CN103331176A - Photocatalyst used for processing arsenic-containing waste water and preparation method thereof - Google Patents

Abstract

The invention discloses a photocatalyst for efficiently catalyzing and removing arsenic pollutants in waste water and a preparation method thereof. The catalyst can efficiently catalyze and oxidize trivalent arsenic into pentavalent arsenic by utilizing sunlight, and absorb and remove the pentavalent arsenic. The preparation method mainly involves solvothermal process, the raw materials are easy to obtain, and the operation is relatively simple. The synthesized catalyst has high catalytic efficiency, large specific surface area, large particle size, and easy separation. After repeated use, the catalytic efficiency remains the same. higher. Experiments have proved that under sunlight irradiation, the oxidation efficiency of the catalyst to trivalent arsenic can reach more than 95%, and the removal efficiency of total arsenic (trivalent and pentavalent arsenic) can reach more than 90%.

Description

A photocatalyst for treating arsenic-containing wastewater and its preparation method

technical field

The invention belongs to the field of water treatment and purification, in particular to a photocatalyst for efficiently catalytically removing arsenic pollutants in wastewater and a preparation method thereof.

Background technique

Arsenic compounds are protoplasmic poisons with metal-like properties and have a wide range of biological effects. They have been identified as the first class of carcinogens by the US Centers for Disease Control and the International Agency for Cancer Prevention and Research. In recent years, with the rapid development of industries such as mining, ceramics, leather, and pesticides, the arsenic pollution in the water environment has become increasingly serious. China is also one of the countries most seriously affected by arsenic poisoning. Therefore, my country has strictly regulated the concentration of arsenic in wastewater discharge and drinking water standards. Arsenic removal and drinking water arsenic removal technologies bring new challenges.

At present, there are many methods for arsenic pollution treatment, which can be summarized as follows:

Precipitation method: Mainly use external agents or energy to form precipitation with arsenic pollutants in water and separate them. The precipitation method has a simple process and low investment, but a large amount of waste residue containing arsenic cannot be used, and it is easy to cause secondary pollution.

Adsorption method: use high specific surface area, insoluble solid material as adsorbent, and fix arsenic pollutants on its surface through physical or chemical adsorption, so as to achieve the purpose of removing arsenic. This method is simple and easy to implement, but the strong adsorption between the arsenic compound and the adsorbent often makes the recovery and reuse of the adsorbent difficult. In addition, phosphates, sulfates, silicates, fluorides and other substances present in wastewater are also likely to compete with arsenic for adsorption sites, resulting in a decrease in adsorption efficiency.

Oxidation method: Since the toxicity of trivalent arsenic is 60 times that of pentavalent arsenic, and it is more difficult to be adsorbed and removed than pentavalent arsenic, in the process of arsenic-containing wastewater treatment, trivalent arsenic is often oxidized to pentavalent arsenic, and then adsorbed remove. In recent years, photocatalytic oxidation has become a hot spot in the environmental field. Using TiO ₂ photocatalyst, most of the trivalent arsenic can be oxidized to pentavalent arsenic under the irradiation of ultraviolet light. However, TiO ₂ photocatalyst can only be excited by ultraviolet light, which accounts for 3-4% of solar energy, wasting a lot of visible light energy, and TiO ₂ powder particles are usually small in size, which is difficult to recycle. Therefore, the development of stable, efficient, and easily recyclable visible light photocatalysts has become a new approach in photocatalytic oxidation.

Ion exchange method: Ion exchange method is also an effective method for arsenic removal, but the treatment process of this method is relatively complicated, the cost is high, and it can only treat wastewater with low concentration, simple composition and high recovery value, and it is difficult to commercialize.

Contents of the invention

The purpose of the present invention is to overcome the above-mentioned deficiencies of the prior art, and provide a photocatalyst for efficiently catalytically removing arsenic pollutants in wastewater and a preparation method thereof. The raw material of the invention is easy to obtain, the operation is relatively simple, and the synthesized catalyst has high catalytic efficiency, large specific surface area, large particle size, easy separation, and high catalytic efficiency after repeated use. Experiments have proved that under sunlight irradiation, the oxidation efficiency of the catalyst to trivalent arsenic can reach more than 95%, and the removal efficiency of total arsenic (trivalent and pentavalent arsenic) can reach more than 90%.

To achieve the above object, the present invention adopts the following technical solutions:

A photocatalyst BiOI for treating arsenic-containing wastewater has a PbFCl-type crystal structure, that is, [Bi ₂ O ₂ ] ²⁺ and ^I- are interlaced and superimposed to form a layered structure. child separation.

The BiOI photocatalyst is synthesized by glycerol solvothermal method. The larger viscosity of glycerol makes the synthesized BiOI sheet-like structure have a thinner thickness, and the carrier separation efficiency is higher. The synthesized BiOI The sheet-like structure can self-assemble to form graded spherical aggregates under experimental conditions, and the particle size is about 10-50 microns observed by scanning electron microscope, and has a large specific surface area. The preparation method comprises the following steps:

(1) Precursor treatment: Dissolve bismuth nitrate pentahydrate and potassium iodide in the same amount in glycerol, mix and stir to prepare the precursor;

(2) Put the precursor in a polytetrafluoroethylene reactor, keep it warm at 130-180°C for 6-12 hours, then cool down to room temperature naturally, wash the obtained precipitate with distilled water several times, and dry it in vacuum or air at 60-80°C After 12-24 hours, the BiOI photocatalyst is obtained.

BiOI photocatalyst uses sunlight to efficiently catalyze the oxidation of trivalent arsenic to pentavalent arsenic, and absorb and remove the pentavalent arsenic. The specific experimental content and detection method are as follows: add a certain amount of catalyst to simulated polluted wastewater of trivalent arsenic with different contents, under magnetic stirring, use sunlight or simulated sunlight light source to irradiate for a certain period of time, after centrifugation, take the supernatant, The concentrations of trivalent arsenic and total arsenic were measured by atomic fluorescence spectrophotometer.

Significant advantage of the present invention is:

(1) The catalyst is prepared by the solvothermal method, the raw materials are easily obtained, the steps are few, the operation is simple, and it is suitable for industrial production.

(2) The synthesized catalyst has high photocatalytic oxidation activity of trivalent arsenic under sunlight or simulated solar light source irradiation, and has superior adsorption performance for the generated pentavalent arsenic, and the removal efficiency of total arsenic high.

(3) The synthesized catalyst has good stability, and still has high activity after repeated use, and the catalyst particle size is large, which is easy to recycle.

Description of drawings

Fig. 1 is the X-ray diffractogram of the catalyst synthesized in embodiment 1.

FIG. 2 is a field emission scanning electron micrograph of the catalyst synthesized in Example 1.

Fig. 3 is the photo of the catalyst synthesized in embodiment 1 through 15 minutes of natural sedimentation.

Detailed ways

The following examples are given to further illustrate the present invention.

Example 1

Weigh 2.425 grams of bismuth nitrate pentahydrate and 0.83 grams of potassium iodide, and dissolve them in 40 milliliters of glycerol respectively, mix the two, and stir for 30 minutes to obtain a precursor, then place the precursor in 100 milliliters of polytetrafluoroethylene to react In the kettle, the reactor was put into a steel jacket, and placed in an oven, kept at 160°C for 12 hours, then naturally cooled to room temperature, and the resulting precipitate was washed 6 times with deionized water, and then placed in a 60°C oven Air dry for 12 hours.

Example 2

The catalyst synthesized according to the method of Example 1 was scanned by an X-ray diffractometer, as shown in FIG. 1 , and was determined to be a BiOI crystal.

Example 3

According to the catalyst synthesized by the method of Example 1, through the field emission scanning electron microscope observation, the synthesized catalyst particles are self-assembled by nano sheet structure, and its sheet thickness is about 10 nanometers, and the particle size is about 10-50 microns, see figure 2.

Example 4

Weigh 40 milligrams of the catalyst synthesized in Example 1, add it to 80 milliliters of 5 mg/liter sodium arsenite solution, and use a xenon lamp to simulate a solar light source under magnetic stirring at 1000 rpm. After irradiating for 60 minutes, centrifuge, filter, The supernatant was taken and tested by an atomic fluorescence spectrophotometer (PF6, Beijing Puxi General Instrument Co., Ltd.), the removal rate of trivalent arsenic reached 97%, and the removal rate of total arsenic reached 92%.

Example 5

Weigh 20 milligrams of the catalyst synthesized in Example 1, add it to 80 milliliters of 1 mg/liter sodium arsenite solution, and irradiate under sunlight for 3 hours under 1000 rpm magnetic stirring, centrifuge, filter, and take the supernatant The liquid was detected by atomic fluorescence spectrophotometer, the concentration of trivalent arsenic was 0.9 micrograms/liter, the removal rate was 99.9%, the concentration of total arsenic was 6.9 micrograms/liter, the removal rate was 99.3%, and the arsenic content had reached the national drinking water standard .

Example 6

According to the process of Example 4, after the used catalyst is recovered and dried, continue to weigh 40 mg and add it to 80 ml of 5 mg/L sodium arsenite solution for the second test. After the reaction, the catalyst Recycled and dried, and carried out the third test. After repeating the cycle for 5 times, the removal rates of trivalent arsenic and total arsenic (trivalent arsenic and pentavalent arsenic) are shown in Table 1.

The removal rate of trivalent arsenic and total arsenic (trivalent arsenic and pentavalent arsenic) of the catalyst synthesized in table 1 embodiment 1

Example 7

Weigh 40 mg of the catalyst, add it to 80 ml of 5 mg/L sodium arsenite solution, let it stand, and observe that it has basically settled completely within 15 minutes, as shown in Figure 3.

The above descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention.

Claims (4)

1. photochemical catalyst of handling arsenic-containing waste water, it is characterized in that: described photochemical catalyst is BiOI.

2. method for preparing the photochemical catalyst of processing arsenic-containing waste water as claimed in claim 1 is characterized in that: described BiOI photochemical catalyst utilizes the glycerine solvent thermal method synthetic.

3. the preparation method of the photochemical catalyst of processing arsenic-containing waste water according to claim 2 is characterized in that: may further comprise the steps:

(1) processing of predecessor: five water bismuth nitrates and the KI of the amount of same substance are dissolved in respectively in the glycerine, mix, stir and make predecessor;

(2) predecessor is placed the polytetrafluoroethylene (PTFE) reactor, in 130-180 ℃ of insulation 6-12 hour, be cooled to room temperature subsequently naturally, gained precipitation is after distilled water washing for several times, and 60-80 ℃ of vacuum or air were dried 12-24 hour, namely got the BiOI photochemical catalyst.

4. the application of the photochemical catalyst of a processing arsenic-containing waste water as claimed in claim 1 is characterized in that: the BiOI photochemical catalyst utilizes sunshine, and the efficiently catalyzing and oxidizing trivalent arsenic is pentavalent arsenic, and pentavalent arsenic absorption is removed.

Images