CN105084511A - Method for degrading organic waste water by activating persulfate through manganese-cobalt composite oxide - Google Patents

Abstract

The invention discloses a method for manganese-cobalt composite oxide to activate persulfate to degrade organic waste water. The method comprises the following steps: adding 0.5-5.0 mM of The persulfate and the manganese-cobalt composite oxide with a concentration of 0.1-2.0g/L are used to treat the water sample for 20min-3h, and then the solid-liquid separation is carried out, and the treatment process is completed. The invention adopts heterogeneous manganese-cobalt oxide as a catalyst, can efficiently and continuously activate persulfate to generate sulfate radical and hydroxyl radical, and achieve the purpose of degrading organic pollutants. At the same time, as an environmentally friendly material, manganese oxide can effectively reduce the leakage of cobalt ions, reduce secondary pollution and biological toxicity. The invention is suitable for treating various organic waste water, has high efficiency, good durability, can be used repeatedly and is convenient to operate, and provides broad prospects for treating refractory organic waste water.

Description

A method for manganese-cobalt composite oxide to activate persulfate to degrade organic wastewater

technical field

The invention belongs to the technical field of water treatment, and in particular relates to a method for manganese-cobalt composite oxide to activate persulfate to degrade organic wastewater.

Background technique

In recent years, the advanced oxidation technology based on sulfate radical has attracted more and more attention. Due to its high efficiency and high selectivity for the removal of refractory organic pollutants, it has developed into a new technology for the treatment of refractory organic wastewater. Compared with the hydroxyl radical (redox potential 1.8-2.7v) widely used in traditional advanced oxidation technology, the sulfate radical has a higher redox potential (2.5-3.1). Compared with hydroxyl radicals, sulfate radicals have a better degradation effect on pollutants in a wider pH range. The persulfate advanced oxidation technology has the advantages of good stability of the oxidizing agent itself, strong oxidizing ability of sulfate radicals generated, little influence of pH, high utilization rate of the oxidizing agent, and non-toxic and harmless.

Common persulfates include persulfate and persulfate. The key to the application of persulfate advanced oxidation technology is how to efficiently activate persulfate to generate sulfate radicals. Conventional methods for activating persulfate radicals include physical methods such as heat, ultraviolet light, and microwaves, and chemical activation methods for transition metal ions such as Co ²⁺ , Mn ²⁺ , Fe ²⁺ , Ag ⁺ , and Cu ²⁺ . Since the reaction of transition metal ion-activated persulfate can proceed rapidly at room temperature without the need for additional energy, transition metal ion-activated persulfate has shown greater potential for environmental remediation than thermal and UV-activated persulfate. superiority. Previous studies have proved that the transition metal ion Co ²⁺ can efficiently activate persulfate to produce active oxide species mainly based on sulfate radicals, and the reaction conditions are simple and mild, and the free radical generation rate is fast. But at the same time, Co ²⁺ also has limitations, such as it is not easy to recycle and reuse, and it may cause potential secondary pollution and biological toxicity. In order to solve the above problems, the present invention proposes a new method of using manganese-cobalt composite oxide to activate persulfate oxidation to remove refractory organic pollutants in water.

At present, there is no invention related to the application of manganese-cobalt composite oxide to activate persulfate to degrade organic wastewater.

Contents of the invention

Purpose of the invention: In order to solve the problems in the prior art, the present invention provides a manganese-cobalt composite oxide activated persulfate that can not only efficiently and continuously activate persulfate, but also reduce the secondary pollution and biological toxicity caused by the catalyst. Method for salt degradation of organic wastewater.

Technical solution: In order to achieve the above-mentioned technical purpose, the method for manganese-cobalt composite oxide to activate persulfate to degrade organic wastewater of the present invention comprises the following steps: under normal temperature conditions, add a concentration of 0.5 to the wastewater containing organic pollutants ～5.0mM persulfate and manganese-cobalt composite oxide with a concentration of 0.1～2.0g/L, treat the water sample for 20min～3h, and then perform solid-liquid separation.

Specifically, the cobalt oxide in the manganese-cobalt composite oxide is any one or a mixture of CoO, Co ₂ O ₃ and Co ₃ O ₄ ; the manganese oxide is MnO, MnO ₂ (including α -, β-, γ-MnO ₂ ), Mn ₃ O ₄ any one or a mixture of several. The persulfate is any one of persulfate and peroxodisulfate.

Preferably, the persulfate is any one of KHS ₂ O ₅ and NaHS ₂ O ₅ ; the peroxodisulfate is any one of K ₂ S ₂ O ₈ and Na ₂ S ₂ O ₈ A sort of.

The manganese-cobalt composite oxide is synthesized by a hydrothermal method or an impregnation method. Wherein, the cobalt oxides are commercial products CoO, Co ₂ O ₃ and Co ₃ O ₄ , and the manganese-cobalt composite oxides are added during the synthesis of manganese oxides by any method in the hydrothermal method or impregnation method. Cobalt oxide is prepared. Wherein, the synthesis of manganese oxide can be carried out according to the conventional synthesis method of manganese oxide.

Specifically, in one embodiment, the steps of preparing manganese oxide by hydrothermal method are:

(1) Take a certain amount of KMnO ₄ and MnSO ₄ (molar ratio 8: 3) were dissolved in water, after stirring for one hour, the mixed solution was transferred to an autoclave, and heat-treated for 12 hours at 160°C;

(II) Dissolve 2 mmol of KMnO in deionized water, add concentrated sulfuric acid dropwise while stirring, put into a 2cm×8cm copper plate, and heat in a water bath at 60°C for 8 hours;

(III) Dissolve 4 mmol of KMnO in deionized water and stir, add a certain amount of glucose, ethylenediamine and 1.4 mL of concentrated HCl solution to the KMnO solution, transfer the mixed solution to an autoclave, and heat-treat at 120°C 12 hours.

Take samples I, II, and III respectively, filter them, wash them three times with deionized water, then wash them twice with absolute ethanol, dry them at 60°C for 24 hours, and calcinate the samples in a muffle furnace at a temperature of 1°C/min. The rate is raised from room temperature to 300°C, 300°C, and 350°C respectively, and the temperature is maintained for 4 hours to continue calcination to obtain α, β, and γ crystal forms of manganese dioxide respectively. The corresponding manganese-cobalt composite oxide can be prepared by adding the required amount and required type of cobalt oxide during the preparation process of the above-mentioned different crystal forms of manganese dioxide.

Impregnation method: add sodium thiosulfate or ethanol, methanol to the KMnO ₄ solution to reduce KMnO ₄ to MnO ₂ , the whole reaction process generally takes 2 to 3 hours, take out the sample, and calcine it in a muffle furnace, the control is different temperature, different crystal forms of manganese dioxide can be calcined. At the beginning of the preparation, the corresponding manganese-cobalt composite oxide can be prepared by adding the required amount and type of cobalt oxide into the KMnO ₄ solution.

Other manganese oxides are prepared by the reduction method. Manganese dioxide is calcined in a muffle furnace, and hydrogen gas is introduced. By controlling the amount of hydrogen gas, manganese oxides of different valence states can be obtained.

The refractory organic wastewater is any one of printing and dyeing wastewater, coal chemical wastewater, petrochemical wastewater, pharmaceutical wastewater, paint wastewater, beer wastewater and alcohol wastewater.

Preferably, the applicable pH range of the entire reaction system is 2-12.

More preferably, the applicable pH range of the entire reaction system is 6-8.

In the present invention, cobalt oxide (one or more of CoO, Co ₂ O ₃ and Co ₃ O ₄ compounded in different proportions), manganese oxide (one or more of MnO, MnO ₂ and Mn ₃ O ₄ Compounds in different proportions) are insoluble in water, so the process of activating persulfate to degrade organic wastewater belongs to heterogeneous catalytic oxidation, which makes it easier to separate manganese-cobalt composite oxides from water after the catalytic process ends. Compared with transition metal ion catalysts, manganese-cobalt composite oxides have very low toxicity to organisms, even if a small amount of manganese and cobalt leaks into the water body during the treatment process, it will not have a great impact on water quality. In addition, the prices of cobalt oxide and manganese oxide are both lower.

Beneficial effects: compared with the prior art, the present invention has the following beneficial effects:

(1) Manganese-cobalt composite oxide can effectively activate persulfate in the present invention to produce sulfate radicals and hydroxyl radicals, and the utilization rate of free radicals is high, the reaction rate is fast, and the removal effect of pollutants is good;

(2) compared with traditional cobalt oxide activated persulfate, the inventive method not only improves the removal rate of organic pollutants and the catalytic efficiency of catalyst due to the addition of manganese oxide, but also greatly reduces secondary pollution and Biological toxicity caused by catalyst leakage;

(3) The present invention is applicable to the treatment of various organic wastewaters, and thus has wide application prospects; the manganese-cobalt composite oxide has high catalytic efficiency, good durability, convenient use, and is an environment-friendly catalyst.

Description of drawings

Fig. 1 is the change figure of embodiment 1 to the removal rate of refractory organic matter;

Fig. 2 is the change graph of the removal rate of the refractory organic matter in Example 2.

Detailed ways

The invention proposes a method for manganese-cobalt composite oxide to activate persulfate to degrade organic waste water, specifically: add persulfate with a concentration of 0.5-5.0 mM to waste water containing organic pollutants under normal temperature conditions and manganese-cobalt composite oxide with a concentration of 0.1-2.0g/L, treat the water sample for 20min-3h, and then perform solid-liquid separation, wherein the cobalt oxides in the manganese-cobalt composite oxide are CoO, Co ₂ O ₃ and Co Any one or a mixture of several of ₃ O ₄ ; manganese oxide is any one or a mixture of several of MnO, MnO ₂ (α-, β-, γ-MnO ₂ ), Mn ₃ O ₄ , Wherein, the cobalt oxide is directly purchased from commercial products CoO, Co ₂ O ₃ and Co ₃ O ₄ , and the manganese-cobalt composite oxide is synthesized in the process of manganese oxide synthesis by any method in the hydrothermal method or impregnation method. Prepared by adding cobalt oxide.

A typical method for preparing manganese oxides is:

(1) Take a certain amount of KMnO ₄ and MnSO ₄ (molar ratio 8: 3) were dissolved in water, after stirring for one hour, the mixed solution was transferred to an autoclave, and heat treated at 160°C for 12 hours;

(II) Dissolve ₂ mmol of KMnO in deionized water, add concentrated sulfuric acid dropwise while stirring, put into a 2cm×8cm copper plate, and heat in a water bath at 60°C for 8 hours;

(III) Dissolve ₄ mmol of KMnO in deionized water and stir, add a certain amount of glucose, ethylenediamine and _1.4 mL of concentrated HCl solution to the KMnO solution, transfer the mixed solution to an autoclave, and heat heat treatment for 12 hours.

Take samples I, II, and III respectively, filter them, wash them three times with deionized water, then wash them twice with absolute ethanol, dry them at 60°C for 24 hours, and calcinate the samples in a muffle furnace at a temperature of 1°C/min. The rate is raised from room temperature to 300°C, 300°C, and 350°C respectively, and the temperature is maintained for 4 hours to continue calcination to obtain α, β, and γ crystal forms of manganese dioxide respectively. The corresponding manganese-cobalt composite oxide can be prepared by adding the required amount and required type of cobalt oxide during the preparation process of the above-mentioned different crystal forms of manganese dioxide.

Impregnation method: add sodium thiosulfate or ethanol, methanol to the KMnO ₄ solution to reduce KMnO ₄ to MnO ₂ , the whole reaction process generally takes 2 to 3 hours, take out the sample, and calcine it in a muffle furnace, the control is different temperature, different crystal forms of manganese dioxide can be calcined. At the beginning of the preparation, the corresponding manganese-cobalt composite oxide can be prepared by adding the required amount and type of cobalt oxide into the KMnO ₄ solution.

Other manganese oxides are prepared by the reduction method. Manganese dioxide is calcined in a muffle furnace, and hydrogen gas is introduced. By controlling the amount of hydrogen gas, manganese oxides of different valence states can be obtained.

Persulfate is any one of persulfate and peroxodisulfate, such as peroxosulfate is any one of KHS ₂ O ₅ and NaHS ₂ O ₅ ; peroxodisulfate is K ₂ S ₂ O ₈ and any one of Na ₂ S ₂ O ₈ .

The present invention will be described in detail below through specific examples.

Example 1 Manganese-cobalt composite oxide activates persulfate to degrade printing and dyeing wastewater.

Take 500mL of the untreated water sample containing printing and dyeing wastewater, and the pH value is 7.0. In this water sample, add manganese-cobalt composite oxide (MnO ₂ -CoO) 0.1g/L (wherein, MnO ₂ -CoO is prepared according to the step of hydrothermal method (I), in the process of preparing MnO ₂ add CoO Particles), persulfate 0.5mM, the water sample was treated for 75min, compared with the single persulfate oxidation method, the removal rate increased from 1% to 75%.

Fig. 1 is the removal effect diagram of the present embodiment to the refractory organic matter in the printing and dyeing wastewater, and the refractory organic matter is taken as orange G (OG), and - in the figure - represents the removal rate curve of the organic waste water degraded by persulfate oxidation alone, - △- represents the removal rate curve of MnO ₂ -CoO activated persulfate oxidation degradation of organic wastewater.

Example 2

Take 500mL of the untreated water sample containing printing and dyeing wastewater, and the pH value is 7.0. Add 2.0g/L of manganese-cobalt composite oxide (MnO ₂ -Co ₃ O ₄ ) into the water sample (wherein, the preparation of MnO ₂ -Co ₃ O ₄ is carried out according to the steps in the hydrothermal method (II), and the During the preparation of MnO ₂ , 5 mM of Co 3 O 4 persulfate (Co ₃ O ₄ particles) was added, and the water sample was treated for 75 minutes. Compared with the oxidation of persulfate alone, the removal rate increased from 1% to 95%.

Fig. 2 is the removal effect diagram of the present embodiment to the refractory organic matter in the printing and dyeing wastewater, and the refractory organic matter is taken as orange G (OG), and - in the figure - represents the removal rate curve of the organic waste water degraded by persulfate oxidation alone, - △- represents the removal rate curve of MnO ₂ -Co ₃ O ₄ activated persulfate oxidation degradation of organic wastewater.

Example 3

Take 500mL of the untreated water sample containing coal chemical wastewater, in which the refractory organic matter is phenol, and the pH value is 5.0. In this water sample, add manganese-cobalt composite oxide (MnO-CoO) 0.1g/L (MnO-CoO is prepared according to the step of hydrothermal method (I), adds CoO particle in the process of preparing _MnO ), over Sulfate 0.5mM, treatment of water samples for 20min, compared with single persulfate oxidation, the removal rate increased from 1% to 45%.

Example 4

Take 500 mL of the untreated water sample containing petrochemical wastewater, in which the refractory organic matter is phenolic compounds, and the pH value is 9.0. Add manganese-cobalt composite oxide (Mn ₃ O ₄ -Co ₃ O ₄ -CoO) 2.0g/L to the water sample (Mn ₃ O ₄ -Co ₃ O ₄ -CoO is synthesized according to hydrothermal method II combined with reduction method Mn ₃ O ₄ , add Co ₃ O ₄ and CoO particles in the process of preparing Mn ₃ O ₄ ), persulfate 5mM, treat water samples for 3h, compared with single persulfate oxidation, the removal rate is increased by 1% to 100%.

Example 5

Take 500mL of the water sample to be treated containing pharmaceutical wastewater, in which the refractory organic matter is the antibiotic ciprofloxacin, and the pH value is 5.0. Add manganese-cobalt composite oxide (MnO ₂ -CoO-Co ₂ O ₃ ) 1.2g/L (MnO ₂ -CoO-Co ₂ O ₃ ) to the water sample to synthesize MnO ₂ according to the hydrothermal method II combined with the reduction method. Co ₃ O ₄ and CoO particles are added in the process of preparing MnO ₂ ), persulfate 3mM, and the water sample is treated for 60min. Compared with the single persulfate oxidation, the removal rate is increased from 1% to 70%.

Example 6

Take 500mL of the untreated water sample containing paint wastewater, in which the refractory organic matter is benzene and toluene, and the pH value is 9.0. Add 0.5g/L of manganese-cobalt composite oxide (MnO ₂ -Co ₃ O ₄ ) to the water sample (MnO ₂ -Co ₃ O ₄ is synthesized according to the impregnation method, and Co ₃ O ₄ is added during the preparation of MnO ₂ Particles), persulfate 1.5mM, water samples were treated for 30min, compared with single persulfate oxidation, the removal rate increased from 1% to 35%.

Example 7

Take 500mL of the untreated water sample containing beer wastewater, and the pH value is 10.0. Add 1.6g/L of manganese-cobalt composite oxide (MnO ₂ -CoO) to the water sample (MnO ₂ -CoO is synthesized according to the impregnation method, and CoO particles are added during the preparation of MnO ₂ ), persulfate 4.5mM, Treating water samples for 30 minutes, compared with single persulfate oxidation, the removal rate increased from 1% to 60%.

Example 8

Take 500mL of the untreated water sample containing alcohol wastewater, and the pH value is 11.0. Add 1.8g/L of manganese-cobalt composite oxide (MnO ₂ -Co ₃ O ₄ ) to the water sample (MnO ₂ -Co ₃ O ₄ is synthesized according to the impregnation method, and Co ₃ O ₄ is added during the preparation of MnO ₂ Particles), persulfate 4.0mM, the water sample was treated for 60min, compared with the single persulfate oxidation, the removal rate increased from 1% to 90%.

Claims (8)

1. A kind of method that manganese-cobalt composite oxide activates persulfate to degrade organic waste water, it is characterized in that: under normal temperature condition, in the waste water that contains organic pollutant, dosing concentration is the persulfate of 0.5～5.0mM and Manganese-cobalt composite oxide with a concentration of 0.1-2.0g/L, the water sample is treated for 20min-3h, and then solid-liquid separation is performed. 2. the method for manganese-cobalt composite oxide activation persulfate degradation organic waste water according to claim 1, is characterized in that, in described manganese-cobalt composite oxide, cobalt oxide is CoO, Co ₂ O ₃ and Co ₃ O ₄ any one or a mixture of several; the manganese oxide is any one or a mixture of MnO, MnO ₂ , Mn ₃ O ₄ . 3. The method for manganese-cobalt composite oxide activating persulfate to degrade organic wastewater according to claim 1, wherein the persulfate is any one of persulfate and peroxodisulfate. 4. the method for manganese-cobalt composite oxide activation persulfate degradation organic waste water according to claim 3, is characterized in that, described persulfate is KHS ₂ O ₅ and NaHS ₂ O ₅ any one ; The peroxodisulfate is any one of K ₂ S ₂ O ₈ and Na ₂ S ₂ O ₈ . 5. the method for manganese-cobalt composite oxide activation persulfate degradation organic waste water according to claim 1, is characterized in that, described manganese-cobalt composite oxide is synthesized by any method in hydrothermal method or dipping method Manganese oxides are prepared by adding cobalt oxides. 6. the method for manganese-cobalt composite oxide activated persulfate degradation organic waste water according to claim 1, is characterized in that, described refractory organic waste water is printing and dyeing waste water, coal chemical industry waste water, petrochemical waste water, pharmaceutical waste water, paint Any one of waste water, beer waste water and alcohol waste water. 7. The method for manganese-cobalt composite oxide to activate persulfate to degrade organic wastewater according to claim 1, characterized in that the applicable pH range of the entire reaction system is 2-12. 8. The method for manganese-cobalt composite oxide to activate persulfate to degrade organic wastewater according to claim 1, characterized in that the applicable pH range of the entire reaction system is 6-8.