, narrow tolerance range of pH and the like, the method cannot treat high-concentration nitric acid-containing wastewater, needs a large amount of water for dilution, occupies a large area, and causes high wastewater treatment cost. Rivett et al have studied that nitrate in water can be chemically reduced to ammonia at alkaline pH, the reaction being carried out under the action of Cu catalyst, and have shown that this process is difficult to put into practical use due to the high cost. Wang et al developed a process for the selective removal of nitrate using electrodialysis techniques. The method can reduce the nitrate concentration from 50mg/L to below 25mg/L, and does not need to add any chemical reagent. However, this method is difficult to handle nitrate at high concentrations. Shin et alNitrate is removed by a cellulose acetate membrane reverse osmosis system, when the concentration of the nitrate in the inlet water is 18-25 mg/L, the continuous operation is carried out for 1 000h, and the nitrate removal rate reaches 65%. The method has low treatment efficiency and high operation cost, and is difficult to popularize in actual production. Wang et al developed a method for removing nitrite and nitrate from drinking water. The result shows that the method can be carried out under the conditions that the temperature is 10 ℃ and the pH value is 6-8, the process is easy to automatically control, and the method is suitable for a small water treatment system. However, the process is still in the research stage, and many factors such as kinetic parameters, long-term stability of the catalyst and the like need to be further researched. The principle of removing nitrate by the ion exchange method is that NO in solution 3 - By reaction with Cl on ion exchange resin － Or HCO 3 - Exchange is carried out to remove the organic matters, and the industrial wastewater contains a large amount of organic matters, so that the resin is blocked, and the use and regeneration of the resin are influenced. Meanwhile, the evaporation concentration technology is suitable for high-concentration and high-salt-content wastewater, but the energy consumption is higher.
Chinese patent CN111115661A discloses a treatment system and a treatment method for nitric acid wastewater. The system comprises a quality separation unit, a steam stripping unit, a biochemical treatment unit and a concentrated salt treatment unit. Separating the nitric acid wastewater into inorganic wastewater and organic wastewater, and then further performing quality-grading treatment; however, the method mainly highlights a water distribution management route, adopts a biochemical method to treat the nitrate wastewater, and the treatment effect is influenced by various factors such as the concentration of the nitrate and the carbon-nitrogen ratio in the wastewater, so that the treatment process is initiated at home and abroad, and no report is found in domestic and foreign documents and patent searches.
Disclosure of Invention
The invention provides a method for treating nitrate radical in industrial wastewater, aiming at controlling ecological environment pollution caused by nitrate radical and solving the practical problem that total nitrogen index caused by nitrate radical is difficult to reach the standard and discharge.
In order to achieve the purpose, the invention adopts the technical scheme that:
a treatment unit for nitrate radical in industrial wastewater, which consists of at least one adsorption unit;
the adsorption unit comprises a fixed plate 1, an adsorption polar plate 2 and an induction titanium wire mesh electrode 5;
an induction titanium wire mesh electrode is arranged between the two fixing plates, and adsorption polar plates are respectively arranged on two sides of the induction titanium wire mesh electrode.
An insulating net is arranged between the induction titanium wire mesh electrode and the adsorption polar plate on one side; the distance between two adsorption pole plates in the adsorption unit is 12-20mm.
The adsorption units are connected through hoses; the lower end of a fixing plate at one side of each adsorption unit is provided with a water inlet, and a fixing plate at the other side is provided with a water outlet;
the adsorption polar plate is sealed on the fixing plate through an insulating rubber ring; the adsorption plate is connected with an external direct current voltage and current stabilizing power supply through a lead.
The adsorption polar plate is formed by coating a titanium-based nano aluminum oxide composite graphite powder coating liquid on one side of a substrate to form an adsorption layer; wherein the thickness of the adsorption layer is 8-10 microns.
The side of the two adsorption pole plates, which forms the adsorption layer, is arranged oppositely, and the side of the two adsorption pole plates, which does not form the adsorption layer, is sealed on the fixing plate through the insulating rubber ring respectively.
A treatment unit is used for treating the nitrate radical in the industrial wastewater, and the wastewater containing the nitrate radical is sequentially treated by the treatment unit under the environment of an electric field through an adsorption unit component, so that the nitrate radical, chloride ions and fluoride ions are removed, the removal of the nitrate radical ions in the wastewater is realized, and the total nitrogen and salt content in the wastewater is reduced.
The environment of the electric field is that the current density is 10-40 mA/cm < 2 >, and the adsorption time is 60-120 min.
Further, corresponding current and flow rate are selected according to the conductivity of the wastewater to be treated and the concentration of nitrate radicals, a peristaltic pump is started to fill the system with the solution, a power supply is started after air is exhausted, the conductivity change of the solution is monitored, adsorption treatment is carried out, and effluent after the adsorption treatment is collected.
The processing unit after the wastewater treatment exchanges the positive and negative electrodes of the external current connected with the processing unit, and the current density is 30～40mA/cm 2 And the regeneration treatment can be realized after the treatment is carried out for 20-60 min.
Furthermore, the adsorption pole plate is used for multiple periods, the adsorption effect is reduced, and the pole plate needs to be regenerated in order to ensure the technical economy. And exchanging the anode and the cathode of the polar plate, performing desorption reaction, and independently collecting the high-nitrate concentrated solution generated in the regeneration process. If the concentrated solution has a single composition, the resource utilization requirement is met, and the resource utilization is preferably considered. If the concentrated solution can not meet the resource utilization requirement, the concentrated solution can be evaporated and concentrated with the high-salt-content waste liquid for disposal.
The adsorption polar plate is formed by coating a nano aluminum oxide composite graphite powder coating liquid on one side of a substrate to form an adsorption layer; wherein the thickness of the adsorption layer is 8-10 microns.
Further, the method comprises the following steps:
1) Preparing a glue mixed solution: mixing carbon black conductive adhesive and isopropanol solution according to a mass ratio of 1:1, mixing and fully dissolving;
2) Preparation of coating liquid: adding a mixed solution of nano-graphite powder and nano-aluminum oxide powder into the glue mixed solution, and uniformly mixing after adding, wherein the mixed solution is a coating solution when the mixed solution is in a turbid liquid state; wherein the mixing mass ratio of the nano graphite powder to the nano aluminum oxide powder is 5:1 to 10:1, the mass ratio of the coating liquid to the glue mixed liquid is 20:1 to 30:1.
and adding the mixed solution of the nano-scale graphite powder and the nano-scale aluminum trioxide powder into the glue mixed solution in batches, and fully and uniformly mixing after each addition.
The coating liquid is uniformly coated on one side of the substrate, the substrate is baked for 30min under an infrared lamp every coating, after 15-20 times of coating and baking of the infrared lamp, the substrate is dried in an oven at 120-150 ℃ for 1h.
And after cleaning the substrate, performing acid etching treatment by using mixed solution of oxalic acid and hydrochloric acid for later use.
Furthermore, the coating method is used for preparing the titanium-based nano aluminum oxide composite graphite powder
Attaching a polar plate:
1. treatment of titanium plates
1) The titanium plate is selected as the base material of the adsorption polar plate, the purity of the titanium plate is more than or equal to 99.9 percent, and the titanium plate is cleaned by ultrasonic waves through mixed liquid of acetone and carbon tetrachloride. The mass ratio of acetone to carbon tetrachloride in the cleaning mixed solution is 2:1, the cleaning time is 10min.
2) In order to enhance the binding force of the titanium plate and the nano aluminum oxide and graphite powder composite coating, increase the effective adsorption specific surface area of the polar plate, improve the conductivity and prolong the service life of the polar plate, the oxalic acid solution is used for carrying out acid etching treatment on the titanium plate. The mixed solution of oxalic acid and hydrochloric acid used in the acid etching treatment has the mass concentration of 5-6% and the mass concentration of hydrochloric acid of 12%. The acid etching temperature is 35-45 ℃, and the acid etching time is 3-4 h.
3) Drying for 30min at 50-60 ℃.
2. Preparation of coating liquid
Weighing a certain mass of carbon black conductive adhesive and an isopropanol solution at room temperature according to a mass ratio of 1:1, stirring for 1h on a magnetic stirrer to fully dissolve the mixed solution, wherein the initial 40min is fully dissolved at a rotating speed of 250r/min in the stirring process, and the later 20min is defoamed and mixed at a rotating speed of 80 r/min. Weighing a certain mass of nano-scale graphite powder and nano-scale aluminum oxide powder, placing the nano-scale graphite powder and the nano-scale aluminum oxide powder into the glue mixed liquid, and continuously stirring for 60min until the nano-scale graphite powder and the nano-scale aluminum oxide powder are fully mixed. Then weighing a certain mass of nano-scale graphite powder and nano-scale aluminum oxide powder, placing the nano-scale graphite powder and the nano-scale aluminum oxide powder into the glue mixed solution, continuously stirring for 30min, firstly stirring for 60min by magnetic force, then mixing for 30min by ultrasonic, and keeping the coating solution in a turbid liquid state for later use
3. Applying a coating
The pole plate brush evenly coats the coating liquid on one side of the processed titanium substrate. Baking for 30min under an infrared lamp every coating, after coating for 5 times and baking of the infrared lamp, drying for 1h at 120-150 ℃. After drying, the polar plate is wiped by using filter paper, no obvious black color exists on the filter paper, and the firmness of the coating meets the use requirement.
Compared with the prior art, the invention has the following advantages:
1. the treatment method can simultaneously remove various anions such as nitrate radical, fluorinion, chloride ion and the like in the wastewater. Effectively reduces the salinity and the conductivity of the wastewater.
2. In the treatment method, the nano-alumina has very high electropositive tendency, and a proper amount of nano-alumina is added into the adsorption polar plate, so that the porosity of the surface coating of the adsorption electrode can be effectively improved, the specific surface area can be increased, and the adsorption performance of the adsorption polar plate on anions can be obviously improved.
3. The treatment method can realize serialization, can realize equipment modularization by the technology, and can be suitable for the desalination treatment of the medium-low concentration saline wastewater with complex water quality.
Description of the drawings:
FIG. 1 is a structural design diagram of an adsorption unit assembly of the present invention
FIG. 2 is a flow chart of the process for treating nitrate nitrogen-containing wastewater by adsorption according to the present invention.
The specific implementation mode is as follows:
the following specific examples are provided to further illustrate the technical aspects of the present invention. But the invention is not limited in any way, and is also suitable for removing other inorganic anions in wastewater in the industries of electroplating, pesticide, fertilizer manufacturing, electronic component production and the like.
In order to control the ecological environmental pollution caused by nitrate radical and solve the practical problem that the total nitrogen index caused by the nitrate radical is difficult to reach the standard and discharge, the invention provides a method for treating the nitrate radical in industrial wastewater, which mainly comprises the following steps of (1) preparing a titanium-based nano aluminum oxide composite graphite powder adsorption polar plate by a coating method; (2) assembling the adsorption unit assembly; (3) Adsorbing and removing anions such as nitrate radical and the like in the wastewater under the environment of an electric field; and (4) regenerating the adsorption saturated polar plate. The treatment method is suitable for removing nitrate radicals in production wastewater in the electroplating industry, the pesticide industry, the fertilizer manufacturing industry, the electronic component production industry and other industries, the removal rate of the nitrate radicals is more than or equal to 75 percent, and meanwhile, a plurality of anions such as the nitrate radicals, fluoride ions, chloride ions and the like in the wastewater are removed. Effectively reduces nitrate radical, salt and conductivity of the wastewater. The nano-alumina has very high electropositive tendency, and a proper amount of nano-alumina is added into the adsorption polar plate, so that the porosity of the surface coating of the adsorption electrode can be effectively improved, the specific surface area can be increased, and the adsorption performance of the adsorption polar plate on anions can be obviously improved. The technology can realize serialization and equipment modularization.
Example 1
First step preparation of adsorption polar plate
1) The titanium plate is selected as the base material of the adsorption polar plate, the purity of the titanium plate is more than or equal to 99.9 percent, and the size of the processed titanium plate is 200 multiplied by 200mm. And ultrasonically cleaning the titanium plate by using a mixed solution of acetone and carbon tetrachloride. The mass ratio of the acetone to the carbon tetrachloride in the cleaning mixed solution is 2:1, the cleaning time is 10min. The acid etching is carried out by using the mixed solution of oxalic acid and hydrochloric acid. The acid etching temperature is 35 ℃, and the acid etching time is 3 hours. After the acid etching is finished, drying for 30min at 50-60 ℃ for later use; wherein the final concentration of the oxalic acid in the mixed solution of the oxalic acid and the hydrochloric acid is 5wt%, and the final concentration of the hydrochloric acid is 12wt%.
2) And (2) at room temperature, weighing 20g of carbon black conductive adhesive and 20g of isopropanol mixed solution, stirring for 1h on a magnetic stirrer to fully dissolve the carbon black conductive adhesive, fully dissolving the carbon black conductive adhesive at a rotation speed of 250r/min in the initial stage of the stirring process, and defoaming and mixing the mixed solution at a rotation speed of 80r/min in the later stage of 20min to obtain the adhesive mixed solution.
Weighing 1.5g of nano-scale graphite powder and 0.3 g of nano-scale aluminum oxide powder, placing the nano-scale graphite powder and the nano-scale aluminum oxide powder into the glue mixed solution, and continuously stirring for 60min until the nano-scale graphite powder and the nano-scale aluminum oxide powder are fully mixed to obtain the mixed solution.
Then weighing 1.5g of nano-scale graphite powder and 0.15g of nano-scale aluminum oxide powder, placing the nano-scale graphite powder and the nano-scale aluminum oxide powder in the mixed solution, continuously stirring for 30min, firstly magnetically stirring for 60min, and then ultrasonically mixing for 30min to obtain a coating solution, wherein the coating solution is in a turbid solution state for later use.
3) And uniformly coating the coating liquid on one side surface of the treated titanium substrate by using an electrode plate brush. Baking under an infrared lamp for 30min every coating, and after 15 times of coating and baking of the infrared lamp, drying for 1h at 120 ℃. After drying, the polar plate is wiped by using filter paper, no obvious black color exists on the filter paper, and the firmness of the coating meets the use requirement.
And secondly, selecting prepared adsorption plates to assemble a nitrate radical adsorption removal treatment unit, wherein the treatment unit is only composed of a single adsorption unit in the embodiment, and the reference of the figure 1:
the single adsorption unit consists of a fixing plate 1, an adsorption polar plate 2, an insulating rubber ring 3, an insulating nylon net 4 and an induction titanium wire net electrode 5; an induction titanium wire mesh electrode is arranged between the two fixed plates (the fixed plates are organic glass plates), adsorption polar plates are respectively arranged on two sides of the induction titanium wire mesh electrode, and an insulating nylon mesh is arranged between the induction titanium wire mesh electrode and the adsorption polar plates; the adsorption polar plate is sealed on the organic glass plate through an insulating rubber ring; namely, the single adsorption unit is sequentially an organic glass plate, an adsorption polar plate, an insulating nylon net, an induction titanium wire net electrode, an insulating nylon net, an adsorption polar plate and an organic glass plate; meanwhile, one sides of the two adsorption pole plates, which form the adsorption layers, are oppositely arranged, and one sides, which do not form the adsorption layers, are respectively sealed on the fixing plates through insulating rubber rings.
Two adjacent fixed plates of the adsorption units are connected through a hose, and the two adsorption polar plates are respectively connected with the positive and negative electrodes of an external direct-current voltage-stabilizing and current-stabilizing power supply through leads. A water inlet is reserved at the center of the lower end of one side of each adsorption unit, a water outlet is reserved at the center of the other side of each adsorption unit, and the distance between the polar plates of the two adsorption polar plates is 12mm.
And the third step is that the absorption unit treats the nitrate-containing wastewater.
The method comprises the steps of enabling waste water to be treated to be certain electroplating waste water cleaning water, enabling the conductivity to be 7300ms/cm, enabling the concentration of nitrate radicals to be 64mg/L, setting the current to be 4A, starting a peristaltic pump, enabling the flow rate to be 10ml/min, enabling the waste water to enter from a left water inlet of an adsorption unit, enabling the unit to be filled with a solution to be treated, enabling the nitrate radicals to be adsorbed on an adsorption pole plate through full contact of the waste water and the pole plate under the environment of an electric field, starting a power supply after air is exhausted, enabling the treated waste water to flow out from a water outlet of the adsorption unit, collecting effluent after adsorption treatment, and analyzing the effluent. The conductivity and current-voltage change of the solution are monitored in the reaction process, the adsorption time is 60min, the concentration of the treated effluent nitrate is 13mg/L, and the removal rate of the nitrate reaches 80%.
Fourth step of regeneration of saturated plates
The adsorption polar plate is used for multiple periods, and when the adsorption removal rate is lower than 30%, the polar plate needs to be regenerated in order to ensure the technical economy. And (3) exchanging the positive and negative electrodes of the polar plate and an external power supply, switching on the power supply, carrying out desorption reaction for 20min, and independently collecting high-nitrate concentrated solution generated in the regeneration process and treating the high-salt waste liquid.
Example 2
First step of preparation of electrode plate
1) The base material of the adsorption polar plate is a titanium plate, the purity of the titanium plate is more than or equal to 99.9 percent, and the size of the processed titanium plate is 200mm multiplied by 200mm. And ultrasonically cleaning the titanium plate by using a mixed solution of acetone and carbon tetrachloride. The mass ratio of acetone to carbon tetrachloride in the cleaning mixed solution is 2:1, the cleaning time is 10min. And (3) carrying out acid etching by using a mixed solution of oxalic acid and hydrochloric acid, wherein the acid etching temperature is 40 ℃, and the acid etching time is 4 hours. After the acid etching is finished, drying for 30min at 50-60 ℃ for later use; wherein the final concentration of oxalic acid in the mixed solution of oxalic acid and hydrochloric acid is 6wt%, and the final concentration of hydrochloric acid is 12wt%.
2) And (2) at room temperature, weighing 30g of carbon black conductive adhesive and 30g of isopropanol mixed solution, stirring for 1h on a magnetic stirrer to fully dissolve the carbon black conductive adhesive, fully dissolving the carbon black conductive adhesive at a rotation speed of 200r/min in the initial stage of the stirring process, and defoaming and mixing the mixed solution at a rotation speed of 100r/min in the later stage of 20min to obtain the adhesive mixed solution.
3g of nano-scale graphite powder and 0.5g of nano-scale aluminum trioxide powder are weighed and placed in the glue mixed solution to be continuously stirred for 60min until the mixed solution is fully mixed to obtain the mixed solution.
Then 3g of nano-scale graphite powder and 0.5g of nano-scale aluminum trioxide powder are weighed and placed in the mixed solution to be continuously stirred for 30min, magnetic stirring is firstly carried out for 60min, and then ultrasonic mixing is carried out for 30min, so as to obtain a coating solution, wherein the coating solution is in a turbid solution state for standby.
3) And uniformly coating the coating liquid on one side surface of the treated titanium substrate by using an electrode plate brush. Baking under an infrared lamp for 30min every coating, and after the coating is performed for 20 times and the baking of the infrared lamp is finished, drying for 1h at 120 ℃. After drying, the polar plate is wiped by using filter paper, no obvious black color exists on the filter paper, and the firmness of the coating meets the use requirement.
And secondly, selecting prepared adsorption plates and assembling a nitrate radical adsorption removal processing unit, and forming the processing unit shown in the figure 1 according to the method recorded in the example 1, wherein the distance between the two adsorption plates is 18mm.
The third step is that the absorption unit treats the nitrate radical-containing wastewater.
The method comprises the steps of treating comprehensive wastewater in a certain fine chemical industry park in Shandong, wherein the conductivity is 8400ms/cm, the concentration of nitrate radicals is 81mg/L, the current is set to be 3A, a peristaltic pump is started, the flow rate is 15ml/min, the wastewater enters from a water inlet in the left side of an adsorption unit, the unit is filled with a solution to be treated, the nitrate radicals are adsorbed on an adsorption polar plate through full contact between the wastewater and the polar plate under the environment of an electric field, a power supply is started after air is exhausted, the treated wastewater flows out from a water outlet of the adsorption unit, and effluent after adsorption treatment is collected and analyzed. The conductivity and current-voltage change of the solution are monitored in the reaction process, the adsorption time is 40min, the concentration of the treated effluent nitrate is 20mg/L, and the removal rate of the nitrate reaches 78%.
Fourth step of regeneration of saturated polar plate
After the total water amount of the adsorption polar plate reaches 12L, the adsorption removal rate is lower than 30%, and the polar plate needs to be regenerated in order to ensure the technical economy. And exchanging the anode and the cathode of the polar plate, turning on a power supply, carrying out desorption reaction for 20min, and separately collecting high-nitrate concentrated solution generated in the regeneration process, and treating the high-nitrate concentrated solution according to high-salt waste liquid.
Example 3
First step of preparation of electrode plate
1) The base material of the adsorption polar plate is a titanium plate, the purity of the titanium plate is more than or equal to 99.9 percent, and the size of the processed titanium plate is 200mm multiplied by 200mm. And ultrasonically cleaning the titanium plate by using a mixed solution of acetone and carbon tetrachloride. The mass ratio of the acetone to the carbon tetrachloride in the cleaning mixed solution is 2:1, the cleaning time is 10min. And (3) carrying out acid etching by using a mixed solution of oxalic acid and hydrochloric acid, wherein the acid etching temperature is 40 ℃, and the acid etching time is 4 hours. And after the acid etching is finished, drying the mixture at 50-60 ℃ for 30min for later use, wherein the final concentration of oxalic acid in the mixed solution of oxalic acid and hydrochloric acid is 6wt%, and the final concentration of hydrochloric acid is 12wt%.
2) And (2) at room temperature, weighing 30g of carbon black conductive adhesive and 30g of isopropanol mixed solution, stirring for 1h on a magnetic stirrer to fully dissolve the carbon black conductive adhesive, fully dissolving the carbon black conductive adhesive at a rotation speed of 200r/min in the initial stage of the stirring process, and defoaming and mixing the mixed solution at a rotation speed of 100r/min in the later stage of 20min to obtain the adhesive mixed solution.
3g of nano-scale graphite powder and 0.5g of nano-scale aluminum trioxide powder are weighed and placed in the glue mixed solution to be continuously stirred for 60min until the mixed solution is fully mixed to obtain the mixed solution.
Then 3g of nano-scale graphite powder and 0.5g of nano-scale aluminum trioxide powder are weighed and placed in the mixed solution to be continuously stirred for 30min, magnetic stirring is firstly carried out for 60min, and then ultrasonic mixing is carried out for 30min, so as to obtain a coating solution, wherein the coating solution is in a turbid solution state for standby.
3) And uniformly coating the coating liquid on the treated titanium substrate by using an electrode plate brush. Baking under an infrared lamp for 30min every coating, and after the coating is performed for 20 times and the baking of the infrared lamp is finished, drying for 1h at 120 ℃. After drying, the polar plate is wiped by filter paper, no obvious black color is formed on the filter paper, and the firmness of the coating meets the use requirement.
Secondly, assembling a single adsorption unit according to the description of the embodiment 1, and combining the four groups of adsorption units in series through a silicone tube to form a processing unit, namely, connecting the water outlet of the previous adsorption unit with the water inlet of the rest adsorption unit through the silicone tube, and repeating the steps to form the processing unit; the plate distance between two adsorption plates of each adsorption unit is 18mm.
And the third step is that the absorption unit treats the nitrate-containing wastewater.
The method comprises the steps of treating comprehensive wastewater of a certain fine chemical industry park in Shandong, wherein the conductivity is 8400ms/cm, the concentration of nitrate radicals is 81mg/L, the current is set to be 3A, a peristaltic pump is started, the flow rate is 15ml/min, the wastewater enters from a water inlet in the left side of an adsorption unit, the unit is filled with a solution to be treated, the nitrate radicals are adsorbed on an adsorption polar plate through full contact of the wastewater and the polar plate under the environment of an electric field, a power supply is started after air is exhausted, the treated wastewater flows out from a water outlet of the adsorption unit, and effluent after adsorption treatment is collected and analyzed. The conductivity and current-voltage change of the solution are monitored in the reaction process, the adsorption time is 40min, the concentration of the treated effluent nitrate is 15mg/L, and the removal rate of the nitrate reaches 87%.
Fourth step of regeneration of saturated plates
The adsorption removal rate of the adsorption polar plate is lower than 30%, and the polar plate needs to be regenerated in order to ensure the technical economy. And exchanging the anode and the cathode of the polar plate, turning on a power supply, carrying out desorption reaction for 20min, and separately collecting high-nitrate concentrated solution generated in the regeneration process, and treating the high-nitrate concentrated solution according to high-salt waste liquid.
Example 4
After the polar plate in the embodiment 1 is regenerated, the treatment unit is assembled according to the record in the embodiment 1 to treat wastewater, the treated wastewater is certain electroplating wastewater cleaning water, the conductivity is 7300ms/cm, the concentration of nitrate radicals is 64mg/L, the current is set to be 4A, a peristaltic pump is started, the flow rate is 10ml/min, the wastewater enters from a water inlet on the left side of the adsorption unit, the unit is filled with a solution to be treated, the nitrate radicals are adsorbed on the adsorption polar plate through the full contact of the wastewater and the polar plate in the environment of an electric field, a power supply is started after air is exhausted, the treated wastewater flows out from a water outlet of the adsorption unit, and effluent after adsorption treatment is collected and analyzed. The conductivity and current-voltage change of the solution are monitored in the reaction process, the adsorption time is 60min, the concentration of the treated effluent nitrate is 21mg/L, and the removal rate of the nitrate reaches 76%.
Claims (6)
1. A processing unit of nitrate radical in industrial wastewater is characterized in that: the treatment unit consists of at least one adsorption unit;
the adsorption unit comprises a fixing plate, an adsorption polar plate and an induction titanium wire mesh electrode;
an induction titanium wire mesh electrode is arranged between the two fixed plates, adsorption polar plates are respectively arranged on two sides of the induction titanium wire mesh electrode, and the base plates of the adsorption polar plates are selected from titanium plates;
the adsorption polar plate is formed by coating a nano aluminum oxide composite graphite powder coating liquid on one side of a substrate to form an adsorption layer, wherein the thickness of the adsorption layer is 8-10 micrometers;
an insulating net is arranged between the induction titanium wire mesh electrode and the adsorption polar plate on one side; the distance between two adsorption polar plates in the adsorption unit is 12-20mm;
the adsorption units are connected through hoses; the lower end of a fixing plate at one side of each adsorption unit is provided with a water inlet, and a fixing plate at the other side is provided with a water outlet;
the adsorption polar plate is sealed on the fixing plate through an insulating rubber ring; the adsorption polar plate is connected with an external direct current voltage and current stabilizing power supply through a lead.
2. A method for treating nitrate nitrogen in industrial wastewater by using the treatment unit as claimed in claim 1, which is characterized by comprising the following steps: the nitrate-containing wastewater is sequentially treated by the treatment unit of claim 1, and under the environment of an electric field, the wastewater is treated by the adsorption unit component, so that nitrate, chloride and fluoride anions are removed, the removal of nitrate ions in the wastewater is realized, and the total nitrogen and salt content in the wastewater is reduced.
3. The process according to claim 2, characterized in that: the environment of the electric field is that the current density is 10-40 mA/cm 2 The adsorption time is 60-120 min.
4. The process according to claim 2, characterized in that: exchanging the positive electrode and the negative electrode of an external power supply connected with the treatment unit after wastewater treatment, and controlling the current density to be 30-40 mA/cm 2 And processing for 20-60min to realize regeneration treatment.
5. The process according to claim 2, characterized in that: the nano aluminum oxide composite graphite powder coating liquid is prepared by the following method:
1) Preparing a glue mixed solution: mixing carbon black conductive adhesive and isopropanol solution according to the mass ratio of 1:1, mixing and fully dissolving;
2) Preparation of coating liquid: adding a mixed solution of nano-scale graphite powder and nano-scale aluminum oxide powder into the glue mixed solution, uniformly mixing the mixture after adding, and obtaining a coating solution when the mixture is in a turbid liquid state; wherein the mixing mass ratio of the nano graphite powder to the nano aluminum oxide powder is 5:1 to 10:1, the mass ratio of the coating liquid to the glue mixed liquid is 20:1 to 30:1.
6. the process of claim 5 wherein: the coating liquid is uniformly coated on one side of the substrate, the substrate is baked for 30min under an infrared lamp every coating, after 15-20 times of coating and baking of the infrared lamp, the substrate is dried in an oven at 120-150 ℃ for 1h.
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