CN110182934A - Method for activating molecular oxygen by using nano zero-valent aluminum under alkaline condition and application - Google Patents

Abstract

The invention discloses a method for activating molecular oxygen by utilizing nano zero-valent aluminum under an alkaline condition and application thereof. The method takes sodium tripolyphosphate as a hydrolysis reagent and nano zero-valent aluminum as a catalyst, reduces dissolved oxygen in an alkaline aqueous solution into oxygen-containing free radicals, and is used for degrading pollutants represented by indigo and paracetamol. The invention utilizes sodium tripolyphosphate to react with Al³⁺The complex effect and the unique proton confinement effect of the nano-sized aluminum complex respectively dissolve the surface passivation layer of the nano-sized zero-valent aluminum and control the electron transfer of the interface, thereby improving the effective utilization of molecular oxygen. The method has simple process, mild condition and easy controlThe response range to the pH value of the wastewater is widened, the exposure risk of the traditional technology for activating the nano zero-valent aluminum by the organic complexing agent to the environment is reduced, and a new idea is provided for the aerobic degradation of organic pollutants by the nano zero-valent aluminum.

Description

A method and application of using nanometer zero-valent aluminum to activate molecular oxygen under alkaline conditions

technical field

The invention belongs to the technical field of wastewater treatment, and in particular relates to a method and application of using nanometer zero-valent aluminum to activate molecular oxygen under alkaline conditions.

Background technique

The treatment of environmental pollutants with nanometer zero-valent metals is a pollution control technology worthy of in-depth research and application value. The feature of this technology is that under anaerobic conditions, nano-zero-valent metals reduce heavy metals or reduce halogenated organic compounds; under aerobic conditions, nano-zero-valent metals activate molecular oxygen to degrade organic pollutants; under specific pH conditions, nano-zero Valence metals can adsorb or co-precipitate pollutants. However, the advanced oxidation technology excited by nano-zero-valent metals under aerobic conditions faces the following problems: the passivation layer of nano-zero-valent metals hinders the contact between the active surface and pollutants; the four-electron reduction reaction of ineffective molecular oxygen dominates, inhibiting the Generation of oxygen reactive species. Nano-scale zero-valent metals with strong reducing activity include zero-valent aluminum (E ^θ (Al ³⁺ /A1) = -1.662V), zero-valent manganese (E ^θ (Mn ²⁺ /Mn) = -1.185V), zero-valent Zinc (E ^θ (Zn ²⁺ /Zn) = -0.762V), zero-valent iron (E ^θ (Fe ²⁺ /Fe) = -0.447V), zero-valent cobalt (E ^θ (Co ²⁺ /Co) = -0.28V), etc. Among them, nanoscale zero-valent aluminum (nZVAl) is an excellent catalyst for environmental pollution control due to its strong thermodynamic reducibility and low risk of environmental exposure.

In recent years, in order to overcome the problems faced by nZVAl in advanced oxidation applications, commonly used methods include surface corrosion pretreatment of nZVAl with acidic solution, and passivation layer dissolution of nZVAl with organic complexing agents (EDTA-Na, sodium oxalate, etc.). However, the added organic complexing agents pose environmental exposure risks. Aiming at the defects of the above prior art, the inventor of the present invention discovered the following technical solutions for the first time after painstaking research.

Contents of the invention

The purpose of the present invention is to solve the surface passivation of nZVAl and inhibit the four-electron reduction reaction of molecular oxygen, and provide a method and application of using nanometer zero-valent aluminum to activate molecular oxygen under alkaline conditions. The present invention uses sodium tripolyphosphate to in situ dissolve the nZVAl surface passivation layer in the reaction solution, and simultaneously controls interface electron transfer, so that the nZVAl efficiently reduces molecular oxygen into oxygen-containing free radicals, and strengthens the degradation of pollutants. The process condition is easy to control and has good molecular oxygen catalytic activity.

The object of the invention is achieved through the following technical solutions:

The invention discloses a method for activating molecular oxygen by using nanometer zero-valent aluminum under alkaline conditions. The hydrolysis reagent is sodium tripolyphosphate, and the nanometer zero-valent aluminum is used as a catalyst to degrade pollutants by catalyzing dissolved oxygen in aqueous solution. Due to the complexing effect of TPP on Al ³⁺ and the "proton confinement effect", the electron transfer pathway at the nZVAl interface is regulated to promote the effective utilization of molecular oxygen.

A method for activating molecular oxygen using nanometer zero-valent aluminum under alkaline conditions, comprising the following steps:

(1) Preparation of nano-zero-valent aluminum stock solution: place commercially purchased nano-zero-valent aluminum in a crimp-top bottle, immerse in 100 mL of ultrapure water, and then ultrasonically disperse for 30 minutes, as a nano-zero-valent aluminum stock solution;

(2) Sodium tripolyphosphate solution preparation: Weigh a fixed mass of sodium tripolyphosphate solid powder, dissolve it in ultrapure water and vibrate ultrasonically for 30 minutes, and prepare a high-concentration (250mM) sodium tripolyphosphate stock solution;

(3) Reaction system construction: at room temperature, use a 250mL tall beaker as a reactor, dissolve the equilibrium oxygen in the air by magnetic stirring, and add pollutants, sodium tripolyphosphate stock solution, and nano-zero-valent aluminum stock solution dropwise in sequence.

In the above method, the average particle diameter of the nanometer zero-valent aluminum described in step (1) is 50nm.

In the above method, the ultrasonic dispersion described in step (1) is carried out at an ultrasonic power of 40 kHz and a water bath temperature of 25°C.

In the above method, the sodium tripolyphosphate stock solution described in step (2) is prepared by adding sodium tripolyphosphate powder gradually into ultrapure water.

In the above method, the initial pH of the reaction solution in step (3) is 9.65-9.69.

In the above method, the magnetic stirring speed described in step (3) is 500rpm.

In the above method, the final total volume of the reaction solution described in step (3) is controlled to be the same.

A method of using inorganic salts to catalyze nanometer zero-valent aluminum to activate molecular oxygen can be used to degrade pollutants in wastewater.

The pollutant is selected from at least one of indigo dye or paracetamol.

The present invention is essentially different from existing methods for overcoming the problems of nZVAl in the application of advanced oxidation (an acidic solution dissolving the surface passivation layer in situ, and an organic complexing agent dissolving the passivation layer in situ). Sodium phosphate is used as a hydrolysis reagent, which dissolves the passivation layer on the surface of nZVAl in situ, and simultaneously controls the electron transfer between zero-valent aluminum and molecular oxygen in the inner core. This method not only solves the cumbersome process of ex-situ pretreatment of the passivation layer in an acidic solution, but also promotes the effective conversion of molecular oxygen into oxygen-containing free radicals and enhances the degradation of pollutants.

The present invention uses nZVAl as a catalyst to solve the problems of surface passivation layer and ineffective four-electron reaction, and at the same time reduce the environmental exposure risk of the system. In the present invention, the inorganic salt sodium tripolyphosphate (TPP) with low environmental risk is used as a hydrolysis reagent, and the complexing effect of TPP on Al ³⁺ can be used to dissolve the dense passivation layer on the surface of nZVAl; at the same time, the complex's unique "proton The "confinement effect" can hinder the competition of protons for electrons, and the formed surface complexes can reduce the electron conductivity of the inner core zero-valent aluminum to the solution interface, in order to transform the four-electron reduction reaction into a one-electron or two-electron reduction reaction. It provides a new idea for nZVAl to activate molecular oxygen to degrade pollutants.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

(1) The process of the present invention is simple, the conditions are mild and easy to control.

(2) The present invention uses sodium tripolyphosphate to catalyze nano-zero-valent aluminum to activate molecular oxygen, which not only improves the effective utilization of molecular oxygen, but also reduces the exposure risk of the reaction system to the environment.

(3) The present invention uses nanometer zero-valent aluminum to activate the equilibrium oxygen in the air, which simplifies the operation process and reduces the implementation cost.

(4) The present invention is carried out under alkaline conditions to widen the response range to the pH value of wastewater.

Description of drawings

Fig. 1 is the impact of different TPP concentrations on nZVAl activated molecular oxygen degradation indigo in embodiment 1;

Fig. 2 is the impact of different TPP concentrations on nZVAl activated molecular oxygen degradation paracetamol in embodiment 2;

Fig. 3 is the impact of different TPP concentrations on the change of solution pH in the process of nZVAl activated molecular oxygen degradation indigo in embodiment 3;

Fig. 4 is the impact of different initial pH values on nZVAl activated molecular oxygen degradation indigo in embodiment 4;

Fig. 5 is the influence that different TPP concentrations produce hydrogen peroxide in the reaction process in embodiment 5.

Detailed ways

In the following, the technical solutions in the embodiments of the present invention will be described in detail with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

It should be noted that, in this document, the term "comprising", "comprising" or any other variation thereof is intended to cover a non-exclusive inclusion such that a process, method, article or apparatus comprising a set of elements includes not only those elements, It also includes other elements not expressly listed, or elements inherent in the process, method, article, or apparatus.

In the present invention, Fig. 1 is the impact of different TPP concentrations on nZVAl activated molecular oxygen degradation of indigo in Example 1; Fig. 2 is the impact of different TPP concentrations on nZVAl activated molecular oxygen degradation of acetaminophen in Example 2; Fig. 3 is the embodiment The influence of different TPP concentrations in 3 on the solution pH change in the nZVAl activated molecular oxygen degradation process of indigo; Figure 4 is the impact of different initial pH values on nZVAl activated molecular oxygen degradation indigo in embodiment 4; Figure 5 is the different TPP in embodiment 5 The influence of concentration on the reaction process to produce hydrogen peroxide.

Example 1

The reactor is a 250mL tall beaker (unless otherwise specified below, this is the reactor), the concentration of nZVAl is 0.5g/L, the concentration of indigo is 50mg/L, and the concentration of TPP is 0, 0.5, 1.0, 5.0, 7.0, 10mM. The pH value is 9.34-9.63 (varies according to different concentrations of TPP), the magnetic stirring rate is 500 rpm, the reaction time is 110 min, and samples are taken at a fixed time. The sample taken was filtered through a 0.22 μm polyethersulfone filter head. In addition, for the experiment of _N2 quenching molecular oxygen, the reactor is a 500mL anaerobic bottle, the concentration of nZVAl is 0.5g/L, the concentration of indigo is 50mg/L, the concentration of TPP is 10mM, the initial pH value is 9.56, and the flow rate of _N2 aeration is 100mL/min , the magnetic stirring rate was 500rpm, the reaction time was 110min, and samples were taken at a fixed time. The sample taken was filtered through a 0.22 μm polyethersulfone filter head. The results are shown in Figure 1, indicating that TPP can significantly promote nZVAl to activate molecular oxygen to degrade indigo.

Example 2

The reaction conditions are nZVAl concentration 3.0g/L, paracetamol concentration 50μM, TPP concentration 0, 10, 20mM, initial pH value 9.34-9.63 (varies according to different concentrations of TPP), magnetic stirring rate 500rpm, reaction time 110min, sampling at a fixed time . The sample taken was filtered through a 0.22 μm polyethersulfone filter head. The results are shown in Figure 2, indicating that TPP can significantly promote nZVAl to activate molecular oxygen to degrade paracetamol.

Example 3

The reaction conditions are nZVAl concentration 0.5g/L, indigo concentration 50mg/L, TPP concentration 0, 0.5, 1.0, 5.0, 7.0, 10mM, initial pH value 9.34-9.63 (varies according to different concentrations of TPP), magnetic stirring rate 500rpm, The reaction time is 110min. Put the pH meter electrode into the reaction solution to detect the change of solution pH during the reaction in real time. The results are shown in Figure 3, when the TPP concentration is lower than 5mM, the solution pH continues to decrease; and when the TPP concentration is greater than 5mM, the solution pH first decreases and then increases. It shows that TPP affects the gain and loss of protons in the solution, that is, when the concentration of TPP is low, the hydrogen peroxide produced in the reaction process undergoes an electron loss oxidation reaction to generate O ₂ and H ⁺ ; while when the concentration of TPP is high, the hydrogen peroxide produced in the reaction process undergoes electron reduction The reaction produces OH ^- and OH.

Example 4

The reaction conditions were nZVAl concentration 0.5g/L, indigo concentration 50mg/L, TPP concentration 0mM, 10mM, initial pH value 3.98-9.63 (adjusted by NaOH and HCl), magnetic stirring rate 500rpm, reaction time 110min, sampling at a fixed time. The sample taken was filtered through a 0.22 μm polyethersulfone filter head. The results are shown in Figure 4. When the concentration of TPP is 10mM, the indigo can be effectively degraded under alkaline conditions; however, it is difficult to degrade indigo under neutral and acidic conditions. When the concentration of TPP was 0mM, indigo could be effectively degraded under acidic conditions, but it was difficult to degrade indigo under neutral and alkaline conditions. It shows that under alkaline conditions, TPP can simultaneously promote the dissolution of the nZVAl passivation layer and regulate the interfacial electron transfer, effectively catalyze molecular oxygen to generate oxygen-containing free radicals, and strengthen the degradation of indigo.

Example 5

The reaction conditions are nZVAl concentration 0.5g/L, indigo concentration 50mg/L, TPP concentration 0, 1.0, 5.0, 10mM, initial pH value 9.34-9.63 (varies according to different concentrations of TPP), magnetic stirring rate 500rpm, reaction time 110min, Samples were taken at a fixed time, and the concentration of hydrogen peroxide was determined by the potassium titanium oxalate method. In addition, for the experiment of _N2 quenching molecular oxygen, the implementation process is the same as that of Example 1. The results are shown in Figure 5, TPP can effectively promote the generation of hydrogen peroxide.

The present invention is essentially different from existing methods for overcoming the problems of nZVAl in the application of advanced oxidation (an acidic solution dissolving the surface passivation layer in situ, and an organic complexing agent dissolving the passivation layer in situ). Sodium phosphate is used as a hydrolysis reagent, which dissolves the passivation layer on the surface of nZVAl in situ, and simultaneously controls the electron transfer between zero-valent aluminum and molecular oxygen in the inner core. This method not only solves the cumbersome process of ex-situ pretreatment of the passivation layer in an acidic solution, but also promotes the effective conversion of molecular oxygen into oxygen-containing free radicals and enhances the degradation of pollutants.

The present invention uses nZVAl as a catalyst to solve the problems of surface passivation layer and ineffective four-electron reaction, and at the same time reduce the environmental exposure risk of the system. In the present invention, the inorganic salt sodium tripolyphosphate (TPP) with low environmental risk is used as a hydrolysis reagent, and the complexing effect of TPP on Al ³⁺ can be used to dissolve the dense passivation layer on the surface of nZVAl; at the same time, the complex's unique "proton The "confinement effect" can hinder the competition of protons for electrons, and the formed surface complexes can reduce the electron conductivity of the inner core zero-valent aluminum to the solution interface, in order to transform the four-electron reduction reaction into a one-electron or two-electron reduction reaction. It provides a new idea for nZVAl to activate molecular oxygen to degrade pollutants.

Compared with the prior art, the present invention has the following advantages and beneficial effects: (1) the process of the present invention is simple, the conditions are mild, and it is easy to control; Effective utilization of molecular oxygen, and reduce the risk of exposure of the reaction system to the environment; (3) the present invention uses nanometer zero-valent aluminum to activate equilibrium oxygen in the air, simplifying the operation process and reducing implementation costs; It is carried out under neutral conditions to broaden the response range to the pH value of wastewater.

Above-mentioned embodiment is the implementation mode and action effect that the present invention optimizes, but the implementation mode of the present invention is not strictly limited by above-mentioned embodiment, and the researcher of this field can be without departing from the spirit and scope of the present invention defined in the claims various changes in its detail or form.

Claims (10)

1. utilizing the method for nano zero-valence aluminium activate molecular oxygen under a kind of alkaline condition, which is characterized in that be with sodium tripolyphosphate Hydrolysing agent, nano zero-valence aluminium are catalyst, pass through solubilised state oxygen degradation pollutant in catalytic water solution.

2. the method according to claim 1, wherein the following steps are included:

(1) prepared by nano zero-valence aluminium stock solution: the nano zero-valence aluminium of commercialization purchase being placed in jaw bottle, 100mL is immersed in In ultrapure water, then ultrasonic disperse 30min, as nano zero-valence aluminium stock solution；

(2) sodium tripolyphosphate stock solution is prepared: being weighed fixed mass sodium tripolyphosphate solid powder, is dissolved in ultrapure water and through ultrasound Vibrate 30min, compounding high concentration (250mM) sodium tripolyphosphate stock solution；

(3) reaction system constructs: under room temperature, using 250mL high foot beaker as reactor, by balancing in magnetic agitation dissolved air Pollutant, sodium tripolyphosphate stock solution, nano zero-valence aluminium stock solution is successively added dropwise in state oxygen.

3. the method according to claim 1, wherein nano zero-valence aluminium average grain diameter described in step (1) is 50nm。

4. the method according to claim 1, wherein ultrasonic disperse described in step (1) is in ultrasonic power 40kHz, it carries out at 25 DEG C of bath temperature.

5. the method according to claim 1, wherein sodium tripolyphosphate stock solution described in step (2) use to It is prepared by the method for adding sodium tripolyphosphate powder by amount in ultrapure water.

6. the method according to claim 1, wherein the initial pH of reaction solution described in step (3) is 9.65- 9.69。

7. the method according to claim 1, wherein magnetic agitation speed described in step (3) is 500rpm.

8. the method according to claim 1, wherein reaction solution final total volume described in step (3) controls It is identical.

9. a kind of wastewater treatment method, wherein using method according to any one of claims 1 to 8 to contaminant degradation.

10. wastewater treatment method according to claim 9, wherein the pollutant is selected from bipseudoindoxyl dye or paracetamol At least one of more than.