A calcium-silicon-aluminum three-phase composite system mineral adsorbent and a preparation method and application thereof

Abstract

The present application relates to a kind of calcium silicon aluminum three-phase composite system mineral adsorbent and its preparation method and application.Montmorillonite mineral is used as main raw material, and calcium-based mineral is used as auxiliary material, and after being crushed and ground, montmorillonite powder and calcium-based mineral powder are obtained;After stirring and uniformly dispersing montmorillonite powder and calcium-based mineral powder in water, mixed suspension is obtained;Composite suspension is obtained by hydrothermal reaction of mixed suspension, and composite adsorbent is obtained after filtration and drying;After high-temperature calcination of composite adsorbent, the calcium silicon aluminum three-phase composite system mineral adsorbent is obtained after cooling.The calcium silicon aluminum three-phase composite system mineral adsorbent is used for capturing heavy metal vapor at high temperature in the process of solid waste incineration.Compared with prior art, the raw material source of the present application is wide, the production process is green and environmentally friendly, and the composite adsorbent integrates calcium, silicon and aluminum three active components, thereby solving the technical problems of low adsorption efficiency of adsorbent for heavy metal vapor and simultaneous removal of multiple heavy metal vapors in the process of solid waste incineration.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of heavy metal adsorbents in solid waste incineration flue gas, in particular to a calcium-silicon-aluminum three-phase composite system mineral adsorbent and its preparation method and application. BACKGROUND

[0002] Incineration is one of the most common treatment methods for waste reduction and resource utilization of solid waste such as garbage and sludge. However, the composition of solid waste is relatively complex, and the flue gas generated contains heavy metal pollutants such as lead (Pb), cadmium (Cd) and zinc (Zn), which limits the development of this technology. Due to the toxicity, persistence and bioaccumulation of these heavy metals, they can pose a serious threat to the ecological environment and human health, even at low emission concentrations.

[0003] Heavy metals can be converted into vapor form at high temperatures, and then enriched on fine particulate matter in the flue gas through homogeneous nucleation or heterogeneous condensation mechanisms. Among them, part of the semi-volatile heavy metals in particulate form can be removed by dust removal devices, but semi-volatile heavy metals enriched on fine particulate matter and in gaseous form will escape. In addition, during the incineration of sludge and municipal solid waste containing chlorine, chlorine will react with heavy metals to form low-boiling heavy metal chlorides, further exacerbating the volatilization of heavy metals. Currently, injecting adsorbents into the furnace is considered a promising heavy metal emission control technology, and its basic principle is that the adsorbents in the furnace capture or solidify heavy metal vapors through physical / chemical adsorption reactions before the toxic heavy metal vapors nucleate.

[0004] Currently, the main way to control heavy metal emissions in the solid waste incineration process is to add a certain heavy metal adsorbent. However, adsorbents are usually difficult to simultaneously achieve efficient capture of multiple heavy metal vapors, and excessive use of solid adsorbents can lead to increased ash and reduced combustion efficiency. Incineration is the main direction of solid waste resource utilization and energy utilization, so developing composite high-efficiency heavy metal adsorbents for solid waste incineration processes is a practical need. Finding clean, efficient, inexpensive and environmentally friendly adsorbents is a hot spot for domestic and foreign research on heavy metal control in solid waste incineration processes.

[0005] Chinese patent CN109304138A discloses a method for preparing a heavy metal adsorbent from aluminum-calcium powder reaction slag and regenerating the same. In view of the long synthesis time, complex synthesis method and high synthesis cost of existing heavy metal adsorbents, the aluminum-calcium powder reaction slag generated in the production of polyaluminum chloride from aluminum-calcium powder is used as raw material to prepare a heavy metal adsorbent by activating with sodium hydroxide. The heavy metal adsorbent has a porous structure and sufficient aluminum hydroxyl heavy metal adsorption active sites, thus having excellent heavy metal adsorption function. After the heavy metal ions in wastewater are adsorbed by the heavy metal adsorbent, hydrochloric acid solution can be used to desorb the adsorption slag to recover the heavy metal ions. The desorption slag obtained by desorption can be reactivated with sodium hydroxide solution to obtain a regenerated heavy metal adsorbent, which still has excellent heavy metal adsorption capacity. The heavy metal adsorbent disclosed in the patent mainly contains aluminum and calcium, but it is mainly used for adsorbing heavy metal ions in wastewater.

[0006] Chinese patent CN112156750A discloses a method for preparing a fly ash carrier heavy metal adsorbent. The method uses fly ash particles as adsorbent carriers, and uniformly solidifies kaolin, Fe and Ca powders on the surface of fly ash particles by physical mixing and high-temperature calcination to prepare the required composite adsorbent. However, the method requires a large number of mineral raw materials, and the physical mixing of various mineral powders during the preparation process can cause uneven distribution of active components in the composite adsorbent, which can further cause large differences in the adsorption effect of the prepared composite adsorbent on heavy metals, making it difficult to standardize large-scale production.

[0007] Traditional single mineral adsorbents have low heavy metal solidification efficiency, high comprehensive cost and difficulty in recycling, which limits the popularization of the technology. The simultaneous solidification of multiple types of heavy metals under solid waste incineration conditions is a major problem currently faced. SUMMARY

[0008] In view of the above defects or improvement needs of the prior art, the present application provides a calcium-silicon-aluminum three-phase composite system mineral adsorbent, a preparation method and application thereof.

[0009] The technical scheme provided by the present application uses montmorillonite powder as the main material of the composite adsorbent and selects calcium-based mineral powder as the auxiliary material. The calcium-silicon-aluminum composite adsorbent is prepared by using an ultrasonic-assisted dispersion-hydrothermal-calcination method. The production process is green and environmentally friendly, simple to operate, and does not require any chemical reagents, thereby avoiding secondary pollution during the production process. The composite adsorbent integrates multiple active components, thereby solving the problems of low heavy metal solidification efficiency and simultaneous solidification of multiple types of heavy metals.

[0010] The object of the present application can be achieved by the following technical solutions:

[0011] The present application first provides a preparation method of a calcium-silicon-aluminum three-phase composite system mineral adsorbent, which comprises the following steps:

[0012] S1: taking a montmorillonite mineral as a main raw material and a calcium-based mineral as an auxiliary material, and crushing and grinding to obtain montmorillonite powder and calcium-based mineral powder; stirring and dispersing the montmorillonite powder and the calcium-based mineral powder in water to obtain a mixed suspension;

[0013] S2: performing a hydrothermal reaction on the mixed suspension obtained in step S1 to obtain a composite suspension, and filtering and drying to obtain a composite adsorbent;

[0014] S3: performing high-temperature calcination on the composite adsorbent, and obtaining the calcium-silicon-aluminum three-phase composite system mineral adsorbent after cooling.

[0015] In an embodiment of the present application, the calcium-based mineral is selected from a combination of one or more of CaCO3, CaO or Ca(OH)2.

[0016] In an embodiment of the present application, the mass of the calcium-based mineral added is 10-30% of the total mass of the montmorillonite mineral and the calcium-based mineral.

[0017] In an embodiment of the present application, the method for stirring and dispersing the montmorillonite powder and the calcium-based mineral powder in water is: stirring in a magnetic stirrer and then performing ultrasonic-assisted dispersion.

[0018] In an embodiment of the present application, the conditions for the hydrothermal reaction are: a hydrothermal temperature of 80-160℃ and a hydrothermal reaction time of 1-3h.

[0019] In an embodiment of the present application, the conditions for the high-temperature calcination are: a calcination temperature of 600-800℃ and a calcination time of 10-30min.

[0020] The present application further provides a calcium-silicon-aluminum three-phase composite system mineral adsorbent prepared based on the above preparation method. The adsorbent is a mixture of montmorillonite, calcium oxide and various calcium silicates, and the main components are Al, Si, Ca and O. The montmorillonite is the main material of the composite adsorbent, and a series of calcium silicate crystals generated at high temperature are uniformly dispersed in the composite adsorbent.

[0021] The present application further provides an application of the calcium-silicon-aluminum three-phase composite system mineral adsorbent prepared based on the above preparation method. The calcium-silicon-aluminum three-phase composite system mineral adsorbent is used for capturing heavy metal vapors at high temperature in a solid waste incineration process.

[0022] In an embodiment of the present application, the heavy metal vapors include PbCl2, CdCl2 and ZnCl2, etc. in solid waste incineration flue gas.

[0023] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0024] The preparation method of the calcium-silicon-aluminum three-phase composite system mineral adsorbent of the present application uses montmorillonite as the main material, as the composite adsorbent skeleton, which can provide reaction sites for the capture of heavy metal chlorides such as PbCl2, CdCl2 and ZnCl2 in solid waste incineration flue gas, has good thermal stability, and solves the sintering problem of traditional adsorbents at high temperature in the furnace; calcium-based minerals are selected as auxiliary materials of the composite adsorbent, and the calcium-based components are dispersed into the silicon-aluminum-based components by the ultrasonic-assisted dispersion-hydrothermal-high temperature calcination method, to obtain the calcium-silicon-aluminum three-phase composite system mineral adsorbent; since the ultrasonic-assisted dispersion technology in liquid is used, the effect is better than that of direct solid-solid mixing, and therefore the active components Ca, Si and Al of the composite adsorbent are uniformly dispersed, and have higher reactivity with heavy metals.

[0025] The preparation method of the calcium-silicon-aluminum three-phase composite system mineral adsorbent of the present application adds calcium-based minerals as one of the active components, and the calcium-based minerals themselves have strong heavy metal vapor adsorption capacity, thereby enhancing the adsorption capacity for heavy metals; in addition, the presence of alkaline calcium-based minerals can reduce the influence of acid gases in solid waste incineration flue gas on the solidification of heavy metal vapors by the composite adsorbent.

[0026] The preparation method of the calcium-silicon-aluminum three-phase composite system mineral adsorbent of the present application selects montmorillonite and calcium-based minerals as the components of the composite adsorbent, combines the advantages of Ca, Si and Al three active components, and provides chemical adsorption reaction sites for various heavy metal vapors in solid waste incineration flue gas, thereby solving the problem of simultaneous removal of various heavy metals in the solid waste incineration process.

[0027] The preparation method of the calcium-silicon-aluminum three-phase composite system mineral adsorbent of the present application uses montmorillonite as the main material of the composite adsorbent and calcium-based minerals as the auxiliary material, which has abundant raw material sources and low cost; the preparation method is simple and green, and will not cause secondary pollution to the environment; the prepared composite adsorbent has high heavy metal adsorption efficiency, wide application range and strong anti-interference ability, and is suitable for industrialization promotion. BRIEF DESCRIPTION OF DRAWINGS

[0028] 1 is a flow chart of the preparation method of the calcium-silicon-aluminum three-phase composite system mineral adsorbent according to the preferred embodiment of the present application;

[0029] Figure 2 is a crystal structure diagram of the calcium-silicon-aluminum three-phase composite system mineral adsorbent according to the preferred embodiment of the present application;

[0030] Figure 3 is a micro-morphology diagram of the calcium-silicon-aluminum three-phase composite system mineral adsorbent according to the preferred embodiment of the present application;

[0031] Figure 4 The graph shows the synergistic adsorption efficiency of a calcium-silicon-aluminum three-phase composite mineral adsorbent and montmorillonite for multiple heavy metals in flue gas, constructed according to a preferred embodiment of the present invention. Detailed Implementation

[0032] To enable those skilled in the art to more clearly understand the purpose, technical solution, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, the technical features involved in the various embodiments of the invention described below can be combined with each other as long as they do not conflict with each other.

[0034] Figure 1 This is a flowchart illustrating the preparation of a calcium-silicon-aluminum three-phase composite mineral adsorbent according to a preferred embodiment of the present invention. The preparation method includes the following steps:

[0035] (1) Montmorillonite mineral is used as the main raw material and calcium-based mineral is used as the auxiliary material. Montmorillonite powder and calcium-based mineral powder are obtained after crushing and grinding. Montmorillonite powder and calcium-based mineral powder accounting for 10-30% of the total mass of montmorillonite mineral and calcium-based mineral are placed in deionized water and vigorously stirred in a magnetic stirrer. After uniform dispersion with ultrasonic assistance, a mixed suspension is obtained.

[0036] (2) The mixed suspension obtained above is placed in a hydrothermal reactor and hydrothermally heated at 80-160°C for 1-3 hours. After filtration and drying, the mixed adsorbent is obtained and calcined in a muffle furnace at 600-800°C for 10-30 minutes. After cooling, the desired calcium-silicon-aluminum three-phase composite mineral adsorbent is obtained.

[0037] The method utilizes montmorillonite as the main material, providing reaction sites for the solidification of heavy metals. With a silica-alumina mineral framework, it exhibits good thermal stability, solving the problem of sintering deactivation of traditional in-furnace additives under high-temperature conditions. By adding calcium-based minerals as one of the active components, these minerals possess strong heavy metal vapor adsorption capabilities. They also promote the eutectic melting effect between heavy metals and silica-alumina minerals and reduce the impact of acidic gases on the adsorbent's capture of heavy metal vapors. Furthermore, the presence of montmorillonite inhibits the agglomeration effect of calcium-based mineral particles at high temperatures.

[0038] In the above preparation process, ultrasonic-assisted dispersion facilitates the thorough mixing of calcium, silicon, and aluminum components in the adsorbent in water; hydrothermal treatment at 80–160℃ promotes the uniform binding of Ca, Si, and Al components in the composite adsorbent; and controlling the calcination temperature at 600–800℃ improves the reactivity of the composite adsorbent while avoiding excessively high temperatures that could lead to sintering and deactivation of the adsorbent.

[0039] The present invention discloses a method for preparing a calcium-silicon-aluminum three-phase composite mineral adsorbent. Montmorillonite is used as the main material, and calcium-based minerals are used as auxiliary materials. The calcium-based components are dispersed into the silicon-aluminum components through an ultrasonic-assisted dispersion-hydrothermal-high-temperature calcination method, resulting in a calcium-silicon-aluminum three-phase composite mineral adsorbent. The Ca, Si, and Al active components of the composite adsorbent are uniformly dispersed, exhibiting higher reactivity with heavy metals. The silicon-aluminum minerals serve as the framework of the composite adsorbent, exhibiting good thermal stability and solving the problem of sintering deactivation of traditional adsorbents at high furnace temperatures. By adding calcium-based minerals, the activity of the composite adsorbent in solidifying heavy metals is enhanced, while the impact of acidic gases in solid waste incineration flue gas on the solidification of heavy metals by the composite adsorbent is reduced. By selecting montmorillonite and calcium-based minerals as components of the composite adsorbent, the advantages of the three active components (Ca, Si, and Al) are combined, providing solidification reaction sites for multiple heavy metals in solid waste incineration flue gas and solving the problem of synergistic removal of multiple heavy metals during solid waste incineration.

[0040] The present invention discloses a method for preparing a calcium-silicon-aluminum three-phase composite mineral adsorbent. The main material of the composite adsorbent is montmorillonite, and the auxiliary material is calcium-based mineral. The raw materials are abundant and the cost is low. The method is simple, green and environmentally friendly, and will not cause secondary pollution to the environment. The prepared composite adsorbent has high heavy metal adsorption efficiency, wide applicability, strong anti-interference ability, and is suitable for industrial promotion.

[0041] The following specific embodiments will be used to better understand the heavy metal solidification performance of the calcium-silicon-aluminum three-phase composite mineral adsorbent of the present invention, specifically:

[0042] Example 1

[0043] A specific method for preparing a calcium-silicon-aluminum three-phase composite mineral adsorbent is provided, comprising the following steps:

[0044] (1) Montmorillonite is used as the main raw material and calcium carbonate is used as the auxiliary material. After crushing and grinding, montmorillonite and calcium carbonate powders are obtained. 8g of montmorillonite powder and 2g of calcium carbonate powder are placed in 200mL of deionized water and stirred for 2 hours. Ultrasonic dispersion is performed for 1 hour to obtain a calcium carbonate / montmorillonite mixed suspension.

[0045] (2) The calcium carbonate / montmorillonite mixed suspension obtained above was placed in a hydrothermal reactor and hydrothermally heated at 120°C for 2 hours. After filtration and drying, the mixed adsorbent was obtained. Then, it was transferred to a muffle furnace and calcined at 700°C for 10 minutes. After cooling, the desired calcium-silicon-aluminum three-phase composite mineral adsorbent was obtained.

[0046] Example 2

[0047] A specific method for preparing a calcium-silicon-aluminum three-phase composite mineral adsorbent is provided, comprising the following steps:

[0048] (1) Montmorillonite was used as the main raw material and calcium oxide as the auxiliary material. After crushing and grinding, montmorillonite and calcium oxide powder were obtained. 9g of montmorillonite powder and 1g of calcium oxide powder were placed in 200mL of deionized water and stirred for 2 hours. After ultrasonic dispersion for 1 hour, a calcium oxide / montmorillonite mixed suspension was obtained.

[0049] (2) The calcium oxide / montmorillonite mixed suspension obtained above was placed in a hydrothermal reactor and hydrothermally heated at 80°C for 1 hour. After filtration and drying, a mixed adsorbent was obtained. Then, it was transferred to a muffle furnace and calcined at 600°C for 20 minutes. After cooling, the desired calcium-silicon-aluminum three-phase composite mineral adsorbent was obtained.

[0050] Example 3

[0051] A specific method for preparing a calcium-silicon-aluminum three-phase composite mineral adsorbent is provided, comprising the following steps:

[0052] (1) Montmorillonite was used as the main raw material and calcium hydroxide as the auxiliary material. After crushing and grinding, montmorillonite and calcium hydroxide powder were obtained. 7g of montmorillonite powder and 3g of calcium hydroxide powder were placed in 200mL of deionized water and stirred for 2 hours. After ultrasonic dispersion for 1 hour, a calcium hydroxide / montmorillonite mixed suspension was obtained.

[0053] (2) The calcium hydroxide / montmorillonite mixed suspension obtained above was placed in a hydrothermal reactor and hydrothermally heated at 160°C for 3 hours. After filtration and drying, the mixed adsorbent was obtained. Then, it was transferred to a muffle furnace and calcined at 800°C for 10 minutes. After cooling, the desired calcium-silicon-aluminum three-phase composite mineral adsorbent was obtained.

[0054] To facilitate a further understanding of the technical solution and advantages of the calcium-silicon-aluminum three-phase composite mineral adsorbent of the present invention, the crystal structure and microstructure of the calcium-silicon-aluminum three-phase composite mineral adsorbent of the present invention were analyzed, and its co-adsorption performance for typical heavy metal chloride vapors was tested.

[0055] Crystal structure and microstructure analysis methods: A small amount of the composite adsorbent prepared according to this invention was taken, and the particle morphology of the composite adsorbent was observed using a scanning electron microscope. Heavy metal chloride vapor adsorption performance test: The heavy metal adsorbent experiment was conducted in a dual-temperature zone vertical tube furnace, with both the upper and lower temperature zones set to 800℃. The heavy metal sources were 20 mg each of PbCl2, CdCl2, and ZnCl2 powders. The heavy metal powders were placed in the upper temperature zone to generate heavy metal vapor, which was carried into the lower temperature zone adsorption zone by air. 0.6 g of calcium-silicon-aluminum composite mineral adsorbent was placed in the lower temperature zone to adsorb heavy metals, and the adsorption reaction time was 20 min. After the adsorption reaction, the content of heavy metals captured in the adsorbent was analyzed using an ICP-OES analyzer, and the adsorption efficiency was calculated.

[0056] The results are as follows:

[0057] Figure 2 This is the XRD pattern of the calcium-silicon-aluminum composite adsorbent prepared according to Example 1 of the present invention. Figure 2 It is known that the prepared calcium-silicon-aluminum composite adsorbent contains three effective components: Ca, Si, and Al. The silicon-aluminum based mineral framework can prevent the adsorbent from sintering and deactivating at high temperatures, and the addition of calcium-based components can synergistically adsorb various heavy metal vapors.

[0058] Figure 3 This describes the microstructure of the calcium-silicon-aluminum composite adsorbent prepared according to Example 1 of the present invention. For example... Figure 3 As shown, the prepared composite adsorbent has a rough surface and a large number of pore structures, which is conducive to the diffusion of gaseous heavy metals inside the adsorbent and can provide more active sites for the adsorption of heavy metal vapors.

[0059] Figure 4 This diagram shows the synergistic adsorption efficiency of the calcium-silicon-aluminum composite adsorbent prepared according to Example 1 of this invention and montmorillonite in simulated solid waste incineration flue gas for multiple heavy metal vapors. The results show that the prepared composite adsorbent has a superior synergistic capture capacity for multiple heavy metal vapors compared to montmorillonite, with adsorption efficiencies of 56%, 47%, and 26% for PbCl2, CdCl2, and ZnCl2 vapors in the incineration flue gas, respectively. The prepared calcium-silicon-aluminum composite adsorbent significantly reduces the release of heavy metal vapors in incineration flue gas. The heavy metal adsorption experiment results demonstrate that the calcium-silicon-aluminum composite adsorbent of this invention can synergistically solidify multiple heavy metal vapors in solid waste incineration flue gas.

[0060] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a calcium-silicon-aluminum three-phase composite mineral adsorbent, characterized in that, The method includes the following steps: S1: Montmorillonite mineral is used as the main raw material and calcium-based mineral as the auxiliary material. Montmorillonite powder and calcium-based mineral powder are obtained by crushing and grinding. The montmorillonite powder and calcium-based mineral powder are stirred and dispersed evenly in water to obtain a mixed suspension. S2: The mixed suspension obtained in step S1 is subjected to a hydrothermal reaction to obtain a composite suspension, which is then filtered and dried to obtain a composite adsorbent. S3: The composite adsorbent is calcined at high temperature and then cooled to obtain the calcium-silicon-aluminum three-phase composite mineral adsorbent. The mass of the calcium-based mineral added is 10-30% of the total mass of montmorillonite mineral and calcium-based mineral. The hydrothermal reaction conditions are: hydrothermal temperature of 80-160℃, hydrothermal reaction time of 1-3h, and high-temperature calcination conditions are: calcination temperature of 600-800℃, calcination time of 10-30min. Montmorillonite was used as the main material and served as the framework of the composite adsorbent to provide reaction sites for the capture of heavy metal chloride vapors in solid waste incineration flue gas. Calcium-based minerals were used as auxiliary materials for the composite adsorbent. The calcium-based components were dispersed into the silicon-aluminum-based components through an ultrasonic-assisted dispersion-hydrothermal-high-temperature calcination method to obtain a calcium-silicon-aluminum three-phase composite mineral adsorbent system.

2. The method for preparing a calcium-silicon-aluminum three-phase composite mineral adsorbent according to claim 1, characterized in that, The calcium-based mineral is selected from one or more combinations of CaCO3, CaO, or Ca(OH)2.

3. The method for preparing a calcium-silicon-aluminum three-phase composite mineral adsorbent according to claim 1, characterized in that, The method for stirring and dispersing montmorillonite powder and calcium-based mineral powder in water is as follows: after stirring in a magnetic stirrer, ultrasonic-assisted dispersion is used.

4. A calcium-silicon-aluminum three-phase composite mineral adsorbent prepared by the preparation method according to any one of claims 1-3.

5. The calcium-silicon-aluminum three-phase composite mineral adsorbent according to claim 4, characterized in that, The adsorbent is a mixture of montmorillonite, calcium oxide and various calcium aluminosilicates, with Al, Si, Ca and O as the main components. A series of calcium aluminosilicate crystals generated at high temperature are uniformly dispersed in the composite adsorbent.

6. The application of the calcium-silicon-aluminum three-phase composite mineral adsorbent according to claim 4 or 5, characterized in that, The calcium-silicon-aluminum three-phase composite mineral adsorbent is used to capture heavy metal vapors at high temperatures during solid waste incineration.

7. The application of the calcium-silicon-aluminum three-phase composite mineral adsorbent according to claim 6, characterized in that, The heavy metal vapors include PbCl2, CdCl2, and ZnCl2 in solid waste incineration flue gas.

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