CN106943995B

CN106943995B - Modified clinoptilolite, preparation method and application of modified clinoptilolite in removing Pb ions in wastewater

Info

Publication number: CN106943995B
Application number: CN201710288294.6A
Authority: CN
Inventors: 闫文付; 李耀睿; 白璞
Original assignee: Changchun Xiding Technology Co ltd
Current assignee: LUOYANG JIANYANG TECHNOLOGY Co.,Ltd.
Priority date: 2017-04-27
Filing date: 2017-04-27
Publication date: 2020-11-24
Anticipated expiration: 2037-04-27
Also published as: CN106943995A

Abstract

The invention relates to a modified clinoptilolite, a preparation method and application thereof in removing Pb ions in wastewater, belonging to the technical field of wastewater purification; the modified clinoptilolite belongs to artificially synthesized clinoptilolite with low silica-alumina ratio, and the framework silica-alumina ratio n (Si/Al) = 4-4.5; then Na + exchange and roasting modification treatment are carried out on the mixture. The prepared modified clinoptilolite has good Pb-removing effect²⁺The saturated adsorption capacity of the adsorbent is up to 185 mg/g; modified clinoptilolite for Pb in the presence of other metal ions in large amounts²⁺Still exhibit strong selective adsorption. The modification method of the invention is simple and easy to implement, has large adsorption capacity and strong selectivity, and greatly improves the Pb content²⁺The treatment efficiency of wastewater.

Description

Modified clinoptilolite, preparation method and application of modified clinoptilolite in removing Pb ions in wastewater

Technical Field

The invention relates to a technology in the field of heavy metal-containing wastewater treatment, in particular to modified clinoptilolite, a preparation method and application thereof in removing Pb ions in wastewater.

Background

With the development and progress of economy, the heavy metal pollution of natural water bodies is increasingly serious. Pb is one of typical heavy metal pollutants, and the main source of Pb is Pb-containing wastewater generated in industrial activities such as electroplating, dye production and battery production. In the solution environment, Pb is mainly Pb²⁺The biological activity of the compound has strong biological toxicity, and after entering a water body, the compound can be accumulated and enriched in a human body, thereby causing serious harm to the health of the human body. Currently, the adsorption method is to remove Pb from the solution²⁺One of the main methods of (1).

The zeolite is composed of [ SiO ]₄]Tetrahedron and [ AlO₄]Three-dimensional open framework materials of tetrahedra formed by sharing oxygen atoms, wherein [ SiO ]₄]The tetrahedron is electrically neutral, and [ AlO ]₄]The tetrahedron has a negative charge and thus boilsThe whole stone framework is negatively charged, and the negative charge of the framework needs to be balanced by cations in pore channels or cages, so that the zeolite has cation exchange capacity and is suitable for removing harmful metal cations in wastewater. Clinoptilolite is one of the more common zeolites, the topological structure belongs to HEU type zeolite, and the clinoptilolite is an alkali metal aluminosilicate with three-dimensional pore channels, has an obvious lamellar crystal structure, and the pore channel structures of the clinoptilolite exist in the forms of ten-membered rings and eight-membered rings.

A great deal of research shows that clinoptilolite is used for removing Pb in wastewater²⁺One of the most potential adsorbents. However, natural clinoptilolite formed in different regions has large differences in phase, silica-alumina ratio and cation composition, and thus has a great influence on Pb²⁺The amount of adsorption of (A) is different. Inglezakis V J et al ([ 1)]Desalinization, 2007, 210(1-3): 248-256) uses Greece natural clinoptilolite to remove Pb from solution²⁺It was found that natural clinoptilolite is responsible for Pb²⁺The maximum adsorption amount of (a) is 33.8 mg/g; inglezakis V J et al ([ 2)]Water Research, 2002, 36(11): 2784-2792) uses natural clinoptilolite for Pb²⁺The maximum adsorption amount of (a) is 44.9 mg/g; sharifipour F et al ([ 3 ]]International Journal of Environmental Research, 2015, 9(3): 1001-1010) found that the maximum adsorption amount of ilolite was 24.4 mg/g. In conclusion, natural clinoptilolite produced in different regions removes Pb²⁺The performance of the catalyst has great difference, and the defects of low adsorption quantity are generally existed. Furthermore, the natural clinoptilolite n (Si/Al) is more than 5-6, while the artificially synthesized clinoptilolite n (Si/Al) reported in European patent EP0681991A1 can be controlled to be 4-4.5, and lower n (Si/Al) means more adsorption sites, but no artificially synthesized low silica-alumina ratio clinoptilolite is currently used for adsorbing Pb²⁺The patent reports of the aspect are not based on the patent reports of the modification aspect.

In conclusion, the natural clinoptilolite ore has the advantages of large composition difference, uncontrollable quality, high silicon-aluminum ratio and Pb²⁺Low adsorption capacity. The low adsorption capacity means that the dosage of the adsorbent is increased when in use, which inevitably causes the increase of solid wastes; the inconsistent quality means that the water will be treatedThe indexes of the process and the sewage bring unpredictable changes. Therefore, the development quality is stable and controllable, and Pb is²⁺Clinoptilolite adsorbent with higher adsorption capacity for removing Pb in wastewater²⁺Has important significance.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a modified clinoptilolite, a preparation method and application thereof in removing Pb ions in wastewater, and overcome the defects of large composition difference, uncontrollable quality, high silicon-aluminum ratio (n (Si/Al) = 5-6) and Pb ion of the existing natural clinoptilolite adsorbent²⁺Low adsorption capacity.

In order to solve the technical problems, the invention adopts the following technical scheme:

a modified clinoptilolite is characterized in that: modified clinoptilolite framework silica-alumina ratio n (Si/Al) =4-4.5, Na⁺The molar ratio of the total balance cations is more than 75 percent.

A preparation method of modified clinoptilolite comprises the following steps:

(1) artificially synthesizing to obtain pure-phase clinoptilolite with the silica-alumina ratio n (Si/Al) = 4-4.5; for example, pure-phase clinoptilolite can be synthesized by the method of 068 example 5 of European patent EP1991A 1;

(2) washing the artificially synthesized clinoptilolite by water by adopting a suction filtration method, and drying for later use;

(3) preparing sodium-containing solution with concentration of 1-3mol/L for later use, adding the washed and dried clinoptilolite into the sodium-containing solution for ion exchange treatment, wherein the mass ratio of the dried pure-phase clinoptilolite to the exchange solution is 1:40-1:80, and the exchange temperature is 50-80^oC, exchange time is more than or equal to 1h, Na is obtained⁺Exchanging the modified sample, washing and drying; the exchange process can be carried out under the condition of stirring, and the rotating speed is 300-500 r/min;

(4) and roasting the dried sample to obtain the modified twilled hair zeolite.

Preferably, the end point of the suction filtration washing before modification is the pH of the washing water < 9.

Preferably, the sodium source used in the sodium-containing solution can be any one of sodium chloride, sodium nitrate, sodium sulfate and sodium hydroxide or a mixture of sodium chloride, sodium nitrate, sodium sulfate and sodium hydroxide in any proportion.

Preferably, Na after exchange modification⁺The molar ratio of the total balance cations is more than 75 percent.

Preferably, the calcination temperature is 450-650^oAnd C, roasting for 1-2h in an air atmosphere.

The application of the prepared modified clinoptilolite in removing Pb ions in wastewater specifically comprises adding the modified clinoptilolite into Pb-containing materials with pH of 3-10²⁺The wastewater of (1) is subjected to stirring adsorption, standing adsorption or circulating adsorption by adjusting the dosage to remove Pb in the wastewater²⁺Ions. This variant is particularly suitable for Pb²⁺<200mg/L of wastewater system.

Modified clinoptilolite for Pb²⁺The saturated adsorption capacity of the ions is as high as 185 mg/g; modified clinoptilolite for Pb even in the presence of other metal ions in large amounts²⁺Still has excellent selective adsorption performance.

An application of modified clinoptilolite in selectively removing Pb ions from waste water is prepared by adding modified clinoptilolite into Pb-containing material with pH of 3-10²⁺Of the wastewater, Pb of the wastewater system²⁺<200mg/L, and the wastewater contains Pb equivalent to that of the wastewater²⁺Other metal cations with the molar concentration less than 10 times are stirred, adsorbed by standing or circularly adsorbed to selectively remove Pb in the wastewater²⁺。

The physicochemical characteristics of the artificially synthesized clinoptilolite can be characterized by the following methods:

1. the artificially synthesized clinoptilolite according to the method of example 5 in reference European patent EP0681991A1 was subjected to XRD detection to determine that the phase of the synthesized clinoptilolite was clinoptilolite.

2. For Na⁺And performing X-ray diffraction (XRD) analysis on the clinoptilolite before and after the double modification by roasting to determine that the structure of the clinoptilolite is not damaged after the modification.

3. Scanning electron micrographs of the clinoptilolite before and after modification are obtained to observe the change of the morphology of the clinoptilolite before and after modification.

4. X-ray fluorescence Spectroscopy (XRF) analysis of clinoptilolite before and after modification to determine the silica to alumina ratio (n (Si/Al)) and Na of clinoptilolite before and after modification⁺The degree of exchange.

These technical solutions, including the improved technical solution and the further improved technical solution, can also be combined or combined with each other, thereby achieving better technical effects.

The invention is designed based on the following technical principles: (1) artificially synthesized low silica-alumina ratio clinoptilolite has a relatively lower silica-alumina ratio, and for zeolitic materials a lower silica-alumina ratio means the presence of [ AlO ] in the framework₄]The more, [ AlO ]₄]More equilibrium cations means more equilibrium cations are needed, more equilibrium cations means more adsorption sites, and thus low silica alumina has greater adsorption capacity than clinoptilolite; (2) artificially synthesized low silica-alumina ratio clinoptilolite initial equilibrium cation with main Na⁺And K⁺In which Na⁺Generally 20% -50%. Because of K⁺The relative ionic radius is larger, so that it is not easy to react with Pb²⁺Exchange and fix K in clinoptilolite⁺Presence of (2) for adsorbing Pb²⁺Is disadvantageous in that Na having a smaller ionic radius and being very inexpensive is used first⁺Carrying out ion exchange modification on the modified product; (3) the total number of the cations in the clinoptilolite skeleton is 4, and the original existence form of the cations in the clinoptilolite skeleton can be changed by controlling the high-temperature roasting condition, so that the clinoptilolite skeleton is more favorable for Pb²⁺Adsorption of (3). Based on the above 3 points, artificially synthesized low silica-alumina ratio clinoptilolite is used and is subjected to Na⁺Exchange and high-temperature roasting modification can prepare the Pb²⁺Has high adsorption capacity and high selectivity.

By adopting the technical scheme, the invention has the following beneficial effects:

(1) the invention uses artificially synthesized low silicon-aluminum ratio (n (Si/Al) = 4-4.5) clinoptilolite instead of natural clinoptilolite with high silicon-aluminum ratio (n (Si/Al) = 5-6) as a raw material, and can improve the cation adsorption sites per unit mass.

(2) The clinoptilolite synthesized by manpower can keep the physicochemical properties of the synthesized product consistent, and has important significance for the design of water treatment process and the stability of water quality index.

(3) By simple Na⁺The exchange and high-temperature roasting double modification treatment is carried out to prepare the modified clinoptilolite with the largest Pb known at present²⁺Adsorption capacity (up to 185 mg/g), even in the presence of other metal ions in large amount, modified clinoptilolite for Pb²⁺Still has excellent selective adsorption performance.

(4) Modified oblique zeolite pair Pb²⁺Has high adsorption capacity and high selectivity, the adsorption capacity is little interfered by other metal ions, and the Pb content can be effectively improved²⁺The wastewater treatment efficiency is improved, and the generation of solid wastes is reduced.

Drawings

FIG. 1 shows the XRD spectrum of a synthetic clinoptilolite prepared by the method of example 5 in reference to European patent EP0681991A1 (corresponding to the sample S1# in example 1 of the present invention). It can be seen from FIG. 1 that the synthesized product is pure-phase clinoptilolite.

FIG. 2 shows XRD spectra of synthetic clinoptilolite before and after modification (corresponding to sample No. S3 in example 1 of the present invention). From FIG. 2 it can be seen that the passage of Na⁺After the exchange and roasting modification treatment, the sample still keeps the complete clinoptilolite structural characteristics.

Fig. 3 and 4 are scanning electron microscope images of the oblique-haired zeolite before and after modification, respectively, which correspond to S1# and S3# in example 1, respectively, and it can be seen that the modification treatment does not affect the morphology of the sample.

FIG. 5 shows clinoptilolite vs. Pb in various states²⁺The adsorption capacity of (a).

Detailed Description

The present invention will be described in detail with reference to the following examples, which will help researchers in the field to further understand the present invention, but the embodiments of the present invention are not limited thereto, and the present invention is not limited to the scope of the present invention. It should be noted that numerous modifications and adaptations can be made by those skilled in the art without departing from the spirit of the invention. All falling within the scope of the present invention.

Example 1

(1) With reference to the method of example 5 of European patent EP0681991A1, low silica to alumina ratio clinoptilolite was synthesized and washed with suction to pH<9，80^oDrying C for later use, detecting by XRF elemental analysis, and synthesizing clinoptilolite n (Si/Al) =4.1, in this case Na⁺The molar ratio of the total balance cations is 27 percent;

(2) 5g of artificially synthesized clinoptilolite was added to 400mL of 2mol/L NaCl solution, 60^oC, stirring for 2 hours at the rotating speed of 300 r/min. Then solid-liquid separation, washing and 80^oDrying C to obtain Na⁺Exchange-modified clinoptilolite, in this case Na⁺Accounting for 81 percent of the total balance cation molar ratio;

(3) mixing Na⁺The modified clinoptilolite is put into a muffle furnace in an air atmosphere of 550^oC, roasting for 2 hours to obtain the final modified slant zeolite;

for comparison, we labeled n (Si/Al) =4.1, clinoptilolite without any modification treatment as S1 #; will pass through Na only⁺Modification treatment to obtain Na⁺Clinoptilolite 81% molar of total equilibrium cations is designated as # S2; will pass through Na⁺The clinoptilolite treated by double modification and calcination is marked as S3 #. We performed adsorption capacity studies on these three clinoptilolites. Adsorption of Pb²⁺The experimental conditions were as follows:

according to the different mass ratio of clinoptilolite to absorbed liquid of 1:500, 1g of clinoptilolite is added into 500mL of Pb-containing liquid²⁺In solution of Pb²⁺Is 400mg/L, the pH of the system is adjusted =5.9, stirring is carried out at 25 ℃ for 2h at constant temperature, the rotation speed is 300 rpm. After adsorption, the solution is centrifuged (4500 rpm, 10 min) and filtered (0.45 mu m microporous filter membrane), and then Pb in the filtrate is detected²⁺Concentration, calculating the adsorbent to Pb²⁺The amount of adsorption of (3).

The results of the experiment are as follows:

as can be seen from example 1, the unmodified clinoptilolite Pb synthesized²⁺The adsorption capacity is 125 mg/g; through Na⁺Exchange-modified clinoptilolite Pb²⁺The adsorption capacity is increased to 166 mg/g; clinoptilolite Pb modified by roasting²⁺The adsorption capacity was increased to 185 mg/g. The adsorption capacity of the artificially synthesized clinoptilolite modified by the method is greatly improved.

Comparative example 1

(1) Taking natural clinoptilolite raw ore from Liaoning and Xinjiang respectively, grinding to powder, washing off easily soluble impurities on the surface, 80%^oOven drying C, wherein the product is natural clinoptilolite n (Si/Al) =5.2, Na⁺Accounts for 41 percent of the total equilibrium cation molar ratio (marked as S4 #), is produced from natural clinoptilolite n (Si/Al) =5.5 in Xinjiang, and is Na⁺49% of the total equilibrium cation molar ratio (labeled S5 #);

(2) respectively adding 5g of the above two clinoptilolite into 200mL of 3mol/L NaCl solution, 80^oC, stirring for 2 hours at the rotating speed of 300 r/min. Then solid-liquid separation, washing and 80^oDrying C to obtain Na⁺Exchange-modified clinoptilolite, natural clinoptilolite Na from Liaoning⁺83% (labeled as S6 #) of total equilibrium cation molar ratio, and is derived from natural clinoptilolite Na in Xinjiang⁺85% of the total equilibrium cation molar ratio (labeled S7 #);

(3) mixing the above two kinds of Na separately⁺The modified clinoptilolite is put into a muffle furnace in an air atmosphere of 550^oC, roasting for 2 hours to obtain the final modified clinoptilolite, wherein the modified natural clinoptilolite produced from Liaoning is marked as S8#, and the modified natural clinoptilolite produced from Xinjiang is marked as S9 #;

we performed adsorption capacity studies on the natural clinoptilolite and modified samples produced in two different regions. Adsorption of Pb²⁺The experimental conditions were the same as in example 1, as follows:

adding 1g clinoptilolite into the solution to be adsorbed according to the mass ratio of 1:500 of the clinoptilolite to the solution to be adsorbed500mL of a solution containing Pb²⁺In solution of Pb²⁺Is 400mg/L, the pH of the system is adjusted =5.9, stirring is carried out at 25 ℃ for 2h at constant temperature, the rotation speed is 300 rpm. After adsorption, the solution is centrifuged (4500 rpm, 10 min) and filtered (0.45 mu m microporous filter membrane), and then Pb in the filtrate is detected²⁺Concentration, calculating the adsorbent to Pb²⁺The amount of adsorption of (3).

The results of the experiment are as follows:

from comparative example 1, it can be seen that natural clinoptilolite is Na-passed⁺Exchanging and roasting modified Pb²⁺The adsorption capacity is greatly improved, but the adsorption capacity is still far lower than that of the modified artificially synthesized low-silica-alumina-ratio clinoptilolite; it can also be seen from comparative example 1 that there is a large difference in the amount of adsorption of clinoptilolite produced from different regions.

Example 2:

the modification procedure of example 1 was repeated except that NaNO was used for NaCl in the step (2)₃Instead. Obtaining the modified oblique-hair zeolite.

Adsorption of Pb²⁺The experimental conditions are the same as example 1, and the modified clinoptilolite is used for Pb²⁺The adsorption capacity was 181 mg/g.

Example 3:

the modification procedure of example 1 was repeated except that NaCl in the step (2) was changed to Na₂SO₄Instead of, Na₂SO₄The concentration became 1 mol/L. Obtaining the modified oblique-hair zeolite.

Adsorption of Pb²⁺The experimental conditions are the same as example 1, and the modified clinoptilolite is used for Pb²⁺The adsorption capacity was 178 mg/g.

Example 4:

pb Using modified clinoptilolite from example 1²⁺And (4) performing adsorption experiments. The main objective is to investigate different types and concentrations of cations versus Pb²⁺The effect of adsorption.

The following experiments were performed:

experiment 1: adsorption of Pb²⁺The experimental conditions were the same as those of example 1, except that 100mg/L Na was further mixed into the adsorbed solution⁺Under the condition, the modified clinopodium zeolite is used for treating Pb²⁺The adsorption capacity is 185 mg/g;

experiment 2: adsorption of Pb²⁺The experimental conditions were the same as those of example 1, except that 400mg/L Na was further mixed into the adsorbed solution⁺Under the condition, the modified clinopodium zeolite is used for treating Pb²⁺The adsorption capacity is 184 mg/g;

experiment 3: adsorption of Pb²⁺The experimental conditions were the same as those of example 1, except that 800mg/L of Na was further mixed into the adsorbed solution⁺Under the condition, the modified clinopodium zeolite is used for treating Pb²⁺The adsorption capacity is 181 mg/g;

experiment 4: adsorption of Pb²⁺The experimental conditions were the same as those of example 1, except that 2000mg/L of Na was further mixed into the adsorbed solution⁺Under the condition, the modified clinopodium zeolite is used for treating Pb²⁺The adsorption capacity is 171 mg/g;

experiment 5: adsorption of Pb²⁺The experimental conditions were the same as those of example 1, except that 200mg/L of Na was further mixed into the adsorbed solution⁺200mg/L of Zn²⁺200mg/L of Cd²⁺、200mg/L Cu²⁺Under the condition, the modified clinopodium zeolite is used for treating Pb²⁺The adsorption capacity is 171 mg/g;

as can be seen from the results of example 4, even if a large amount of interfering metal ions (experiment 4 interfering ions Na) is present⁺The concentration is Pb ²⁺5 times of concentration) or multiple metal ions exist together, the modified clinoptilolite has good Pb-removing effect²⁺The adsorption capacity is not obviously reduced yet, and the modified clinoptilolite provided by the invention is proved to have good effect on Pb²⁺Has good selective adsorption performance.

Example 5:

pb Using modified clinoptilolite from example 1²⁺And (4) performing adsorption experiments. From a plant containing Pb²⁺Waste water, Pb²⁺Concentration 55mg/L, pH = 6.7. 2g of modified clinoptilolite was charged into 1L of this wasteStirring in water at room temperature for 1h at a rotation speed of 300r/min, centrifuging (4500 rpm, 10 min), filtering (0.45 μm microporous membrane), and detecting Pb in the filtrate²⁺The concentration is 0.8mg/L, which is lower than the highest allowable discharge concentration of the first class of pollutants in the national comprehensive wastewater discharge standard (GB-8978-1996).

Claims

1. A modified clinoptilolite is characterized in that: modified clinoptilolite framework silica-alumina ratio n (Si/Al) =4-4.5, Na⁺The molar ratio of the total balance cations is more than 75 percent;

the preparation method of the modified clinoptilolite comprises the following steps:

(1) artificially synthesizing to obtain pure-phase clinoptilolite with the silica-alumina ratio n (Si/Al) = 4-4.5;

(3) preparing a sodium-containing solution with the concentration of 1-3mol/L for later use, adding the washed and dried clinoptilolite into the sodium-containing solution for ion exchange treatment at the exchange temperature of 50-80 ℃ for 1-2h to obtain Na, wherein the mass ratio of the dried pure-phase clinoptilolite to the exchange solution is 1:40-1:80⁺Exchanging the modified sample, washing and drying;

(4) baking the dried sample to obtain a modified twilled hair zeolite;

and (3) washing the artificially synthesized clinoptilolite by using water by adopting a suction filtration method in the step (2), wherein the pH value of the washing water is less than 9 at the end point of suction filtration and washing.

2. A preparation method of modified clinoptilolite is characterized by comprising the following steps: the method comprises the following steps:

(3) preparing 1-3mol/L sodium-containing solution for later use, drying, and mixing with clinoptiloliteThe mass ratio of the exchange liquid is 1:40-1:80, the washed and dried clinoptilolite is added into a sodium-containing solution for ion exchange treatment, the exchange temperature is 50-80 ℃, the exchange time is 1-2h, and Na is obtained⁺Exchanging the modified sample, washing and drying;

(4) baking the dried sample to obtain a modified twilled hair zeolite;

3. The process for preparing modified clinoptilolite according to claim 2, wherein: the exchange process is carried out under stirring.

4. The process for preparing modified clinoptilolite according to claim 3, wherein: the stirring speed is 300-500 r/min.

5. The process for preparing modified clinoptilolite according to claim 2, wherein: the sodium source used in the sodium-containing solution is any one of sodium chloride, sodium nitrate, sodium sulfate and sodium hydroxide or a mixture of sodium chloride, sodium nitrate, sodium sulfate and sodium hydroxide in any proportion.

6. The process for preparing modified clinoptilolite according to claim 2, wherein: ion exchange modified Na⁺The molar ratio of the total balance cations is more than 75 percent.

7. The process for preparing modified clinoptilolite according to claim 2, wherein: the roasting temperature is 450-650 ℃, the roasting time is 1-2h, and the roasting atmosphere is air atmosphere.

8. The application of the modified clinoptilolite in removing Pb ions in wastewater is characterized in that:

(3) preparing a sodium-containing solution with the concentration of 1-3mol/L for later use, adding the washed and dried clinoptilolite into the sodium-containing solution for ion exchange treatment at the exchange temperature of 50-80 ℃ for 1-2h to obtain a Na + exchange modified sample, washing and drying, wherein the mass ratio of the dried pure-phase clinoptilolite to the exchange solution is 1:40-1: 80; the exchange process can be carried out under the condition of stirring, and the rotating speed is 300-500 r/min;

(4) baking the dried sample to obtain a modified twilled hair zeolite;

(5) adding the modified clinoptilolite into Pb-containing material with pH of 3-10²⁺Of the wastewater, Pb of the wastewater system²⁺<200mg/L, and the wastewater contains Pb equivalent to that of the wastewater²⁺Other metal cations with the molar concentration less than 10 times are stirred, adsorbed by standing or circularly adsorbed to selectively remove Pb in the wastewater²⁺。