CN112919752A - Method for preparing sludge treatment agent and method for treating sludge - Google Patents
Method for preparing sludge treatment agent and method for treating sludge Download PDFInfo
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- CN112919752A CN112919752A CN202011443294.7A CN202011443294A CN112919752A CN 112919752 A CN112919752 A CN 112919752A CN 202011443294 A CN202011443294 A CN 202011443294A CN 112919752 A CN112919752 A CN 112919752A
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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
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/004—Sludge detoxification
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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
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/006—Electrochemical treatment, e.g. electro-oxidation or electro-osmosis
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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
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Abstract
A method of preparing a sludge treatment agent and a method of treating sludge are provided. The method for preparing the sludge treating agent comprises the following steps: providing an iron-carbon filler; loading a layered double hydroxide on the iron-carbon filler; and carrying out first roasting on the iron-carbon filler loaded with the layered double hydroxide to obtain the sludge treatment agent. According to the concept of the invention, the heavy metal in the sludge can be removed and stabilized by adopting the iron-carbon filler to load the layered bimetal oxide.
Description
Technical Field
The invention belongs to the field of sludge treatment, and particularly relates to a method for preparing a sludge treatment agent and a method for treating sludge.
Background
In the sewage treatment process, most of pollutants in the sewage are transferred into the sludge through the actions of adsorption, precipitation and the like. The sludge consists of zoogloea formed by various microorganisms, organic matters and inorganic matters adsorbed by the zoogloea and water of the zoogloea, and particularly, harmful substances such as refractory organic matters, heavy metals, pathogenic microorganisms and the like in the sewage can be concentrated in the sludge after being separated.
The sludge heavy metal treatment method mainly comprises a biological leaching technology, a plant restoration technology, an electric restoration technology, a chemical forest washing method, an artificial wetland technology and the like.
The biological treatment technology mainly utilizes the reactions of oxidation, reduction, accumulation, metabolism and the like of microorganisms and heavy metals to remove the heavy metals in the sludge, however, the technology has long bioleaching retention time and high maintenance cost, can not be applied in a large scale, and is easy to cause the loss of nutrient elements in the sludge.
The plant restoration technology is used for enriching heavy metals in sludge through plants, transferring the heavy metals in the sludge into plants, enabling the plants to be unaffected, and then performing remote treatment and recovery through harvesting and other means. However, the plant extraction method is slow, inefficient, and not easy to dehydrate sludge.
The electric remediation removes heavy metals in the sludge by means of electric field action through electromigration, electroosmosis, electrophoresis and the like. The electric restoration technology has the advantages of short treatment time, simple installation and high heavy metal removal rate, can restore the sludge in situ, but has limited sludge amount per treatment and is combined with other treatment technologies for more use.
The chemical leaching method mainly removes heavy metals in the sludge through chemical reagents, and during the chemical leaching method, insoluble compound heavy metals in the sludge are converted into complex ion heavy metals through dissolution, leaching, ion exchange, acidification, complexation and the like. The chemical leaching method has good effect of removing heavy metals, but acid in the acidified sludge and the neutralized leachate consumes a large amount of chemical reagents and has higher requirement on equipment.
The artificial wetland technology mainly relates to an ecological system which is constructed artificially, supervised and controlled and is similar to a natural wetland, and the ecological system makes full use of the effects of plants, microorganisms, fillers, sunlight and other elements in the wetland system, so that the sludge can be effectively dewatered and reduced, the content of organic matters and heavy metals can be reduced, pathogenic bacteria can be removed, and the sludge is stabilized and harmlessly. However, the technology has significant problems in that it is costly, complicated in process, and has a risk of secondary contamination.
Therefore, a sludge treatment method capable of overcoming the above technical problems is required.
Disclosure of Invention
Aiming at the problems of low efficiency, high cost, incomplete removal and the like of removing heavy metals in sludge, the invention provides a method for preparing a sludge treating agent and a method for treating sludge, so that the heavy metals in the sludge can be removed in a recycling manner and passivated.
According to an aspect of the present invention, there is provided a method of preparing a sludge treating agent, the method comprising the steps of: providing an iron-carbon filler; loading layered double hydroxides on the iron-carbon filler; and carrying out first roasting on the iron-carbon filler loaded with the layered double hydroxide to obtain the sludge treatment agent.
The step of loading the layered double hydroxide on the iron-carbon filler may include: adding an iron-carbon filler to a reactor for preparing a layered double hydroxide; the layered double hydroxide is prepared in a reactor in which an iron-carbon filler is accommodated, thereby preparing the iron-carbon filler on which the layered double hydroxide is supported.
The roasting temperature of the first roasting can be 200-600 ℃, and the roasting time can be 2-6 h.
According to another aspect of the present invention, there is provided a method for treating sludge, which comprises subjecting sludge to a first treatment using the sludge treatment agent prepared by the above method.
The method may further comprise: and mixing the layered double hydroxides with attapulgite, carrying out secondary roasting on the mixture, and carrying out secondary treatment on the sludge by using a product of the secondary roasting.
The roasting temperature of the second roasting can be 200-600 ℃, and the roasting time can be 2-6 h.
The mass ratio of layered double hydroxide to attapulgite in the mixture may be in the range of 1:9 to 9: 1.
After the first treatment, the iron-carbon filler in the sludge may be separated, and the separated iron-carbon filler may be subjected to a third roasting.
The roasting temperature of the third roasting can be 300-800 ℃, and the roasting time can be 2-8 h.
The water content of the sludge can be 40 wt% -80 wt%.
From the above brief description, the inventive concept has the following beneficial effects, but is not limited to:
(1) the waste iron-carbon filler is used as a remover of heavy metals in the sludge, and the iron-carbon filler after the heavy metals are removed can be used for an ozone catalyst, so that the waste is recycled, and the use cost of the technology of removing and stabilizing the heavy metals in the sludge and the ozone catalytic oxidation is reduced;
(2) the heavy metal removal and passivation effect is obvious: the layered double-metal oxide has unique structure memory effect and adsorption effect, can efficiently remove heavy metals in sludge, and the treated sludge can meet the requirement of sludge land utilization;
(3) the synergistic passivation effect is outstanding: by doping and roasting the layered double hydroxides and the attapulgite, the heavy metal in the sludge can be synergistically passivated, and the stability of the sludge after passivation is ensured.
Drawings
FIG. 1 is a flowchart exemplarily showing a method of preparing a sludge treatment agent;
fig. 2 is a view exemplarily showing a layered structure of hydrotalcite;
fig. 3 is a view exemplarily showing a crystal structure of attapulgite.
Detailed Description
Hereinafter, the inventive concept will be described in detail with reference to the accompanying drawings, however, the following specific embodiments are only for sufficiently conveying the inventive concept to those skilled in the art, and do not limit the scope of the present invention. The scope of the invention is defined by the appended claims and equivalents thereof.
A large amount of sludge is produced in the sewage treatment process. The sludge consists of zooglea formed by various microorganisms, organic matters and inorganic matters adsorbed by the zooglea, and water of the zooglea, wherein the zooglea comprises a large amount of heavy metals and the like. In order to make full use of the sludge, it is necessary to remove heavy metals included in the sludge. In order to achieve the purpose, the invention mainly utilizes the sludge treatment agent of the iron-carbon filler loaded layered double-metal oxide to realize the high-efficiency and low-cost removal of heavy metals in the sludge.
The sludge treatment agent according to the present inventive concept can be obtained by providing an iron-carbon filler, a supported layered double hydroxide, and a preparation method of a roasting treatment. A flow chart of a method of preparing a sludge treatment agent according to the inventive concept is shown in fig. 1. Hereinafter, a method of preparing a sludge treating agent according to the present inventive concept will be described in detail.
Providing iron-carbon filler
The iron-carbon filler according to the present inventive concept may include an iron-carbon filler used in an iron-carbon micro-electrolysis process for sewage treatment. The iron-carbon microelectrolysis is a pretreatment process for sewage treatment, and the purpose of degrading organic pollutants is achieved by utilizing the potential difference generated by the microelectrolysis material of the iron-carbon filler in the wastewater under the condition of no power supply to carry out electrolytic treatment on the wastewater. Accordingly, the iron-carbon filler may include, but is not limited to, iron filings, charcoal, etc., and the inventive concept is not limited to the components of the iron-carbon filler and the ratio between the components, and those skilled in the art can obtain the iron-carbon filler of the inventive concept based on the prior art according to the inventive concept.
In addition, when the iron-carbon filler is used for sewage treatment, it may not be suitable for sewage treatment due to no longer having sewage treatment ability or reduced sewage treatment ability due to its change in properties (e.g., plate hardening), so that the iron-carbon filler used for sewage treatment no longer has any use value in the prior art. However, the invention can fully utilize the iron-carbon filler after sewage treatment, so that the waste can be recycled under the condition of efficiently removing heavy metals in the sludge, the sludge treatment cost is reduced, and the production cost is obviously reduced. However, the inventive concept is not limited thereto. That is, the inventive concept may be used with any form of iron carbon filler prior to and/or after use involved in the prior art wastewater treatment process.
According to the inventive concept, the iron carbon filler can be crushed after being selected. Here, the purpose of crushing is mainly to increase the contact area of the iron-carbon filler with the sludge, while increasing the contact area involved in the later step when loading the Layered Double Hydroxide (LDH), thereby improving the removal efficiency of the heavy metals. When the iron-carbon filler loaded with the layered double metal oxide (LDO) (obtained by roasting the layered double hydroxide, which will be described later) is added into the sludge, the iron-carbon filler with a large specific surface area can be sufficiently contacted with the sludge to reduce the reducible heavy metals in the sludge to low valence state and convert the reducible heavy metals into easily precipitated substances by using the chemical reduction effect of the iron-carbon filler, so that the toxicity of the heavy metals is reduced; meanwhile, the layered bimetal oxide which is loaded on the surface of the iron-carbon filler in a large amount through the large specific surface area of the iron-carbon filler can remove heavy metals in the sludge in a combined manner in cooperation with the iron-carbon filler in an adsorption manner.
Therefore, according to exemplary embodiments of the inventive concept, the iron-carbon filler may be crushed into small particles having a particle size of 5cm to 10cm, but the inventive concept is not limited to the particle size of the iron-carbon filler.
Supported layered double hydroxides
After the iron-carbon filler is provided, the layered double hydroxide may be supported on the iron-carbon filler.
The Layered Double Hydroxides (LDH) according to the present inventive concept are a class of prior art layered columnar compounds consisting of positively charged metal hydroxides and interlamellar packing exchangeable anions, and may be represented by the general chemical formula [ M2+ 1-xM3+ x(OH)2]x+(An-)x/n·yH2O, wherein M2+Represents a divalent metal ion (e.g., may be selected from Mg)2+、Ca2+、Sr2 +、Ba2+、Zn2+、Ni2+、Fe2+、Cu2+、Co2+、Mn2+One or more of the group of compositions, commonly used may be Ni2+、Co2+、Zn2+、Mg2+、Mn2+Etc.), M)3+Represents a trivalent metal ion (e.g., may be selected from Al)3+、Cr3+、Fe3+、V3+、Co3+、Ga3+、Ti3+One or more of the group of3+、Fe3+、Ti3+Etc.), x is 0.2-0.4, y is 0-2, An-Represents an interlayer anion (e.g., may be selected from CO)3 2-、NO3 -、SO4 2-、PO4 3-、Cl-One or more of the group consisting, commonly used, may be CO3 2-、NO3 -Etc.), n represents the valence number of the interlayer anion. Here, the layered double hydroxides according to exemplary embodiments of the inventive concept may include hydrotalcite and hydrotalcite-like compounds.
A typical composition of Hydrotalcite (HT) may be Mg6Al2(OH)16CO3·4H2O, the hydrotalcite has a structure similar to brucite (Mg (OH)2Brucite), octahedron with Mg2+Centered on OH-As a vertex, adjacent octahedrons form a layered compound through a common edge, the layers are orderly arranged, and the layers are combined through electrostatic attraction and hydrogen bonds. When the layers are isomorphously substituted by portions of similar radius, resulting in the accumulation of positive plate charge, the plates are CO-doped3 2-The plasma layers are separated and charge balance is achieved, and interlayer water exists in the form of crystal water, so that a layered structure of hydrotalcite is formed, as shown in fig. 1. In FIG. 1, A represents a brucite-like slab, B represents the height of channels between the surface layers, and C represents the interlayer region (in which interlayer anions and water molecules are present)
Hydrotalcite-like compounds obtained when metal cations in Hydrotalcite layers are partially or completely isomorphously substituted by other metal cations with similar radii or interlayer anions are exchanged by other anions are called hydrotalcites (hydrotalcites), and the chemical formula of the Hydrotalcite-like compounds can be: [ M ] A1-x 2+Mx 3+(OH)2]x+Ax/n n-·mH2O, wherein x is M3+/(M2++M3+) The molar ratio (which may range from0.22-0.33, outside of which only mixtures of hydrotalcite-like compounds with other compounds are obtained: when x is more than 0.337, boehmite (alpha-AlOOH) is generated; when x is more than 0.15 and less than 0.201, the product is brucite (4 MgCO)3·Mg(OH)2·4H2O); when x is less than 0.15, a mixture of brucite and magnesium hydroxide is generated), M is the mole number of interlayer crystal water, and M is2+、M3+Respectively, divalent and trivalent metal cations (e.g., Mg) occupying the central position of the octahedral structure of the complex hydroxide on the laminate2+、Zn2+、Cu2+、Co2+、Fe2+、Ni2+、Al3+、Fe3+、Ca3+、Cr3+、Mn3+Etc. these bivalent and bivalent metal cations with similar radiuses can synthesize various binary, ternary, quaternary and even quinary hydrotalcite HTlcs), An-Interlayer anions of different valences (e.g. Cl)-、I-、NO3 -、ClO4 -、CO3 2-、SO4 2-、CrO4 2-Iso inorganic anion, (V)10O28)6-、(Mo7O24)6-、(PMo12O40)3-Such as polyoxymetal ions and organic acid metal complexes). In addition, another hydrotalcite-like compound, so-called Pillared hydrotalcite (also called intercalated hydrotalcite), can be obtained by introducing bulky anionic groups (such as organic anions) into the interlayer.
Due to the above-mentioned layered nature of the layered double hydroxide, it can lose interlayer crystalline water and interlayer anions when it is fired, so that a Layered Double Oxide (LDO) having an unstable state can be formed. The layered bimetal oxide has larger specific surface area and good adsorption performance, and when loaded on the iron-carbon filler, the layered bimetal oxide can remove heavy metals in sludge by cooperating with the iron-carbon filler.
In order to support the layered double hydroxide on the iron-carbon filler, the iron-carbon filler may be added to the reactor in which the layered double hydroxide is formed before or during the formation of the layered double hydroxide, so that the iron-carbon filler may become a forming matrix of the layered double hydroxide. The layered double hydroxide (or the layered double oxide formed after roasting) can be firmly attached to the iron-carbon filler and cannot easily fall off by loading the layered double hydroxide through the method, so that the heavy metal in the sludge can be removed. According to specific examples, the preparation method of the layered double hydroxide may include, but is not limited to, a coprecipitation method, a hydrothermal synthesis method, etc., that is, the method of attaching the layered double hydroxide on the iron-carbon filler according to the inventive concept is not limited thereto.
In addition, the amount of the layered double hydroxide attached to the iron-carbon filler and the process conditions involved during the attachment process (e.g., raw materials, equipment, temperature, etc. for forming the layered double hydroxide) according to the inventive concept are not particularly limited, and one skilled in the art can adaptively adjust any process conditions involved during the attachment process and/or the corresponding relationship between the amount of the iron-carbon filler and the layered double hydroxide based on process selection, properties of the selected iron-carbon filler, and sludge treatment efficiency, and the inventive concept is not limited thereto.
Roasting treatment
After the layered double hydroxide is attached to the iron-carbon filler, the iron-carbon filler to which the layered double hydroxide is attached may be calcined at a suitable temperature to convert the layered double hydroxide into a layered double oxide.
Aiming at the roasting process for converting the layered double hydroxide into the layered double oxide, the roasting temperature can be 200-600 ℃, and the roasting time can be 2-6 h. However, as described above, the layered double hydroxide according to the inventive concept may have different compositions, and thus, different more detailed firing process conditions may be performed for different compositions. Specifically, the method comprises the following steps: when the loaded layered double hydroxide is NiAl-LDH, the roasting temperature can be 300-400 ℃, and the roasting temperature can be 2-4 h; when the supported layered double hydroxide is CoAl-LDH, the roasting temperature can be 300-400 ℃, and the roasting temperature can be 2-5 h; when the supported layered double hydroxide is NiFe-LDH, the roasting temperature can be 350-450 ℃, and the roasting temperature can be 3-4 h; when the loaded layered double hydroxide is CuAl-LDH, the roasting temperature can be 300-400 ℃, and the roasting temperature can be 2-4 h; when the loaded layered double hydroxide is ZnAl-LDH, the roasting temperature can be 350-450 ℃, and the roasting temperature can be 3-4 h; when the supported layered double hydroxide is MgFe-LDH, the roasting temperature can be 200-400 ℃, and the roasting temperature can be 2-4 h; when the supported layered double hydroxide is MgAl-LDH, the roasting temperature can be 350-450 ℃, and the roasting temperature can be 4-5 h.
After calcination, the layered double hydroxide supported on the iron-carbon filler may be converted into a layered double oxide. The layered bimetal oxide loaded on the surface of the iron-carbon filler has larger specific surface area and good adsorption performance, and can remove heavy metals in sludge by cooperating with the adsorption of the iron-carbon filler. On one hand, the layered bimetal oxide can adsorb heavy metal reduced by the iron-carbon filler on the surface of the iron-carbon filler by utilizing the adsorption performance of the layered bimetal oxide, and can adsorb heavy metal in an oxidizable state; on the other hand, it is also possible for the layered bimetallic oxide to bind acid-soluble heavy metals to convert them to a residue state and adsorb on the surface of the iron-carbon filler. In addition, the layered double hydroxide has unique 'structural memory effect' because the more stable layered double hydroxide loses crystal water and anions between layers after being roasted to become unstable layered double oxide. When the iron-carbon filler loaded with the layered double-metal oxide is added into the water-containing sludge, the layered double-metal oxide can insert various complex anionic metal pollutants or other anions into the layers to restore the original layered structure, so that the heavy metal can be at least partially removed. In addition, the layered double metal oxide has ion exchange performance, and the complexing anion metal can exchange with the interlayer anion of the layered double metal oxide to realize the removal of heavy metal. In conclusion, the layered double-metal oxide loaded on the surface of the iron-carbon filler can also remove heavy metals in the sludge by utilizing the structure memory effect and the ion exchange performance.
The method for preparing a sludge treating agent contemplated by the present invention is described above in detail with reference to the exemplary embodiments. By the method, the sludge treatment agent with the bimetallic oxide loaded on the iron-carbon filler can be prepared, so that heavy metals in the sludge can be effectively removed by the sludge treatment agent.
The sludge treatment agent disclosed by the invention is used for treating sludge, a large amount of heavy metals can be adsorbed on the surface of the iron-carbon filler, and the iron-carbon filler can be recycled by using the magnetic separator. The recovery treatment can comprise roasting the iron-carbon filler collected after the sludge treatment at the temperature of 300-800 ℃ for 2-8 h, and the roasted iron-carbon filler can be used for the catalyst for catalytic oxidation of ozone, the catalytic effect of the catalyst is better than that of the ozone catalyst used in the prior art due to the fact that heavy metal ions are loaded on the surface of the catalyst, meanwhile, the purchase cost of the catalyst is saved, and the recycling and utilization of resources are realized.
In addition, in order for the sludge treatment agent according to the present inventive concept to effectively treat the sludge while taking economic benefits into consideration, the amount of the sludge treatment agent of the present inventive concept added to the sludge, the water content of the sludge (the ratio of the weight of water in the sludge to the total weight of the water-containing sludge), and the treatment conditions may be controlled. Specifically, the adding amount of the sludge treatment agent of the present invention per kilogram of sludge can be in the range of 1g-50g, the water content of the sludge can be 40 wt% -80 wt%, and the sludge can be stirred during the treatment process of the sludge by the sludge treatment agent of the present invention, and the treatment time can be in the range of 6h-24 h. However, the inventive concept is not limited thereto.
In addition, when acid-soluble, reducible, oxidizable and other heavy metals which are directly or potentially toxic to the environment and are considered to be the most stable forms exist in the sludge, the heavy metals are mainly bound in a mineral crystal structure, have little bioavailability and are not easily released under common natural conditions. According to the concept of the invention, in order to reduce the influence of the heavy metal on the sludge recycling, the heavy metal can be passivated by combining attapulgite and layered double hydroxides. This is because: acid-soluble heavy metals are easy to coprecipitate with attapulgite and layered double metal oxides; the oxidizable heavy metal is easily adsorbed between layers by the layered double metal oxide on one hand, and is easily combined with the attapulgite to form a stable ternary compound mainly in the form of attapulgite-heavy metal-organic matter on the other hand; in addition, heavy metals in the sludge are easy to generate coordination reaction with hydroxyl of the layered double hydroxides and the attapulgite to generate hydroxyl complexes, so that the passivation treatment of the residual heavy metals in the sludge is completed.
Therefore, in order to passivate the heavy metals in the sludge, layered double hydroxides and attapulgite may be separately prepared according to the inventive concept.
The layered double hydroxide according to the present inventive concept may be prepared by the process for preparing the layered double hydroxide involved in the above-described supporting process. In other words, when the step of supporting the layered double hydroxide on the iron-carbon filler is performed, it is possible to add the iron-carbon filler to the reactor in which the layered double hydroxide is formed, and to support a part of the layered double hydroxide formed on the iron-carbon filler while forming the layered double hydroxide in the reactor. Thus, by performing the loading step, the layered double hydroxide formed may be partially loaded on the iron-carbon filler and partially formed separately from the iron-carbon filler, and the portion of the layered double hydroxide formed separately from the iron-carbon filler may be separated out after the loading step as a binding component with the attapulgite. However, the inventive concept is not limited to the formation of layered double hydroxides.
The attapulgite according to the inventive concept may be attapulgite known in the art. In other words, the attapulgite clay according to the present inventive concept may be an aqueous magnesium-rich silicate clay (mineralogically belonging to the sepiolite family) in the form of a layer chain. The theoretical molecular formula of the attapulgite can be Mg5Si8O20(OH)2(OH2)·4H2O, consisting of 2:1 layered silicate units, wherein each unit is formed by reversing SiO along a set of Si-O-Si bonds4The tetrahedra are connected to the next unit to form zeolite-like channels having dimensions of about 0.37nm by 0.64 nm. The chemical components of the attapulgite are MgO and SiO2、Al2O3Mainly contains a certain amount of MnO and TiO2、Fe2O3Etc. (the crystal structure of attapulgite is shown in fig. 3). The attapulgite crystal is needle-shaped, rod-shaped, fibrous or fibrous polymeric, has lattice displacement phenomenon in structure, and contains variable amount of Na+、Ca2+、Fe3+And Al3+. The attapulgite has special fiber structure, unusual colloid, adsorption and decolorization performances. The attapulgite has a developed pore structure and can be divided into a primary pore and a secondary pore according to the pore size: the 'zeolite' pore canal with the diameter of 0.37nm multiplied by 0.64nm formed by the magnesium aluminum silicate chain is a primary pore canal; the free spaces (mesopores) formed by the felt-like crystallites are secondary pores. Attapulgite contains 4 forms of water: water is absorbed on the surface; zeolite water with Si-O atoms in the channels (as "H2O' represents); crystal water (as "OH") located at the edge of the pore channel and coordinately bound to the edge octahedral cation2"represents); structural water (denoted as "OH") bound to the middle cations of the octahedral layer.
The attapulgite has a unique chain lamellar crystal structure and a large specific surface area, so that the attapulgite has a plurality of physicochemical properties such as ion exchange, suspension, thixotropy, adsorption, decoloration, catalysis, filling, colloid, rheological property, thermal stability, salt resistance and the like, and the most important properties comprise adsorptivity, catalysis and ion exchange.
According to the inventive concept, after the layered double hydroxide and the attapulgite are separately prepared, the layered double hydroxide and the attapulgite may be mixed and doped in a weight ratio of 1:9 to 9: 1. However, the inventive concept is not limited thereto.
After mixing and doping, the obtained mixture can be roasted to obtain higher activity. Here, the calcination temperature may be controlled within a range of 200 ℃ to 600 ℃, and the calcination time may be 2h to 6 h.
After calcination, the resulting material (hereinafter referred to as "passivating agent") can passivate the sludge, and here, the inventive concept does not limit the order of treatment of the sludge by the passivating agent and the sludge treatment agent. In other words, the sludge may be passivated by adding the passivating agent to the treated sludge after the sludge is treated with the sludge treating agent contemplated by the present invention. Alternatively, the sludge may be treated by adding the passivating agent to the sludge simultaneously with the sludge treatment agent. The inventive concept is not so limited.
In addition, in order to enable the passivating agent according to the present invention to effectively passivate sludge while taking economic benefits into consideration, the addition amount of the passivating agent and the time of the passivating treatment can be controlled. According to the concept of the invention, the adding amount of the passivating agent can be 1g-30g of passivating agent per kilogram of sludge, and the treatment time for treating the sludge by using the passivating agent can be 12h-36 h.
The method of treating sludge using the sludge treatment agent and the passivating agent according to the inventive concept is described above with reference to specific examples. The invention mainly improves the removal effect of the iron-carbon filler on heavy metals in sludge by loading the layered double-metal oxide on the surface of the iron-carbon filler, and meanwhile, the treated iron-carbon filler can also provide high-efficiency catalytic performance as a catalyst for catalytic oxidation of ozone. In addition, when a small amount of heavy metal ions still exist in the treated sludge, the heavy metal in the sludge can be passivated by the passivator obtained by roasting the layered double hydroxide and the attapulgite, so that the problem of efficiently, stably and safely treating the heavy metal in the sludge is solved.
In the following, specific examples of the inventive concept will be described in detail.
Example 1:
providing waste iron-carbon filler used in the iron-carbon micro-electrolysis treatment process, and crushing the waste iron-carbon filler to obtain the iron-carbon filler with the particle size of 8 mm.
Adding iron-carbon filler into a reactor for preparing Mg-Fe LDH, wherein the Mg-Fe LDH adopts a coprecipitation method; and after the reaction is finished, filtering to obtain Mg-Fe LDH and the iron-carbon filler loaded with the Mg-Fe LDH respectively.
And roasting the iron-carbon filler loaded with the Mg-Fe LDH in a muffle furnace at 220 ℃ for 2h to obtain the iron-carbon filler loaded with the Mg-Fe LDO as a sludge treatment agent.
Mixing 50 wt% of Mg-Fe LDH with 50 wt% of attapulgite, and roasting the mixture in a muffle furnace at 220 ℃ for 2.5h to obtain the passivator.
Taking 1kg of sludge with the water content of 72.3%, and adding 10g of sludge treatment agent into the sludge, wherein the content of main heavy metals in the sludge is as follows: 550.34mg/kg of Cu, 87.92mg/kg of Ni, 180.35mg/kg of Cr and 608.40mg/kg of Zn. The reaction is carried out for 20h under the condition of stirring. And after the reaction is finished, recovering the iron-carbon filler by using a magnetic separator, and roasting the recovered iron-carbon filler in a muffle furnace at 450 ℃ for 4 hours to obtain the ozone catalytic oxidation catalyst for treating the sewage. In addition, after the reaction is finished, 15g of passivating agent is added into the sludge and the reaction is carried out for 24 hours. The detection of the heavy metal content in the sludge after the reaction is as follows: the Cu content is 145.60mg/kg, the Ni content is 39.34mg/kg, the Cr content is 56.59mg/kg, and the Zn content is 203.48mg/kg, so that the requirement of sludge land utilization is met.
The obtained ozone catalytic oxidation catalyst is used for treating printing and dyeing wastewater, the COD of inlet water is 128mg/L, the reaction time is 60min, the COD of outlet water is 35mg/L, and the removal rate of COD reaches 72.6%.
Example 2:
providing waste iron-carbon filler used in the iron-carbon micro-electrolysis treatment process, and crushing the waste iron-carbon filler to obtain the iron-carbon filler with the particle size of 6 mm.
Adding iron-carbon filler into a reactor for preparing Ni-Al LDH, wherein the preparation method of the Ni-Al LDH is a hydrothermal synthesis method; and after the reaction is finished, filtering to obtain the Ni-Al LDH and the iron-carbon filler loaded with the Ni-Al LDH respectively.
And roasting the iron-carbon filler loaded with the Ni-Al LDH in a muffle furnace at 400 ℃ for 2h to obtain the iron-carbon filler loaded with the Ni-Al LDO as a sludge treatment agent.
Mixing 30 wt% of Ni-Al LDH with 70 wt% of attapulgite, and roasting the mixture in a muffle furnace at 220 ℃ for 2.5h to obtain the passivator.
Taking 1kg of sludge with the water content of 64.9%, and adding 20g of sludge treatment agent into the sludge, wherein the content of main heavy metals in the sludge is as follows: 636.86mg/kg of Cu, 89.32mg/kg of Ni, 200.32mg/kg of Cr and 742.32mg/kg of Zn are reacted for 20 hours under the condition of stirring, after the reaction is finished, the iron-carbon filler is recovered by a magnetic separator, and the recovered iron-carbon filler is roasted for 4 hours in a muffle furnace at 450 ℃ to obtain the ozone catalytic oxidation catalyst for treating sewage. In addition, after the reaction is finished, 15g of passivating agent is added into the sludge and the reaction is carried out for 24 hours. The detection of the heavy metal content in the sludge after the reaction is as follows: the Cu content is 184.75mg/kg, the Ni content is 32.54mg/kg, the Cr content is 60.42mg/kg, and the Zn content is 196.96mg/kg, so that the requirement of sludge land utilization is met.
The obtained ozone catalytic oxidation catalyst is used for treating papermaking wastewater, the COD of inlet water is 215mg/L, the reaction time is 60min, the COD of outlet water is 48mg/L, and the removal rate of the COD reaches 77.7%.
The present invention has been described above with reference to specific examples. The invention mainly adopts a heavy metal removal and passivation treatment route, firstly removes heavy metals in the sludge through the modified waste iron-carbon filler loaded layered double metal oxide, and then passivates the heavy metals in the sludge through a passivator obtained by roasting the layered double metal oxide and attapulgite, thereby realizing the problem of efficiently, stably and safely treating the heavy metals in the sludge.
Thus, the inventive concept enables, but is not limited to, the following advantageous effects:
resource utilization: the waste iron-carbon filler is used as a remover of heavy metals in the sludge, and the iron-carbon filler after the heavy metals are removed can be used for an ozone catalyst, so that the waste can be recycled, and the use cost of the technology of removing and stabilizing the heavy metals in the sludge and the use cost of the ozone catalytic oxidation technology are reduced;
the heavy metal removal and passivation effect is obvious: the layered bimetal oxide has unique structure memory effect and adsorption effect, can efficiently remove heavy metals in the sludge, and the treated sludge can meet the requirement of sludge land utilization.
The synergistic passivation effect is outstanding: by mixing and doping the layered double hydroxides and the attapulgite and carrying out roasting treatment, the method can play a role in synergistic passivation of heavy metals in the sludge, and ensure the stability of the sludge after passivation;
modification of waste iron-carbon filler: by loading the layered double-metal oxide on the surface of the iron-carbon filler, the removal effect of the layered double-metal oxide on the heavy metal in the sludge can be improved, and the catalytic performance of the layered double-metal oxide as an ozone catalyst can be improved.
Claims (10)
1. A method for preparing a sludge treatment agent, comprising the steps of:
providing an iron-carbon filler;
loading a layered double hydroxide on the iron-carbon filler;
and carrying out first roasting on the iron-carbon filler loaded with the layered double hydroxide to obtain the sludge treatment agent.
2. The method of claim 1, wherein the step of loading the layered double hydroxide on the iron-carbon filler comprises:
adding the iron-carbon filler to a reactor for preparing a layered double hydroxide;
preparing a layered double hydroxide in the reactor in which the iron-carbon filler is accommodated, thereby preparing the iron-carbon filler on which the layered double hydroxide is supported.
3. The method of claim 1, wherein the first firing has a firing temperature of 200 ℃ to 600 ℃ and a firing time of 2h to 6 h.
4. A method for treating sludge, characterized in that the method comprises subjecting sludge to a first treatment by using the sludge treatment agent produced by the method according to any one of claims 1 to 3.
5. The method of claim 4, wherein the method further comprises:
mixing the layered double hydroxide with attapulgite, carrying out secondary roasting on the mixture,
and carrying out second treatment on the sludge by using the product of the second roasting.
6. The method of claim 5, wherein the second roasting has a roasting temperature of 200 ℃ to 600 ℃ and a roasting time of 2h to 6 h.
7. The method of claim 5, wherein the mass ratio of the layered double hydroxide to the attapulgite in the mixture is in the range of 1:9 to 9: 1.
8. The method of claim 4, wherein after the first treatment, the iron-carbon filler in the sludge is separated, and the separated iron-carbon filler is subjected to a third roasting.
9. The method of claim 8, wherein the third firing is at a firing temperature of 300 ℃ to 800 ℃ for a firing time of 2h to 8 h.
10. The method of claim 4, wherein the water content of the sludge is 40 wt% to 80 wt%.
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