Method for treating iron-removing resin eluate from fly ash for alumina production

Abstract

The application provides a treatment method of iron-removing resin eluate for preparing alumina from fly ash. The method comprises the following steps: adding iron powder into the first iron-removing resin eluate to obtain a reduction material slurry, adding sulfide into the reduction material slurry to obtain ferrous sulfide material slurry, adding the ferrous sulfide material slurry into the second iron-removing resin eluate to carry out mercury removal reaction, obtaining post-mercury removal liquid, mixing the post-mercury removal liquid with calcium hydroxide to obtain calcium-containing waste liquid and heavy metal residue. The method can effectively remove heavy metal impurities in the iron-removing resin eluate in the process of preparing alumina from fly ash, and the preparation of mercury removal reagent can be realized by using the materials in the system, so that the iron-removing resin eluate is fully utilized and the material cost is reduced. The calcium-containing waste liquid obtained finally basically does not contain heavy metals, which is beneficial to realize the wastewater treatment and high-value utilization of the iron-removing resin eluate. Meanwhile, the heavy metals in the heavy metal residue are fully solidified and are not easy to leach out, and the toxicity of the solid waste product is also significantly reduced.

Description

Technical Field

[0001] This invention relates to the field of industrial wastewater treatment technology, and more specifically, to a method for treating iron removal resin eluent from alumina produced by fly ash. Background Technology

[0002] High-alumina fly ash is a new type of fly ash that has emerged in the central and western regions of my country in recent years with the development of coal resources in western China and the construction of large-scale thermal power plants. Its Al2O3 content typically reaches around 50 wt%, equivalent to the Al2O3 content in medium-grade bauxite in my country, making it a very valuable recycled aluminum-bearing mineral resource. Utilizing high-alumina fly ash to produce alumina can alleviate the shortage of bauxite resources in my country. Current technology uses a one-step acid leaching process to extract alumina from fly ash.

[0003] However, in addition to alumina, fly ash also contains heavy metal impurities such as mercury, lead, and zinc. These heavy metal impurities also enter the slurry during the hydrochloric acid leaching process. These heavy metal impurities are adsorbed by the iron removal resin during the resin iron removal process after acid leaching and accumulate in the iron removal resin eluent. The presence of heavy metals severely restricts the treatment and high-value utilization of the iron removal resin eluent. Summary of the Invention

[0004] The main objective of this invention is to provide a method for treating iron removal resin eluent from fly ash-based alumina, thereby solving the problems of difficulty in removing heavy metals, high treatment costs, and high toxicity of heavy metal-containing materials in the existing technology.

[0005] To achieve the above objectives, according to one aspect of the present invention, a method for treating iron removal resin eluent from fly ash alumina production is provided. The total mass concentration of heavy metal ions in the iron removal resin eluent is 6-80 g / L. The iron removal resin eluent is divided into two parts, namely a first iron removal resin eluent and a second iron removal resin eluent. The treatment method includes the following steps: Step S1, adding iron powder to the first iron removal resin eluent to carry out a reduction reaction to obtain a reduced slurry; Step S2, adding sulfide to the reduced slurry to carry out a metathesis reaction to obtain a ferrous sulfide slurry; Step S3, adding the ferrous sulfide slurry to the second iron removal resin eluent to carry out a mercury removal reaction to obtain a mercury-removed slurry, and then performing a first filtration to obtain a mercury-removed liquid and mercury-containing slag; Step S4, mixing the mercury-removed liquid with calcium hydroxide to carry out a neutralization reaction to obtain a neutralized slurry, and then performing a second filtration to obtain a calcium-containing waste liquid and heavy metal slag.

[0006] Furthermore, the iron removal resin eluent contains 6–75 mg / L mercury, 0.1–0.32 mg / L lead, 0.5–1.23 mg / L zinc, and 0.02–0.13 mg / L cadmium, with a pH of 0.5–1.5.

[0007] Furthermore, the first iron removal resin eluent accounts for 5-15% of the total volume of the iron removal resin eluent.

[0008] Furthermore, the liquid-to-solid ratio of the first iron-removing resin eluent to the iron powder is 1L:(20-50g); and / or the temperature of the reduction reaction is 20-30℃, and the time is 0.5-1h.

[0009] Furthermore, sulfides include sodium sulfide and / or potassium sulfide.

[0010] Furthermore, the sulfide is added via an aqueous sulfide solution, the mass percentage concentration of which is 60-70%; preferably, the volume ratio of the reducing slurry to the aqueous sulfide solution is 1:(0.5-0.8).

[0011] Further, a metathesis reaction is carried out at 20–30°C for 1.5–2 hours until the pH of the ferrous sulfide slurry is 6–8.

[0012] Further, the mass ratio of the second iron removal resin eluent to the ferrous sulfide slurry is 1:(0.5-1); or the molar concentration ratio of mercury ions in the second iron removal resin eluent to ferrous sulfide in the ferrous sulfide slurry is 1:(500-3000).

[0013] Furthermore, the mercury removal reaction is carried out at a temperature of 20–30°C for 1–2 hours.

[0014] Further, the neutralization reaction is carried out at 20-30°C for 3-4 hours until the pH of the neutralized slurry is 6-8; preferably, mercury-removed liquid is added to calcium hydroxide to carry out the neutralization reaction.

[0015] By applying the technical solution of this invention, ferrous sulfide, a mercury removal agent, is first prepared using iron removal resin eluent. Then, ferrous sulfide is used to adsorb mercury ions in the iron removal resin eluent. After filtration, calcium hydroxide is used to neutralize and solidify the iron ions and other heavy metal ions in the filtrate, resulting in calcium-containing wastewater and heavy metal slag. This method can effectively remove heavy metal impurities from the iron removal resin eluent in the fly ash-to-alumina process. Furthermore, the mercury removal agent can be prepared using materials within the system, ensuring full utilization of the iron removal resin eluent and reducing material costs. The resulting calcium-containing wastewater is essentially free of heavy metals, facilitating wastewater treatment and high-value utilization of the iron removal resin eluent. Simultaneously, the heavy metals in the heavy metal slag are fully solidified and less prone to leaching, significantly reducing the toxicity of the solid waste products, demonstrating broad application prospects. Attached Figure Description

[0016] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0017] Figure 1 A schematic diagram of the treatment process of iron removal resin eluent for alumina production from fly ash according to an embodiment of the present invention is shown. Detailed Implementation

[0018] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0019] Unless otherwise specified, "room temperature" in this invention refers to 20–30°C.

[0020] Unless otherwise specified, in this invention, "liquid-solid ratio" refers to the amount (g) of solid added to 1L of liquid.

[0021] Unless otherwise specified, the "iron removal resin eluent for alumina production from fly ash" in this invention refers to the eluent obtained by dissolving fly ash in hydrochloric acid, treating the solution with iron removal resin, and then eluting the iron removal resin with hydrochloric acid (which can be 1 mol / L), which contains a relatively large amount of ferric ions and heavy metal ions.

[0022] As described in the background section of this invention, the prior art has problems such as difficulty in removing heavy metals from the iron removal resin eluent of fly ash-based alumina, high processing costs, and high toxicity of materials containing heavy metals. To address the aforementioned problems, in a typical embodiment of the present invention, a method for treating iron removal resin eluent from fly ash-based alumina production is provided. The total mass concentration of heavy metal ions in the iron removal resin eluent is 6–80 g / L. The iron removal resin eluent is divided into two parts: a first iron removal resin eluent and a second iron removal resin eluent. The treatment method includes the following steps: Step S1, adding iron powder to the first iron removal resin eluent to conduct a reduction reaction, obtaining a reduced slurry; Step S2, adding sulfide to the reduced slurry to conduct a metathesis reaction, obtaining a ferrous sulfide slurry; Step S3, adding the ferrous sulfide slurry to the second iron removal resin eluent to conduct a mercury removal reaction, obtaining a mercury-removed slurry, followed by a first filtration to obtain a mercury-removed liquid and mercury-containing slag; Step S4, mixing the mercury-removed liquid with calcium hydroxide to conduct a neutralization reaction, obtaining a neutralized slurry, followed by a second filtration to obtain a calcium-containing waste liquid and heavy metal slag.

[0023] Specifically, iron powder is first added to the first iron removal resin eluent to carry out a reduction reaction, so that all the trivalent ferric chloride in the iron removal resin eluent is converted into divalent ferrous chloride, and a reduced raw material slurry is obtained; then, sulfide is added to the reduced raw material slurry to carry out a metathesis reaction, and ferrous sulfide slurry is obtained.

[0024] Then, ferrous sulfide slurry is added to the second iron removal resin eluent to carry out the mercury removal reaction. The solid ferrous sulfide particles present in the slurry adsorb mercury ions in the iron removal resin eluent. At the same time, some mercury ions undergo metathesis with ferrous sulfide to form mercury sulfide precipitate. The mercury removal slurry obtained after the reaction is fully filtered. The filtrate is the iron removal resin eluent after mercury removal, and the filter residue is iron sulfide slag containing mercury sulfide.

[0025] Finally, the mercury-removed solution is mixed with calcium hydroxide to carry out a neutralization reaction, allowing the residual heavy metals in the mercury-removed solution to dissolve in the OH-. - The mixture settles in the presence of calcium hydroxide, while some calcium hydroxide can promote the sedimentation of heavy metals through physical adsorption, resulting in a neutralized slurry. Then, a second filtration is performed. The filtrate is a calcium chloride solution containing a small amount of potassium and sodium impurities, and the filter residue is a solid residue of ferric hydroxide and magnesium hydroxide that has settled heavy metals.

[0026] This invention proposes for the first time a method for removing heavy metals from the iron removal resin eluent in the fly ash-to-alumina process. This method effectively removes heavy metal impurities from the eluent and allows for the preparation of mercury removal agents using materials within the system, thus fully utilizing the eluent and reducing material costs. The resulting calcium-containing wastewater is essentially free of heavy metals, and its indicators meet the requirements of the "Emission Standard for Pollutants from Aluminum Industry." This facilitates the wastewater treatment and high-value utilization of the iron removal resin eluent. Furthermore, the addition of calcium hydroxide during the treatment process ensures that heavy metals are fully settled and adsorbed, solidified in the heavy metal slag, and difficult to leach. The toxicity of the solid waste products is also significantly reduced, demonstrating broad application prospects.

[0027] In a preferred embodiment, the iron removal resin eluent contains 6-75 mg / L of mercury, 0.1-0.32 mg / L of lead, 0.5-1.23 mg / L of zinc, and 0.02-0.13 mg / L of cadmium, with a pH of 0.5-1.5. Iron removal resin eluents with heavy metal content within the above range are more suitable for processing using the method of the present invention, resulting in better heavy metal removal and better suitability for the material characteristics of current industrial production processes, thus offering greater practicality.

[0028] The amount of the first iron removal resin eluent needs to be set according to the heavy metal content in the eluent. In a preferred embodiment, the first iron removal resin eluent accounts for 5-15% of the volume of the iron removal resin eluent. Under the above conditions, the amount of ferrous sulfide prepared is more compatible with the remaining second iron removal resin eluent, which is more conducive to providing sufficient solid ferrous sulfide particles and sulfur ions, further promoting the full progress of the mercury removal reaction, thereby improving the heavy metal removal effect of the eluent, and at the same time, it can better realize the full utilization of system materials and reduce processing costs.

[0029] To ensure more complete reduction of ferric ions in the first iron-removing resin eluent, thereby facilitating the subsequent preparation of ferrous sulfide and heavy metal removal, in a preferred embodiment, the liquid-to-solid ratio of the first iron-removing resin eluent to iron powder is 1 L:(20–50 g); and / or the reduction reaction temperature is 20–30°C, and the time is 0.5–1 h. Iron powder is added in excess, and the specific amount of iron powder added and the reduction time can be adjusted according to actual conditions. For example, when using starch-potassium iodide test paper to determine the ferric ions in the slurry, the addition of iron powder or the reduction reaction is stopped when ferric ions are undetectable. These are things that those skilled in the art will understand and will not be elaborated upon here.

[0030] In a preferred embodiment, the sulfide includes sodium sulfide and / or potassium sulfide, which helps to further reduce material costs.

[0031] To further improve the reaction rate of the metathesis reaction, in a preferred embodiment, the sulfide is added through an aqueous sulfide solution with a mass percentage concentration of 60-70%. Preferably, the volume ratio of the reducing slurry to the aqueous sulfide solution is 1:(0.5-0.8), which is beneficial to provide sufficient sulfur ions to participate in the formation of ferrous sulfide, thereby further improving the subsequent removal effect of heavy metals.

[0032] For similar reasons, in a preferred embodiment, the metathesis reaction is carried out at 20–30°C for 1.5–2 hours until the pH of the ferrous sulfide slurry is 6–8.

[0033] In a preferred embodiment, the mass ratio of the second iron removal resin eluent to the ferrous sulfide slurry is 1:(0.5-1); or the molar concentration ratio of mercury ions in the second iron removal resin eluent to ferrous sulfide in the ferrous sulfide slurry is 1:(500-3000). Under these conditions, it is more advantageous for ferrous sulfide to bind heavy metal mercury ions in the slurry through physical adsorption and metathesis reaction. At the same time, the above-mentioned amount of ferrous sulfide slurry can further reduce the amount of ferrous sulfide entering the system, thereby reducing the impact on the system materials and further reducing the metal ion content of the final waste liquid after treatment.

[0034] In order to further improve the precipitation effect of ferrous sulfide on heavy metal ions such as mercury ions, in a preferred embodiment, the mercury removal reaction temperature is 20-30°C and the time is 1-2 hours.

[0035] In a preferred embodiment, the neutralization reaction is carried out at 20–30°C for 3–4 hours until the pH of the neutralized slurry is 6–8. Under these conditions, the acidic slurry can be more thoroughly neutralized, allowing heavy metal ions to be more fully settled or adsorbed and solidified into the heavy metal slag, resulting in better removal efficiency and reduced leaching, further reducing the toxicity of the solid waste products. Preferably, mercury-removed liquid is added to calcium hydroxide for the neutralization reaction. Reverse addition further avoids changes in the pH of the treated waste liquid, which is beneficial for further purification and high-value utilization of the waste liquid.

[0036] Typical, but not limiting, the volume percentage of the first iron removal resin eluent in the iron removal resin eluent is 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or any two of these values.

[0037] Typical, but not limiting, liquid-to-solid ratios of the first iron-removing resin eluent to iron powder are 1L:20g, 1L:25g, 1L:30g, 1L:35g, 1L:40g, 1L:45g, 1L:50g, or any two of these values.

[0038] Typical, but not limiting, volume ratios of the slurry to the sulfide aqueous solution are 1:0.5, 1:0.55, 1:0.6, 1:0.65, 1:0.7, 1:0.75, 1:0.8, or any two of these values.

[0039] Typical, but not limiting, mass ratios of the second iron removal resin eluent to ferrous sulfide slurry are 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, or any two of these values; or molar ratios of mercury ions in the second iron removal resin eluent to ferrous sulfide in the ferrous sulfide slurry are 1:500, 1:1000, 1:1500, 1:2000, 1:2500, 1:3000, or any two of these values.

[0040] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0041] Example 1

[0042] A schematic diagram of the treatment process for iron removal resin eluent in fly ash-to-alumina production is shown below. Figure 1 As shown.

[0043] The iron removal resin eluent for alumina production from fly ash contains 40 mg / L mercury, 0.2 mg / L lead, 0.9 mg / L zinc, and 0.08 mg / L cadmium, with a pH of 1. 10% (volume percentage) is taken as the first iron removal resin eluent, and the remainder is taken as the second iron removal resin eluent.

[0044] Step S1: Add iron powder to the first iron removal resin eluent at a liquid-to-solid ratio of 1L:35g to carry out a reduction reaction at room temperature for 45 minutes to obtain a reduced slurry.

[0045] Step S2: Add a 65% sodium sulfide aqueous solution to the reducing slurry at a volume ratio of 1:0.6 to carry out a metathesis reaction at room temperature for 1.8 hours to obtain a ferrous sulfide slurry with a pH of 7.

[0046] Step S3: Add ferrous sulfide slurry to the second iron removal resin eluent at a mass ratio of 1:0.5 to carry out the mercury removal reaction at room temperature for 1.5 hours to obtain the mercury removal slurry. Then, perform the first filtration to obtain the mercury removal liquid and mercury-containing slag.

[0047] In step S4, mercury-removed liquid is added to calcium hydroxide at room temperature to carry out a neutralization reaction for 3.5 hours, resulting in a neutralized slurry with a pH of 7. The slurry is then filtered a second time to obtain calcium-containing waste liquid and heavy metal slag.

[0048] Example 2

[0049] The iron removal resin eluent for alumina production from fly ash contains 40 mg / L mercury, 0.2 mg / L lead, 0.9 mg / L zinc, and 0.08 mg / L cadmium, with a pH of 1. 10% (volume percentage) is taken as the first iron removal resin eluent, and the remainder is taken as the second iron removal resin eluent.

[0050] Step S1: Add iron powder to the first iron removal resin eluent at a liquid-to-solid ratio of 1L:35g to carry out a reduction reaction at room temperature for 45 minutes to obtain a reduced slurry.

[0051] Step S2: Add a 65% sodium sulfide aqueous solution to the reducing slurry at a volume ratio of 1:0.6 to carry out a metathesis reaction at room temperature for 1.8 hours to obtain a ferrous sulfide slurry with a pH of 7.

[0052] Step S3: Add ferrous sulfide slurry to the second iron removal resin eluent at a mass ratio of 1:1 to carry out the mercury removal reaction at room temperature for 1.5 hours to obtain the mercury removal slurry. Then, perform the first filtration to obtain the mercury removal liquid and mercury-containing slag.

[0053] In step S4, mercury-removed liquid is added to calcium hydroxide at room temperature to carry out a neutralization reaction for 3.5 hours, resulting in a neutralized slurry with a pH of 7. The slurry is then filtered a second time to obtain calcium-containing waste liquid and heavy metal slag.

[0054] Example 3

[0055] The iron removal resin eluent for alumina production from fly ash contains 6 mg / L mercury, 0.1 mg / L lead, 0.5 mg / L zinc, and 0.02 mg / L cadmium, with a pH of 0.5. 10% (volume percentage) is taken as the first iron removal resin eluent, and the remainder is used as the second iron removal resin eluent.

[0056] Step S1: Add iron powder to the first iron removal resin eluent at a liquid-to-solid ratio of 1L:35g to carry out a reduction reaction at room temperature for 45 minutes to obtain a reduced slurry.

[0057] Step S2: Add a 65% sodium sulfide aqueous solution to the reducing slurry at a volume ratio of 1:0.6 to carry out a metathesis reaction at room temperature for 1.8 hours to obtain a ferrous sulfide slurry with a pH of 7.

[0058] Step S3: Add ferrous sulfide slurry to the second iron removal resin eluent at a mass ratio of 1:0.5 to carry out the mercury removal reaction at room temperature for 1.5 hours to obtain the mercury removal slurry. Then, perform the first filtration to obtain the mercury removal liquid and mercury-containing slag.

[0059] In step S4, mercury-removed liquid is added to calcium hydroxide at room temperature to carry out a neutralization reaction for 3.5 hours, resulting in a neutralized slurry with a pH of 7. The slurry is then filtered a second time to obtain calcium-containing waste liquid and heavy metal slag.

[0060] Example 4

[0061] The iron removal resin eluent for alumina production from fly ash contains 75 mg / L mercury, 0.32 mg / L lead, 1.23 mg / L zinc, and 0.13 mg / L cadmium, with a pH of 1.5. 10% (volume percentage) is taken as the first iron removal resin eluent, and the remainder is used as the second iron removal resin eluent.

[0062] Step S1: Add iron powder to the first iron removal resin eluent at a liquid-to-solid ratio of 1L:35g to carry out a reduction reaction at room temperature for 45 minutes to obtain a reduced slurry.

[0063] Step S2: Add a 65% sodium sulfide aqueous solution to the reducing slurry at a volume ratio of 1:0.6 to carry out a metathesis reaction at room temperature for 1.8 hours to obtain a ferrous sulfide slurry with a pH of 7.

[0064] Step S3: Add ferrous sulfide slurry to the second iron removal resin eluent at a mass ratio of 1:0.5 to carry out the mercury removal reaction at room temperature for 1.5 hours to obtain the mercury removal slurry. Then, perform the first filtration to obtain the mercury removal liquid and mercury-containing slag.

[0065] In step S4, mercury-removed liquid is added to calcium hydroxide at room temperature to carry out a neutralization reaction for 3.5 hours, resulting in a neutralized slurry with a pH of 7. The slurry is then filtered a second time to obtain calcium-containing waste liquid and heavy metal slag.

[0066] Example 5

[0067] The iron removal resin eluent for alumina production from fly ash contains 40 mg / L mercury, 0.2 mg / L lead, 0.9 mg / L zinc, and 0.08 mg / L cadmium, with a pH of 1. 5% (volume percentage) is taken as the first iron removal resin eluent, and the remainder is used as the second iron removal resin eluent.

[0068] Step S1: Add iron powder to the first iron removal resin eluent at a liquid-to-solid ratio of 1L:35g to carry out a reduction reaction at room temperature for 45 minutes to obtain a reduced slurry.

[0069] Step S2: Add a 65% sodium sulfide aqueous solution to the reducing slurry at a volume ratio of 1:0.6 to carry out a metathesis reaction at room temperature for 1.8 hours to obtain a ferrous sulfide slurry with a pH of 7.

[0070] Step S3: Add ferrous sulfide slurry to the second iron removal resin eluent at a mass ratio of 1:0.5 to carry out the mercury removal reaction at room temperature for 1.5 hours to obtain the mercury removal slurry. Then, perform the first filtration to obtain the mercury removal liquid and mercury-containing slag.

[0071] In step S4, mercury-removed liquid is added to calcium hydroxide at room temperature to carry out a neutralization reaction for 3.5 hours, resulting in a neutralized slurry with a pH of 7. The slurry is then filtered a second time to obtain calcium-containing waste liquid and heavy metal slag.

[0072] Example 6

[0073] The iron removal resin eluent for alumina production from fly ash contains 40 mg / L mercury, 0.2 mg / L lead, 0.9 mg / L zinc, and 0.08 mg / L cadmium, with a pH of 1. 15% (volume percentage) is taken out as the first iron removal resin eluent, and the remainder is used as the second iron removal resin eluent.

[0074] Step S1: Add iron powder to the first iron removal resin eluent at a liquid-to-solid ratio of 1L:35g to carry out a reduction reaction at room temperature for 45 minutes to obtain a reduced slurry.

[0075] Step S2: Add a 65% sodium sulfide aqueous solution to the reducing slurry at a volume ratio of 1:0.6 to carry out a metathesis reaction at room temperature for 1.8 hours to obtain a ferrous sulfide slurry with a pH of 7.

[0076] Step S3: Add ferrous sulfide slurry to the second iron removal resin eluent at a mass ratio of 1:0.5 to carry out the mercury removal reaction at room temperature for 1.5 hours to obtain the mercury removal slurry. Then, perform the first filtration to obtain the mercury removal liquid and mercury-containing slag.

[0077] In step S4, mercury-removed liquid is added to calcium hydroxide at room temperature to carry out a neutralization reaction for 3.5 hours, resulting in a neutralized slurry with a pH of 7. The slurry is then filtered a second time to obtain calcium-containing waste liquid and heavy metal slag.

[0078] Example 7

[0079] The difference from Example 1 is that in step S1, iron powder is added to the first iron removal resin eluent at a liquid-to-solid ratio of 1L:20g to carry out a reduction reaction at room temperature for 60 minutes to obtain a reduced slurry.

[0080] Example 8

[0081] The difference from Example 1 is that in step S1, iron powder is added to the first iron removal resin eluent at a liquid-to-solid ratio of 1L:50g to carry out a reduction reaction at room temperature for 30 minutes to obtain a reduced slurry.

[0082] Example 9

[0083] The difference from Example 1 is that in step S2, a sodium sulfide aqueous solution with a mass percentage concentration of 70% is added to the reducing slurry at a volume ratio of 1:0.5 to carry out a metathesis reaction at room temperature for 2 hours, resulting in a ferrous sulfide slurry with a pH of 8.

[0084] Example 10

[0085] The difference from Example 1 is that in step S2, a potassium sulfide aqueous solution with a mass percentage concentration of 60% is added to the reducing slurry at a volume ratio of 1:0.8 to carry out a metathesis reaction at room temperature for 1.5 hours, resulting in a ferrous sulfide slurry with a pH of 6.

[0086] Example 11

[0087] The difference from Example 1 is that in step S3, ferrous sulfide slurry is added to the second iron removal resin eluent at a molar concentration ratio of 1:500 for mercury removal, at room temperature for 2 hours, to obtain a mercury-removed slurry, which is then filtered first to obtain a mercury-removed liquid and mercury-containing slag.

[0088] Example 12

[0089] The difference from Example 1 is that in step S3, ferrous sulfide slurry is added to the second iron removal resin eluent at a molar concentration ratio of 1:3000 for mercury removal, at room temperature for 1 hour, to obtain a mercury-removed slurry, which is then filtered first to obtain a mercury-removed liquid and mercury-containing slag.

[0090] Example 13

[0091] The difference from Example 1 is that in step S4, mercury-removed liquid is added to calcium hydroxide at room temperature to carry out a neutralization reaction for 3 hours, resulting in a neutralized slurry with a pH of 6. Then, a second filtration is performed to obtain calcium-containing waste liquid and heavy metal slag.

[0092] Example 14

[0093] The difference from Example 1 is that in step S4, mercury-removed liquid is added to calcium hydroxide at room temperature to carry out a neutralization reaction for 4 hours, resulting in a neutralized slurry with a pH of 8. Then, a second filtration is performed to obtain calcium-containing waste liquid and heavy metal slag.

[0094] Comparative Example 1

[0095] The iron removal resin eluent for alumina production from fly ash contains 40 mg / L mercury, 0.2 mg / L lead, 0.9 mg / L zinc, and 0.08 mg / L cadmium, with a pH of 1.

[0096] Step S1: Add iron powder to the iron removal resin eluent at a liquid-to-solid ratio of 1L:35g to carry out the mercury removal reaction at room temperature for 1.5 hours to obtain a mercury removal slurry. Then, perform the first filtration to obtain the mercury removal liquid and mercury-containing slag.

[0097] In step S2, mercury-free liquid is added to calcium hydroxide at room temperature to carry out a neutralization reaction for 3.5 hours, resulting in a neutralized slurry with a pH of 7. The slurry is then filtered a second time to obtain calcium-containing waste liquid and heavy metal slag.

[0098] Comparative Example 2

[0099] The iron removal resin eluent for alumina production from fly ash contains 40 mg / L mercury, 0.2 mg / L lead, 0.9 mg / L zinc, and 0.08 mg / L cadmium, with a pH of 1. 10% (volume percentage) is taken as the first iron removal resin eluent, and the remainder is taken as the second iron removal resin eluent.

[0100] Step S1: Add iron powder to the first iron removal resin eluent at a liquid-to-solid ratio of 1L:35g to carry out a reduction reaction at room temperature for 45 minutes to obtain a reduced slurry.

[0101] Step S2: Add a 65% sodium sulfide aqueous solution to the reducing slurry at a volume ratio of 1:0.6 to carry out a metathesis reaction at room temperature for 1.8 hours to obtain a ferrous sulfide slurry with a pH of 7.

[0102] Step S3: Add ferrous sulfide slurry to the second iron removal resin eluent at a mass ratio of 1:0.5 to carry out the mercury removal reaction at room temperature for 1.5 hours to obtain the mercury removal slurry. Then, perform the first filtration to obtain the mercury removal liquid and mercury-containing slag.

[0103] In step S4, mercury-removed liquid is added to sodium hydroxide solution at room temperature to carry out a neutralization reaction for 3.5 hours, resulting in a neutralized slurry with a pH of 7. The slurry is then filtered a second time to obtain waste liquid and heavy metal slag.

[0104] The waste liquid and waste residue obtained from the above-described embodiments and comparative examples were tested, and the results are shown in Tables 1 to 3.

[0105] Test method:

[0106] Waste liquid: GB25465-2010 "Emission Standard of Pollutants for Aluminum Industry" and GB30770-2014 "Emission Standard of Pollutants for Tin, Antimony and Mercury Industry".

[0107] Waste residue: GB 5085.3-2007 "Identification Standard for Hazardous Waste - Leaching Toxicity Identification".

[0108] Table 1

[0109]

[0110]

[0111] Note: "L" means that the detection limit of this method is below the detection limit and therefore not detected.

[0112] Table 2

[0113]

[0114] Note: "L" means that the detection limit of this method is below the detection limit and therefore not detected.

[0115] Table 3

[0116]

[0117] As shown in Tables 1 and 3, all the detection indicators of the waste liquid in each embodiment of the present invention are far lower than the direct emission standards for newly built enterprises in the "Emission Standard of Pollutants for Aluminum Industry" (GB25465-2010) and the "Emission Standard of Pollutants for Tin, Antimony and Mercury Industry" (GB30770-2014). As shown in Tables 1 and 3, the detection results of the leachate from the waste residue in each embodiment of the present invention are far lower than all indicators in the "Identification Standard for Hazardous Waste: Leaching Toxicity Identification" (GB 5085.3-2007), indicating that the leaching toxicity of the waste residue generated by the present invention does not belong to hazardous waste.

[0118] As can be seen from the above, compared with the comparative example, each embodiment of the present invention first uses iron removal resin eluent to prepare a mercury removal agent, ferrous sulfide, and then uses ferrous sulfide to adsorb mercury ions in the iron removal resin eluent. After filtration, calcium hydroxide is used to neutralize and solidify the iron ions and other heavy metal ions in the filtrate, resulting in calcium-containing waste liquid and heavy metal slag. The method of the present invention can effectively remove heavy metal impurities from the iron removal resin eluent in the fly ash to alumina process, and can utilize the materials in the system to prepare the mercury removal agent, making full use of the iron removal resin eluent and reducing material costs. The final calcium-containing waste liquid is basically free of heavy metals, which is conducive to the wastewater treatment and high-value utilization of the iron removal resin eluent. At the same time, the heavy metals in the heavy metal slag are fully solidified and not easily leached, and the toxicity of the solid waste products is also significantly reduced, showing broad application prospects.

[0119] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for treating iron removal resin eluent from fly ash-based alumina production, characterized in that, The total mass concentration of heavy metal ions in the iron removal resin eluent is 6-80 g / L. The iron removal resin eluent is divided into two parts: a first iron removal resin eluent and a second iron removal resin eluent. The treatment method includes the following steps: Step S1: Add iron powder to the first iron removal resin eluent to carry out a reduction reaction and obtain a reduced slurry. Step S2: Sulfide is added to the reducing slurry to carry out a metathesis reaction to obtain ferrous sulfide slurry; Step S3: Add the ferrous sulfide slurry to the second iron removal resin eluent to carry out the mercury removal reaction, obtain the mercury removal slurry, and then perform the first filtration to obtain the mercury removal liquid and mercury-containing slag. Step S4: Mix the mercury-removed liquid with calcium hydroxide to carry out a neutralization reaction to obtain a neutralized slurry, and then perform a second filtration to obtain calcium-containing waste liquid and heavy metal slag.

2. The processing method according to claim 1, characterized in that, The iron removal resin eluent contains 6-75 mg / L mercury, 0.1-0.32 mg / L lead, 0.5-1.23 mg / L zinc, and 0.02-0.13 mg / L cadmium, with a pH of 0.5-1.

5.

3. The processing method according to claim 1 or 2, characterized in that, The first iron removal resin eluent accounts for 5-15% of the volume percentage of the iron removal resin eluent.

4. The processing method according to claim 1 or 2, characterized in that, The liquid-to-solid ratio of the first iron-removing resin eluent to the iron powder is 1L:(20~50g); and / or the temperature of the reduction reaction is 20~30℃, and the time is 0.5~1h.

5. The processing method according to claim 1 or 2, characterized in that, The sulfides include sodium sulfide and / or potassium sulfide.

6. The processing method according to claim 1 or 2, characterized in that, The sulfide is added via an aqueous sulfide solution, wherein the mass percentage concentration of the aqueous sulfide solution is 60-70%.

7. The processing method according to claim 6, characterized in that, The volume ratio of the reducing slurry to the sulfide aqueous solution is 1:(0.5~0.8).

8. The processing method according to claim 1 or 2, characterized in that, The metathesis reaction is carried out at 20-30℃ for 1.5-2 hours until the pH of the ferrous sulfide slurry is 6-8.

9. The processing method according to claim 1 or 2, characterized in that, The mass ratio of the second iron-removing resin eluent to the ferrous sulfide slurry is 1:(0.5~1); or The ratio of mercury ions in the second iron removal resin eluent to the molar concentration of ferrous sulfide in the ferrous sulfide slurry is 1:(500~3000).

10. The processing method according to claim 1 or 2, characterized in that, The mercury removal reaction is carried out at a temperature of 20-30°C for 1-2 hours.

11. The processing method according to claim 1 or 2, characterized in that, The neutralization reaction is carried out at 20-30℃ for 3-4 hours until the pH of the neutralized slurry is 6-8.

12. The processing method according to claim 10, characterized in that, The mercury-removed solution is added to calcium hydroxide to carry out the neutralization reaction.

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