Red mud-based unfired ceramsite water purification filler with hierarchical pore structure and preparation method thereof
阅读说明：本技术 一种多级孔结构赤泥基免烧陶粒净水填料及其制备方法 (Red mud-based unfired ceramsite water purification filler with hierarchical pore structure and preparation method thereof ) 是由 张超 王文龙 吴长亮 王旭江 李敬伟 蒋稳 于 2020-12-31 设计创作，主要内容包括：本发明公开了一种多级孔结构赤泥基免烧陶粒净水填料及其制备方法,包括如下步骤：将烘干的赤泥、铝渣、脱硫石膏和石灰石尾矿按比例混合研磨后煅烧,得赤泥基胶凝材料熟料；赤泥基胶凝材料熟料与脱硫石膏按比例混合粉磨,得赤泥基胶凝材料；将赤泥基胶凝材料、粉煤灰、热-碱活化赤泥、Al粉、碱激发剂和硼砂按比例混合粉磨,过筛后挤压成型造粒；造粒后颗粒进行养护；养护后的颗粒浸泡于纳米过氧化钙水溶液中设定时间,烘干,制得赤泥基免烧陶粒净水填料。(The invention discloses a red mud-based unfired ceramsite water purification filler with a hierarchical pore structure and a preparation method thereof, wherein the preparation method comprises the following steps: mixing and grinding the dried red mud, the aluminum slag, the desulfurized gypsum and the limestone tailings according to a proportion, and then calcining to obtain red mud-based cementing material clinker; mixing and grinding the red mud-based cementing material clinker and the desulfurized gypsum in proportion to obtain a red mud-based cementing material; mixing and grinding the red mud-based cementing material, the fly ash, the heat-alkali activated red mud, the Al powder, the alkali activator and the borax according to a proportion, sieving, extruding and forming for granulation; maintaining the granulated particles; and soaking the cured particles in a nano calcium peroxide aqueous solution for a set time, and drying to obtain the red mud-based unfired ceramsite water purification filler.)
1. A preparation method of red mud-based unfired ceramsite water purification filler with a hierarchical pore structure is characterized by comprising the following steps of: the method comprises the following steps:
mixing and grinding the dried red mud, the aluminum slag, the desulfurized gypsum and the limestone tailings according to a proportion, and then calcining to obtain red mud-based cementing material clinker;
mixing and grinding the red mud-based cementing material clinker and the desulfurized gypsum in proportion to obtain a red mud-based cementing material;
mixing and grinding the red mud-based cementing material, the fly ash, the heat-alkali activated red mud, the Al powder, the alkali activator and the borax according to a proportion, sieving, adding water, and carrying out extrusion molding and granulation;
carrying out standard maintenance on the granulated particles;
and soaking the cured particles in a nano calcium peroxide aqueous solution for a set time, and drying to obtain the red mud-based unfired ceramsite water purification filler.
2. The preparation method of the red mud-based unfired ceramsite water purifying filler with the hierarchical pore structure according to claim 1 is characterized by comprising the following steps of: the mass ratio of the red mud, the aluminum slag, the desulfurized gypsum and the limestone tailings is 15-25: 25-30: 20-30: 25-35.
3. The preparation method of the red mud-based unfired ceramsite water purifying filler with the hierarchical pore structure according to claim 1 is characterized by comprising the following steps of: the calcining temperature is 1210-1230 ℃, and the calcining time is 1.5-2.5 h;
further, the calcination temperature was 1220 ℃ and the calcination time was 2 hours.
4. The preparation method of the red mud-based unfired ceramsite water purifying filler with the hierarchical pore structure according to claim 1 is characterized by comprising the following steps of: the preparation method of the heat-alkali activated red mud comprises the following steps: introducing high-temperature flue gas in the calcining process into a red mud complex containing NaOH, and carrying out heat-alkali activation treatment on the red mud;
further, the temperature of the high-temperature flue gas is 600-700 ℃;
furthermore, the mass percentage of NaOH in the red mud complexing body is 5-12%, preferably 10%.
5. The preparation method of the red mud-based unfired ceramsite water purifying filler with the hierarchical pore structure according to claim 1 is characterized by comprising the following steps of: the mass ratio of the red mud-based cementing material clinker to the desulfurized gypsum is 92-96: 4-8.
6. The preparation method of the red mud-based unfired ceramsite water purifying filler with the hierarchical pore structure according to claim 1 is characterized by comprising the following steps of: the mass ratio of the red mud-based cementing material to the fly ash to the heat-alkali activated red mud to the Al powder to the alkali activator to the borax is 5-10: 5-20: 60-90: 2-5: 3-5:3-6.
7. The preparation method of the red mud-based unfired ceramsite water purifying filler with the hierarchical pore structure according to claim 1 is characterized by comprising the following steps of: the concentration of the nano calcium peroxide water solution is 5-10%, and the mass percent is.
8. The preparation method of the red mud-based unfired ceramsite water purifying filler with the hierarchical pore structure according to claim 1 is characterized by comprising the following steps of: soaking the cured particles in nanometer calcium peroxide aqueous solution repeatedly for 8-15min each time.
9. The preparation method of the red mud-based unfired ceramsite water purifying filler with the hierarchical pore structure according to claim 8 is characterized by comprising the following steps of: the soaking times are 3-6 times.
10. The red mud-based unfired ceramsite water purification filler with the hierarchical pore structure is characterized in that: the red mud-based unfired ceramsite water purifying filler with the hierarchical pore structure as defined in any one of claims 1-9.
Technical Field
The invention relates to the technical field of water purification filler preparation, in particular to a red mud-based unfired ceramsite water purification filler with a hierarchical pore structure and a preparation method thereof.
Background
The information in this background section is only for enhancement of understanding of the general background of the invention 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.
At present, the existing preparation technology of the red mud-based porous ceramsite filter material is mostly prepared by a sintering route, and the existing technology for preparing the red mud-based non-sintered ceramsite filter material by a non-sintering route is mostly based on the adsorption characteristic brought by the porous property of the red mud. The raw materials for preparing the existing baking-free ceramsite filter material mostly adopt fly ash as a main raw material and ordinary silicon cement as a cementing material, and various additives are additionally used for improving the anti-crushing performance of the ceramsite.
The problems of the existing red mud-based porous ceramsite filter material preparation technology are as follows: (1) the existing red mud-based ceramsite filter material product is mostly prepared by adopting a sintering method, and the sintering method has the defects of high pollution and high energy consumption; (2) the existing red mud-based unfired ceramsite filter material product has low red mud doping amount due to low red mud activity; (3) the existing red mud-based unfired ceramsite filter material product has the defects of low porosity, poor adsorption performance, high cost and the like.
Disclosure of Invention
Aiming at the technical problems in the prior art, the invention provides a red mud-based unfired ceramsite water purification filler with a hierarchical pore structure and a preparation method thereof.
To solve the above technical problem, one or more of the following embodiments of the present invention provide the following technical solutions:
in a first aspect, the invention provides a preparation method of a red mud-based unfired ceramsite water purification filler with a hierarchical pore structure, which comprises the following steps:
mixing and grinding the dried red mud, the aluminum slag, the desulfurized gypsum and the limestone tailings according to a proportion, and then calcining to obtain red mud-based cementing material clinker;
mixing and grinding the red mud-based cementing material clinker and the desulfurized gypsum in proportion to obtain a red mud-based cementing material;
mixing and grinding the red mud-based cementing material, the fly ash, the heat-alkali activated red mud, the Al powder, the alkali activator and the borax according to a proportion, sieving, extruding and granulating to obtain a red mud-based porous ceramsite product;
performing standard maintenance on the red mud-based porous ceramsite product (the temperature is 25 ℃, and the humidity is 99%);
and soaking the cured red mud-based porous ceramsite product in a nano calcium peroxide aqueous solution for a set time, and drying to obtain the red mud-based unfired ceramsite water purification filler.
In a second aspect, the invention provides a red mud-based unfired ceramsite water purification filler with a hierarchical pore structure, which is prepared by a preparation method of the red mud-based unfired ceramsite water purification filler with the hierarchical pore structure.
Compared with the prior art, the above embodiment of the invention has the following beneficial effects:
the invention takes solid wastes as main raw materials, firstly prepares the red mud-based cementing material by utilizing the red mud, carries out heat-alkali activation on the red mud by utilizing the waste heat generated in the preparation process, and then prepares the high-strength unfired ceramsite filter material product by taking the red mud cementing material as a cementing agent and doping the red mud in high proportion, thereby realizing the comprehensive utilization of the red mud and leading the utilization rate of the red mud to reach more than 70 percent.
The invention realizes the formation of the multi-level pore structure of the non-sintered ceramsite filler by adding the foaming agent (Al powder) and combining the porous structure characteristics of the red mud, the porosity reaches 40-50 percent, and the adsorbability of the ceramsite filter material is improved.
The red mud-based cementing material is a low-alkalinity cementing material, and minerals such as ettringite, sodium aluminosilicate geopolymer, calcium silicate hydrate and the like formed by combining heat-alkali activated red mud with the red mud-based cementing material and fly ash can realize Na+Curing at 70-80%, reducing alkalinity of filter material, improving biocompatibility, improving filler strength, and increasing its crushing resistance.
The preparation process of the invention relates to waste heat recovery, and in the process of preparing the red mud-based cementing material from the red mud, the waste heat of a kiln is utilized to complete the heat-alkali activation of the red mud, thereby improving the strength performance of the red mud-based ceramsite, reducing the breakage rate, and being green, energy-saving and environment-friendly.
The bulk density of the red mud-based unfired lightweight aggregate product prepared by the invention is 710-880Kg/m3The cylinder pressure strength is 4-6MPa, the porosity is 40-50%, the porosity is 48-55%, the average pore diameter is 300-500nm, and Na2The content of O is less than 1 percent.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.
FIG. 1 is a route diagram for preparing a red mud-based unfired ceramsite water purification filler with a hierarchical pore structure in an embodiment of the invention;
FIG. 2 is a cross-sectional view of an optical microscope of the red mud-based ceramsite prepared in example 1 of the present invention;
FIG. 3 is a pore size distribution diagram of the red mud-based unfired ceramsite prepared in example 1 of the present invention;
FIG. 4 is an SEM photograph of red mud in example 1 of the present invention;
fig. 5 is an SEM image of the red mud-based ceramsite prepared in example 1 of the present invention;
FIG. 6 shows the ammonia nitrogen removal in the reactor of example 1 of the present invention.
Detailed Description
It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. 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 to which this invention belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
In a first aspect, the invention provides a preparation method of a red mud-based unfired ceramsite water purification filler with a hierarchical pore structure, which comprises the following steps:
mixing and grinding the dried red mud, the aluminum slag, the desulfurized gypsum and the limestone tailings according to a proportion, and then calcining to obtain red mud-based cementing material clinker;
mixing and grinding the red mud-based cementing material clinker and the desulfurized gypsum in proportion to obtain a red mud-based cementing material;
mixing and grinding the red mud-based cementing material, the fly ash, the heat-alkali activated red mud, the Al powder, the alkali activator and the borax according to a proportion, sieving, extruding and granulating to obtain a red mud-based porous ceramsite product;
performing standard maintenance on the red mud-based porous ceramsite product (the temperature is 25 ℃, and the humidity is 99%);
and soaking the cured red mud-based porous ceramsite product in a nano calcium peroxide aqueous solution for a set time, and drying to obtain the red mud-based unfired ceramsite water purification filler.
The fly ash can play a role of micro aggregate to enable the lightweight aggregate to be more compact, and the strength of the ceramsite can be improved while the density is reduced by properly adding the fly ash, so that the crushing resistance of the ceramsite is improved. In addition, the fly ash is rich in active silicon-aluminum components, has alkali-activated activity, can form compact geopolymer gelled materials such as sodium aluminosilicate/calcium aluminosilicate and the like under the action of the red mud and NaOH, and can realize effective Na + solidification while increasing the strength of the ceramsite, thereby reducing the alkalinity of the ceramsite filter material and improving the biocompatibility.
The Al powder can generate hydrogen in an alkaline solution as a solid foaming agent, so that the foaming and pore-forming of the red mud-based ceramsite are realized.
Thermal-alkaline activation of red mud: according to the invention, the red mud is used as Bayer process red mud, and because the active ingredients such as Si, Al and the like which can be dissolved out are basically and completely dissolved out, and the rest Si and Al ingredients are difficult to dissolve out, the red mud is subjected to heat-alkali activation by using the waste heat in the preparation process of the red mud-based cementing material, so that the alkali-activated activity of the red mud is improved, and the cementing property of the red mud is improved by matching with the fly ash and NaOH.
NaOH used as an alkali environment regulator and an alkali activator (sodium silicate or potassium hydroxide can also be used) not only provides an alkaline environment for the Al powder foaming agent, but also can activate the gelling activity of the red mud and the fly ash.
The borax serving as a foam stabilizer adjusts the structure of foaming pores and has the functions of foam stabilization and foam preservation.
The nano calcium peroxide is a biological affinity agent and can provide oxygen for microorganisms cultured in the ceramsite filler, so that the biological affinity of the water purification filler is improved.
In some embodiments, the mass ratio of the red mud, the aluminum slag, the desulfurized gypsum and the limestone tailings is 15-25: 25-30: 20-30: 25-35.
In some embodiments, the temperature of the calcination is 1210-1230 ℃, and the calcination time is 1.5-2.5 h;
further, the calcination temperature was 1220 ℃ and the calcination time was 2 hours.
In some embodiments, the thermal-alkali activated red mud is prepared by: introducing high-temperature flue gas in the preparation and calcination process of the red mud-based cementing material clinker into a red mud complex containing NaOH, and carrying out heat-alkali activation treatment on the red mud.
Further, the temperature of the high-temperature flue gas is 600-700 ℃.
Furthermore, the mass percentage of NaOH in the red mud complexing body is 5-12%, preferably 10%.
In some embodiments, the mass ratio of the red mud-based cementitious material clinker to the desulfurized gypsum is 92-96: 4-8.
In some embodiments, the mass ratio of the red mud-based cementitious material, the fly ash, the hot-alkali activated red mud, the alkali activator, the Al powder and the borax is 5-10: 5-20: 60-90: 3-5: 2-5: 3-6.
In some embodiments, the water usage amount is controlled as water to mix at 10-20: 80-90.
In some embodiments, the concentration of the nano calcium peroxide aqueous solution is 5-10%, and% is mass percent.
Further, soaking the cured particles in a nano calcium peroxide aqueous solution repeatedly for 8-15min each time.
Furthermore, the soaking times are 3-6 times.
In a second aspect, the invention provides a red mud-based unfired ceramsite water purification filler with a hierarchical pore structure, which is prepared by a preparation method of the red mud-based unfired ceramsite water purification filler with the hierarchical pore structure.
Example 1
As shown in figure 1, the red mud-based cementing material is prepared by the following steps of (1) drying red mud, aluminum slag, desulfurized gypsum and tailings for later use; (2) respectively taking 20 parts of red mud; 25 parts of limestone tailings; 30 parts of desulfurized gypsum; 25 parts of aluminum slag, namely grinding and uniformly mixing the red mud with limestone tailings, the aluminum slag and the desulfurized gypsum, and calcining the mixture to prepare the red mud-based cementing material clinker, wherein the calcining temperature is 1220 ℃ and the calcining time is 2 hours. Introducing calcination flue gas (600-700 ℃) into a 10:90 sodium hydroxide red mud mixture to prepare heat-alkali activated red mud, wherein the red mud-based cementing material clinker comprises the following components in parts by mass: desulfurized gypsum 95: 5, uniformly mixing and grinding to obtain the red mud-based cementing material.
The red mud-based ceramsite comprises the following preparation steps: (1) counting according to mass fraction, uniformly mixing and grinding 10 parts of red mud-based cementing material, 20 parts of fly ash, 5 parts of aluminum powder, 5 parts of borax, 3 parts of NaOH and 57 parts of hot-alkali activated red mud, and sieving with a 150-mesh sieve; (2) adding water into the mixture, stirring, adding water until the mixture is held by hand to be agglomerated, slightly soaking the surface with water, wherein the water consumption is 15%, and putting the mixed blank into an extrusion type granulator for granulation and molding; (3) maintaining the red mud-based ceramsite for 7 days at normal temperature and pressure for later use; (4) and soaking the prepared red mud-based unfired ceramsite in a nano calcium peroxide aqueous solution with the mass fraction of 5% for 10min, repeatedly soaking for 5 times, and drying at 50 ℃ to obtain the red mud-based unfired ceramsite water purification filler.
As shown in fig. 2, 3 and 5, the prepared red mud-based ceramsite has the following properties: bulk density of 710kg/m3Cylinder strength of 5MPa, porosity of 49.8%, porosity of 53%, averageThe pore diameter is 488nm, Na2O < 1%, and the reactor ammonia nitrogen removal rate is 65%, as shown in FIG. 6.
The beneficial effect of the red mud-based unfired ceramsite water purification filler is to develop the water purification efficiency of the BAF reactor. In the experiment, the self-made red mud-based unfired ceramsite water purification filler and the traditional sintered ceramsite are placed in a BAF reactor to evaluate the water purification efficiency of different ceramsite reactors, COD, pH and microbial biomass of the reactors in a film forming period are respectively collected, and suspended matter and ammonia nitrogen indexes are measured in a normal operation period. BAF reactor operating parameters were: gas-water ratio: 7-10:1, the filtration speed is 0.2m/h, the hydraulic retention time is 5h, wherein the ammonia nitrogen index analysis method adopts a spectrophotometry method, and the sampling frequency is once every two days in a normal operation period.
The traditional ceramsite is commercial fly ash sintered ceramsite with the bulk density of 800-900Kg/m3And the porosity is 40-50%.
Example 2
The red mud-based cementing material is prepared by the following steps of (1) drying red mud, aluminum slag, desulfurized gypsum and tailings for later use; (2) respectively taking 20 parts of red mud; 25 parts of limestone tailings; 30 parts of desulfurized gypsum; 25 parts of aluminum slag, namely grinding and uniformly mixing the red mud with limestone tailings, the aluminum slag and the desulfurized gypsum, and calcining the mixture to prepare the red mud-based cementing material clinker, wherein the calcining temperature is 1220 ℃ and the calcining time is 2 hours. Introducing calcination flue gas (600-700 ℃) into a 5:95 sodium hydroxide red mud mixture to prepare the heat-alkali activated red mud, wherein the red mud-based cementing material clinker comprises the following components in parts by mass: desulfurized gypsum 95: 5, uniformly mixing and grinding to obtain the red mud-based cementing material.
The red mud-based ceramsite is prepared by the following steps: (1) counting according to mass fraction, uniformly mixing and grinding 10 parts of red mud-based cementing material, 10 parts of fly ash, 2 parts of aluminum powder, 3 parts of borax, 4 parts of NaOH and 75 parts of hot-alkali activated red mud, and sieving with a 150-mesh sieve; (2) adding water into the mixture, stirring, adding water, grasping with hands, and slightly soaking with water on the surface, wherein the water consumption is 20%, and placing the mixed blank into an extrusion type granulator for granulation and molding; (3) maintaining the red mud-based non-fired ceramsite for 7 days at normal temperature and pressure for later use; (4) and soaking the prepared red mud-based unfired ceramsite in a nano calcium peroxide aqueous solution with the mass fraction of 5% for 10min, repeatedly soaking for 5 times, and drying at 50 ℃ to obtain the red mud-based unfired ceramsite water purification filler.
The prepared red mud-based ceramsite has the following properties: bulk density of 800kg/m3Cylinder pressure 4.5Mpa, porosity 41.2%, porosity 45%, average pore diameter 322nm, Na2O is less than 1 percent, and the ammonia nitrogen removal rate of the reactor is 51 percent.
Comparative example 1
Compared with the example 1, the heat-alkali activated red mud in the example 1 is replaced by the common dried red mud, and the rest is the same as the example 1.
The prepared red mud-based ceramsite has the following properties: bulk density of 800kg/m3Cylinder pressure of 3.5MPa, porosity of 39.6%, porosity of 45%, average pore diameter of 386nm and Na2O is less than 2 percent, and the ammonia nitrogen removal rate of the reactor is 60 percent.
Comparative example 2
The Al powder in example 1 was omitted as compared with example 1, and the rest was the same as example 1.
The prepared red mud-based ceramsite has the following properties: bulk density 1030kg/m3Cylinder pressure of 7.5MPa, porosity of 28.5%, porosity of 33%, average pore diameter of 86nm, and Na2O is less than 1 percent, and the ammonia nitrogen removal rate of the reactor is 45 percent.
Comparative example 3
Compared with the example 1, the step (4) of the red mud-based ceramsite preparation method in the example 1 is omitted, and the rest is the same as the example 1.
The prepared red mud-based ceramsite has the following properties: bulk density of 710kg/m3Cylinder pressure of 5MPa, porosity of 49.8%, porosity of 53%, average pore diameter of 488nm, Na2O is less than 1 percent, and the ammonia nitrogen removal rate of the reactor is 43 percent.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.