CN101920189A - Preparation method of modified titanium dioxide nanofiber self-regenerating adsorbent - Google Patents

Abstract

The invention relates to a preparation method of a modified titanium dioxide nanofiber self-regenerating adsorbent. In the method, the titanium dioxide nanofiber is immersed in a hydrofluoric acid aqueous solution, and the silicon on the surface of the titanium dioxide is removed by acid corrosion, and nitric acid is added after the dipping corrosion is completed. The aqueous solution is used to wash and increase the acidity of the fiber surface, and after washing, it is dried and then cooled to room temperature for later use. The adsorbent obtained by the invention has dual functions of adsorption and degradation, high adsorption capacity, fast adsorption speed, easy regeneration, and excellent adsorption capacity after self-regeneration.

Description

Preparation method of modified titanium dioxide nanofiber self-regenerating adsorbent

technical field

The invention relates to a preparation method of a modified titanium dioxide nanofiber self-regenerating adsorbent, belonging to the technical field of organic wastewater treatment.

Background technique

The printing and dyeing industry is a large discharge of industrial wastewater. The concentration of dyes in the wastewater is about 400-500 mg/L. After the traditional coagulation treatment, the concentration of the discharge is still 30-40 mg/L, which is relatively high. Dyes are difficult to biodegrade due to complex aromatic groups, and the removal rate of COD by biological treatment is usually less than 50%. The chroma of water-soluble printing and dyeing wastewater can be as high as tens of thousands to hundreds of thousands. Although chemical reduction or anaerobic biological treatment can destroy the chromophoric groups in dyes and decolorize, some of the reduced products are easy to return to color under aerobic conditions. In terms of standard discharge and recycling of printing and dyeing wastewater, the traditional water treatment process has been severely challenged.

The use of adsorption to treat printing and dyeing wastewater has good application prospects, but after the traditional adsorbents enrich the dyes on the surface, follow-up treatment is required, and the "automatic" degradation of the dyes cannot be achieved, and the problem cannot be fundamentally solved. During the adsorption process, dyes will block the effective adsorption pores of the adsorbent, reduce the specific surface area, and reduce the adsorption capacity, so the regeneration of the adsorbent must be considered. At present, the regeneration methods of adsorbent mainly include heating method, oxidation method, biological regeneration and other methods. Among them, the heating method requires more complicated equipment and higher operating costs; the oxidation method is prone to secondary pollution, and the equipment used must be corrosion-resistant and high-pressure resistant. ; The biological regeneration method takes a long time.

Contents of the invention

Aiming at the shortcomings of traditional adsorbent regeneration methods that are complicated and require high conditions, the purpose of the present invention is to provide a method for preparing a modified titanium dioxide nanofiber self-regenerating adsorbent, and the adsorbent obtained by the method has good adsorption for water-soluble dyes Effect, self-regeneration and direct degradation of dyes can be achieved, and it can be realized under the excitation of indoor fluorescent lamps or weak light such as morning light and twilight.

The present invention is achieved through the following technical solutions:

The preparation method of modified titanium dioxide nanofiber self-regenerating adsorbent comprises the following steps:

(1) Prepare a certain concentration of hydrofluoric acid aqueous solution and nitric acid aqueous solution;

(2) Immerse the pretreated titanium dioxide nanofibers doped with silicon in hydrofluoric acid aqueous solution for a certain period of time, and then wash them with nitric acid aqueous solution;

(3) Put the washed titanium dioxide nanofibers into an oven to dry, remove the residual moisture in the titanium dioxide nanofibers, and then cool them down.

The mass fractions of the hydrofluoric acid aqueous solution and the nitric acid aqueous solution are 1.5%-2.5% and 5%-7% respectively.

The concentration of the titanium dioxide nanofibers in the hydrofluoric acid aqueous solution is 0.05g/L.

The amount of the nitric acid aqueous solution is 2 to 2.5 times the volume of the hydrofluoric acid aqueous solution.

The immersion time in the hydrofluoric acid aqueous solution in step (2) is 1-2 hours, and the washing is 3-5 times.

The drying temperature in step (3) is 120-200° C., and the drying time is 1-3 hours.

The titanium dioxide nanofibers used in the modified titanium dioxide nanofiber self-regenerating adsorbent are pretreated by doping with silicon, that is, the organic silicon reagent is mixed into the fiber at a ratio equivalent to 15% silicon dioxide by mass (see patent CN1584156A ). The pretreated titanium dioxide nanofibers doped with silicon are immersed in hydrofluoric acid aqueous solution, and the silicon on the surface of titanium dioxide is removed by acid corrosion, so as to increase the specific surface area and facilitate the occurrence of photosensitization reaction. After the immersion corrosion is completed, nitric acid aqueous solution is added for washing and acidification, after washing, drying is carried out, and then cooled to room temperature.

After the adsorption of the dye is completed, the modified titanium dioxide nanofibers are taken out from the regenerated adsorbent and drained. Under the excitation of indoor fluorescent lamps or natural visible light including morning light and twilight, effective photosensitivity can be produced between the titanium dioxide nanofibers and the dye molecules. The chemical reaction produces active oxygen species with strong oxidative properties, and completes the self-regeneration of the adsorbent while degrading the dye. After that, the regenerated adsorbent is washed with water, dried, and placed in a desiccator for later use.

The present invention has the following advantages:

1. The preparation process is short, the raw materials are easy to obtain, the required equipment is simple, and the energy consumption is low;

2. In addition to printing and dyeing wastewater, it can also be used for adsorption treatment of other organic wastewater, and has dual functions of adsorption and degradation.

3. The adsorbent can realize self-regeneration through photosensitization, the light source requirement is low, the regeneration process does not require any equipment or reagents, the regeneration is easy, and the regeneration efficiency is greatly improved;

4. High adsorption capacity, fast adsorption speed, strong adsorption capacity after self-regeneration, and good regeneration performance.

Detailed ways:

The present invention will be further described below:

Example 1:

The modified titania nanofiber self-regenerating adsorbent was prepared by the following method:

(1) Prepare respectively a hydrofluoric acid aqueous solution with a mass fraction of 1.5% and a nitric acid aqueous solution with a mass fraction of 5%;

(2) Weigh 1 g of titanium dioxide nanofibers that have been pretreated with silicon doping and put them into a polytetrafluoroethylene container, add 20 mL of hydrofluoric acid aqueous solution with a mass fraction of 1.5%, stir continuously during the injection, and mix well; the mixture is placed in a dark place Stand still for 90 minutes, during this process, the silicon on the surface of titanium dioxide is removed by acid corrosion, and a rich pore structure and a large specific surface area are obtained;

(3) Take out the fibers obtained in the above steps, and wash them with a 5% nitric acid aqueous solution; when washing, first place the titanium dioxide nanofibers in a polytetrafluoroethylene container, take 40 mL of the nitric acid aqueous solution, slowly pour it into the container, and immerse After the fibers are pulled up and down repeatedly to make the dilute nitric acid fully contact with the fibers, the aqueous solution of nitric acid can dilute the aqueous solution of hydrofluoric acid to achieve the purpose of washing residual hydrofluoric acid and controlling the high acidity of the surface. The amount of hyponitrate aqueous solution is 40mL;

(4) Dry the washed fibers in an oven to remove residual moisture in the titanium dioxide fibers. The drying temperature is 150°C, the drying time is 2 hours, and cooled to room temperature.

Example 2:

Preparation method of modified titanium dioxide nanofiber self-regenerating adsorbent:

(1) Prepare a hydrofluoric acid aqueous solution with a mass fraction of 2.5% and an aqueous nitric acid solution with a mass fraction of 7%;

(2) Weigh 1 g of titanium dioxide nanofibers that have been pretreated with silicon doping and put them into a polytetrafluoroethylene container, add 20 mL of hydrofluoric acid with a mass fraction of 2.5%, stir continuously during the injection, and mix well; Place it for 90 minutes, desilicate and increase the specific surface area through acid corrosion;

(3) Take out the fibers obtained in the above steps, and wash them with a 7% nitric acid aqueous solution; when washing, first place the titanium dioxide nanofibers in a polytetrafluoroethylene container, take 50 mL of the nitric acid aqueous solution, slowly pour it into the container, and immerse After the fibers are pulled up and down repeatedly to make the dilute nitric acid fully contact with the fibers, the aqueous solution of nitric acid can dilute the aqueous solution of hydrofluoric acid to achieve the purpose of washing. Method Washing 5 times, each time the amount of nitric acid aqueous solution is 50mL.

Example 3:

Adsorption test of the modified titanium dioxide nanofiber self-regenerating adsorbent of the present invention on water-soluble printing and dyeing wastewater:

Reactive dye X-3B was used to prepare simulated wastewater solutions with a concentration of 40 mg/L, and static adsorption experiments were carried out at room temperature. Each time, 100 ml of wastewater with different initial concentrations was placed in a 150 ml evaporating dish, and modified Titanium dioxide nanofiber self-regenerating adsorbent 0.4g, magnetic stirring for 15min under dark conditions, so that the modified titanium dioxide nanofiber self-regenerating adsorbent can fully adsorb the dye, the adsorption amount is 8.4mg/g, and the adsorption removal rate can reach 84%.

A simulated wastewater solution with a concentration of 30 mg/L was prepared with the basic dye malachite green, and a static adsorption experiment was carried out at room temperature. 100ml of the simulated wastewater solution was placed in a 150ml evaporating dish, and 0.4g of modified titanium dioxide nanofibers were added, protected from light. After magnetic stirring for 15 minutes under the same conditions, the calculated adsorption capacity was 6.15 mg/g, and the adsorption removal rate could reach 82%.

After completing the adsorption of the dye, the modified titanium dioxide nanofibers were taken out from the regenerated adsorbent and drained. Under the excitation of low-intensity visible light such as indoor fluorescent lamps or natural light, photosensitization occurs, and the dye adsorbate adsorbed on the surface of the modified titanium dioxide nanofiber is mineralized and self-regenerated. After regeneration, wash the adsorbent with deionized water for 3 to 5 times until the solution becomes neutral, then dry it in an oven at 110°C for 2 hours, and cool it to room temperature for later use. After the modified titanium dioxide nanofiber self-regenerating adsorbent is used continuously for 7 times, the adsorption removal rate is 77%-80%, indicating that the adsorbent has stable adsorption performance and good regeneration performance.

Claims (5)

1. the preparation method of modified titania nanofiber self-regenerating adsorbent is characterized in that, comprises the steps: (1) Prepare a certain concentration of hydrofluoric acid aqueous solution and nitric acid aqueous solution; (2) Immerse the pretreated titanium dioxide nanofibers doped with silicon in hydrofluoric acid aqueous solution for a certain period of time, and then wash them with nitric acid aqueous solution; (3) Put the washed titanium dioxide nanofibers into an oven to dry, remove the residual moisture in the titanium dioxide nanofibers, and then cool them down. 2. according to the preparation method of the modified titania nanofiber self-regenerating adsorbent according to claim 1, it is characterized in that, the mass fractions of described hydrofluoric acid aqueous solution and nitric acid aqueous solution are respectively 1.5%～2.5% and 5%～ 7%. 3. according to the preparation method of the modified titanium dioxide nanofiber self-regenerating adsorbent of claim 1, it is characterized in that, the concentration of described titanium dioxide nanofiber in hydrofluoric acid aqueous solution is 0.05g/L, and described nitric acid aqueous solution The dosage is 2 to 2.5 times the volume of the hydrofluoric acid aqueous solution. 4. According to the preparation method of modified titanium dioxide nanofiber self-regenerating adsorbent according to claim 1, it is characterized in that the immersion time in the hydrofluoric acid aqueous solution in step (2) is 1 to 2 hours, and the washing 3 to 5 times. 5. The method for preparing the modified titanium dioxide nanofiber self-regenerating adsorbent according to claim 1, characterized in that the drying temperature in step (3) is 120-200° C., and the drying time is 1-3 hours.