CN113522222B - Preparation method of iron-modified red mud-based magnetic adsorbent and application of iron-modified red mud-based magnetic adsorbent in composite heavy metal wastewater - Google Patents
Preparation method of iron-modified red mud-based magnetic adsorbent and application of iron-modified red mud-based magnetic adsorbent in composite heavy metal wastewater Download PDFInfo
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- CN113522222B CN113522222B CN202110961384.3A CN202110961384A CN113522222B CN 113522222 B CN113522222 B CN 113522222B CN 202110961384 A CN202110961384 A CN 202110961384A CN 113522222 B CN113522222 B CN 113522222B
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- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
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Abstract
The invention discloses a preparation method of an iron modified red mud-based magnetic adsorbent and application of the iron modified red mud-based magnetic adsorbent in composite heavy metal wastewater, which comprises the following steps: 1) pretreatment: drying the red mud, grinding and sieving to obtain the pretreated red mud; crushing and sieving the straws to obtain pretreated straws; 2) and (3) freeze drying: mixing the pretreated red mud and straw, and adding FeCl3After the solution is uniformly dispersed by ultrasonic waves, carrying out freeze drying to obtain a mixture; 3) and (3) pyrolysis treatment: and (3) placing the mixture in a muffle furnace, performing high-temperature pyrolysis, and cooling the mixture to room temperature along with the furnace after pyrolysis is finished to obtain the iron-modified red mud-based magnetic adsorbent. The invention is based on the strategy of treating waste by waste, adopts a simple method, does not need to carry out acid pretreatment on red mud, modifies the solid waste red mud into a strongly-magnetic adsorbing material low-cost adsorbent, realizes the synchronous removal of multi-metal in the wastewater through the surface complexation and chemical adsorption, and has good adsorbability and regenerability.
Description
Technical Field
The invention belongs to the technical field of industrial solid waste recycling and water treatment, and particularly relates to a preparation method of an iron modified red mud-based magnetic adsorbent and application of the iron modified red mud-based magnetic adsorbent in composite heavy metal wastewater.
Background
The rapid development of society and the industrial level are continuously improved, but with the development of various environmental problems, especially the current situation of heavy metal pollution is more and more severe, and the removal of heavy metal pollutants including Pb, Cd, Cu, As and their compounds has become a difficult problem to be solved urgently. The adsorption method is a common method for removing heavy metals in industrial wastewater, and the removal effect of the adsorption method is inseparable from that of the used adsorption material. The excellent adsorbing material needs to have the characteristics of low cost, large adsorption capacity, easy regeneration and the like.
Although red mud is a waste generated in the industrial process of alumina, the comprehensive utilization of red mud is a research hotspot in the environmental field. At present, red mud is utilized to prepare electro-Fenton catalytic materials, pollution remediation materials, heavy metal adsorbents and other functional materials. However, due to the high alkalinity of the red mud, the heavy metal adsorbents prepared by the patents such as CN109107524B, CN110721655A and CN109675527A perform acid neutralization treatment on the red mud, which not only has higher requirements on equipment, but also has the problem of secondary pollution of waste liquid. Therefore, a simple and efficient red mud modification technology is developed, the efficient adsorption of heavy metals is realized, and the method has very important significance for the reutilization of the red mud.
Disclosure of Invention
The invention aims to provide a preparation method of an iron modified red mud-based magnetic adsorbent and application of the iron modified red mud-based magnetic adsorbent in composite heavy metal wastewater; the method successfully prepares the high-Fe magnetic iron with good magnetic property and high Fe content by using industrial solid waste red mud and agricultural waste straws as raw materials, using ferric trichloride as an iron source and using freeze drying and high-temperature pyrolysis methods3O4Iron-modified red mud-based magnetic adsorbent with high content.
The preparation method of the iron modified red mud-based magnetic adsorbent comprises the following steps:
1) pretreatment: drying the red mud, grinding and sieving to obtain the pretreated red mud; crushing and sieving the straws to obtain pretreated straws;
2) and (3) freeze drying: mixing the red mud pretreated in the step 1) with strawsMixing, then adding FeCl3After the solution is uniformly dispersed by ultrasonic waves, freeze-drying the solution to obtain a mixture;
3) pyrolysis treatment: uniformly grinding the mixture obtained in the step 2), putting the mixture into a muffle furnace, performing high-temperature pyrolysis, and cooling to room temperature after pyrolysis is finished to obtain the iron-modified red mud-based magnetic adsorbent.
In the step 1), the red mud is sintering process red mud; grinding the red mud, and sieving the ground red mud by a 100-mesh sieve; after the straws are crushed, the straws are sieved by a 70-mesh sieve.
In the step 2), the mass ratio of the straw to the red mud is 1 (3-5), and FeCl3The concentration of the solution is 1-8 gL-1(ii) a 5ml of LFeCl is added into the mixture of 5.0g of straws and red mud3A solution; the freeze drying is that the mixture is firstly frozen in an ultra-low temperature refrigerator at the temperature of-90 to-70 ℃ for 6 hours and then is put into a freeze drying instrument for drying for 40 to 60 hours; preferably, the mass ratio of the straws to the red mud is 1: 4; the freezing temperature is-80 deg.C, the freezing time is 6h, and the freeze-drying time is 48 h.
In the step 3), the high-temperature pyrolysis specifically comprises the following steps: at 10 ℃ for min-1The temperature is raised to 500-700 ℃ at the speed, and the temperature is kept for 1.5-2.5 h at the temperature. Preferably, the temperature of pyrolysis is raised to 600 ℃ and kept for 2 h.
The iron-modified red mud-based magnetic adsorbent is prepared according to the preparation method of the adsorbent.
The iron-modified red mud-based magnetic adsorbent is applied to the composite heavy metal wastewater.
The mechanism analysis of the invention is as follows:
the red mud and the straw are used as raw materials, and FeCl is added3The pyrolysis modification can realize that: (1) FeCl3Fe in solution3+OH dissolved from red mud-、CO3 2-Precipitating alkaline anions to neutralize alkaline components in the red mud and generate an iron-rich component layer on the surfaces of the red mud and the straws; (2) FeCl in the pyrolysis process3Decomposition to Fe3O4The magnetic components are equal, so that the magnetization intensity of the adsorbent is increased; (3) fe precipitated and adsorbed on the surfaces of red mud and straw3+In the presence of heatA great deal of Fe is generated by reduction in the solution process2+Component (B) Fe2+As active adsorption sites, the active adsorption sites can enhance the activity on Pb through the action of reduction, ion exchange, chemical coordination and the like2+And Cd2+The adsorption capacity of the ions not only improves the number of active adsorption sites, but also enhances the adsorption capacity of the active sites, thereby improving the adsorption capacity to Pb2+/Cd2+Adsorption effect of cationic composite heavy metal.
The invention has the beneficial technical effects that: the invention is based on the strategy of treating waste by waste, adopts a simple method, does not need to carry out acid pretreatment on red mud, modifies the solid waste red mud into a strongly-magnetic adsorbing material low-cost adsorbent, realizes the synchronous removal of multi-metal in the wastewater through the surface complexation and chemical adsorption, and has good adsorbability and regenerability.
Drawings
Fig. 1 is a flow chart of the preparation of an iron-modified red mud-based magnetic adsorbent;
FIG. 2 is a scanning electron micrograph of the 0.04-Fe-S-BR adsorbent prepared in example 1;
FIG. 3 is a scanning electron micrograph of the S-BR adsorbent prepared in example 1;
FIG. 4 shows the results of EDX analysis of the 0.04-Fe-S-BR adsorbent prepared in example 1;
fig. 5 is an X-ray diffraction pattern of the iron-modified red mud-based magnetic adsorbent prepared in example 1;
fig. 6 is a hysteresis regression plot of the iron-modified red mud-based magnetic adsorbent prepared in example 1;
FIG. 7 is a scanning electron micrograph of the 0.04-Fe-S-BR adsorbent after the adsorption experiment in example 2;
FIG. 8 shows the results of EDX analysis of 0.04-Fe-S-BR adsorbent in example 2 after the adsorption experiment;
FIG. 9 shows the adsorption of 0.04-Fe-S-BR adsorbent for Pb after different cycle numbers in example 32+/Cd2+The removal rate of composite pollution.
Detailed Description
The following specific examples further illustrate the invention in detail.
Example 1 preparation of iron-modified red mud-based magnetic adsorbent
Example 1 was carried out according to the scheme for preparing an iron-modified red mud-based magnetic adsorbent shown in fig. 1.
1. Pretreatment: drying red mud of a sintering method of a red mud storage yard of Yuanping aluminum industry company in Shanxi province of China, grinding and sieving with a 100-mesh sieve. Crushing the straws, and sieving the crushed straws with a 70-mesh sieve;
2. and (3) freeze drying: mixing the pretreated red mud and straw according to the proportion of 1:4, and respectively adding 5mL of mixture with the concentration of 0, 4, 8 and 16gL into 5.0g of mixture-1FeCl of3The solutions are respectively marked as S-BR, 0.02-Fe-S-BR, 0.04-Fe-S-BR and 0.08-Fe-S-BR, and are dispersed uniformly by ultrasound. Freezing in an ultra-low temperature refrigerator at-80 deg.C for 6 hr, and drying in a freeze drying instrument for 48 hr. After freeze drying, grinding the mixture evenly;
3. pyrolysis treatment: putting the mixture into a muffle furnace for high-temperature pyrolysis at 10 deg.C for min-1Heating to 600 ℃, keeping the temperature at 600 ℃ for 2 hours, and naturally cooling to room temperature to obtain the iron-modified red mud-based magnetic adsorbent.
Table 1 shows the chemical composition of the red mud used in example 1
Table 2 shows the chemical composition of the straw used in example 1
SEM appearance characterization is carried out on the S-BR obtained by co-pyrolyzing the red mud and the straw which are not modified by iron in the example 1, and as shown in figure 2, large particles with rough surfaces exist and agglomeration phenomenon occurs. The iron-modified red mud-based magnetic adsorbent of 0.04-Fe-S-BR is characterized in that the particles are different in size, but obviously smaller and have more dense pores as shown in FIG. 3. As is clear from the EDX results in FIG. 4, 0.04-Fe-S-BR contains mainly O, Fe, Na, Al, Si, Ca, etc., and the iron content therein is as high as 14.71%.
Analyzing the phase structure by an X-ray diffractometer, as shown in FIG. 5, it is found that the products of red mud and straw pyrolysis have obvious Fe3O4(75-0449) and Fe2O3(87-1164) phase, wherein the iron modified 0.04-Fe-S-BR adsorbent has obvious characteristic peaks near 45.78 degrees and 53.77 degrees, and the characteristic peaks respectively correspond to (100) crystal faces and (42) crystal faces.
As can be seen from the hysteresis regression line chart of FIG. 6, as the content of iron salt increases, the saturation magnetization decreases, and the saturation magnetization of 0.02-Fe-S-BR is the highest and reaches 8.04emu g-1The saturation magnetizations of 0.04-Fe-S-BR and 0.08-Fe-S-BR were successively slightly decreased to 7.58emu g, respectively-1And 7.12emu g-1The S-BR without iron modification is only 6.53emu g-1。
Example 2 iron-modified Red-mud-based magnetic adsorbent for Pb2+/Cd2+Adsorption experiment of combined pollution
The iron-modified red mud-based magnetic adsorbent prepared in example 1 was used in an amount of 4gL-1Is added to Pb2+/Cd2+After 16h of adsorption experiment, the adsorption results of the composite contaminated solution are shown in table 3.
TABLE 3 iron salt addition on adsorption Effect
As can be seen from the table, for Pb2+/Cd2+The adsorption effect of the iron modified red mud-based magnetic adsorbent is shown to be 0.04-Fe-S-BR & gt 0.02-Fe-S-BR & gt 0.08-Fe-S-BR, and when the addition amount of iron salt is increased, the red mud, straws and FeCl are added3When the mass ratio of the Cd to the Cd is equal to 4:1:0.04, the effluent concentration of the wastewater conforms to the national comprehensive wastewater discharge standard GB 25466--1、Pb≤1mg L-1) However, the iron salt modified red mud is used for Pb2+The adsorption capacity of the catalyst is obviously higher than that of comparative Cd2+Mainly due to Pb2+/Cd2+Competition between adsorption sites, Pb2+Binding ability to adsorption sites than Cd2+Has strong binding capacity to the adsorption sites.
SEM morphology characterization was performed on 0.04-Fe-S-BR obtained after the adsorption experiment in example 2. The surface small porosity of the 0.04-Fe-S-BR after adsorption can be seen in FIG. 7, and the EDX spectrum result in FIG. 8 shows that the Pb and Cd contents of the surface of the adsorbed material are increased.
Example 3 iron-modified Red mud-based magnetic adsorbent for Pb2+/Cd2+Cyclic adsorption experiment of combined pollution
The 0.04-Fe-S-BR adsorbent obtained after the adsorption experiment in example 2 was collected, and 50mL of 0.1mol L was added-1And (3) taking out the NaOH solution after shaking for 2 hours in a shaking box, washing away redundant NaOH on the surface of the NaOH solution by deionized water, and drying the NaOH solution in an oven for later use. At 4gL-1Is added to Pb2+/Cd2+In the composite contaminated solution (initial concentration: Pb)2+Is 50mg g-1，Cd2+Is 25mg g-1) And carrying out an adsorption experiment for 16 h.
The corresponding adsorption results are shown in fig. 9. After 5 times of regeneration adsorption, it is used for treating Pb2+Still keeps higher adsorption effect which can reach 99.80 percent, and only reduces 2 percent compared with the first time, thereby meeting the national comprehensive sewage discharge standard. For Cd in compound heavy metal2+The removal rate of the cyclic adsorption of the previous 3 times is more than 90%, the adsorption effect is slightly deteriorated, and when the cyclic regeneration adsorption of the 4 th and 5 th times is carried out, the removal rates are reduced to 77.92% and 74.44%.
The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above-described embodiments. Modifications and variations that may occur to those skilled in the art without departing from the spirit and scope of the invention are to be considered as within the scope of the invention.
Claims (6)
1. A preparation method of an iron modified red mud-based magnetic adsorbent comprises the following steps:
1) pretreatment: drying the red mud, grinding and sieving to obtain the pretreated red mud; crushing and sieving the straws to obtain pretreated straws;
2) and (3) freeze drying: mixing the red mud pretreated in the step 1) with straws, and then adding FeCl3After the solution is uniformly dispersed by ultrasonic waves, freeze-drying the solution to obtain a mixture;
3) pyrolysis treatment: uniformly grinding the mixture obtained in the step 2), putting the mixture into a muffle furnace, performing high-temperature pyrolysis, and cooling to room temperature after pyrolysis to obtain the iron-modified red mud-based magnetic adsorbent;
in the step 2), the mass ratio of the straws to the red mud is 1 (3-5), and FeCl3The concentration of the solution is 1-8 gL-1(ii) a 5ml of LFeCl is added into the mixture of 5.0g of straws and red mud3A solution; the freeze drying is to freeze the mixture in an ultralow temperature refrigerator at-90 to-70 ℃ for 6 hours, and then put the mixture into a freeze drying instrument for drying for 40 to 60 hours;
in the step 3), the high-temperature pyrolysis specifically comprises the following steps: at 10 ℃ for min-1The temperature is raised to 500-700 ℃ at the speed, and the temperature is kept for 1.5-2.5 h at the temperature.
2. The preparation method of the iron-modified red mud-based magnetic adsorbent according to claim 1, wherein in the step 1), the red mud is a sintering process red mud; crushing the red mud, and sieving the crushed red mud by a 100-mesh sieve; crushing the straws, and sieving the crushed straws with a 70-mesh sieve.
3. The preparation method of the iron-modified red mud-based magnetic adsorbent according to claim 1, wherein the mass ratio of the straw to the red mud is 1: 4; the freezing temperature is-80 deg.C, the freezing time is 6h, and the freeze-drying time is 48 h.
4. The preparation method of the iron-modified red mud-based magnetic adsorbent according to claim 1, characterized by high-temperature pyrolysis: at 10 ℃ for min-1The temperature is raised to 600 ℃ at the rate of (1) and kept for 2 hours.
5. The iron-modified red mud-based magnetic adsorbent prepared by the preparation method according to any one of claims 1 to 4.
6. The application of the iron-modified red mud-based magnetic adsorbent according to claim 5 in adsorption of composite heavy metals in wastewater.
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