CN110876921B - Preparation method of desulfurization and denitrification wastewater adsorbent - Google Patents
Preparation method of desulfurization and denitrification wastewater adsorbent Download PDFInfo
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Abstract
The invention belongs to the field of sewage treatment, and particularly relates to a preparation method of a desulfurization and denitrification wastewater adsorbent. The preparation method of the desulfurization and denitrification wastewater adsorbent comprises the steps of respectively preparing hydrotalcite with adjustable interlayer structures and polypyrrole-modified montmorillonite, and changing the surface electrical property of the material by utilizing the adjustable characteristics of the type and the quantity of cations of a hydrotalcite polar plate; by intercalating the montmorillonite, the modification effect of the montmorillonite and polypyrrole is improved, and the adsorption property to nitrate radicals is improved while the steric hindrance is formed; and finally, carrying out composite bonding intercalation on the hydrotalcite and the montmorillonite to form a layered structure composite material with certain steric hindrance, wherein the material is applied to adsorbing nitrate radicals in high-salt wastewater (particularly high-salt wastewater with higher sulfate radical content), the adsorption selectivity and the adsorption capacity have good effects, and the removal rate of the nitrate radicals in the wastewater is more than or equal to 60%.
Description
Technical Field
The invention belongs to the field of sewage treatment, and particularly relates to a preparation method of a desulfurization and denitrification wastewater adsorbent.
Background
After the nitrate is accumulated in human body, nitrite can be produced by action of nitrate reductase, and under the action of various nitrogen-containing organic compounds, such as amine, urea and cyanamide, the nitrite can be converted into nitrosamine and nitrosophthalein amine which have carcinogenesis, teratogenesis and mutagenesis, so as to induce human body to produce various tumors, such as tumor diseases of intestinal tract, nervous system, brain, skin and skeleton, etc. Nitrate is also easy to cause goiter, inhibits the thyroid from taking in inorganic iodine, and even in a water body with high iodine content, if the content of nitrate in water is high, endemic goiter is easy to cause. Nitrite also reacts with hemoglobin in the blood to form methemoglobin, which affects the oxygen transport in the blood and makes the cell tissue anoxic, even leading to respiratory cycle failure in severe cases. Compared with adults, infants are sensitive to the potential toxicity of nitrate, and when the content of the nitrate in drinking water reaches 90-140mg/L, the infants are easy to suffer from methemoglobinemia, the skin of the infants turns into blue gray, which is commonly called as 'blue infant disease', and serious people can cause suffocation. Since nitrate pollution can be harmful to human health, various countries around the world set standards for nitrate content in drinking water, where the world health organization stipulates Nitrate (NO) 3 -N) not more than 10mg/L, Nitrite (NO) 2 -N) not more than 0.91mg/L, the U.S. EPA specified maximum limit being (NO) 3 -N)10mg/L，(NO 2 -N)1mg/L, and the content of nitrate nitrogen in water is less than or equal to 10mg/L according to the water quality standard of domestic drinking water (GBS749-2006) in China.
The pollution of nitrate has received extensive attention, and the research on the nitrate control technology is increasing at home and abroad. At present, the control technology of nitrate mainly comprises a biological method, a physical chemical method and a chemical reduction method. The biological method is a method for gradually converting nitrogen-containing substances in sewage into nitrogen under the action of microorganisms. The physical and chemical methods mainly include a membrane separation method, an ion exchange method and an adsorption method. However, these methods generally have high running cost and complicated regeneration process. The chemical reduction method is a very effective method for degrading nitrate, but how to reduce harmful substances, namely ammonia nitrogen and nitrite in a reduction product and improve the selectivity of nitrogen in the reduction product is a research hotspot at present. Although the catalytic hydrogenation reduction method can effectively improve the selectivity of nitrogen in the reduction product, the method uses hydrogen as a reducing agent, has certain potential safety hazard, and has low solubility of hydrogen in water and low utilization rate.
Patent CN 107694541A discloses a preparation and application of a nitrate treating agent, which takes cotton as a template, adopts a coprecipitation method to synthesize zinc-titanium-iron ternary hydrotalcite-like compound with biological morphology, and obtains the nitrate treating agent by roasting in a muffle furnace. The invention also provides application of the nitrate treating agent prepared by the method in nitrate wastewater treatment. The nitrate treating agent prepared by the method has good adsorption effect on nitrate, is convenient to separate, has simple and easy regeneration method, and has wide application prospect in the field of nitrate wastewater treatment. But the treatment agent has better effect when being applied to the treatment of the conventional nitrate-containing wastewater, and does not relate to the absorption of nitrate in high-salinity wastewater. The salt content in the high-salt wastewater severely limits the adsorption effect of the adsorbent, so that the adsorbent needs to have certain adsorption selectivity in the process of adsorbing nitrate by the high-salt wastewater.
In the literature, "research on adsorption and degradation of nitrate ions by modified montmorillonite", authors provide that modified montmorillonite is obtained by exchanging interlayer cations of montmorillonite with polydiallyldimethylammonium chloride, and the structural ferric ions of montmorillonite are chemically reduced to the structural ferrous ions. The capacity of unmodified montmorillonite in different oxidation states for adsorbing and degrading nitrate ions is measured; the level of nitrate ion adsorption by the oxidized modified montmorillonite under different charging conditions; the ability of the reduced modified montmorillonite to degrade nitrate ions. The experimental results show that: the oxidized unmodified montmorillonite can hardly adsorb and reduce and degrade nitrate ions; the reduced unmodified montmorillonite can absorb nitrate ions of about 0.0054mmol/g, and generates a very small amount of low-valence nitro products; the oxidation state modified montmorillonite can adsorb nitrate ions of 0.23mmol/g, and the adsorption capacity of the oxidation state modified montmorillonite is increased along with the increase of the concentration of interlayer polymerization cations. The modified clay mineral is proved to be capable of strongly adsorbing nitrate ions, and a potential research direction is provided for the treatment of nitrate ion pollution. The article also does not relate to the treatment of waste water in which sulfate ions are present in the waste water in competition for adsorption with nitrate ions.
At present, the adsorbent is mostly applied to treating conventional wastewater containing nitrate ions, and the salt content in the wastewater is low. However, when the adsorbent is applied to the treatment of high-salinity wastewater, other anions in the wastewater rapidly occupy the adsorption sites on the surface of the adsorbent due to the competitive adsorption effect, so that the adsorption effect of nitrate is reduced.
Disclosure of Invention
The invention aims to provide a preparation method of a desulfurization and denitrification wastewater adsorbent, the prepared adsorbent is applied to adsorbing high-salinity wastewater, particularly high-salinity wastewater with high sulfate radical content, the nitrate radical adsorption selectivity and the adsorption capacity have good effects, and the removal rate of nitrate radicals in the wastewater is more than or equal to 60%.
The preparation method of the desulfurization and denitrification wastewater adsorbent comprises the following steps:
stage one, preparing magnesium-iron hydrotalcite:
(1) preparation of Mg (NO) 3 ) 2 ·6H 2 O and Fe (NO) 3 ) 3 ·9H 2 Mixed salt solution A of O, NaOH and Na 2 CO 3 The mixed solution B of (1);
(2) adding deionized water into a reactor, dropwise adding the mixed salt solution A and the mixed solution B into the reactor, stirring simultaneously, and controlling the pH value of the mixed stirring liquid in the reactor to be 9-10;
(3) after the dropwise addition is finished, the slurry is subjected to heat preservation and stirring at 60 ℃, aged for 12 hours, the formed hydrotalcite is filtered and washed, and a filter cake is transferred to a crucible and dried for later use;
stage two, intercalation montmorillonite fine clay preparation:
(4) pulverizing montmorillonite raw soil to less than 50 meshes, adding into deionized water, stirring with a stirrer for 30-60 min, standing, removing montmorillonite slurry on the upper layer, and removing sand and stone on the lower layer; adjusting the pH value of the montmorillonite slurry to acidity, then heating and flocculating for 10-15 minutes, standing at room temperature, drying after centrifugal separation, and grinding to obtain montmorillonite fine soil;
(5) adding montmorillonite fine soil into deionized water, stirring for 30min, adding 1mol/L NaCl solution, stirring the mixed solution at 65 deg.C for 2 hr, standing for 2 hr, adding 1mol/L NaCl solution, stirring at 65 deg.C for 2 hr, standing overnight, filtering, repeatedly washing with distilled water until no Cl is formed - Drying at 120 ℃, grinding, sieving with a 200-mesh sieve, and activating the product at 105 ℃ for 1-2 days to obtain sodium montmorillonite;
(6) dispersing sodium-based montmorillonite into distilled water to obtain sodium-based montmorillonite slurry for later use; respectively preparing 0.4mol/L NaOH solution and 0.2mol/L ferric trichloride solution, dripping the NaOH solution into the ferric trichloride solution, vigorously stirring for 2-4h, aging at room temperature for 12h, pouring into sodium-based montmorillonite slurry, vigorously stirring for 4-6h, filtering, repeatedly washing with distilled water until no Cl exists - Drying at 120 ℃ to obtain the intercalated montmorillonite fine soil;
stage three, modifying intercalated montmorillonite fine clay polypyrrole:
(7) adding the fine intercalated montmorillonite soil into deionized water, stirring vigorously for 60-90min, and adding FeCl of the same mass as the fine intercalated montmorillonite soil at 25-35 deg.C 3 Then adding pyrrole, reacting for 3-4h at 30 ℃, respectively centrifugally washing for 3-4 times by using water and acetone to obtain modified montmorillonite, and drying for later use;
and a fourth stage: high shear bonding:
(8) and (3) adding the hydrotalcite prepared in the step (3) and the modified montmorillonite prepared in the step (7) into deionized water, shearing for 60-90min by using a high-shear disperser, centrifugally washing for 3 times by using the deionized water, drying in a forced air drying box at 110 ℃, roasting a dried sample at 250-300 ℃ for 4h, and preparing the desulfurization and denitrification wastewater adsorbent.
Wherein:
in the step (1), in the mixed salt solution A, Mg 2+ The mass concentration of the substance is 0.6-0.8mol/L, Fe 3+ The concentration of the substance is 0.15-0.2 mol/L; in the mixed solution B, Na 2 CO 3 The mass concentration of the substance is 0.3-0.4mol/L, and the mass concentration of the NaOH substance is 1.5-2 mol/L.
In the step (2), the dropping speed is 600-800ml/h, and the volume ratio of the deionized water to the mixed salt solution A to the mixed solution B is 2: 1: 1-2.5: 1: 1.
in the step (3), the drying temperature is 105 ℃, and the drying time is 12 hours.
In the step (4), the mass ratio of the montmorillonite raw soil to the deionized water is 0.05-0.2: 1.
in the step (4), the granularity of the montmorillonite fine soil is less than 200 meshes.
In the step (5), adding the montmorillonite fine soil into deionized water to obtain a montmorillonite aqueous solution, wherein the mass ratio of the montmorillonite fine soil to the deionized water is 0.05-0.2: 1; stirring for 30min, adding 1mol/L NaCl solution, wherein the volume ratio of the NaCl solution to the montmorillonite aqueous solution is 1:1-3:1, stirring the mixed solution at 65 ℃ for 2h, standing for 2h, adding 1mol/L NaCl solution, adding the NaCl solution, stirring at 65 ℃ for 2h, standing overnight; suction filtering, washing with distilled water repeatedly until no Cl is formed - Drying at 120 deg.C, grinding, sieving with 200 mesh sieve, and activating at 105 deg.C for 1-2 days to obtain sodium montmorillonite.
In the step (7), the mass ratio of the intercalated montmorillonite refined soil to the deionized water is 0.05-0.2: 1.
in the step (5), the mass ratio of the pyrrole to the intercalated montmorillonite fine soil is 0.06-0.25: 1.
in the step (8), the mass ratio of the hydrotalcite to the modified montmorillonite is 1: 1-4: 1.
preferably, the preparation method of the desulfurization and denitrification wastewater adsorbent provided by the invention specifically comprises the following steps:
stage one, preparing magnesium-iron hydrotalcite:
(1) preparation of Mg (NO) 3 ) 2 ·6H 2 O and Fe (NO) 3 ) 3 ·9H 2 Mixed salt solution A of O, solution Mg 2+ The mass concentration of the substance is 0.6-0.8mol/L, Fe 3+ The mass concentration of the substance is 0.15-0.2 mol/L; NaOH and Na are prepared 2 CO 3 Mixed solution B of (1), Na in solution 2 CO 3 The mass concentration of the substance is 0.3-0.4mol/L, and the mass concentration of the NaOH substance is 1.5-2 mol/L. Mixing the mixed salt solution A and the mixed salt solution B according to a volume ratio of 1: a ratio of 1 for standby.
(2) Adding a certain volume of deionized water into a reactor, dropwise adding the mixed salt solution A and the mixed solution B into the reactor, stirring vigorously, and controlling the pH value of the mixed stirring liquid in the reactor to be 9-10. Wherein the dropping speed is 600-800ml/h, the volume ratio of the deionized water to the solution A and the solution B is 2: 1: 1-2.5: 1: 1.
(3) after the dropwise addition, the slurry is subjected to heat preservation and stirring at 60 ℃ and is aged for 12 hours. Filtering the formed hydrotalcite after aging, washing and filtering repeatedly for three times, transferring a filter cake into a crucible, drying for 12 hours in a drying oven at 105 ℃, and placing the product into a dryer for later use.
Stage two, preparing intercalation montmorillonite fine clay:
(4) pulverizing raw montmorillonite to less than 50 meshes, weighing a certain mass of pulverized montmorillonite, adding into a certain volume of deionized water, wherein the mass ratio of montmorillonite to deionized water is 0.05-0.2, stirring with a stirrer for 30-60 min, standing, removing montmorillonite slurry on the upper layer, and discarding sand and stone on the lower layer. Adjusting the pH value of the montmorillonite slurry on the upper layer to be acidic, then heating and flocculating for 10-15 minutes on an electric furnace, standing for a certain time at room temperature, centrifugally separating to remove partial water and salt, drying, and grinding to obtain the montmorillonite fine soil with a certain particle size.
(5) Adding montmorillonite fine soil into deionized water, stirring for 30min, and then adding 1mol/L NaCl solution, wherein the volume ratio of the NaCl solution to the montmorillonite solution is 1:1-3:1, stirring the mixed solution at 65 ℃ for 2 hours, and then standing for 2 hours. Then adding 1mol/L NaCl solution, and adding the NaCl solution in a volume ratio of 3:1-4: after stirring at 1, 65 ℃ for 2h, the mixture was left to stand overnight. Suction filtration is carried out the next day, and the filtrate is repeatedly washed by distilled water until no Cl is generated - Until now. Drying at 120 deg.C, grinding, sieving with 200 mesh sieve, and activating at 105 deg.C for 1-2 days to obtain sodium montmorillonite for use.
(6) Weighing 10-20g sodium-based montmorillonite, and distilling in 500-1000mlWater, fully dispersed and reserved for standby. Respectively preparing 0.4mol/L NaOH solution and 2000ml of 0.2mol/L ferric trichloride solution, slowly dripping the NaOH solution into the 0.2mol/L ferric trichloride solution, simultaneously and violently stirring for 2-4h, after finishing aging at room temperature for 12h, quickly pouring the dispersed sodium-based montmorillonite slurry, violently stirring for 4-6h, carrying out suction filtration, and repeatedly washing with distilled water until no Cl exists - Drying at 120 deg.C to obtain refined clay of intercalated montmorillonite.
Stage three, modifying intercalated montmorillonite fine clay polypyrrole:
(7) adding the intercalated montmorillonite fine soil prepared in the step (6) into deionized water according to the mass ratio of 0.05-0.2, mechanically and violently stirring for 60-90min, and slowly adding FeCl with the same mass as the intercalated montmorillonite fine soil 3 Then adding pyrrole with the mass ratio of the pyrrole to the fine soil of the intercalated montmorillonite being 0.06-0.25, reacting for 3-4h at 30 ℃, respectively centrifugally washing with water and acetone for 3-4 times to obtain the modified montmorillonite, and drying for later use.
And a fourth stage: high shear bonding:
(8) mixing the hydrotalcite prepared in the step (3) and the modified montmorillonite prepared in the step (7) according to the mass ratio of 1: 1-4:1, adding the mixture into deionized water, shearing the mixture for 60-90min by using a high-shear disperser, centrifugally washing the mixture for 3 times by using the deionized water, drying the mixture in a forced air drying box at 110 ℃, and roasting the dried sample at 250-300 ℃ for 4 hours to prepare the desulfurization and denitrification wastewater adsorbent.
The method takes the desulfurization and denitrification wastewater of the oil refinery as the target water quality, the wastewater is high-salinity wastewater, the content of nitrate ions in the wastewater is 300-plus-300 ppm, the content of sulfate ions in the wastewater is 3000ppm, the conventional adsorbent is adopted, the adsorption effect is poor, and the removal rate of nitrate ions in the wastewater is more than or equal to 60 percent when the adsorbent provided by the invention is used for treating the wastewater.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention respectively prepares hydrotalcite with adjustable and controllable interlayer structure and polypyrrole modified montmorillonite, and utilizes the adjustable and variable characteristics of the type and the quantity of cations of a hydrotalcite polar plate to change the surface electrical property of the material; by intercalating the montmorillonite, the modification effect of the montmorillonite and polypyrrole is improved, and the adsorption property to nitrate radicals is improved while the steric hindrance is formed; and finally, carrying out composite bonding intercalation on the hydrotalcite and the montmorillonite to form a layered structure composite material with certain steric hindrance, wherein the material is applied to adsorbing nitrate radicals in high-salt wastewater (particularly high-salt wastewater with higher sulfate radical content), and has good adsorption selectivity and adsorption capacity.
2. The adsorbent prepared by the invention is applied to the process of adsorbing nitrate radical in high-salt wastewater, can be regenerated and reused through an adsorbent regeneration tower at 220 ℃ after the adsorption of the adsorbent is saturated, and is applied to the process of adsorbing nitrate radical in high-salt wastewater after the regeneration is finished, so that the removal rate of nitrate radical is still stably more than or equal to 60%.
Detailed Description
The present invention is further described below with reference to examples.
The starting materials used in the examples are all commercially available except where otherwise indicated.
Example 1
The preparation method of the desulfurization and denitrification wastewater adsorbent comprises the following steps:
(1) 2L of Mg (NO) is prepared 3 ) 2 ·6H 2 O and Fe (NO) 3 ) 3 ·9H 2 Mixed salt solution A of O, Mg in solution 2+ The mass concentration of the substance is 0.6mol/L, Fe 3+ The mass concentration of the substance is 0.15 mol/L; 2L of NaOH and Na are prepared 2 CO 3 Mixed solution B, Na of 2 CO 3 The mass concentration of the substance is 0.3mol/L, and the mass concentration of the NaOH substance is 1.5 mol/L. After 4L of deionized water was added into a 10L reactor, the mixed salt solution A and the mixed solution B were added dropwise into the reactor at a dropping rate of 800ml/h while vigorously stirring, and the pH of the mixed and stirred solution in the reactor was controlled to 9. After titration, the slurry is stirred at the temperature of 60 ℃ and aged for 12 h. Filtering the formed hydrotalcite after aging, washing and filtering repeatedly for three times, transferring a filter cake into a crucible, drying for 12 hours in a drying oven at 105 ℃, and placing the product into a dryer for later use.
(2) Weighing raw montmorillonite soil 1kg, pulverizing to less than 50 mesh, weighing pulverizedThen adding the mixture into a plastic bucket, adding 10L of deionized water, stirring for 30 minutes by a stirrer, standing, removing montmorillonite slurry on the upper layer, and removing sand and stones on the lower layer. Adjusting the pH value of the montmorillonite slurry on the upper layer to acidity, then heating and flocculating for 10 minutes on an electric furnace, standing for a certain time at room temperature, centrifugally separating to remove partial water and salt, drying and grinding. 100g of purified montmorillonite fine soil is taken and added into deionized water, stirred and then kept stand, 400ml of 1mol/L NaCl solution is added, stirred for 2h at 65 ℃ and then kept stand for 2 h. 100ml of a 1mol/L NaCl solution was added thereto, and the mixture was stirred at 65 ℃ for 2 hours and then allowed to stand overnight. Suction filtration is carried out the next day, and the filtrate is repeatedly washed by distilled water until no Cl is generated - Until now. Drying at 120 deg.C, grinding, sieving with 200 mesh sieve, and activating at 105 deg.C for 1 day. Weighing 10g of sodium-based montmorillonite by using a balance, putting into an erlenmeyer flask, adding 500ml of distilled water, and violently shaking the erlenmeyer flask to fully disperse the montmorillonite in the water for later use. Respectively preparing 0.4mol/L NaOH solution and 2000ml of 0.2mol/L ferric trichloride solution, slowly dripping the NaOH solution into the 0.2mol/L ferric trichloride solution, simultaneously and violently stirring for 4h, after finishing aging for 12h at room temperature, quickly pouring the dispersed sodium-based montmorillonite slurry, violently stirring for 6h, carrying out suction filtration, and repeatedly washing with distilled water until no Cl exists - The prepared intercalated montmorillonite is dried at 120 ℃ for standby.
Adding 100g of prepared intercalated montmorillonite fine soil into 1L of deionized water, mechanically and violently stirring for 60min, and adding FeCl at a temperature of 25 DEG C 3 100g, then adding 12.5ml of pyrrole, reacting for 3h at 30 ℃, respectively centrifugally washing for 3 times by using water and acetone to obtain the modified montmorillonite, and drying for later use.
(3) And (3) accurately weighing 10g of hydrotalcite prepared in the step (1) and 5g of modified montmorillonite prepared in the step (2), adding the hydrotalcite and the modified montmorillonite into 1L of deionized water, shearing the mixture for 60min by using a high-shear disperser, centrifugally washing the mixture for 3 times by using the deionized water, drying the mixture in a forced air drying oven at 110 ℃, and roasting the dried sample for 4 hours at 250 ℃ to prepare the adsorbent.
Taking desulfurization and denitrification wastewater of an oil refinery, wherein the concentration of nitrate in the wastewater is 300mg/L, the concentration of sulfate is 2880mg/L, the dosage of the adsorbent is 1g/L, the reaction time is 60min, and after settling for 30min, supernatant liquid is taken for detection, the concentration of nitrate in effluent is 115mg/L, the removal rate of nitrate is 61.7%, the concentration of sulfate in effluent is 2825mg/L, and the adsorption amount of sulfate is 55mg/L, which shows that the adsorbent has a better selective adsorption effect on nitrate in the desulfurization and denitrification wastewater.
After the adsorption of the adsorbent is saturated, the adsorbent is placed in a muffle furnace for regeneration at 220 ℃, and the regenerated adsorbent is repeatedly used in the nitrate adsorption process of high-salt wastewater, so that the nitrate removal rate can be stably maintained at over 60 percent.
Example 2
The preparation method of the desulfurization and denitrification wastewater adsorbent comprises the following steps:
(1) formulation 2LMg (NO) 3 ) 2 ·6H 2 O and Fe (NO) 3 ) 3 ·9H 2 Mixed salt solution A of O, Mg in solution 2+ The mass concentration of the substance is 0.8mol/L, Fe 3+ The mass concentration of the substance is 0.2 mol/L; preparation of 2LNaOH and Na 2 CO 3 Mixed solution B, Na of 2 CO 3 The mass concentration of the substance is 0.4mol/L, and the mass concentration of the NaOH substance is 2.0 mol/L. After 4L of deionized water is added into a 10L reactor, the mixed salt solution A and the mixed solution B are dropwise added into the reactor at a dropping speed of 600ml/h while vigorously stirring, and the pH value of the mixed stirring liquid in the reactor is controlled to be 10. After titration, the slurry is stirred at the temperature of 60 ℃ and aged for 12 h. And after aging, filtering the formed hydrotalcite, washing and filtering repeatedly for three times, transferring a filter cake into a crucible, drying for 12 hours in a drying oven at 105 ℃, and placing the product into a dryer for later use.
(2) Weighing 2kg of raw montmorillonite, crushing to be less than 50 meshes, weighing the crushed raw montmorillonite, adding the crushed raw montmorillonite into a plastic barrel, adding 20L of deionized water, stirring for 60 minutes by using a stirrer, standing, removing montmorillonite slurry on the upper layer, and removing sand and stones on the lower layer. Adjusting the pH value of the montmorillonite slurry on the upper layer to acidity, then heating and flocculating for 15 minutes on an electric furnace, standing for a certain time at room temperature, centrifugally separating to remove partial water and salt, drying and grinding. 100g of purified montmorillonite fine soil is taken and added into deionized water, stirred and then kept stand, 400ml of 1mol/L NaCl solution is added, stirred for 2h at 65 ℃ and then kept stand for 2 h. Then 100ml of 1mol/L NaCl solution is added,after stirring at 65 ℃ for 2h, the mixture was left to stand overnight. Repeatedly washing the filtrate with distilled water the next day until no Cl is formed - Until now. Drying at 120 deg.C, grinding, sieving with 200 mesh sieve, and activating at 105 deg.C for 1 day. Weighing 10g of sodium-based montmorillonite by using a balance, putting into an erlenmeyer flask, adding 500ml of distilled water, and violently shaking the erlenmeyer flask to fully disperse the montmorillonite in the water for later use. Respectively preparing 0.4mol/L NaOH solution and 2000ml of 0.2mol/L ferric trichloride solution, slowly dripping the NaOH solution into the 0.2mol/L ferric trichloride solution, simultaneously and violently stirring for 2h, after finishing aging for 12h at room temperature, quickly pouring the dispersed sodium-based montmorillonite slurry, violently stirring for 4h, carrying out suction filtration, and repeatedly washing with distilled water until no Cl exists - Drying the obtained intercalated montmorillonite at 120 deg.C for use. Adding 200g of the prepared intercalated montmorillonite fine soil into 2L of deionized water, mechanically and violently stirring for 90min, and adding FeCl at the temperature of 35 DEG C 3 200g, then adding 25ml of pyrrole, reacting for 4h at 30 ℃, respectively centrifugally washing for 4 times by using water and acetone to obtain the modified montmorillonite, and drying for later use.
(3) Accurately weighing 20g of hydrotalcite prepared in the step (1) and 10g of modified montmorillonite prepared in the step (2), adding the hydrotalcite and the modified montmorillonite into 2L of deionized water, shearing the mixture for 90min by using a high-shear disperser, centrifugally washing the mixture for 3 times by using the deionized water, drying the mixture in a forced air drying oven at 110 ℃, and roasting the dried sample for 4 hours at 300 ℃ to prepare the adsorbent.
Taking desulfurization and denitrification wastewater of an oil refinery, wherein the nitrate concentration of the wastewater is 270mg/L, the sulfate concentration is 2830mg/L, the adding amount of the adsorbent is 1g/L, the reaction time is 60min, after settling for 30min, supernatant liquid is taken for detection, the nitrate concentration of effluent is 104mg/L, the removal rate of nitrate is 61.5%, the sulfate concentration of effluent is 2792mg/L, and the sulfate adsorption amount is 38mg/L, which shows that the adsorbent has a better selective adsorption effect on nitrate in the desulfurization and denitrification wastewater.
After the adsorption of the adsorbent is saturated, the adsorbent is placed in a muffle furnace for regeneration at 220 ℃, and the regenerated adsorbent is repeatedly used in the nitrate adsorption process of high-salt wastewater, so that the nitrate removal rate can be stably maintained at over 60 percent.
Comparative example 1
The magnesium-aluminum hydrotalcite commodity sold in the market is applied to desulfurization and denitrification wastewater of a certain oil refinery, the nitrate concentration of the wastewater is 270mg/L, the adding amount of the adsorbent is 1g/L, the reaction time is 60min, after sedimentation is carried out for 30min, supernatant is taken for detection, the nitrate concentration of effluent is 267mg/L, the nitrate removal rate is 1.1%, and the removal effect is poor.
Comparative example 2
The magnesium-iron hydrotalcite prepared in the step (1) in the embodiment 1 is applied to desulfurization and denitrification wastewater of a certain oil refinery, the nitrate concentration of the wastewater is 270mg/L, the sulfate concentration is 2830mg/L, the adding amount of the hydrotalcite is 1g/L, the reaction time is 60min, after the hydrotalcite is settled for 30min, a supernatant is taken for detection, the nitrate concentration of effluent is 219mg/L, the removal rate of nitrate is 18.9%, the sulfate concentration of the effluent is 2770mg/L, the adsorption amount of sulfate is 60mg/L, and the removal effect is poor.
Comparative example 3
The pyrrole-modified montmorillonite prepared in the step (2) in the example 1 is independently applied to desulfurization and denitrification wastewater of a certain oil refinery, the nitrate concentration of the wastewater is 270mg/L, the sulfate concentration is 2830mg/L, the adding amount of hydrotalcite is 1g/L, the reaction time is 60min, after sedimentation is carried out for 30min, a supernatant is taken for detection, the nitrate concentration of effluent is 157mg/L, the nitrate removal rate is 41.9%, the sulfate concentration of the effluent is 2790mg/L, and the sulfate adsorption amount is 40 mg/L.
Comparative example 4
10g of magnesium-iron hydrotalcite prepared in the step (1) of the example 1 and 2g of pyrrole-modified montmorillonite prepared in the step (2) of the example 1 are added into 2L of deionized water, and are sheared for 90min by a high shear disperser, and are centrifugally washed for 3 times by the deionized water, and then are dried in a forced air drying oven at 110 ℃, and the dried sample is roasted for 4h at 300 ℃ to prepare the adsorbent.
The adsorbent is used for desulfurization and denitrification wastewater of a certain oil refinery, the concentration of nitrate in the wastewater is 300mg/L, the concentration of sulfate radical in the wastewater is 2880mg/L, the dosage of the adsorbent is 1g/L, the reaction time is 60min, after sedimentation is carried out for 30min, supernatant is taken for detection, the concentration of nitrate radical in effluent is 171mg/L, the removal rate of nitrate radical is 43%, the concentration of sulfate radical in effluent is 2799mg/L, and the adsorption quantity of sulfate radical is 81 mg/L.
Comparative example 5
Adding 5g of magnesium-iron hydrotalcite prepared in the step (1) in the example 1 and 10g of pyrrole-modified montmorillonite prepared in the step (2) in the example 1 into 2L of deionized water, shearing for 90min by using a high-shear disperser, centrifugally washing for 3 times by using the deionized water, drying at 110 ℃ in a forced air drying oven, and roasting a sample at 300 ℃ for 4h to prepare the adsorbent.
The adsorbent is used for desulfurization and denitrification wastewater of a certain oil refinery, the concentration of nitrate in the wastewater is 300mg/L, the concentration of sulfate radical in the wastewater is 2880mg/L, the dosage of the adsorbent is 1g/L, the reaction time is 60min, after sedimentation is carried out for 30min, supernatant is taken for detection, the concentration of nitrate radical in effluent is 164mg/L, the removal rate of nitrate radical is 45.3%, the concentration of sulfate radical in effluent is 2812mg/L, and the adsorption quantity of sulfate radical is 68 mg/L.
Comparative example 6
The carbon nano tube and the powdered activated carbon are respectively applied to desulfurization and denitrification wastewater of a certain oil refinery, the nitrate concentration of the wastewater is 270mg/L, the adding amount of the carbon nano tube and the powdered activated carbon is 1g/L, the reaction time is 60min, after 30min of sedimentation, supernatant is taken for detection, the nitrate concentration of effluent water adsorbed by the carbon nano tube is 175mg/L, the removal rate of the nitrate is 35.2%, the nitrate concentration of effluent water adsorbed by the powdered activated carbon is 182mg/L, and the nitrate concentration is 32.6%.
Comparative example 7
The method comprises the steps of modifying commercially available zeolite with hydrochloric acid, and then applying the modified zeolite to desulfurization and denitrification wastewater of a certain oil refinery, wherein the nitrate concentration of the wastewater is 270mg/L, the adding amount of the modified zeolite is 1g/L, the reaction time is 60min, after settling for 30min, the supernatant is taken for detection, the nitrate concentration of effluent is 218mg/L, and the nitrate removal rate is 19.3%.
Comparative example 8
The method comprises the steps of preparing zinc-titanium-iron ternary hydrotalcite, applying the zinc-titanium-iron ternary hydrotalcite to desulfurization and denitrification wastewater of an oil refinery, wherein the nitrate concentration of the wastewater is 270mg/L, the sulfate concentration is 2830mg/L, the adding amount of the zinc-titanium-iron ternary hydrotalcite is 1g/L, the reaction time is 60min, after settling for 30min, taking supernate for detection, the nitrate concentration of effluent is 142mg/L, the removal rate of nitrate is 47.4%, the sulfate concentration is 2620mg/L, and the sulfate adsorption capacity is 210 mg/L.
Comparative example 9
The adsorbent prepared in example 1 is applied to low-salt wastewater, the nitrate concentration in the wastewater is 190mg/L, sulfate ions cannot be basically detected, the adding amount of the adsorbent is 0.5g/L, the reaction time is 60min, after sedimentation is carried out for 30min, supernatant is taken for detection, the nitrate concentration of effluent is 9mg/L, and the nitrate removal rate is 95.2%.
Comparative example 10
The adsorbent prepared in example 1 is applied to low-salt wastewater, the nitrate concentration in the wastewater is 190mg/L, sulfate ions cannot be basically detected, the adding amount of the adsorbent is 1g/L, the reaction time is 60min, after sedimentation is carried out for 30min, supernatant is taken for detection, the effluent nitrate concentration is 6mg/L, and the nitrate removal rate is 96.8%.
Claims (9)
1. A preparation method of a desulfurization and denitrification wastewater adsorbent is characterized by comprising the following steps: the method comprises the following steps:
stage one, preparing magnesium-iron hydrotalcite:
(1) preparation of Mg (NO) 3 ) 2 ·6H 2 O and Fe (NO) 3 ) 3 ·9H 2 Mixed salt solution A of O, NaOH and Na 2 CO 3 The mixed solution B of (1);
(2) adding deionized water into a reactor, dropwise adding the mixed salt solution A and the mixed solution B into the reactor, stirring simultaneously, and controlling the pH value of the mixed stirring liquid in the reactor to be 9-10;
(3) after the dropwise addition is finished, the slurry is subjected to heat preservation and stirring at 60 ℃, aged for 12 hours, the formed hydrotalcite is filtered and washed, and a filter cake is transferred to a crucible and dried for later use;
stage two, intercalation montmorillonite fine clay preparation:
(4) pulverizing montmorillonite raw soil to less than 50 meshes, adding into deionized water, stirring with a stirrer for 30-60 min, standing, removing montmorillonite slurry on the upper layer, and removing sand and stone on the lower layer; adjusting the pH value of the montmorillonite slurry to acidity, then heating and flocculating for 10-15 minutes, standing at room temperature, drying after centrifugal separation, and grinding to obtain montmorillonite fine soil;
(5) adding montmorillonite fine soil into deionized water, stirring, and adding 1mol/L NaCl solutionStirring the mixed solution at 65 ℃ for 2h, standing for 2h, adding 1mol/L NaCl solution, stirring at 65 ℃ for 2h, standing overnight, filtering, washing with distilled water until no Cl exists - Drying at 120 ℃, grinding, sieving with a 200-mesh sieve, and activating the product at 105 ℃ for 1-2 days to obtain sodium montmorillonite;
(6) dispersing sodium-based montmorillonite into distilled water to obtain sodium-based montmorillonite slurry for later use; respectively preparing 0.4mol/L NaOH solution and 0.2mol/L ferric trichloride solution, dripping the NaOH solution into the ferric trichloride solution, simultaneously stirring for 2-4h, aging at room temperature for 12h, pouring into sodium-based montmorillonite slurry, stirring for 4-6h, filtering, repeatedly washing with distilled water until no Cl exists - Drying at 120 ℃ to obtain the intercalated montmorillonite fine soil;
stage three, modifying intercalated montmorillonite fine clay polypyrrole:
(7) adding the fine intercalated montmorillonite clay into deionized water, stirring for 60-90min, and adding FeCl with the same mass as the fine intercalated montmorillonite clay at a temperature of 25-35 deg.C 3 Then adding pyrrole, reacting for 3-4h at 30 ℃, respectively centrifugally washing for 3-4 times by using water and acetone to obtain modified montmorillonite, and drying for later use;
and a fourth stage: high shear bonding;
(8) adding the hydrotalcite prepared in the step (3) and the modified montmorillonite prepared in the step (7) into deionized water, shearing for 60-90min by using a high-shear disperser, centrifugally washing for 3 times by using the deionized water, drying in a forced air drying box at 110 ℃, roasting a dried sample at 250-300 ℃ for 4h, and preparing the desulfurization and denitrification wastewater adsorbent;
in the step (8), the mass ratio of the hydrotalcite to the modified montmorillonite is 1: 1-4: 1;
the content of nitrate ions in the desulfurization and denitrification wastewater is 100-300ppm, and the content of sulfate ions in the desulfurization and denitrification wastewater is 2000-3000 ppm.
2. The method for preparing the adsorbent for desulfurization and denitrification wastewater according to claim 1, characterized in that: in the step (1), in the mixed salt solution A, Mg 2+ The mass concentration of the substance is 0.6-0.8mol/L, Fe 3+ The mass concentration of the substance is 0.15-0.2 mol/L; mixing ofIn the mixed solution B, Na 2 CO 3 The mass concentration of the substance is 0.3-0.4mol/L, and the mass concentration of the NaOH substance is 1.5-2 mol/L.
3. The method for preparing the adsorbent for desulfurization and denitrification wastewater according to claim 1, characterized in that: in the step (2), the dropping speed is 600-800mL/h, and the volume ratio of the deionized water to the mixed salt solution A to the mixed solution B is 2: 1: 1-2.5: 1: 1.
4. the method for preparing the adsorbent for desulfurization and denitrification wastewater according to claim 1, characterized in that: in the step (3), the drying temperature is 105 ℃, and the drying time is 12 h.
5. The method for preparing the adsorbent for desulfurization and denitrification wastewater according to claim 1, characterized in that: in the step (4), the mass ratio of the montmorillonite raw soil to the deionized water is 0.05-0.2: 1.
6. the method for preparing the adsorbent for desulfurization and denitrification wastewater according to claim 1, characterized in that: in the step (4), the granularity of the montmorillonite fine soil is less than 200 meshes.
7. The method for preparing the adsorbent for desulfurization and denitrification wastewater according to claim 1, characterized in that: in the step (5), adding the montmorillonite fine soil into deionized water to obtain a montmorillonite aqueous solution, wherein the mass ratio of the montmorillonite fine soil to the deionized water is 0.05-0.2: 1; stirring for 30min, adding 1mol/L NaCl solution, wherein the volume ratio of the NaCl solution to the montmorillonite aqueous solution is 1:1-3:1, stirring the mixed solution at 65 ℃ for 2h, standing for 2h, adding 1mol/L NaCl solution, adding the NaCl solution, stirring at 65 ℃ for 2h, standing overnight; suction filtering, washing with distilled water repeatedly until no Cl is formed - Drying at 120 deg.C, grinding, sieving with 200 mesh sieve, and activating at 105 deg.C for 1-2 days to obtain sodium montmorillonite.
8. The method for preparing the adsorbent for desulfurization and denitrification wastewater according to claim 1, characterized in that: in the step (7), the mass ratio of the intercalated montmorillonite refined soil to the deionized water is 0.05-0.2: 1.
9. the method for preparing the adsorbent for desulfurization and denitrification wastewater according to claim 1, characterized in that: in the step (7), the mass ratio of the pyrrole to the intercalated montmorillonite fine soil is 0.06-0.25: 1.
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