WO2016187796A1 - Preparation method and use of heavy metal ion adsorbent - Google Patents

Abstract

The present invention relates to the technical field of high-molecular material modification, and especially relates to a preparation method and a use of a heavy metal ion adsorbent. The preparation method for the adsorbent comprises the following steps: (1) formulating an aqueous solution of aldehyde group sodium alginate, adding a polyethylene polyamine for reaction, then adding sodium borohydride for reduction, and continuing the reaction so as to obtain amino sodium alginate; and (2) adding a mixed solution of carbon disulfide and sodium hydroxide to the solution obtained after the reaction in step (1), continuing the reaction until carbon disulfide droplets in the solution have disappeared, stopping the reaction, adding an alcohol solvent for precipitating a product, standing and layering, separating the precipitate precipitated at the bottom layer, and drying same so as to obtain the heavy metal ion adsorbent. The adsorbent has a strong adsorptivity to heavy metal ions, and desorption efficiency is improved.

Description

Preparation method of heavy metal ion adsorbent and application thereof

The present application claims priority from Chinese Patent Application No. 201510262299.2, entitled "Preparation of a Heavy Metal Ion Adsorbent and Its Application", the entire contents of which are incorporated by reference. In this application.

Technical field

The invention relates to the technical field of polymer material modification, in particular to a preparation method of heavy metal ion adsorbent and application thereof.

Background technique

Of the many pollutants in the water, heavy metal ions are the most harmful. Modern medical research has shown that some heavy metal ions can cause cancer, teratogenicity and chromosomal mutations in humans, and the incubation period can reach several decades. There are tens of thousands of electroplating enterprises in China. The output of heavy metal ions in wastewater is huge. The incident of heavy metal ion pollution has occurred in China. Many enterprises have weak treatment of heavy metal ions and exceeded the standards. Therefore, there are huge hidden dangers of environmental damage.

Current methods for treating heavy metal ion wastewater include ion exchange, membrane separation, electrochemical, chemical, and biological methods. Although these methods can remove heavy metal ions to varying degrees, they have their own advantages and disadvantages. The main problem is that the equipment is complicated and the running cost is high. The chemical law has high drug costs, the first-level discharge is difficult to meet the standard, and the waste is difficult to handle, causing secondary pollution. The use of metal flocculant to adsorb heavy metal ions is simple and effective, and the treatment effect is ideal. The flocculation effect of organic nanoflocculant is ten or even dozens larger than that of traditional inorganic salt flocculant, and it has the advantages of simple use and fast sedimentation speed. , low dosage, low processing cost, high efficiency, and so on.

Sodium alginate is a natural polymer composed of a linear copolymer of mannose and gulose, and is widely found in various brown seaweeds. Sodium alginate has a very unique property, soluble in water and with many divalent metal cations in water such as: Pb ²⁺ , Cu ²⁺ , Hg ²⁺ , Cd ²⁺ , Co ²⁺ , Ni ²⁺ , Zn ²⁺ , Mn ²⁺ , Sr ²⁺ , Ba ²⁺ , and Ca ²⁺ react to form a gel which precipitates from water. The mechanism is that the hydroxyl group in the molecular structural unit of sodium alginate acts synergistically with the carboxyl group to form a chelate structure like the "egg shell" with the metal ion. Even for very dilute concentrations of metal ions, such reactions can occur, which are not found in other natural polymeric flocculants and synthetic flocculants.

In order to improve the adsorption performance of sodium alginate, it needs to be structurally modified to maximize the adsorption of heavy metal ions and improve its ability to treat wastewater.

Summary of the invention

In order to solve the above technical problems, an object of the present invention is to provide a method for preparing a heavy metal ion adsorbent and an application thereof, and to modify a sodium alginate to introduce a chelating group having a strong adsorption capacity for heavy metal ions in a molecule. Further enhance the adsorption of heavy metal ions and improve the efficiency of removing heavy metal ions.

The preparation method of the heavy metal ion adsorbent proposed by the invention comprises the following steps:

(1) The aldehyde-based sodium alginate is formulated into an aqueous solution, and the reaction with polyethene polyamine is added, followed by reduction with sodium borohydride, and the reaction is continued to obtain amino sodium alginate;

(2) adding a mixed solution of carbon disulfide and sodium hydroxide to the solution in the step (1), continuing the reaction until the carbon disulfide droplets disappear in the solution, stopping the reaction, adding an alcohol solvent to precipitate the product, and allowing to stand. The layers were separated, and the precipitate obtained by the bottom chromatography was separated, and after drying, a heavy metal ion adsorbent was obtained.

Further, in the step (1), the mass percentage of the aldehyde-based sodium alginate in the aqueous solution is 5.8%.

Further, the polyethene polyamine includes any one or more of ethylenediamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

Further, in the step (1), the mass of the polyethene polyamine is 1-3 times the mass of the oxidized sodium alginate, and the mass of the sodium borohydride is 60% of the mass of the aldehyde-based alginate.

Further, in the step (1), the reaction temperature of the aldehyde-based sodium alginate and the polyethene polyamine is 40 ° C, and the reaction time is 24 h.

Further, in the step (2), a mixed solution of carbon disulfide and sodium hydroxide is formed by mixing an equal volume of carbon disulfide with a 30% by mass aqueous sodium hydroxide solution, and the mass ratio of the amino alginate to the carbon disulfide is 1. : 0.8 to 1.2.

Further, in the step (2), the alcohol solvent comprises any one or more of methanol, absolute ethanol, and isopropanol in an amount of three times the volume of the reactant solution.

Further, the reaction temperature in the step (2) is 40 °C.

Further, the preparation process of the aldehyde-based sodium alginate in the step (1) comprises the steps of dispersing sodium alginate in anhydrous ethanol, preparing a dispersion having a mass percentage of 15 to 20%, and then adding 0.8 mol / L sodium periodate aqueous solution, sodium periodate and sodium alginate mass ratio of 1:0.4 ~ 1, after the light-proof reaction, add ethylene glycol to terminate the reaction, the quality of ethylene glycol is sodium alginate 22.5% of the aldehyde-based sodium alginate was obtained after washing and drying.

The invention also provides an application of a heavy metal ion adsorbent for treating industrial sewage containing heavy metal ions and adsorbing heavy metal ions in the sewage.

By the above scheme, the present invention has at least the following advantages: the raw material used in the present invention is derived from the natural product ammonium alginate, which is inexpensive and has few modification steps; the modified sodium alginate has a functional amino group and a thiocarboxylate group. Group, these two groups have strong capture ability for heavy metal ions, large adsorption capacity, high removal rate, high speed, and improved adsorption efficiency.

The above description is only an overview of the technical solutions of the present invention, and the technical means of the present invention can be more clearly understood and can be implemented in accordance with the contents of the specification. Hereinafter, the preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

DRAWINGS

The drawings described herein are provided to provide a further understanding of the invention and constitute the application. In part, the illustrative embodiments of the invention and the description thereof are intended to be illustrative of the invention and are not intended to limit the invention. In the drawing:

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an infrared spectrum diagram of OSA-NH ₄ -CS-1 in the first embodiment of the present invention.

detailed description

The invention will be described in detail below with reference to the drawings in conjunction with the embodiments.

Example 1

Preparation of adsorbent OSA-NH ₄ -CS-1

Add 100 mL of absolute ethanol to 20 g of sodium alginate (SA) powder, stir evenly with magnetic stirring, add 100 mL of sodium periodate (NaIO ₄ ) solution with a concentration of 0.8 mol/L, and react at room temperature for 12 h in the dark, add 4.5 mL. Ethylene glycol, continue to react for 2h. The solution was suction filtered, and the product was washed thoroughly with 50% ethanol, suction filtered, and twice. The obtained product was dried in an oven at 55 ° C for 24 h to give an aldehyde-based sodium alginate (OSA).

5 g of OSA was mixed into 80 mL of water to form a homogeneous solution, 80 mL of a 1 mol/L tetraethylenepentamine aqueous solution was added, and the reaction was magnetically stirred in a 40 ° C water bath for 24 hours, and then cooled to room temperature. 3.02 g of NaBH _{4 was} added in portions, and the reaction was continued for 24 hours to obtain amino sodium alginate.

In the solution after the above reaction, a mixed solution of CS ₂ and NaOH is added, and the mixed solution is prepared by mixing 4 g of CS ₂ and 5 mL of 30% NaOH solution, and the reaction temperature is 40 ° C, and the reaction is continued until there is no CS ₂ droplet in the solution. . The reaction was stopped, ethanol was added in an amount of 3 times the volume of the reactant solution, and the mixture was allowed to stand overnight. The precipitate obtained by bottom chromatography was dried in an oven at 50 ° C for 24 hours to obtain a heavy metal ion adsorbent. The product mass was 6.64 g, and it was named OSA-NH _{4 .} -CS-1.

Fig. 1 is an infrared analysis spectrum of the above heavy metal ion adsorbent. The absorption peak at a wavenumber of 3350 cm ^-1 is a NH stretching vibration of an amino group in a polyethene polyamine; the absorption peak at 1601 cm ^-1 and 1422 cm ^-1 is thio The characteristic peak of the carboxylic acid and the infrared spectrum confirmed the successful synthesis of the modified sodium alginate.

The chemical reaction equation is as follows.

Example 2

Preparation of adsorbent OSA-NH ₄ -CS-2

100 mL of absolute ethanol was added to 18 g of sodium alginate (SA) powder, and the mixture was uniformly dispersed by magnetic stirring. 263 mL of a sodium periodate (NaIO ₄ ) solution having a concentration of 0.8 mol/L was added, and the reaction was carried out at room temperature for 12 hours in the dark, and 4.1 mL was added. Ethylene glycol, continue to react for 2h. The solution was suction filtered, and the product was washed thoroughly with 50% ethanol, suction filtered, and twice. The obtained product was dried in an oven at 55 ° C for 24 h to give an aldehyde-based sodium alginate (OSA).

5 g of OSA was mixed into 80 mL of water to form a homogeneous solution. 34 mL of a 1 mol/L aqueous solution of triethylenetetramine was added, and the reaction was magnetically stirred in a 40 ° C water bath for 24 hours, and then cooled to room temperature. 3.02 g of NaBH _{4 was} added in portions, and the reaction was continued for 24 hours to obtain amino sodium alginate.

In the solution after the above reaction, a mixed solution of CS ₂ and NaOH is added, and the mixed solution is thoroughly stirred by mixing 6 g of CS ₂ and 7.5 mL of a 30% NaOH solution, and the reaction temperature is 40 ° C, and the reaction is continued until there is no CS ₂ liquid in the solution. drop. The reaction was stopped, methanol was added in an amount of 3 times the volume of the reactant, and the mixture was allowed to stand overnight. The precipitate obtained by bottom chromatography was dried in an oven at 50 ° C for 24 hours to obtain a heavy metal ion adsorbent. The product mass was 5.21 g and was named OSA-NH ₄ - CS-2.

Example 3

Preparation of adsorbent OSA-NH ₄ -CS-3

Add 100 mL of absolute ethanol to 25 g of sodium alginate (SA) powder, stir evenly under magnetic stirring, add 183 mL of sodium periodate (NaIO ₄ ) solution with a concentration of 0.8 mol/L, and react at room temperature for 12 h in the dark, add 5.6 mL. Ethylene glycol, continue to react for 2h. The solution was suction filtered, and the product was washed thoroughly with 50% ethanol, suction filtered, and twice. The obtained product was dried in an oven at 55 ° C for 24 h to give an aldehyde-based sodium alginate (OSA).

5 g of OSA was mixed into 80 mL of water to form a homogeneous solution. 53 mL of a 1 mol/L tetraethylenepentamine aqueous solution was added, and the reaction was magnetically stirred in a 40 ° C water bath for 24 hours, and then cooled to room temperature. 3.02 g of NaBH _{4 was} added in portions, and the reaction was continued for 24 hours to obtain amino sodium alginate.

In the solution after the above reaction, a mixed solution of CS ₂ and NaOH is added, and the mixed solution is prepared by mixing 5 g of CS ₂ and 6.25 mL of 30% NaOH solution, and the reaction temperature is 40 ° C, and the reaction is continued until there is no CS ₂ liquid in the solution. drop. The reaction was stopped, isopropanol was added in an amount of 3 times the volume of the reactant solution, and the mixture was allowed to stand overnight. The precipitate obtained by bottom chromatography was dried in an oven at 50 ° C for 24 hours to obtain a heavy metal ion adsorbent, and the product mass was 7.56 g, which was named OSA- NH ₄ -CS-3.

Taking the adsorbent (OSA-NH ₄ -CS-1) obtained in the first embodiment as an example, the heavy metal ions commonly found in the sewage are adsorbed, and the adsorption capacity and adsorption conditions of the adsorbent are investigated.

In order to compare the adsorption effect, an adsorbent containing no thiocarboxylate was synthesized and named as the adsorbent reference sample. The mixed solution of CS ₂ and NaOH was not added during the synthesis of the adsorbent. The other synthetic conditions were The first embodiment is the same. Table 1 is a comparison of the sorbent reference sample with the results of the preparation of OSA-NH ₄ -CS-1 in Example 1.

Table 1 Comparison of the synthesis results of two adsorbents

OSA-NH ₄ -CS-1, adsorbent reference sample and sodium alginate were used to adsorb Pb ²⁺ , and 1.0 g of the above three adsorbents were respectively taken and disposed as an aqueous solution of 1% by mass, respectively. 5 mL, 10 mL, 15 mL, and 20 mL of the aqueous solution were added to 50 mL of a 5 mmol/L Pb(NO ₃ ) ₂ solution, shaken for 20 min (120 r/min), centrifuged for 15 min (4000 r/min), and 10 mL of the supernatant was taken. Add 1 mL of hexamethylenetetramine-hydrochloric acid buffer solution (pH=6.11), use 0.2% xylenol orange solution as indicator, titrate with 9.97mmol/L EDTA solution, test the concentration of Pb ^{2+ in the} solution, calculate the pair Pb ²⁺ removal rate and adsorption rate.

It can be seen from Table 2 that the modified adsorbent OSA-NH ₄ -CS-1 has higher adsorption capacity and removal rate for lead ions than the sodium alginate before modification (Table 2 shows the removal rate in parentheses). The apparent increase is improved, and the adsorption capacity of OSA-NH ₄ -CS-1 is higher than that of the adsorbent reference sample, indicating that the introduction of thiocarboxylate is a key factor for increasing the adsorption rate.

Table 2 Effect of different adsorbents on Pb ²⁺ adsorption capacity (mmol/g)

Further, OSA-NH ₄ -CS-1 and sodium alginate were used to adsorb Cd ²⁺ , and Cd(NO ₃ ) _{2 was used} instead of Pb(NO ₃ ) ₂ . The procedure was the same as the step of adsorbing Pb ²⁺ , and the adsorbent was measured. As for the adsorption performance of Cd ²⁺ , it can be seen from Table 3 that compared with sodium alginate, the adsorption performance of OSA-NH ₄ -CS-1 on Cd ²⁺ in solution is greatly improved.

Table 3 Effect of different adsorbents on Cd ²⁺ adsorption capacity (mmol/g)

R: removal rate; Q: adsorption capacity

The initial concentration of metal ions in the solution affects the adsorption of the adsorbent. Therefore, we investigated the effects of different concentrations of Pb ²⁺ solution on the adsorption of different adsorbents. Pb(NO ₃ ) ₂ solutions with concentrations of 5.0, 10.0, 20.0, 40.0, 50.0 (mmol/L) were prepared, each taking 50 mL, and 10 mL of OSA-NH ₄ -CS-1 solution (1%, w/w) was added. After shaking for 20 min (120 r/min), centrifuge for 15 min (4000 r/min), take 2 parts of 10 mL of supernatant, test the concentration of Pb ^{2+ in the} solution, calculate the removal rate and adsorption rate of Pb ^{2+ by the} adsorbent. In the same manner, sodium alginate solution (1%, w/w) was used as a comparison, and the results were compared. It can be seen from Table 4 that as the concentration of Pb ²⁺ increases, the adsorption of the adsorbent tends to be saturated, and the adsorption amount tends to be stable. The saturated adsorption capacity of OSA-NH ₄ -CS-1 is higher than that of SA, indicating that the adsorption performance of the modified adsorbent is better than that of sodium alginate. When the metal ion removal rate is low, the Pb ²⁺ concentration is lower. The effect is better.

Table 4 Effect of initial concentration of Pb ²⁺ on adsorption

R: removal rate; Q: adsorption capacity

The pH of the solution is very important for the adsorption effect. After the OSA-NH ₄ -CS-1 solution is added to different Pb(NO ₃ ) ₂ solutions, the pH of the solution is adjusted, and the removal rate and adsorption capacity of the adsorbent for Pb ²⁺ ions are measured. The results are shown in Table 5. As can be seen from the table, the adsorption performance of the adsorbent did not differ much between pH 5-6.

Table 5 Effect of solution pH on adsorption performance

Sample serial number	Solution pH	R (%)	Q (mmol/L)
				1	4	6.4	0.16
2	5	10.6	0.26
				3	6	39.7	0.99
4	7	73.60	1.83
				5	8	90.4	2.25
6	9	96.40	2.40
				7	10	96.40	2.40

In summary, the present invention prepares a heavy metal ion adsorbent by modifying sodium alginate. The source of sodium alginate is abundant, the price is cheap, the modification step is small, the product is convenient to use, and the post-treatment is easy, no secondary Contaminated, environmentally friendly; the adsorbent has a large number of amino groups, thiocarboxylates and other groups, these two groups have strong capture ability for heavy metals, large adsorption capacity, high removal rate, fast speed, plus The carboxyl group in the sodium alginate structure of Shanghai has synergistic effects to form a chelate with heavy metal ions. Therefore, it has a good adsorption effect on heavy metal ions, and is applied to the treatment of sewage, which is simple in operation and low in cost. The heavy metal residual ratio is low; the heavy metal ion adsorbent has higher adsorption capacity, larger adsorption capacity, and wider pH range than the existing sodium alginate, so it is suitable for a wide range of applications.

The above description is only the preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes can be made to the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and scope of the present invention are intended to be included within the scope of the present invention.

Claims (10)

1. A method for preparing a heavy metal ion adsorbent, comprising: the following steps:

   (1) The aldehyde-based sodium alginate is formulated into an aqueous solution, and the reaction with polyethene polyamine is added, followed by reduction with sodium borohydride, and the reaction is continued to obtain amino sodium alginate;

   (2) adding a mixed solution of carbon disulfide and sodium hydroxide to the solution in the step (1), continuing the reaction until the carbon disulfide droplets disappear in the solution, stopping the reaction, adding an alcohol solvent to precipitate the product, and allowing to stand. The layers were separated, and the precipitate obtained by the bottom chromatography was separated, and after drying, a heavy metal ion adsorbent was obtained.
2. The method for preparing a heavy metal ion adsorbent according to claim 1, wherein in the step (1), the mass percentage of the aldehyde-based sodium alginate in the aqueous solution is 5.8%.
3. The method for preparing a heavy metal ion adsorbent according to claim 1, wherein the polyethene polyamine comprises any one of ethylenediamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine. Kind or more.
4. The method for preparing a heavy metal ion adsorbent according to claim 1, wherein in the step (1), the mass of the polyethene polyamine is 1 to 3 times that of the mass of the oxidized sodium alginate. The mass of sodium borohydride is 60% of the mass of aldehyde-based sodium alginate.
5. The method for preparing a heavy metal ion adsorbent according to claim 1, wherein in the step (1), the reaction temperature of the aldehyde-based sodium alginate and the polyethene polyamine is 40 ° C, and the reaction time is 24 h. .
6. The method for preparing a heavy metal ion adsorbent according to claim 1, wherein in the step (2), the mixed solution of carbon disulfide and sodium hydroxide is composed of an equal volume of carbon disulfide and a mass percentage of 30%. The aqueous solution of sodium hydroxide is mixed, and the mass of sodium amino alginate and carbon disulfide is 1:0.8 to 1.2.
7. The method for preparing a heavy metal ion adsorbent according to claim 1, wherein in the step (2), the alcohol solvent comprises any one of methanol, absolute ethanol, and isopropanol. A variety of amounts of three times the volume of the reactant solution.
8. The method for preparing a heavy metal ion adsorbent according to claim 1, wherein the reaction temperature in the step (2) is 40 °C.
9. The method for preparing a heavy metal ion adsorbent according to claim 1, wherein the preparation process of the aldehyde-based sodium alginate in the step (1) comprises the steps of dispersing sodium alginate in anhydrous ethanol. , formulated into a mass percentage of 15-20% dispersion, and then added 0.8mol / L sodium periodate aqueous solution, the quality of sodium periodate and sodium alginate is 1:0.4 ~ 1, in the dark Thereafter, the reaction was terminated by adding ethylene glycol, and the mass of the ethylene glycol was 22.5% of sodium alginate. After washing and drying, an aldehyde-based sodium alginate was obtained.
10. An application of a heavy metal ion adsorbent, characterized in that the heavy metal ion adsorbent according to any one of claims 1 to 9 is used for the treatment of industrial sewage containing heavy metal ions, and adsorbs heavy metal ions in the sewage.

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