A method for preparing spherical particle solid waste-based adsorbent from electrolytic manganese residue and chromium electroplating sludge and application thereof

Abstract

The present application relates to a kind of method for preparing solid waste-based granular adsorbent using chromium electroplating sludge and electrolytic manganese residue, by first crushing electrolytic manganese residue and chromium electroplating sludge, activated with acid solution, then mixed with a certain proportion of sodium bentonite, kaolin and zeolite, mixed evenly, then added biomass high temperature calcination for secondary activation, to obtain adsorbent precursor. The prepared powder precursor is mixed with chitosan to form granules, to obtain a solid waste-based adsorbent with strong adsorption and recyclability. The spherical granular adsorbent prepared by the present application has low preparation cost, simple operation, good adsorption effect, and good recycling effect. The adsorbent recovered after five adsorption processes still retains high adsorption, suitable for deep treatment of industrial wastewater containing heavy metals, and realizes resource utilization of industrial waste residue.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of adsorbent preparation, and particularly relates to a method for preparing spherical particle solid waste-based adsorbent by using electrolytic manganese residue and chromium electroplating sludge. BACKGROUND

[0002] China is a large country in production, consumption and export of electrolytic manganese, and the production capacity has exceeded 2.5 million tons, accounting for more than 98.5% of the world's manganese production. Electrolytic manganese residue is a high-moisture industrial solid waste produced in the process of electrolytic manganese production after manganese ore is leached in an acidic solution, and the annual output is 7-11 tons per ton of manganese. At present, the treatment method of electrolytic manganese residue is still open-air stacking, and the open-air stacking amount of electrolytic manganese residue in China has exceeded 120 million tons and is still increasing. Electrolytic manganese residue is an acidic residue, and during the stacking process, the acid leachate causes irreversible damage to surrounding buildings, environment and the like, occupies a large amount of land resources, has dust hazards and the like, and has a great impact on the ecological environment.

[0003] Electroplating sludge is flocculation and precipitation produced in the process of electroplating wastewater treatment, has the characteristics of high moisture content, easy accumulation, poor stability, easy transfer and the like, and its secondary environmental hazards are greater than those of electroplating wastewater. In the electroplating process, organic matters such as brightener and surfactant are often added, which makes the composition of electroplating sludge more complex and increases the difficulty of its treatment. Electroplating sludge contains Cr, Ni, Cu, Zn, Pb, Cd and other heavy metals, is listed as the seventeenth type of hazardous waste in the National Hazardous Waste List of China, and is also a recognized hazardous waste in the world. At present, the annual output of electroplating sludge exceeds 10 million tons. If it is not properly disposed of and is arbitrarily stacked, the heavy metals in it will migrate along the path of sludge-soil-crops-human body, not only polluting the environment and causing serious pollution to groundwater, but also directly or indirectly endangering human health. However, there is no efficient and reasonable treatment method for electroplating sludge at present, and how to harmlessly and resourcefully treat electroplating sludge has been a research hotspot in the relevant field.

[0004] At present, the commonly used adsorbents include resins, activated carbon, organic materials and the like, but there are problems of high price, difficult to reuse, complex subsequent treatment and the like, so the solid waste-based adsorbent has significant advantages. There are studies that prepare adsorbents from industrial solid wastes such as red mud, electrolytic manganese slag and fly ash, but there is a disadvantage of low adsorption efficiency. The patent CN109772259 proposes a method for treating heavy metals in electroplating wastewater by using electroplating sludge, which is simple to operate and has better adsorption effect than commercial adsorbents, but cannot be reused and has certain limitations in application environment, which is difficult to treat other heavy metal industrial wastewater. The patent CN113231007B discloses a method for preparing a heavy metal adsorbent from blast furnace slag, but only the waste utilization of blast furnace slag can be used, and the method cannot be used for electroplating sludge and electrolytic manganese slag with high ammonia nitrogen and manganese content, so it cannot effectively resourceize the electroplating sludge and electrolytic manganese slag.

[0005] Therefore, it is necessary to improve the adsorbent prepared from the electrolytic manganese slag and the electroplating sludge solid waste material or the preparation method, so as to maximize the comprehensive reuse of the solid waste, and also make the solid waste-based adsorbent more efficient, reusable and suitable for a wider range of applications. SUMMARY

[0006] In view of the problem that the adsorbent prepared from the electroplating sludge is in powder form and is not conducive to solid-liquid separation and recovery, the application provides a spherical particle solid waste-based adsorbent preparation method and application, which comprehensively utilizes chromium electroplating sludge and electrolytic manganese slag to prepare a spherical particle adsorbent. The prepared adsorbent has good adsorption effect, can be recycled and can be applied to the advanced treatment of industrial wastewater containing heavy metals.

[0007] To solve the above technical problems, the application provides a solid waste-based adsorbent preparation method and application, wherein the adsorbent is prepared from electrolytic manganese slag and chromium electroplating sludge as main raw materials. The application first crushes and mixes the electrolytic manganese slag and the chromium electroplating sludge, activates them with an acid solution, mixes them with sodium-based bentonite, kaolin and zeolite at a certain ratio, uniformly mixes them, adds biomass high-temperature calcination for secondary activation to obtain an adsorbent precursor, further mixes and granulates the adsorbent precursor with chitosan, and finally obtains a solid waste-based adsorbent with strong adsorption and recyclability.

[0008] Specifically, a method for preparing a solid waste-based particle adsorbent from chromium electroplating sludge and electrolytic manganese slag includes the following steps:

[0009] (1) separately ball milling, drying, sieving and reserving the electrolytic manganese slag, the chromium electroplating sludge, the kaolin and the sodium-based bentonite;

[0010] (2) mixing the screened electrolytic manganese residue and electroplating sludge obtained in step (1) uniformly, adding acid liquid for acid leaching treatment; filtering to obtain acid washing liquid and filter residue, drying the filter residue after washing to neutral to obtain acid-activated solid powder 1; combining the filtrate and washing liquid for reuse in the next batch of raw material acid washing activation;

[0011] (3) mixing the solid powder 1 obtained in step (2) with zeolite powder, screened kaolin in step (1), and sodium-based bentonite uniformly to obtain solid powder 2;

[0012] (4) mixing the solid powder 2 obtained in step (3) with biomass uniformly, calcining, and taking out after cooling to room temperature to obtain solid powder 3 by grinding;

[0013] (5) adding chitosan powder, binder, and distilled water to the solid powder 3 obtained in step (4) and mixing uniformly, granulating, drying, and sieving to obtain granular adsorbent.

[0014] Preferably, in step (1), the chromium electroplating sludge is flocculation precipitate generated during chemical treatment of electroplating wastewater, and the chromium content in the electroplating sludge is high because the plating species is chromium. The chromium content in the electroplating sludge of the present application is 40-60 wt%. The electrolytic manganese residue is solid waste residue generated during electrolytic manganese production using manganese carbonate as raw material, and the mineral composition mainly includes quartz and calcium sulfate dihydrate. The main chemical components are glassy oxides such as SiO2, Al2O3, CaO, MnO, and the content of SiO2, Al2O3, CaO, MnO, and SO3 accounts for 80-90 wt% of the total amount of electrolytic manganese residue, and the content of SO3 is higher than 20%.

[0015] In step (1), the screening is through a 100-200 mesh sieve, such as 100 mesh, 120 mesh, or 180 mesh.

[0016] In step (2), the mass ratio of electrolytic manganese residue to electroplating sludge is 1:(0.9-2), preferably 1:(1.2-2).

[0017] The solid waste electrolytic manganese residue and electroplating sludge are activated by acid and high-temperature reaction, and chromium in the electroplating sludge and iron, manganese, silicon, calcium, etc. in the electrolytic manganese residue generate spinel, thereby effectively solidifying heavy metals. Therefore, preferably, the mass of the electroplating sludge is higher than that of the electrolytic manganese residue.

[0018] The solid-liquid ratio of the mixture of electrolytic manganese residue and electroplating sludge to acid liquid is 1 g:(10-15) mL.

[0019] The acid liquid is a mixture of citric acid, water, and other carboxylic acids, wherein the concentration of citric acid is 0.1-0.15 mol / L, and the concentration of the other carboxylic acid is 0.05-0.1 mol / L. The other carboxylic acid is selected from one or a combination of two or more of acetic acid, oxalic acid, and benzoic acid.

[0020] The acid liquid has a pH value of 4.5-5.5, the acid leaching treatment temperature is room temperature, which can be 20-35 DEG C; the acid leaching treatment time is 10-15 h; and the stirring speed of the acid leaching treatment is 150-300 rpm.

[0021] The organic weak acid has certain reducibility, and the electrolytic manganese residue and electroplating sludge are activated by the acid liquid containing the organic weak acid, so that the heavy metals are resolved, and the chromium is reduced to a low valence state, which is beneficial to the subsequent high-temperature reaction to generate spinel structure, and realizes the stabilization and solidification of metal ions.

[0022] The inventor finds that the ternary carboxylic acid citric acid and other monovalent or divalent carboxylic acids in the composite acid system not only facilitate the control of the end point pH value of the acid leaching activation in the pH value change process of the system, but also promote the generation of low valence chromium, improve the reduction efficiency of chromium, and thus the acid leaching activation efficiency is higher, the metal ion resolution efficiency is higher, the adsorption performance of the adsorbent is improved, and the harm of secondary leaching of hexavalent chromium and other metal ions is reduced.

[0023] In step (3), the zeolite powder accounts for 5-15% of the total mass of the mixture of the electrolytic manganese residue and the electroplating sludge, the kaolin accounts for 8-12% of the total mass of the mixture of the electrolytic manganese residue and the electroplating sludge, and the sodium-based bentonite accounts for 8-12% of the total mass of the mixture of the electrolytic manganese residue and the electroplating sludge.

[0024] In step (4), the biomass is straw or walnut shell; and the mass ratio of the solid powder 2 to the biomass is (3-6):1.

[0025] The calcination is performed by using a muffle furnace, the preheating temperature is 280-320 DEG C, the heating rate is 3 DEG C / min-8 DEG C / min, the calcination temperature is 900-1000 DEG C, and the holding time is 30-60 min.

[0026] The particle size of the solid powder 3 is 100-150 meshes, such as 100 meshes, 120 meshes or 150 meshes.

[0027] After the acid leaching activation treatment, the porous material zeolite and the sodium-based bentonite are further added, and the biomass is secondarily activated, the oxygen-containing functional groups on the biomass are used, and the heavy metals are interactively reacted under the action of high-temperature calcination, so that the metal ions are solidified in the form of spinel phases such as MnCr2O4, FeCr2O4 and Ca3Cr2(SiO4)3, and the porous material with spinel as the "skeleton" is formed, and the structure of the adsorption material is loose and the pore structure is rich; in this process, the ammonia nitrogen in the electrolytic manganese residue is a pore-forming agent, and finally the porous material with more rich structure is obtained.

[0028] In step (5), the chitosan powder accounts for 2-5% of the total mass of the mixture of solid powder 3 and chitosan; the chitosan has a deacetylation degree of more than 80% and a viscosity of more than 0.8 Pa·s.

[0029] The binder is an activated carbon binder, and the amount of addition accounts for 0.5-2% of the total mass of the mixture of solid powder 3 and chitosan.

[0030] The present application further adds chitosan granulation, and the granular adsorbent is convenient to collect, and the addition of chitosan enhances the adsorption capacity of the adsorbent, and also prevents spinel phase agglomeration, and the adsorbent has good stability and is suitable for multiple recycling and reuse.

[0031] Preferably, the chitosan is a combination of two or more chitosans with different deacetylation degrees.

[0032] More preferably, two chitosans with a deacetylation degree of 80-90% and a deacetylation degree of more than 90% are combined, and the mass ratio of the chitosan with a deacetylation degree of 80-90% to the chitosan with a deacetylation degree of more than 90% is 1:(1-2).

[0033] The inventors have found that the higher the deacetylation degree, the higher the activity of chitosan, the protonation of amine groups increases the number of charged groups of chitosan in an acid solution, and the interaction with heavy metal ions is strong, so the adsorption rate is higher, and therefore the deacetylation degree is more than 80%. On the other hand, chitosans with different deacetylation degrees have more abundant structures, and chitosans with different molecular structures and spinels form various combination forms, so that the combination of the two is more compact, the effective adsorption area is increased, the adsorption efficiency is improved, and collection is facilitated.

[0034] In one embodiment of the present application, two chitosans with a deacetylation degree of 80% and a deacetylation degree of 95% are mixed in a mass ratio of 1:1.

[0035] In step (5), the granulation is performed by a granulator to form a material ball with a particle size of 2-3 mm; and the sieving is performed by passing through a 6-8 mesh sieve.

[0036] The drying method is not particularly limited, and a conventional drying method in the art can be used, such as oven drying or vacuum drying.

[0037] The technical principle and beneficial effects of the present application are as follows:

[0038] 1.The present application first activates electrolytic manganese residue and electroplating sludge with acid, in which process heavy metal ions are resolved. The composite weak organic acid also has reducing property, which reduces chromium to low valence state for later high temperature reaction to form spinel, and enhances the acid activation effect. Zeolite powder is a porous material, and sodium-based bentonite is a hydrous clay mineral mainly containing montmorillonite, which has swelling, binding, adsorbing, catalyzing, suspending and cation exchanging properties, and is beneficial to adsorbing heavy metal ions in manganese residue and sludge. The adsorbing material (zeolite and bentonite) is mixed with manganese residue and electroplating sludge powder and calcined at high temperature, with the help of secondary activation of biomass, not only facilitating the mutual reaction of heavy metals to be solidified in the form of spinel phases such as MnCr2O4, FeCr2O4 and Ca3Cr2(SiO4)3, but also making the adsorbent structure more loose. Furthermore, ammonia nitrogen in electrolytic manganese residue acts as a pore-forming agent, which not only improves the strength of the adsorbent in aqueous solution, but also ensures the adsorption effect, so as to obtain a porous material. Chitosan macromolecule has active hydroxyl and amino groups, strong heavy metal adsorption and chelation, and mixing with the above porous material improves the adsorption performance of the adsorbent and enables the adsorbent to be collected in granular form for reuse. The adsorbent still has strong adsorption after being used for five times. Meanwhile, the adsorbent has strong reusability, which may be because chitosan and spinel structure are combined to achieve effective modification, not only preventing spinel phase from agglomeration, but also enhancing the adsorption capacity of the adsorbent.

[0039] 2.The adsorbent of the present application first resolves heavy metal ions through acid activation, and then adds porous adsorbing material (zeolite and bentonite, etc.), which is secondarily activated by oxygen-containing biomass, and high-temperature calcination makes the heavy metals in solid waste form a porous adsorbing material with spinel main body "skeleton" structure. Furthermore, the active functional groups in chitosan improve the metal chelation of the adsorbent and prevent the spinel "skeleton" in the adsorbent from agglomeration or collapse. The adsorbent is beneficial to recycling and has long service life. The whole process is an organic whole, and the modification process is closely coordinated. The final adsorbent has strong adsorption capacity, high utilization rate of solid waste, and no secondary pollution.

[0040] 3.The present application further optimizes the process details. The composite weak acid system is used for the first time, which improves the reduction efficiency of chromium and the acid leaching activation effect. The compounded chitosan improves the close degree and interaction of the metal ions to be adsorbed and spinel phase, further optimizes the adsorption capacity of the adsorbent for metal ions, and reduces the agglomeration effect of spinel, which is beneficial to recycling.

[0041] 4.The adsorbent of the present application is simple to prepare, belongs to waste-to-resource, has low cost, and raw materials are easy to obtain. The particle size can be made into various sizes according to actual needs, which is suitable for industrial large-scale production and application. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 Process route map for preparing the solid waste-based adsorbent;

[0043] Figure 2 XRD spectrum of electrolytic manganese residue from a certain electrolytic plant in Guizhou;

[0044] Figure 3 SEM images of the adsorbent prepared in Example 1 (a: magnification 200 times; b: magnification 3500 times). DETAILED DESCRIPTION

[0045] The present application will be further described below in connection with specific examples, but is not limited to the contents of the specification. If not otherwise specified, the "parts" described in the examples are all weight parts.

[0046] The adsorbent preparation method and its properties according to the design of the present application will be described in detail below.

[0047] The chromium plating sludge and electrolytic manganese residue used in the examples of the present application are respectively from a certain electroplating plant in Jiangsu and a certain electrolytic plant in Guizhou. The content of the main chemical components of the electroplating sludge and electrolytic manganese residue is analyzed by X-ray fluorescence spectroscopy (instrument model: XRF-1800), and the results are shown in Table 1. In addition, the raw materials and reagents used in the present application can be purchased.

[0048] Table 1 Composition of chromium-containing electroplating sludge and electrolytic manganese residue

[0049]

[0050] The heavy metal ion wastewater in the present application is a simulated wastewater prepared with pure reagents, and the concentration of heavy metal ions is shown in Table 2:

[0051] Table 2 Concentration of heavy metal ions in wastewater

[0052] Heavy metal class Ni Cu Fe Cd Pb Concentration (mg / L) 247.2 126.8 61.5 58.6 98.5

[0053] Preparation Example 1

[0054] (1) Prepare 25 parts by weight of electrolytic manganese residue and 50 parts by weight of chromium plating sludge, each of which is sieved and dried, ball milled by a ball mill, and passed through a 100 target screen, and then bagged for use;

[0055] (2) The dry electrolytic manganese residue and electroplating sludge obtained in step (1) are mixed thoroughly, and then added into acid solution for stirring at room temperature for 12 hours. The acid washing solution and the residue are obtained by filtration. The residue is washed to neutral and then dried to obtain the acid-activated solid powder 1. The filtrate and washing solution are combined and reused in the next batch of raw materials for acid washing activation. The acid solution is a mixture of citric acid, water and oxalic acid, the concentration of citric acid in the acid solution is 0.1 mol / L, the concentration of oxalic acid is 0.05 mol / L, and the pH of the acid solution is 5. The solid-liquid ratio of the mixture of electrolytic manganese residue and electroplating sludge to the acid solution is 1 g:10 mL, and the stirring speed is 150 rpm.

[0056] (3) The powder 1 obtained in step (2) is mixed with zeolite powder, kaolin and sodium-based bentonite raw materials according to a mass ratio of 10:1:1:1, and the mixture is thoroughly mixed to obtain a solid powder 2.

[0057] (4) The solid powder 2 obtained in step (3) is mixed with straw according to a mass ratio of 4:1, and then placed in a porcelain square boat. When the temperature of the muffle furnace reaches 300℃, the porcelain square boat is placed in the furnace, and the temperature is raised to 1000℃ at a rate of 5℃ / min, and then kept for 60 min. After cooling to room temperature, the porcelain square boat is taken out, ground through a 150-mesh sieve, and a solid powder 3 is obtained.

[0058] (5) 5% of chitosan powder with a deacetylation rate of 95% and 0.5% of activated carbon binder and distilled water, accounting for the total mass of the solid powder 3 and chitosan, are added to the solid powder 3 obtained in step (4), and the mixture is thoroughly mixed. Pellets with a particle size of 2-3 mm are made by a pelletizer, dried, and sieved through a 6-mesh standard sieve to obtain a granular adsorbent.

[0059] From Figure 3 (a) It can be seen that the adsorbent has a rich pore structure, and the pore size distribution is shown in the following figure. Figure 3 (b) As can be seen from the local enlarged view of the spinel part, in the porous structure of the adsorbent, the spinel forms the main body "skeleton" structure of the adsorbent.

[0060] Preparation Example 2

[0061] The rest is the same as Preparation Example 1, except that in step (1), 28 parts by weight of electrolytic manganese residue and 48 parts by weight of electroplating sludge are mixed uniformly.

[0062] Preparation Example 3

[0063] The rest is the same as Preparation Example 1, except that in step (1), 31 parts by weight of electrolytic manganese residue and 46 parts by weight of electroplating sludge are mixed uniformly.

[0064] Preparation Example 4

[0065] The rest is the same as that in Preparation Example 1, except that in step (1), 35 parts of electrolytic manganese residue and 42 parts of electroplating sludge are uniformly mixed according to the ratio.

[0066] Preparation Example 5

[0067] The rest is the same as that in Preparation Example 1, except that in step (2), the acid solution is a mixture of citric acid, water and acetic acid, the concentration of citric acid in the acid solution is 0.1 mol / L, the concentration of acetic acid in the acid solution is 0.05 mol / L, and the pH of the acid solution is 5.

[0068] Preparation Example 6

[0069] In step (2), the acid solution is a mixture of citric acid and water, the concentration of citric acid in the acid solution is 0.1 mol / L, and the pH of the acid solution is 5.

[0070] Preparation Example 7

[0071] The rest is the same as that in Preparation Example 1, except that in step (3), the solid powder 1, zeolite powder, kaolin and sodium-based bentonite raw materials are uniformly mixed according to the mass ratio of 11:0.8:0.8:0.8.

[0072] Preparation Example 8

[0073] The rest is the same as that in Preparation Example 1, except that in step (3), the solid powder 1, zeolite powder, kaolin and sodium-based bentonite raw materials are uniformly mixed according to the mass ratio of 9:1.2:1.2:1.2.

[0074] Preparation Example 9

[0075] The rest is the same as that in Preparation Example 1, except that in step (5), 5% of the total mass of the solid powder 3 and chitosan is added, which is a combination of chitosan powder with a deacetylation rate of 95% and chitosan powder with a deacetylation rate of 80%, and the mass ratio of the two is 1:1, i.e. each accounts for 0.25%.

[0076] Preparation Example 10

[0077] The rest is the same as that in Preparation Example 1, except that in step (5), 5% of the total mass of the solid powder 3 and chitosan is added, which is a combination of chitosan powder with a deacetylation rate of 95% and chitosan powder with a deacetylation rate of 80%, and the mass ratio of the two is 1:0.5.

[0078] Comparative Preparation Example 1

[0079] The rest is the same as that in Preparation Example 1, except that in step (1), 75 parts of electrolytic manganese residue by weight is screened, dried, ball milled by a ball mill, and passed through a 100 target screen, and then bagged for use.

[0080] Comparative Preparation Example 2

[0081] The rest is the same as Preparation Example 1, except that 75 parts by weight of the electroplating sludge prepared in step (1) is screened, dried, ball milled, passed through a 100 mesh sieve, and bagged for use.

[0082] Comparative Preparation Example 3

[0083] The rest is the same as Preparation Example 1, except that step (3) is omitted, and the zeolite powder, kaolin, and sodium-based bentonite are not added.

[0084] The acid-activated solid powder 1 obtained in step (2) is directly mixed with the straw in a mass ratio of 4:1, and the adsorbent is finally obtained.

[0085] Comparative Preparation Example 4

[0086] The rest is the same as Preparation Example 1, except that step (4) is omitted, and the solid powder 2 obtained in step (3) is mixed with 5% of chitosan powder with a deacetylation rate greater than 90% and 0.5% of activated carbon binder based on the total mass of the solid powder 3 and chitosan, and distilled water is thoroughly mixed, and a granulator is used to make material balls with a particle size of 2-3 mm, the material balls are dried, passed through a 6-mesh standard sieve, and the adsorbent is prepared.

[0087] Comparative Preparation Example 5

[0088] The rest is the same as Preparation Example 1, except that step (5) does not add chitosan.

[0089] The solid powder 3 obtained in step (4) is added with 0.5% of activated carbon binder based on the mass of the solid powder 3 and distilled water is thoroughly mixed, and a granulator is used to make material balls with a particle size of 2-3 mm, the material balls are dried, passed through a 6-mesh standard sieve, and the adsorbent is prepared.

[0090] Treatment of heavy metal wastewater

[0091] Examples 1-10

[0092] The solid waste-based adsorbent prepared in Preparation Examples 1-10 is added to the heavy metal wastewater at a dosage of 200 mg / L, and stirred at a speed of 50 r / min for 60 min, and then left to stand for 30 min.

[0093] Example 11

[0094] The rest is the same as Example 1, except that the dosage of the solid waste-based adsorbent in Example 1 is 100 mg / L.

[0095] Example 12

[0096] The rest is the same as example 1, except that the dosage of the solid waste-based adsorbent of example 1 is 300 mg / L.

[0097] Example 13

[0098] The rest is the same as example 1, except that the solid waste-based adsorbent is recovered, dried, and example 1 is repeated, and this process is repeated a total of two times, and the adsorption rate of the third time is calculated.

[0099] Example 14

[0100] The rest is the same as example 1, except that the solid waste-based adsorbent is recovered, dried, and example 1 is repeated, and this process is repeated a total of four times, and the adsorption rate of the fifth time is calculated.

[0101] Comparative examples 1-5

[0102] The solid waste-based adsorbents prepared in comparative example preparation examples 1-5 are added to the heavy metal wastewater at a dosage of 200 mg / L, stirred at a speed of 50 r / min for 60 min, and then left to stand for 30 min.

[0103] Adsorption rate calculation:

[0104] The supernatant at a distance of 2 cm from the liquid surface after the mixed solution in the above examples and comparative examples is left to stand for half an hour, and the heavy metal concentration is tested, and the adsorption rate η of each heavy metal is calculated according to the following formula A , %:

[0105]

[0106] In the formula, - the concentration of ion A in the supernatant, mol / L; - the concentration of ion A in the original wastewater, mol / L; V2- the volume of the wastewater after adsorption, L; V1- the volume of the wastewater before adsorption, L; The calculation results are shown in Table 3.

[0107] Table 3 Adsorption rate of heavy metals in wastewater

[0108]

[0109]

[0110] As can be seen from the overall test results in Table 3, the solid waste-based adsorbent prepared in the present application has strong adsorption, especially for nickel ions and lead ions, and has a very high adsorption rate. And the adsorbent still maintains good adsorption effect after five times of reuse, and is suitable for treating industrial heavy metal wastewater.

[0111] From examples 1, 5, 6, it can be seen that the adsorbent prepared by the composite acid system of examples 1 and 5 has better adsorption effect on metal ions than the single acid system of example 6, which may be due to the higher reduction efficiency, higher metal precipitation efficiency, higher acid activation degree and more stable spinel structure in the composite acid system, so that the adsorption capacity of the adsorbent is strong, and there is no secondary leaching hazard of metal ions (such as hexavalent chromium).

[0112] From examples 1, 9, 10, it can be seen that high degree of deacetylation of chitosan is beneficial to improve the performance of the adsorbent, and the inventors have unexpectedly found that the use of chitosan with different deacetylation rates for compounding has more excellent active amino functional groups, which not only prevents spinel agglomeration but also enhances the adsorption of heavy metals, thereby having more excellent adsorption performance.

[0113] From examples 1 and comparative examples 1-2, it can be seen that even if the substrate materials are the same, if either of the electroplating sludge or the electrolytic manganese residue is missing, the effect of the adsorbent will be greatly reduced. On the one hand, the particle adsorbent is easy to collapse and has poor reuse effect due to the failure to form a spinel structure. On the other hand, the adsorbent mainly relies on the porous structure, and if there is no electrolytic manganese residue and no ammonia-nitrogen overflow, the pore structure will be poor, the adsorption efficiency will be low, and the utilization rate of metal ions will be low, which may cause secondary pollution.

[0114] From examples 1 and comparative examples 3, 4, it can be seen that the adsorbent without adding zeolite powder and other porous materials (comparative example 3) cannot form a rich porous structure, so the adsorption efficiency is reduced. The adsorbent without adding biomass (comparative example 4) has relatively less spinel structure and cannot form a loose structure because the biomass is not activated, so the adsorption rate of the adsorbent formed by solid waste on metal ions is reduced. From example 1 and comparative example 5, it can be seen that the adsorbent without adding chitosan (comparative example 5) not only has a low adsorption rate, but also has a general granulation effect and is easy to collapse, so it is not conducive to recycling and reuse.

[0115] The above detailed description is a specific description of one of the feasible embodiments of the present application, which is not used to limit the patent scope of the present application, and any equivalent implementation or change made without departing from the present application shall be included in the scope of the technical scheme of the present application.

Claims

1. A method for preparing a solid waste-based granular adsorbent using chromium electroplating sludge and electrolytic manganese residue, characterized by, It comprises the following steps: (1) electrolytic manganese residue, chromium electroplating sludge, kaolin and sodium bentonite are respectively ball milled, dried and sieved for use; (2) the sieved electrolytic manganese residue and electroplating sludge obtained in step (1) are mixed, acid leaching treatment is carried out by adding acid solution, and then filtration is carried out to obtain acid washing solution and filter residue, the filter residue is washed to neutral and then dried to obtain acid-activated solid powder 1; (3) the solid powder 1 obtained in step (2) is mixed with zeolite powder, sieved kaolin in step (1) and sodium bentonite to obtain solid powder 2; (4) the solid powder 2 obtained in step (3) is mixed with biomass, calcined, cooled to room temperature, taken out and ground to obtain solid powder 3; (5) chitosan powder, binder and distilled water are added to the solid powder 3 obtained in step (4) and mixed uniformly, granulated, dried, sieved to obtain granular adsorbent; In step (2), the mass ratio of the electrolytic manganese residue and the electroplating sludge is 1:(1.2-2); The acid solution is a mixture of citric acid, water and other carboxylic acids; the concentration of citric acid is 0.1-0.15 mol / L; The other carboxylic acid is selected from one or a combination of two or more of acetic acid, oxalic acid and benzoic acid, and the concentration of the other carboxylic acid is 0.05-0.1 mol / L; the pH value of the acid solution is 4.5-5.5; The biomass is straw or walnut shell.

2. The method of claim 1, wherein, In step (1), the content of Cr in the chromium electroplating sludge is 40-60 wt%; the contents of SiO2, Al2O3, CaO, MnO and SO3 in the electrolytic manganese residue are 80-90 wt% of the total amount of the electrolytic manganese residue, and the content of SO3 is higher than 20%; The sieving is through a 100-200 mesh sieve.

3. The method of claim 1, wherein, The solid-liquid ratio of the mixture of the electrolytic manganese residue and the electroplating sludge to the acid solution is 1 g:10-15 mL.

4. The method of claim 3, wherein, The acid leaching treatment temperature is 20-35℃; the acid leaching treatment time is 10-15 h; and the stirring speed of the acid leaching treatment is 150-300 rpm.

5. The method of claim 1, wherein, In step (3), the content of the zeolite powder is 5-15% of the total mass of the mixture of the electrolytic manganese residue and the electroplating sludge, the content of the kaolin is 8-12% of the total mass of the mixture, and the content of the sodium bentonite is 8-12% of the total mass of the mixture.

6. The method of claim 1, wherein, In step (4), the mass ratio of the solid powder 2 to the biomass is (3-6):1; The calcination temperature is 900-1000℃, and the holding time is 30-60 min; The particle size of the solid powder 3 is 100-150 mesh.

7. The method of claim 1, wherein, In step (5), the content of the chitosan powder is 2-5% of the total mass of the mixture of the solid powder 3 and chitosan; the deacetylation degree of the chitosan is above 80%, and the viscosity is higher than 0.8 Pa·s; The binder is an activated carbon binder, and the amount added is 0.5-2% of the total mass of the mixture of the solid powder 3 and chitosan.

8. The method of claim 7, wherein, In step (5), the chitosan is a combination of two or more chitosans with different deacetylation degrees.

9. The method of claim 8, wherein, Two kinds of chitosan with deacetylation degrees of 80-90% and >90% are combined.

10. The method of claim 9, wherein, The mass ratio of the chitosan with a deacetylation degree of 80-90% to the chitosan with a deacetylation degree of >90% is 1:(1-2).

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