CN114699802A - Method for desorbing, enriching and recovering Cd/Pb step by step - Google Patents

Method for desorbing, enriching and recovering Cd/Pb step by step Download PDF

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CN114699802A
CN114699802A CN202210450744.8A CN202210450744A CN114699802A CN 114699802 A CN114699802 A CN 114699802A CN 202210450744 A CN202210450744 A CN 202210450744A CN 114699802 A CN114699802 A CN 114699802A
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CN114699802B (en
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毛娟
钱璐
许海亮
吴晓晖
余华东
张利虹
陆谢娟
周涛
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Zhejiang Hi Tech Environmental Technology Co ltd
Huazhong University of Science and Technology
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Huazhong University of Science and Technology
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Abstract

The invention belongs to the technical field of metal wastewater pollution treatment and recovery, and particularly relates to a method for desorbing, enriching and recovering Cd/Pb step by step. Hair brushThe method for desorbing, enriching and recovering Cd/Pb step by step is provided by adsorbing Cd2+And Pb2+The first step of the method is to desorb the Cd adsorbed in the adsorbent sample by using the solubility difference between lead sulfate and cadmium sulfate2+Is preferentially desorbed, and Pb2+The generated surface micro-precipitate is not desorbed; then adopting ammonium acetate aqueous solution as desorbent, stirring and making second-step desorption, utilizing Pb2+Good solubility in ammonium acetate solution, desorbing the un-desorbed Pb in the adsorbent after the first step2+Elution and stepwise desorption can realize stepwise enrichment and separate mass recovery of Cd/Pb.

Description

Method for desorbing, enriching and recovering Cd/Pb step by step
Technical Field
The invention belongs to the technical field of metal wastewater pollution treatment and recovery, and particularly relates to a method for desorbing, enriching and recovering Cd/Pb step by step.
Background
Cadmium and lead are heavy metals with strong toxicity, the electroplating wastewater often contains cadmium and lead metal ions at the same time, and the untreated cadmium and lead-containing wastewater discharged into water can cause serious harm and hidden danger to water ecological systems and human life safety. With the continuous development of the electroplating industry, the consumption of raw materials is larger and larger, the recoverable resources are less and less, the recovery of cadmium and lead is beneficial to environmental protection, and the recovery consumption of non-renewable mineral resources can be relieved. Therefore, the method has important significance for efficiently separating, enriching, separating and recycling the cadmium and the lead in the wastewater. At present, the treatment methods of the wastewater containing cadmium and lead mainly include a precipitation method, a membrane separation method, an ion exchange method and an adsorption method, wherein the adsorption method can realize the separation of metal ions in the wastewater from a solution through adsorption, and can also perform concentration and enrichment on the adsorbed metal ions through desorption.
Chitosan has many advantages of environmental protection, biodegradability, wide and easily available sources, low cost and the like, but the solubility of chitosan under acidic conditions limits the application range of chitosan, and the adsorption capacity of original chitosan is limited. However, the chitosan surface contains a large amount of hydroxyl and amino with high reaction activity, so that the functional modification is convenient, and the chitosan-based adsorbing material with high adsorption quantity, good selectivity, high mechanical strength and good regeneration performance can be prepared, thereby making up for the defects. The chitosan is rich in carboxyl, amino and hydroxyl through group modification, and the ion exchange and complexing adsorption capacity of metal cadmium, lead and the like is improved, so that the chitosan can be applied to adsorption removal treatment of heavy metal ions in wastewater.
Because of the similar properties of cadmium and lead metals, the two metals can be adsorbed by the adsorbent at the same time, so that the two metals adsorbed by the adsorbent are eluted at the same time, further separation, enrichment and quality-based recovery are difficult to perform, and in addition, the method for recovering metals by adsorption and desorption is usually only used for metal ions in a single metal element solution, such As Kinetics, thermynamics, and enrichment of As (III), Cd (II), Cu (II) and Pb (II) adsorption and utilization of copper ions-supported MnFe2O4Synthesis of novel chitosan-polyethylene glycol bead-loaded MnFe in nanoparticules2O4The porous nano composite material of nano particles can be used as a high-efficiency adsorbent to remove metals (As (III)) and heavy metals (Cd (II), Cu (II) and Pb (II)) in an aqueous solution, and NaOH is used for desorbing the solution containing only a single element during desorption. The phosphoalkylated chitosan/CoFe literature2O4The composition for the efficient removal of Pb (II) and Cd (II) from aqueous solution the phosphorylation properties and mechanism fractions have synthesized the phosphorylated magneticThe chitosan composite material (P-MCS) is applied to adsorbing Pb (II) and Cd (II) in an aqueous solution, hydrochloric acid is adopted during desorption, and Pb (II) and Cd (II) are eluted. A good method for separating, enriching and recycling the waste water containing cadmium and lead according to quality is not provided.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a method for desorbing, enriching and recovering Cd/Pb step by step, which solves the technical problems that the prior art cannot realize step by step desorption, quality-based recovery and the like after simultaneously adsorbing cadmium and lead in wastewater.
In order to realize the aim, the invention provides a method for desorbing, enriching and recovering Cd/Pb step by step, which comprises the following steps:
(1) will adsorb Cd2+And Pb2+The adsorbent sample is mixed with the aqueous solution of sulfuric acid, stirring is carried out for first-step desorption, and the difference of the solubility of lead sulfate and cadmium sulfate is utilized to ensure that Cd adsorbed in the adsorbent sample2+Is preferentially desorbed, and Pb2+Is not desorbed to obtain the adsorbent and Cd after the first desorption step2+Desorbing the enriched liquid;
(2) mixing the adsorbent desorbed in the first step in the step (1) with an ammonium acetate aqueous solution, stirring for desorption in the second step, and using Pb2+Solubility in ammonium acetate solution to allow the non-desorbed Pb in the adsorbent after the first desorption2+Is eluted to obtain Pb2+Desorbing the enriched liquid to realize the stepwise enrichment and the quality-classified recovery of Cd/Pb.
Preferably, the Cd is adsorbed in the step (1)2+And Pb2+The adsorbent is capable of adsorbing Cd by electrostatic action2+And Pb2+The adsorbent of (1).
Preferably, the adsorbent sample in the step (1) is adsorbed with Cd2+And Pb2+The modified chitosan adsorbent of (1) is more preferably used for adsorbing Cd2+And Pb2+Saturated modified chitosan adsorbent is achieved.
Preferably, the modified chitosan adsorbent is obtained by performing carboxylation modification on chitosan.
Preferably, the concentration of the aqueous solution of sulfuric acid in the step (1) is 0.05-0.2M, the stirring speed is 150-180rpm, and the stirring time is 6-12 h.
Preferably, the concentration of the aqueous solution of ammonium acetate in the step (2) is 3-4M, the stirring speed is 150-180rpm, and the stirring time is 6-12 h.
Preferably, Cd is adsorbed to the adsorbent before the first desorption in step (1)2+And Pb2+The adsorbent sample of (a) is washed with water.
Preferably, the preparation of the modified chitosan adsorbent comprises the following steps:
dissolving chitosan powder by using acetic acid to prepare chitosan gel;
step two, injecting chitosan gel into an alkali solution for solidification to form fibers;
step three, placing the fiber in a cross-linking agent solution, and performing cross-linking reaction under the condition of strong alkali control to obtain cross-linked chitosan fiber;
and step four, performing carboxyl modification on the crosslinked chitosan fibers in an acidic modification solution, and washing and drying to obtain the modified chitosan adsorbent.
Preferably, the acidic modification solution in the fourth step is a halogenated carboxylic acid or oxalic acid modification solution, and the oxalic acid modification solution is obtained by performing carboxyl activation on an oxalic acid solution by using 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide.
Generally, compared with the prior art, the above technical solution conceived by the present invention has the following beneficial effects:
(1) the invention provides a method for desorbing, enriching and recovering Cd/Pb step by step, which adsorbs Cd2+And Pb2+The first step of desorbing the adsorbent sample by using an aqueous solution of sulfuric acid, and making use of the solubility difference between lead sulfate and chromium sulfate to adsorb Cd in the adsorbent sample2+Is preferentially desorbed, and Pb2+Is not desorbed; then adoptAmmonium acetate aqueous solution as desorbent, stirring for second desorption, and using Pb2+Good solubility in ammonium acetate solution, and the un-desorbed Pb in the adsorbent after the first desorption2+Eluted to realize the stepwise enrichment and the separate recycling of Cd/Pb.
(2) The method for desorbing, enriching and recovering Cd/Pb step by step is suitable for various Cd-adsorbed materials2+And Pb2+In particular by electrostatic adsorption of Cd2+And Pb2+The adsorbent of (1). In the preferred embodiment of the invention, the modified chitosan is used as the adsorbent to adsorb Cd2+And Pb2+The adsorbent sample is desorbed, and the experimental result shows that the desorption rate of Cd (II) in the first step is about 100.6%, the desorption rate of Pb (II) is 4.5%, the desorption rate of Cd (II) in the second step is 0, and the desorption rate of Pb (II) is 90.4%. By two-step desorption of sulfuric acid-ammonium acetate, the stepwise enrichment of Cd (II) and Pb (II) can be realized, and the purities of Cd (II) and Pb (II) after quality-divided recovery are respectively as follows: 92.6% and 100%.
Drawings
FIG. 1 is a flow chart of the present invention for Cd (II) and Pb (II) desorption, enrichment and recovery step by step.
FIG. 2 is a graph showing the effect of sulfuric acid solution concentration on Cd (II) desorption in example 1.
FIG. 3 is a graph showing the effect of ammonium acetate concentration on Pb (II) desorption effect in example 2.
Figure 4 is the data for the two-step desorption results of example 3.
FIG. 5 shows the data of the two-step desorption results of example 4.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The invention provides a method for desorbing, enriching and recovering Cd/Pb step by step, which comprises the following steps as shown in figure 1:
(1) will adsorb Cd2+And Pb2+The adsorbent sample is mixed with the aqueous solution of sulfuric acid, stirring is carried out for the first desorption, and the difference of the solubility of lead sulfate and chromium sulfate is utilized to ensure that Cd adsorbed in the adsorbent sample2+Is preferentially desorbed, and Pb2+The generated surface micro-precipitation is not desorbed, and the adsorbent and Cd after the first desorption step are obtained2+Desorbing the enriched liquid;
(2) mixing the adsorbent desorbed in the first step in the step (1) with an ammonium acetate aqueous solution, stirring for desorption in the second step, and using Pb2+Good solubility in ammonium acetate solution, and good solubility in Pb in the adsorbent after the first desorption2+Is desorbed to obtain Pb2+Desorbing the enriched liquid to realize the stepwise enrichment and the quality-classified recovery of Cd/Pb.
The stepwise desorption-enrichment recovery method is suitable for various adsorption wastewater Cd2+And Pb2+The adsorbent of (1). In a preferred embodiment, the Cd adsorbed in the step (1)2+And Pb2+The adsorbent is an adsorbent sample capable of adsorbing Cd by electrostatic action2+And Pb2+The adsorbent of (1).
In some embodiments, the adsorbent sample of step (1) is adsorbed with Cd2+And Pb2+The modified chitosan adsorbent is preferably used for adsorbing Cd2+And Pb2+The saturated modified chitosan adsorbent is obtained.
In some embodiments, the modified chitosan adsorbent is a modified chitosan adsorbent obtained by performing carboxyl modification on chitosan. The modified chitosan adsorbent can be prepared by adopting the prior art to perform carboxylation modification on chitosan so that the surface of the chitosan is rich in hydroxyl, amino and carboxyl functional groups, and the modified chitosan adsorbent is used as an adsorbent to adsorb Cd in wastewater through electrostatic action2+And Pb2+. In some embodiments, the modified chitosan adsorbent is prepared by the following steps:
dissolving chitosan powder by using acetic acid to prepare chitosan gel;
step two, injecting chitosan gel into an alkali solution for solidification to form fibers;
step three, placing the fiber in a cross-linking agent solution, and performing cross-linking reaction under the condition of strong alkali control to obtain cross-linked chitosan fiber;
and step four, performing carboxyl modification on the crosslinked chitosan fibers in an acidic modification solution, and washing and drying to obtain the modified chitosan adsorbent.
In some embodiments, the volume fraction of acetic acid in step one is 2-4%, and the mass fraction of chitosan gel is 4-6%; spraying the fiber in the second step into 0.8-1.2M NaOH solution through a 0.6-0.8mm needle under 0.5-0.7MPa to form fiber, and soaking for 10-24h to solidify the fiber; the cross-linking agent in the third step is preferably Ethylene Glycol Diglycidyl Ether (EGDE), the molar ratio of the EGDE to the chitosan monomer is 1:1-1.4:1, and the cross-linking is carried out for 2-4h at the temperature of 40-50 ℃.
In some embodiments, the crosslinked fiber filaments are placed in a halogenated carboxylic acid solution and modified at 75-85 ℃ for 6-8h, and the modification pH is maintained at 8.0-8.5; the halogenated carboxylic acid is preferably chloroacetic acid, and the mass ratio of the modifier chloroacetic acid to the chitosan is 1:8-16: 1; sodium carbonate is used to maintain the modified pH to 8.0-8.5. The surface of the modified chitosan adsorbent contains a large number of hydroxyl, amino and carboxyl functional groups, has good adsorption performance on Cd (II) and Pb (II), and is easy to desorb by nitric acid to realize multiple regeneration and cyclic utilization; chitosan molecules and chains are combined through ether bonds to form a stable structure, so that the acid resistance is good; the stepwise enrichment and the quality-classified recovery of Cd (II) and Pb (II) can be realized by a stepwise desorption method. The preparation method of the adsorbent is simple, low in cost, clean, environment-friendly, free of secondary pollution, good in performance and easy to regenerate.
In other embodiments, the acidic modifying solution in step four is an oxalic acid modifying solution activated by carboxyl, and the preparation method of the oxalic acid modifying solution includes the following steps: preparing oxalic acid solution with the concentration of 0.1-0.2M, adjusting the pH of the solution to 2.5-2.9 by alkali, sequentially adding 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide, and carrying out carboxyl activation on the oxalic acid solution to obtain oxalic acid modified solution.
In some embodiments, the concentration of the aqueous solution of sulfuric acid in step (1) is 0.5M-2M, the stirring speed is 150-180rpm, and the stirring time is 6-12 hours.
In some embodiments, the concentration of the aqueous solution of ammonium acetate in step (2) is 3M-4M, the stirring speed is 150-180rpm, and the stirring time is 6-12 hours.
In some embodiments, Cd is adsorbed to the adsorbent before the first desorption step (1) is performed2+And Pb2+The adsorbent sample is cleaned by water to remove residual cadmium ions and lead ions on the surface, so that interference on the second step of desorption sample measurement analysis is prevented.
The invention provides a stepwise desorption method capable of enriching and recovering Cd/Pb, which can realize stepwise enrichment and recovery of Cd/Pb by a simple two-step desorption method and has important significance for treatment of heavy metal wastewater and resource protection.
The following are examples:
example 1
Preparing a modified chitosan fiber adsorbent: dissolving 1g of chitosan powder in 3% acetic acid by volume fraction to prepare 5% chitosan gel by mass fraction; spraying chitosan gel into about 1.0M NaOH solution through a needle head of about 0.7mm under the constant air pressure of 0.6MPa to form fibers, and curing for about 12 h; firstly, carrying out crosslinking reaction on cellosilk and Ethylene Glycol Diglycidyl Ether (EGDE) at a molar monomer ratio of 1:1.3 at 40 ℃; dissolving 14g of chloroacetic acid to prepare 200mL of solution, putting the crosslinked chitosan into the solution, reacting for 8 hours at 80 ℃, and maintaining the modified pH to 8.0-8.5 by using sodium carbonate; finally, the modified chitosan fiber adsorbent can be prepared by washing and drying.
One-step desorption of Cd (II) under unit solution: taking 0.02g of modified chitosan fiber adsorbent, and adding 30mL of cadmium nitrate solution with the concentration of 250mg/L for adsorption; oscillating at the rotating speed of 160rpm at the temperature of 25 ℃ for 24 hours, wherein the adsorption capacity of Cd (II) in the solution is 50 mg/g; after the modified chitosan fiber adsorbent which is saturated in adsorption is washed by deionized water, 25mL of sulfuric acid desorption liquid with the concentration of 0.01M-0.5M is added, the desorption is completed after the reaction is carried out for 12h at the temperature of 25 ℃ at the rotating speed of 160rpm, the experimental result of the influence of the concentration of the sulfuric acid solution on the desorption rate of Cd (II) is shown in figure 2, the desorption rates are all maintained to be more than 90%, the concentration of sulfuric acid is continuously increased, and the desorption rate is slightly reduced. In conclusion, 0.1M sulfuric acid solution is selected as the first-step desorption solution to ensure a good enough desorption effect.
Example 2
Preparation of modified chitosan fiber adsorbent the procedure of example 1 was followed.
Fractional desorption under pb (ii) unit system: taking 0.02g of modified chitosan fiber adsorbent, and adding 30mL of lead nitrate solution with the concentration of 250mg/L into the modified chitosan fiber adsorbent; oscillating at the rotating speed of 160rpm at the temperature of 25 ℃ for 24 hours, wherein the adsorption quantity of Pb (II) in the solution is 67 mg/g; after the modified chitosan fiber adsorbent subjected to adsorption saturation is washed by deionized water, 25mL of sulfuric acid desorption solution with the concentration of 0.1M is added firstly, the reaction is carried out at the rotating speed of 160rpm for 12h at the temperature of 25 ℃ to complete the first-step desorption, the concentration of Pb (II) after the desorption is completed is only 4.5mg/L, and the desorption rate of Pb (II) is 16.67%; after the modified chitosan fiber adsorbent after the first desorption step is cleaned, 25mL of ammonium acetate desorption solution with different concentrations is added, the reaction is carried out at the rotating speed of 160rpm for 12 hours at the temperature of 25 ℃, the influence of the concentration of the ammonium acetate solution on the desorption result of Pb (II) is shown in figure 3, and the desorption rate is gradually increased along with the gradual increase of the concentration of the ammonium acetate, so that the ammonium acetate aqueous solution is a better desorption solution. However, although the desorption rate of 2M ammonium acetate is the highest, the desorption rate is 25%, and thus the desorption rate of ammonium acetate at a concentration of 2M or less is poor.
Example 3
Preparing a modified chitosan fiber adsorbent: dissolving 0.5g of chitosan powder in 3% acetic acid by volume fraction to prepare 5% chitosan gel by mass fraction; spraying chitosan gel into about 1.0M NaOH solution through a needle head of about 0.7mm under the constant air pressure of 0.6MPa to form fibers, and curing for about 12 h; firstly, carrying out crosslinking reaction on cellosilk and Ethylene Glycol Diglycidyl Ether (EGDE) at the temperature of 40 ℃ according to the molar monomer ratio of 1: 1.2; preparing oxalic acid modified solution: preparing oxalic acid solution with the concentration of 0.15M, adjusting the pH of the solution to about 2.70 by using alkali, adding 0.5g of 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride, and then adding 1g of N-hydroxysuccinimide to react for 15min at 37 ℃ and 160 rpm; then adding the crosslinked fiber filaments cleaned by clear water into the oxalic acid modified solution to react for 20 hours at 37 ℃ and 160 rpm; finally, washing and drying to obtain the modified chitosan fiber adsorbent.
Fractional desorption under a Cd (II), Pb (II) binary mixed system: taking 0.02g of modified chitosan fiber adsorbent, and adding 30mL of lead nitrate and cadmium nitrate solutions with the concentrations of 250 mg/L; reacting at 25 ℃ at the rotating speed of 160rpm for 24 hours, wherein the adsorption capacity of Cd (II) and Pb (II) in the binary mixed solution is 1.46mg/g and 230.00mg/g respectively; after the modified chitosan fiber adsorbent which is saturated in adsorption is washed by deionized water, 25mL of sulfuric acid desorption solution with the concentration of 0.1M is added firstly, and the reaction is carried out for 12 hours at the rotating speed of 160rpm at the temperature of 25 ℃ to finish the first-step desorption, wherein the desorption rate to Cd (II) is about 102.0 percent, and the desorption rate to Pb (II) is 2.3 percent; after the modified chitosan fiber adsorbent subjected to desorption in the first step is washed, 25mL of ammonium acetate desorption solution with the concentration of 2M-5M is added, the reaction is carried out for 12 hours at the temperature of 25 ℃ at the rotating speed of 160rpm, the desorption rate of Cd (II) is 0 at the moment, the two-step desorption result data are shown in figure 4, it can be seen that the desorption rate in the second step gradually increases along with the gradual increase of the ammonium acetate concentration, and the desorption rate begins to decrease again after the concentration exceeds 4M, so that the high-concentration ammonium acetate can destroy the space structure of the fiber filaments. In summary, a 3-4M ammonium acetate solution was chosen as the desorbent for the second step to ensure a sufficiently good desorption.
Example 4
Preparing a modified chitosan fiber adsorbent: dissolving 1g of chitosan powder in 3% acetic acid by volume fraction to prepare 5% chitosan gel; spraying chitosan gel into about 1.0M NaOH solution through a needle head of about 0.7mm under the constant air pressure of 0.6MPa to form fibers, and curing for about 12 h; firstly, carrying out crosslinking reaction on cellosilk and Ethylene Glycol Diglycidyl Ether (EGDE) at the temperature of 40 ℃ according to the molar monomer ratio of 1: 1.2; dissolving 14g chloroacetic acid to prepare 200mL solution, putting the crosslinked chitosan into the solution, reacting for 7 hours at 80 ℃, and maintaining the modified pH to 8.0-8.5 by using sodium carbonate; finally, the modified chitosan fiber adsorbent can be prepared by washing and drying.
Fractional desorption under a Cd (II), Pb (II) binary mixed system: taking 0.02g of modified chitosan fiber adsorbent, and adding 30mL of lead nitrate and cadmium nitrate solutions with the concentrations of 250 mg/L; reacting at 25 ℃ at the rotating speed of 160rpm for 24 hours, wherein the adsorption capacity of Cd (II) and Pb (II) in the binary mixed solution is 67mg/g and 128mg/g respectively; after the modified chitosan fiber adsorbent after saturated adsorption is washed by deionized water, 25mL of sulfuric acid desorption solution with the concentration of 0.1M is added firstly, and desorption is carried out at the rotating speed of 160rpm for 12h at the temperature of 25 ℃ to finish the first-step desorption, wherein the desorption rate of Cd (II) is about 98.0 percent, and the desorption rate of Pb (II) is 4.4 percent; after the modified chitosan fiber adsorbent after the first desorption step is cleaned, 25mL of ammonium acetate desorption solution with the concentration of 3M is added, the reaction is carried out for 12 hours at the temperature of 25 ℃ and the rotating speed of 160rpm, the desorption rate of Cd (II) is 0, the desorption rate of Pb (II) is 90.4 percent, and the data of the two-step desorption result is shown in figure 5. By two-step desorption of sulfuric acid-ammonium acetate, the stepwise enrichment of Cd (II) and Pb (II) can be realized, and the purities of Cd (II) and Pb (II) after quality-divided recovery are respectively as follows: 92.6% and 100%.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (9)

1. A method for desorbing, enriching and recovering Cd/Pb step by step is characterized by comprising the following steps:
(1) will adsorb Cd2+And Pb2+The adsorbent sample is mixed with the aqueous solution of sulfuric acid, stirring is carried out for first-step desorption, and the difference of the solubility of lead sulfate and cadmium sulfate is utilized to ensure that Cd adsorbed in the adsorbent sample2+Is preferentially desorbed, and Pb2+Is not desorbed to obtain the adsorbent and Cd after the first desorption2+Desorbing the enrichment liquid;
(2) mixing the adsorbent desorbed in the first step in the step (1) with an ammonium acetate aqueous solution, stirring for desorption in the second step, and using Pb2+Solubility in ammonium acetate solution to allow the non-desorbed Pb in the adsorbent after the first desorption2+Is eluted to obtain Pb2+Desorbing enriched liquidThe present Cd/Pb is enriched step by step and recovered by separate quality.
2. The enrichment recovery method according to claim 1, wherein the Cd adsorbed in the step (1)2+And Pb2+The adsorbent is capable of adsorbing Cd by electrostatic action2+And Pb2+The adsorbent of (1).
3. The enrichment recovery method according to claim 1, wherein the adsorbent sample in the step (1) is adsorbed Cd2+And Pb2+The modified chitosan adsorbent is preferably used for adsorbing Cd2+And Pb2+The saturated modified chitosan adsorbent is obtained.
4. The enrichment recovery method according to claim 3, wherein the modified chitosan adsorbent is a modified chitosan adsorbent obtained by performing carboxylation modification on chitosan.
5. The enrichment recovery method according to claim 1, wherein the concentration of the aqueous solution of sulfuric acid in step (1) is 0.05-0.2M, the stirring speed is 150-180rpm, and the stirring time is 6-12 h.
6. The enrichment recovery method according to claim 1, wherein the concentration of the aqueous solution of ammonium acetate in step (2) is 3-4M, the stirring speed is 150-180rpm, and the stirring time is 6-12 h.
7. The enrichment recovery method according to claim 1, wherein Cd is adsorbed to the adsorbent before the first desorption step of step (1)2+And Pb2+The adsorbent sample of (a) is washed with water.
8. The enrichment recovery method of claim 4, wherein the preparation of the modified chitosan adsorbent comprises the steps of:
dissolving chitosan powder by using acetic acid to prepare chitosan gel;
step two, injecting chitosan gel into an alkali solution for solidification to form fibers;
step three, placing the fiber in a cross-linking agent solution, and performing cross-linking reaction under the condition of strong alkali control to obtain cross-linked chitosan fiber;
and step four, performing carboxyl modification on the crosslinked chitosan fibers in an acidic modification solution, and washing and drying to obtain the modified chitosan adsorbent.
9. The enrichment recovery method according to claim 8, wherein the acidic modified solution in the fourth step is a halogenated carboxylic acid or an oxalic acid modified solution obtained by carboxyl-activating an oxalic acid solution with 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide.
CN202210450744.8A 2022-04-27 2022-04-27 Method for desorbing, enriching and recovering Cd/Pb step by step Active CN114699802B (en)

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