CN113072159A - Circulating dechlorination process and system - Google Patents

Circulating dechlorination process and system Download PDF

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CN113072159A
CN113072159A CN202110437963.8A CN202110437963A CN113072159A CN 113072159 A CN113072159 A CN 113072159A CN 202110437963 A CN202110437963 A CN 202110437963A CN 113072159 A CN113072159 A CN 113072159A
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dechlorination
product
reaction
unit
chlorine
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仇洪波
杨凤岭
吕扬
吕杨杨
吕和兴
孙德山
于友水
乔正泽
付迪
杨正大
宋甲亮
尹鹏
李智阳
管闯
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Shandong Guoshun Environmental Protection Equipment Co ltd
Shandong Guoshun Construction Group Co Ltd
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Shandong Guoshun Environmental Protection Equipment Co ltd
Shandong Guoshun Construction Group Co Ltd
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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
    • C02F1/58—Treatment of water, waste water, or sewage by removing specified dissolved compounds
    • 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
    • C02F1/38—Treatment of water, waste water, or sewage by centrifugal separation
    • 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
    • C02F2101/12—Halogens or halogen-containing compounds

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Abstract

The application provides a cyclic dechlorination process which is characterized in that the process adopts Bi2(H2O)2(SO4)2(OH)2Or with Bi2(H2O)2(SO4)2(OH)2The dechlorinating agent which is an active ingredient is dechlorinated, and the dechlorinating product after dechlorination is regenerated to obtain a regenerated product, so that the regenerated product is continuously used for preparing the dechlorinating agent to participate in dechlorination, or the regenerated product is continuously used for participating in dechlorination, and the circulation is carried out. The process has good dechlorination effect, the first dechlorination effect can reach 99 percent, the cyclic dechlorination can be realized, and the dechlorination efficiency is still maintained at 80 percent after the cyclic multiple use.

Description

Circulating dechlorination process and system
Technical Field
The application relates to the technical field of wastewater treatment, in particular to a cyclic dechlorination process and a cyclic dechlorination system.
Background
The information in this background section is disclosed only to enhance understanding of the general background of the application and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art that is already known to a person of ordinary skill in the art.
The high content of chloride ions in the wastewater not only can corrode equipment, but also can generate toxic action on human bodies, fishes, vegetation, buildings and the like. At present, the proportion of the high-chlorine wastewater is large and the sources are wide in the total amount of wastewater discharged every year in China. The treatment difficulty of chloride ions in the high-chlorine wastewater is high, the treatment cost is high, and great challenges are provided for wastewater treatment. The comprehensive wastewater discharge standards (GB 8978-. The design code of industrial circulating cooling water treatment (GB 50050-2017) also stipulates that the concentration of chloride ions in circulating cooling water in a water running process cannot exceed 1000 mg/L. In recent years, with the strictness of the implementation of wastewater discharge standards, the content of chloride ions has become an important index for whether the wastewater can reach the discharge standard after being treated, and the industrial attention is attracted.
The method for removing the chloride ions mainly comprises chemical precipitation, adsorption, ion exchange, filter membrane separation, electrochemical technology, evaporation concentration, supercritical water oxidation and the like. The supercritical water oxidation method has strict equipment requirements and can generate toxic gas chlorine; the waste water in the evaporation concentration method needs high concentration, the energy consumption is large, and the equipment is easy to corrode; electrochemical techniques have limited throughput and generate chlorine gas; the membrane separation is not suitable for treating high-concentration chloride ion wastewater, and the membrane component is easy to be polluted; the ion exchange method is not suitable for treating high-concentration chloride ion wastewater; the adsorption method has long reaction time, is easily influenced by temperature, competitive ions, chloride ion concentration and the like, and has large sludge yield; the chemical precipitation method is simple to operate, can treat high-concentration chloride ion wastewater and has large treatment capacity, but has the problems of low removal rate, large medicament dosage and sludge treatment. The chlorine removal method is the simplest chemical precipitation method in combination, wherein the related chlorine removal agent and the specific method mainly comprise layered double hydroxides such as Mg-Al, Zn-Al and the like, CaO, NaAlO and the like2The ultra-high lime-aluminum method, the silver compound dechlorination method, the cuprous dechlorination method and the like. The layered double hydroxide and the ultra-high lime-aluminum method are used for removing chlorine, the medicament consumption is large, the regeneration effect is poor, and the sludge yield is large; the silver compound can rapidly and efficiently remove chlorine, but the cost is too high (more than 100 ten thousand per ton); the cuprous ions are unstable, the cuprous dechlorination (more than 4 ten thousand per ton) needs gas protection or additional copper powder or zinc powder is added, and the medicament is consumedHigh consumption and large amount of heavy metal ions. Due to the problems of cost, stability, chlorine removal efficiency and the like, the chlorine removal agents are not widely applied to chlorine removal of chlorine-containing wastewater so far, so that the chlorine-containing wastewater is shelved in large quantity and cannot be treated, and the ecological environment is seriously threatened. Therefore, the development of a high chlorine-containing wastewater treatment technology with good chlorine removal effect and low cost is urgent for water pollution control in China and many related enterprises.
Compared with the chlorine removal agent, bismuth oxide is the most promising chlorine removal agent for large-scale application, because bismuth ions are relatively stable, and the formed bismuth oxychloride precipitate has good regeneration effect, but the bismuth oxide can obtain higher chlorine removal efficiency under the condition of excessive addition (at least 2 times). However, because the addition needs to be excessive and the cost of bismuth oxide is high, the existing bismuth oxide dechlorination method is not difficult to realize industrialization really.
Disclosure of Invention
In order to solve the defects of the prior art, the application provides a circulating dechlorination process and a circulating dechlorination system2(H2O)2(SO4)2(OH)2Or with Bi2(H2O)2(SO4)2(OH)2The dechlorination agent which is an active ingredient is used for dechlorinating the wastewater, and the dechlorination product is treated to realize circular dechlorination, so that the defects of poor dechlorination effect, large using amount, high price and difficulty in circular use of the conventional dechlorination agent are overcome, the dechlorination efficiency is improved, the circulation of the dechlorination process is realized, the cost is reduced, and the industrial application of the bismuth-containing dechlorination agent is realized.
Specifically, the present invention provides the following technical features, and one or a combination of the following technical features constitutes the technical solution of the present invention.
In a first aspect of the invention, the invention provides a cyclic dechlorination process, which employs Bi2(H2O)2(SO4)2(OH)2As dechlorinating agents or with Bi2(H2O)2(SO4)2(OH)2Is active componentThe divided chlorine removal agent is used for removing chlorine, and the chlorine removal product after chlorine removal is subjected to regeneration treatment to obtain a regeneration product, so that the regeneration product is used for continuously preparing the chlorine removal agent to participate in chlorine removal, or the regeneration product is used for participating in chlorine removal, and the circulation is carried out.
In an embodiment of the present invention, the Bi2(H2O)2(SO4)2(OH)2Has a smooth rod-like morphology. Rods vary in length and a small amount of aggregates are present. The length of the rod-shaped body ranges from 1.9 to 33.7 mu m, the length of the rod-shaped body is mainly concentrated in 5 to 20 mu m, and the average length is 10.6 mu m; the diameter of the rods ranged from 0.6 to 3.7 μm, centered primarily at 1 to 3 μm, with an average diameter of 1.9 μm.
In some embodiments of the invention, the chlorine scavenger may or may not contain water. In the embodiment of the present invention, the inventors have studied on the chlorine remover, and the chlorine removing effect of the chlorine remover containing a proper amount of water is better than that of the chlorine remover after the complete drying under the same chlorine removing condition. In some embodiments of the present invention, the chlorine scavenger has a water content of not less than 9%, and may further have a water content of 9 to 30%.
In some embodiments of the invention, the dechlorinating agent having a water content of 10% is Bi3+：Cl-When the chlorine removal is carried out by the feeding amount of 1:1, the chlorine removal efficiency in 10 minutes can be close to 90 percent, and the chlorine removal efficiency in 60 minutes can be close to 99 percent; under the condition of the same feeding, the dechlorination efficiency of the anhydrous dechlorination agent in 10 minutes is about 88 percent, the dechlorination efficiency in 60 minutes is close to 95 percent, and although the dechlorination agent is not as good as the anhydrous dechlorination agent, the dechlorination agent has good dechlorination effect when the dechlorination agent does not contain water.
In some embodiments of the present invention, other water-purifying substances may be added to the chlorine removal agent as long as the substances do not affect the active ingredient Bi2(H2O)2(SO4)2(OH)2Stability of (2). In embodiments of the present invention, the inventors have found that Bi2(H2O)2(SO4)2(OH)2Has good stability, and can be used in water at room temperature and at a temperature of not higher than 250 deg.CCan exist stably under certain temperature.
In some embodiments of the invention, the chlorine removal agent is selected from the group consisting of concentrated sulfuric acid, water and Bi2O3Is prepared from the raw materials.
The dechlorinating agent of the invention is composed of Bi2(H2O)2(SO4)2(OH)2And water, wherein the preparation method of the dechlorinating agent comprises the following steps: adding concentrated sulfuric acid to Bi2O3-centrifuging the water slurry to remove water, and collecting the dechlorinating agent; preferably, the water removal is carried out at a temperature of not more than 250 deg.C, preferably not more than 200 deg.C.
It is to be noted that, when the dechlorinating agent is prepared by the present invention, the water is desalted water. The demineralized water can be prepared according to methods known in the art, as is well known to those skilled in the art.
The above preparation process may be reacted: bi2O3+2H2SO4+H2O＝Bi2(H2O)2(SO4)2(OH)2↓
In the embodiment of the present invention, the concentrated sulfuric acid needs to be slowly added to Bi with stirring2O3In aqueous slurry, if Bi is added2O3Added into concentrated sulfuric acid, and the surface layer reacts rapidly to form 'calculus' wrapping the bismuth oxide of the inner layer because of the instant non-uniform reaction, so that the Bi of the inner layer is prevented2O3The chlorine removal agent is not pure due to the transformation of (2) so that uneven 'caking' is formed after the chlorine removal agent is prepared. Therefore, in the embodiment of the present invention, Bi is used2O3Can be fully converted into a dechlorination medicament, Bi should be added firstly2O3To produce Bi2O3And after the slurry is obtained, slowly adding concentrated sulfuric acid.
In an embodiment of the present invention, Bi2(H2O)2(SO4)2(OH)2The dechlorination reaction produces a dechlorination product BiOCl, and the reaction is as follows:
Bi2(H2O)2(SO4)2(OH)2+2Cl-＝2BiOCl↓+2H++2SO4 2-+2H2O
therefore, the dechlorination product of the invention is mainly BiOCl; under well-controlled conditions, almost all of the dechlorinated product is BiOCl and no longer contains the reactant Bi2(H2O)2(SO4)2(OH)2. Such reaction conditions are for example Bi2(H2O)2(SO4)2(OH)2With Bi3+Measured as Bi3+：Cl-The dosage of which is 0.8-1:1, especially Bi3+：Cl-More preferably, the ratio is 0.8: 1.
In an embodiment of the invention, the dechlorination product BiOCl has a plate-like rod-like morphology.
In an embodiment of the present invention, the recycled material is Bi2O3Which retains Bi2(H2O)2(SO4)2(OH)2The smooth rod-like morphology.
In some embodiments of the invention, the regeneration treatment comprises treating the chlorine removal product with a NaOH solution, and the reaction that produces a regenerated product upon regeneration is as follows:
2BiOCl+2NaOH＝2NaCl+Bi2O3+H2O
in the implementation process of the invention, the concentration of NaOH solution is 1-5mol/L, and the treated Bi is obtained2O3All maintain Bi2(H2O)2(SO4)2(OH)2The processing time of the NaOH solution is 1 hour or can be prolonged properly.
It is worth noting that in the prior art, the treatment of BiOCl with sodium hydroxide often requires the addition of Bi2O3Completely different from the seed crystal (for example, the seed crystal with the BiOCl amount of 5-40 wt% needs to be added in a report), and/or the seed crystal can be realized only by increasing the temperature (for example, the seed crystal needs to be increased to 70-95 ℃ in a report), the method adopts the sodium hydroxide treatment, has natural operation, can realize the conversion at normal temperature, and does not need to additionally add the seed crystal. In some embodiments, the hydrogen hydroxideThe concentration of the sodium solution is 1-5mol/L, and the Bi obtained after the sodium hydroxide treatment2O3Has a smooth rod-like structure.
In some embodiments of the invention, preparing the chlorine removal agent from the regeneration product comprises adding concentrated sulfuric acid to an aqueous slurry of the regeneration product; wherein, concentrated sulfuric acid needs to be added slowly with stirring.
In the embodiment of the invention, the chlorine removal product can be purified and then regenerated.
With Bi3+：Cl-When the chlorine removal is carried out to obtain the dechlorinated product with the feeding amount of 0.8-1:1, Bi is used3+：Cl-When the ratio of the reactant to the chlorine removal product is 0.8:1, the content of the reactant in the chlorine removal product is less, and the purity of the BiOCl can reach 99% without purifying the chlorine removal product.
The purification process may include: and after the dechlorination reaction is finished, performing centrifugal dehydration to obtain a dechlorination product, and performing wet purification or dry purification on the dechlorination product to obtain a purified product. Wherein, the wet purification adopts dilute nitric acid to treat dechlorination products, the concentration of the dilute nitric acid is preferably 0.5-5%, and particularly, in the products purified by 5% nitric acid, the purity of BiOCl is greatly improved, and the purity of BiOCl can be improved to 99.6822% from unpurified 99.096%.
The purified product obtained by wet purification retains the sheet structure of BiOCl and is gathered in the shape of a short rod.
The dry purification can calcine the dechlorination product at the temperature of 700-850 ℃, and the reaction can occur in the calcining process:
Figure BDA0003033807860000041
Figure BDA0003033807860000042
wherein, BiCl3BiCl capable of reacting when meeting water3+H2O → BiOCl +2HCl, to regenerate BiOCl, BiCl produced in cold wells when calcined at 800 deg.C3Has the highest content of 800Calcination at a temperature of preferably.
Further, in an embodiment of the present invention, the cyclic dechlorination process of the present invention comprises: adding Bi2(H2O)2(SO4)2(OH)2Or with Bi2(H2O)2(SO4)2(OH)2Adding a dechlorinating agent serving as an active ingredient into chlorine-containing wastewater for dechlorinating reaction, after centrifugal dehydration, putting a dechlorinating product mainly comprising BiOCl into a NaOH solution for regeneration to obtain a regenerated product Bi with a smooth rod-shaped appearance2O3Adding concentrated sulfuric acid slowly into the regenerated product while stirring to prepare Bi2(H2O)2(SO4)2(OH)2Adding Bi2(H2O)2(SO4)2(OH)2Continuously adding the mixture into chlorine-containing wastewater for dechlorination, or directly adding a regenerated product Bi with a smooth rod-shaped appearance2O3Adding the mixture into acidic chlorine-containing wastewater to perform dechlorination reaction.
Directly adding a reproduction Bi product with a smooth rod-like appearance2O3When the raw materials are added into the acidic chlorine-containing wastewater for dechlorination reaction, the generated dechlorination reaction is as follows: bi2O3+2H++2Cl-→2BiOCl+H2O, the dechlorination product is still BiOCl, and the regeneration can be carried out again so as to realize the dechlorination circulation.
In an embodiment of the present invention, the chlorine-containing wastewater is preferably desulfurization wastewater. The desulfurized wastewater can be subjected to the cyclic dechlorination of the invention after conventional pretreatment in the field.
In a second aspect of the present invention, the present invention provides a cyclic chlorine removal system comprising: a chlorine removal reaction unit, a centrifugal dehydration unit and a regeneration unit;
a dechlorination reaction unit in which a dechlorination reaction can occur to generate a dechlorination reaction liquid;
the centrifugal dehydration unit at least comprises 2 groups of centrifugal dehydration units 1 and 2, which are used for receiving reaction liquid and obtaining reaction products through centrifugal dehydration;
the centrifugal dehydration unit 1 is respectively connected with the dechlorination reaction unit and the regeneration unit and is used for receiving the dechlorination reaction liquid and obtaining a dechlorination product through centrifugal dehydration;
the regeneration unit is used for receiving the dechlorination product generated by the centrifugal dehydration unit 1, and regenerating the dechlorination product in the regeneration unit to generate regenerated reaction liquid;
a centrifugal dehydration unit 2 which is respectively connected with the regeneration unit and the dechlorination reaction unit and is used for receiving the regeneration reaction liquid and obtaining a regenerated product through centrifugal dehydration; and (4) enabling the regenerated product to enter a dechlorination reaction unit, adding acid to continue the dechlorination reaction, and completing the cycle of the dechlorination reaction.
In some embodiments of the invention, the centrifugal dewatering unit further comprises a centrifugal dewatering unit 3 and a chlorine scavenger preparation unit;
the centrifugal dehydration unit 3 is respectively connected with the dechlorinating agent preparation unit and the dechlorinating reaction unit and is used for receiving the dechlorinating agent preparation reaction liquid and obtaining the dechlorinating agent through centrifugal dehydration; the chlorine removing agent enters a chlorine removing reaction unit connected with the centrifugal dehydration unit 3 to complete the circulation of the chlorine removing reaction.
And, optionally, the system may further comprise a chlorine removal product purification unit disposed between the centrifugal dehydration unit 1 and the regeneration unit for purifying the chlorine removal product.
Compared with the prior art, the invention has the advantages that:
the cyclic dechlorination process of the invention uses Bi2(H2O)2(SO4)2(OH)2Or with Bi2(H2O)2(SO4)2(OH)2The dechlorination agent which is an active component is used for dechlorinating the wastewater for the first time, the dechlorinating efficiency can reach more than 95 percent in 10 minutes and can reach 99 percent in 1 hour. The dechlorination product generated in the dechlorination process is mainly BiOCl, the purity of the dechlorination product can reach 99 percent, and the dechlorination product can be regenerated by treating the dechlorination product with NaOH solution to obtain Bi2O3，Bi2O3Inherit the original dechlorinating agent Bi2(H2O)2(SO4)2(OH)2Smooth rod-like morphology of Bi obtained2O3The dechlorination reaction can be directly carried out with the chlorine-containing wastewater by adding acid, and in some embodiments of the invention, the regeneration product is directly used for dechlorination (the initial concentration of chloride ions is 5000mg/L, Bi is3+(derived from Bi)2O3)：Cl-The molar ratio of (1: 1), the dechlorination efficiency is more than 80%, and the dechlorination product generated by the dechlorination is still BiOCl, so that the dechlorination circulation can be realized; and, the obtained regenerated product Bi2O3Can also be used for continuously preparing the dechlorinating agent Bi2(H2O)2(SO4)2(OH)2The chlorine removal agent is continuously used for removing chlorine, so that circulation is realized; in some embodiments of the invention, after 6 cycles, the chlorine removal agent and the recycled Bi are obtained2O3The rod-shaped appearance can be kept, and the dechlorination efficiency is still kept above 80% in the 6 th time; in addition, in the above cycle, the loss of Bi is not so large. The technical scheme of the invention realizes the defects of poor dechlorination effect and difficult recycling of the existing dechlorinating agent, improves the dechlorination efficiency, realizes the recycling of the dechlorination process, reduces the cost and realizes the industrial application of the bismuth-containing dechlorinating agent.
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The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the application and, together with the description, serve to explain the application and are not intended to limit the application. Embodiments of the present application are described in detail below with reference to the attached drawing figures, wherein:
FIG. 1 shows the addition procedure for the preparation of the chlorine scavenger of example 1; wherein, (a) demineralized water is added into the preparation box, and (b) Bi is added2O3(c) continuing to add Bi2O3，(d)Bi2O3The adding is finished, (e) the sulfuric acid is added.
FIG. 2 shows a collection procedure for preparing the chlorine scavenger of example 1; wherein, (a) water is discharged by centrifugation, (b) a dechlorinating agent film on the filter cloth, and (c, d) collected dechlorinating agent powder.
FIG. 3 is an XRD pattern of the chlorine remover prepared in example 1.
FIG. 4 is an SEM topography of the chlorine removal agent prepared in example 1.
FIG. 5 is a graph showing the size distribution of the chlorine scavenger obtained in example 1.
FIG. 6 is an SEM image (a) of the chlorine scavenger prepared in example 1 and an EDS energy spectrum (b-d) of three points thereof.
FIG. 7 is the SEM image (a) and the element surface scanning distribution diagram, the overlay diagram (e) and the EDS energy spectrum diagram (f) of Bi (b), S (c), O (d) of the chlorine scavenger prepared in example 1.
FIG. 8 example 2 feed procedure for preparing a dechlorinating agent; wherein, (a) adding demineralized water, (b) adding concentrated sulfuric acid, and (c) adding Bi2O3， (d)Bi2O3Immediately after the addition, (e) after stirring for 1.5 hours.
FIG. 9 is a collection procedure for preparing a chlorine scavenger in example 2; wherein, the filter cloth of 600 meshes is centrifuged, (b) the filter cloth of 600 meshes is centrifuged to discharge water, (c) the dechlorination medicament on the filter cloth of 600 meshes, (d) the filter cloth of 4000 meshes is centrifuged to discharge water, (e) the dechlorination medicament collected.
FIG. 10 shows the charging and collecting processes for preparing the chlorine scavenger of example 3; wherein (a) a small amount of Bi is added into the preparation tank immediately after the addition of the desalted water and the sulfuric acid2O3(b, c) continuing to add Bi2O3(d) adding Bi completely2O3Stirring for a period of time, and (e) centrifuging through 8000-mesh filter cloth.
FIG. 11 is a photograph of desulfurized wastewater, wherein (a) optical photographs of desulfurized wastewater before and after precipitation (left: original desulfurized wastewater and precipitation thereof; right: desulfurized wastewater after flocculation precipitation); (b) optical photos of the desulfurized wastewater after flocculation precipitation in a preparation box; (c) dechlorinating agent Bi3+:Cl-Adding the wastewater reaction solution and the precipitate thereof into the reactor at a ratio of 1:1 for reaction for 10, 30 and 60 minutes (from left to right); (d) dechlorinating agent Bi3+:Cl-The reaction solution of the wastewater taken from 10, 30 and 60 minutes (left to right) and the precipitate thereof are added at a ratio of 0.8: 1.
FIG. 12 is an XRD pattern of the original desulfurization waste water precipitate in example 4.
FIG. 13 is an XRD pattern of the product of example 5, which was obtained by laboratory centrifugation of the dechlorination reaction solution for 10min, 30min and 60min, and A is Bi3+:Cl-1:1 conditionRemoving chlorine products; b is Bi3+:Cl-Dechlorination product under 0.8:1 conditions.
FIG. 14 is the XRD pattern of the product of 60min centrifugal test in the dechlorination reaction solution in example 5, A is Bi3+:Cl-Dechlorination product under 1:1 conditions; b is Bi3+:Cl-Dechlorination product under 0.8:1 conditions.
FIG. 15 shows Bi in example 53+:Cl-SEM morphology of the centrifuged dechlorinated product under 1:1 conditions.
FIG. 16 shows Bi in example 53+:Cl-Size distribution of the chlorine removal product by centrifugation under 1:1 conditions.
FIG. 17 shows Bi in example 53+:Cl-SEM spectra of the dechlorinated product (a) and its point locations (b-e) under 1:1 conditions.
FIG. 18 shows Bi in example 53+:Cl-SEM topography of the centrifuged dechlorinated product under 1:1 conditions (a) and elemental surface scans thereof (b) Bi, (c) Cl, (d) O, (e) S and (f) overlay images thereof.
FIG. 19 shows Bi in example 53+:Cl-EDS (electron density distribution) spectrogram obtained by scanning a centrifugal dechlorination product element plane under the condition of 1:1, wherein (a) the atomic percentage and (b) the mass percentage are shown in the EDS spectrogram.
FIG. 20 shows Bi in example 53+:Cl-SEM morphology of the product of centrifugation dechlorination under 0.8:1 conditions.
FIG. 21 shows Bi in example 53+:Cl-Size distribution of the chlorine removal product by centrifugation at 0.8: 1.
FIG. 22 shows Bi in example 53+:Cl-SEM topography of the dechlorinated product (a) and EDS spectra of its different sites (b-f) at 0.8: 1.
FIG. 23 shows Bi in example 53+:Cl-SEM topography and EDS profile of the centrifuged dechlorinated product (a) at 0.8:1 (b) Bi, (c) Cl, (d) O and (e) total energy spectra.
FIG. 24 shows Bi in example 53+:Cl-ICP test result of sample obtained by high-speed centrifugation of pilot test after 60 minutes reaction under 0.8:1 condition
FIG. 25Is Bi in example 73+:Cl-XRD patterns of the dechlorinated product after purification with different nitric acid concentrations under 0.8:1 conditions.
FIG. 26 shows Bi in example 73+:Cl-(a-d) SEM morphology of dechlorinated product after purification with 5mol/L nitric acid at 0.8: 1.
FIG. 27 shows Bi in example 73+:Cl-The dechlorinated product was purified with 5mol/L nitric acid under 0.8:1 conditions to give (a) a size profile of the rods and (b) a thickness profile of the sheet-like BiOCl.
FIG. 28 shows Bi in example 73+:Cl-XRD pattern of product in crucible after decomposition of dechlorinated product BiOCl at different temperatures under 0.8:1 conditions.
FIG. 29 is SEM images of the products in the crucible after decomposition of BiOCl at different temperatures in example 7 (a, b) at 750 ℃, (c, d) at 800 ℃, (e, f) at 850 ℃.
FIG. 30 is an XRD pattern of the product of example 7 in a cold well after decomposition of the dechlorination product BiOCl at different temperatures.
FIG. 31 is an XRD pattern of the dechlorination product BiOCl obtained in example 8 after treatment with different concentrations of NaOH.
FIG. 32 is an SEM image of the products of example 8 after the dechlorination product BiOCl was regenerated with different NaOH solutions, wherein (a) the SEM image is 0.5mol/L, (b) the SEM image is 1.0mol/L, (c) the SEM image is 2.0mol/L, (d) the SEM image is 3.0mol/L, and (e) the SEM image is 5.0 mol/L.
Detailed Description
The present application is further illustrated with reference to specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present application. Experimental procedures without specific conditions noted in the following examples, generally according to conventional conditions or according to conditions recommended by the manufacturer.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. The reagents or starting materials used in the present application can be purchased from conventional sources, and unless otherwise specified, the reagents or starting materials used in the present application can be used in the conventional manner in the art or in the product specification. In addition, any methods and materials similar or equivalent to those described herein can be used in the methods of the present application. The preferred embodiments and materials described herein are intended to be exemplary only.
The chlorine removal agent is in a pilot test result acceptance stage when being reported, and pilot test result research shows that the chlorine removal agent is suitable for mass production and cyclic chlorine removal, and the loss amount of Bi is small when the chlorine removal agent is used circularly. Therefore, the following examples of the present invention are presented in a pilot plant process, and it is understood that the examples are presented only for illustrating a part of the pilot plant experiments of the present invention. For scale-up and laboratory implementation, the applicant believes that it must be understood by those skilled in the art that the technical solution that can be implemented in the laboratory stage is not representative of the solution that can be implemented in mass production or application, because the instruments, the quantities and the problems to be solved in the laboratory stage are not at all on one order compared to the pilot stage, for example, in terms of the quantities, the pilot stage is an amplification stage, generally from milligram or gram to kilogram, or milligram or gram to ton; for example, in terms of the problems to be solved and considered, the problems considered in the pilot plant are different from those in the laboratory development stage, the research and development stage only considers how to implement the technical solution, and the pilot plant needs to consider more factors such as cost, equipment, safety, and influence on the environment, for example, in the laboratory, the used instruments are basically glass, so that the reaction materials do not need to be considered too much, while in the pilot plant, the problems such as whether the reaction solution is acidic, strongly corrosive, easily generating static electricity, easily solidifying are considered, the stirring effect, the heating mode, the post-treatment mode, the environmental protection problem (such as recycling and reusing of the solvent, which is hardly considered in the laboratory due to the small amount used), and the like are considered, and in the separation experiment, the reaction solution is layered after centrifugation in a laboratory transparent multi-purpose container such as a separating funnel, The centrifugal tube is transparent and visible at a glance, which never causes problems, but equipment in a workshop cannot be transparent and visible due to the fact that the equipment is limited by materials and environments, and only can be observed by using a sight glass, and the difference is conceivable.
Example 1Preparation of dechlorinating agent
The diameter and height of the preparation box are both 1.3m, and the area of the bottom surface is 1.32665m2. The liquid surface height of 100L of the solution was 0.07538m, i.e., a height of about 7.5 cm. The stirrer is approximately 20cm from the bottom.
The demineralized water valve of the reactor was opened, 600L of demineralized water (the amount of water was determined by measuring the height of the liquid level in the preparation tank) was added and the stirrer was switched on, see fig. 1 a. Adding 100kg (four barrels) of Bi2O3L of raw material (FIGS. 1b-c), 100L of sulfuric acid was slowly added while stirring by opening the sulfuric acid tank lift pump and associated valves (FIG. 1 e). The reaction vessel lid was closed and stirred for 2 hours. After the reaction is finished, a valve connected with the centrifuge is opened, the slurry is transferred to the centrifuge in batches for dehydration, the supernatant is directly discharged after passing through filter cloth (8000 meshes) of the centrifuge, and the effluent is clear (figure 2a), which shows that the loss of Bi is less. Firstly centrifuging at low speed and then centrifuging at high speed for dewatering, wherein the chlorine removal agent film on the filter cloth is white (figure 2b) and has no yellow block, and the chlorine removal agent is collected and filled and marked (figures 2c and d), so that 8 barrels can be collected.
To calculate the water content in the chlorine remover, the number, weight and water content of the collected 8 barrels are shown in table 1. The calculation of the solid content corresponds to the samples with corresponding numbers, and the samples are dried in a drying oven at 105 ℃ for 12 hours, and the weight loss is the mass of the water. As can be seen from Table 3-1, the minimum water content was about 9% after high-speed centrifugation. In addition, Bi2(H2O)2(SO4)2(OH)2It is stable in structure and does not dehydrate under the condition of not higher than 280 ℃.
TABLE 1
Figure BDA0003033807860000081
Figure BDA0003033807860000091
The chemical reaction formula for preparing the dechlorinating agent is as follows:
Bi2O3+2H2SO4+H2O＝Bi2(H2O)2(SO4)2(OH)2↓
100kg of Bi2O3Generating active ingredient Bi of theoretical dechlorinating agent2(H2O)2(SO4)2(OH)2The mass of (2) is 146.24kg, which is slightly different from the actual collected total mass of 151.91kg (actually, slightly higher water content can be caused by sampling error and water content error in the drying process, because the drying box has no air blowing device, the interior of the medicament can not be completely dried, but when the medicament is taken back to a laboratory for drying, the water content is not greatly different from the result of a pilot plant.
Characterization of the dechlorinating agent:
(1) XRD analysis of dechlorinating agent
The XRD pattern of the chlorine scavenger is shown in FIG. 3, from which it can be seen that all diffraction peaks correspond to Bi2(H2O)2(SO4)2(OH)2(PDF card number: 76-1103) showing all Bi dosed during the pilot run2O3Are all converted into Bi2(H2O)2(SO4)2(OH)2. The obtained dechlorination medicament has high purity of at least more than 99 percent.
(2) Morphology analysis of dechlorinating agent SEM
The SEM appearance of the chlorine removal agent is shown in FIG. 4, and it can be seen that the chlorine removal agent has a rod-like appearance. These rods were not uniform in size and had a small amount of aggregates. According to their size statistics, as shown in FIG. 5, the length of the rods ranged from 1.9 to 33.7 μm, mainly centered at 5 to 20 μm, with an average length of 10.6 μm; the diameter of the rod-shaped body is 0.6 to 3.7 μm, mainly centered at 1 to 3 μm, and the average diameter is 1.9 μm.
(3) EDS (electron-dispersive spectroscopy) analysis of dechlorinating agent
The chlorine remover was analyzed by the element analysis shown in FIG. 6, and the test was performed by dotting from three positions (FIG. 6a) of the chlorine remover stick, and the results were shown in FIG. 6b, FIG. 6c and FIG. 6d, in which the element signals of Bi, O and S are mainly listed, and the element signals of H are not accurate and not listed. In which the chlorine-removing agent rod is in three positionsThe atomic percentages (molar ratio) of Bi and S are both 1:1, which accords with the molecular formula of the dechlorinating agent Bi2(H2O)2(SO4)2(OH)2The theoretical ratio of Bi to S in the solution.
FIG. 7 shows the results of the element surface scan analysis of the chlorine scavenger. The elements Bi (fig. 7b), S (fig. 7c) and O (fig. 7d) are uniformly distributed along the rod morphology in fig. 7 a. As is clear from the superposition of these elements with the SEM image (FIG. 7e), these rods were all Bi2(H2O)2(SO4)2(OH)2The atomic percentages of Bi and S are also 1: 1.
Example 2
Adding 500L of high-purity desalted water into a medicament preparation box (figure 8a), opening a stirrer, slowly adding 67L of concentrated sulfuric acid by using a concentrated sulfuric acid metering pump (the sulfuric acid metering pump works for half an hour at 100%; theoretically 106L should be added, and the addition is less because of errors in observing the liquid level), as shown in figure 8b, adding 100kg of bismuth oxide after stirring for 10min (figures 8c and 8d), and continuing stirring for 1.5 hours until the medicament turns white (figure 8e), which indicates that the preparation of the medicament is basically finished. In fact, in the range where meat is visible, the white color immediately after the addition of bismuth oxide is not much different from that after 1.5 hours of stirring.
After stirring for 1.5 hours, the prepared slurry was introduced into a centrifugal dehydration apparatus for centrifugal dehydration, and the separated dilute sulfuric acid aqueous solution was introduced into a stock tank for storage. The filter cloth used at the beginning is 600 meshes, as shown in figure 9a, the effluent after centrifugation is shown in figure 9b, the effluent is relatively white, and a certain amount of dechlorination agent is carried. Fig. 9c shows the dechlorination agent obtained after the 600 mesh filter cloth is centrifugally dewatered, and the dechlorination agent film also contains unreacted yellow bismuth oxide, and the sources of the yellow bismuth oxide are primarily considered to be two: firstly, preparing unreacted bismuth oxide in a box connecting pipe; one is due to the lack of concentrated sulfuric acid added, resulting in a certain amount of caking in the obtained dechlorinating agent (fig. 9 e). After the filter cloth of 4000 meshes is used, the centrifuged water is clear, and is shown in FIG. 9 d.
Example 3
Aiming at the problems of too small dosage of sulfuric acid and insufficient mesh number of filter cloth in the embodiment 2, the embodiment adds enough sulfuric acid and adopts 8000 meshes of filter cloth. The experimental procedure was as follows:
the demineralized water valve of the reactor was opened and 600L of demineralized water was added (the amount of water was determined by measuring the height of the liquid level in the preparation tank and the inner diameter of the reactor). The stirrer was turned on and the sulfuric acid tank lift pump and associated valves were opened to add 100L of sulfuric acid while stirring. Adding 100kg of Bi slowly (the actual adding speed is faster than that of the first pilot test)2O3L feedstock (four barrels), see fig. 10 a-c. The reaction chamber lid was closed and after stirring for 2 hours, unreacted yellow block powder was still present in the preparation chamber (fig. 10 d). After the reaction is finished, a valve connected with a centrifugal machine is opened, the slurry is transferred to the centrifugal machine in batches for dehydration, and the supernatant is directly discharged after passing through filter cloth (8000 meshes) of the centrifugal machine. After the centrifugal dehydration is completed, unreacted yellow powder agglomerates still exist in the dechlorinating agent film on the surface layer of the filter cloth, and the filter cloth is damaged.
The reason for the problem is as follows: bi2O3When the powder is added into the sulfuric acid solution, the surface layer reacts rapidly to form 'calculus' to wrap the bismuth oxide of the inner layer because the powder is not reacted uniformly instantly when added, and the Bi of the inner layer is prevented2O3The transformation of (2) causes the medicament to form uneven 'lumps' after the preparation, which leads to impure dechlorination medicament.
Example 4Pretreatment of desulfurization wastewater
The original desulfurization waste water is brownish yellow, the pH value of the stock solution of the supernatant is 5.65, and brownish yellow precipitates can be obtained after self-precipitation (fig. 11a, left). The XRD pattern of this brown-yellow precipitate is shown in FIG. 12. As can be seen, this brown-yellow precipitate contains mainly four phases: SiO 22、 CaAl2Si2O8·4H2O、KAl2(AlSi3O10)(OH)2And CaSO4·2H2O。
The desulfurization wastewater is lifted to a preparation tank by a pump, filtered by 8000 meshes of filter cloth and then flows into a storage tank. In order to improve the settling property of the desulfurization wastewater, a small amount of flocculant (1L of flocculant is added into 6 cubic meters of desulfurization wastewater) is added. After 12 hours of settling, the supernatant was relatively pure and the bottom settled very little (right in FIG. 11 a), which was difficult to collect efficiently for XRD testing. At this time, the pH was 3.23 and the chloride ion concentration was 8825mg/L, and this was used as chlorine-containing wastewater to conduct dechlorination (FIG. 11 b).
Example 5Dechlorination reaction
The dechlorination reaction equation is as follows:
Bi2(H2O)2(SO4)2(OH)2+2Cl-＝2BiOCl↓+2H++2SO42-+2H2O
according to the concentration of chloride ions, respectively according to Bi3+With Cl-The molar ratio of (1: 1) to (0.8: 1) is added with a dechlorinating agent in a manner of converting the dry weight into the water content of each container. The calculation process is as follows:
the dosage of the traditional Chinese medicine in the wastewater is as follows:
Figure BDA0003033807860000111
wherein m isDechlorination agentIn units of kg, CChlorineThe concentration of chloride ions in the wastewater (kg/m)3) V is the volume m of the waste water3，M1The molar mass of chlorine is 35.5g/mol, M2The molar mass of the chlorine removing agent is 680g/mol, 1/2 is unit mole number of chlorine and Bi in the chlorine removing agent3+The molar ratio of (a) is the addition coefficient, namely Bi3+With Cl-Actual addition molar ratio of (a).
After the chlorine removing agent was added according to the chlorine content and water amount of the wastewater, the wastewater was stirred for 60 minutes, wherein a small amount of the reaction solution (FIGS. 11c and d) was scooped at time points 10, 30 and 60 minutes to test pH and Cl-And (4) calculating the dechlorination efficiency according to the ion concentration. After 60 minutes, standing for 2 hours, wherein the supernatant is dechlorination wastewater and precipitates to be dechlorination products. They are stirred and then automatically flow into a centrifugal machine for dehydration.
The dechlorination reaction process and the characterization thereof are as follows:
1. adding the desulfurized wastewater after flocculation precipitation into a preparation tank, wherein the volume of the desulfurized wastewater is 1m3The chloride ion content was 8825 mg/L. Adding a chlorine-removing medicament into the mixture,respectively according to Bi3+With Cl-The molar ratio of (1: 1) is added, 84.52Kg of dry dechlorination agent is respectively added, and the wet weight adding amount of the dechlorination agent is calculated according to the water content.
Wherein, Bi3+With Cl-The respective chlorine removal efficiencies at different times under the condition of a molar ratio of (1: 1) are shown in Table 2.
TABLE 2Bi3+:Cl-Chlorine removal efficiency at different times under 1:1 conditions
Reaction time (minutes) pH Chloride ion concentration (mg/L) Efficiency of chlorine removal
0 3.23 8825 —
10 0.75 325 96.3％
30 0.85 80 99.1％
60 1.00 64 99.3％
According to Bi3+:Cl-After the chlorine removal agent is added under the condition of 1:1, the reaction solution is centrifuged at high speed in a laboratory for 10 minutes, 30 minutes and 60 minutes, the XRD patterns of the obtained products are respectively shown in figure 13A, and the product is centrifuged at high speed for 60 minutes in a pilot plant.
As is clear from FIG. 13A, when the reaction was carried out for 10 minutes, a new main phase BiOCl appeared in the dechlorinated product, but a part of Bi remained2(H2O)2(SO4)2(OH)2As the reaction time was extended to 60 minutes, the intensity of diffraction peak of BiOCl increased, and Bi2(H2O)2(SO4)2(OH)2The diffraction peak intensity of (A) is reduced, indicating that Bi is consumed in the progress of the dechlorination reaction2(H2O)2(SO4)2(OH)2And generating a dechlorination product BiOCl; BiOCl and Bi thereof2(H2O)2(SO4)2(OH)2Is about 67.7% and 32.3%, respectively. The above is the laboratory centrifugation result after sampling, and there may be a deviation in sampling the uppermost layer due to the small sampling amount.
To calculate Bi more accurately3+:Cl-XRD analysis was performed on the dechlorination product after the high-speed centrifugation in the pilot plant as shown in FIG. 14A, wherein the main phase was BiOCl and the secondary phase was Bi in the XRD spectrum of the dechlorination product after centrifugation2(H2O)2(SO4)2(OH)2The result is consistent with the XRD result of the dechlorination product of the reaction liquid. But BiOCl and Bi2(H2O)2(SO4)2(OH)2The relative mass fractions of (A) and (B) were different and were 77.3% and 22.7%, respectively (Table 3).
TABLE 3Bi3+:Cl-Relative mass fraction of phase in reaction liquid product under 1:1 condition and dechlorination efficiency
Figure BDA0003033807860000112
Figure BDA0003033807860000121
Bi3+:Cl-The product of centrifugation dechlorination was SEM characterized under 1:1 conditions: according to Bi3+:Cl-The addition was carried out under 1:1 conditions, and the product of dechlorination by pilot plant high speed centrifugation with a reaction time of 60 minutes was taken for SEM morphology analysis as shown in fig. 15. From FIGS. 15a-d it can be seen that the chlorine removal product is composed mainly of platy rod structures and smooth rod structures. The smooth rod-like structure being unreacted Bi2(H2O)2(SO4)2(OH)2The topography is similar to that of fig. 4. The sheet-shaped rod-shaped structure is BiOCl, inherits the appearance of the chlorine removal agent, has the shortest length of 3.2 mu m and the longest length of 32.5 mu m, is mainly concentrated at 5-10 mu m, and has the average length of 8.9 mu m (figure 16); the diameter of the particles is 1.6 μm at the shortest and 13.9 μm at the longest, and the particles are mainly concentrated in the range of 1-6 μm, and the average diameter is 3.8 μm.
For Bi3+:Cl-Elemental analysis of the dechlorinated product by centrifugation under 1:1 conditions, as shown by the EDS point scan results in FIGS. 17a-e, the dechlorinated product contained a certain amount of S, which was derived from Bi2(H2O)2(SO4)2(OH)2. Except for S, no other impurity elements were detected.
Fig. 18 is the EDS surface scan results for sheet-like rod-like structures. As can be seen from FIGS. 18b, c and d, the elements Bi, Cl and O are uniformly distributed along the sheet in FIG. 18a, indicating that the sheet-like rod-like structure consists essentially of BiOCl. FIG. 18e is the element plane scanning signal of S, which may be caused by noise, because the S content in the sheet-like rod structure is very low (FIG. 19), and as can be seen from the element overlay of FIG. 18f, the sheet-like rod structure is mainly composed of Bi, O and Cl. Thus, Bi3+:Cl-Centrifugal dechlorination product under 1:1 conditionThe sheet-like rod-like structure of (1) is BiOCl, which is present together with an unreacted dechlorinating agent.
2. Adding the desulfurized wastewater after flocculation precipitation into a preparation tank, wherein the volume of the desulfurized wastewater is 0.8m3The chloride ion content was 8825 mg/L. Adding a dechlorinating agent according to Bi3+With Cl-The molar ratio of (1) to (2) is 0.8:1, 54.09Kg of dry dechlorination agent needs to be added, and the wet weight adding amount of the dechlorination agent is calculated according to the water content of the agent.
According to Table 4, after the addition, the reaction mixture was stirred for one hour, and the reaction mixture was taken at 0, 10, 30 and 60 minutes (FIG. 11d), centrifuged, and the chloride ion concentration and pH of the supernatant were measured, and the results are shown in Table 3. In Bi3+:Cl-The dechlorination efficiency reached 98.6% in 10 minutes, 99.3% in 30 minutes and 99.3% in 60 minutes under the condition of 0.8: 1. Most of the chlorine removal reaction is actually completed within 10 minutes.
TABLE 4 Bi3+:Cl-Chlorine removal efficiency at different times under the condition of 0.8:1
Reaction time (minutes) pH Chloride ion concentration (mg/L) Efficiency of chlorine removal
0 3.23 8825 —
10 0.86 120 98.6％
30 0.86 63 99.3％
60 0.86 60 99.3％
According to Bi3+:Cl-After the chlorine removal agent is added under the condition of 0.8:1, the reaction solution is taken for 10, 30 and 60 minutes and centrifuged at high speed in a laboratory, the XRD patterns of the obtained products are respectively shown in figure 13B, and the product is taken for 60 minutes by high-speed centrifugation in a pilot plant.
As can be seen from the figure, a new main phase BiOCl appears in the dechlorination product, and Bi is not obvious in the three groups of reactions2(H2O)2(SO4)2(OH)2Or the presence of other diffraction peaks. Indicating that the dechlorination product is below Bi3+:Cl-Under the condition of 1:1, the dechlorination reaction is rapid, the dechlorination efficiency is high, and the purity of the dechlorination product is high; purity is at least 95% above with very small (typically less than 5%) or amorphous content of crystalline material, according to XRD detection limits.
Bi3+:Cl-The product of centrifugal dechlorination XRD characterization under the condition of 0.8: 1: to calculate Bi more accurately3+:Cl-XRD analysis was performed on the dechlorination product after the high-speed centrifugation of the pilot plant at the phase mass ratio of 0.8:1, as shown in FIG. 14B, in the XRD pattern of the dechlorination product after the centrifugation, the main phase was BiOCl, no other impurities appeared, and the sample was similar to the sample of the reaction solution, which indicates that Bi is in Bi3+:Cl-The high-purity dechlorination product can be obtained under the condition that the molar ratio is less than or equal to 1:1The substance BiOCl.
Bi3+:Cl-The product of chlorine removal by centrifugation was SEM characterized under 0.8:1 conditions: according to Bi3+:Cl-The chlorine removal agent was added under the condition of 0.8:1, and SEM morphology analysis was performed on the chlorine removal product which had a reaction time of 60 minutes and was subjected to pilot-scale high-speed centrifugation, as shown in fig. 20. It can be seen that the chlorine removal product was essentially a flaky rod-like structure, and no smooth rod-like chlorine remover was observed. The sheet-like rod-shaped structure is BiOCl, inherits the appearance of the chlorine removal agent, has the shortest length of 2.5 mu m and the longest length of 18.2 mu m, is mainly concentrated at 5-11 mu m, and has the average length of 7.7 mu m (figure 21); the diameter of the particles is 1.2 μm at the shortest and 7.2 μm at the longest, and the particles are mainly concentrated in the range of 1-5 μm, and the average diameter is 3.1 μm. Bi3+:Cl-In the dechlorination product obtained under the condition of 0.8:1, no smooth rod-shaped dechlorinating agent Bi is found2(H2O)2(SO4)2(OH)2It shows that the dechlorination reaction is thorough and the use rate of the dechlorination agent is high.
Bi3+:Cl-Element characterization of the product of centrifugal dechlorination under the condition of 0.8: 1: FIGS. 22a-f are Bi3+:Cl-From the EDS spot scan of the centrifuged product under 0.8:1 conditions, it was found that the S content was 0 and that almost all of the obtained sheet-like rod-like structures were BiOCl. No peaks of other elements were found in the EDS spectra, indicating that the centrifuged product was relatively pure.
FIGS. 23a-e are Bi3+:Cl-EDS surface scan results of the centrifuged product under 0.8:1 conditions. Therefore, the elements Bi, Cl and O are uniformly distributed along the sheet-like morphology in FIG. 23a, and the content of S is 0, which further indicates that the sheet-like rod-like structure is BiOCl, and the purity is high.
Bi3+:Cl-And (3) carrying out ICP detection on the dechlorination product by centrifugation under the condition of 0.8: 1: due to the limitation of the detection precision of a Scanning Electron Microscope (SEM) energy spectrum, after being digested, the dechlorination product is sent to an analysis and test center of Shanghai university of transportation for testing by an inductively coupled plasma emission spectrometer (ICP-OES), and the dechlorination product is Bi3+:Cl-After reacting for 60 minutes under the condition of 0.8:1, performing high-speed centrifugation on the obtained sample in a pilot test, and testing the resultSee fig. 24. As can be seen from FIG. 24a, trace amounts of Ca, Mg, Na, S, Al, Fe, K and Si impurities (Cl and O elements could not be tested, and negative values indicate that such elements were not present) remained in the dechlorinated product; however, the Bi content is too high to exceed the detection limit, and a large error exists, as shown in FIG. 24b, and the value is only used for reference.
The purity of the dechlorinated product BiOCl is 99.096% by calculation through a deduction method, and the specific algorithm is as follows:
99.096％＝100％-0.0023％(Al)-0.0001％(As)-0.0673％(Ca)-0.0000％(Cd)-0.0000％(Cr)-0.0007％(C u)-0.0038％(Fe)-0.0000％(Hg)-0.0230％(K)-0.0775％(Mg)-0.0338％(Na)-0.0003％(Ni)-0.0000％(Pb)-0. 6905％(S)-0.0045％(Si)-0.0005％(Zn)
ca. Impurities such as Mg, Na, Si, Al, Fe, K and the like are mainly derived from the desulfurization wastewater. As for the S element, the desulfurization waste water contains a certain amount of S, but mainly comes from residual Bi2(H2O)2(SO4)2(OH)2。
Example 6
This example compares the effect of chlorine removal with and without water.
1. Effect of chlorine removal agent after drying
The aqueous dechlorination agent prepared in example 1 was taken under laboratory conditions and dried in a forced air oven at 80 ℃ for 12 hours to obtain a water content comparable to the results of the pilot field tests. The XRD pattern of the drying dechlorination agent is consistent with that of figure 3 and is Bi2(H2O)2(SO4)2(OH)2The purity is close to 100%. Removing Bi in the chlorine agent3+Content and Cl in the desulfurization waste water-The ion content (8825mg/L) was added at molar ratios of 1:1, 0.8:1, 0.6:1 and 0.4:1 (total wastewater amount in each reaction was 200mL), and the chlorine removal efficiency after 10, 30 and 60 minutes of reaction was as shown in Table 5.
TABLE 5
Figure BDA0003033807860000141
2. Effect of chlorine removing agent after not drying
The wet dechlorinating agent obtained in example 1 was subjected to a dechlorination test under laboratory conditions, and Bi contained in the dechlorinating agent was determined according to the water content3+Content and Cl in the desulfurization waste water-The ion content (8825mg/L) was added at a molar ratio of 1:1, 0.8:1, 0.6:1 and 0.4:1 (total wastewater content in each reaction was 200mL), and the chlorine removal efficiency after 10, 30 and 60 minutes of reaction was as shown in Table 6.
TABLE 6
Figure BDA0003033807860000142
Comparing the dechlorinating effect of the dechlorinating agent with that of the dechlorinating agent without drying, Bi3+:Cl-Under the condition of different molar ratios, the chlorine removal efficiency of non-drying is higher, which is slightly higher than the content of the chlorine removal agent and possibly also than Bi thereof3+The ion release rate is related. The dried dechlorinating agent is easy to agglomerate in the baking and dehydrating process to cause the particles to become large, thereby influencing Bi in the dechlorinating reaction process3+Efficiency of ion release. Therefore, under the condition that the water content of the dechlorinating agent is accurately calculated, the dechlorinating agent for the pilot-scale high-speed centrifugal dehydration is not dried, and the cost such as electricity cost consumed by drying can be saved.
EXAMPLE 7 purification of the dechlorination product
By using Bi of example 53+:Cl-The purification operation was carried out on the dechlorination product under 0.8:1 conditions.
1. Purification by wet method
And (4) purifying by using dilute nitric acid. Respectively preparing 100mL of 0.5%, 1.0%, 2.0%, 3.0% and 5.0% diluted nitric acid solutions, and respectively adding 5g of pilot-plant Bi3+:Cl-0.8:1 dechlorination product. The XRD pattern of the product obtained after stirring for 1 hour is shown in FIG. 25. As can be seen from the figure, in the dechlorination product purified by different nitric acid concentrations, all XRD diffraction peaks correspond to BiOCl, and other miscellaneous peaks do not appear. Table 7 showsThe relative mass fractions of the phases in the product after treatment with different nitric acid concentrations are shown. According to the detection limit of XRD or the characteristics of amorphous substances, the relative mass fraction of BiOCl in all purified products with different nitric acid concentrations is more than 95%. SEM morphology characterization FIG. 26 is a pilot Bi test3+:Cl-SEM morphology of 0.8:1 dechlorinated product after purification with 5mol/L nitric acid. From the low-power (FIG. 26a) and high-power (FIGS. 26c-d) morphologies of the graphs, the purified product retained the sheet-like structure of BiOCl and aggregated in the form of short rods. FIG. 27a shows the size distribution of short rods, with a shortest dimension of 0.9 μm and a longest dimension of 5.4 μm, centered mainly at 1-5 μm, and an average diameter of 2.77 μm. FIG. 26d clearly shows the plate-like morphology of BiOCl, with the distribution of thickness dimensions of the plates as shown in FIG. 27b, the shortest dimension being 30.8nm and the longest dimension being 95.9nm, mainly centered at 45-90 nm, and the average thickness being 61.1 nm.
In the product purified by 5% nitric acid, the purity of BiOCl is improved from unpurified 99.096% to 99.6822%.
2. Purification by dry method
The chlorine removal product is purified by a dry method, and the chlorine removal product is calcined for 0.5 hour at 700 ℃, 750 ℃, 800 and 850 ℃ respectively. The XRD pattern of the product in the crucible after decomposition of the dechlorination product BiOCl at different temperatures is shown in figure 28. The relative mass fractions of the residue phases after the treatment are shown in Table 7.
TABLE 7
Figure BDA0003033807860000151
FIGS. 29a and b are SEM images of the product in the crucible after half an hour of treatment at 750 ℃ from which two appearances can be seen, the rod being Bi2O3The rest irregular flake materials are BiOCl which is not completely decomposed, and the surface layer of the BiOCl may be coated with Bi2O3. FIGS. 29c and d are the morphology of the product in the crucible after half an hour of treatment at 800 ℃ and it can be seen that there is still BiOCl which is not completely decomposed and Bi which is newly formed24O31Cl10It may exist primarily in a lamellar morphology. It can also be seen in the figureSmall amount of rod-like Bi2O3Mixed with the other two substances. FIGS. 29e and f are graphs of the product remaining in the crucible after half an hour of treatment at 850 deg.C, in which the appearance of platelet-like BiOCl completely disappeared and the large amount of paste present connected the rods, and it was preliminarily determined that the paste was predominantly Bi24O31Cl10The rod-like article is mainly Bi2O3。
Investigation of the influence of decomposition temperature on the product phase in the cold well: XRD was not provided when processing at 700 c, due to the difficulty of collection with only a trace of white powder in the cold well walls. After the sample was treated at 750 ℃ for half an hour, the powder collected in the cold well contained three phases, respectively BiCl3、Bi2O3And BiOCl. Wherein, BiCl3The diffraction peaks of (a) are mainly located at 2 θ (18.230 °), 19.392 °, 26.698 °, 30.414 °, 34.531 °, 37.748 °, 38.128 °, 42.009 °, and 43.591 °, corresponding to crystal planes (101), (020), (121), (220), (022), (230), (301), (222), and (141), respectively (PDF standard card number: 70-1519). Other diffraction peaks correspond to Bi2O3Or BiOCl. The XRD pattern of the product in the cold well after decomposition of the dechlorination product BiOCl at different temperatures is shown in figure 30, and the relative mass fraction of the phase in the cold well after decomposition of the dechlorination product BiOCl at different temperatures is shown in Table 8.
TABLE 8
Figure BDA0003033807860000161
Wherein, BiCl3Is formed by the decomposition of BiOCl, and the BiOCl heating reaction equation is as follows:
Figure BDA0003033807860000162
Figure BDA0003033807860000163
Bi2O3is mainly fromIs due to the volatile BiCl during the pyrolysis process3The gas or the flowing nitrogen will convert Bi with small size2O3The particles are brought into the cold well.
The source of BiOCl is mainly due to BiCl3It is very easy to encounter the decomposition of water by water absorption in air (during XRD test) to generate HCl and BiOCl, and the reaction equation is as follows:
BiCl3+H2O→BiOCl+2HCl
after the treatment for half an hour at 800 ℃, BiCl still remains in the product collected in the cold well3、Bi2O3And BiOCl, the relative mass fractions of which are 63.5%, 21.8% and 14.7%, respectively, wherein BiCl3The relative mass fraction of (a) is significantly increased. After half an hour of treatment at 850 ℃, the phase of the product collected by the cold well is also BiCl3、Bi2O3And BiOCl, their relative mass fractions being 61.3%, 23.3% and 15.4%, respectively. It can be seen that the temperature continues to rise, for BiCl3The magnitude of the increase in mass fraction is not large. From the above results, it was found that BiCl was obtained in the cold well when treated at 800 ℃3The highest relative mass fraction. E.g. to obtain BiCl of higher value3As a judgment standard, 800 ℃ is the optimum decomposition temperature.
Example 8
And putting the dechlorination product BiOCl into a NaOH solution for reaction. The reaction that occurs in solution is of the formula: 2BiOCl +2NaOH 2NaCl + Bi2O3+H2O, BiOCl can be converted to Bi by this reaction2O3Thereby realizing the aim of dechlorination.
The XRD pattern of the dechlorinated product BiOCl treated with NaOH at different concentrations is shown in figure 31. Of particular note is Bi obtained from the conversion of the dechlorinated product BiOCl of the present invention via the above reaction2O3Inherit Bi2(H2O)2(SO4)2(OH)2The rod-shaped appearance of the catalyst can have higher dechlorination performance in the subsequent dechlorination reaction. FIG. 32 shows regeneration after treatment with 0.5mol/L NaOH solutionThe SEM topography of the product can be seen, wherein some unreacted small-piece BiOCl still remains in the sample, and the rest blocky substances are newly generated Bi2O3. FIG. 32b shows the morphology of the regenerated product after treatment with 1.0mol/L NaOH solution, from which it is difficult to find flake-like BiOCl, and most of Bi has a rod-like morphology2O3I.e. Bi2O3Inherit Bi2(H2O)2(SO4)2(OH)2The rod-shaped appearance of the catalyst can have higher dechlorination performance in the subsequent dechlorination reaction. FIGS. 32c, d and e are the regenerated products treated by NaOH solutions of 2.0mol/L, 3.0mol/L and 5.0mol/L, respectively, and it is evident that the rod-like Bi2O3Combined together, exhibit flower-like crystals.
Bi obtained by treating NaOH with different concentrations2O3All are rod-shaped, have higher activity, can be directly used for removing chlorine, and can omit the re-synthesis of Bi2(H2O)2(SO4)2(OH)2The step (2).
The method comprises the following specific operations: at normal temperature, pH is 0.5, rotation speed is 500r/min, Bi3+:Cl-The mixture was stirred for 1h under the condition of a chloride ion concentration of 5000mg/L at 1: 1. The chemical reaction that takes place therein is as follows:
Bi2O3+2H++2Cl-→2BiOCl+H2O
the chlorine removal efficiencies were calculated, and as a result, as shown in Table 9, the chlorine removal efficiencies of the regenerated products obtained by the wet process were all maintained at about 80%.
TABLE 9
Concentration mol/L of sodium hydroxide Efficiency of chlorine removal
1 80.6％
2 77.3％
3 79.6％
5 79.6％
Bi to be regenerated2O3The method can perform dechlorination reaction with chlorine-containing wastewater under an acidic condition, the reaction product is still BiOCl, and the dechlorination product BiOCl can be regenerated again, so that a dechlorination cycle is realized, and after 6 cycles, the dechlorination efficiency is still about 80%.
In contrast, if Bi is used2O3(commercially available L-form) dechlorination under acidic conditions due to Bi2O3-L type does not contain Bi2(H2O)2(SO4)2(OH)2The remained smooth rod-like structure has a chlorine removal effect inferior to that of the regenerated product Bi of the present invention2O3Under the same conditions, the chlorine removal efficiency can be kept at about 75% after 1 hour of reaction, but the chlorine removal effect is difficult to maintain in circulation, and the chlorine removal efficiency is already remarkably reduced in the second time of chlorine removal.
Example 9Recycle and regeneration test
Step 1 preparation of Bi from dechlorinated product2O3
In the cyclic regeneration, 20g of dried pilot Bi are initially taken3+:Cl-The dechlorination product is treated by 5mol/L NaOH solution for 1 hour to obtain Bi2O3In the middle process, residual Bi such as the wall of the beaker is not scraped off intentionally2O3Finally drying to obtain 16g of Bi2O3. Theoretically 20g of the BiOCl dechlorination product gave 17.89g Bi2O3Therefore, the recovery rate of Bi was 89.4%.
Step 2.Bi2O3Preparation of dechlorinating agent
In the obtained 16g of Bi2O3Taking 10g of Bi2(H2O)2(SO4)2(OH)2To obtain 16g of a chlorine scavenger. 10g of Bi2O3Theoretically, 14.5g of dechlorinating agent can be obtained. Because the dechlorinating agent can be better collected in the beaker, the obtained dechlorinating agent has the mass which is larger than the theoretical value, and the error exists, but basically indicates that Bi is in Bi2O3The loss of bismuth in this step of the preparation of the dechlorinating agent is not great.
Step 3, dechlorinating agent dechlorinating
Of 16g of the chlorine removing agent, 15g of the chlorine removing agent was added to the wastewater to remove chlorine, and 10.65g of the chlorine removing product was obtained. 15g of dechlorinating agent theoretically gave 11.49g of BiOCl dechlorination product, and thus the recovery of Bi was 92.7%.
Step 4, dechlorination product preparation of Bi2O3
10.4g of 10.65g of the dechlorination product of BiOCl are treated with 5mol/L NaOH solution for 1 hour to obtain 8.8g of Bi2O3. 10.4g of BiOCl dechlorinating agent 9.3g of Bi can be obtained theoretically2O3Therefore, the recovery rate of Bi was 94.6%.
Step 5.Bi2O3Preparation of dechlorinating agent
At 8.8g Bi2O3In the above, 8.5g of the prepared chlorine removal agent was taken to obtain 14.1g of the chlorine removal agent. 8.5g Bi2O3In theory, 12.4g of dechlorinating agent can be obtained. This large recovery rate indicates a low loss of Bi during the preparation of the dechlorinating agent.
The dechlorinating agent has good Bi recovery rate and less loss in multiple cyclic regeneration. The amount of Bi lost in the recycle recovery test after 100-fold amplification of the pilot test has similar results.
The cyclic dechlorination is carried out according to the steps, the dechlorination efficiency can still be kept at about 80 percent after 6 times of cyclic dechlorination.
Although the present application has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications may be made to the technical solutions described in the foregoing embodiments, or equivalents may be substituted for some of the technical features thereof. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims (10)

1. The cyclic dechlorination process is characterized in that Bi is adopted2(H2O)2(SO4)2(OH)2Or with Bi2(H2O)2(SO4)2(OH)2The dechlorinating agent which is an active ingredient is dechlorinated, and the dechlorinating product after dechlorination is regenerated to obtain a regenerated product, so that the regenerated product is continuously used for preparing the dechlorinating agent to participate in dechlorination, or the regenerated product is continuously used for participating in dechlorination, and the circulation is carried out.
2. The cyclic dechlorination process of claim 1 wherein the Bi is2(H2O)2(SO4)2(OH)2Has a smooth rod-like morphology;
preferably, the chlorine removal agent can contain water or no water, and the water content is preferably not lower than 9%;
preferably, the dechlorinating agent is concentrated sulfuric acid, water and Bi2O3Is used as a raw material.
3. The cyclic chlorine removal process of claim 1 or 2, wherein the chlorine removal product comprises BiOCl; preferably, the dechlorination product BiOCl has a plate-like rod-like morphology.
4. The cyclic dechlorination process of claim 1 or 2 wherein the re-product is Bi2O3Which retains Bi2(H2O)2(SO4)2(OH)2The smooth rod-like morphology.
5. The cyclic dechlorination process of claim 1 or 2 wherein the regeneration treatment comprises treating the dechlorination product with a NaOH solution;
preferably, the concentration of the NaOH solution is 1-5 mol/L.
6. The cyclic chlorine removal process of claim 1 or 2, wherein preparing the chlorine removal agent from the regenerated product comprises adding concentrated sulfuric acid to an aqueous slurry of the regenerated product;
preferably, the concentrated sulfuric acid is added slowly with stirring.
7. The cyclic dechlorination process according to claim 1 or 2, wherein the dechlorination product is purified and then subjected to a regeneration treatment;
preferably, after the dechlorination reaction is finished, performing centrifugal dehydration to obtain a dechlorination product, and performing wet purification or dry purification on the dechlorination product to obtain a purified product;
preferably, the wet purification adopts dilute nitric acid to treat the dechlorination product, and the concentration of the dilute nitric acid is preferably 0.5-5%;
preferably, the purified product obtained by wet purification retains the sheet structure of BiOCl and is gathered in the shape of a short rod;
preferably, the dry purification comprises calcination of the dechlorinated product at 700-850 ℃, preferably at 800 ℃.
8. The cyclic dechlorination process of claim 1 or 2, wherein the process comprises: will be Bi2(H2O)2(SO4)2(OH)2Adding a dechlorinating agent serving as an active ingredient into chlorine-containing wastewater for dechlorinating reaction, after centrifugal dehydration, putting a dechlorinating product mainly comprising BiOCl into a NaOH solution for regeneration to obtain a regenerated product, stirring the regenerated product, and slowly adding concentrated sulfuric acid to prepare Bi2(H2O)2(SO4)2(OH)2As an active ingredient, a dechlorinating agent comprisingAnd (3) continuously adding the dechlorinating agent into the chlorine-containing wastewater to carry out dechlorination reaction, or directly adding the regenerated product into the acidic chlorine-containing wastewater to carry out dechlorination reaction.
9. A cyclic chlorine removal system based on the process of any one of claims 1 to 8, comprising: a chlorine removal reaction unit, a centrifugal dehydration unit and a regeneration unit;
a dechlorination reaction unit in which a dechlorination reaction can occur to generate a dechlorination reaction liquid;
the centrifugal dehydration unit at least comprises 2 groups of centrifugal dehydration units 1 and 2, which are used for receiving reaction liquid and obtaining reaction products through centrifugal dehydration;
the centrifugal dehydration unit 1 is respectively connected with the dechlorination reaction unit and the regeneration unit and is used for receiving the dechlorination reaction liquid and obtaining a dechlorination product through centrifugal dehydration;
the regeneration unit is used for receiving the dechlorination product generated by the centrifugal dehydration unit 1 and carrying out regeneration treatment on the dechlorination product in the regeneration unit to generate a regeneration reaction liquid;
a centrifugal dehydration unit 2 which is respectively connected with the regeneration unit and the dechlorination reaction unit and is used for receiving the regeneration reaction liquid and obtaining a regenerated product through centrifugal dehydration; and (4) enabling the regenerated product to enter a dechlorination reaction unit, adding acid to continue the dechlorination reaction, and completing the cycle of the dechlorination reaction.
10. The system of claim 9, wherein the centrifugal dewatering unit further comprises a centrifugal dewatering unit 3 and a chlorine scavenger preparation unit;
the centrifugal dehydration unit 3 is respectively connected with the dechlorinating agent preparation unit and the dechlorinating reaction unit and is used for receiving the dechlorinating agent preparation reaction liquid and obtaining the dechlorinating agent through centrifugal dehydration; the dechlorinating agent enters a dechlorinating reaction unit connected with the centrifugal dehydration unit 3 to complete the circulation of the dechlorinating reaction;
preferably, the system may further comprise a chlorine removal product purification unit disposed between the centrifugal dehydration unit 1 and the regeneration unit for purifying the chlorine removal product.
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115140824A (en) * 2022-07-19 2022-10-04 江苏理工学院 Wet regeneration method of bismuth oxychloride at low alkali concentration

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115140824A (en) * 2022-07-19 2022-10-04 江苏理工学院 Wet regeneration method of bismuth oxychloride at low alkali concentration
CN115140824B (en) * 2022-07-19 2023-11-03 江苏理工学院 Bismuth oxychloride wet regeneration method under low alkali concentration

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