CN111547906B - Method for deeply degrading organic pollutants in water by fully utilizing bismuth-silver oxide - Google Patents
Method for deeply degrading organic pollutants in water by fully utilizing bismuth-silver oxide Download PDFInfo
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- CN111547906B CN111547906B CN202010393568.XA CN202010393568A CN111547906B CN 111547906 B CN111547906 B CN 111547906B CN 202010393568 A CN202010393568 A CN 202010393568A CN 111547906 B CN111547906 B CN 111547906B
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- CJQSUEBYPDGXEY-UHFFFAOYSA-N bismuth;oxosilver Chemical compound [Bi].[Ag]=O CJQSUEBYPDGXEY-UHFFFAOYSA-N 0.000 title claims abstract description 142
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- PNYYBUOBTVHFDN-UHFFFAOYSA-N sodium bismuthate Chemical compound [Na+].[O-][Bi](=O)=O PNYYBUOBTVHFDN-UHFFFAOYSA-N 0.000 claims abstract description 47
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- VUZPPFZMUPKLLV-UHFFFAOYSA-N methane;hydrate Chemical compound C.O VUZPPFZMUPKLLV-UHFFFAOYSA-N 0.000 description 1
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- AAAQKTZKLRYKHR-UHFFFAOYSA-N triphenylmethane Chemical compound C1=CC=CC=C1C(C=1C=CC=CC=1)C1=CC=CC=C1 AAAQKTZKLRYKHR-UHFFFAOYSA-N 0.000 description 1
- 238000003911 water pollution Methods 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F9/00—Multistage treatment of water, waste water or sewage
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/001—Processes for the treatment of water whereby the filtration technique is of importance
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/30—Treatment of water, waste water, or sewage by irradiation
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/72—Treatment of water, waste water, or sewage by oxidation
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F2001/007—Processes including a sedimentation step
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/20—Heavy metals or heavy metal compounds
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/30—Organic compounds
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/30—Organic compounds
- C02F2101/308—Dyes; Colorants; Fluorescent agents
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2301/00—General aspects of water treatment
- C02F2301/08—Multistage treatments, e.g. repetition of the same process step under different conditions
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2305/00—Use of specific compounds during water treatment
- C02F2305/02—Specific form of oxidant
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2305/00—Use of specific compounds during water treatment
- C02F2305/10—Photocatalysts
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Abstract
The invention discloses a method for deeply degrading organic pollutants in water by fully utilizing bismuth silver oxide. The method comprises the following steps: pre-treating and adjusting pH; the first stage is as follows: adding sodium bismuthate and silver nitrate into the wastewater to generate bismuth silver oxide for oxidation degradation reaction; after degradation for a certain time, if the pollutant removal rate is more than or equal to 85 percent, collecting the wastewater, and entering a second stage for treatment, wherein the bismuth-silver oxide is reused for the oxidative degradation treatment of the wastewater of the next batch; if the pollutant removal rate is less than 85% but more than 3%, the bismuth silver oxide is reused for the oxidative degradation treatment of the wastewater of the next batch; if the pollutant removal rate is less than 3%, the bismuth silver oxide is considered to completely lose the oxidation activity, and the bismuth silver oxide is washed and then put into a second stage to be used as a photocatalyst to carry out photocatalytic degradation reaction with the wastewater under the illumination. The two-stage treatment method realizes the full life cycle utilization of the sodium bismuthate, so that bismuth silver oxides with different life cycles can play corresponding functions in different wastewater treatment stages.
Description
Technical Field
The invention belongs to the technical field of water pollution treatment, and particularly relates to a method for deeply degrading organic pollutants in water by fully utilizing bismuth silver oxide.
Background
With the development of industry, common chemical products or intermediates such as halogenated compounds, nitro compounds, amino compounds, aniline compounds, phenols and other organic compounds are discharged or leaked into natural water bodies to become organic pollutants in water. They are generally toxic or carcinogenic to varying degrees, severely affecting the growth of aquatic organisms and microorganisms, and are also quite harmful to human health. The traditional organic wastewater treatment method comprises an adsorption method, a chemical coagulation method, a membrane separation method, an anaerobic/aerobic biological treatment method and the like, wherein the first three methods all adopt the principle of enrichment and concentration, and do not really remove organic pollutants, and the biological treatment method can effectively remove part of pollutants, but most of wastewater has the characteristics of high organic matter concentration, poor biodegradability, even biotoxicity and the like, so that the traditional biological method cannot achieve ideal effect on the treatment. In addition, the most widely studied methods include chemical degradation processes in which contaminant molecules are oxidized or reduced to break down into small molecule compounds, even completely mineralized into structures such as carbon dioxide, water, nitrogen, aldehydes, acids, and sulfates. Contaminant oxidation typically involves the use of oxidizing agents such as chlorine and chlorine dioxide, ozone, hydrogen peroxide, and the like. The conventional chemical oxidation method has long requirement on the retention time of the wastewater, has limited degradation effect and even can generate metabolites with higher toxicity, such as chlorinated organic matters and the like. In recent years, advanced oxidation technologies including visible light catalysis have been the focus of research on wastewater treatment due to the characteristics that the advanced oxidation technologies can generate active free radicals with strong oxidizing property, so that many organic molecules with stable structures and even difficult decomposition by microorganisms can be converted into non-toxic and harmless biodegradable small molecular substances, and most of end-point products of the reaction are carbon dioxide, water and inorganic ions. However, the objective problems and development directions of the solar photocatalytic degradation technology for treating wastewater are as follows: (1) the high-efficiency visible-light-driven photocatalyst is generally complex in synthesis and high in precision control requirement, and the commercial practical application of the technology is limited; (2) active free radicals produced by photocatalysis are highly efficient and therefore react nonselectively with contaminant molecules, such as by pre-degrading contaminants in combination with other technologies, while efficient photocatalytic free radicals are fully utilized to concentrate on subsequent mineralization, which will greatly enhance the advanced treatment capabilities of photocatalytic degradation technologies (Serli, E.Synthesis effects of nanoparticles combined with a photocatalytic analysis in the degradation of an azo dye [ J ]. Physical Chemistry. 2002,4(24), 6123-.
Perovskite metal oxides are widely used in the fields of environmental protection, industrial catalysis and the like because of stable crystal structures, unique electromagnetic properties, and high activities of oxidation reduction, hydrogenolysis, isomerization, electrocatalysis and the like. The sodium bismuthate is a novel material with excellent performance and wide application, and researches show that the sodium bismuthate has higher visible light catalytic activity and has wide application prospect in green treatment of environmental pollution by utilizing solar energy (Kako T, Zou Z G, Katagiri M, et al. composition of organic compositions over NaBiO)3 under visible light irradiation[J].Chemistry of Materials,2007,19(2):198-202)。
When sodium bismuthate is used as a photocatalyst for a long time and has a tendency of inactivation, patent number ZL200910029442.8 introduces bismuth silver oxide generated by mixing and reacting sodium bismuthate and silver nitrate, and the bismuth silver oxide can degrade triphenylmethane dyes only under the condition of stirring and contact, so that the application of the sodium bismuthate material in organic sewage treatment is expanded. The method utilizes the oxidability of the sodium bismuthate to decolor the dye wastewater, does not need additional energy, has higher decoloring speed on the dye wastewater, but has limited deep mineralization capability (namely, the capability of the bismuth silver oxide for deeply degrading organic pollutants in water is limited).
Thereafter, the patent number ZL 201310204545.X provides a method for organically combining the oxidation performance of sodium bismuthate and the solar photocatalysis performance and quickly and deeply degrading organic dye wastewater at low cost aiming at the problem that the deep mineralization capacity of bismuth silver oxide is limited. The two-section type combined method aims at the degradation characteristics of dye wastewater, and is characterized in that: firstly, after the dye wastewater is basically decolorized by using bismuth silver oxide, sodium bismuthate is added as a catalyst to generate visible light catalytic reaction under the irradiation of sunlight. The two-stage treatment method effectively solves two problems of the visible light catalytic degradation technology to a certain extent: not only utilizes the easily obtained high-efficiency photocatalytic material, but also adds an oxidation pretreatment stage before the photocatalytic stage. However, the method introduces a brand-new sodium bismuthate catalytic material in the second stage, and the bismuth silver oxide used in the first stage is an oxidant, so that the bismuth silver oxide cannot be used for pollution treatment after the oxidizing efficiency of the oxidant is lost (along with the continuous degradation of pollutants in the first stage, the oxidizing capability of the bismuth silver oxide is certainly gradually lost). Therefore, from the perspective of fully utilizing materials, the patent number ZL 201310204545.X only fully utilizes the catalytic function of sodium bismuthate, namely provides a method for converting the sodium bismuthate with deactivated catalytic activity into the bismuth silver oxide and then continuously utilizing the oxidation function of the bismuth silver oxide. However, whether the bismuth silver oxide with the fully utilized oxidation function has other uses or not can be converted into functional materials with other properties, so that the environmental function of the bismuth silver oxide is continuously and deeply expanded, and the research is needed.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: overcomes the defects of the prior art, and provides a method for fully utilizing the environmental function of the bismuth silver oxide, namely a method for deeply degrading organic pollutants in water based on fully utilizing the bismuth silver oxide.
The invention is further improved on the basis of the patent number ZL 201310204545.X, and also utilizes a two-stage organic wastewater treatment method, namely the first stage also utilizes bismuth silver oxide to rapidly degrade pollutants, and the second stage utilizes a photocatalysis method to carry out secondary deep degradation on the degraded wastewater, but the method is greatly different from the method of the patent number ZL 201310204545. X. In contrast, the present invention has the following advantages: (1) after the first stage water treatment material is used, the first stage water treatment material can be used as a second stage water treatment material after simple treatment, but a brand new material is required to be introduced during the second stage water treatment. The water treatment function of the bismuth silver oxide is further expanded instead of sodium bismuthate, the aim of making the best use of the bismuth silver oxide at different stages is achieved according to the structural change of the bismuth silver oxide in the using process, and the targeted application effect of the bismuth silver oxide in the whole life cycle is achieved; (2) on the premise of fully utilizing the bismuth silver oxide, key process and step parameters in the whole set of method process are as follows: the wastewater in the first stage can enter the second stage for treatment when reaching the standard, and the materials in the first stage can be used as functional materials in the second stage after being treated again after reaching the standard, so that optimization explanation is carried out, and the dual purposes of full utilization of the materials and deep degradation of pollutants are considered.
The technical scheme of the invention is as follows:
the invention provides a method for deeply degrading organic pollutants in water by fully utilizing bismuth silver oxide, which comprises the following steps: (the method is a batch-type treatment method)
Pretreatment: removing impurities from the organic polluted wastewater through a grid (if the wastewater contains heavy metal pollutants, heavy metal ions in the wastewater need to be removed), standing for precipitation, and adjusting the pH value to be 6-11; if the TOC concentration of the organic polluted wastewater exceeds 50mg/L, the polluted wastewater needs to be diluted by pure water, so that the TOC concentration of the diluted wastewater is reduced to below 50 mg/L; dividing the pretreated organic polluted wastewater into a plurality of batches for treatment in batches;
(II) first stage (oxidative degradation treatment):
dividing the pretreated organic polluted wastewater into a plurality of batches, and carrying out first-stage oxidative degradation treatment in batches;
(1) treating the pretreated first batch of organic polluted wastewater: in the pretreated first batch of organic polluted wastewater, firstly adding 6-10 g/L of sodium bismuthate powder, then adding 50-200% of silver nitrate powder by weight of the sodium bismuthate, wherein the sodium bismuthate powder can be quickly changed from light yellow to black under the stirring effect, and continuously and fully stirring and mixing the black powder (bismuth silver oxide obtained by the reaction of the sodium bismuthate and the silver nitrate) with the wastewater to ensure that the bismuth silver oxide and organic pollutants in the wastewater are subjected to oxidative degradation reaction; after the oxidation degradation reaction is carried out for a certain time t, the concentration of the pollutants in the wastewater is detected, and the reduction rate of the concentration of the pollutants (namely the removal rate of the pollutants and the degradation rate of the pollutants) is calculated;
after the oxidation degradation reaction is carried out for a certain time t (15-35 minutes), the reduction rate of the pollutant concentration reaches more than 85 percent, namely the pollutant concentration in the wastewater is reduced to be less than 15 percent of the initial concentration, after the wastewater (the effluent after the oxidation degradation treatment of the batch) is separated from the bismuth silver oxide (solid-liquid separation), the effluent after the oxidation degradation treatment of the batch is collected and enters a second stage for photocatalytic degradation treatment, and the bismuth silver oxide is recycled and continuously used as the first-stage oxidation degradation treatment (used as an oxidant) of the wastewater of the next batch;
if the reduction rate of the pollutant concentration cannot reach more than 85 percent after the oxidation degradation reaction is carried out for a certain time t (15-35 minutes), further diluting the polluted wastewater appropriately, or increasing the adding amount of sodium bismuthate appropriately to ensure that the pollutant removal rate reaches more than 85 percent;
(2) treating the pretreated second batch of organic polluted wastewater: adding the collected and recovered bismuth-silver oxide into second batch of wastewater after the first-stage oxidative degradation treatment of the first batch of wastewater for the first-stage oxidative degradation treatment of the second batch of wastewater (the reaction conditions such as initial concentration of pollutants, degradation reaction time and the like of the second batch of wastewater are completely the same as those of the first batch); after the second batch of wastewater is subjected to oxidative degradation reaction for a certain time t (15-35 minutes), detecting the concentration reduction rate of pollutants in the wastewater;
if the pollutant concentration reduction rate still exceeds 85 percent after the oxidative degradation reaction is carried out for a certain time t (15-35 minutes), namely the pollutant concentration in the wastewater is reduced to be below 15 percent of the initial concentration, the bismuth silver oxide still has higher activity, can be used for the first-stage oxidative degradation treatment of the third batch of wastewater, and the effluent after the oxidative degradation treatment of the batch can also enter the second-stage photocatalytic degradation treatment after being collected;
(3) adding the collected and recovered bismuth-silver oxide into third batch of wastewater after the first-stage oxidative degradation treatment of the second batch of wastewater for the first-stage oxidative degradation treatment of the second batch of wastewater; by analogy, adding the collected and recovered bismuth silver oxide into the wastewater of the next batch for the first-stage oxidative degradation treatment of the wastewater of the next batch (the initial concentration and degradation reaction time of the pollutants of the wastewater of each next batch are completely the same as those of the wastewater of the first batch); with the continuous operation of the first-stage oxidative degradation treatment process of the next batch of wastewater and the next batch of wastewater, the oxidation activity of the bismuth silver oxide is continuously reduced until the first-stage oxidative degradation treatment of the Nth batch of wastewater is finished, the concentration reduction rate of pollutants in the wastewater is detected, and the concentration reduction rate of the pollutants is found to be less than 85% but more than 3% after the Nth batch of wastewater is subjected to oxidative degradation reaction for a certain time t (15-35 minutes); at the moment, the bismuth silver oxide still has certain oxidation activity and can be used for the first-stage oxidative degradation treatment of the (N + 1) th batch of wastewater, but after the first-stage oxidative degradation treatment of the Nth batch of wastewater is finished, effluent is collected and converged, sodium bismuthate and silver nitrate are required to be added again for the first-stage oxidative degradation treatment, and the effluent cannot directly enter the second-stage photocatalytic degradation treatment; in addition, effluent after the first-stage oxidative degradation treatment of the subsequent batches is finished from the Nth batch cannot directly enter the second-stage photocatalytic degradation treatment, the effluent is collected and collected together, and sodium bismuthate and silver nitrate are added again to carry out the first-stage oxidative degradation treatment again;
(4) continuously adding the collected and recovered bismuth-silver oxide into the wastewater of the next batch for the first-stage oxidative degradation treatment of the wastewater of the next batch (the initial concentration and degradation reaction time of pollutants in the wastewater of each batch of the next batch are completely the same as those in the wastewater of the first batch); detecting the concentration reduction rate of the pollutants in the wastewater until the M batch of wastewater is oxidized and degraded, and finding that the concentration reduction rate of the pollutants is less than 3% after the M batch of wastewater is oxidized and degraded for a certain time t (15-35 minutes); at this time, it is considered that the bismuth silver oxide has completely lost the oxidation activity, and can be used as a functional material for the second-stage photocatalytic degradation treatment, but cannot be used for the first-stage oxidative degradation treatment of the wastewater of the latter batch, i.e., the M +1 th batch. So far, the first-stage oxidative degradation treatment process dominated by the same bismuth silver oxide is completely finished. The next brand new complete first-stage oxidative degradation treatment process will be dominated by the brand new bismuth silver oxide.
(5) Collecting the effluent after the first-stage oxidative degradation treatment of the Nth batch of wastewater to the Mth batch of wastewater, uniformly gathering the effluent together, dividing the effluent into a plurality of batches, and carrying out the first-stage oxidative degradation treatment in batches according to the method; at this time, new sodium bismuthate and silver nitrate (a brand new bismuth silver oxide is needed) need to be added again, and the first-stage oxidative degradation treatment is carried out again.
(III) second stage (photocatalytic degradation treatment): washing the bismuth silver oxide (namely the residual bismuth silver oxide after the M batch of wastewater oxidation degradation reaction) which completely loses the oxidation activity in the first stage with water, and then washing with an organic solvent; then, as a photocatalyst, adding 0.5-0.8 g/L of the photocatalyst into effluent collected after the first-stage oxidative degradation treatment (the effluent quality is characterized in that the concentration of pollutants after the first-stage oxidative degradation treatment is reduced to below 15% of the initial concentration), stirring under illumination (visible light, sunlight and ultraviolet light), carrying out photocatalytic degradation reaction, and discharging the effluent after the concentration of pollutants or TOC in the wastewater in the second-stage reaction is further reduced to an expected target (the invention does not make an explanation on the end mark or the reaction time of the reaction in the stage, and the end mark or the reaction time of the reaction in the stage is completely determined according to the expected target); the photocatalyst of the second stage can be reused.
The flow of the two-stage organic wastewater treatment method (including the first stage and the second stage) in the invention is shown in fig. 1.
Furthermore, in the pretreatment process, heavy metal ions in the organic polluted wastewater containing heavy metal pollutants need to be removed. The method of the invention can only aim at organic polluted wastewater. The reason why the heavy metal ions in the wastewater are removed first is that when the bismuth silver oxide is used for oxidizing pollutants, if other heavy metals exist, the bismuth silver oxide can affect the structural change of the bismuth silver oxide, namely, the material generated after the bismuth silver oxide is inactivated is uncertain about the existence or the photocatalytic activity.
Further, in the second stage, the deactivated bismuth silver oxide is washed by water, and the water used is deionized water.
Further, in the second stage, the deactivated bismuth silver oxide is washed with an organic solvent, and the organic solvent used is ethanol and n-hexane.
Further, after the bismuth silver oxide inactivated in the first stage is washed twice by deionized water, the bismuth silver oxide is washed once by ethanol and n-hexane respectively; then, as a photocatalyst, photocatalytic degradation treatment is performed.
In the present invention, the first stage oxidative degradation treatment process is the important step of the present invention, and some important descriptions about the first stage are as follows:
under the general condition, when the initial TOC concentration of the organic polluted wastewater is less than 50mg/L, the adding amount of sodium bismuthate is 6-10 g/L, and the adding amount of silver nitrate is 0.5-2 times of the adding amount of sodium bismuthate, the bismuth silver oxide which is completely synthesized by the sodium bismuthate and the silver nitrate can complete high-efficiency oxidative degradation of the polluted wastewater within a certain reaction time t (15-35 minutes) (the degradation rate is more than or equal to 85%). If the pollutant removal rate cannot reach more than 85% within the preset time range, the polluted wastewater is further diluted appropriately, or the addition amount of the sodium bismuthate is increased appropriately. It is ensured that during the first degradation reaction in the first stage the concentration of contaminants drops by more than 85% within the reaction time t. When the method is used for degrading the wastewater in the first reaction in the first stage, the degradation reaction time t value for reducing the concentration of the pollutants to more than 85 percent (namely reducing the initial concentration from 100 percent to below 15 percent) is different according to the concentration and the type of the pollutants in the specific polluted wastewater. After the first-stage wastewater oxidative degradation reaction is finished, the bismuth silver oxide is collected and recycled to be continuously used as the first-stage oxidative degradation treatment (used as an oxidant) of the next batch of wastewater, and the treated wastewater (effluent) can enter the second stage for photocatalytic degradation treatment after being collected and gathered.
The reaction conditions of the first stage oxidative degradation treatment of the second batch of wastewater are identical to those of the first batch. After a reaction time t (determined from the first reaction), the degradation rate of the contaminant is measured. If the reduction rate of the pollutant concentration still exceeds 85 percent, namely the pollutant concentration is less than 15 percent of the initial concentration after the reaction time t, the bismuth silver oxide still has higher activity and can be used for the first-stage oxidative degradation treatment of the third batch, and the effluent after the first-stage oxidative degradation treatment of the batch is collected and gathered can also enter the second stage for photocatalytic degradation treatment.
As the bismuth silver oxide is recycled for the next batch and the first-stage oxidative degradation reaction of the next batch of wastewater is continuously carried out, the oxidation activity of the bismuth silver oxide is continuously reduced until the pollutant concentration reduction rate is less than 85% but more than 3% after the nth batch of cyclic reaction is finished and the reaction time t is up, at this time, the bismuth silver oxide is considered to still maintain a certain oxidation activity and can be used for the (N + 1) th batch of reaction, but after the nth batch of first-stage cyclic reaction is finished and the treated effluent is collected, the first-stage oxidative degradation treatment needs to be carried out again, and the treated effluent cannot directly enter the second-stage photocatalytic degradation treatment. And collecting and summarizing effluent after the first-stage cycle reaction of the subsequent batches from the Nth batch, adding sodium bismuthate and silver nitrate again, and performing the first-stage oxidative degradation treatment again.
Continuing the first-stage reaction, after the Mth batch of cyclic reaction is finished, the pollutant concentration reduction rate is less than 3% after the reaction time t, and at this time, the bismuth silver oxide is considered to completely lose the oxidation activity, and can be used for the functional material of the second-stage photocatalytic degradation treatment, but can not be used for the Mth +1 batch of reaction of the first stage. The first stage reaction, which is dominated by the same bismuth silver oxide, is now completely completed. The next completely new first stage reaction will be dominated by the completely new bismuth silver oxide. Collecting and uniformly collecting treated effluent after the first-stage cyclic reaction of the Nth to Mth batches is finished, adding sodium bismuthate and silver nitrate again (brand new bismuth silver oxide needs to be generated), and performing the first-stage oxidative degradation treatment again. The above process points are summarized as follows:
it is necessary to ensure that the pollutant concentration after the first batch oxidative degradation reaction in the first stage is over 85% and the oxidative degradation reaction time to reach the degradation rate is t.
The mark that the wastewater (effluent) after the first stage oxidative degradation treatment can enter the second stage for photocatalytic degradation treatment is: after the first stage oxidative degradation treatment, the contaminant concentration has dropped below 15% of the initial concentration.
In the first stage, the cyclic reaction (continuously utilizing the residual oxidizing capability of the bismuth silver oxide) of each batch needs to be kept unchanged, including the type and initial concentration of the organic polluted wastewater, the adding amount of the bismuth silver oxide (generated after the sodium bismuthate is added in the first batch and reacts with the silver nitrate), and the degradation reaction time t of each batch.
After the oxidation degradation reaction of the 1 st to the N-1 st batches of wastewater in the first stage is finished, the effluent of the wastewater in the first stage directly enters the second stage for photocatalytic degradation, and the recovered bismuth silver oxide after the reaction is finished is continuously used for the oxidation degradation reaction (cyclic reaction) of the next batch of wastewater in the first stage.
After the Nth to M-1 th batch reactions in the first stage are finished, the effluent direction of the wastewater in the first stage is changed (the effluent in the first stage directly enters the second stage, and the effluent in the first stage is collected and gathered and then the reaction in the first stage is carried out again); the destination of the bismuth silver oxide after the reaction is finished is not changed (the bismuth silver oxide can be recycled and continuously used as the oxidative degradation reaction of the next batch of wastewater in the first stage, namely the cyclic reaction).
The oxidative degradation reaction of the M-th batch of wastewater in the first stage is finished, the effluent of the wastewater in the first stage is unchanged (the effluent in the first stage needs to be collected and then the first-stage reaction is carried out again), and the material direction is changed (the bismuth silver oxide is changed into a photocatalyst which is used for the photocatalytic degradation reaction in the second stage after being simply treated and reused as an oxidant for the oxidative degradation reaction of the next batch of wastewater in the first stage).
The invention has the beneficial effects that:
1. sodium bismuthate is a chemical substance with high oxidation activity, but the sodium bismuthate cannot be subjected to oxidative degradation reaction with organic pollutants directly. In the invention, the silver bismuth oxide is synthesized by silver nitrate and sodium bismuthate in the first stage, so that the high oxidation activity of the sodium bismuthate can be effectively utilized, and organic pollutants can be oxidized and degraded. The first stage of the oxidation degradation reaction is very efficient, can quickly degrade pollutants, and is very suitable for the purpose of primarily degrading the pollutants in the first stage.
2. Bismuth silver oxide, as it continues to oxidatively degrade contaminants (release singlet oxygen) in the first stage, changes its own structure until it is completely deactivated, itself becoming silver-containing bismuth subcarbonate. The invention discovers that after the bismuth silver oxide with the oxidation performance fully utilized is changed into silver-containing bismuth subcarbonate, the silver-containing bismuth subcarbonate is washed by water and an organic solvent, the material has high photocatalytic activity (can be used as a visible light photocatalyst, generates superoxide radical and photogenerated cavity under the irradiation of sunlight, visible light or ultraviolet light, and generates deep degradation reaction with organic pollutants in wastewater), and can be just used as a photocatalyst in the second stage.
3. In the first stage, the bismuth silver oxide degrades pollutants mainly by singlet oxygen, the oxidation-reduction potential of the singlet oxygen is not high enough, and the bismuth silver oxide has selective attack characteristics (mainly electrophilic attack) and cannot effectively and comprehensively carry out advanced treatment (mineralization) on the pollutants. In the second stage, bismuth silver oxide with oxidation performance fully utilized becomes bismuth subcarbonate containing silver, and can generate superoxide radical and photogenerated cavity under illumination, wherein the redox potential of the photogenerated cavity is higher than that of singlet oxygen, and the attack characteristic of the superoxide radical is completely different from that of singlet oxygen (the superoxide radical is nucleophilic attack, and the singlet oxygen is electrophilic attack). The synergistic effect between the photogenerated hole and the superoxide radical is utilized, the second-stage reaction is added after the first-stage reaction is finished, and the main purpose is to carry out secondary degradation, namely deep degradation and even complete mineralization on pollutants after the first-stage reaction. The two-stage organic wastewater treatment method can rapidly degrade pollutants in the first stage by using singlet oxygen with high degradation activity and low mineralization capability, and secondarily treat the pollutants in the second stage by using photocatalytic free radicals with strong deep degradation and mineralization capabilities, so that the aim of thoroughly removing the organic pollutants in a short time is fulfilled.
4. The invention further develops the brand new photocatalysis performance of the bismuth silver oxide on the basis of the patent ZL 200910029442.8. The two-stage organic wastewater treatment method provided by the invention realizes the full life cycle utilization of the sodium bismuthate material, so that bismuth silver oxides with different life cycles can play corresponding functions in different wastewater treatment stages, and the two-stage degradation method based on material characteristic change can be combined to carry out deep degradation on pollutants. Therefore, compared with the patent ZL 201310204545.X, the invention has similar effect on wastewater treatment, but the cost is further reduced because the material for the second stage completely comes out of the material for the first stage for inactivation.
5. In order to ensure the full utilization of the bismuth silver oxide in the first stage and the maximization of the function of the bismuth silver oxide in the second stage after the first stage is utilized, the invention provides a use judgment method for the bismuth silver oxide material in the first stage as a functional material in the second stage through retreatment in the whole set of method processes, and provides a method for evaluating the application conversion of the bismuth silver oxide material by judging the wastewater treatment effect (the pollutant concentration reduction rate is less than 3%) in the first stage, thereby saving the step of material characterization. In addition, the invention provides a water outlet judgment method in which the wastewater at the first stage (the pollutant removal rate is more than 85%) can enter the second stage for treatment in the whole set of method process, so that the reasonable utilization of the oxidation pretreatment at the first stage and the photocatalytic advanced treatment at the second stage in the two-stage treatment method can be ensured, and the effect of optimal overall pollution treatment effect can be achieved. (the Nth cycle reaction and the Mth cycle reaction in the first stage are taken as two turning points which respectively correspond to the change of the effluent direction of the wastewater in the first stage and the change of the application of the bismuth-silver oxide material in the first stage.)
Compared with the prior art, the invention has the beneficial effects that:
1. the method has strong applicability to organic polluted wastewater, can be carried out at normal temperature, can efficiently and deeply degrade most organic pollutants by integrating two materials based on bismuth-silver oxide and a corresponding two-stage combined degradation method, has no secondary pollution, and realizes advantage complementation.
2. The material after the first-stage oxidation inactivation is a brand-new catalytic material for the second stage after being simply washed by water and an organic solvent, and the material is simple and easy to combine and use in the two processes.
3. The method of the invention does not need auxiliary energy such as microwave, ultrasonic and the like in the whole process, and only needs to stir the solution in the first stage. In the second stage, the deep degradation can be performed by sunlight, and compared with an artificial light source, the deep degradation consumes electric energy and is further optimized by utilizing sunlight cost. In order to control the working time and enhance the efficiency, the light source can also be used for illuminating.
4. The raw materials required by the two combined treatment processes are bismuth silver oxide, and the bismuth silver oxide has the advantages of simple preparation, low price and easy large-scale production and use. In combination with the two-stage water treatment process, the bismuth silver oxide can exert its greatest value both before and after conversion into the catalyst.
5. The whole system has low running cost and simple operation.
Drawings
FIG. 1 is a schematic flow chart of a two-stage organic wastewater treatment method (including a first stage and a second stage) according to the present invention.
Detailed Description
The present invention is further illustrated by the following specific examples.
Example 1:
preparing 30mg/L azure aqueous solution (polluted solution and waste water) simulation dye waste water (the solution does not need to be purified, and the pH value is within the range of 6-11). 5g of sodium bismuthate powder is added into 500mL of simulated dye wastewater, then 2.5g of silver nitrate powder is rapidly added, and after the mixture is oxidized and degraded under the action of stirring for 17min, the azure concentration is reduced by 91%. After solid-liquid separation, the solid bismuth silver oxide is recovered for standby, and the liquid (wastewater effluent) after reaction is collected (the first stage wastewater treatment stage task is completed and the preparation is carried out in the second stage photocatalytic degradation treatment).
And continuously degrading the recovered bismuth silver oxide with 500mL of 30mg/L azure aqueous solution of the next new batch, performing oxidative degradation reaction for 17min under the stirring effect, and then performing solid-liquid separation. And recovering the solid bismuth silver oxide for later use, collecting the liquid after reaction, and preparing to enter a second-stage photocatalytic degradation treatment.
The above processes are continuously repeated (circular reaction), that is, the bismuth silver oxide collected and recovered after the first-stage oxidative degradation treatment of the previous batch of wastewater is continuously added into the next batch of wastewater for the first-stage oxidative degradation treatment of the next batch of wastewater; the initial concentration of pollutants and the degradation reaction time of each subsequent batch of wastewater are completely the same as those of the first batch.
After the 7 th circulation reaction, namely the oxidation degradation reaction of the 7 th batch of wastewater for 17min, the azure concentration in the wastewater is reduced by 84% (the reduction rate of the pollutant concentration in the wastewater is less than 85% but more than 3%, namely the bismuth silver oxide is still active and can be used for the first-stage oxidation degradation treatment of the next batch of wastewater, namely the 8 th batch of wastewater, but the first-stage treatment task of the batch of wastewater is not completed and cannot enter the second-stage photocatalytic degradation treatment); effluent after the first-stage oxidative degradation treatment of the 7 th batch and subsequent batches cannot directly enter the second-stage photocatalytic degradation treatment, the effluent is collected and collected together, and sodium bismuthate and silver nitrate are added again to perform the first-stage oxidative degradation treatment again.
After the 27 th circulation reaction, namely the 27 th batch of wastewater is subjected to oxidative degradation reaction for 17min, the azure concentration in the wastewater is stabilized at 98% of the initial concentration (the reduction rate of the pollutant concentration in the wastewater is less than 3%, namely the bismuth silver oxide completely loses the oxidation activity, so that the bismuth silver oxide can be used as a functional material for the second-stage photocatalytic degradation treatment, and cannot be used for the first-stage oxidative degradation treatment of the subsequent batch, namely the 28 th batch of wastewater).
The 7 th cycle reaction and the 27 th cycle reaction in the first stage are taken as two turning points which respectively correspond to the change of the effluent direction of the wastewater in the first stage and the change of the application of the bismuth-silver oxide material in the first stage.
And uniformly collecting and collecting the solutions after the 7 th to 27 th batches of reactions, adding sodium bismuthate and silver nitrate again (generating a brand new bismuth silver oxide), and performing the first-stage oxidative degradation treatment again.
And uniformly collecting the solutions after the first 6 batches of reactions to perform the next (second stage) photocatalytic degradation reaction.
In the first stage, after 27 times of reaction, the solid bismuth silver oxide is subjected to solid-liquid separation, washed twice by deionized water and then washed once by ethanol and n-hexane respectively; then, the uniformly collected effluent water of the first stage is added according to the adding amount of 0.5g/L, the mixture is stirred under the irradiation of sunlight to generate a photocatalytic degradation reaction, and after 2 hours, the TOC of the effluent water of the second stage is reduced by 38 percent compared with that of the effluent water of the first stage. Compared with the initially prepared polluted solution, after two-stage treatment, the azure concentration in the wastewater is reduced by 100%, and the TOC is reduced by 53%.
Example 2:
preparing a 20mg/L tetrachlorophenol aqueous solution (polluted solution and waste water) simulated dye waste water (the solution does not need to be purified, and the pH value is within the range of 6-11). Adding 4g of sodium bismuthate powder into 500mL of simulated dye wastewater, then quickly adding 4g of silver nitrate powder, and carrying out oxidative degradation reaction for 30min under the action of stirring, wherein the concentration of tetrachlorophenol is reduced by 81%. After solid-liquid separation, the solid bismuth silver oxide is recovered for standby, and the liquid (wastewater effluent) after reaction is collected (the stage task of wastewater treatment in the first stage is completed and the photocatalytic degradation treatment in the second stage is prepared).
And continuously using the recovered bismuth silver oxide for the next new 500mL of tetrachlorophenol aqueous solution with the concentration of 20mg/L for degradation, carrying out oxidative degradation reaction for 30min, and then carrying out solid-liquid separation. And (3) recovering the solid bismuth silver oxide for later use, collecting the liquid after reaction, and preparing to enter a second-stage photocatalytic degradation treatment.
The above processes are continuously repeated (circular reaction), that is, the bismuth silver oxide collected and recovered after the first-stage oxidative degradation treatment of the previous batch of wastewater is continuously added into the next batch of wastewater for the first-stage oxidative degradation treatment of the next batch of wastewater; the initial concentration of pollutants and the degradation reaction time of each subsequent batch of wastewater are completely the same as those of the first batch.
After the 4 th circulation reaction, namely the 4 th batch of wastewater is subjected to oxidative degradation reaction for 30min, the azure concentration in the wastewater is reduced by 83% (the reduction rate of the pollutant concentration in the wastewater is less than 85% but more than 3%, namely the bismuth silver oxide is still active and can be used for the first-stage oxidative degradation treatment of the next batch of wastewater, namely the 8 th batch of wastewater, but the first-stage treatment task of the batch of wastewater is not completed and cannot enter the second-stage photocatalytic degradation treatment); effluent after the first-stage oxidative degradation treatment of the 4 th batch and subsequent batches cannot directly enter the second-stage photocatalytic degradation treatment, the effluent is collected and collected together, and the sodium bismuthate and the silver nitrate are added again to perform the first-stage oxidative degradation treatment again.
After the 21 st cycle reaction, namely the 21 st batch of wastewater is subjected to the oxidative degradation reaction for 30min, the azure concentration in the wastewater is stabilized at 99% of the initial concentration (the reduction rate of the concentration of pollutants in the wastewater is less than 3%, namely the bismuth silver oxide completely loses the oxidation activity, and the bismuth silver oxide can be used as a functional material for the second-stage photocatalytic degradation treatment and cannot be used for the first-stage oxidative degradation treatment of the next batch of wastewater, namely the 22 nd batch of wastewater).
The 4 th cycle reaction and the 21 st cycle reaction in the first stage are taken as two turning points which respectively correspond to the change of the effluent direction of the wastewater in the first stage and the change of the application of the bismuth-silver oxide material in the first stage.
Uniformly collecting the solutions after the first-stage oxidative degradation treatment of the 4 th to 21 st batches, and performing the first-stage oxidative degradation treatment again.
The solutions after the first-stage oxidative degradation treatment of the first 3 batches are uniformly collected to be subjected to the next (second stage) photocatalytic degradation treatment.
In the first stage, after the 21 st oxidation degradation reaction, the solid bismuth silver oxide is subjected to solid-liquid separation, washed twice by deionized water and then washed once by ethanol and n-hexane respectively; then, the uniformly collected effluent water of the first stage is added according to the adding amount of 0.7g/L, the mixture is stirred under the irradiation of ultraviolet light to generate a photocatalytic degradation reaction, and after 6.5 hours, the TOC of the effluent water of the second stage is reduced by 46 percent compared with that of the effluent water of the first stage. Compared with the initially prepared polluted solution, after two-stage treatment, the concentration of tetrachlorophenol in the wastewater is reduced by 100%, and TOC is reduced by 59%.
Example 3:
preparing 35mg/L atrazine water solution (polluted solution and waste water) simulation dye waste water (the solution does not need to be purified, and the pH value is within the range of 6-11). Adding 3g of sodium bismuthate powder into 500mL of simulated dye wastewater, then quickly adding 6g of silver nitrate powder, and carrying out oxidation degradation reaction for 35min under the action of stirring, wherein the concentration of atrazine is reduced by 96%. After solid-liquid separation, the solid bismuth silver oxide is recovered for standby, and the liquid (wastewater effluent) after reaction is collected (the first stage wastewater treatment stage task is completed and the preparation is carried out in the second stage photocatalytic degradation treatment).
And continuously degrading the recovered bismuth silver oxide with a new next 500mL of tetrachlorophenol aqueous solution with the concentration of 35mg/L, carrying out oxidative degradation reaction for 35min under the stirring action, and then carrying out solid-liquid separation. And (3) recovering the solid bismuth silver oxide for later use, collecting the liquid after reaction, and preparing to enter a second-stage photocatalytic degradation treatment.
The above processes are continuously repeated (circular reaction), that is, the bismuth silver oxide collected and recovered after the first-stage oxidative degradation treatment of the previous batch of wastewater is continuously added into the next batch of wastewater for the first-stage oxidative degradation treatment of the next batch of wastewater; the initial concentration of pollutants and the degradation reaction time of each subsequent batch of wastewater are completely the same as those of the first batch.
After the 5 th circulation reaction, namely the 5 th batch of wastewater is subjected to oxidation degradation reaction for 35min, the azure concentration is reduced by 83% (the pollutant concentration reduction rate in the wastewater is less than 85% but more than 3%, namely the bismuth silver oxide is still active and can be used for the first-stage oxidation degradation treatment of the next batch of wastewater, namely the 6 th batch of wastewater, but the first-stage treatment stage task of the batch of wastewater is not completed and cannot enter the second-stage photocatalytic degradation treatment); effluent after the first-stage oxidative degradation treatment of the 5 th batch and subsequent batches cannot directly enter the second-stage photocatalytic degradation treatment, the effluent is collected and collected together, and the sodium bismuthate and the silver nitrate are added again to perform the first-stage oxidative degradation treatment again.
After the 17 th circulation reaction, namely the 17 th batch of wastewater is subjected to oxidation degradation reaction for 35min, the azure concentration in the wastewater is stabilized at 97% of the initial concentration (the reduction rate of the pollutant concentration in the wastewater is less than 3%, namely the bismuth silver oxide completely loses oxidation activity, can be used as a functional material for the second-stage photocatalytic degradation treatment, and cannot be used for the first-stage oxidation degradation treatment of the next batch of wastewater, namely the 18 th batch of wastewater).
The 5 th cycle reaction and the 17 th cycle reaction in the first stage are taken as two turning points which respectively correspond to the effluent direction change of the wastewater in the first stage and the application change of the bismuth-silver oxide material in the first stage.
And uniformly collecting the solutions after the 5 th to 17 th batches of reactions, and carrying out the first-stage reaction again. And uniformly collecting the solutions after the first 4 batches of reactions to perform the next (second stage) degradation reaction.
In the first stage, after the 17 th reaction, the solid bismuth silver oxide is subjected to solid-liquid separation, washed twice by deionized water and then washed once by ethanol and n-hexane respectively; then, adding the uniformly collected effluent water of the first stage according to the adding amount of 0.8g/L, stirring under the irradiation of artificial visible light to perform a photocatalytic degradation reaction, and after 4 hours, reducing the concentration of the pollutant atrazine by 61 percent compared with the TOC of the effluent water of the first stage. Compared with the initially prepared polluted solution, after two-stage treatment, the concentration of atrazine in the wastewater is reduced by 100%, and TOC is reduced by 72%.
Claims (8)
1. A method for deeply degrading organic pollutants in water by fully utilizing bismuth silver oxide is characterized by comprising the following steps:
pretreatment: removing impurities from the organic polluted wastewater through a grating, standing for precipitation, and adjusting the pH value to 6-11;
(II) first-stage oxidative degradation treatment:
dividing the pretreated organic polluted wastewater into a plurality of batches, and carrying out first-stage oxidative degradation treatment in batches;
(1) treating the pretreated first batch of organic polluted wastewater: firstly adding 6-10 g/L of sodium bismuthate powder into pretreated first-batch organic polluted wastewater, then adding 50-200% by weight of sodium bismuthate powder into the pretreated first-batch organic polluted wastewater, wherein the sodium bismuthate powder can be quickly changed from light yellow to black under the action of stirring, and the black powder, namely bismuth silver oxide which is a product obtained by reacting sodium bismuthate and silver nitrate, is continuously and fully stirred and mixed with the wastewater to enable the bismuth silver oxide and organic pollutants in the wastewater to carry out oxidative degradation reaction; after the oxidation degradation reaction is carried out for a certain time t, the concentration of the pollutants in the wastewater is detected, and the reduction rate of the concentration of the pollutants, namely the removal rate of the pollutants, is calculated;
if the pollutant concentration reduction rate reaches more than 85 percent after the oxidation degradation reaction is carried out for a certain time t, namely the pollutant concentration in the wastewater is reduced to be less than 15 percent of the initial concentration, the wastewater and the bismuth silver oxide are subjected to solid-liquid separation, the effluent after the first time of oxidation degradation treatment is collected and enters a second stage for photocatalytic degradation treatment, and the bismuth silver oxide is recycled and continuously used for the first stage oxidation degradation treatment of the next time of wastewater;
if the reduction rate of the pollutant concentration cannot reach more than 85% after the oxidation degradation reaction is carried out for a certain time t, properly diluting the polluted wastewater, or properly increasing the adding amount of sodium bismuthate to ensure that the removal rate of the pollutants reaches more than 85%;
(2) treating the pretreated second batch of organic polluted wastewater: adding the collected and recovered bismuth-silver oxide into second batch of wastewater after the first-stage oxidative degradation treatment of the first batch of wastewater for the first-stage oxidative degradation treatment of the second batch of wastewater; after the second batch of wastewater is subjected to oxidative degradation reaction for a certain time t, detecting the concentration reduction rate of pollutants in the wastewater;
if the pollutant concentration reduction rate still exceeds 85 percent after the oxidation degradation reaction is carried out for a certain time t, namely the pollutant concentration in the wastewater is reduced to be below 15 percent of the initial concentration, the bismuth silver oxide still has higher activity, can be used for the first-stage oxidation degradation treatment of the third batch of wastewater, and the effluent after the oxidation degradation treatment of the batch can also enter the second-stage photocatalytic degradation treatment after being collected;
(3) adding the collected and recovered bismuth silver oxide into a third batch of wastewater after the first-stage oxidative degradation treatment of the second batch of wastewater for the first-stage oxidative degradation treatment of the second batch of wastewater; by analogy, adding the recovered bismuth silver oxide collected after the first-stage oxidative degradation treatment of the wastewater of the previous batch into the wastewater of the next batch for the first-stage oxidative degradation treatment of the wastewater of the next batch; along with the continuous process of the first-stage oxidative degradation treatment of the next batch of wastewater and the next batch of wastewater, the oxidation activity of the bismuth silver oxide is continuously reduced until the first-stage oxidative degradation treatment of the Nth batch of wastewater is finished, the concentration reduction rate of pollutants in the wastewater is detected, and the concentration reduction rate of the pollutants is less than 85% but more than 3% after the Nth batch of wastewater is subjected to the oxidative degradation reaction for a certain time t; at the moment, the bismuth silver oxide still has certain oxidation activity and can be used for the first-stage oxidative degradation treatment of the (N + 1) th batch of wastewater, but effluent after the first-stage oxidative degradation treatment of the Nth batch of wastewater and each subsequent batch of wastewater is collected and needs to be temporarily stored, and the effluent cannot directly enter the second-stage photocatalytic degradation treatment;
(4) continuously adding the collected and recovered bismuth-silver oxide into the wastewater of the next batch for the first-stage oxidative degradation treatment of the wastewater of the next batch; detecting the concentration reduction rate of the pollutants in the wastewater until the oxidation degradation reaction of the M batch of wastewater is finished, and finding that the concentration reduction rate of the pollutants is less than 3% after the oxidation degradation reaction of the M batch of wastewater is carried out for a certain time t; at the moment, the bismuth silver oxide is considered to completely lose the oxidation activity, can be used as a functional material for the second-stage photocatalytic degradation treatment, and can not be used for the first-stage oxidative degradation treatment of the next batch, namely the M +1 th batch of wastewater; so far, the first-stage oxidative degradation treatment process dominated by the same bismuth silver oxide is completely finished;
(III) the second-stage photocatalytic degradation treatment: washing the bismuth silver oxide which completely loses oxidation activity after the M batch of wastewater in the first stage is subjected to oxidative degradation, and then washing with an organic solvent; then, adding the photocatalyst serving as a photocatalyst into effluent collected after the first-stage oxidative degradation treatment is finished according to the adding amount of 0.5-0.8 g/L, stirring under illumination to perform photocatalytic degradation reaction, and discharging after the pollutant concentration or TOC of the wastewater in the second-stage reaction further drops to an expected target;
the certain time t of the oxidative degradation reaction is 15-35 minutes; in the step (2) of the second step (II), the initial concentration and the degradation reaction time of the pollutants in the second batch of wastewater are completely the same as those in the first batch; in the step (3) and the step (4) of the step (II), the initial concentration of the pollutants and the degradation reaction time of each subsequent batch of wastewater are completely the same as those of the first batch;
collecting the effluent after the oxidation degradation treatment of the wastewater from the Nth batch to the Mth batch in the first stage, uniformly gathering the effluent together, dividing the effluent into a plurality of batches, and carrying out the oxidation degradation treatment of the first stage in batches according to the method; at the moment, new sodium bismuthate and silver nitrate are required to be added again to generate a brand new bismuth silver oxide, and the first-stage oxidative degradation treatment is carried out again.
2. The method for deeply degrading organic pollutants in water by fully utilizing bismuth silver oxide as claimed in claim 1, wherein in the pretreatment process, heavy metal ions in the organic polluted wastewater containing heavy metal pollutants need to be removed.
3. The method for deeply degrading organic pollutants in water by fully utilizing bismuth silver oxide as claimed in claim 1, wherein in the pretreatment process, if the TOC concentration of organic polluted wastewater exceeds 50mg/L, the polluted wastewater needs to be diluted by pure water, so that the TOC concentration of the diluted wastewater is reduced to be below 50 mg/L.
4. The method for deeply degrading organic pollutants in water by fully utilizing bismuth silver oxide as claimed in claim 1, wherein in the second stage, the deactivated bismuth silver oxide is washed by using deionized water.
5. The method for deeply degrading organic pollutants in water by fully utilizing bismuth silver oxide as claimed in claim 1, wherein in the second stage, the deactivated bismuth silver oxide is washed by using an organic solvent, and the used organic solvent is ethanol and n-hexane.
6. The method for deeply degrading organic pollutants in water by fully utilizing bismuth silver oxide as claimed in claim 1, wherein in the second stage, the bismuth silver oxide deactivated in the first stage is washed twice by deionized water and then washed once by ethanol and n-hexane respectively; then, as a photocatalyst, photocatalytic degradation treatment is performed.
7. The method for deeply degrading organic pollutants in water by fully utilizing bismuth silver oxide as claimed in claim 1, wherein in the second stage, the illumination is visible light, sunlight or ultraviolet light.
8. The method for deeply degrading organic pollutants in water by fully utilizing bismuth silver oxide as claimed in claim 1, wherein the photocatalyst in the second stage can be reused.
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