Harmless co-treatment method for acid mine wastewater and incineration fly ash

Abstract

The invention belongs to the technical field of solid waste and wastewater treatment, and particularly relates to a mine acid wastewater and incineration fly ash harmless co-treatment method which comprises the following steps: at normal temperature, adding an alkaline solution into incineration fly ash to be treated to obtain mixed slurry; heating and stirring the mixed slurry; adding mine acid wastewater into the mixed slurry obtained in the previous step until the pH value is adjusted to be neutral; transferring the neutral mixed slurry into a microwave hydrothermal reaction kettle for microwave-assisted hydrothermal treatment, and cooling the mixed slurry to room temperature after the treatment is finished; and carrying out solid-liquid separation treatment on the cooled mixed slurry, discharging the obtained liquid-phase product as waste liquid, and drying the obtained solid-phase product to be reused as an adsorbent. The harmless co-treatment method provided by the invention simultaneously solves the harmless and stable treatment problems of two hazardous wastes, namely the mine acid wastewater and the waste incineration fly ash, and meanwhile, the treated fly ash also has extremely high stability and adsorption characteristic.

Description

Technical Field

[0001] This application belongs to the technical field of solid waste and wastewater treatment, and specifically relates to a method for harmless co-disposal of mine acid wastewater and incineration fly ash. Background Art

[0002] Mineral resources, as important natural resources that drive the rapid development of human society, have induced a series of ecological and environmental problems due to long-term disorderly and destructive mining. Mine acid wastewater (AMD) is an industrial wastewater generated during the mining, processing, and tailings stacking of mineral resources. When the ore is oxidized or eroded by rainwater, it has characteristics such as low pH, high concentration of sulfate (SO 4 2- ), and various toxic heavy metal ions (such as Fe 2+ , Cu 2+ , Mn 2+ , Cd 2+ etc.). The treatment technologies for AMD wastewater can be mainly divided into two categories. Among them, the active treatment technologies mainly include sulfide precipitation method, neutralization precipitation method, electrolysis method, ion exchange method, redox method, etc. Although these treatment technologies have advantages such as convenient operation, quick treatment, and short treatment cycle, they will cause secondary pollution during the treatment process, and the operation and maintenance costs are relatively high; the passive treatment technologies mainly include constructed wetland method, microbial reduction method, and BST (Biological source treatment) microbial comprehensive technology, etc. These technologies have the advantages of low operation cost, strong applicability, and no secondary pollution. However, due to the limitation of the tolerance of plants or microorganisms themselves, there are problems such as a relatively small range of pH values to be treated, poor treatment effects on some heavy metal ions, and low treatment efficiency.

[0003] Incineration treatment has become a widely adopted domestic waste treatment technology in China due to its advantages such as low land occupation area, significant reduction, and heat recovery. During the incineration process of domestic waste, fly ash accounting for 3 - 5% of the waste mass will be generated. Since the fly ash from waste incineration contains a large amount of toxic heavy metals (such as Pb, Cd, Cr, etc.) and volatile organic pollutants such as dioxins, it has been included in the "National Hazardous Waste List" with the number HW18. Therefore, realizing the harmless disposal and resource utilization of fly ash from waste incineration has become the most urgent need in the industry.

[0004] At present, the harmless treatment technologies for fly ash mainly include cement solidification, chemical agent stabilization, vitrification / melting solidification and other technologies. Among them, the cement solidification technology uses inorganic / organic solidifying agents to form a solidified body with fly ash, and through saponification reaction or hydration reaction with heavy metals in fly ash, the purpose of heavy metal stabilization is achieved. However, the fly ash treated by this technology has a relatively large volume increase, and cannot completely eliminate dioxin-like persistent organic pollutants. At the same time, the solidification effect on amphoteric heavy metals such as lead and zinc is not good. The chemical agent stabilization technology mainly decomposes and converts toxic substances into substances with low mobility, low solubility and low toxicity through a series of chemical reactions between organic / inorganic agents and fly ash. However, it is difficult for this technology to achieve the synchronous stabilization of multiple heavy metals, and the treated waste liquid contains soluble salts and suspended heavy metals, which will cause secondary pollution. The vitrification / melting solidification technology heats fly ash to the melting temperature (700 - 2200 °C), and then quickly cools the slag. In this process, organic pollutants such as fly dioxin will thermally decompose and gasify, and the treated fly ash will form a dense and stable glassy slag, permanently sealing the toxic heavy metals in it. However, too high melting temperature will cause heavy metal volatilization and secondary pollution.

[0005] In summary, although there are already treatment methods for mine acid wastewater and fly ash respectively in the existing technologies, they all have the above-mentioned deficiencies. Moreover, there is currently no effective harmless co-disposal method for mine acid wastewater and fly ash in the existing technologies. Summary of the Invention

[0006] In order to solve at least one technical problem existing in the existing technology, the present application provides a harmless co-disposal method for mine acid wastewater and incineration fly ash.

[0007] The present application discloses a harmless co-disposal method for mine acid wastewater and incineration fly ash, which includes the following steps: Step 1: At room temperature, add an alkaline solution to the incineration fly ash to be treated to obtain a mixed slurry; Step 2: Heat and stir the mixed slurry obtained in Step 1; Step 3: Add mine acid wastewater to the mixed slurry obtained by stirring in Step 2 until the pH value of the mixed slurry is adjusted to neutral; Step 4: Transfer the neutral mixed slurry obtained in Step 3 to a microwave hydrothermal reaction kettle for microwave-assisted hydrothermal treatment; Step 5: Cool the mixed slurry obtained by treatment in Step 4 to room temperature; Step 6: Perform solid-liquid separation on the cooled mixed slurry in Step 5. Among them, the separated liquid-phase product is discharged as waste liquid, and the separated solid-phase product is dried and then reused as an adsorbent.

[0008] According to at least one embodiment of the present application, the heavy metals contained in the acid mine wastewater are one or more of Cu, Pb, Zn, Cd, Mn, and Fe.

[0009] According to at least one embodiment of the present application, in the step 1, the alkaline solution added is a sodium hydroxide solution, the concentration of the sodium hydroxide solution is 0.1-0.3 mol / L, and the liquid-to-solid ratio is 3-10 mL:1 g.

[0010] According to at least one embodiment of the present application, in the step 2, heating and stirring the mixed slurry comprises: The mixed slurry is transported to a stirred heating hydrothermal reactor and stirred at a temperature of 50-90°C and a rotation speed of 200-600 r / min for 1-6 hours; preferably 70-90°C, 300-500 r / min and 2-5 hours; more preferably 90°C, 400 r / min and 3 hours.

[0011] According to at least one embodiment of the present application, in the step 4, the microwave-assisted hydrothermal treatment comprises: The temperature of the mixed slurry in the microwave hydrothermal reaction kettle is maintained at 100-370°C for 10-120 min; more preferably, the temperature is 130-200°C and the microwave hydrothermal reaction time is 10-120 min; further preferably, the temperature is 150°C and the microwave hydrothermal reaction time is 20 min.

[0012] According to at least one embodiment of the present application, in step six, drying the solid phase product comprises: The solid product was dried at 105±5°C for 12-24h.

[0013] This application has at least the following beneficial technical effects: 1) The method for harmless co - treatment of mine acid wastewater and incineration fly ash in this application uses the strong alkalinity of sodium hydroxide solution to modify the surface structure of waste incineration fly ash under low - temperature conditions, which is beneficial to the dissolution of elements such as calcium, silicon, and aluminum necessary for subsequent microwave hydrothermal synthesis of zeolite - like minerals. In addition, the alkalinity of the mixed slurry obtained from waste incineration fly ash and sodium hydroxide solution is used to neutralize the mine acid wastewater, adjusting the pH to near neutral. Further, microwave hydrothermal technology is used to deeply treat the mine acid wastewater and waste incineration fly ash. While simultaneously degrading organic pollutants such as dioxins in the fly ash, the heavy metals in the mine acid wastewater and incineration fly ash are effectively converted into the residual state, achieving the simultaneous stabilization of heavy metals. In summary, the treatment method in this application solves the problems of harmless and stable treatment of two kinds of hazardous wastes, mine acid wastewater and waste incineration fly ash, and the treated fly ash also has extremely strong stability and adsorption characteristics.

[0014] 2) The method for harmless co - treatment of mine acid wastewater and incineration fly ash in this application is more convenient to operate, including only two steps: alkaline pretreatment of fly ash and microwave hydrothermal treatment of incineration fly ash and mine acid wastewater. In addition, this application uses the silicon, aluminum, and calcium dissolved from fly ash to form zeolite - like minerals to stabilize heavy metal ions, without the need to add additional heavy metal stabilizers. Further, while achieving the stabilization of heavy metals, this application can also efficiently degrade persistent organic pollutants such as dioxins in the fly ash. Brief Description of the Drawings

[0015] Figure 1 It is the flow chart of the method for harmless co - treatment of mine acid wastewater and incineration fly ash in this application. Detailed Embodiments

[0016] To make the purpose, technical solutions, and advantages of the implementation of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the drawings in the embodiments of this application. In the drawings, the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions from beginning to end. The described embodiments are some, but not all, of the embodiments of this application. The embodiments described below by referring to the drawings are exemplary and are intended to explain this application, and should not be construed as a limitation of this application. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of this application.

[0017] Example 1: In this embodiment, the initial pH value of the mine acid wastewater is 2.43, and the types and concentrations of the main heavy metals it contains are as follows: Fe: 162.1 mg / L, Cu: 10.21 mg / L, Pb: 5.26 mg / L; the waste incineration fly ash is taken from the fly ash generated by fluidized bed incineration of domestic waste, and the dioxin toxicity equivalent in it is: 36.20 TEQ μg / g; the toxicity experiment of heavy metal leaching of the fly ash is carried out by using the "Solid Waste Leaching Toxicity Leaching Method - Acetic Acid Buffer Solution Method" (HJ / T 300-2007), and the heavy metal concentrations in the leachate are detected as follows: Zn: 38.26 mg / L, Pb: 0.37 mg / L, Cu: 12.26 mg / L, Cd: 0.42 mg / L, Cr: 2.10 mg / L, Ni: 0.28 mg / L.

[0018] As Figure 1 shown, the harmless co-disposal method of the mine acid wastewater and incineration fly ash in this embodiment includes the following steps: Step 1: At room temperature, accurately weigh 20 g of waste incineration fly ash, and mix the fly ash and 0.3 mol / L sodium hydroxide concentrated solution evenly according to the liquid-solid ratio of 5:1 mL / g to obtain a mixed slurry; Step 2: Transfer the mixed slurry to a stirred heating hydrothermal reactor, and react for 2 h under the conditions of a temperature of 70 °C and a stirring speed of 200 r / min; Step 3: After the reaction in Step 2 ends, add the mine acid wastewater to the obtained mixed slurry until the pH value of the mixed slurry is adjusted to neutral; Step 4: Transfer the mixed slurry in Step 3 to a microwave hydrothermal reaction kettle, and react for 40 min under the condition of a temperature of 140 °C; Step 5: Naturally cool the mixed slurry obtained in Step 4 to room temperature; Step 6: Perform solid-liquid separation on the cooled mixed slurry in Step 5 to obtain a hydrothermal solid-phase product and a hydrothermal liquid-phase product. Among them, the separated liquid-phase product is discharged as waste liquid, and the solid-phase product is dried at 100 ± 5 °C.

[0019] It also needs to be explained here that in Step 1, the strong alkalinity of the sodium hydroxide solution is used to modify the surface structure of the waste incineration fly ash at low temperature, mainly changing the specific surface area and pore volume of the incineration fly ash, making its specific surface area and pore volume larger, and making it easier to adsorb heavy metal ions in the co-treatment of acid wastewater.

[0020] Furthermore, the microwave hydrothermal treatment technology involved in Step 4 uses subcritical water as the reaction medium. Taking advantage of the characteristics of water in the subcritical state (T = 100 - 374 °C, P = 0.1 - 22.1 Mpa), such as fast movement acceleration, large ionic product constant, and high diffusion coefficient, it can be better miscible with organic substances, greatly improving the degradation rate of organic pollution. At the same time, water can change the dielectric properties of municipal solid waste incineration fly ash, enabling it to absorb microwaves well, significantly shortening the dissolution-recrystallization process of elements such as calcium, silicon, and aluminum in the fly ash, and thus effectively realizing the stabilization of toxic heavy metals. In addition, the microwave hydrothermal treatment technology also has advantages such as simple operation, high treatment efficiency, and low secondary pollution.

[0021] In addition, the reason for using a microwave hydrothermal reactor instead of a supercritical water heat treatment in Step 4 of this application is that when the supercritical water heat treatment technology is used to treat the fly ash and wastewater mixture, the wastewater generally contains a large amount of refractory organic pollutants. It mainly utilizes the changes in the density, viscosity, and dielectric constant of water molecules in the supercritical state to change the polarity of water, making it a good solvent for organic substances, and then realizing the degradation of organic pollutants. However, the wastewater involved in this application contains a large amount of metal ions. As the reaction temperature rises to near the critical temperature (~350 - 400 °C), the reaction medium will change from water to a supercritical metal fluid, which will cause the silicon, aluminum, and calcium dissolved from the fly ash to precipitate and crystallize rapidly during the supercritical gas-liquid separation process, hindering the nucleation of zeolite-like minerals and thus reducing the stabilization efficiency of heavy metals. The advantage of microwave hydrothermal technology over supercritical hydrothermal technology is mainly reflected in terms of energy consumption. The temperature of microwave hydrothermal reaction usually ranges from 100 - 200 °C, and the working power of its reactor is generally 1 kw, while the supercritical hydrothermal reaction temperature ≥ 374 °C, and the working power of its reactor ≥ 3 kw. Therefore, using microwave hydrothermal can significantly reduce energy consumption and operating costs.

[0022] Finally, the content of dioxins in the hydrothermal solid-phase product was analyzed by using a high-resolution gas chromatography / high-resolution mass spectrometry (HRGC / MS) instrument. The analysis experimental results showed that the dioxin toxicity equivalent in the hydrothermal solid-phase product was 1.52 ng-TEQ / g, which was 95.80% lower than that of the original fly ash; and the toxicity leaching experiment of heavy metals on the dried solid-phase product was carried out in accordance with the "Solid Waste Leaching Toxicity Leaching Method - Acetic Acid Buffer Solution Method" (HJ / T 300-2007). The leaching concentrations of heavy metals in the solid-phase product were as follows: Zn: 2.27 mg / L, Pb: 0.18 mg / L, Cu: 1.16 mg / L, Cd: 0.022 mg / L, Cr: 0.086 mg / L, Ni: 0.024 mg / L; furthermore, an inductively coupled plasma mass spectrometer (ICP-MS) was used to analyze the concentrations of heavy metals in the leaching solution and waste liquid. The pH of the hydrothermal liquid-phase product was 7.81, and its heavy metal concentrations were as follows: Zn: 1.42 mg / L, Pb: 0.86 mg / L, Cu: 0.32 mg / L, Cd: 0.042 mg / L, Cr: 0.057 mg / L, Ni: 0.036 mg / L; Fe: 4.12 mg / L.

[0023] In summary, the leaching concentrations of heavy metals in the hydrothermal solid-phase product after treatment were far lower than the limit values required by the "Pollution Control Standard for Domestic Waste Landfill" (GB16889-2008); the heavy metal concentrations in the hydrothermal liquid phase fully met the "Integrated Wastewater Discharge Standard" (GB8978-1996).

[0024] In addition, through the cation exchange capacity and heavy metal adsorption experiments on the hydrothermal solid-phase product, it was found that the cation exchange capacity of the incineration fly ash treated by the process of this example was 0.812 meq / g, which had good adsorption performance and fully had the application prospect of being recycled as an adsorbent.

[0025] Example 2: In this example, the initial pH value of the mine acid wastewater was 3.21, and the main types and concentrations of heavy metals it contained were: Fe: 126.1 mg / L, Mn: 6.21 mg / L, Pb: 3.41 mg / L; the waste incineration fly ash was from the fly ash generated by fluidized bed incineration of domestic waste, and the dioxin toxicity equivalent in it was: 40.81 TEQ μg / g; through the heavy metal toxicity leaching experiment on the fly ash, the heavy metal concentrations in the leaching solution were detected as: Zn: 16.32 mg / L, Pb: 0.35 mg / L, Cu: 6.21 mg / L, Cd: 0.16 mg / L, Cr: 0.85 mg / L, Ni: 0.46 mg / L.

[0026] Similarly, the method for harmless co-disposal of mine acid wastewater and incineration fly ash in this embodiment includes the following steps: Step 1: At room temperature, accurately weigh 20 g of waste incineration fly ash, and mix the fly ash and 0.2 mol / L sodium hydroxide concentrated solution evenly according to a liquid-solid ratio of 7:1 ml / g to obtain a mixed slurry; Step 2: Transfer the mixed slurry to a stirred hydrothermal reactor, and react for 4 h under the conditions of a temperature of 70 °C and a stirring speed of 300 r / min; Step 3: After the reaction in Step 2 ends, add the mine acid wastewater to the obtained mixed slurry until the pH value of the mixed slurry is adjusted to neutral; Step 4: Transfer the mixed slurry in Step 3 to a microwave hydrothermal reaction kettle, and react for 30 min under the condition of a temperature of 200 °C; Step 5: Naturally cool the mixed slurry treated in Step 4 to room temperature; Step 6: Perform solid-liquid separation on the cooled mixed slurry in Step 5 to obtain a hydrothermal solid-phase product and a hydrothermal liquid-phase product. Among them, the separated liquid-phase product is discharged as waste liquid, and the solid-phase product is dried at 100 ± 5 °C.

[0027] Finally, analyze the content of dioxins in the hydrothermal solid-phase product by using a high-resolution gas chromatography / high-resolution mass spectrometry HRGC / MS. The analysis experimental results show that the dioxin toxicity equivalent in the hydrothermal solid-phase product is 1.66 ng-TEQ / g, which is reduced by 95.93% compared with the original fly ash; and perform a heavy metal leaching toxicity experiment on the dried solid-phase product according to the "Solid Waste Leaching Toxicity Leaching Method Acetic Acid Buffer Solution Method" (HJ / T 300-2007). The heavy metal leaching concentrations in the solid-phase product are: Zn: 3.26 mg / L, Pb: 0.13 mg / L, Cu: 0.96 mg / L, Cd: 0.046 mg / L, Cr: 0.053 mg / L, Ni: 0.082 mg / L; further, analyze the heavy metal concentrations in the leaching solution and waste liquid by using an inductively coupled plasma mass spectrometer ICP-MS. The pH of the hydrothermal liquid-phase product is 8.16, and its heavy metal concentrations are: Zn: 1.62 mg / L, Pb: 0.79 mg / L, Cu: 0.44 mg / L, Cd: 0.032 mg / L, Cr: 0.061 mg / L, Ni: 0.091 mg / L, Fe: 5.63 mg / L, Mn: 0.62 mg / L.

[0028] Similarly, in this embodiment, the leaching concentration of heavy metals in the hydrothermal solid-phase product after treatment is much lower than the limit values required by the "Pollution Control Standard for Domestic Waste Landfill" (GB16889-2008); the concentration of heavy metals in the hydrothermal liquid phase fully meets the "Integrated Wastewater Discharge Standard" (GB8978-1996); in addition, through the cation exchange capacity and heavy metal adsorption experiments on the hydrothermal solid-phase product, it is known that the cation exchange capacity of the incineration fly ash treated by the process of this embodiment is 0.796 meq / g, which has good adsorption performance and fully has the application prospect of being recycled as an adsorbent.

[0029] Example 3: In this embodiment, the initial pH value of the mine acid wastewater is 2.96, and the main types and concentrations of heavy metals contained are: Fe: 141.8 mg / L, Mn: 7.32 mg / L, Pb: 3.41 mg / L, Cd: 1.32 mg / L; the incineration fly ash is from the fly ash generated by fluidized bed incineration of domestic waste, and the dioxin toxicity equivalent is: 39.12 TEQ μg / g; through the heavy metal leaching toxicity experiment on the fly ash, the heavy metal concentrations in the leachate are detected as: Zn: 40.51 mg / L, Pb: 0.66 mg / L, Cu: 18.61 mg / L, Cd: 0.28 mg / L, Cr: 0.54 mg / L, Ni: 0.39 mg / L.

[0030] Similarly, the harmless co-disposal method of the mine acid wastewater and incineration fly ash in this embodiment includes the following steps: Step 1: At room temperature, accurately weigh 20 g of incineration fly ash, and mix the fly ash and 0.1 mol / L sodium hydroxide concentrated solution evenly according to the liquid-solid ratio of 10:1 ml / g to obtain a mixed slurry; Step 2: Transfer the mixed slurry to a stirred hydrothermal reactor, and react for 6 h under the conditions of a temperature of 90 °C and a stirring speed of 400 r / min; Step 3: After the reaction in Step 2 ends, add the mine acid wastewater to the obtained mixed slurry until the pH value of the mixed slurry is adjusted to neutral; Step 4: Transfer the mixed slurry in Step 3 to a microwave hydrothermal reaction kettle and react for 20 min under the condition of a temperature of 150 °C; Step 5: Naturally cool the mixed slurry obtained in Step 4 to room temperature; Step 6: Perform solid-liquid separation on the cooled mixed slurry in Step 5 to obtain a hydrothermal solid-phase product and a hydrothermal liquid-phase product. Among them, the separated liquid-phase product is discharged as waste liquid, and the solid-phase product is dried at 100 ± 5 °C.

[0031] Finally, the content of dioxins in the hydrothermal solid-phase product was analyzed using a high-resolution gas chromatography / high-resolution mass spectrometry (HRGC / MS) instrument. The analysis results showed that the dioxin toxicity equivalent in the hydrothermal solid-phase product was 1.89 ng-TEQ / g, which was a 95.17% reduction compared to the original fly ash. In addition, a toxicity leaching experiment for heavy metals was conducted on the dried solid-phase product in accordance with the "Solid Waste Leaching Toxicity Leaching Method - Acetic Acid Buffer Solution Method" (HJ / T 300-2007). The leaching concentrations of heavy metals in the solid-phase product were as follows: Zn: 6.26 mg / L, Pb: 0.21 mg / L, Cu: 2.45 mg / L, Cd: 0.051 mg / L, Cr: 0.060 mg / L, Ni: 0.074 mg / L. Further, an inductively coupled plasma mass spectrometry (ICP-MS) was used to analyze the heavy metal concentrations in the leachate and waste liquid. The pH of the hydrothermal liquid-phase product was 8.23, and its heavy metal concentrations were as follows: Zn: 1.49 mg / L, Pb: 0.85 mg / L, Cu: 0.38 mg / L, Cd: 0.065 mg / L, Cr: 0.072 mg / L, Ni: 0.088 mg / L, Fe: 6.98 mg / L, Mn: 0.71 mg / L.

[0032] Similarly, in this embodiment, the leaching concentrations of heavy metals in the hydrothermal solid-phase product after treatment were far lower than the limits required by the "Pollution Control Standard for Domestic Waste Landfill Sites" (GB16889-2008); the heavy metal concentrations in the hydrothermal liquid phase fully met the "Integrated Wastewater Discharge Standard" (GB8978-1996). In addition, through cation exchange capacity and heavy metal adsorption experiments on the hydrothermal solid-phase product, it was found that the cation exchange capacity of the incineration fly ash treated by the process of this embodiment was 0.788 meq / g, with good adsorption performance, and it fully had the application prospect of being recycled as an adsorbent.

[0033] Example 4: In this embodiment, the initial pH value of the mine acid wastewater was 2.89, and the main types and concentrations of heavy metals it contained were: Fe: 132.6 mg / L, Cu: 9.84 mg / L, Pb: 2.98 mg / L; the waste incineration fly ash was from the fly ash generated by fluidized bed incineration of domestic waste, and the dioxin toxicity equivalent in it was: 39.26 TEQ μg / g; through a toxicity leaching experiment for heavy metals on the fly ash, the heavy metal concentrations in the leachate were detected as follows: Zn: 67.32 mg / L, Pb: 0.55 mg / L, Cu: 26.51 mg / L, Cd: 0.19 mg / L, Cr: 0.75 mg / L, Ni: 0.66 mg / L.

[0034] Similarly, the method for harmless co-disposal of mine acid wastewater and incineration fly ash in this embodiment includes the following steps: Step 1: At room temperature, accurately weigh 20 g of waste incineration fly ash, and mix the fly ash and 0.25 mol / L sodium hydroxide concentrated solution evenly according to a liquid-solid ratio of 6:1 mL / g to obtain a mixed slurry; Step 2: Transfer the mixed slurry to a stirred heating hydrothermal reactor, and react for 3 h under the conditions of a temperature of 60 °C and a stirring speed of 300 r / min; Step 3: After the reaction in Step 2 ends, add mine acid wastewater to the obtained mixed slurry until the pH value of the mixed slurry is adjusted to neutral; Step 4: Transfer the mixed slurry in Step 3 to a microwave hydrothermal reaction kettle, and react for 30 min under the condition of a temperature of 350 °C; Step 5: Naturally cool the mixed slurry obtained in Step 4 to room temperature; Step 6: Perform solid-liquid separation on the cooled mixed slurry in Step 5 to obtain a hydrothermal solid-phase product and a hydrothermal liquid-phase product. Among them, the separated liquid-phase product is discharged as waste liquid, and the solid-phase product is dried at 100 ± 5 °C.

[0035] Finally, analyze the content of dioxins in the hydrothermal solid-phase product by using a high-resolution gas chromatography / high-resolution mass spectrometry HRGC / MS. The analysis experimental results show that the dioxin toxicity equivalent in the hydrothermal solid-phase product is 0.96 ng-TEQ / g, which is reduced by 97.55% compared with the original fly ash; and perform a heavy metal leaching toxicity experiment on the dried solid-phase product according to the "Solid Waste Leaching Toxicity Leaching Method Acetic Acid Buffer Solution Method" (HJ / T 300-2007). The heavy metal leaching concentrations in the solid-phase product are: Zn: 9.07 mg / L, Pb: 0.091 mg / L, Cu: 5.69 mg / L, Cd: 0.016 mg / L, Cr: 0.035 mg / L, Ni: 0.078 mg / L; further, analyze the heavy metal concentrations in the leaching solution and waste liquid by using an inductively coupled plasma mass spectrometer ICP-MS. The pH of the hydrothermal liquid-phase product is 8.09, and its heavy metal concentrations are: Zn: 1.33 mg / L, Pb: 0.65 mg / L, Cu: 0.39 mg / L, Cd: 0.018 mg / L, Cr: 0.054 mg / L, Ni: 0.078 mg / L, Fe: 5.28 mg / L, Mn: 0.58 mg / L.

[0036] Similarly, in this embodiment, the leaching concentration of heavy metals in the hydrothermal solid-phase product after treatment is much lower than the limit required by the "Pollution Control Standard for Domestic Waste Landfills" (GB16889-2008); the concentration of heavy metals in the hydrothermal liquid phase fully meets the "Integrated Wastewater Discharge Standard" (GB8978-1996); in addition, through the cation exchange capacity and heavy metal adsorption experiments on the hydrothermal solid-phase product, it can be seen that the cation exchange capacity of the incineration fly ash treated by the process of this embodiment is 0.857 meq / g, which has good adsorption performance and fully has the application prospect of being recycled as an adsorbent.

[0037] However, it should be noted here that the temperature in the microwave hydrothermal reactor in Example 4 is 350 °C. Although the harmless treatment of incineration fly ash and mine acid can also be achieved synchronously, compared with Examples 1-3, the too high reaction temperature in Example 4 will correspondingly increase the energy consumption.

[0038] It can be seen from the above 4 embodiments that the method for co-disposing mine acid wastewater and incineration fly ash harmlessly in this application can effectively achieve the synchronous removal of harmful substances in mine acid wastewater and waste incineration fly ash, and has the advantages of simple operation, high disposal efficiency, and low disposal cost. In addition, the treated hydrothermal solid-phase product can also be recycled as an adsorbent, making the value created by this application more adaptable to the national conditions of our country, and providing a theoretical basis and technical support for the industrial development of the harmless treatment and resource utilization of mine acid wastewater and waste incineration fly ash.

[0039] The above is only the specific implementation manner of this application, but the protection scope of this application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in this application should be covered by the protection scope of this application. Therefore, the protection scope of this application should be subject to the protection scope of the claimed rights.

Claims

1. A method for harmless co-disposal of acid mine wastewater and incineration fly ash, characterized in that: The steps include: Step 1: adding an alkaline solution to the incineration fly ash to be treated at room temperature to obtain a mixed slurry; Step 2, heating and stirring the mixed slurry obtained in step 1; Step 3, adding acid mine wastewater to the mixed slurry obtained by stirring in step 2 until the pH value of the mixed slurry is adjusted to neutral; Step 4: transferring the neutral mixed slurry obtained in step 3 to a microwave hydrothermal reactor for microwave-assisted hydrothermal treatment; Step 5, cooling the mixed slurry obtained in step 4 to room temperature; Step six, performing solid-liquid separation on the mixed slurry after cooling in step five, wherein the separated liquid product is discharged as waste liquid, and the separated solid product is dried and reused as an adsorbent.

2. The method for harmless co-disposal of acid mine wastewater and incineration fly ash according to claim 1, characterized in that: The heavy metals contained in the acid mine wastewater are one or more of Cu, Pb, Zn, Cd, Mn and Fe.

3. The method for harmless co-disposal of acid mine wastewater and incineration fly ash according to claim 2, characterized in that: In the step 1, the alkaline solution added is a sodium hydroxide solution, the concentration of the sodium hydroxide solution is 0.1-0.3 mol / L, and the liquid-solid ratio is 3-10 mL:1 g.

4. The method for harmless co-disposal of acid mine wastewater and incineration fly ash according to claim 3, characterized in that: In the step 2, the mixed slurry is subjected to heating and stirring treatment, which includes: The mixed slurry is transported to a stirred heating hydrothermal reactor and stirred for 1-6 hours at a temperature of 50-90° C. and a rotation speed of 200-600 r / min.

5. The method for harmless co-disposal of acid mine wastewater and incineration fly ash according to claim 4, characterized in that: The mixed slurry is subjected to heating and stirring treatment, comprising: The mixed slurry is transported to a stirring heating hydrothermal reactor and stirred for 2-5 hours at a temperature of 70-90° C. and a rotation speed of 300-500 r / min.

6. According to the method for harmless co-disposal of acid mine wastewater and incineration fly ash according to claim 5, the heating and stirring treatment of the mixed slurry comprises: The mixed slurry was transported to a stirred hydrothermal reactor and stirred for 3 hours at a temperature of 90° C. and a rotation speed of 400 r / min.

7. The method for harmless co-disposal of acid mine wastewater and incineration fly ash according to claim 4, characterized in that: In the step 4, the microwave-assisted hydrothermal treatment comprises: The temperature of the mixed slurry in the microwave hydrothermal reaction kettle is maintained at 100-370° C. for 10-120 min.

8. The method for harmless co-disposal of acid mine wastewater and incineration fly ash according to claim 7, characterized in that: The microwave-assisted hydrothermal treatment comprises: The temperature of the mixed slurry in the microwave hydrothermal reaction kettle is maintained at 130-200° C. for 15-60 min.

9. The method for harmless co-disposal of acid mine wastewater and incineration fly ash according to claim 7, characterized in that: In the step 4, the microwave-assisted hydrothermal treatment comprises: The temperature of the mixed slurry in the microwave hydrothermal reaction kettle was maintained at 150° C. for 20 min.

10. The method for harmless co-disposal of acid mine wastewater and incineration fly ash according to claim 7, characterized in that: In the step six, drying the solid phase product comprises: The solid product was dried at 105±5°C for 12-24h.

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