CN101264440A - Preparation method and regeneration method of iron-modified natural STI zeolite defluoridation material - Google Patents

Abstract

The invention relates to a preparation method and regeneration method of an iron-modified natural STI zeolite defluorination material. The invention adopts a natural zeolite as a raw material, undergoes ammonium exchange, high-temperature roasting under the protection of nitrogen, and is modified by iron to obtain a natural zeolite matrix defluoridation material. The fluorine-removing material is mixed with high-fluorine water at a certain solid-to-liquid ratio, and after static adsorption for 2 hours, the fluorine content in the water can be effectively reduced to meet the national drinking water standard. The fluorine removal material prepared by the method has high mechanical strength, good fluorine removal effect, simple and time-saving operation, and low energy consumption and treatment cost. The defluoridation material prepared by the method can restore the adsorption performance after pickling and iron modification again, can be used repeatedly, and will not cause secondary pollution to drinking water.

Description

Preparation method and regeneration method of iron-modified natural STI zeolite defluoridation material

technical field

The invention relates to a preparation method and regeneration method of an iron-modified natural STI zeolite defluoridation material, belonging to the technical field of environmental protection.

Background technique

Fluorine is one of the essential trace elements for the human body. Appropriate amount of fluorine can enhance the firmness of bones and have a certain effect on preventing dental caries. However, excessive intake of fluoride can damage human health, causing dental fluorosis and skeletal fluorosis; severe cases can cause backaches and leg pains, joint stiffness, hunchback and even paraplegia; it can also lead to thyroid dysfunction and renal dysfunction. Drinking water is the main source of fluorine intake for the human body. High fluoride content in drinking water is a major problem in our country, and it is also a worldwide problem. According to statistics, about 77 million people in my country drink groundwater with excessive fluorine content, covering 27 provinces, municipalities and autonomous regions. Endemic fluorosis caused by drinking high-fluorine water has a wide range of incidence areas, many patients, and serious illnesses. It has an impact on people's health and economic development. It has become a social development problem that cannot be ignored in our country. Although our government has done a lot of work in the prevention and treatment of endemic fluorosis and the elimination of fluorine hazards, there is still a long way to go to completely cure fluorosis. It is of great significance to study economical and effective defluoridation methods.

At present, the fluorine content in drinking water sources in high-fluoride areas in my country still exceeds the specified standard (the standard for drinking water in my country stipulates that fluoride should not exceed 1.0mg/L, and in the drinking water standard recommended by the World Health Organization (WHO), the concentration of fluoride is 1.5mg/L), generally up to 3mg/L, and some areas exceed 10mg/L. At present, a lot of research has been done on the treatment of fluorine-containing water at home and abroad, and some progress has been made in the research on fluoride removal technology and related basic theories. The physical and chemical methods commonly used to remove fluoride from drinking water mainly include coagulation precipitation, adsorption filtration, chemical precipitation, reverse osmosis, electrodialysis, and electrocoagulation. Among them, adsorption filtration, reverse osmosis, and electrocoagulation have been studied more.

However, the reverse osmosis method has not been widely used in my country at present, mainly due to the high price of reverse osmosis membrane components, easy pollution, and short service life (usually only 1-3 years). Due to various factors such as economy and technology, it is not realistic for this method to be widely used in rural areas. The electrocoagulation method is used to remove fluoride from drinking water, which consumes a lot of energy and is not stable enough. It is still necessary to solve the problems of how to further improve the efficiency of fluoride removal and how to take effective measures to prevent membrane polarization scaling.

The adsorption filtration method mainly uses the adsorption, ion exchange or complexation of the adsorbent and the fluorine ion to remove the fluoride ion. However, the effect of fluoride removal is mainly restricted by the type of adsorbent. Commonly used adsorbents include activated alumina, bone charcoal, activated magnesia, fly ash, chelating resin, etc. The disadvantages are large usage, limited fluoride removal capacity, frequent regeneration, and easy to cause secondary pollution and other problems.

Contents of the invention

The purpose of the present invention is to provide a preparation method of iron-modified natural STI zeolite defluoridation material.

Another object of the present invention is to provide a regeneration method for iron-modified natural STI zeolite defluoridation material.

The purpose of the present invention is achieved through the following technical solutions.

A preparation method of iron-modified natural STI zeolite defluoridation material is characterized in that the method has the following process steps:

a. Preparation of NH ₄ -STI zeolite: exchange natural STI zeolite with 1mol/L NH ₄ Cl solution at 95°C for 3 times, each time for 2 hours, the ratio of the mass of natural STI zeolite to the volume of 1mol/L NH ₄ Cl solution 1:10 to 1:15, wherein the mass unit of STI zeolite is gram, the volume unit of NH ₄ Cl solution is milliliter, after the exchange is completed, wash and dry at 80°C to obtain NH ₄ -STI zeolite;

Preparation of bH-STII zeolite: use NH ₄ -STI zeolite to program temperature increase at a rate of 10°C/min, and roast at 500-550°C for 2-3 hours under nitrogen protection to obtain H-STI zeolite;

c. Preparation of iron-modified Fe(III)-STI zeolite: H-STI zeolite was exchanged ₃ times with 1mol/L FeCl solution at 80-90°C for 2 hours each time. _3. The volume ratio of the solution is 1:10 to 1:15, wherein the mass unit of STI zeolite is gram, and the volume unit of _FeCl3 solution is milliliter. Calcined Fe(III)-STI zeolite.

A method for regeneration of iron-modified natural STI zeolite defluoridation material, characterized in that the method has the following processes:

Exchange the Fe(III)-STI zeolite that has lost its adsorption capacity with 2mol/L HCl solution at room temperature once, 2 hours each time, wash and dry at 80°C after the exchange is completed, and then use 1mol/L FeCl ₃ solution at 80-90°C Exchange 3 times, each 2 hours, the mass of Fe(III)-STI zeolite and the volume ratio of 1mol/L _FeCl3 solution are 1: 10～1: 15, wherein the mass unit of Fe(III)-STI zeolite is Gram, the volume unit of the _FeCl3 solution is milliliters. After the exchange is completed, it is washed and dried at 80° C., and roasted at a high temperature under the protection of nitrogen to obtain a regenerated Fe(III)-STI zeolite.

The raw material used in the present invention is the abundant natural mineral CXN zeolite in my country, which has high grade, large reserves, and low mining cost. new natural mineral resources. The unit cell composition is Na _0.2 Mg _0.1 Ca _8.4 [Al _17.2 Si _54.8 O ₁₄₄ ]·65H ₂ O, and its skeleton structure contains ten-membered ring channels (along the [100] direction, 0.49nm×0.62nm) and intersecting Eight-membered ring channel (along [101] direction, 0.27nm×0.56nm), zeolite framework silicon-aluminum ratio (Si/Al=3.2). When the iron-modified STI zeolite is in contact with a fluorine-containing solution, ^F- ions diffuse into the pores of the zeolite crystal and complex with Fe ³⁺ to form FeFn ^3-n (n=1～6), thereby Its chemical adsorption ability is greatly enhanced, and at the same time Fe ³⁺ is complexed with F ^- , and other anions in drinking water such as HCO ₃ ^- , CO ₃ ^2- , SO ₄ ^2- , Cl ^- have less interference, indicating that iron modified zeolite High selectivity to ^F- .

The invention provides a preparation method of a fluoride-removing material capable of effectively removing excess fluoride in drinking water and a regeneration method thereof. High fluorine water can reach the national drinking water standard (1mg/L) after being statically adsorbed by Fe(III)-STI zeolite (2h). The fluorine removal material has low energy consumption and treatment cost, high mechanical strength and good fluorine removal effect, and the treated water is odorless, tasteless and nontoxic. The fluoride removal material has no leakage of metal ions and does not cause secondary pollution to drinking water. The Fe(III)-STI zeolite defluoridation material prepared in the present invention is used to remove fluorine-containing drinking water, and its static saturated adsorption capacity can reach 2.1 mg (fluorine ion)/g (zeolite). In the present invention, the Fe(III)-STI zeolite that has lost its adsorption capacity recovers its adsorption capacity after pickling and iron modification, and can be used repeatedly.

Description of drawings

Figure 1 is the adsorption curve of the effect of static adsorption time on the effect of fluoride removal. It can be seen that after 15 minutes, the F ^- concentration in the original fluorine water dropped from 5 mg/L to below the national drinking water standard of 1 mg/L, and the adsorption equilibrium was basically reached within 2 hours, and the fluoride ion equilibrium concentration was 0.32 mg/L. The results show that the material has a fast defluorination effect.

Figure 2 is the adsorption isotherm of iron-modified STI zeolite at different fluoride ion concentrations. The results show that the saturated adsorption capacity of the material for fluorine in drinking water is 2.1 mg/g.

Detailed ways

Below in conjunction with embodiment the present invention will be further described:

Example 1

Effect of Modified Zeolite with Different Anion Iron Salt Solutions on Fluoride Removal Effect

Different Fe(III)-STI zeolites were prepared by modifying natural mineral STI zeolites with different anion iron salt solutions. The specific preparation method of Fe(III)-STI zeolite with _FeCl3 solution as iron salt solution is as follows:

(1) Preparation of NH ₄ -STI zeolite: the natural STI zeolite was exchanged 3 times with 1mol/L NH ₄ Cl solution at 95°C (2 hours each time), the solid-liquid ratio was 1:10 (the quality of the natural STI zeolite and the 1mol/LNH ₄ Cl solution volume ratio), where the mass unit of STI zeolite is gram, and the volume unit of NH ₄ Cl solution is milliliter. After the exchange is completed, wash and dry at 80°C to obtain NH ₄ -STI zeolite.

(2) Preparation of H-STI zeolite: NH ₄ -STI zeolite was calcined at 550° C. for 2-3 hours under nitrogen protection by temperature programming (10° C./min) to prepare H-STI zeolite.

(3) Preparation of iron-modified Fe(III)-STI zeolite: H-STI zeolite was exchanged 3 times with 1mol/L FeCl solution at 80-90°C (2 hours each time) _, solid-liquid ratio 1:10 (H- The ratio of the mass of STI zeolite to the volume of 1mol/L _FeCl3 solution), wherein the mass unit of STI zeolite is gram, and the volume unit of _FeCl3 solution is milliliter. After the exchange is completed, it is washed and dried at 80 ° C. Calcined Fe(III)-STI zeolite.

With Fe(NO ₃ ) ₃ solution, Fe ₂ (SO ₄ ) ₃ solution as the method for the Fe(III)-STI zeolite prepared by iron salt solution is as described above, only the 1mol/L FeCl solution in step ( ₃ ) is respectively Replace with 1mol/L Fe(NO ₃ ) ₃ solution, Fe ₂ (SO ₄ ) ₃ solution.

Accurately weigh 1 g of Fe(III)-STI zeolite prepared after modification with different iron salt solutions, put in a plastic beaker, add 100 mL of fluorine-containing water sample with a concentration of 5.12 mg/L, stir for 2 hours, filter the clear liquid, and add TISAB The buffer solution was used to measure the fluoride ion concentration using a fluoride ion selective electrode. The effect of modified zeolite with different anion iron salts on the defluoridation effect is as follows:

Iron salt solution Concentration of original fluorine water (mg/L) Concentration after defluoridation (mg/L) Fluoride removal rate (%) _FeCl3 5.12 0.32 93.8 Fe(NO ₃ ) ₃ 5.12 3.2 37.5 Fe ₂ (SO ₄ ) ₃ 5.12 3.4 33.6

The above data show that when FeCl ₃ solution is used to modify STI zeolite, ferric ions are more likely to replace other cations on the zeolite, which improves the defluoridation effect.

Example 2

Comparison of defluoridation effect between FeCl ₃ modified STI zeolite and natural STI zeolite raw powder

The preparation steps of Fe(III)-STI zeolite are the same as in Example 1. The comparison of the defluoridation effect of FeCl ₃ modified STI zeolite and natural STI zeolite raw powder is as follows:

Adsorbent Concentration of original fluorine water (mg/L) Concentration after defluoridation (mg/L) Fluoride removal rate (%)  Unmodified STI zeolite 5.12 3.9 23.8 FeCl ₃ modified STI zeolite 5.12 0.32 93.8

The above data show that after ferric ions replace other cations on the zeolite, FeFn ^3-n (n=1-6) is formed due to the complexation between ferric ions and fluorine ions, which greatly enhances its chemical adsorption capacity. The adsorption capacity of the adsorbent is greatly increased.

Example 3

Comparison of Static Adsorption Capabilities of Different Adsorbents for Fluoride-Containing Drinking Water

Iron-modified natural HEU zeolite was used together with commercially available activated alumina, amorphous alumina, activated carbon, calcite, clay, charcoal, fuller's earth, and red mud as comparative adsorbents.

The comparison results of the adsorption capacity of different adsorbents for fluoride-containing drinking water are shown in the following table:

Adsorbent Adsorption capacity (mg/g) Activated alumina 2.4 Amorphous alumina 3.6 activated carbon 1.1 Calcite 4.37×10 ^-5 clay 7.09 charcoal 7.88×10 ^-5 fuller's earth 7.75 red mud ^6.2810-3 Iron modified HEU zeolite ＜1.0 Iron-modified STI zeolite (the present invention) 2.1

The formula for calculating the adsorption capacity is as follows:

$\mathrm{<span\; class="notranslate">\; qe</span>}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; co</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; Ce</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; W</span>}}<span\; class="notranslate">\; \&CenterDot;</span>\mathrm{<span\; class="notranslate">\; V</span>}$

Where: initial fluoride ion concentration in Co-solution (mg/L)

Fluoride ion concentration at equilibrium in Ce-solution (mg/L)

V-solution volume (L)

W-adsorbent mass (g)

qe- Adsorption capacity of adsorbent per unit mass of adsorbate at adsorption equilibrium (mg/g)

Considering the market price and adsorption capacity of the adsorbent comprehensively, the fluoride removal material of the present invention has low energy consumption and treatment cost, good fluoride removal effect, and excellent cost performance among existing drinking water fluoride removal materials.

Example 4

Fluoride removal effect of 1g iron-modified STI zeolite dose on 100mL (solid-to-liquid ratio 1:100) drinking water with different concentrations of fluoride

The preparation steps of Fe(III)-STI zeolite are the same as in Example 1.

Concentration of original fluorine water (mg/L) Adsorption capacity (mg/g) Fluoride removal rate (%) 5 0.46 93.8 10 0.87 91.1 15 1.18 85.7 30 1.98 82.6

The above data show that the material with a dose of 1 gram has a good defluoridation effect on low-fluorine drinking water (<30mg/L). The treated drinking water is odorless, tasteless and non-toxic. According to ICP-AES detection, there is basically no leakage of metal ion Fe ³⁺ in the adsorbent, and it will not cause secondary pollution to drinking water. Increasing the dosage of iron-modified STI zeolite can remove high-fluorine drinking water.

Example 5

Regeneration Test of Fe(III)-STI Zeolite Adsorbent

After the Fe(III)-STI zeolite that has lost its adsorption capacity is exchanged once (2 hours) at room temperature with 2mol/L HCl solution, after the exchange is completed, it is washed and dried at 80°C, and then exchanged with 1mol/L FeCl _solution at 80-90°C 3 times (2 hours each time), the ratio of the mass of Fe(III)-STI zeolite to the volume of 1mol/ _L FeCl solution is 1:10, wherein the mass unit of Fe(III)-STI zeolite is gram, _FeCl solution The unit of volume is milliliter. After the exchange is completed, it is washed and dried at 80° C., and roasted at high temperature under the protection of nitrogen to obtain the regenerated Fe(III)-STI zeolite. The above process and the fluorine removal test of Example 1 were repeated, and the results showed that after two regenerations, the adsorbent still had good adsorption performance (the fluorine removal rate was greater than 90%).

Claims (2)

1. the preparation method of an iron modified natural STI zeolite defluorination material is characterized in that this method has following processing step:

A.NH ₄-STI prepare zeolite: natural STI zeolite 1mol/L NH ₄Cl solution is at 95 ℃ of exchanges 3 times, each 2 hours, the quality of natural STI zeolite and 1mol/L NH ₄The ratio of the volume of Cl solution is 1: 10～1: 15, and wherein the mass unit of STI zeolite is gram, NH ₄The volume unit of Cl solution is a milliliter, and exchange is finished the back and washed and obtain NH 80 ℃ of oven dry ₄-STI zeolite;

B.H-STII prepare zeolite: with NH ₄-STI zeolite adopts temperature programming, and programming rate is 10 ℃/min, obtains the H-STI zeolite in 2～3 hours 500～550 ℃ of roastings under nitrogen protection;

C. iron MODIFIED Fe (III)-STI prepare zeolite: H-STI zeolite 1mol/LFeCl ₃Solution is at 80～90 ℃ of exchanges 3 times, each 2 hours, the quality of H-STI zeolite and 1mol/LFeCl ₃The ratio of the volume of solution is 1: 10～1: 15, and wherein the mass unit of STI zeolite is gram, FeCl ₃The volume unit of solution is a milliliter, and exchange is finished the back and washed and 80 ℃ of oven dry, make Fe (III)-STI zeolite through high-temperature roasting under nitrogen protection.

2. the renovation process of an iron modified natural STI zeolite defluorination material is characterized in that this method has following technology:

To lose Fe (the III)-STI zeolite of adsorption capacity and 2mol/LHCl solution room temperature exchange 1 time, each 2 hours, exchange was finished the back and is washed and 80 ℃ of oven dry, use 1mol/LFeCl again ₃Solution is at 80～90 ℃ of exchanges 3 times, each 2 hours, the quality and the 1mol/LFeCl of Fe (III)-STI zeolite ₃The ratio of the volume of solution is 1: 10～1: 15, and wherein the mass unit of Fe (III)-STI zeolite is gram, FeCl ₃The volume unit of solution is a milliliter, and exchange is finished back washing and 80 ℃ of oven dry, made Fe (the III)-STI zeolite of regenerating through high-temperature roasting under nitrogen protection.

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