Calcium chloride modified biochar material as well as preparation method and application thereof

Abstract

The invention provides a calcium chloride modified biochar material as well as a preparation method and application thereof, and belongs to the technical field of wastewater treatment. The invention provides a preparation method of a calcium chloride modified biochar material. The preparation method comprises the following steps: uniformly mixing sunflower discs, fly ash and calcium chloride, and granulating to obtain a granular biochar raw material; and aging the granular biochar raw material, and calcining at 500-700 DEG C to obtain the calcium chloride modified biochar. The calcium chloride modified biochar material prepared by the invention has large particles, is easy to separate from water, has excellent adsorption performance, and can be used for buffering the pH value of acidic mine water and treating iron and sulfate ions in the water.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and more specifically to a calcium chloride modified biochar material and a preparation method and application thereof. Background Art

[0002] Acid mine drainage (AMD) generally refers to mine water with a pH value of less than 6. Sulfide ores that exist stably in a reducing environment will be left in the goaf after coal mining, exposed to the air or immersed in oxygen-rich water, and will form acid mine water rich in sulfate ions and with a low pH value (the pH value can reach below 2 in severe areas) through a series of oxidation reactions. The presence of sulfate in water can directly affect drinking water, making it bitter. Long-term drinking can also cause obvious physiological harm to mammals. For example, long-term intake of high-concentration sulfate ions by humans may cause symptoms such as diarrhea and indigestion. Therefore, the "Standards for Drinking Water Quality" stipulates that SO4 in drinking water 2 -The concentration should not exceed 250mg / L. Excessive SO4 in water 2 -It will also cause the natural sulfur cycle to be disrupted, causing serious harm to the ecosystem.

[0003] In recent years, the treatment of acid mine water has been widely studied, and new materials and methods have emerged one after another. However, the treatment of mine water with high sulfate concentration still has disadvantages such as high material production cost, low working capacity, and poor operability. Biochar has a wide range of sources, well-developed pores, and rich polar functional groups. It can adsorb pollutants in water bodies through mechanisms such as physical adsorption, electrostatic action, ion exchange, complex reaction, and chemical precipitation. Compared with ordinary activated carbon adsorbents, biochar is not activated and has lower costs; but when biochar is used alone, the adsorption selectivity is not high, and the type of carrier, reaction temperature, and type of adsorbed ions in the preparation process have a great influence on the adsorption effect.

[0004] Oh et al. used biochar prepared from poultry manure to treat AMD produced from abandoned copper mines in South Korea. The results showed that the high concentrations of Fe, Al, Mn, Cu, and As contained in AMD were completely removed, while Zn, Mn, SO4 2-removal rates of 99%, 61% and 31% respectively; Giachini et al. found that compared with the original AMD, biochar rich in cow dung can promote 41% sulfate reduction, and compared with other treatments (AMD sediment, sludge), sulfate is reduced by 39%; Ao Hanting et al. used grapefruit peel as raw material, impregnated with zirconium oxychloride, precipitated with ammonia water, and synthesized modified grapefruit peel biochar adsorbent by room temperature chemical method, and the absorption of sulfate in water can reach 12.33 mg / g. Although a large number of modified biochars have been studied for high-sulfur mine water, the research on biochar treatment of high-sulfur mine water is still only in the laboratory stage due to the small particles, insufficient strength, difficulty in separation from water and poor sulfate adsorption performance of the prepared biochar. On this basis, the research and development of a modified biochar with large particles, easy separation from water and strong adsorption capacity is of great significance for the efficient treatment of high-sulfur mine water. Summary of the invention

[0005] In view of the above problems, the present invention provides a calcium chloride modified biochar material and a preparation method and application thereof. The calcium chloride modified biochar material prepared by the present invention has large particles, is easy to separate from water, has excellent adsorption properties, and can be used to buffer the pH of acidic mine water and treat iron and sulfate ions in water.

[0006] The present invention provides a method for preparing a calcium chloride modified biochar material, which is characterized by comprising the following steps:

[0007] The sunflower disc, fly ash and calcium chloride are uniformly mixed and then granulated to obtain granular biochar raw material.

[0008] The granular biochar raw material is aged and then calcined at 500°C to 700°C to obtain calcium chloride modified biochar.

[0009] For example, the calcination temperature is 500°C, 550°C, 600°C, 650°C, 700°C, etc.

[0010] In a preferred embodiment of the present invention, the mass ratio of sunflower disc to fly ash is 2 to 4:1. For example, the mass ratio of sunflower disc to fly ash is 2:1, 2.5:1, 3:1, 3.5:1, 4:1, etc., but is not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0011] In a preferred embodiment of the present invention, the amount of calcium chloride added is 25% to 100% of the total mass of the sunflower disc and fly ash. For example, the amount of calcium chloride added is 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, etc., but is not limited to the listed values. Other values ​​not listed in the above numerical range are also applicable. Further, the amount of calcium chloride added is 3% to 100% of the total mass of the sunflower disc and fly ash; further, the amount of calcium chloride added is 100% of the total mass of the sunflower disc and fly ash.

[0012] In a preferred embodiment of the present invention, the aging temperature is 30°C to 50°C, and the aging time is 16h to 24h. For example, the aging temperature is 30°C, 35°C, 40°C, 4550°C, etc., and the aging time is 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, 24h, etc., but is not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0013] In a preferred embodiment of the present invention, the calcination temperature is 600°C.

[0014] In a preferred embodiment of the present invention, the calcination time is 90 min to 150 min, for example, the calcination time is 90 min, 100 min, 110 min, 120 min, 130 min, 140 min, 150 min, etc., but is not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0015] In a preferred embodiment of the present invention, the particle size of the granular biochar raw material is 2 mm to 3 mm.

[0016] The second object of the present invention is to provide a calcium chloride-modified biochar material prepared by the above preparation method.

[0017] The third object of the present invention is to provide an application of the above-mentioned calcium chloride modified biochar material in the remediation of sulfuric acid mine water pollution, adding the calcium chloride modified biochar material to the sulfuric acid mine water to be treated, adsorbing at 15°C to 35°C, and completing the remediation of the sulfuric acid mine water to be treated. For example, the temperature during adsorption is 15°C, 20°C, 25°C, 30°C, 35°C, etc., but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0018] In a preferred embodiment of the present invention, the ratio of the sulfuric acid mine water to be treated and the calcium chloride modified biochar material is 1g:60ml.

[0019] The concentration of the sulfuric acid mine water to be treated is 500 mg / L to 3000 mg / L. For example, the concentration of the sulfuric acid mine water to be treated is 500 mg / L, 1000 mg / L, 1500 mg / L, 2000 mg / L, 2500 mg / L, 3000 mg / L, etc., but is not limited to the listed values. Other values ​​not listed within the above numerical range are also applicable.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The present invention provides a preparation method, repair method and application of a calcium chloride modified biochar material. By using fly ash and calcium chloride to modify biochar to obtain calcium chloride modified biochar, the adsorption sites and specific surface area of ​​the material can be increased, thereby increasing the adsorption capacity of the biochar material for iron and sulfate ions. The biochar raw material is granulated and calcined to obtain a calcium chloride modified biochar material with both high specific surface area and porosity and alkalinity. This material can not only effectively adsorb iron and sulfate ions in water bodies, but also use its own alkalinity to neutralize pH and precipitate pollutants, greatly improving the treatment effect of acidic mine water. The present invention regenerates and recycles the biochar material that adsorbs pollutants using hydrochloric acid, in order to reduce the cost of adsorption and repair.

[0022] (2) The calcium chloride modified biochar material prepared by the present invention has extremely low heavy metal leaching toxicity, is environmentally friendly, and effectively utilizes solid waste materials such as fly ash and sunflower discs without secondary pollution.

[0023] (3) The material formula of the present invention is simple and easy to obtain locally; the preparation method is simple and easy to implement; the solid waste ratio is high, environmentally friendly and low-cost; the proportion and amount of raw materials can be adjusted according to the technical requirements of different engineering sites, and can be used for the treatment of mine water pollution in operating or closed coal mines. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a physical picture of the granular biochar raw material obtained in the biochar granulation process of Example 1.

[0025] Figure 2 This is the infrared spectrum of the calcium chloride-modified biochar material prepared in Example 1 and after adsorbing sulfate.

[0026] Figure 3 This is a graph showing the adsorption capacity of different calcium chloride-modified biochar materials prepared in the present invention for sulfate.

[0027] Figure 4 This is a graph showing the effect of different concentrations and different adsorption temperatures on the sulfate adsorption performance of the calcium chloride modified biochar material prepared in Example 1.

[0028] Figure 5 This is a graph showing the effect of reaction time on the sulfate adsorption performance of the calcium chloride modified biochar material prepared in Example 1.

[0029] Figure 6 This is the XRD pattern of the calcium chloride modified biochar material prepared in Example 1.

[0030] Figure 7 This is a graph showing the adsorption of sulfate by biochar materials modified with different raw materials prepared in Example 1 and Comparative Examples 4 to 7.

[0031] Figure 8 This is a diagram showing the in-situ remediation mechanism of highly sulfated mine water using the calcium chloride-modified biochar material prepared in the present invention. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] In view of the problems in the background technology, the present invention combines sunflower discs, fly ash and CaCl2 for use. Sunflower discs are agricultural solid waste, which can form biochar with a large specific surface area after calcination and has strong adsorption performance; fly ash is a common coal-based solid waste, which is easy to obtain and has low cost. It is mostly alkaline, porous and has a large specific surface area. After calcining with sunflower discs, the porosity of biochar can be greatly improved, and the adsorption performance of pollutants can be further improved. After the solid waste powder is calcined together with CaCl2, its adsorption of SO4 2- The adsorption effect is greatly improved, and it has a certain buffering effect on the pH of the solution. In summary, the present invention uses sunflower discs as the main raw material and adds fly ash and CaCl2 to calcine them together as PRB filling materials to treat polluted water in the mining area in situ. While neutralizing the pH of acidic mine water, it can also effectively adsorb SO4 2- And other pollutants, so as to achieve the goal of treating waste with waste.

[0034] Example 1

[0035] According to the mass ratio of sunflower disc to fly ash of 2:1, 200g of sunflower disc and 100g of fly ash were weighed and mixed evenly to obtain solid waste powder.

[0036] According to the mass ratio of solid waste powder to CaCl2 of 2:1, 150g of CaCl2 was weighed, and the weighed CaCl2 was added into water to prepare a CaCl2 solution with a mass concentration of 30%. The prepared CaCl2 solution was evenly mixed with the solid waste powder, and then put into a granulator for granulation. The speed of the granulator was set to 30r / min and the granulation time was 10min, thereby obtaining a granular biochar raw material with a particle size of 2-3mm. The actual picture is as follows Figure 1 shown.

[0037] The granular biochar raw material was aged at 50°C for 16 hours and then placed in a crucible. The crucible was placed in a tubular furnace for carbonization and calcined at 600°C for 2 hours. After cooling, it was taken out, ground and sieved to prepare calcium chloride modified biochar, recorded as CaCl2-BC.

[0038] Example 2

[0039] According to the mass ratio of sunflower disc to fly ash of 2:1, 200g of sunflower disc and 100g of fly ash were weighed and mixed evenly to obtain solid waste powder.

[0040] According to the mass ratio of solid waste powder to CaCl2 of 1:1, 300g of CaCl2 was weighed, and the weighed CaCl2 was added into water to prepare a CaCl2 solution with a mass concentration of 30%. The prepared CaCl2 solution was evenly mixed with the solid waste powder, and then put into a granulator for granulation. The speed of the granulator was set to 30r / min and the granulation time was 10min, thereby obtaining a granular biochar raw material with a particle size of 2 to 3mm.

[0041] The granular biochar raw material was aged at 50°C for 16 hours and then placed in a crucible. The crucible was placed in a tubular furnace for carbonization and calcined at a constant temperature of 600°C for 2 hours. After cooling, it was taken out, ground and sieved to prepare calcium chloride modified biochar.

[0042] Example 3

[0043] According to the mass ratio of sunflower disc to fly ash of 2:1, 200g of sunflower disc and 100g of fly ash were weighed and mixed evenly to obtain solid waste powder.

[0044] According to the mass ratio of solid waste powder to CaCl2 of 4:1, 75g of CaCl2 was weighed, and the weighed CaCl2 was added into water to prepare a CaCl2 solution with a mass concentration of 30%. The prepared CaCl2 solution was evenly mixed with the solid waste powder, and then put into a granulator for granulation. The speed of the granulator was set to 30r / min and the granulation time was 10min, thereby obtaining a granular biochar raw material with a particle size of 2 to 3mm.

[0045] The granular biochar raw material was aged at 50°C for 16 hours and then placed in a crucible. The crucible was placed in a tubular furnace for carbonization and calcined at a constant temperature of 600°C for 2 hours. After cooling, it was taken out, ground and sieved to prepare calcium chloride modified biochar.

[0046] Example 4

[0047] According to the mass ratio of sunflower disc to fly ash of 2:1, 200g of sunflower disc and 100g of fly ash were weighed and mixed evenly to obtain solid waste powder.

[0048] According to the mass ratio of solid waste powder to CaCl2 of 2:1, 150g of CaCl2 was weighed, and the weighed CaCl2 was added into water to prepare a CaCl2 solution with a mass concentration of 30%. The prepared CaCl2 solution was evenly mixed with the solid waste powder, and then put into a granulator for granulation. The speed of the granulator was set to 30r / min and the granulation time was 10min, thereby obtaining a granular biochar raw material with a particle size of 2 to 3mm.

[0049] The granular biochar raw material was aged at 50°C for 16 hours and then placed in a crucible. The crucible was placed in a tubular furnace for carbonization and calcined at a constant temperature of 500°C for 2 hours. After cooling, it was taken out, ground and sieved to prepare calcium chloride modified biochar.

[0050] Example 5

[0051] According to the mass ratio of sunflower disc to fly ash of 2:1, 200g of sunflower disc and 100g of fly ash were weighed and mixed evenly to obtain solid waste powder.

[0052] According to the mass ratio of solid waste powder to CaCl2 of 1:1, 300g of CaCl2 was weighed, and the weighed CaCl2 was added into water to prepare a CaCl2 solution with a mass concentration of 30%. The prepared CaCl2 solution was evenly mixed with the solid waste powder, and then put into a granulator for granulation. The speed of the granulator was set to 30r / min and the granulation time was 10min, thereby obtaining a granular biochar raw material with a particle size of 2 to 3mm.

[0053] The granular biochar raw material was aged at 50°C for 16 hours and then placed in a crucible. The crucible was placed in a tubular furnace for carbonization and calcined at a constant temperature of 500°C for 2 hours. After cooling, it was taken out, ground and sieved to prepare calcium chloride modified biochar.

[0054] Example 6

[0055] According to the mass ratio of sunflower disc to fly ash of 2:1, 200g of sunflower disc and 100g of fly ash were weighed and mixed evenly to obtain solid waste powder.

[0056] According to the mass ratio of solid waste powder to CaCl2 of 4:1, 75g of CaCl2 was weighed, and the weighed CaCl2 was added into water to prepare a CaCl2 solution with a mass concentration of 30%. The prepared CaCl2 solution was evenly mixed with the solid waste powder, and then put into a granulator for granulation. The speed of the granulator was set to 30r / min and the granulation time was 10min, thereby obtaining a granular biochar raw material with a particle size of 2 to 3mm.

[0057] The granular biochar raw material was aged at 50°C for 16 hours and then placed in a crucible. The crucible was placed in a tubular furnace for carbonization and calcined at a constant temperature of 500°C for 2 hours. After cooling, it was taken out, ground and sieved to prepare calcium chloride modified biochar.

[0058] Example 7

[0059] According to the mass ratio of sunflower disc to fly ash of 2:1, 200g of sunflower disc and 300g of fly ash were weighed and mixed evenly to obtain solid waste powder.

[0060] According to the mass ratio of solid waste powder to CaCl2 of 2:1, 150g of CaCl2 was weighed, and the weighed CaCl2 was added into water to prepare a CaCl2 solution with a mass concentration of 30%. The prepared CaCl2 solution was evenly mixed with the solid waste powder, and then put into a granulator for granulation. The speed of the granulator was set to 30r / min and the granulation time was 10min, thereby obtaining a granular biochar raw material with a particle size of 2 to 3mm.

[0061] The granular biochar raw material was aged at 50°C for 16 hours and then placed in a crucible. The crucible was placed in a tubular furnace for carbonization and calcined at 700°C for 2 hours. After cooling, the raw material was taken out, ground and sieved to prepare calcium chloride modified biochar.

[0062] Example 8

[0063] According to the mass ratio of sunflower disc to fly ash of 2:1, 200g of sunflower disc and 100g of fly ash were weighed and mixed evenly to obtain solid waste powder.

[0064] According to the mass ratio of solid waste powder to CaCl2 of 1:1, 300g of CaCl2 was weighed, and the weighed CaCl2 was added into water to prepare a CaCl2 solution with a mass concentration of 30%. The prepared CaCl2 solution was evenly mixed with the solid waste powder, and then put into a granulator for granulation. The speed of the granulator was set to 30r / min and the granulation time was 10min, thereby obtaining a granular biochar raw material with a particle size of 2 to 3mm.

[0065] The granular biochar raw material was aged at 50°C for 16 hours and then placed in a crucible. The crucible was placed in a tubular furnace for carbonization and calcined at 700°C for 2 hours. After cooling, the raw material was taken out, ground and sieved to prepare calcium chloride modified biochar.

[0066] Example 9

[0067] According to the mass ratio of sunflower disc to fly ash of 2:1, 200g of sunflower disc and 100g of fly ash were weighed and mixed evenly to obtain solid waste powder.

[0068] According to the mass ratio of solid waste powder to CaCl2 of 4:1, 75g of CaCl2 was weighed, and the weighed CaCl2 was added into water to prepare a CaCl2 solution with a mass concentration of 30%. The prepared CaCl2 solution was evenly mixed with the solid waste powder, and then put into a granulator for granulation. The speed of the granulator was set to 30r / min and the granulation time was 10min, thereby obtaining a granular biochar raw material with a particle size of 2 to 3mm.

[0069] The granular biochar raw material was aged at 50°C for 16 hours and then placed in a crucible. The crucible was placed in a tubular furnace for carbonization and calcined at 700°C for 2 hours. After cooling, the raw material was taken out, ground and sieved to prepare calcium chloride modified biochar.

[0070] Example 10

[0071] According to the mass ratio of sunflower disc to fly ash of 3:1, 300g of sunflower disc and 100g of fly ash were weighed and mixed evenly to obtain solid waste powder.

[0072] According to the mass ratio of solid waste powder to CaCl2 of 3:1, 133g of CaCl2 was weighed, and the weighed CaCl2 was added into water to prepare a CaCl2 solution with a mass concentration of 30%. The prepared CaCl2 solution was evenly mixed with the solid waste powder, and then put into a granulator for granulation. The speed of the granulator was set to 30r / min and the granulation time was 10min, thereby obtaining a granular biochar raw material with a particle size of 2 to 3mm.

[0073] The granular biochar raw material was aged at 30°C for 24 hours and then placed in a crucible. The crucible was placed in a tubular furnace for carbonization and calcined at 500°C for 150 minutes. After cooling, the raw material was taken out, ground and sieved to prepare calcium chloride modified biochar.

[0074] Embodiment 11

[0075] According to the mass ratio of sunflower disc to fly ash of 4:1, 200 g of sunflower disc and 50 g of fly ash were weighed and mixed evenly to obtain solid waste powder.

[0076] According to the mass ratio of solid waste powder to CaCl2 of 1:1, 250g of CaCl2 was weighed, and the weighed CaCl2 was added into water to prepare a CaCl2 solution with a mass concentration of 30%. The prepared CaCl2 solution was evenly mixed with the solid waste powder, and then put into a granulator for granulation. The speed of the granulator was set to 30r / min and the granulation time was 10min, thereby obtaining a granular biochar raw material with a particle size of 2 to 3mm.

[0077] The granular biochar raw material was aged at 40°C for 20 hours and then placed in a crucible. The crucible was placed in a tubular furnace for carbonization and calcined at 700°C for 90 minutes. After cooling, the raw material was taken out, ground and sieved to prepare calcium chloride modified biochar.

[0078] Comparative Example 1

[0079] According to the mass ratio of sunflower disc to fly ash of 2:1, 200g of sunflower disc and 100g of fly ash were weighed and mixed evenly to obtain solid waste powder.

[0080] According to the mass ratio of solid waste powder to CaCl2 of 2:1, 150g of CaCl2 was weighed, and the weighed CaCl2 was added into water to prepare a CaCl2 solution with a mass concentration of 30%. The prepared CaCl2 solution was evenly mixed with the solid waste powder, and then put into a granulator for granulation. The speed of the granulator was set to 30r / min and the granulation time was 10min, thereby obtaining a granular biochar raw material with a particle size of 2 to 3mm.

[0081] The granular biochar raw material was aged at 50°C for 16 hours and then placed in a crucible. The crucible was placed in a tubular furnace for carbonization and calcined at a constant temperature of 300°C for 2 hours. After cooling, the raw material was taken out, ground and sieved to prepare calcium chloride modified biochar.

[0082] Comparative Example 2

[0083] According to the mass ratio of sunflower disc to fly ash of 2:1, 200g of sunflower disc and 100g of fly ash were weighed and mixed evenly to obtain solid waste powder.

[0084] According to the mass ratio of solid waste powder to CaCl2 of 1:1, 300g of CaCl2 was weighed, and the weighed CaCl2 was added into water to prepare a CaCl2 solution with a mass concentration of 30%. The prepared CaCl2 solution was evenly mixed with the solid waste powder, and then put into a granulator for granulation. The speed of the granulator was set to 30r / min and the granulation time was 10min, thereby obtaining a granular biochar raw material with a particle size of 2 to 3mm.

[0085] The granular biochar raw material was aged at 50°C for 16 hours and then placed in a crucible. The crucible was placed in a tubular furnace for carbonization and calcined at a constant temperature of 300°C for 2 hours. After cooling, the raw material was taken out, ground and sieved to prepare calcium chloride modified biochar.

[0086] Comparative Example 3

[0087] According to the mass ratio of sunflower disc to fly ash of 2:1, 200g of sunflower disc and 100g of fly ash were weighed and mixed evenly to obtain solid waste powder.

[0088] According to the mass ratio of solid waste powder to CaCl2 of 4:1, 75g of CaCl2 was weighed, and the weighed CaCl2 was added into water to prepare a CaCl2 solution with a mass concentration of 30%. The prepared CaCl2 solution was evenly mixed with the solid waste powder, and then put into a granulator for granulation. The speed of the granulator was set to 30r / min and the granulation time was 10min, thereby obtaining a granular biochar raw material with a particle size of 2 to 3mm.

[0089] The granular biochar raw material was aged at 50°C for 16 hours and then placed in a crucible. The crucible was placed in a tubular furnace for carbonization and calcined at a constant temperature of 300°C for 2 hours. After cooling, the raw material was taken out, ground and sieved to prepare calcium chloride modified biochar.

[0090] Comparative Example 4

[0091] According to the mass ratio of lotus pod powder to fly ash of 2:1, 200g of lotus pod powder and 100g of fly ash were weighed and mixed evenly to obtain solid waste powder.

[0092] According to the mass ratio of solid waste powder to CaCl2 of 2:1, 150g of CaCl2 was weighed, and the weighed CaCl2 was added into water to prepare a CaCl2 solution with a mass concentration of 30%. The prepared CaCl2 solution was evenly mixed with the solid waste powder, and then put into a granulator for granulation. The speed of the granulator was set to 30r / min and the granulation time was 10min, thereby obtaining a granular biochar raw material with a particle size of 2 to 3mm.

[0093] The granular biochar raw material was aged at 50°C for 16 hours and then placed in a crucible. The crucible was placed in a tubular furnace for carbonization and calcined at 600°C for 2 hours. After cooling, it was taken out, ground and sieved to prepare calcium chloride modified biochar, which was recorded as CaCl2-LPBC.

[0094] Comparative Example 5

[0095] According to the mass ratio of rice husk powder to fly ash of 2:1, 200g of rice husk powder and 100g of fly ash were weighed and mixed evenly to obtain solid waste powder.

[0096] According to the mass ratio of solid waste powder to CaCl2 of 2:1, 150g of CaCl2 was weighed, and the weighed CaCl2 was added into water to prepare a CaCl2 solution with a mass concentration of 30%. The prepared CaCl2 solution was evenly mixed with the solid waste powder, and then put into a granulator for granulation. The speed of the granulator was set to 30r / min and the granulation time was 10min, thereby obtaining a granular biochar raw material with a particle size of 2 to 3mm.

[0097] The granular biochar raw material was aged at 50°C for 16 hours and then placed in a crucible. The crucible was placed in a tubular furnace for carbonization and calcined at 600°C for 2 hours. After cooling, it was taken out, ground and sieved to prepare calcium chloride modified biochar, which was recorded as CaCl2-DKBC.

[0098] Comparative Example 6

[0099] According to the mass ratio of corn cob powder to fly ash of 2:1, 200g corn cob powder and 100g fly ash were weighed and mixed evenly to obtain solid waste powder.

[0100] According to the mass ratio of solid waste powder to CaCl2 of 2:1, 150g of CaCl2 was weighed, and the weighed CaCl2 was added into water to prepare a CaCl2 solution with a mass concentration of 30%. The prepared CaCl2 solution was evenly mixed with the solid waste powder, and then put into a granulator for granulation. The speed of the granulator was set to 30r / min and the granulation time was 10min, thereby obtaining a granular biochar raw material with a particle size of 2 to 3mm.

[0101] The granular biochar raw material was aged at 50°C for 16 hours and then placed in a crucible. The crucible was placed in a tubular furnace for carbonization and calcined at 600°C for 2 hours. After cooling, it was taken out, ground and sieved to prepare calcium chloride modified biochar, which was recorded as CaCl2-YMXBC.

[0102] Comparative Example 7

[0103] According to the mass ratio of yellow bamboo powder to fly ash of 2:1, 200g of yellow bamboo powder and 100g of fly ash were weighed and mixed evenly to obtain solid waste powder.

[0104] According to the mass ratio of solid waste powder to CaCl2 of 2:1, 150g of CaCl2 was weighed, and the weighed CaCl2 was added into water to prepare a CaCl2 solution with a mass concentration of 30%. The prepared CaCl2 solution was evenly mixed with the solid waste powder, and then put into a granulator for granulation. The speed of the granulator was set to 30r / min and the granulation time was 10min, thereby obtaining a granular biochar raw material with a particle size of 2 to 3mm.

[0105] The granular biochar raw material was aged at 50°C for 16 hours and then placed in a crucible. The crucible was placed in a tubular furnace for carbonization and calcined at 600°C for 2 hours. After cooling, it was taken out, ground and sieved to prepare calcium chloride modified biochar, which was recorded as CaCl2-HZBC.

[0106] Based on the fact that the slurry solidification environment in actual engineering applications is acidic mine water, the raw materials and test blocks were tested for heavy metal leaching toxicity according to the "Solid Waste Leaching Toxicity Leaching Method-Sulfuric Acid and Nitric Acid Method" (HJ / T 299-2007). A mixture of concentrated sulfuric acid and concentrated nitric acid with a mass ratio of 2:1 was added to reagent water to prepare the leaching agent, and the pH value of the solution was 3.20±0.05. Weigh 6-10g of sample and place it in an extraction bottle, add the leaching agent at a liquid-solid ratio of 10mL:1g, cover the bottle cap tightly, fix it on the flip-type oscillating device, adjust the speed to 30r / min, and oscillate at 23℃ for 18h. Install the filter membrane on the pressure filter, rinse the filter and filter membrane with dilute nitric acid, discard the elution, filter and collect the leachate. According to the “Hazardous Waste Identification Standard - Leaching Toxicity Identification” (GB 5085.3-2007), the heavy metal concentration in the leachate was measured and identified. The heavy metal leaching toxicity test results of the raw materials and the prepared calcium chloride modified biochar test blocks are shown in Table 1.

[0107] Table 1 Contents of relevant toxic metal elements in raw materials and calcium chloride modified biochar leaching solutions (ppm)

[0108] sample Pb Zn Ni Cr Cu Cd Fly ash 0.0670 ND 0.0003 0.0322 0.0421 0.1663 Sunflower plate ND ND ND ND ND ND <![CDATA[CaCl2-BC]]> 0.0200 ND 0.0002 0.0091 0.0120 0.0333 Concentration limit 5 100 5 5 100 1

[0109] It should be noted that ND means not detected.

[0110] As can be seen from Table 1, by comparing the leaching concentration of each heavy metal with the standard specifications, it can be seen that the leaching concentration of the heavy metal elements contained in it is within the standard limits prescribed by the state, and is much smaller than the prescribed limits. Therefore, when CaCl2-BC is in acid mine water conditions or when other factors such as test block crushing interfere, the leaching of heavy metals in the material meets the prescribed limits and can be safely used in engineering practice.

[0111] The following adsorption test was conducted on the calcium chloride modified biochar prepared by the present invention.

[0112] The sulfate solution is prepared by adding Na2SO4 into deionized water to obtain sulfate solutions with concentrations of 500 mg / L, 1000 mg / L, 1500 mg / L, 2000 mg / L, 2500 mg / L, and 3000 mg / L, respectively, for use.

[0113] Figure 2 The calcium chloride modified biochar material prepared in Example 1 and the calcium chloride modified biochar material (CaCl2-BC+SO42- ) infrared spectrum. Figure 2 It can be seen that many absorption peaks were found in the biochar before adsorption, indicating that there are a large number of various functional groups on the biochar, such as CH, C=O, OH, -COOH, etc. These functional groups will react with SO4 2- Reaction is carried out to achieve the purpose of adsorption.

[0114] 0.5 g of calcium chloride modified biochar was added to 30 mL of 2500 mg / L sulfate solution and adsorbed at 25 °C for 24 h. The infrared test of the calcium chloride modified biochar after adsorption showed that the adsorption of SO4 2- After that, at 3451cm -1 The hydrogen bond absorption peak at the wave number shifted to 3451cm -1 , and 1623cm -1 The carbonyl (C=O) absorption peak at the two positions becomes weaker, indicating that the functional groups at these two positions and SO4 2- A reaction occurred, and during the adsorption process SO4 2- The hydroxyl and carbonyl groups were replaced, resulting in a decrease in their number and a weakening of the absorption peak; at 1136cm -1 There is an absorption peak at SO4 2- caused by vibration; at 510cm -1 The CH absorption peak at the position is greatly weakened, and the CS absorption peak is generated at the same time, indicating that these functional groups and SO4 2- A reaction occurs and new chemical bonds are formed.

[0115] Figure 3 The graph of the adsorption capacity of sulfate ion in different calcium chloride modified biochar materials of the present invention shows that after changing the mass ratio of solid powder and CaCl2 and the calcination temperature, the prepared calcium chloride modified biochar material is adsorbed at 25°C for 24h according to the ratio of calcium chloride modified biochar material to sulfate ion solution of 1g:60mL and the concentration of sulfate ion solution of 2500mg / L. When the calcination temperature remains unchanged, as the mass ratio of solid powder and CaCl2 increases, the sulfate ion removal first increases significantly and then gradually stabilizes. This is because the higher the proportion of CaCl2, the more Ca can be provided for biochar. 2+ Adsorption sites, greatly improving the material's SO4 2- However, the high content of CaCl2 will solidify the biochar surface to some extent, reducing the adsorption capacity. When the mass ratio of solid powder and CaCl2 remains unchanged and the calcination temperature increases, the sulfate removal rate increases first and then decreases. This is because the pyrolysis temperature is too low, which will lead to incomplete combination of CaCl2 and sunflower, thus causing SO4 2-The removal rate is low. The pyrolysis temperature of CaCl2 is above 700℃, so too high a temperature will cause CaCl2 to pyrolyze, resulting in a decrease in the removal rate of sulfate.

[0116] 0.5 g of calcium chloride modified biochar was added to 30 mL of sulfate solution with different concentrations and adsorbed at different temperatures for 24 h. Figure 4 It can be seen that calcium chloride modified biochar has an effect on SO4 2- The adsorption amount of the biochar gradually increases with the increase of the initial concentration and gradually reaches equilibrium. This is because the higher the solution concentration, the more adsorbents can be provided. The liquid film on the surface of the biochar and the SO4 2- The concentration difference increases, the driving force increases, making it more sensitive to SO4 2- The adsorption capacity of biochar increases. Under low concentration conditions, the utilization rate of adsorption sites on the biochar surface is low and the adsorption amount is also low. 2- As the concentration gradually increases, the adsorption sites are gradually occupied and reach saturation, so the adsorption amount also gradually reaches saturation.

[0117] 0.5 g of calcium chloride-modified biochar was added to 30 mL of 2500 mg / L sulfate solution for adsorption at 25 °C. Figure 5 As shown in the figure, when the adsorption time gradually increases, within the initial adsorption time of 14h, the modified biochar has a significant effect on SO4 2- The adsorption capacity of SO4 2- The adsorption amount accounted for 65% of the total adsorption. Then the adsorption amount gradually decreased and finally reached adsorption equilibrium within 50 hours. This is because in the initial stage of adsorption, SO4 2- It quickly combines with the adsorption sites of biochar and the adsorption amount increases rapidly. As the adsorption proceeds, SO4 2- The adsorption amount increased slowly by diffusing into the internal pores of biochar through migration and eventually reached equilibrium. The adsorption process was more consistent with pseudo-second-order kinetics, which indicated that the adsorption process might involve chemical adsorption related to valence through electron exchange or sharing.

[0118] Figure 6 The XRD spectrum of the calcium chloride modified biochar material prepared in Example 1 and after adsorbing sulfate, it can be seen from the XRD spectrum that the pure biochar surface has the characteristic diffraction peak of KCl, and after calcining with CaCl2, the surface mainly has the characteristic diffraction peak of CaCl2, and after treating sulfur-containing mine water, the surface has the characteristic diffraction peak of CaSO4. This shows that after modification, the surface has been successfully loaded with Ca 2+ , and subsequently adsorb SO4 2- role.

[0119] Table 2 shows the specific surface area and pore structure parameters of samples prepared by modifying biochar with different raw materials in Example 1 and Comparative Examples 4 to 7.

[0120] Table 2 Specific surface area and pore structure parameters of samples prepared in Example 1 and Comparative Examples 4-7

[0121]

[0122] Figure 7 The graph shows the adsorption of sulfate by biochar materials modified with different raw materials prepared in Example 1 and Comparative Examples 4 to 7. 0.5 g of biochar modified with calcium chloride of different raw materials was added to 30 mL of a solution with a pH of 3 and a sulfate concentration of 2500 mg / L for adsorption at 25°C. It can be seen from the graph that the biochar prepared with sunflower discs as raw materials has the largest adsorption of sulfate and the strongest pH buffering capacity for the solution. The iron adsorption performance of biochar prepared from different agricultural wastes is ranked as follows: sunflower disc biochar>lotus pod biochar>rice husk biochar>yellow bamboo biochar>corn cob biochar. Combined with the results in Table 2, it can be seen that this is because the specific surface area of ​​the calcium chloride modified biochar prepared with sunflower discs as raw materials is about 7.23 times that of the calcium chloride modified biochar prepared with lotus pods as raw materials, reaching 49.02 m 2 / g, therefore, the sample prepared in Example 1 has more adsorption sites on its surface and a larger contact area with the surrounding environment, has more opportunities to react, and has a stronger adsorption capacity for pollutants than the samples prepared in Comparative Examples 4 to 7 with other raw materials.

[0123] from Figure 8 It can be seen that the adsorption mechanism of the calcium chloride modified biochar material prepared by the present invention mainly includes chemical precipitation, physical adsorption, surface complexation and ion exchange. The chemical precipitation is mainly SO4 2- Ca on the biochar surface 2+ Combined to form CaSO4; physical adsorption is mainly due to the large specific surface area of ​​biochar, which has a good adsorption capacity for pollutants; surface complexation is due to the rich oxygen-containing functional groups on the surface of biochar, such as hydroxyl and carbonyl, which can react with ions in the solution to achieve the purpose of adsorption; ion exchange is due to the negatively charged Cl on the surface of biochar after modification. - With negatively charged SO4 in solution 2- The physical exchange between.

[0124] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0125] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for preparing a calcium chloride modified biochar material, characterized in that: The following steps are involved: The sunflower disc, fly ash and calcium chloride are uniformly mixed and then granulated to obtain a granular biochar raw material; The granular biochar raw material is aged and then calcined at 500°C to 700°C to obtain calcium chloride modified biochar.

2. The method for preparing a calcium chloride modified biochar material according to claim 1, characterized in that: The mass ratio of sunflower disc to fly ash is 2 to 4:

1.

3. The method for preparing a calcium chloride modified biochar material according to claim 1, characterized in that: The added amount of calcium chloride is 25% to 100% of the total mass of the sunflower disc and fly ash.

4. The method for preparing a calcium chloride modified biochar material according to claim 1, characterized in that: The aging temperature is 30℃~50℃, and the aging time is 16h~24h.

5. The method for preparing a calcium chloride modified biochar material according to claim 1, characterized in that: The calcination temperature is 600°C.

6. The method for preparing a calcium chloride modified biochar material according to claim 1, characterized in that: The calcination time is 90min to 150min.

7. The method for preparing a calcium chloride modified biochar material according to claim 1, characterized in that: The particle size of the granular biochar raw material is 2mm to 3mm.

8. A calcium chloride modified biochar material prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the calcium chloride modified biochar material according to claim 8 in the remediation of sulfuric acid mine water pollution, characterized in that: Calcium chloride-modified biochar material is added to the treated sulfuric acid mine water, and adsorption is carried out at 15°C to 35°C to complete the remediation of the treated sulfuric acid mine water.

10. The use of the calcium chloride modified biochar material according to claim 9 in the remediation of sulfuric acid mine water pollution, characterized in that: The ratio of the treated sulfuric acid mine water and calcium chloride modified biochar material is 1g:60ml; The concentration of the sulfuric acid mine water to be treated is 500mg / L to 3000mg / L.

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