CN101234792B - A method for removing fluoride ions in water by aluminum oxide loaded with lanthanum oxide - Google Patents

Abstract

The invention discloses an application of aluminum oxide loaded with lanthanum oxide in removing fluorine ions in water. The invention also discloses a method for removing fluorine ions in water by using aluminum oxide loaded with lanthanum oxide, that is, the modified aluminum oxide loaded with lanthanum oxide is adsorbed to remove pollution under acidic, neutral or alkaline conditions at 20-30°C Fluoride ions in water. When the present invention adopts an adsorption method to remove fluorine pollutants in water, it exhibits significantly better adsorption performance than traditional adsorption materials. In addition, the invention has simple operation, readily available materials, low cost and remarkable treatment effect. Therefore, the invention is used to remove fluoride ions in slightly polluted source water, and has good economic and environmental benefits.

Description

A method for removing fluoride ions in water by aluminum oxide loaded with lanthanum oxide

technical field

The invention belongs to the technical field of carrier alumina and rare earth metal oxides, and in particular relates to an application of alumina loaded with lanthanum oxide to remove fluorine ions in water.

Background technique

Fluorine is an essential trace element for the human body and plays a very important role in the metabolism of teeth and bones. With the development of society, the production and use of fluorine and its compounds are increasing. An appropriate amount of fluorine is beneficial to the human body, but when the daily intake of fluoride exceeds the normal needs for a long time, it will lead to endemic fluorosis. The waste water produced by the mining and processing of fluorine-containing ore, metal smelting, aluminum electrolysis, coke, glass, electronics, electroplating, fertilizer, pesticide, chemical industry and other industries often contains high concentrations of fluoride, which causes environmental pollution after being discharged into water bodies, causing people of high attention. High fluoride content in drinking water is the most basic and important factor leading to the prevalence of endemic fluorosis. Drinking high-fluoride water for a long time can lead to dental fluorosis and skeletal fluorosis, which can cause tooth deterioration and enamel loss, and can cause bone sclerosis or osteoporosis, bone deformation, and even paralysis, making people lose their ability to work. Therefore, the treatment of fluorine-containing wastewater has become an important issue urgently needed to be solved in the field of environmental protection at home and abroad.

Traditional fluoride removal methods mainly include precipitation method, electrocoagulation method, reverse osmosis method, ion exchange method and adsorption method. Among these methods, electrocoagulation and reverse osmosis have better treatment effects, but the cost is higher; ion exchange and precipitation have poor selectivity and limited removal capacity. Therefore, the adsorption method with high efficiency, low energy consumption and easy operation has become one of the most widely used methods at present.

Adsorption is the process by which one or more molecules of a substance attach to the surface of another substance (usually a solid). Adsorption is an interface phenomenon, which is the concentration of adsorbed molecules on the interface. Usually people call activated carbon, molecular sieve, silica gel, adsorption resin and other substances with relatively large specific surface area as adsorbents, and the substances adsorbed by adsorbents are called adsorbates. In recent years, scholars generally believe that the use of adsorbents with high specific surface area to remove toxic and harmful substances in water through adsorption is one of the most effective methods for water pollution control.

Commonly used adsorbents for removing fluoride ions in water include activated alumina, activated carbon, bone charcoal and tricalcium phosphate, etc. However, the adsorption capacity of these materials is generally not high. Taking ordinary activated carbon as an example, its adsorption capacity for fluoride ions in water is less than 1mg/g. In addition, the regeneration of activated carbon materials is relatively complicated, and the applicable pH range of activated alumina is also small, which limits their application. Studies in recent years have shown that the hydrated oxides of rare earth elements and some metal elements including iron have higher adsorption capacity and better selectivity for fluoride ions, and can be used as better fluoride removal adsorbents. At the same time, in order to improve the utilization efficiency of these metals as much as possible, the preparation of fluorine adsorption materials by loading specific forms of metals on different supports has attracted people's attention. This method of making full use of surface reactions is a good solution The economic applicability of this kind of adsorbent has been discussed. Alumina is a common carrier, which is cheap and easy to obtain, and has a stable structure; lanthanum is also a relatively common rare earth element. Therefore, loading lanthanum oxide on the surface of alumina not only makes full use of the huge specific surface area and stable structure of alumina, but also makes full use of the efficient adsorption capacity of lanthanum hydrated oxides for fluorine, which has potential application prospects in the removal of fluorine. . At the same time, the method of using alumina-supported lanthanum oxide to remove fluoride ions in water has not been reported yet.

Contents of the invention

The purpose of the present invention is to improve the adsorption capacity and selectivity of the adsorbent for fluoride ions; to provide an application of aluminum oxide-loaded lanthanum oxide in removing fluoride ions in water by utilizing the properties of certain metal oxides.

Another object of the present invention is to provide a method for removing fluoride ion pollutants in water by using alumina-supported lanthanum oxide.

The purpose of the present invention can be achieved through the following measures:

An application of aluminum oxide loaded with lanthanum oxide in removing fluoride ions in water.

A method for removing fluoride ions from water by aluminum oxide loaded with lanthanum oxide, the modified aluminum oxide loaded with lanthanum oxide is placed at 20-30°C (preferably room temperature) and under acidic, neutral or slightly alkaline conditions (preferably pH5- 8) Lower adsorption (preferably 10min to 12h) to remove fluoride ions in polluted water.

The initial concentration of fluoride ions in water is 4-80mg/L. The amount of adsorbent can be adjusted according to specific conditions, preferably the mass ratio of adsorbent to slightly polluted water is 1:900-1100.

The alumina loaded with lanthanum oxide is obtained by mixing and roasting alumina and lanthanum salt, and loading lanthanum oxide on alumina; specifically: mixing alumina and lanthanum salt at a mass ratio of 1 to 4:1 and mixing them at a temperature of 170 to Calcined at 400°C, it is obtained by loading lanthanum oxide on alumina. Among them, the lanthanum salt is preferably lanthanum nitrate, which can be ground evenly during mixing, and the alumina can be pre-calcined at 450-500°C to stabilize the carrier.

The invention uses alumina-loaded lanthanum oxide as an adsorbent to adsorb and remove fluorine pollutants in water. The hydrated oxides of metal elements have high adsorption capacity and selectivity for fluoride ions; the structure of alumina is stable, and the surface is easy to modify. In order to improve the adsorption capacity of alumina for fluorine ions, the present invention modifies its surface to obtain alumina loaded with oxides of lanthanum, which can be used as an adsorbent for adsorbing and removing fluorine pollutants in water, so that it can absorb fluorine in water. The adsorption effect of ions is significantly improved.

Alumina among the present invention is comparatively common, and requires larger specific surface area; The compound of lanthanum is common lanthanum salt, is most commonly used with lanthanum nitrate.

A method for removing fluorine ions in water with aluminum oxide-supported lanthanum oxide, specifically comprising the following steps:

1. A compound of metal lanthanum is loaded on the surface of alumina to react to obtain alumina loaded with oxide of lanthanum;

2. Using aluminum oxide loaded with lanthanum oxide as an adsorbent to adsorb fluoride ions in water, the adsorption time is 12 hours, and the adsorption is carried out at room temperature;

3. The determination of fluoride ion concentration adopts the electrode method to detect the ion concentration.

Concrete surface-modified alumina, its modification method is as follows:

Vector pretreatment

The alumina was calcined at 500°C for 4h to stabilize the carrier.

Surface Metal Loading

1. Solid mixed grinding, the mass ratio of aluminum oxide and lanthanum nitrate is preferably 1 to 4:1;

2. Roast the ground product at 170-400°C for 1-3 hours;

3. The roasted product is the adsorbent for removing fluoride ions in water.

The fluoride ions in water are adsorbed by using the alumina loaded with lanthanum oxide as an adsorbent. Adsorption can be a dynamic continuous process or a static batch process. The polluted water treated by the invention is slightly polluted source water containing fluorine ions, the mass ratio of the adsorbent to the slightly polluted water is 1:900-1100, and the initial concentration range of fluoride ions is 4-80 mg/L. The adsorption time is 10min-12h, and the adsorption effect increases with time. After 8 hours of adsorption, the equilibrium was basically reached. When the loading amount was greater than 1:1, the adsorption effect was not significantly improved; but the lower the loading amount, the worse the adsorption effect.

When the present invention adopts an adsorption method to remove fluorine pollutants in water, the adsorption performance is significantly better than that of traditional adsorption materials (such as activated carbon and unmodified alumina). In addition, the invention has simple operation, readily available materials, low cost and remarkable treatment effect. Therefore, the invention is used for removing fluoride ions in slightly polluted source water, and has good environmental and economic benefits.

Detailed ways

Example 1 Alumina loaded with lanthanum oxide

Alumina is calcined at 500°C for 4 hours, mixed with lanthanum nitrate and ground for 20 to 30 minutes, the mass ratio of alumina and lanthanum nitrate is 1:1; the ground product is calcined at 170°C for 2 hours; the loaded lanthanum oxide is obtained of alumina.

Example 2 Alumina loaded with lanthanum oxide

Alumina is calcined at 500°C for 4 hours, mixed with lanthanum nitrate and ground for 20 to 30 minutes, the mass ratio of alumina and lanthanum nitrate is 2:1; the ground product is calcined at 170°C for 2 hours; the loaded lanthanum oxide is obtained of alumina.

Example 3 Alumina loaded with lanthanum oxide

Alumina is calcined at 500°C for 4 hours, mixed with lanthanum nitrate and ground for 20 to 30 minutes, the mass ratio of alumina and lanthanum nitrate is 3:1; the ground product is calcined at 170°C for 2 hours; the loaded lanthanum oxide is obtained of alumina.

Example 4 Alumina loaded with lanthanum oxide

Alumina is calcined at 500°C for 4 hours, mixed with lanthanum nitrate and ground for 20 to 30 minutes, the mass ratio of alumina and lanthanum nitrate is 4:1; the ground product is calcined at 170°C for 2 hours; the loaded lanthanum oxide is obtained of alumina.

Example 5 Alumina loaded with lanthanum oxide

Alumina is calcined at 500°C for 4 hours, mixed with lanthanum nitrate and ground for 20 to 30 minutes, the mass ratio of alumina and lanthanum nitrate is 3:1; the ground product is calcined at 250°C for 2 hours; the loaded lanthanum oxide is obtained of alumina.

Example 6 Alumina loaded with lanthanum oxide

Alumina is calcined at 500°C for 4 hours, mixed with lanthanum nitrate and ground for 20 to 30 minutes, the mass ratio of alumina and lanthanum nitrate is 3:1; the ground product is calcined at 300°C for 2 hours; the loaded lanthanum oxide is obtained of alumina.

Example 7 Alumina loaded with lanthanum oxide

Alumina is calcined at 500°C for 4 hours, mixed with lanthanum nitrate and ground for 20 to 30 minutes, the mass ratio of alumina and lanthanum nitrate is 3:1; the ground product is calcined at 400°C for 2 hours; the loaded lanthanum oxide is obtained of alumina.

Example 8

The alumina loaded with lanthanum oxide in Example 1 was used as an adsorbent to adsorb fluoride ions in water. Adsorption was performed in a closed vessel (volume 25 ml). The initial concentration of fluoride ion is 80 mg/L, pH=6, and the mass ratio of adsorbent to slightly polluted water is 1:1000. Adsorption at room temperature for 12 hours, the maximum adsorption capacity is 80.8mg/g.

In this example and the following comparative examples or examples, the adsorption amount refers to the mass of fluorine adsorbed per gram of adsorbent.

Example 9

The alumina loaded with lanthanum oxide in Example 2 was used as an adsorbent to adsorb fluoride ions in water. Adsorption was performed in a closed vessel (volume 25 ml). The initial concentration of fluoride ion is 80 mg/L, pH=6, and the mass ratio of adsorbent to slightly polluted water is 1:1000. Adsorption at room temperature for 12 hours, the maximum adsorption capacity is 58.1mg/g.

Example 10

The alumina loaded with lanthanum oxide in Example 3 was used as an adsorbent to adsorb fluoride ions in water. Adsorption was performed in a closed vessel (volume 25 ml). The initial concentration of fluoride ion is 80 mg/L, pH=6, and the mass ratio of adsorbent to slightly polluted water is 1:1000. Adsorption at room temperature for 12 hours, the maximum adsorption capacity is 42.3mg/g.

Example 11

The alumina loaded with lanthanum oxide in Example 4 was used as an adsorbent to adsorb fluoride ions in water. Adsorption was performed in a closed vessel (volume 25 ml). The initial concentration of fluoride ion is 80 mg/L, pH=6, and the mass ratio of adsorbent to slightly polluted water is 1:1000. Adsorption at room temperature for 12 hours, the maximum adsorption capacity is 33.8mg/g.

It can be seen that within a certain range, with the increase of the loaded lanthanum salt, the adsorption capacity of the adsorbent for fluoride ions increases continuously.

Example 12

The alumina loaded with lanthanum oxide in Example 5 was used as an adsorbent to adsorb fluoride ions in water. Adsorption was performed in a closed vessel (volume 25 ml). The initial concentration of fluoride ion is 80 mg/L, pH=6, and the mass ratio of adsorbent to slightly polluted water is 1:1000. Adsorption at room temperature for 12 hours, the maximum adsorption capacity is 44.1mg/g.

Example 13

The alumina loaded with lanthanum oxide in Example 6 was used as an adsorbent to adsorb fluoride ions in water. Adsorption was performed in a closed vessel (volume 25 ml). The initial concentration of fluoride ion is 80 mg/L, pH=6, and the mass ratio of adsorbent to slightly polluted water is 1:1000. Adsorption at room temperature for 12 hours, the maximum adsorption capacity is 42.3mg/g.

Example 14

The alumina loaded with lanthanum oxide in Example 7 was used as an adsorbent to adsorb fluoride ions in water. Adsorption was performed in a closed vessel (volume 25 ml). The initial concentration of fluoride ion is 80 mg/L, pH=6, and the mass ratio of adsorbent to slightly polluted water is 1:1000. After adsorption at room temperature for 12 hours, the maximum adsorption capacity is 14.8mg/g.

It can be seen that within a certain range, under the condition that the loading of lanthanum remains constant, the adsorption capacity of the adsorbent for fluoride ions decreases continuously with the increase of the reaction and calcination temperature.

Comparative example 1

Using unmodified alumina as the adsorbent, other conditions are the same as in Example 8, and the measured adsorption capacity is less than 2 mg/g.

It can be seen that the role of alumina support in the adsorption process is negligible.

Comparative example 2

With activated alumina as the adsorbent, other conditions are the same as in Example 8, and the measured adsorption capacity is 7 mg/g.

It can be seen that the ability of activated alumina to absorb and remove fluorine is quite different from that of alumina loaded with lanthanum oxide.

Comparative example 3

The alumina loaded with lanthanum oxide in Example 3 was used as an adsorbent to adsorb fluoride ions in water. The initial concentration of fluoride ions is 80 mg/L, pH=8, and other conditions are the same as in Example 8. The measured adsorption amount was 38.5 mg/g.

It can be seen that the adsorption capacity of the adsorbent for fluoride ions under alkaline conditions is equivalent to that under acidic conditions.

Claims (5)

1. the aluminum oxide of a lanthanum-carried oxide compound is removed the method for fluorion in the water, it is characterized in that with the aluminum oxide of lanthanum-carried oxide compound in 20～30 ℃ and under acid, neutrality or meta-alkalescence condition absorption remove fluorion in the polluted water; The aluminum oxide of wherein said lanthanum-carried oxide compound is: earlier aluminum oxide is carried out the roasting pre-treatment with stable carrier at 450～500 ℃, again with aluminum oxide and lanthanum nitrate by 1～4: 1 quality than mixed grinding 20～30 minutes, grinding product 170～400 ℃ of following roastings, is loaded on gained on the aluminum oxide with lanthanum-oxides.

2. method according to claim 1 is characterized in that adsorption process carries out under the condition of pH5～8.

3. method according to claim 1 is characterized in that adsorption time is 10min～12h, and temperature is a room temperature.

4. method according to claim 1, the concentration that it is characterized in that fluoride ion contaminant in the water is 4～80mg/L.

5. method according to claim 1, the mass ratio that it is characterized in that sorbent material and polluted water is 1: 900～1100.