TWI422533B - Can be self - produced hydrogen peroxide wastewater advanced oxidation method - Google Patents

Description

Advanced oxidation treatment method for wastewater capable of generating hydrogen peroxide by itself

The invention relates to a wastewater treatment method, in particular to an advanced oxidation treatment method for wastewater which can generate hydrogen peroxide by itself.

Nowadays, the chemical industry is developing rapidly, and the demand for industrial water is increasing year by year. However, under the premise of preferential supply of water for people's livelihood, there may be a shortage of industrial water. If industrial wastewater can be properly treated, the standard for recycling can be achieved. It will greatly ease the demand and pressure of water use. In addition, it is now an important issue to effectively reduce the impact of these industrial pollutants on the environment by using wastewater treatment methods.

On the other hand, the dye is a kind of material widely used in various industrial processes. After use, it will produce dyeing and finishing wastewater. The dyes can be generally classified into: acid dyes, salt-based dyes, disperse dyes, reactive dyes, etc. The characteristics of the dye are insoluble in water, not easy to decompose and oxidize, and the absorption rate is low, but it is the only dye dyed by polyester fiber, and a few are used for dyeing of nylon and aolong, the dyeing method is adsorption, and the general water-soluble dye Differently, the disperse dyes can be classified into a nitro system and an azo system according to the chemical structure. Among them, azo dyes are toxic and may be converted into carcinogens.

Traditional methods for treating dyeing and finishing wastewater include activated carbon adsorption, chemical coagulation, and biological treatment. Among them, when the wastewater is treated by the techniques of activated carbon adsorption and chemical coagulation, the dye substance is converted from a liquid phase to a solid phase, and the produced sludge needs to be further processed, and the treatment procedure is relatively cumbersome but the treatment efficiency is not necessarily obtained. Higher. The biological treatment method is because the dye is an organic substance that is not easily decomposed by microorganisms, and the treatment effect is poor.

In addition, there is a treatment method of directly adding hydrogen peroxide to the dyeing and finishing wastewater. Although a good treatment effect can be obtained, hydrogen peroxide is quite expensive, and other operation steps and additives are still required.

The Fenton reaction procedure has been widely studied and applied to remove organic pollutants in wastewater, and its ‧ OH, which has strong oxidizing ability, is more effective than traditional physicochemical and biological treatments in destroying pollutants, and can cause organic pollution in water. Oxidation into non-toxic compounds, or oxidation into compounds that are more easily decomposed by microorganisms, and Fe ²⁺ is oxidized to Fe ³⁺ , which has the ability to coagulate, so the Fenton program has both the dual treatment functions of oxidation and coagulation. .

However, after Fe ^{+ 2+} is oxidized to Fe ³⁺ during the Fenton reaction, the rate of free radical generation will be slowed down, as shown by equations (1) and (2), and the rate constant (k) is 58 M ^{- 1} s ^{-1 is} reduced to 0.02 M ^-1 s ^-1 , which affects the efficiency of decomposition of organic matter. Therefore, in the previous study (Sagawe et al., 2001), it was clearly pointed out that equation (2) is the reaction rate limiting step in the Fenton program ( Rate-limiting step). Therefore, in the general Fenton reaction process, in order to achieve a good reaction effect, a large amount of iron salt needs to be added to facilitate the formation of ‧ OH, but this often causes a large amount of iron-containing sludge to be produced, thereby increasing the treatment cost of the sludge.

Fe ²⁺ +H ₂ O ₂ →‧OH+OH ^- +Fe ³⁺ k=58 M ^-1 s ^-1 (1)

Fe ³⁺ +H ₂ O ₂ →Fe ²⁺ +‧O ₂ H+H ⁺ k=0.02 M ^-1 s ^-1 (2)

In general, Fenton chemical oxidation requires a large amount of hydrogen peroxide to be added, resulting in an increase in cost, and the reaction system needs to be advantageously carried out under acidic conditions, but it causes environmental impact. Kang et al. used the Fenton method to treat textile mill wastewater and explore the advantages and disadvantages of chemical oxidation. For the removal of chromaticity, only a small amount of dose (H ₂ O ₂ = 10 mg / L, Fe ²⁺ = 10 mg / L) was required, and after 5 minutes of reaction, more than 90% of the chromaticity was removed. When the H ₂ O ₂ concentration is changed (H ₂ O ₂ = 100 mg/L), the chroma removal rate is only about 20% for the oxidant only (H ₂ O ₂ ) system. When Fe ²⁺ = 50 mg / L and H ₂ O ₂ = 100 mg / L, the chromaticity removal can reach more than 90% due to the Fenton reaction, and the COD removal rate increases with the H ₂ O ₂ concentration. With the increase, the maximum is 60%. In addition, when H ₂ O ₂ = 10 mg/L, the Fe ²⁺ concentration (5-50 mg/L) was changed, and 90% of the chromaticity was found to be removed when Fe ²⁺ = 10 mg/L, but for COD The removal is only about 20% (Kang et al., 2002).

Kang and other scholars also found that the Fenton treatment speed is very fast, only 10 min, but the COD removal effect is not good, the H ₂ O ₂ residual concentration is about 60%, but the chromaticity is 70% removal. effect. However, the chromaticity rises at the end of the reaction, and the reason is that the residual Fe ²⁺ will increase the chromaticity for a long time (Kang and Chang, 1997). Therefore, it is still impossible to simplify the steps of the Fenton process for treating wastewater and reduce its operating costs.

Accordingly, it is an object of the present invention to provide an advanced oxidation treatment process for wastewater which is self-generating hydrogen peroxide which can simplify the processing procedure.

Therefore, the present invention can automatically generate hydrogen peroxide wastewater advanced oxidation treatment method, comprising a preparation step, a reaction step, and a detection step.

The preparation step is to prepare an iron-aluminum composite metal, the reaction step is to mix the iron-aluminum composite metal with waste water, the iron-aluminum composite metal is used in an amount of 10 to 60 g/L, and react at room temperature for a set time. The detection step is to detect the chemical oxygen demand in the wastewater.

The invention has the effect that the iron-aluminum composite metal can be combined with the above operating conditions to generate a sufficient amount of hydrogen peroxide for the treatment of dyeing and finishing wastewater, and no need to cooperate with other operation steps, thereby greatly saving waste water treatment. cost.

The above and other technical contents, features and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments.

In recent years, it has been found that nanoscale zero-valent iron (nZVI) removes pollutants not only by the reduction mechanism but also by the mechanism of oxidation (Joo et al., 2004; Joo et al., 2005). . The principle of the oxidation program is mainly to use the electrons released when the zero-valent iron is converted into ferrous ions, and the oxygen in the water is changed into superoxide anion (O ₂ ^2- ) and superoxide ion (HO ₂ ^- ), and then in acidity. Hydrogen peroxide is formed under conditions, and ferrous ions in water react with hydrogen peroxide to form oxidant hydroxyl radicals (OH‧) (Keenan and Sedlak, 2008; Zhou et al., 2008; Lee and Choi, 2007). . Strong oxidizing hydroxyl radicals reoxidize and degrade pollutants. The species generation and reaction procedures are as follows:

Iron-aluminum composite metals have proven to be good electron suppliers that can degrade a variety of chlorinated organic pollutants through reductive dechlorination (Chen et al., 2008). The following reaction formula is a conceptual diagram of the degradation of carbon tetrachloride by iron-aluminum composite metal proposed in the literature (Chen et al., 2008). The reaction of carbon tetrachloride on the reduction and dechlorination of zero-valent iron surface causes oxidation of zero-valent iron. Ferrous ions increase the concentration of divalent iron in the water sample. The literature indicates that the iron-aluminum composite metal can stably provide a concentration of divalent ferrous ions in water of about 20 to 50 mg/L.

However, there is currently no application of iron-aluminum composite metals in the field of wastewater for treating oxidative pollutants. Therefore, experiments were first conducted on the formation of hydrogen peroxide from iron-aluminum composite metals.

It can be seen from Fig. 1 that the weight percentage of iron is 15wt%, and the amount of iron-aluminum composite metal used is 50 g/L. Hydrogen peroxide can be produced in about 1 hour, and the amount can be 25 mg in about 8 hours. /L. However, after 24 hours, the concentration gradually decreased, and it was estimated that the low concentration of hydrogen peroxide would naturally decompose into oxygen and water in the water sample, as shown in equation (3):

2H ₂ O ₂ →2H ₂ O+O ₂ (3)

Another reason is that hydrogen peroxide can oxidize metal ions in an aqueous solution, and when used as an oxidant, the product is water. As shown in equation (4), in a water sample under acidic conditions, hydrogen peroxide can oxidize ferrous ions to ferric ions, resulting in a decrease in hydrogen peroxide.

2Fe ²⁺ +H ₂ O ₂ +2H ⁺ →2Fe ³⁺ +2H ₂ O (4)

From the above experimental results, it is known that the iron-aluminum composite metal has the ability to form hydrogen peroxide in the presence of dissolved oxygen. In comparison with the study by scholars such as Joo, the study indicated that hydrogen peroxide can be produced at 0.187 mg/L when the additive amount of zero-valent iron is 0.1 g/L (Joo et al., 2004). It can be seen that the amount of hydrogen peroxide generated by the iron-aluminum composite metal is significantly better than the amount of hydrogen peroxide produced by using zero-valent iron in the literature alone.

After confirming that hydrogen peroxide can be produced by the iron-aluminum composite metal, the following experiments were carried out on the treatment of dyeing and finishing wastewater with iron-aluminum composite metal. Due to the difference in dyes, the type of dyeing and finishing wastewater produced is also different. In this embodiment, a reactive black dye, a reactive red dye, an acid black dye, an acid red dye, a salt-based black dye, and an anti-UV are selected. Dyeing and finishing wastewater formed by dyes and dye additives (such as dispersing agents, water repellents, softeners) and the like is subjected to the following experiments, and the characteristics of the dyeing and finishing wastewater formed by various substances are those having ordinary knowledge in the field. Can understand, no longer repeat them.

Referring to FIG. 2, a preferred embodiment of the advanced oxidation treatment method for wastewater capable of generating hydrogen peroxide by itself comprises a preparation step 21, a reaction step 22, and a detection step 23.

The preparation step 21 is to prepare an iron-aluminum composite metal, wherein the iron-aluminum composite metal has a weight percentage of iron of 5 to 25 wt% and a weight percentage of aluminum of 75 to 95 wt%.

The reaction step 22 is to mix the iron-aluminum composite metal with waste water, the iron-aluminum composite metal is used in an amount of 10 to 60 g/L, and react at room temperature for a set time, and the detecting step 23 is to detect the chemical in the wastewater. Chemical oxygen demand (COD).

Next, an experiment was conducted on COD degradation of a salt-based black dye and an anti-UV dye for an iron-aluminum composite metal using 5 to 25% by weight of iron. Iron-aluminum composite metals of 5%, 10%, 15%, and 25% by weight of iron were used, respectively, in an amount of 50 g/L, and reacted at room temperature for 24 hours. It can be seen from the experimental results in Table 1 and Figures 3 and 4 on the following page that the COD removal rate of the salt-based black dye is lower (52.5%) except that the weight ratio of iron is 5% by weight. The COD removal rate of other ratios is higher than 80%, and as the weight percentage of iron increases, the COD removal rate in wastewater also increases. It can be seen that regardless of the type of dyeing and finishing wastewater, the weight percentage of iron is 10 wt% or more, and the COD removal rate of 80% or more can be achieved.

Next, the weight percentage of iron was 15 wt%, but different amounts of the iron-aluminum composite metal were used to carry out COD degradation experiments on different kinds of dyeing and finishing wastewater for 24 hours.

In the present embodiment, the iron-aluminum composite metal used in the amounts of 0, 10, 20, and 50 g/L is used for the reactive black dye, the reactive red dye, the acid black dye, the acid red dye, and the salt base. Experiments were carried out on dyeing and finishing wastewaters such as black dyes and anti-UV dyes.

Refer to the experimental results in Table 2 on the next page. For the dyeing and finishing wastewater of reactive black dye, acid black dye, acid red dye and anti-UV dye, the effect of the amount of use is less significant, except for the removal rate of reactive black dye. Low (about 50%), other dyeing and finishing wastewater, regardless of the amount of use, the COD removal rate of more than 75%. For the reactive red dye and the salt-based black dye, the amount of use has a significant effect on the removal of the dye COD, and the removal rate is markedly increased as the amount of the composite metal used increases.

It can be seen that regardless of the type of dyeing and finishing wastewater, when the amount of iron-aluminum composite metal used is 50 g/L, the COD removal rate can reach 70% or more for most of the dyeing and finishing wastewater.

In addition, due to the different characteristics of the dye, the pH of the dyeing and finishing wastewater is also very different, using the same operating conditions (reaction at room temperature for 24 hours) and iron-aluminum composite metal dose (iron weight percentage 15wt%, usage 50 Under the condition of g/L), the initial pH value is from 3.0 to 9.6 to remove the dye in the water. As shown in Table 3, except for dye additives (such as dispersants and softeners), the COD removal rate can reach more than 50% (mostly more than 90%), and the final pH is weakly acidic. .

The iron-aluminum composite metal for removing COD from dyeing and finishing wastewater is shown in Table 4 and Figure 5. The use of 15% iron-aluminum composite metal can achieve both salt-based black dye and anti-UV dye in 8 hours. More than 80% removal rate, wherein the removal rate of anti-UV dye can reach more than 90% in 30 minutes.

In summary, the present invention can generate hydrogen peroxide waste water advanced oxidation treatment method, by mixing iron-aluminum composite metal with dyeing and finishing wastewater, hydrogen peroxide can be generated by itself, and by hydrogen peroxide reaction The COD in the dyeing and finishing wastewater is removed, so there is no need to add expensive hydrogen peroxide, and it is not necessary to cooperate with other treatment steps, that is, the dyeing and finishing wastewater can be effectively treated, the treatment process is greatly simplified, and the treatment cost is reduced, so that it can be achieved. The object of the invention.

The above is only the preferred embodiment of the present invention, and the scope of the invention is not limited thereto, that is, the simple equivalent changes and modifications made by the scope of the invention and the description of the invention are All remain within the scope of the invention patent.

twenty one. . . Preparation step

twenty two. . . Reaction step

twenty three. . . Detection step

Figure 1 is a graph illustrating the amount of hydrogen peroxide produced by an iron-aluminum composite metal, zero-valent iron, and zero-valent aluminum;

2 is a flow chart showing the operation steps of a preferred embodiment of the advanced oxidation treatment method of the wastewater capable of generating hydrogen peroxide by itself;

3 is a histogram showing the COD removal effect of different ratios of iron-aluminum composite metals on the dyeing and finishing wastewater of salt-based black;

4 is a histogram illustrating the COD removal effect of different ratios of iron-aluminum composite metals on dyeing and finishing wastewater resistant to UV dyes;

Figure 5 is a graph illustrating the effect of different treatment times on the COD removal rate of dyeing and finishing wastewater.

twenty one. . . Preparation step

twenty two. . . Reaction step

twenty three. . . Detection step

Claims (4)

An advanced oxidation treatment method for wastewater capable of generating hydrogen peroxide by itself comprises: a preparation step of preparing an iron-aluminum composite metal; a reaction step of mixing the iron-aluminum composite metal with dyeing and finishing wastewater, and the use of the iron-aluminum composite metal The amount is 10~60g/L, and reacts at room temperature for a set time; and a detection step detects the chemical oxygen demand in the dyeing and finishing wastewater. An advanced oxidation treatment method for wastewater which can generate hydrogen peroxide by itself according to the first aspect of the patent application, wherein the iron-aluminum composite metal has a weight percentage of iron of 5 to 25 wt% and an aluminum weight percentage of 75 to 95 wt%. . The advanced oxidation treatment method for wastewater which can generate hydrogen peroxide by itself according to the first aspect of the patent application, wherein the set time is at least 30 minutes. The advanced oxidation treatment method for wastewater which can generate hydrogen peroxide by itself according to the first aspect of the patent application scope, wherein the pH of the dyeing and finishing wastewater is between 2 and 10.