CN110776079B - Method for promoting phenol pollutants to be efficiently photo-catalytically oxidized in situ by utilizing organic arsenic pollutants - Google Patents
Method for promoting phenol pollutants to be efficiently photo-catalytically oxidized in situ by utilizing organic arsenic pollutants Download PDFInfo
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Abstract
The invention discloses a method for promoting phenol pollutants to be efficiently photo-catalytically oxidized in situ by utilizing organic arsenic pollutants, which is to add TiO into wastewater to be treated in which the organic arsenic pollutants and the phenol pollutants simultaneously exist2The photocatalyst forms a photocatalytic degradation system, and the synergistic photocatalytic degradation of the organic arsenic pollutants and the phenol pollutants is realized under the illumination. The method of the invention passes through the organic arsenic pollutants and TiO in the water without additionally increasing the water treatment cost2The synergistic coupling of the photocatalyst realizes the remarkable improvement of the degradation efficiency and stability of the phenolic pollutants in situ.
Description
Technical Field
The invention belongs to the field of environmental protection, and particularly relates to efficient and synergistic oxidation removal of persistent organic pollutants.
Background
The photocatalytic water treatment technology is to carry out oxidative degradation and removal on environmental pollutants by combining a photocatalyst with a polluted water body and using light energy as drive. Based on TiO2The photocatalytic oxidation technology is used for repairing water body pollutionThe effective technical means are widely researched mainly because of the practical environment application potential of high activity, good stability, no toxicity, low price and the like, and the advantages of strong oxidation capability, no secondary pollution and the like. TiO 22The process of degrading environmental pollutants by photocatalytic oxidation is carried out by valence band holes (h)VB +) Hydroxyl radical (. OH) and superoxide radical (O)2 ·-) Initiated by an iso-oxidation state. The hydroxyl radical is a strong oxidant, is easy to react with organic matters adsorbed on the surface, and is a main active substance for removing pollutants.
TiO2The surface chemistry is determined by the particle shape and crystal form, which also determine the surface atomic arrangement, coordination, surface energy and structural defects as well as their electronic structure, surface adsorption and catalytic activity. Single crystal TiO with high energy {001} crystal face structure on surface2Single crystal TiO with surface crystal face structure as low energy {101} crystal face2Compared with the prior art, the method has many advantages in chemical catalytic performance. Mainly due to the single crystal TiO of high-energy {001} crystal face2The surface atoms with low coordination have a large number of dangling bonds, and the large number of unsaturated oxygen vacancies endow the surface atoms with high activation capacity. Unsaturated Ti on the surface of high-energy {001} crystal compared with the low-energy {101} crystal face5cHas strong interaction, is beneficial to the transfer of photogenerated electrons from a conduction band to molecular oxygen to form an oxidizing substance, and realizes the high-efficiency removal of most environmental pollutants and the purification of water quality.
Phenolic compounds are important industrial raw materials, and are mainly used in the industries of producing plastics, resins, dyes, medicines, pesticides, disinfectants, paints and the like. With the rapid development of industries such as oil refining, petrochemical industry, synthetic fiber and the like, the types and the amount of phenol environmental pollutants are increasing day by day. The phenolic compound is a prototype toxicant, has toxic action on all living individuals, has the characteristics of long-term residue, bioaccumulation, semi-volatility and high toxicity, can migrate for a long distance through various environmental media (atmosphere, water, organisms and the like), and has serious harm to human health and environment. The phenol can also invade the body by contacting, inhaling or orally administering to the skin or mucous membrane, and it is found in the cell plasmaWhen the protein contacts, a chemical reaction occurs, so that the protein is coagulated or denatured, and tissue damage, necrosis and general poisoning are caused. Because the pollution range of the phenol pollutants is wide and the harmfulness is large, the treatment of the phenol-containing waste water is increasingly concerned by environmental protection mechanisms of various countries. How to efficiently and energy-efficiently remove various phenolic pollutants in water and wastewater by oxidation through a photocatalytic technology is an important environmental protection topic. On one hand, the components of the phenolic pollutants in the water are various, the water quality is complex, the chemical structure of the phenolic pollutants is stable, and the biological toxicity is high; on the other hand, ordinary TiO2The strong hydrophilicity of the surface of the photocatalyst causes photoproduction hydroxyl free radicals to be localized on the surface of the photocatalyst and not to be effectively diffused into a solution for homogeneous reaction, so that the surface bound hydroxyl free radicals (OH) generated by taking surface hydroxyl functional groups as precursorsbound) The catalytic oxidation activity to the phenol pollutants is low, so that the photocatalytic degradation efficiency of the phenol pollutants is low, and the reaction kinetics is slow. However, if the oxidation of one pollutant can be utilized in situ to promote the efficient degradation of other pollutants, the process effectiveness and the economy of the overall treatment of the pollutants can be greatly improved, and the water treatment cost is remarkably reduced.
Organic arsenic represented by Roxarsone (ROX) is widely used as an additive in animal husbandry for controlling coccidial intestinal parasites, promoting growth and improving meat color. However, about 90% of the produced feces are directly used as agricultural fertilizers, causing secondary environmental pollution to local soil, surface water and underground water. Moreover, these organic arsenic compounds can be converted to inorganic arsenic by biological or non-biological processes, with higher toxicity and fluidity. Inorganic arsenic, which is mainly present in the form of arsenite (as (iii)) or arsenate (as (v)), is one of the most typical toxic and harmful pollutants in ground water and industrial wastewater. Therefore, similar to phenolic pollutants, efficient oxidative removal of organic arsenic pollutants is also critical. At present, the methods commonly used at home and abroad mainly comprise a chemical oxidation method, a photocatalytic oxidation method, a biological oxidation method and the like. The chemical oxidation method mainly uses H2O2、MnO2And an oxidizing agent such as ozone, butThe cost of the oxidant is high, and the addition of a large amount of the oxidant is easy to cause secondary pollution; the biological oxidation method has long reaction period and poor treatment effect. Based on TiO2The photocatalytic oxidation method has the important technical characteristics of environmental protection, energy conservation, no secondary pollution and the like, and is a water treatment means for removing organic arsenic pollutants by high-efficiency oxidation.
Disclosure of Invention
In order to solve the increasingly serious pollution problem of organic arsenic and phenolic compounds, the invention provides a method for promoting the efficient photocatalytic oxidation of phenolic pollutants in situ by using organic arsenic pollutants, and aims to solve the problem of increasing pollution of organic arsenic and phenolic compounds by using single crystal TiO2The catalytic oxidation reaction under ultraviolet illumination efficiently degrades organic arsenic and simultaneously realizes the modification of the surface of the catalyst, thereby further realizing the efficient removal of the phenol pollutants.
In order to solve the technical problem, the invention adopts the following technical scheme:
a method for promoting the efficient photocatalytic oxidation of phenolic pollutants in situ by using organic arsenic pollutants is characterized by comprising the following steps: adding TiO into the wastewater to be treated with organic arsenic pollutants and phenolic pollutants simultaneously2The photocatalyst forms a photocatalytic degradation system, and the synergistic photocatalytic degradation of the organic arsenic pollutants and the phenol pollutants is realized under the illumination. The water treatment method for promoting the efficient removal of organic pollutants of other components by utilizing the synergistic effect of the organic arsenic pollutants in the water in situ effectively realizes the in-situ removal of different components in the water body on the premise of not additionally increasing the cost of the photocatalysis technologyThe organic pollutants are removed by synergistic, efficient and rapid degradation.
In the photocatalytic degradation process, inorganic arsenic As (V) generated and released in the catalytic degradation process of the organic arsenic pollutants is rapidly and strongly adsorbed on TiO through Ti-As chemical bonds2The surface of the photocatalyst forms a hydrophobic inert photocatalytic interface (Ti-OH + As) terminated by Ti-As bonds3+/5+→Ti-As+OH-) Thereby changing TiO2The photocatalysis mechanism of the photocatalyst is to generate free hydroxyl groups (OH) by taking free water molecules and liquid-phase hydroxide radicals as precursorsfree) And the catalytic degradation of the phenolic pollutants is realized.
Further, the TiO2Photocatalyst is crystal face regulating TiO2The photocatalyst has a single crystal crystallographic structure and a regular quadrilateral flake micro-morphology, and the surface of the photocatalyst is simultaneously exposed with a high-energy {001} polar crystal plane and a low-energy {101} nonpolar crystal plane. Further, the crystal face-regulated TiO2The photocatalyst is prepared by the following method: adding 10-50 mL of tetrabutyl titanate into 15-30 mL of HF aqueous solution with the concentration of 24 wt.%, and uniformly stirring to obtain a precursor solution; transferring the precursor solution into an autoclave, and reacting at a constant temperature of 100-200 ℃ for 12-48 h; cooling to room temperature after the reaction is finished, washing the obtained product for multiple times by ethanol, 0.1M NaOH and distilled water in sequence, then drying, and calcining for 5 hours at 400 ℃ in an air atmosphere to obtain the crystal face regulating TiO2A photocatalyst.
Further, in the photocatalytic degradation system, the TiO2The addition amount of the photocatalyst is 0.2-2.0 g/L, the concentration of the organic arsenic pollutants is 5.0-50.0 mg/L, the concentration of the phenol pollutants is 0.0-50.0 mg/L, and the pH value is 3.0-9.0.
Further, the organic arsenic-based pollutant is Roxarsone (ROX), and the phenolic pollutant is at least one of p-chlorophenol (4-CP) and phenol.
Further, the method for promoting the phenol pollutants to be efficiently photo-catalytically oxidized in situ by using the organic arsenic pollutants comprises the following steps: to-be-treated for determination of phenolic-containing contaminantsThe concentration of the organic arsenic pollutants in the wastewater is regulated and controlled in a mode of diluting or adding the organic arsenic pollutants, so that the concentration of the organic arsenic pollutants is maintained at 5.0-50.0 mg/L; adding TiO into the simulation wastewater to be treated2The addition amount of the photocatalyst is 0.2-2.0 g/L, and a photocatalytic degradation system is formed; then regulating and controlling the pH value of the photocatalytic degradation system to be 3.0-9.0; and finally, magnetically stirring at 100-500 rpm for 10-60 min under a dark condition, and performing photocatalytic degradation reaction for 1-8 h under ultraviolet irradiation, so as to complete the synergistic photocatalytic degradation of the organic arsenic pollutants and the phenol pollutants.
The working principle of the invention is as follows: as shown in FIG. 1, the presence of ROX favors the formation of a free hydroxyl group (. OH)free) Because the arsenic ions generated after ROX oxidation replace the surface hydroxyl groups of the catalyst, h is suppressedVB +Reaction with hydroxyl radicals on the surface of the catalyst, i.e. inhibition of OHboundAnd (4) generating. But it enhances hVB +Reaction with water molecule promotes OHfreeAnd (4) generating. Due to OHboundGenerally only reacts with contaminants near the catalyst surface, oxidatively degrading it, and OHfreeIt can diffuse out of the catalyst surface and react with the contaminants in the bulk solution. OH is thusfreeThe oxidative degradation capability of the phenolic pollutants is higher than OHboundAnd phenolic contaminants in TiO2The adsorption amount on the surface is small. Thus, by ROX on TiO2Enrichment oxidation modification of surface to generate OHfreeThe method can promote the degradation of the phenol pollutants, can economically and effectively remove ROX, and synchronously realize the high-efficiency conversion of the organic arsenic pollutants and the phenol pollutants.
The invention provides a method for preparing a titanium dioxide (TiO)2Under the irradiation of ultraviolet light, the novel method for promoting the high-efficiency removal of phenol pollutants in situ by utilizing the catalytic degradation of ROX is suitable for the polluted wastewater simultaneously containing arsenic and phenol pollutants, and As (V) generated by the oxidation of organic arsenic is in TiO2Adsorption of the surface to form a hydrophobic inert photocatalytic interface terminated by Ti-As bonds, thereby promoting the generation of free radicalsSuch radicals are formed, and have a stronger degrading effect on phenolic contaminants than surface bound hydroxyl radicals.
The invention has the beneficial effects that:
(1) the invention obviously improves the degradation efficiency and stability of the phenol pollutants on the premise of not needing the oxidation cost of the organic arsenic pollutants, thereby finally reducing the total cost of the water treatment process and realizing the unification of the high efficiency and the economy of the water treatment process in the rapid degradation process of the organic pollutants difficult to degrade.
(2) The invention makes use of TiO2The strong oxidizing property of the photocatalytic system and the specific adsorption of arsenic modify the surface of the catalyst in situ, improve the oxidizing property of the photocatalytic pollutant, synchronously complete the oxidative degradation of organic arsenic pollutants and the synchronous and efficient removal of phenol pollutants, and provide a new technical approach for the efficient treatment of wastewater containing arsenic and phenol.
(3) The invention utilizes the monocrystal TiO of high-energy {001} polar crystal face2As a semiconductor material with important industrial value, the semiconductor material has the characteristics of simple structure, high performance efficiency, stable structure, low price, easy preparation, safety, no toxicity and the like, so that the semiconductor material is extremely friendly to the environment and has remarkable economic and environmental benefits.
(4) The photocatalyst used in the invention has stable structure, outstanding physicochemical properties, excellent catalytic activity, low price, no toxicity and good practical prospect, and the used organic arsenic pollutants are difficult to be effectively removed by other conventional chemical and biological oxidation technologies.
(5) The invention utilizes OHfreeThe oxidative degradation capability to phenolic pollutants is far more than OHboundThe existence of ROX can modify-OH end capping in situ and TiO with extremely strong hydrophilicity2Surface chemical property of catalyst, promoting OHfreeThe generation and the directional regulation and control of the photocatalytic degradation mechanism greatly improve the overall treatment efficiency of the wastewater containing arsenic and phenol and reduce the process energy consumption.
(6) The invention has the advantages of ingenious conception, exquisite design, obvious effect and outstanding advantages, and has obvious significance for the efficient removal and mechanism regulation of multi-component, complex-property and persistent refractory organic pollutants in actual sewage and wastewater.
Drawings
FIG. 1 is a schematic diagram of the principle of the present invention for promoting the efficient photocatalytic oxidation of phenolic pollutants in situ by using organic arsenic pollutants.
FIG. 2 shows a crystal plane-controlled TiO prepared in example 12Scanning electron micrographs (a) and transmission electron micrographs (b) of the photocatalyst.
FIG. 3 is a graph of the contaminant concentration as a function of degradation time for different experimental systems in experiment 1 of example 2.
FIG. 4 is the effect of ROX concentration on 4-CP degradation efficiency in experiment 2 of example 2, where: FIG. 4(a) shows different concentrations of ROX as a function of degradation time; FIG. 4(b) shows the change in 4-CP concentration with degradation time at different concentrations of ROX.
FIG. 5 is a graph comparing the degradation rates of 4-CP in example 3 at different pH conditions.
FIG. 6 is a graph comparing the degradation rates of 4-CP in example 4 at different cycle numbers.
FIG. 7 is a graph of contaminant concentration as a function of degradation time for different experimental systems in experiment 1 of example 5.
FIG. 8 is a graph of the effect of ROX concentration on phenol degradation efficiency in experiment 2 of example 5, where: FIG. 8(a) shows different concentrations of ROX as a function of degradation time; FIG. 8(b) shows the change in phenol concentration with degradation time at different concentrations of ROX.
Detailed Description
The following examples are given for the detailed implementation and specific operation of the present invention, but the scope of the present invention is not limited to the following examples.
The device used in the following examples mainly comprises a 50mL beaker, a magnetic stirrer, a 15W UV lamp tube and the like, all of which are placed in a dark operation cabinet to integrally construct the whole photocatalytic reactor unit module set, so as to avoid the interference of external natural light on the whole system and the possible radiation pollution of an ultraviolet light source to the environment and human body.
The solutions used in the following examples were all 18.3 M.OMEGA.cm-1And (4) preparing ultrapure water.
Example 1 crystal face-controlled TiO2Preparation of the photocatalyst
TiO used in this example2Photocatalyst is crystal face regulating TiO2The photocatalyst has a single crystal crystallographic structure, is in a form of nano crystal particle, has a regular quadrilateral flake micro-morphology, and has a high-energy {001} polar crystal face and a low-energy {101} nonpolar crystal face exposed on the surface at the same time, and the preparation method comprises the following steps: adding 20mL of tetrabutyl titanate into 20mL of HF aqueous solution with the concentration of 24 wt.%, and uniformly stirring to obtain a precursor solution; transferring the precursor solution into a high-pressure kettle, and reacting at the constant temperature of 170 ℃ for 24 hours; cooling to room temperature after the reaction is finished, washing the obtained product for multiple times by ethanol, concentrated alkali and distilled water, drying at 60 ℃ for 12h, and calcining at 400 ℃ for 5h in air atmosphere to obtain the crystal face-regulated TiO2A photocatalyst.
FIG. 2(a) and FIG. 2(b) are respectively a crystal plane-controlled TiO prepared in this example2Scanning electron micrographs and transmission electron micrographs of the photocatalyst.
Example 2 Effect of ROX in synergistic degradation System of chlorophenol (4-CP) and ROX
1. In order to verify the influence of ROX in a synergistic degradation system of chlorophenol (4-CP) and ROX, three groups of experimental systems are set:
first, the crystal plane-modified TiO prepared in example 1 was ultrasonically cleaned in a 50mL beaker at room temperature2Dispersing in deionized water with the dispersion concentration of 0.7 g/L;
then: in the first set of experimental systems, 4-CP was added to the beaker to a concentration of 10 ppm; in the second set of experiments, 4-CP and ROX stock solutions were added to the beaker to a concentration of 10ppm for both; in the third set of experimental systems, the ROX stock solution was added to the beaker to a concentration of 10 ppm. The pH of the three systems was adjusted to 6 by 0.1M HCl or NaOH.
And finally, magnetically stirring the obtained systems at 300rpm for 30min under a dark condition, fully performing adsorption balance on the surface of the catalyst, starting ultraviolet irradiation, performing photocatalytic degradation reaction, wherein the reaction time lasts for 8h, and sampling in the reaction process to detect the concentration of pollutants. FIG. 3 shows the change of 4-CP concentration with degradation time in the first set of experimental systems (without ROX (4-CP)), the change of 4-CP concentration with degradation time in the second set of experimental systems (with ROX (4-CP)), and the change of ROX concentration with degradation time in the third set of experimental systems (ROX)). It can be seen that when ROX (10ppm) exists, the degradation effect on 4-CP (10ppm) is obviously enhanced, so that the cost for removing ROX is saved, and the degradation of 4-CP is promoted.
2. In order to verify the influence of the concentration of ROX on the degradation efficiency of 4-CP in the synergistic degradation system of chlorophenol (4-CP) and ROX, the following experiment is set up:
first, the crystal plane-modified TiO prepared in example 1 was ultrasonically cleaned in a 50mL beaker at room temperature2Dispersing in deionized water with the dispersion concentration of 0.7 g/L; then adding 4-CP into the beaker until the concentration of the 4-CP is 10 ppm; adding ROX into the beaker until the concentration is 0ppm, 5ppm, 10ppm, 15ppm and 20ppm respectively; finally, the system pH was adjusted to 6 by 0.1M HCl or NaOH. And magnetically stirring the obtained suspension for 30min at 300rpm under a dark condition, fully performing adsorption balance on the surface of the catalyst, starting ultraviolet irradiation, performing photocatalytic degradation reaction, wherein the reaction time lasts for 8h, and sampling in the reaction process to detect the concentration of pollutants.
FIG. 4(a) shows different concentrations of ROX as a function of degradation time; FIG. 4(b) shows the change in 4-CP concentration with degradation time at different concentrations of ROX. As can be seen from the figure, ROX has both inhibitory and stimulatory effects on 4-CP degradation. The inhibition effect is that ROX and 4-CP compete for hydroxyl free radical, but ROX can modify the surface of catalyst to a certain extent, which is beneficial to OHfreeSo that an appropriate concentration of ROX can effectively promote the degradation of 4-CP. When the concentration of ROX is less than 10ppm, the concentration of ROX increases to compete with 4-CP to consume the oxidation-active substance, but at the same time, the surface of the catalyst is modified to promote OHfreeThereby accelerating the degradation of 4-CP. Therefore, this stage4-CP achieves higher removal rates with increasing ROX concentration. However, when the concentration of ROX exceeds 10ppm, the degree of positive effect of ROX on 4-CP degradation remains unchanged, indicating that the adsorption of ROX by the catalyst approaches saturation. And ROX is a competitive object of the oxidizing substance of 4-CP, the inhibition degree of the ROX is increased along with the increase of the concentration of ROX, so when the concentration of ROX exceeds 10ppm, the ROX has inhibition effect on the degradation of 4-CP. As can be seen from fig. 4(a), although the removal rate of ROX decreases with the increase of the concentration of ROX, the removal rate still reaches 95%, which indicates that the system has higher efficiency for removing contaminants.
Example 3 Effect of pH on synergistic degradation System of chlorophenol (4-CP) and ROX
To verify the effect of pH on the chlorophenol (4-CP) and ROX synergistic degradation system, the following experiment was set up:
first, the crystal plane-modified TiO prepared in example 1 was ultrasonically cleaned in a 50mL beaker at room temperature2Dispersing in deionized water with the dispersion concentration of 0.7 g/L; the 4-CP and ROX stock solutions were then added to the beaker to a concentration of 10ppm each. Finally, the system pH is adjusted to 3, 4, 5, 6, 7, 8 and 9 respectively by 0.1M HCl or NaOH. And magnetically stirring the obtained suspension for 30min at 300rpm under a dark condition, fully performing adsorption balance on the surface of the catalyst, starting ultraviolet irradiation, performing photocatalytic degradation reaction, wherein the reaction time lasts for 8h, and sampling in the reaction process to detect the concentration of pollutants.
FIG. 5 is a graph comparing the degradation rate of 4-CP at different pH conditions. OH formation depends on the pH of the solution, and the surface charge of the catalyst and the morphology of As are also influenced by the pH, i.e.OHfreeAnd thus has a significant effect on the degradation of 4-CP. In the pH range of 3-6, although the surface of the catalyst is positively charged under the condition of lower pH, the adsorption with ROX is facilitated, but more cations are contained in the aqueous solution, the arsenic is more easily combined, and the generation of active substances OH is not facilitatedfreeThus, the degradation ability of 4-CP is worse as the pH is decreased. Under alkaline conditions, TiO increases with pH2The surface of (A) is mainly negatively charged, inhibiting the production of arsenate anions, OH, which are oxidation products of ROXfreeAnd also correspondingly reduced, so that the removal rate of the 4-CP is slightly reduced. Therefore, the pH value is 6, which is similar to the pH value of natural water, and the method has good practicability and is more favorable for being applied to actual water environment.
Example 4 Cyclic stability test of synergistic degradation System of chlorophenol (4-CP) and ROX
To verify the practical feasibility of the simultaneous oxidation process of 4-CP and ROX and the stability and activity of the catalyst, the following experiments were set up:
first, the crystal plane-modified TiO prepared in example 1 was ultrasonically cleaned in a 50mL beaker at room temperature2Dispersing in deionized water with the dispersion concentration of 0.7 g/L; the 4-CP and ROX stock solutions were then added to the beaker to a concentration of 10ppm each. Finally, the pH of the system is adjusted to 6 by 0.1M HCl or NaOH. And magnetically stirring the obtained suspension for 30min at 300rpm in a dark condition, fully performing adsorption balance on the surface of the catalyst, starting ultraviolet irradiation, performing photocatalytic degradation reaction, lasting for 8h, and immediately sampling and detecting after the reaction is finished. After each reaction, the catalyst was recovered by filtering the reaction solution, washed several times with distilled water, and then dried at 60 ℃ for reuse.
The photocatalytic reaction was repeated up to five cycles at the same time intervals and experimental conditions. FIG. 6 is a graph comparing the degradation rate of 4-CP at different cycle numbers. It can be seen that the 4-CP removal rate remained above 60% after 5 cycles. Similar concentrations at the same time intervals in the recycle tests strongly demonstrate the superior structural and catalytic stability of the catalyst and also the reliability of the process.
Example 5 Effect of ROX in synergistic degradation System of phenol and ROX
1. In order to verify the influence of ROX in a synergistic degradation system of phenol and ROX, three groups of experimental systems are set:
first, the crystal plane-modified TiO prepared in example 1 was ultrasonically cleaned in a 50mL beaker at room temperature2Dispersing in deionized water with the dispersion concentration of 0.7 g/L;
then: in the first set of experimental systems, phenol was added to the beaker to a concentration of 10 ppm; in the second set of experiments, phenol and ROX stock solution were added to the beaker to a concentration of 10ppm for both; in the third set of experimental systems, the ROX stock solution was added to the beaker to a concentration of 10 ppm. The pH of the three systems was adjusted to 6 by 0.1M HCl or NaOH.
And finally, magnetically stirring the obtained systems at 300rpm for 30min under a dark condition, fully performing adsorption balance on the surface of the catalyst, starting ultraviolet irradiation, performing photocatalytic degradation reaction, wherein the reaction time lasts for 8h, and sampling in the reaction process to detect the concentration of pollutants.
Fig. 7 shows the change of phenol concentration with degradation time in the first set of experimental systems (no addition of ROX (phenol)), the change of phenol concentration with degradation time in the second set of experimental systems (addition of ROX (phenol)), and the change of ROX concentration with degradation time in the third set of experimental systems (ROX)). It can be seen that, in accordance with the experimental results of example 2, when ROX (10ppm) was present, the degradation effect on phenol (10ppm) was significantly enhanced.
2. In order to verify the influence of the concentration of ROX on the degradation efficiency of 4-CP in the synergistic degradation system of phenol and ROX, the following experiment is set:
first, the crystal plane-modified TiO prepared in example 1 was ultrasonically cleaned in a 50mL beaker at room temperature2Dispersing in deionized water with the dispersion concentration of 0.7 g/L; then adding phenol to the beaker to a concentration of 10 ppm; adding ROX into the beaker until the concentration is 0ppm, 5ppm, 10ppm, 15ppm and 20ppm respectively; finally, the system pH was adjusted to 6 by 0.1M HCl or NaOH. And magnetically stirring the obtained suspension for 30min at 300rpm under a dark condition, fully performing adsorption balance on the surface of the catalyst, starting ultraviolet irradiation, performing photocatalytic degradation reaction, wherein the reaction time lasts for 8h, and sampling in the reaction process to detect the concentration of pollutants.
FIG. 8(a) shows different concentrations of ROX as a function of degradation time; FIG. 8(b) shows the change in phenol concentration with degradation time at different concentrations of ROX. It can be seen that the results are consistent with those of example 2.
It can be seen that TiO is used2In the ultraviolet lightUnder irradiation, catalytic oxidation of organic arsenic pollutants is utilized to modify and promote TiO in situ2The coupling synergistic technical characteristic of the photocatalytic efficient degradation of the phenol pollutants has obvious technical advantages and wide application prospect.
Claims (6)
1. A method for promoting the efficient photocatalytic oxidation of phenolic pollutants in situ by using organic arsenic pollutants is characterized by comprising the following steps: adding TiO into the wastewater to be treated with organic arsenic pollutants and phenolic pollutants simultaneously2The photocatalyst forms a photocatalytic degradation system, and the synergistic photocatalytic degradation of the organic arsenic pollutants and the phenol pollutants is realized under the illumination;
the TiO is2Photocatalyst is crystal face regulating TiO2The photocatalyst has a single-crystal crystallographic structure, and the surface of the photocatalyst is simultaneously exposed with a {001} polar crystal plane and a {101} nonpolar crystal plane.
2. The method of claim 1, wherein: in the photocatalytic degradation process, inorganic arsenic generated and released in the catalytic degradation process of the organic arsenic pollutants is adsorbed on TiO through Ti-As chemical bonds2The surface of the photocatalyst is formed, and a hydrophobic inert photocatalytic interface which is terminated by Ti-As bonds is formed, thereby changing TiO2The photocatalysis mechanism of the photocatalyst takes free water molecules and liquid-phase hydroxide radicals as precursors to generate free hydroxyl groups, thereby realizing the catalytic degradation of phenolic pollutants.
3. The method of claim 1, wherein: the crystal face regulating TiO2The photocatalyst is prepared by the following method: adding 10-50 mL of tetrabutyl titanate into 15-30 mL of HF aqueous solution with the concentration of 24 wt.%, and uniformly stirring to obtain a precursor solution; transferring the precursor solution into an autoclave, and reacting at a constant temperature of 100-200 ℃ for 12-48 h; cooling to room temperature after the reaction is finished, washing and drying the obtained product, and calcining for 5 hours at 400 ℃ in the air atmosphere to obtain the crystal face regulating TiO2A photocatalyst.
4. The method according to claim 1 or 2, characterized in that: in the photocatalytic degradation system, the TiO2The addition amount of the photocatalyst is 0.2-2.0 g/L, the concentration of the organic arsenic pollutants is 5.0-50.0 mg/L, the concentration of the phenol pollutants is 0.0-50.0 mg/L, and the pH value is 3.0-9.0.
5. The method according to claim 1 or 2, characterized in that: the organic arsenic pollutant is roxarsone, and the phenolic pollutant is at least one of p-chlorophenol and phenol.
6. The method according to claim 1 or 2, characterized in that it is carried out as follows:
measuring the concentration of the organic arsenic pollutants in the wastewater to be treated containing the phenol pollutants, and regulating and controlling the concentration of the organic arsenic pollutants in a manner of diluting or adding the organic arsenic pollutants to maintain the concentration of the organic arsenic pollutants at 5.0-50.0 mg/L; adding TiO into the wastewater to be treated2The addition amount of the photocatalyst is 0.2-2.0 g/L, and a photocatalytic degradation system is formed; then regulating and controlling the pH value of the photocatalytic degradation system to be 3.0-9.0; and finally, magnetically stirring at 100-500 rpm for 10-60 min under a dark condition, and performing photocatalytic degradation reaction for 1-8 h under ultraviolet irradiation, so as to complete the synergistic photocatalytic degradation of the organic arsenic pollutants and the phenol pollutants.
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