Modified iron tailings solid waste ceramsite, and preparation method and application thereof

Abstract

The application belongs to the technical field of environmental engineering water treatment, and provides a modified iron tailing solid waste ceramsite as well as a preparation method and application thereof, which is prepared from raw materials including the following components in mass fractions: iron tailing 60-80 parts, saw mud 19-39 parts, pore forming agent 1-5 parts, and sodium silicate solution 1-5 parts. 3 The ceramsite provided by the application has a volume density of 1.10-1.25 g / cm , a strength of 5.8-7.1 MPa, an apparent porosity of 62-72%, a hydrochloric acid soluble rate of 0.8-1.3%, and an ammonia nitrogen removal rate of 90.1-94.8%. The ceramsite has the advantages of small volume density, large specific surface area, high strength and apparent porosity, low hydrochloric acid soluble rate, strong specificity to ammonia nitrogen, and high removal rate. After adsorption, the ceramsite is easy to recover, thus achieving the purpose of waste treatment with waste, and solving the problem of large accumulation of iron tailing and saw mud.

Description

Technical Field

[0001] This invention relates to the field of environmental engineering water treatment technology, and in particular to a modified iron tailings solid waste ceramsite, its preparation method, and its application. Background Technology

[0002] Ammonia nitrogen is commonly found in human industrial and agricultural production processes. High concentrations of ammonia nitrogen are prevalent in industrial and agricultural wastewater such as wastewater from the leather and textile industries, landfill leachate, fertilizer wastewater, and mining wastewater. Ammonia nitrogen is ionic ammonia (NH4+). + Ammonia nitrogen combines with molecular ammonia (NH3). Excessive ammonia nitrogen emissions can cause many environmental problems. For example, if the ammonia nitrogen concentration in pond water exceeds 5 mg / L, eutrophication and low oxygen levels will occur, seriously affecting ecological balance and even public health. Therefore, removing ammonia nitrogen from wastewater before discharge to prevent water pollution is of great significance.

[0003] Currently, there are various methods for treating ammonia nitrogen in water, such as biological methods, breakpoint chlorination, membrane separation, ion exchange, and adsorption. Among these, adsorption is a commonly used wastewater treatment method, offering advantages such as wide application range, energy efficiency, simple operation, minimal secondary pollution, reusable adsorbents, and high ammonia nitrogen recovery rates. It can effectively remove ammonia nitrogen from wastewater. The key to the effectiveness of adsorption lies in the selection of the adsorbent. Currently, commonly used ammonia nitrogen adsorbents include biochar, activated carbon, manganese oxide, bentonite, diatomaceous earth, natural zeolite, artificial zeolite, and artificial ceramsite.

[0004] However, existing adsorbents have the following main problems in use: First, using natural minerals as adsorbents, such as natural zeolite and bentonite, does not conform to the current concept of sustainable development; second, biochar is difficult to treat after adsorption, causing secondary pollution; third, activated carbon and artificial zeolite are usually in powder form, with low mechanical strength, making them difficult to separate and recover after adsorption, and activated carbon is also expensive; fourth, artificial ceramsite has low adsorption capacity and poor targeting.

[0005] Tailings are waste residue generated after mineral mining, while sawdust is waste material produced during stone processing. Utilizing tailings and sawdust to prepare ceramsite can reduce the environmental damage and safety hazards caused by solid waste accumulation. Using the prepared ceramsite for wastewater treatment can also achieve waste-to-waste treatment. The resulting ceramsite has the characteristics of high mechanical strength, high porosity, high water absorption, and moderate particle size. However, its numerous large pores and lack of specificity result in a weak ammonia nitrogen adsorption capacity, limiting its application. Therefore, modifying the original tailings ceramsite to improve its ammonia nitrogen removal capacity is of great significance for the high-value utilization of bulk solid waste and the efficient treatment of water resources. Summary of the Invention

[0006] The purpose of this invention is to provide a modified iron tailings solid waste ceramic particle, its preparation method and application, in order to solve the problems of low mechanical strength, difficulty in recycling, small adsorption capacity and poor selectivity of existing ammonia nitrogen adsorbents.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] This invention provides a modified iron tailings solid waste ceramsite, prepared from raw materials comprising the following parts by mass:

[0009] Iron tailings 60-80 parts, sawdust 19-39 parts, pore-forming agent 1-5 parts, sodium silicate solution 1-5 parts.

[0010] Preferably, the iron tailings contain ≥30wt% CaO and ≥25wt% SiO2, and the average particle size of the iron tailings is ≤74μm.

[0011] The sawdust contains SiO2 ≥ 70 wt%, Al2O3 ≥ 15 wt%, and Na2O ≥ 5 wt%, and the average particle size of the sawdust is ≤ 74 μm.

[0012] Preferably, the pore-forming agent is one or more of dextrin, carbon black, and activated carbon;

[0013] The average particle size of the pore-forming agent is ≤15μm.

[0014] Preferably, the sodium silicate solution contains sodium silicate at a mass concentration of 12-14% and sodium oxide at a mass concentration of 4-4.5%.

[0015] The present invention also provides a method for preparing the modified iron tailings solid waste ceramsite, comprising the following steps:

[0016] (1) Iron tailings, sawdust, pore-forming agent and sodium silicate solution are mixed to obtain raw material balls;

[0017] (2) The modified iron tailings solid waste ceramic particles are obtained by calcining the raw material balls and then immersing them in a composite solution for reaction.

[0018] Preferably, the particle size of the raw material balls in step (1) is 3 to 9 mm.

[0019] Preferably, the composite solution in step (2) comprises a NaAlO2 solution and a hexamethyltetramine solution;

[0020] The volume ratio of the NaAlO2 solution to the hexamethyltetramine solution is 98–99.9:0.1–2;

[0021] The concentration of the NaAlO2 solution is 1–3 mol / L, and the concentration of the hexamethyltetramine solution is 0.02–0.04 mol / L.

[0022] Preferably, the calcination temperature in step (2) is 1150–1190°C, the calcination holding time is 30–90 min, and the calcination heating rate is 2–5°C / min.

[0023] Preferably, the reaction temperature in step (2) is 120–160°C and the reaction time is 12–16 h.

[0024] This invention also provides the application of the modified iron tailings solid waste ceramsite in adsorbing ammonia nitrogen in water.

[0025] The present invention has the following beneficial effects

[0026] This invention provides a modified iron tailings solid waste ceramsite, prepared from raw materials comprising the following parts by weight: 60-80 parts iron tailings, 19-39 parts sawdust, 1-5 parts pore-forming agent, and 1-5 parts sodium silicate solution. The raw materials used in this invention are iron tailings and sawdust, both of which are bulk solid wastes, fully realizing the comprehensive utilization of iron tailings and sawdust resources. It has the advantages of high resource utilization rate and low production cost, solving the problem of large-scale accumulation of iron tailings and sawdust.

[0027] The bulk density of the expanded clay aggregate provided by this invention is 1.10–1.25 g / cm³. 3 The adsorption strength is 5.8–7.1 MPa, the apparent porosity is 62–72%, the hydrochloric acid solubility is 0.8–1.3%, and the ammonia nitrogen removal rate is 90.1–94.8%. It possesses advantages such as low bulk density, large specific surface area, high strength and apparent porosity, low hydrochloric acid solubility, and strong specificity and high removal rate for ammonia nitrogen. Furthermore, it is easy to recover after adsorption, achieving the goal of treating waste with waste.

[0028] The raw materials used in this invention contain iron tailings with CaO ≥ 30 wt%, a high content of fluxing metal oxides in the mixed raw materials, and the addition of a pore-forming agent. During calcination, a large amount of this pore is lost, resulting in numerous micron- and nano-sized pores within the ceramsite, thereby reducing the ceramsite density and increasing the apparent porosity and specific surface area. Furthermore, the sawdust contains SiO2 ≥ 70 wt%, and the iron tailings contain SiO2 ≥ 25 wt%. High-temperature calcination forms a small amount of molten phase, which, upon cooling, adheres to the solid phase surface to form a robust framework, thus improving the ceramsite strength and reducing hydrochloric acid solubility.

[0029] The raw materials used in this invention mainly contain CaO, SiO2, and Na2O, possessing numerous macropores and mesopores, enabling the CaA zeolite generated in the reaction to be loaded onto the surface of the ceramsite. CaA zeolite forms chemical bonds with Ca, Si, and Na elements in iron tailings and sawdust, attaching to the surface and pores of the ceramsite, further increasing the number of two types of nanoscale micropores: one-dimensional straight channels (0.74 nm) and eight-membered ring windows (0.4 nm). The macropores and mesopores of the ceramsite itself allow wastewater to enter the interior, increasing the contact area between the liquid and solid phases and facilitating rapid adsorption. The one-dimensional straight channels provided by CaA zeolite allow molecules to enter the zeolite crystals and initially separate large molecules, while the eight-membered ring windows further separate larger molecules, allowing ammonia nitrogen to enter for adsorption. This increases the contact area between wastewater and the ceramsite, as well as the ammonia nitrogen adsorption sites on the ceramsite, reducing the influence of other cations in the wastewater on the ammonia nitrogen adsorption effect, thereby improving the specificity and removal rate of ammonia nitrogen by the ceramsite. Furthermore, the raw materials form calcium nepheline and calcium feldspar crystal phases at high temperatures, which enhance the adsorption capacity of the ceramsite for ammonia nitrogen. In addition, CaA zeolite is attached to the ceramsite, giving it a certain strength and particle size, which facilitates the recovery and treatment of ammonia nitrogen after adsorption. Detailed Implementation

[0030] This invention provides a modified iron tailings solid waste ceramsite, prepared from raw materials comprising the following parts by mass:

[0031] Iron tailings 60-80 parts, sawdust 19-39 parts, pore-forming agent 1-5 parts, sodium silicate solution 1-5 parts.

[0032] In this invention, the mass fraction of the iron tailings is preferably 62-78 parts, more preferably 65-75 parts, and even more preferably 68-72 parts.

[0033] In this invention, the mass fraction of the sawdust is preferably 20 to 38 parts, more preferably 22 to 36 parts, and even more preferably 25 to 35 parts.

[0034] In this invention, the pore-forming agent is preferably 1.5 to 4.5 parts by mass, more preferably 2 to 4 parts, and even more preferably 2.5 to 3.5 parts by mass.

[0035] In this invention, the sodium silicate solution is preferably 1.5 to 4.5 parts by mass, more preferably 2 to 4 parts, and even more preferably 2.5 to 3.5 parts by mass.

[0036] In this invention, the iron tailings preferably contain ≥30wt% CaO, more preferably ≥32wt%, and even more preferably ≥34wt%; SiO2 preferably ≥25wt%, more preferably ≥27wt%, and even more preferably ≥29wt%; and the average particle size of the iron tailings preferably ≤74μm, more preferably ≤72μm, and even more preferably ≤70μm.

[0037] In this invention, the sawdust contains preferably ≥70wt% SiO2, more preferably ≥71wt%, and more preferably ≥72wt%; preferably ≥15wt% Al2O3, more preferably ≥16wt%, and more preferably ≥17wt%; preferably ≥5wt% Na2O, more preferably ≥6wt%, and more preferably ≥7wt%; and the average particle size of the sawdust is preferably ≤74μm, more preferably ≤72μm, and more preferably ≤70μm.

[0038] In this invention, the pore-forming agent is preferably one or more of dextrin, carbon black, and activated carbon;

[0039] The average particle size of the pore-forming agent is preferably ≤15μm, more preferably ≤14μm, and even more preferably ≤13μm.

[0040] In this invention, the sodium silicate solution preferably has a sodium concentration of 12-14%, more preferably 12.5-13.5%, and even more preferably 12.8-13.2%, and the sodium oxide concentration is preferably 4-4.5%, more preferably 4.1-4.4%, and even more preferably 4.2-4.3%.

[0041] The present invention also provides a method for preparing the modified iron tailings solid waste ceramsite, comprising the following steps:

[0042] (1) Iron tailings, sawdust, pore-forming agent and sodium silicate solution are mixed to obtain raw material balls;

[0043] (2) The modified iron tailings solid waste ceramic particles are obtained by calcining the raw material balls and then immersing them in a composite solution for reaction.

[0044] The specific steps of mixing in step (1) are as follows: first, mix the iron tailings, sawdust and pore-forming agent and place them in a granulator. Then, add sodium silicate solution by spraying while the granulator is rotating.

[0045] In this invention, the particle size of the raw material balls in step (1) is preferably 3-9 mm, more preferably 4-8 mm, and even more preferably 5-7 mm.

[0046] In this invention, the composite solution in step (2) preferably comprises a NaAlO2 solution and a hexamethyltetramine solution. The volume ratio of the NaAlO2 solution to the hexamethyltetramine solution is preferably 98-99.9:0.1-2, more preferably 98.2-99.7:0.3-1.8, and even more preferably 98.5-99.4:0.6-1.5. The concentration of the NaAlO2 solution is preferably 1-3 mol / L, more preferably 1.5-2.5 mol / L, and even more preferably 1.8-2.2 mol / L. The concentration of the hexamethyltetramine solution is preferably 0.02-0.04 mol / L, more preferably 0.022-0.038 mol / L, and even more preferably 0.025-0.035 mol / L.

[0047] In step (2), the raw material pellets are dried before calcination, and then the dried raw material pellets are placed in a calcination furnace for preheating before calcination. The drying temperature is preferably 100-110℃, more preferably 102-108℃, and even more preferably 104-106℃; the preheating temperature is preferably 780-820℃, more preferably 785-815℃, and even more preferably 790-810℃.

[0048] In this invention, the calcination temperature in step (2) is preferably 1150-1190℃, more preferably 1160-1180℃, and even more preferably 1165-1175℃. The holding time for calcination is preferably 30-90 min, more preferably 40-80 min, and even more preferably 50-70 min. The heating rate for calcination is preferably 2-5℃ / min, more preferably 2.5-4.5℃ / min, and even more preferably 3-4℃ / min.

[0049] In this invention, the reaction temperature in step (2) is preferably 120-160°C, more preferably 130-150°C, and even more preferably 135-145°C. The reaction time is preferably 12-16h, more preferably 13-15h, and even more preferably 13.5-14.5h.

[0050] The present invention also provides the application of the modified iron tailings solid waste ceramic particles in the adsorption of ammonia nitrogen.

[0051] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0052] Example 1

[0053] 63 portions of iron tailings, 36 portions of sawdust, and 1 portion of pore-forming agent.

[0054] The iron tailings raw material contains 30wt% CaO and 28wt% SiO2.

[0055] The sawdust raw material contains 73 wt% SiO2, 15 wt% Al2O3, and 5 wt% Na2O.

[0056] Iron tailings, sawdust, and pore-forming agent are mixed and placed in a granulator. Two parts of sodium silicate solution are added by spraying while the granulator is rotating to obtain raw material pellets with a particle size of 8 mm.

[0057] Raw material pellets were dried in an oven at 105°C. The dried pellets were then preheated in a calcining furnace at 800°C for 20 minutes, followed by calcination at a rate of 3°C / min to 1170°C for 60 minutes. After removal, the pellets were immersed in a composite solution (NaAlO2 solution and hexamethyltetramine solution in a volume ratio of 98.5:1.5) and reacted at 125°C for 13 hours to obtain modified iron tailings solid waste ceramsite. The concentration of the NaAlO2 solution was 2 mol / L, and the concentration of the hexamethyltetramine solution was 0.03 mol / L.

[0058] The bulk density is 1.25 g / cm³. 3 It has a strength of 7.1 MPa, a porosity of 62%, and a hydrochloric acid solubility of 0.8%.

[0059] Example 2

[0060] 68 parts of iron tailings, 30 parts of sawdust, and 2 parts of pore-forming agent.

[0061] The iron tailings raw material contains 31 wt% CaO and 27 wt% SiO2.

[0062] The sawdust raw material contains 72 wt% SiO2, 15 wt% Al2O3, and 5 wt% Na2O.

[0063] Iron tailings, sawdust, and pore-forming agent are mixed and placed in a granulator. While rotating, 3 parts of sodium silicate solution are added by spraying to obtain raw material pellets with a particle size of 8 mm.

[0064] Raw material pellets were dried in an oven at 105°C. The dried pellets were then preheated in a calcining furnace at 800°C for 20 minutes, followed by calcination at a rate of 3°C / min to 1180°C for 60 minutes. After removal, the pellets were immersed in a composite solution (NaAlO2 solution and hexamethyltetramine solution in a volume ratio of 98.7:1.3) and reacted at 135°C for 14 hours to obtain modified iron tailings solid waste ceramsite. The concentration of the NaAlO2 solution was 2 mol / L, and the concentration of the hexamethyltetramine solution was 0.03 mol / L.

[0065] The bulk density is 1.21 g / cm³. 3 It has a strength of 6.8 MPa, a porosity of 66%, and a hydrochloric acid solubility of 1.0%.

[0066] Example 3

[0067] 73 parts of iron tailings, 24 parts of sawdust, and 3 parts of pore-forming agent.

[0068] The iron tailings raw material contains 32 wt% CaO and 26 wt% SiO2.

[0069] The sawdust raw material contains 71 wt% SiO2, 16 wt% Al2O3, and 6 wt% Na2O.

[0070] Iron tailings, sawdust, and pore-forming agent are mixed and placed in a granulator. Four parts of sodium silicate solution are added by spraying while the granulator is rotating to obtain raw material pellets with a particle size of 8 mm.

[0071] Raw material pellets were dried in an oven at 105°C. The dried pellets were then preheated in a calcining furnace at 800°C for 20 minutes, followed by calcination at a rate of 3°C / min to 1170°C for 45 minutes. After removal, the pellets were immersed in a composite solution (NaAlO2 solution and hexamethyltetramine solution in a volume ratio of 98.9:1.1) and reacted at 145°C for 15 hours to obtain modified iron tailings solid waste ceramsite. The concentration of the NaAlO2 solution was 3 mol / L, and the concentration of the hexamethyltetramine solution was 0.03 mol / L.

[0072] The bulk density is 1.18 g / cm³. 3 It has a strength of 6.3 MPa, a porosity of 69%, and a hydrochloric acid solubility of 1.2%.

[0073] Example 4

[0074] 77 parts of iron tailings, 19 parts of sawdust, and 4 parts of pore-forming agent.

[0075] The iron tailings raw material contains 33 wt% CaO and 25 wt% SiO2.

[0076] The sawdust raw material contains 70 wt% SiO2, 16 wt% Al2O3, and 6 wt% Na2O.

[0077] Iron tailings, sawdust, and pore-forming agent are mixed and placed in a granulator. Five parts of sodium silicate solution are added by spraying while the granulator is rotating to obtain raw material pellets with a particle size of 8 mm.

[0078] Raw material pellets were dried in an oven at 105°C. The dried pellets were then preheated in a calcining furnace at 800°C for 20 minutes, followed by calcination at a rate of 33°C / min to 1170°C for 30 minutes. After removal, the pellets were immersed in a composite solution (NaAlO2 solution and hexamethyltetramine solution in a volume ratio of 99.1:0.9) and reacted at 150°C for 15 hours to obtain modified iron tailings solid waste ceramsite. The concentration of the NaAlO2 solution was 3 mol / L, and the concentration of the hexamethyltetramine solution was 0.03 mol / L.

[0079] The bulk density is 1.10 g / cm³. 3 It has a strength of 5.8 MPa, a porosity of 72%, and a hydrochloric acid solubility of 1.3%.

[0080] Performance testing

[0081] Take 2g of each of the modified iron tailings solid waste ceramsite obtained in Examples 1-4 above and put it into a conical flask containing 100mL of 10mg / L ammonia nitrogen solution. Adjust the pH to 7 and adsorb at 25℃ with shaking at 90r / min for 12h. Filter the adsorbent solution and take 25mL of filtrate. Measure the ammonia nitrogen concentration in the filtrate according to HJ535-2009 "Nessler's Reagent Spectrophotometric Method" and calculate the ammonia nitrogen removal rate. The results are shown in Table 1.

[0082] Table 1 shows the ammonia nitrogen removal rate test results of the modified iron tailings solid waste ceramsite in the examples.

[0083] Example Ammonia nitrogen removal rate % Example 1 90.1 Example 2 92.3 Example 3 93.9 Example 4 94.8

[0084] As can be seen from Table 1, the modified iron tailings solid waste ceramic particles provided by the present invention have excellent removal effect on ammonia nitrogen in water.

[0085] As shown in the above embodiments, the present invention provides a modified iron tailings solid waste ceramsite, prepared from raw materials comprising the following parts by weight: 60-80 parts iron tailings, 19-39 parts sawdust, 1-5 parts pore-forming agent, and 1-5 parts sodium silicate solution. The ceramsite provided by the present invention has a bulk density of 1.10-1.25 g / cm³. 3 It has a strength of 5.8–7.1 MPa, a porosity of 62–72%, a hydrochloric acid solubility of 0.8–1.3%, and an ammonia nitrogen removal rate of 90.1–94.8%. It has the advantages of low bulk density, large specific surface area, high strength and porosity, low hydrochloric acid solubility, and strong targeting and high removal rate of ammonia nitrogen.

[0086] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A modified iron tailings solid waste ceramsite, characterized in that, It is prepared from raw materials comprising the following parts by mass: Iron tailings 60-80 parts, sawdust 19-39 parts, pore-forming agent 1-5 parts, sodium silicate solution 1-5 parts; The iron tailings contain ≥30wt% CaO and ≥25wt% SiO2, and the average particle size of the iron tailings is ≤74μm. The sawdust contains SiO2 ≥ 70 wt%, Al2O3 ≥ 15 wt%, and Na2O ≥ 5 wt%, and the average particle size of the sawdust is ≤ 74 μm; The method for preparing the modified iron tailings solid waste ceramsite includes the following steps: (1) Iron tailings, sawdust, pore-forming agent and sodium silicate solution are mixed to obtain raw material balls; (2) The modified iron tailings solid waste ceramic pellets are obtained by calcining the raw material pellets and then immersing them in a composite solution for reaction. The composite solution described in step (2) comprises a NaAlO2 solution and a hexamethyltetramine solution; The volume ratio of the NaAlO2 solution to the hexamethyltetramine solution is 98–99.9:0.1–2; The concentration of the NaAlO2 solution is 1–3 mol / L, and the concentration of the hexamethyltetramine solution is 0.02–0.04 mol / L.

2. The modified iron tailings solid waste ceramsite as described in claim 1, characterized in that, The pore-forming agent is one or more of dextrin, carbon black, and activated carbon; The average particle size of the pore-forming agent is ≤15μm.

3. The modified iron tailings solid waste ceramsite as described in claim 2, characterized in that, The sodium silicate solution contains sodium silicate at a mass concentration of 12-14% and sodium oxide at a mass concentration of 4-4.5%.

4. The method for preparing modified iron tailings solid waste ceramsite according to any one of claims 1 to 3, characterized in that, Includes the following steps: (1) Iron tailings, sawdust, pore-forming agent and sodium silicate solution are mixed to obtain raw material balls; (2) The modified iron tailings solid waste ceramic pellets are obtained by calcining the raw material pellets and then immersing them in a composite solution for reaction. The composite solution described in step (2) comprises a NaAlO2 solution and a hexamethyltetramine solution; The volume ratio of the NaAlO2 solution to the hexamethyltetramine solution is 98–99.9:0.1–2; The concentration of the NaAlO2 solution is 1–3 mol / L, and the concentration of the hexamethyltetramine solution is 0.02–0.04 mol / L.

5. The method for preparing modified iron tailings solid waste ceramsite as described in claim 4, characterized in that, The particle size of the raw material balls mentioned in step (1) is 3-9 mm.

6. The method for preparing modified iron tailings solid waste ceramsite as described in claim 5, characterized in that, The calcination temperature in step (2) is 1150-1190℃, the holding time for calcination is 30-90 min, and the heating rate for calcination is 2-5℃ / min.

7. The method for preparing modified iron tailings solid waste ceramsite as described in claim 6, characterized in that, The reaction temperature in step (2) is 120-160°C, and the reaction time is 12-16 hours.

8. The application of the modified iron tailings solid waste ceramic particles according to any one of claims 1 to 3 in the adsorption of ammonia nitrogen in water.