CN101289244A - A method for natural photocatalytic degradation of chlorophenol pollutants - Google Patents

Abstract

The invention relates to a method for natural photocatalytic degradation of chlorophenol pollutants. First, a catalyst is added to an aqueous solution of chlorophenol pollutants with a mass concentration of ^10-2-300mg /L. The catalyst is composed of components A and B. A is a divalent or trivalent soluble iron salt, and B is an alkali metal Soluble salt; the ratio of the amount of substances A and B is 0.01-1; the ratio of the amount of catalyst to chlorophenols is 0.01-1. The reaction condition of the present invention is outdoor sunlight irradiation, low price, high degradation rate, no secondary pollution, suitable for the degradation of chlorophenol pollutants with wide distribution and low concentration and waste water produced by chlorophenol pollutants, industrialization The application prospect is great.

Description

A method for natural photocatalytic degradation of chlorophenol pollutants

technical field

The invention relates to a method for photodegradation and removal of chlorophenol pollutants, in particular to a method for catalytically degrading chlorophenol pollutants under sunlight.

Background technique

Since the 1930s, chlorophenols (CPs) have been widely used as wood preservatives, rust inhibitors, fungicides and herbicides, etc., and a large amount of chlorophenols wastewater is also produced in the pulp bleaching process, It is also used in the control of schistosomiasis in Asia, Africa and South America, so the production scale of CPs in many industrialized countries is very large. At the same time, 2-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol are highly toxic substances, and are included in the blacklist of priority pollutants by the US EPA. The extensive use of chlorophenol compounds has caused a large number of CPs pollutants to enter the environment, causing great harm to the natural environment. Therefore, removing such compounds from the environment is a major challenge for humans.

At present, there are many methods for treating chlorophenol-containing wastewater, and the commonly used methods are biodegradation, adsorption, extraction, and liquid membrane separation. However, the biological method takes a long time and is not suitable for the treatment of high-concentration chlorophenol wastewater. In addition, biodegradation of chlorophenol wastewater will also produce more toxic dioxin-like pollutants (LGOeberg, Chemosphere, 1992). Advanced oxidation technology is a technology developed in the 1980s to deal with refractory organic pollutants. Its main feature is to generate hydroxyl radicals through chemical reactions, so that organic pollutants can be effectively degraded into water, carbon dioxide and inorganic ions; mainly including Ozone oxidation, photocatalytic oxidation, wet oxidation, H2O2/UV, Fenton, O3/UV and other methods. Among advanced oxidation methods for treating chlorophenols, photocatalytic oxidation has attracted widespread attention due to its low cost and mild conditions. In the degradation of chlorophenols, the most representative one is Meunier's catalytic oxidation system (Science 1996), which uses hydrogen peroxide as oxidant and iron phthalocyanine as catalyst to deal with chlorophenols organic pollutants and the mineralization of carbon in trichlorophenols. The mineralization rate of chlorine is 14%, and the mineralization rate of chlorine is 70%. The world patent application (S.Muriel, WO0059836, 2000) invented a metal phthalocyanine catalyst, which uses hydrogen peroxide as an oxidant to treat trichlorophenol wastewater. In addition, in Collins' catalytic system (Science 2002), using tetraaminoiron macrocyclic compound as catalyst and hydrogen peroxide as oxidant, the mineralization rate of trichlorophenol is 35%, and the mineralization rate of chlorine is 83%. The existing problems are mainly that the used oxidants such as H ₂ O ₂ and O ₃ are expensive, so that the processing cost is relatively high, and in the process of catalytic oxidation, the synthesis cost of iron phthalocyanine catalyst, etc. is also relatively high. In addition, some Transition metal catalysts are unstable and easy to deactivate. The existence of these problems makes the industrialization prospect of chlorophenol wastewater treatment very small.

Contents of the invention

In order to overcome some deficiencies in the above-mentioned methods for degrading chlorophenols, the purpose of the present invention is to provide a photocatalyst with high catalytic activity, good treatment effect, mild reaction conditions, low treatment cost, great industrial application prospect, and in-situ treatment. A method for catalytically degrading chlorophenol pollutants.

To achieve the above object, the technical solution adopted in the present invention is:

A method for natural photocatalytic degradation of chlorophenol pollutants,

First, a catalyst is added to the aqueous solution of chlorophenol pollutants with a mass concentration of ^10-2-300mg /L;

The catalyst is composed of components A and B, A is a divalent or trivalent soluble iron salt, B is a soluble salt of an alkali metal; the ratio of the amounts of A and B is 0.01 to 1; the catalyst and chlorophenols The amount ratio is 0.01-1.

The trivalent soluble iron salt is ferric chloride, ferric nitrate and/or ferric sulfate; the soluble salt of alkali metal is nitrate, and these soluble salts use NO ₃ ^- and/or NO ₂ ^- as active anion components; catalyst The ratio of the amount of substance to chlorophenol is preferably 0.4-1.

The natural environment refers to a natural environment with an ambient temperature of -25°C to 45°C and a daily sunlight exposure time of 8-16 hours. This method has mild reaction conditions and is completely exposed to the natural environment. The experiment is completed on the roof of the laboratory building, using pure natural weather, and alternating day and night.

The present invention has the following advantages:

1. The catalyst has high activity and mild reaction conditions. In the present invention, a catalyst composed of trivalent soluble iron salt and non-transition metal salt solution is added to a small test tube with a ground mouth, and air is used as an oxidant to oxidize and degrade chlorophenol into carbon dioxide, water and some non-toxic small molecule carboxylic acid. The method can achieve 100% degradation rate in treating chlorophenol solution, and there is no secondary pollution in the degradation process.

2. The processing cost is low, and the industrialization prospect is great. Because the amount of oxidizing agent and catalyst used in the present invention is small, cheap and easy to obtain, and the treatment process is simple and convenient, the catalytic oxidation method of the present invention has the application prospect of industrially treating chlorophenol pollutants, and is suitable for wide distribution and low concentration Degradation of chlorophenol pollutants; this method has mild reaction conditions, low price and high degradation rate for treating chlorophenol wastewater. 3. Environmental friendly. The reaction system of the invention is simple, convenient and practical, has high catalyst reactivity and can completely remove pollutants. The catalyst will not cause secondary pollution to the environment within the concentration range used.

4. Wide application range. The present invention is applicable to the treatment of chlorophenol wastewater and some wastewater related to chlorophenol growth plants. The structural formula of common chlorophenols to be treated is exemplified as follows:

n=1-5.

In a word, the reaction condition of the present invention is outdoor sunlight irradiation, low price, high degradation rate, no secondary pollution, suitable for the degradation of chlorophenol pollutants with wide distribution and low concentration and waste water produced by chlorophenol pollutants , and has great prospects for industrial application.

Detailed ways

The present invention is given further description by examples below, of course, the present invention is not limited to following examples.

Example 1

First prepare a 200mg/L trichlorophenol solution, then dilute it 10 times with pure water, put 15ml of the solution into a 20ml glass test tube with a ground stopper, add a catalyst to the test tube, cover the lid, seal it with a parafilm, and put Enter the roof of the laboratory building, regularly sample and detect, and do a control reaction and an amplification reaction at the same time, and the removal rate of trichlorophenol after the reaction is shown in Table 1. The ambient temperature is -25°C to 10°C, and the daily sunlight exposure time is 8-10 hours.

Table 1 The results of photocatalytic degradation of trichlorophenol under natural conditions

mol% is the ratio of catalyst to trichlorophenol

Example 2

According to the operation procedure of the above-mentioned Example 1, FeCl ₃ /NaNO ₂ was used as a catalyst, and 20 mg/L o-chlorophenol pollutant was treated under the same conditions, and the results are shown in Table 2. The ambient temperature is -25°C to 10°C, and the daily sunlight exposure time is 8-10 hours.

Table 2 The results of photocatalytic degradation of o-chlorophenol under natural conditions

Example 3

According to the operation procedure of the above-mentioned Example 1, FeCl ₃ /NaNO ₂ was used as a catalyst to treat 20 mg/L p-chlorophenol pollutants under the same conditions, and the results are shown in Table 3. The ambient temperature is -25°C to 10°C, and the daily sunlight exposure time is 8-10 hours.

Table 3 The results of photocatalytic degradation of p-chlorophenol under natural conditions

Example 4

According to the operation steps of the above-mentioned Example 1, FeCl ₃ /NaNO ₂ was used as a catalyst to treat 20 mg/L 2,4-dichlorophenol pollutants under the same conditions, and the results are shown in Table 4. The ambient temperature is -25°C to 10°C, and the daily sunlight exposure time is 8-10 hours.

The results of photocatalytic degradation of 2,4-dichlorophenol under natural conditions in table 4

Example 5

According to the operation steps of the above-mentioned Example 1, FeCl ₃ /NaNO ₂ was used as a catalyst to treat 20 mg/L pentachlorophenol pollutants under the same conditions, and the results are shown in Table 5. The ambient temperature is -25°C to 10°C, and the daily sunlight exposure time is 8-10 hours.

The results of photocatalytic degradation of pentachlorophenol under natural conditions in table 5

Example 6

According to the operation steps of the above-mentioned Example 1, using FeCl ₃ /NaNO ₂ as a catalyst, at an ambient temperature of 20°C to 35°C, and under the conditions of 12-14 hours of sunlight irradiation time per day, 20mg/L trichlorophenol was treated Pollutants, the results are shown in Table 6.

The results of photocatalytic degradation of trichlorophenol under natural conditions in table 6

Claims (5)

1. A method for natural photocatalytic degradation of chlorophenol pollutants, characterized in that: A catalyst is added to an aqueous solution of chlorophenol pollutants with a mass concentration of 10 ^-2 -300mg/L, the catalyst is composed of components A and B, A is a divalent or trivalent soluble iron salt, and B is a soluble iron salt of an alkali metal Salt; the ratio of the amount of substances A and B is 0.01 to 1; the ratio of the amount of catalyst to chlorophenols is 0.01 to 1, and the reaction container is made of transparent material, and it is placed in an outdoor natural environment after being covered with a lid . 2. The method for natural photocatalytic degradation of chlorophenol pollutants according to claim 1, wherein the trivalent soluble iron salt is ferric chloride, ferric nitrate and/or ferric sulfate. 3. The method for natural photocatalytic degradation of chlorophenol pollutants according to claim 1, characterized in that: the soluble salts of alkali metals are nitrates, and these soluble salts use NO ₃ ^- and/or NO ₂ ^- as active anions components. 4. The method for natural photocatalytic degradation of chlorophenol pollutants according to claim 1, characterized in that: the ratio of the amount of the catalyst to the amount of chlorophenols is 0.4-1. 5. According to the method for natural photocatalytic degradation of chlorophenol pollutants according to claim 1, it is characterized in that: the natural environment refers to the ambient temperature between -25°C and 45°C, and the daily sunlight exposure time is 8-16 hours natural environment.