CN109317197B - Preparation method of sewage denitrification catalyst - Google Patents
Preparation method of sewage denitrification catalyst Download PDFInfo
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- CN109317197B CN109317197B CN201710639863.7A CN201710639863A CN109317197B CN 109317197 B CN109317197 B CN 109317197B CN 201710639863 A CN201710639863 A CN 201710639863A CN 109317197 B CN109317197 B CN 109317197B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
- B01J31/02—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides
- B01J31/06—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides containing polymers
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/70—Treatment of water, waste water, or sewage by reduction
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/16—Nitrogen compounds, e.g. ammonia
- C02F2101/163—Nitrates
Abstract
A preparation method of a sewage denitrification catalyst, belonging to the field of sewage treatment. The preparation method is characterized by comprising the following preparation steps: activating and pretreating a macroporous polystyrene resin carrier, namely sequentially placing a catalyst precursor into ethanol with the mass concentration of 1-4% and citric acid modified PdCl2And (3) dipping in a copper sulfate dipping solution, carrying out reaction complexation, dipping in a mixed solution of sodium hydroxide and hydrazine hydrate, reacting for 2-4 h, separating a complex, and drying to obtain the catalyst. A large amount of metal ions are combined and uniformly dispersed on the inner surface of the exchange resin micropores, and the metal ions are reduced to form metal clusters which are deeply immersed in the three-dimensional network structure of the resin, so that the activity is uniformly dispersed on the resin and firmly combined.
Description
Technical Field
A preparation method of a sewage denitrification catalyst, belonging to the field of sewage treatment.
Background
The nitrogen element in the water body is mainly ionic nitrogen, wherein nitrate nitrogen is taken as the main component, and ammonia nitrogen and nitrite nitrogen are taken as the secondary components, the salts can cause pollution to the environment, the ammonia nitrogen can cause eutrophication of the water body, and the nitrite nitrogen can cause harm to the health of human bodies, animals and plants. The nitrate source in nature mainly comprises two aspects, namely wide waste water source and complex components, such as chemical fertilizer manufacturing, steel production, gunpowder manufacturing, feed production, meat processing, electronic components, flue gas denitration absorption liquid and the like, and part of nitrate can be reduced into nitrite after being taken into human bodies and animal bodies. Nitrite can oxidize hemoglobin in blood into ferrohemoglobin which does not have the capability of combining oxygen, and when the content of the ferrohemoglobin in the blood is increased, the capability of oxygen delivery of the blood is reduced, and serious patients cause human tissue purple plague, which is clinically called as methemoglobinemia. In addition, nitrite ions can cause baby blueness after entering a human body, and particularly, baby reaction within 4 months is sensitive, and the nitrite ions are easy to cause great harm to pregnant women, old and weak sensitive people. Nitrite can react with paraammonium in stomach to form strong carcinogen nitrosamine, and British, Chile and Columbia have reports of correlation between nitrate and high incidence rate of gastric cancer; a relationship between high nitrate levels in drinking water and the incidence of hypertension is found in the united states. According to rough statistics, about 3000 thousands of people in China drink high-nitrate saline water, and nitrate pollution becomes one of the main environmental factors for cancer occurrence in China. Therefore, the national relevant standards specify the concentration of nitrate in water, wherein the drinking water health standard specifies the maximum allowable concentration of nitrate to be 20mg/L, and the surface water quality standard GB3838-2002 specifies the maximum allowable concentration of nitrate in the surface water source of the centralized domestic drinking water to be 10 mg/L. In conclusion, how to effectively treat the high-concentration nitrate wastewater and improve the quality of the effluent water becomes one of the hot spots and difficulties in the field of water pollution control, and has been widely regarded by many researchers.
The method for treating the nitrate wastewater mainly comprises a physical-chemical method, a biological denitrification method and a catalytic reduction method. The method for removing nitrate in wastewater by a physical and chemical method mainly comprises an ion exchange method, reverse osmosis, electrodialysis, a steaming house method and the like. These processes are too costly to operate, they concentrate the nitrates in the medium or waste liquid, and do not actually remove them completely, but rather transfer or concentration of the nitrate contaminants takes place.
Biological denitrification is divided into two processes of nitrification and denitrification, and NH is generated by nitrification reaction4 +The nitrate is converted into nitrate, and denitrification refers to that denitrifying bacteria take the nitrate as an electron acceptor and reduce the nitrate into nitrogen to be released into the atmosphere under the condition of oxygen deficiency or oxygen-free.
The chemical catalytic reduction of nitrate refers to the reduction of nitrate into nitrogen by using hydrogen, formic acid and the like as reducing agents, adding a proper catalyst in the reaction and utilizing the catalytic action of the catalyst. The process has the advantages that the reaction activity is high and is 30 times higher than that of biological denitrification, and the key point of the process is to prepare the catalyst with good performance, so that the catalyst has high reaction activity and high selectivity.
There is a prior art activated carbon cloth supported bimetallic Pd-Cu nanocatalyst comprising about 1 wt% Pd and about 0.35-0.45 wt% Cu and having a surface Cu/Pd metal ratio of about 8-10m2/m 2. The nanocatalyst is capable of removing nitrate and/or nitrite from wastewater with high selectivity to nitrogen. The preparation method of the catalyst is sputtering deposition, continuous hydrogen flow and nitrogen flow are required to be kept for high-temperature roasting reduction in the preparation process, the production process is difficult to control, and the prepared catalyst has low dispersity, so that the activity is poor and is only 77.6% at most.
Literature<<Experimental study on nitrate removal by chemical denitrification>>In the batch type complete mixing reactor, the authors carried out experimental research on catalytic reduction of nitrate by using Pd-Cu/gamma-Al 2O3 as a catalyst, and the results show that under the action of a supported metal catalyst, nitrate can be effectively reduced to generate N2The total nitrogen removal rate reaches more than 80%. In the preparation process of the catalyst, the periodic stirring and room temperature drying time are longer. In addition, for the supported catalyst, the roasting at 350 ℃ is difficult to ensure the firm combination of the active component and the carrier, and the service life of the catalyst is easy to shorten.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: overcomes the defects of the prior art and provides a preparation method of the sewage denitrification catalyst with simple, scientific and reasonable preparation process.
The technical scheme adopted by the invention for solving the technical problems is as follows: the preparation method of the sewage denitrification catalyst is characterized by comprising the following preparation steps:
1) the catalyst precursor A is prepared by the activation pretreatment of a macroporous polystyrene resin carrier, and specifically comprises the following steps:
1.1 adding macroporous polystyrene resin particles into a saturated calcium hydroxide solution, stirring at room temperature for 60-120 min, and washing the resin particles to be neutral;
1.2 adding the resin particles washed to be neutral in the step 1.1 into a methanol solution for stirring treatment at room temperature, wherein the stirring time is 60-120 min, and then washing;
1.3, soaking the resin washed in the step 1.2 in an EDTA saturated solution for 6-24 h, separating the resin, and drying to obtain the activated pretreated carrier.
2) Preparation of catalyst precursor: placing the catalyst precursor A in ethanol with the mass concentration of 1-4% and citric acid modified PdCl2Dipping in the dipping solution for 4-8h, separating a complex after the reaction is finished, and drying to obtain a catalyst precursor B; soaking the catalyst precursor B in a mixed solution of sodium hydroxide and hydrazine hydrate, reacting for 2-4 h, and separating a complex to obtain a catalyst precursor C;
3) preparing a composite catalyst: soaking the catalyst precursor C in an EDTA saturated solution for 6-24 h, separating, and drying to obtain a catalyst precursor D; placing the catalyst precursor D in ethanol and citric acid modified copper sulfate impregnation liquid with the mass concentration of 2% -8% for impregnation for 4-8h, separating a complex after the reaction is finished, and drying to obtain a catalyst precursor E; and (3) soaking the catalyst precursor E in a mixed solution of sodium hydroxide and hydrazine hydrate, reacting for 2-4 h, separating a complex, and drying to obtain the catalyst.
The invention also provides a preparation method of the sewage denitrification catalyst, and the preparation process is simple, scientific and reasonable. The carrier is pretreated in multiple steps, so that the binding force of the carrier, EDTA (ethylene diamine tetraacetic acid) and active components is increased, a large amount of metal ions are bound and uniformly dispersed on the inner surface of micropores of the exchange resin, and the metal ions are reduced to form metal clusters which are deeply sunk in a three-dimensional network structure of the resin, so that the activity is uniformly dispersed on the resin and is firmly bound. The catalyst is applied to the process of catalytic reduction of nitrate nitrogen in sewage, the removal rate of the nitrate nitrogen is improved, and the selectivity of nitrogen is better.
Preferably, the dipping time of the resin washed in the step 1.2 in the EDTA saturated solution is 9-13 h.
Preferably, the mass ratio of the saturated calcium hydroxide solution to the macroporous polystyrene resin is 100: 16-24, and the stirring time is 80-100 min. The preferable mass ratio can better pre-treat the carrier, so that the carrier and the active component are combined more firmly and stably.
Preferably, the mass ratio of the methanol solution to the macroporous polystyrene resin is 100: 16-24, and the stirring time is 80-100 min. The preferable mass ratio can better pre-treat the carrier, so that the carrier and the active component are combined more firmly and stably.
Preferably, the ethanol and citric acid modified PdCl in the step 2)2The preparation method of the impregnation liquid comprises the following steps: taking PdCl2The citric acid is dissolved in a mixed water solution of ethanol and citric acid, wherein the mass concentration of the ethanol in the mixed water solution is 20-30%, and the mass concentration of the citric acid in the mixed water solution is 0.5-1%. Preferred PdCl2The preparation method of the impregnation liquid can enable the Pd to be combined on the inner surfaces of the micropores of the exchange resin more uniformly and stably.
Preferably, the ethanol and citric acid modified PdCl2PdCl in immersion liquid2The mass concentration of the catalyst is 2% -3%. PdCl of appropriate concentration2The catalytic effect can be promoted to be stronger.
Preferably, the mass concentration of the sodium hydroxide in the mixed solution of the sodium hydroxide and the hydrazine hydrate in the step 2) is 1-4%, and the mass concentration of the hydrazine hydrate is 2-3%. The optimal concentration can better promote the combination of the rest carriers of the active components, the combination is firmer, and the catalytic effect is stable for a longer period.
Preferably, the preparation method of the ethanol and citric acid modified copper sulfate impregnation liquid in the step 3) comprises the step of dissolving copper sulfate in a mixed aqueous solution of ethanol and citric acid, wherein the mass concentration of ethanol in the mixed aqueous solution is 20-30%, and the mass concentration of citric acid in the mixed aqueous solution is 0.5-1%. The preferable preparation method of the copper sulfate impregnation liquid can enable Cu to be more uniformly and stably combined on the inner surfaces of the micropores of the exchange resin.
Preferably, the mass concentration of copper sulfate in the ethanol and citric acid modified copper sulfate impregnation liquid is 3-5%. The optimal concentration enables the arrangement of Cu and Pd to be more reasonable and the catalytic effect to be better.
The prepared sewage denitrification catalyst comprises active components and a carrier, wherein the active components comprise the following components in percentage by mass: pd1% -1.5%, Cu 1% -1.5%; the carrier is macroporous polystyrene resin, and the specific surface of the macroporous polystyrene resin is 400 m2/g~600m2Per g, pore volume of 0.4 m3/g~2.0m3A pore diameter of 3.0 nm to 5.0 nm. The catalyst is applied to the denitrification reaction of sewage, N2The selectivity is high, the content of total nitrogen in the sewage can be effectively reduced, the ammonia nitrogen in the sewage is ensured not to exceed the standard, and the national and local discharge indexes of the total nitrogen and the ammonia nitrogen in the sewage can be met.
Preferably, the content of Pd in the catalyst is 1.1-1.3% by mass percent.
Preferably, the content of Cu in the catalyst is 1.2-1.3% by mass percent. The preferred active component content achieves the best nitrate chemical reduction catalytic effect of the catalyst.
Preferably, the specific surface area of the macroporous polystyrene resin is 500m2/g～540m2G, pore volume of 1.4 m3/g～1.7m3(ii) in terms of/g. The physical property of the optimized macroporous polystyrene resin can load the active component with the optimal density, so that the catalytic effect is optimal, and the catalyst has longer stabilization time.
Compared with the prior art, the sewage denitrification catalyst and the preparation method thereof have the beneficial effects that:
1. the active components are highly effective and stable. The carrier is pretreated in multiple steps, so that the binding force of the carrier, EDTA (ethylene diamine tetraacetic acid) and active components is increased, a large amount of metal ions are bound and uniformly dispersed on the inner surface of micropores of the exchange resin, and the metal ions are reduced to form metal clusters which are deeply sunk in a three-dimensional network structure of the resin, so that the activity is uniformly dispersed on the resin and is firmly bound;
2. the removal rate of nitrate nitrogen and the selectivity of N2 are high. The catalyst is applied to the process of catalytic reduction of nitrate nitrogen in sewage, the removal rate of the nitrate nitrogen reaches more than 85%, and the selectivity of nitrogen reaches more than 90%.
Detailed Description
The present invention is further illustrated by the following specific examples, of which example 1 is the most preferred.
Example 1
Step one, putting 100ml of saturated calcium hydroxide solution and 20g of macroporous polystyrene resin particles into a flask with a stirrer, stirring at room temperature for 60min, and washing with deionized water until the washing water is neutral; adding the resin particles into 100ml of methanol solution, stirring at room temperature, stirring for 60min, and washing with deionized water for 3 times for later use. Preparing an EDTA saturated solution, soaking the pretreated resin in the EDTA saturated solution for 6 hours, taking out the resin carrier, and drying in vacuum at room temperature;
step two, taking 2.5g of PdCl2Dissolved in a mixed solution of 97.5g of ethanol, water and citric acid, wherein the concentration of the ethanol in the mixed solution is 25 percent, the concentration of the citric acid in the mixed solution is 0.8 percent, and the balance is water. And (3) soaking the pretreated resin carrier in the mixed solution for 4 hours, then taking out, and drying in a vacuum drying oven. Soaking the dried catalyst precursor in a mixed solution of sodium hydroxide and hydrazine hydrate, wherein the concentration of the sodium hydroxide in the solution is 1.5 percent, the concentration of the hydrazine hydrate is 2 percent, separating the catalyst precursor after soaking for 2 hours, and drying the catalyst precursor in vacuum at room temperature for later use;
and step three, soaking the catalyst precursor in an EDTA saturated solution for 6 hours, separating, drying in vacuum at room temperature, and placing in a mixed solution of 100g of blue vitriol solution, wherein the blue vitriol concentration is 4%, the ethanol concentration is 25%, and the citric acid concentration is 0.7%. Taking out after dipping for 4h, and placing in a vacuum drying oven for drying. Soaking the dried catalyst precursor in a mixed solution of sodium hydroxide and hydrazine hydrate, wherein the concentration of the sodium hydroxide in the solution is 3 percent, the concentration of the hydrazine hydrate is 2.5 percent, separating the catalyst precursor after soaking for 2 hours, and drying the catalyst precursor in vacuum at room temperature for later use;
the content of each active component of the prepared catalyst in the catalyst by mass percent is as follows: pd1.2%, Cu 1.25%; the carrier is macroporous polystyrene resin, and the specific surface area of the macroporous polystyrene resin is 500m2/g～540m2G, pore volume of 1.4 m3/g～1.7m3(ii)/g, the pore diameter is 3.0 nm to 5.0 nm;
the prepared catalyst is applied to the effluent of a certain acrylonitrile catalytic oxidation device, wherein the nitrate nitrogen of the water is 496mg/L, the pH is =5.3, and the main process operating conditions are as follows: h2The flow rate is 50ml/min, the pH value of inlet water is adjusted to 5.0, the volume of the reactor is 200ml, the adding amount of the catalyst is 0.15g, and the reaction time is 90 min. After treatment, the effluent is 44.6mg/L of nitrate nitrogen, the ammonia nitrogen is 9mg/L, the removal rate of the reaction nitrate nitrogen is 91 percent, and the selectivity of the nitrogen is 95 percent.
Example 2
Step one, putting 100ml of saturated calcium hydroxide solution and 18g of macroporous polystyrene resin particles into a flask with a stirrer, stirring at room temperature for 80min, and washing with deionized water until the washing water is neutral; adding the resin particles into 100ml of methanol solution, stirring at room temperature, stirring for 80min, and washing with deionized water for 3 times for later use. Preparing an EDTA saturated solution, soaking the pretreated resin in the EDTA saturated solution for 9 hours, taking out the resin carrier, and drying in vacuum at room temperature;
step two, taking 2gPdCl2Dissolved in a mixed solution of 98g of ethanol, water and citric acid, wherein the concentration of the ethanol in the mixed solution is 23 percent, the concentration of the citric acid in the mixed solution is 0.6 percent, and the balance is water. And (3) soaking the pretreated resin carrier in the mixed solution for 5 hours, then taking out, and drying in a vacuum drying oven. Soaking the dried catalyst precursor in a mixed solution of sodium hydroxide and hydrazine hydrate, wherein the concentration of the sodium hydroxide in the solution is 2 percent, the concentration of the hydrazine hydrate is 2.8 percent, separating the catalyst precursor after soaking for 2.3h, and drying the catalyst precursor in vacuum at room temperature for later use;
and step three, soaking the catalyst precursor in an EDTA saturated solution for 9 hours, separating, drying in vacuum at room temperature, and placing in a mixed solution of 100g of blue vitriol solution, wherein the blue vitriol concentration is 3%, the ethanol concentration is 23%, and the citric acid concentration is 0.6%. And taking out after soaking for 5h, and placing in a vacuum drying oven for drying. Soaking the dried catalyst precursor in a mixed solution of sodium hydroxide and hydrazine hydrate, wherein the concentration of the sodium hydroxide in the solution is 2 percent, the concentration of the hydrazine hydrate is 2.8 percent, separating the catalyst precursor after soaking for 2.3h, and drying the catalyst precursor in vacuum at room temperature for later use;
the content of each active component of the prepared catalyst in the catalyst by mass percent is as follows: pd1.1%, Cu 1.25%; the carrier is macroporous polystyrene resin, and the specific surface area of the macroporous polystyrene resin is 480 m2/g～560m2Per g, pore volume of 0.9m3/g～1.6m3(ii)/g, the pore diameter is 3.0 nm to 5.0 nm;
the prepared catalyst was applied to the effluent of a catalyst plant unit with 619mg/L of aqueous nitrate nitrogen and pH = 7.2. The main process operating conditions are as follows: h2The flow rate is 50ml/min, the pH value of inlet water is adjusted to 5.0, the volume of the reactor is 200ml, the adding amount of the catalyst is 0.15g, and the reaction time is 90 min. After treatment, the effluent is 68mg/L of nitrate nitrogen, the ammonia nitrogen is 15mg/L, the removal rate of the nitrate nitrogen in the reaction is 89%, and the selectivity of the nitrogen is 93.3%.
Example 3
Step one, putting 100ml of saturated calcium hydroxide solution and 22g of macroporous polystyrene resin particles into a flask with a stirrer, stirring at room temperature for 100min, and washing with deionized water until the washing water is neutral; adding the resin particles into 100ml of methanol solution, stirring at room temperature, stirring for 100min, and washing with deionized water for 3 times for later use. Preparing an EDTA saturated solution, soaking the pretreated resin in the EDTA saturated solution for 13 hours, taking out the resin carrier, and drying in vacuum at room temperature;
step two, taking 3gPdCl2Dissolved in a mixed solution of 97g of ethanol, water and citric acid, wherein the concentration of the ethanol in the mixed solution is 27 percent, the concentration of the citric acid in the mixed solution is 0.8 percent, and the balance is water. And (3) soaking the pretreated resin carrier in the mixed solution for 5 hours, then taking out, and drying in a vacuum drying oven. Soaking the dried catalyst precursor in a mixed solution of sodium hydroxide and hydrazine hydrate, wherein the concentration of the sodium hydroxide in the solution is 3.5 percent, the concentration of the hydrazine hydrate is 2.3 percent, separating the catalyst precursor after soaking for 2.7 hours, and drying the catalyst precursor in vacuum at room temperature for later use;
and step three, soaking the catalyst precursor in an EDTA saturated solution for 12 hours, separating, vacuum-drying at room temperature, placing in a mixed solution of 100g of a blue vitriol solution, wherein the blue vitriol has the concentration of 5%, the ethanol has the concentration of 27% and the citric acid has the concentration of 0.8%, soaking for 5 hours, taking out, and placing in a vacuum drying oven for drying. Soaking the dried catalyst precursor in a mixed solution of sodium hydroxide and hydrazine hydrate, wherein the concentration of the sodium hydroxide in the solution is 3.5 percent, the concentration of the hydrazine hydrate is 2.3 percent, separating the catalyst precursor after soaking for 2.7 hours, and drying the catalyst precursor in vacuum at room temperature for later use;
the content of each active component of the prepared catalyst in the catalyst by mass percent is as follows: pd1.3%, Cu 1.25%; the carrier is macroporous polystyrene resin, and the specific surface area of the macroporous polystyrene resin is 490 m2/g～570m2Per g, pore volume of 1.0m3/g～1.6m3(ii)/g, the pore diameter is 3.0 nm to 5.0 nm;
the prepared catalyst was applied to the effluent of a catalyst plant unit with 601mg/L of aqueous nitrate nitrogen and pH = 7.2. The main process operating conditions are as follows: h2The flow rate is 50ml/min, the pH value of inlet water is adjusted to 5.0, the volume of the reactor is 200ml, the adding amount of the catalyst is 0.15g, and the reaction time is 90 min. After treatment, the effluent is 64.3mg/L of nitrate nitrogen, the ammonia nitrogen is 12mg/L, the removal rate of the reaction nitrate nitrogen is 89.3 percent, and the nitrogen selectivity is 92.9 percent.
Example 4
Step one, putting 100ml of saturated calcium hydroxide solution and 16g of macroporous polystyrene resin particles into a flask with a stirrer, stirring at room temperature for 120min, and washing with deionized water until the washing water is neutral; adding the resin particles into 100ml of methanol solution, stirring at room temperature, stirring for 120min, and washing with deionized water for 3 times for later use. And (3) preparing an EDTA saturated solution, soaking the pretreated resin in the EDTA saturated solution for 24 hours, taking out the resin carrier, and drying in vacuum at room temperature.
Step two, taking 1gPdCl2Dissolving in a mixed solution of 99g of ethanol, water and citric acid, wherein the concentration of the ethanol in the mixed solution is 30 percent, the concentration of the citric acid in the mixed solution is 1 percent, and the balance is water. And (3) soaking the pretreated resin carrier in the mixed solution for 7 hours, then taking out, and drying in a vacuum drying oven. Soaking the dried catalyst precursor in a mixed solution of sodium hydroxide and hydrazine hydrate, wherein the concentration of the sodium hydroxide in the solution is 4 percentSoaking for 3h, separating a catalyst precursor, and drying at room temperature in vacuum for later use, wherein the concentration of hydrazine hydrate is 2%;
and step three, soaking the catalyst precursor in an EDTA saturated solution for 20 hours, separating, vacuum-drying at room temperature, placing in a mixed solution of 100g of a blue vitriol solution, wherein the blue vitriol concentration is 2%, the ethanol concentration is 30%, the citric acid concentration is 1%, soaking for 7 hours, taking out, and placing in a vacuum drying oven for drying. Soaking the dried catalyst precursor in a mixed solution of sodium hydroxide and hydrazine hydrate, wherein the concentration of the sodium hydroxide in the solution is 4 percent, the concentration of the hydrazine hydrate is 2 percent, separating the catalyst precursor after 3 hours of soaking, and drying the catalyst precursor in vacuum at room temperature for later use;
the content of each active component of the prepared catalyst in the catalyst by mass percent is as follows: pd1%, Cu 1%; the carrier is macroporous polystyrene resin, and the specific surface area of the macroporous polystyrene resin is 400 m2/g~600m2Per g, pore volume of 0.4 m3/g~1.8m3(ii)/g, the pore diameter is 3.0 nm to 5.0 nm;
the prepared catalyst was applied to the effluent of a catalyst plant unit with 620mg/L of aqueous nitrate nitrogen and pH = 7.2. The main process operating conditions are as follows: h2The flow rate is 50ml/min, the pH value of inlet water is adjusted to 5.0, the volume of the reactor is 200ml, the adding amount of the catalyst is 0.15g, and the reaction time is 90 min. After treatment, the effluent is 83.08mg/L of nitrate nitrogen, the ammonia nitrogen is 14mg/L, the removal rate of the reaction nitrate nitrogen is 86.6 percent, and the selectivity of nitrogen is 92.1 percent.
Example 5
Step one, putting 100ml of saturated calcium hydroxide solution and 24g of macroporous polystyrene resin particles into a flask with a stirrer, stirring at room temperature for 120min, and washing with deionized water until the washing water is neutral; adding the resin particles into 100ml of methanol solution, stirring at room temperature, stirring for 120min, and washing with deionized water for 3 times for later use. Preparing an EDTA saturated solution, soaking the pretreated resin in the EDTA saturated solution for 24 hours, taking out the resin carrier, and drying in vacuum at room temperature;
step two, taking 4gPdCl2Dissolving in 96g mixed solution of ethanol, water and citric acid, and mixingThe concentration of ethanol in the solution is 20%, the concentration of citric acid is 0.5%, and the balance is water. And (3) soaking the pretreated resin carrier in the mixed solution for 8 hours, then taking out, and drying in a vacuum drying oven. Soaking the dried catalyst precursor in a mixed solution of sodium hydroxide and hydrazine hydrate, wherein the concentration of the sodium hydroxide in the solution is 1 percent, the concentration of the hydrazine hydrate is 1 percent, separating the catalyst precursor after soaking for 4 hours, and drying the catalyst precursor in vacuum at room temperature for later use;
and step three, soaking the catalyst precursor in an EDTA saturated solution for 24 hours, separating, vacuum-drying at room temperature, placing in a mixed solution of 100g of a blue vitriol solution, wherein the blue vitriol has the concentration of 8%, the ethanol has the concentration of 20% and the citric acid has the concentration of 0.5%, soaking for 8 hours, taking out, and placing in a vacuum drying oven for drying. Soaking the dried catalyst precursor in a mixed solution of sodium hydroxide and hydrazine hydrate, wherein the concentration of the sodium hydroxide in the solution is 1 percent, the concentration of the hydrazine hydrate is 1 percent, separating the catalyst precursor after soaking for 4 hours, and drying the catalyst precursor in vacuum at room temperature for later use;
the content of each active component of the prepared catalyst in the catalyst by mass percent is as follows: pd1.5%, Cu 1.5%; the carrier is macroporous polystyrene resin, and the specific surface area of the macroporous polystyrene resin is 450 m2/g~600m2Per g, pore volume of 0.4 m3/g~2.0m3(ii)/g, the pore diameter is 3.0 nm to 5.0 nm;
the catalyst obtained was applied to the effluent of a catalyst plant unit with a nitrate nitrogen of 529mg/L and a pH = 7.2. The main process operating conditions are as follows: h2The flow rate is 50ml/min, the pH value of inlet water is adjusted to 5.0, the volume of the reactor is 200ml, the adding amount of the catalyst is 0.15g, and the reaction time is 90 min. After treatment, the effluent is 77.2mg/L of nitrate nitrogen, the ammonia nitrogen is 11mg/L, the removal rate of the nitrate nitrogen in the reaction is 85.4 percent, and the selectivity of the nitrogen is 90.2 percent.
Comparative example 1:
step one, preparing an EDTA saturated solution, soaking the macroporous polystyrene resin in the EDTA saturated solution for 6 hours, taking out the resin carrier, and drying in vacuum at room temperature.
Step two and step three are the same as step two and step three of example 1.
The prepared catalyst is applied to the effluent of a certain acrylonitrile catalytic oxidation device, the nitrogen content of the water nitrate is 500mg/L, the pH =5.3, and the main process operating conditions are as follows: h2The flow rate is 50ml/min, the pH value of inlet water is adjusted to 5.0, the volume of the reactor is 200ml, the adding amount of the catalyst is 0.15g, and the reaction time is 90 min. After treatment, the effluent is 211mg/L of nitrate nitrogen, the ammonia nitrogen is 92mg/L, the removal rate of the reaction nitrate nitrogen is 57.8 percent, and the selectivity of the nitrogen is 68.2 percent.
Comparative example 2
Step one, putting 100ml of saturated sodium hydroxide solution and 20g of macroporous polystyrene resin particles into a flask with a stirrer, stirring at room temperature for 60min, and washing with deionized water until the washing water is neutral; adding the resin particles into 100ml of methanol solution, stirring at room temperature, stirring for 60min, and washing with deionized water for 3 times for later use. And (3) preparing an EDTA saturated solution, soaking the pretreated resin in the EDTA saturated solution for 6 hours, taking out the resin carrier, and drying in vacuum at room temperature.
Step two and step three are the same as step two and step three of example 1.
The prepared catalyst is applied to the effluent of a certain acrylonitrile catalytic oxidation device, the nitrogen content of the water nitrate is 500mg/L, the pH =5.3, and the main process operating conditions are as follows: h2The flow rate is 50ml/min, the pH value of inlet water is adjusted to 5.0, the volume of the reactor is 200ml, the adding amount of the catalyst is 0.15g, and the reaction time is 90 min. After treatment, the effluent is 105mg/L of nitrate nitrogen, the ammonia nitrogen is 78mg/L, the removal rate of the reaction nitrate nitrogen is 79%, and the selectivity of the nitrogen is 80%.
Comparative example 3:
taking gamma-Al2 O3200ml is used as a carrier, soaked for 30min by using EDTA with the same volume, dried at 100 ℃ in vacuum, taken out and added with 1% palladium chloride solution with the same volume for soaking for 90min, dried in a vacuum drying oven at 100 ℃ after soaking is finished, and roasted for 2h at 450 ℃ in a muffle furnace. After the baking is finished, the reaction product is cooled to room temperature, reduced by hydrazine hydrate, washed by deionized water and dried. Soaking the catalyst precursor in EDTA for 30min, vacuum drying at 100 deg.c, soaking in 1% copper chloride solution for equal volume for equal soaking timeAnd (3) 90min, drying in a vacuum drying oven at 100 ℃ after the impregnation is finished, and roasting in a muffle furnace at 450 ℃ for 2 h. After the baking is finished, the reaction product is cooled to room temperature, reduced by hydrazine hydrate, washed by deionized water and dried.
The prepared catalyst is applied to the effluent of a certain acrylonitrile catalytic oxidation device, the nitrogen content of the water nitrate is 500mg/L, the pH =5.3, and the main process operating conditions are as follows: h2The flow rate is 50ml/min, the pH value of inlet water is adjusted to 5.0, the volume of the reactor is 200ml, the adding amount of the catalyst is 0.15g, and the reaction time is 90 min. After treatment, the effluent is 121mg/L of nitrate nitrogen, the ammonia nitrogen is 93mg/L, the removal rate of the nitrate nitrogen in the reaction is 76%, and the selectivity of the nitrogen is 75.4%.
Comparative example 4
Taking gamma-Al2 O3200ml of carrier is put into saturated calcium hydroxide solution of 1000ml, after being soaked for 4 hours, deionized water is washed until the washing water is neutral, then the carrier is soaked for 60 minutes in methanol solution at room temperature, washed for 3 times by the deionized water, soaked for 30 minutes by EDTA with the same volume, dried in vacuum at 100 ℃, taken out and added with 1% palladium chloride solution for soaking with the same volume, the soaking time is 90 minutes, after the soaking is finished, the carrier is dried in a vacuum drying oven at 100 ℃, and then the carrier is placed in a muffle furnace to be roasted for 2 hours at 450 ℃. After the baking is finished, the reaction product is cooled to room temperature, reduced by hydrazine hydrate, washed by deionized water and dried. And then soaking the catalyst precursor in EDTA with the same volume for 30min, performing vacuum drying at 100 ℃, taking out, adding 1% copper chloride solution for soaking with the same volume for 90min, drying in a vacuum drying oven at 100 ℃ after soaking, and roasting in a muffle furnace at 450 ℃ for 2 h. After the baking is finished, the reaction product is cooled to room temperature, reduced by hydrazine hydrate, washed by deionized water and dried.
In the preparation process, the surface of the obtained catalyst is covered by calcium, and the catalyst cannot be applied to a nitrate nitrogen reduction test.
Comparative example 5
Soaking 200ml of activated carbon serving as a carrier in EDTA (ethylene diamine tetraacetic acid) with the same volume for 30min, then carrying out vacuum drying at 100 ℃, taking out the activated carbon, then adding a 1% palladium chloride solution for soaking with the same volume for 90min, drying the activated carbon in a vacuum drying oven at 100 ℃ after the soaking is finished, and roasting the activated carbon in a muffle furnace at 450 ℃ for 2 h. After the baking is finished, the reaction product is cooled to room temperature, reduced by hydrazine hydrate, washed by deionized water and dried. And then soaking the catalyst precursor in EDTA with the same volume for 30min, performing vacuum drying at 100 ℃, taking out, adding 1% copper chloride solution for soaking with the same volume for 90min, drying in a vacuum drying oven at 100 ℃ after soaking, and roasting in a muffle furnace at 450 ℃ for 2 h. After the baking is finished, the reaction product is cooled to room temperature, reduced by hydrazine hydrate, washed by deionized water and dried.
The prepared catalyst is applied to the effluent of a certain acrylonitrile catalytic oxidation device, the nitrogen content of the water nitrate is 500mg/L, the pH =5.3, and the main process operating conditions are as follows: h2The flow rate is 50ml/min, the pH value of inlet water is adjusted to 5.0, the volume of the reactor is 200ml, the adding amount of the catalyst is 0.15g, and the reaction time is 90 min. After treatment, the effluent is 198mg/L of nitrate nitrogen, the ammonia nitrogen is 93mg/L, the removal rate of the nitrate nitrogen in the reaction is 60 percent, and the selectivity of the nitrogen is 69.2 percent.
Comparative example 6
Taking gamma-Al2 O3200ml of carrier is put into saturated calcium hydroxide solution of 1000ml, after being soaked for 4 hours, deionized water is washed until the washing water is neutral, then the carrier is soaked for 60 minutes in methanol solution at room temperature, washed for 3 times by the deionized water, soaked for 30 minutes by EDTA with the same volume, dried in vacuum at 100 ℃, taken out and added with 1% palladium chloride solution for soaking with the same volume, the soaking time is 90 minutes, after the soaking is finished, the carrier is dried in a vacuum drying oven at 100 ℃, and then the carrier is placed in a muffle furnace to be roasted for 2 hours at 450 ℃. After the baking is finished, the reaction product is cooled to room temperature, reduced by hydrazine hydrate, washed by deionized water and dried. And then soaking the catalyst precursor in EDTA with the same volume for 30min, performing vacuum drying at 100 ℃, taking out, adding 1% copper chloride solution for soaking with the same volume for 90min, drying in a vacuum drying oven at 100 ℃ after soaking, and roasting in a muffle furnace at 450 ℃ for 2 h. After the baking is finished, the reaction product is cooled to room temperature, reduced by hydrazine hydrate, washed by deionized water and dried.
In the preparation process, the surface of the obtained catalyst is covered by calcium, and the catalyst cannot be applied to a nitrate nitrogen reduction test.
The foregoing is directed to preferred embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow. However, any simple modification, equivalent change and modification of the above embodiments according to the technical essence of the present invention are within the protection scope of the technical solution of the present invention.
Claims (10)
1. The preparation method of the sewage denitrification catalyst is characterized by comprising the following preparation steps:
1) the catalyst precursor A is prepared by the activation pretreatment of a macroporous polystyrene resin carrier, and specifically comprises the following steps:
1.1 adding macroporous polystyrene resin particles into a saturated calcium hydroxide solution, stirring at room temperature for 60-120 min, and washing the resin particles to be neutral;
1.2 adding the resin particles washed to be neutral in the step 1.1 into a methanol solution for stirring treatment at room temperature, wherein the stirring time is 60-120 min, and then washing;
1.3, soaking the resin washed in the step 1.2 in an EDTA saturated solution for 6-24 hours, separating the resin, and drying to obtain an activated pretreated carrier;
2) preparation of catalyst precursor: placing the catalyst precursor A in ethanol with the mass concentration of 1-4% and citric acid modified PdCl2Dipping in the dipping solution for 4-8h, separating a complex after the reaction is finished, and drying to obtain a catalyst precursor B; soaking the catalyst precursor B in a mixed solution of sodium hydroxide and hydrazine hydrate, reacting for 2-4 h, and separating a complex to obtain a catalyst precursor C;
3) preparing a composite catalyst: soaking the catalyst precursor C in an EDTA saturated solution for 6-24 h, separating, and drying to obtain a catalyst precursor D; placing the catalyst precursor D in an ethanol and citric acid modified copper sulfate dipping solution with the mass concentration of 2-8% for dipping for 4-8h, separating a complex after the reaction is finished, and drying to obtain a catalyst precursor E; and (3) soaking the catalyst precursor E in a mixed solution of sodium hydroxide and hydrazine hydrate, reacting for 2-4 h, separating a complex, and drying to obtain the catalyst.
2. The method for preparing a denitrification catalyst for wastewater according to claim 1, wherein the method comprises the following steps: and (3) soaking the resin washed in the step (1.2) in an EDTA saturated solution for 9-13 h.
3. The method for preparing a denitrification catalyst for wastewater according to claim 1, wherein the method comprises the following steps: the mass ratio of the saturated calcium hydroxide solution to the macroporous polystyrene resin is 100: 16-24, and the stirring time is 80-100 min.
4. The method for preparing a denitrification catalyst for wastewater according to claim 1, wherein the method comprises the following steps: the mass ratio of the methanol solution to the macroporous polystyrene resin is 100: 16-24, and the stirring time is 80-100 min.
5. The method for preparing a denitrification catalyst for wastewater according to claim 1, wherein the method comprises the following steps: the ethanol and citric acid modified PdCl in the step 2)2The preparation method of the impregnation liquid comprises the following steps: taking PdCl2The citric acid is dissolved in a mixed water solution of ethanol and citric acid, wherein the mass concentration of the ethanol in the mixed water solution is 20-30%, and the mass concentration of the citric acid in the mixed water solution is 0.5-1%.
6. The method for preparing a denitrification catalyst for wastewater according to claim 1, wherein the method comprises the following steps: the ethanol and citric acid modified PdCl2PdCl in immersion liquid2The mass concentration of the catalyst is 2% -3%.
7. The method for preparing a denitrification catalyst for wastewater according to claim 1, wherein the method comprises the following steps: in the step 2), the mass concentration of the sodium hydroxide in the mixed solution of the sodium hydroxide and the hydrazine hydrate is 1-4%, and the mass concentration of the hydrazine hydrate is 2-3%.
8. The method for preparing a denitrification catalyst for wastewater according to claim 1, wherein the method comprises the following steps: the preparation method of the ethanol and citric acid modified copper sulfate impregnation liquid in the step 3) comprises the step of dissolving copper sulfate in a mixed water solution of ethanol and citric acid, wherein the mass concentration of ethanol in the mixed water solution is 20-30%, and the mass concentration of citric acid in the mixed water solution is 0.5-1%.
9. The method for preparing a denitrification catalyst for wastewater according to claim 1, wherein the method comprises the following steps: the mass concentration of copper sulfate in the ethanol and citric acid modified copper sulfate impregnation liquid is 3% -5%.
10. The method for preparing a denitrification catalyst for wastewater according to claim 1, wherein the method comprises the following steps: the prepared sewage denitrification catalyst comprises active components and a carrier, wherein the active components comprise the following components in percentage by mass: pd1% -1.5%, Cu 1% -1.5%; the carrier is macroporous polystyrene resin, and the specific surface of the macroporous polystyrene resin is 400 m2/g~600m2Per g, pore volume of 0.4 m3/g~2.0m3A pore diameter of 3.0 nm to 5.0 nm.
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