A method for preparing sugar alcohol chelated calcium and magnesium hydroxide using phosphorus tailings

Abstract

The present invention discloses a method for preparing sugar alcohol chelated calcium and magnesium hydroxide from phosphorus tailings, belonging to the technical field of waste resource utilization. In the present invention, calcium carbonate and magnesium carbonate in phosphorus tailings are decomposed by calcination, and the calcined slag is reacted with ammonium nitrate to obtain phosphorus concentrate; subsequently, ammonia water and sugar alcohol are sequentially added to the leaching solution to obtain magnesium hydroxide and sugar alcohol chelated calcium; the obtained products have high added value, and the whole process of phosphorus tailings resource utilization is simple, which is beneficial to improving the resource utilization rate of phosphorus tailings, thus conducive to solving the problem of phosphorus tailings accumulation, and further conducive to solving the environmental pollution caused by phosphorus tailings, improving the ecological environment, and having great economic, social and environmental benefits.

Description

Technical Field

[0001] The present invention belongs to the technical field of waste resource utilization, and particularly relates to a method for preparing sugar alcohol chelated calcium and magnesium hydroxide by using phosphorus tailings. Background Art

[0002] Phosphorus tailings mainly come from the tailings remaining after beneficiation to extract concentrate, belonging to mining solid waste in industrial solid waste. With the increase of phosphorus ore mining, the quantity of phosphorus tailings is also rising rapidly. After every 1 million t of phosphorus ore is beneficiated, 300,000 - 400,000 t of phosphorus tailings will be produced; phosphorus tailings contain relatively high contents of calcium carbonate, magnesium carbonate, calcium fluorophosphate, etc.; the utilization value is very low, and the phosphorus tailings that have not been effectively treated for a long time pile up like mountains, causing serious pollution to the environment and being a waste of resources. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a method for preparing sugar alcohol chelated calcium and magnesium hydroxide by using phosphorus tailings; this method has the characteristics of low cost, full utilization of waste resources and by-products, and simple process.

[0004] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0005] A method for preparing sugar alcohol chelated calcium and magnesium hydroxide by using phosphorus tailings, comprising the following steps:

[0006] S1: Calcining the phosphorus tailings at 900 - 1000 °C to obtain calcined slag;

[0007] S2: Adding the calcined slag and ammonium nitrate solution into a reaction kettle and stirring for reaction, and separating by filtration to obtain leachate and leached residue;

[0008] S3: Heating the leachate, distilling out ammonia gas, then adding ammonia water to adjust the pH of the leachate, and filtering to obtain magnesium hydroxide and filtrate;

[0009] S4: Heating the filtrate, distilling out ammonia gas, then adding sugar alcohol for reaction to obtain a sugar alcohol chelated calcium solution; adding an organic solvent to the sugar alcohol chelated calcium solution and separating to obtain sugar alcohol chelated calcium.

[0010] In the present invention, the content of calcium oxide in the phosphorus tailings is 33%, and the content of magnesium oxide is 17%. The production process of selective leaching with ammonium salts can be used to prepare magnesium hydroxide (the recovery rate of magnesium is as high as 85%) and calcium sugar alcohol chelate with relatively high economic value (the recovery rate of calcium reaches 83%). As a fertilizer, the calcium element carried by sugar alcohol in calcium sugar alcohol chelate will be recognized as sugar alcohol by the phloem of crops for absorption and transportation. At the same time, it is not easy to synthesize calcium organic acid precipitate with the organic acids in the crop body. In addition, sugar alcohol has a moisturizing function and can stay on the leaves for a longer time, extending the time for crop leaves to absorb calcium element. At the same time, sugar alcohol is also a surfactant, which can make the liquid containing calcium sugar alcohol chelate evenly cover the leaves, increasing the absorption and utilization of calcium by crops; instead of calcium carbonate with relatively low value produced by traditional processes; and it can be used for phosphate rock concentrate in the wet-process phosphoric acid production process. Using this method to treat flotation tailings can improve the problems of low resource and energy utilization rate and poor product quality existing in the carbonization method.

[0011] In the present invention, by first adjusting the pH with ammonia water to precipitate magnesium hydroxide and then chelating with the filtrate, the influence of magnesium during chelation can be reduced. At the same time, adjusting the pH with ammonia water can make the chelation rate and yield of sugar alcohol higher under this condition.

[0012] In the present invention, the reaction in step S2 will generate ammonia gas. The ammonia gas generated in each step is made into ammonia water for recycling, which can reduce waste gas emissions and resource waste.

[0013] In step S1, the specific chemical equations are as follows: CaCO3 = CaO + CO2; MgCO3 = MgO + CO2;

[0014] In step S2, the specific chemical equations are as follows:

[0015] CaO + 2NH4NO3 = Ca(NO3)2 + 2NH3 + H2O;

[0016] MgO + 2NH4NO3 = Mg(NO3)2 + 2NH3 + H2O;

[0017] In step S3, the specific chemical equation is as follows: Mg(NO3)2 + 2NH3·H2O = Mg(OH)2 + 2NH4NO3.

[0018] Preferably, step S1 is carried out at 900 - 1000 °C for calcination for 40 - 90 min.

[0019] Under the above calcination parameters, calcium carbonate and magnesium carbonate in the phosphorus tailings are fully decomposed into calcium oxide and magnesium oxide, and fluorapatite (Ca5F(PO4)3) in the phosphorus tailings does not decompose at this calcination temperature.

[0020] Preferably, in step S2, the molar ratio of ammonium nitrate to calcium oxide in the calcined slag is 8-10:1.

[0021] Preferably, in step S2, the liquid-solid ratio of the ammonium nitrate solution to the calcined slag is 5-10 g:1 g.

[0022] Preferably, in step S2, the concentration of ammonium nitrate in the ammonium nitrate solution is 25%.

[0023] Preferably, in step S2, the temperature of the stirring reaction is 50-80 °C, the rotation speed of the stirring reaction is 100-200 r / min, and the time of the stirring reaction is 45-60 min.

[0024] React the leaching residue with ammonium nitrate. Calcium oxide in the leaching residue reacts to form calcium nitrate, and magnesium oxide reacts to form magnesium nitrate. After filtration, a filtrate containing magnesium nitrate and calcium nitrate and a filter residue containing phosphate rock concentrate are obtained. The filter residue can be further processed to recover phosphorus in the filter residue.

[0025] The parameters of the stirring leaching reaction are the main factors affecting the progress of the reaction. For example, the molar ratio of ammonium nitrate in the ammonium nitrate solution to calcium oxide in the calcined slag, the liquid-solid ratio of the ammonium nitrate solution to the calcined slag, the temperature of the stirring reaction, the concentration of ammonium nitrate in the ammonium nitrate solution, etc.

[0026] If the molar ratio of ammonium nitrate in the ammonium nitrate solution to calcium oxide in the calcined slag is too small, part of the calcium and magnesium will not react with ammonium nitrate for leaching; if the molar ratio of ammonium nitrate to calcium oxide in the calcined slag is too large, the leaching rates of calcium and magnesium will decrease; further preferably, the molar ratio of ammonium nitrate in the ammonium nitrate solution to calcium oxide in the calcined slag is 9:1.

[0027] If the liquid-solid ratio of the ammonium nitrate solution to the calcined slag is too small, the leaching rates of calcium oxide and magnesium oxide will be relatively low; if the liquid-solid ratio of the ammonium nitrate solution to the calcined slag is too large, resources will be wasted due to the slow leaching rate; further preferably, the liquid-solid ratio of the ammonium nitrate solution to the calcined slag is 7 g:1 g.

[0028] If the temperature of the stirring reaction is too low, the reaction rate will be affected and the reaction between calcium oxide and magnesium oxide will be incomplete; if the temperature of the stirring reaction is too high, ammonia will evaporate in advance and the reaction will be incomplete; further preferably, the temperature of the stirring reaction is 60 °C.

[0029] By optimizing the parameters of the reaction between the leaching residue and ammonium nitrate, the leaching residue and ammonium nitrate can react fully, and the recovery rates of magnesium and calcium in the phosphorus tailings can be improved.

[0030] Preferably, in step S3, the heating temperature of the leaching solution is 140-150 °C. At the above temperature, ammonia in the leaching solution can be effectively distilled out. The heating time is determined according to the smell of the leaching solution. When there is no obvious ammonia smell in the leaching solution, stop heating.

[0031] Preferably, in step S3, the pH of the leaching solution is 9-10.

[0032] The pH value of the leaching solution affects the precipitation effect of magnesium hydroxide. If the pH of the leaching solution is too large or too small, magnesium hydroxide cannot be completely precipitated; when the pH of the leaching solution is 10, magnesium hydroxide can be completely precipitated, further improving the recovery rate of magnesium.

[0033] Preferably, in step S4, the reaction temperature is 65-80 °C and the reaction time is 30-60 min.

[0034] Preferably, in step S4, the sugar alcohol is xylitol.

[0035] The temperature of the chelation reaction between calcium nitrate and sugar alcohol, as well as the type of sugar alcohol, are the main factors affecting the chelation rate of sugar alcohol chelated calcium. If the temperature of the chelation reaction between calcium nitrate and sugar alcohol is too low or too high, the chelation rate of sugar alcohol chelated calcium will be affected. When the reaction temperature is 65 °C, the chelation rate of sugar alcohol chelated calcium is the highest; compared with sorbitol, mannitol, and glycerol, under alkaline conditions, the chelation effect of xylitol and calcium nitrate is better, which can further improve the chelation rate of sugar alcohol chelated calcium.

[0036] Preferably, in step S4, the organic solvent is acetone; the separation method is shaking separation.

[0037] In the present invention, acetone solvent is used to extract sugar alcohol chelated calcium, which has a better extraction effect than acetonitrile and is safer than n-butanol; the method of shaking separation to extract sugar alcohol chelated calcium has a significantly better effect than centrifugation, ultrasonic wave and other methods.

[0038] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0039] (1) In the present invention, calcium carbonate and magnesium carbonate in the phosphorus tailings are decomposed by calcination, and the calcined slag is reacted with ammonium nitrate to obtain phosphorus concentrate; subsequently, ammonia water and sugar alcohol are sequentially added to the leaching solution to obtain magnesium hydroxide and sugar alcohol chelated calcium; the obtained products have high added value, and the whole process of resource utilization of phosphorus tailings is simple, which is conducive to greatly improving the resource utilization rate of phosphorus tailings, thus conducive to solving the problem of phosphorus tailings accumulation, and further conducive to solving the environmental pollution caused by phosphorus tailings, improving the ecological environment, and having great economic, social and environmental benefits.

[0040] (2) The ammonia gas generated in the present invention is recycled in the system, which not only saves the raw material cost, but also makes the ammonia gas generated in this method be fully utilized, avoiding the waste of resources and environmental pollution.

[0041] (3) In the phosphorus tailings of the present invention, the recovery rate of magnesium is as high as 98.8%, and the recovery rate of calcium reaches 83%, fully realizing the resource recovery and utilization. Brief Description of the Drawings

[0042] Figure 1 This is a schematic flow diagram of the present invention. Detailed Description of the Invention

[0043] In order to better illustrate the purpose, technical solution and advantages of the present invention, the present invention will be further described below in conjunction with specific examples and comparative examples. The purpose is to understand the content of the present invention in detail, rather than a limitation to the present invention. All other examples obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention. The experimental reagents and instruments involved in the implementation of the present invention are all common ordinary reagents and instruments unless otherwise specified.

[0044] Example 1

[0045] This example provides a method for preparing sugar alcohol chelated calcium and magnesium hydroxide from phosphorus tailings, comprising the following steps:

[0046] S1: Calcinate the phosphorus tailings at 1000 °C for 1 h, and cool to 25 °C to obtain calcined slag;

[0047] S2: Add the calcined slag and ammonium nitrate solution into a reaction kettle, stir and react at a rotation speed of 150 r / min and a temperature of 60 °C for 50 min to generate ammonia gas, and obtain leachate and leached residue through filtration and separation; wherein, the molar ratio of ammonium nitrate in the ammonium nitrate solution to calcium oxide in the calcined slag is 9:1, and the liquid-solid ratio of the ammonium nitrate solution to the calcined slag is 7 g:1 g;

[0048] S3: Heat the leachate to 150 °C, distill out ammonia gas until there is no obvious ammonia smell in the leachate, then add ammonia water to adjust the pH of the leachate to 10, and filter to obtain magnesium hydroxide and filtrate;

[0049] S4: Heat the filtrate to 150 °C, distill out ammonia gas until there is no obvious ammonia smell in the leachate, then cool to 65 °C, and add xylitol solution to react for 45 min to obtain sugar alcohol chelated calcium solution;

[0050] S5: After adding acetone to the sugar alcohol chelated calcium solution, shake for 30 min to obtain chelating substrate and supernatant, and separate; the obtained chelating substrate is repeated in step S5 continuously for 3 times to obtain white colloidal sugar alcohol chelated calcium.

[0051] In this example, the recovery rate of magnesium is 98.8%; the chelation rate of sugar alcohol chelated calcium is 87.26%.

[0052] Example 2

[0053] This example provides a method for preparing sugar alcohol chelated calcium and magnesium hydroxide from phosphorus tailings, comprising the following steps:

[0054] S1: Calcinate the phosphate tailings at 950 °C for 40 min, and cool to 25 °C to obtain the calcined slag;

[0055] S2: Add the calcined slag and ammonium nitrate solution to the reaction kettle, stir and react at a rotation speed of 150 r / min and a temperature of 60 °C for 50 min to generate ammonia gas, and obtain the leaching solution and leaching residue through filtration and separation; wherein, the molar ratio of ammonium nitrate in the ammonium nitrate solution to calcium oxide in the calcined slag is 8:1, and the liquid-solid ratio of the ammonium nitrate solution to the calcined slag is 5 g:1 g;

[0056] S3: Heat the leaching solution to 150 °C, distill out ammonia gas until there is no obvious ammonia smell in the leaching solution, then add ammonia water to adjust the pH of the leaching solution to 10, and filter to obtain magnesium hydroxide and the filtrate;

[0057] S4: Heat the filtrate to 150 °C, distill out ammonia gas until there is no obvious ammonia smell in the leaching solution, then cool to 65 °C, add xylitol solution and react for 45 min to obtain the sugar alcohol chelated calcium solution;

[0058] S5: Add acetone to the sugar alcohol chelated calcium solution, shake for 30 min to obtain the chelating substrate and the supernatant, and separate; repeat step S5 for the obtained chelating substrate continuously for 3 times to obtain white colloidal sugar alcohol chelated calcium.

[0059] In this example, the recovery rate of magnesium is 80.56%; the chelation rate of sugar alcohol chelated calcium is 82.16%.

[0060] Example 3

[0061] This example provides a method for preparing sugar alcohol chelated calcium and magnesium hydroxide from phosphate tailings, including the following steps:

[0062] S1: Calcinate the phosphate tailings at 1000 °C for 1 h, and cool to 25 °C to obtain the calcined slag;

[0063] S2: Add the calcined slag and ammonium nitrate solution to the reaction kettle, stir and react at a rotation speed of 150 r / min and a temperature of 60 °C for 50 min to generate ammonia gas, and obtain the leaching solution and leaching residue through filtration and separation; wherein, the molar ratio of ammonium nitrate in the ammonium nitrate solution to calcium oxide in the calcined slag is 10:1, and the liquid-solid ratio of the ammonium nitrate solution to the calcined slag is 8 g:1 g;

[0064] S3: Heat the leaching solution to 150 °C, distill out ammonia gas until there is no obvious ammonia smell in the leaching solution, then add ammonia water to adjust the pH of the leaching solution to 10, and filter to obtain magnesium hydroxide and the filtrate;

[0065] S4: Heat the filtrate to 150 °C, distill out ammonia gas until there is no obvious ammonia smell in the leaching solution, then cool to 65 °C, add xylitol solution and react for 45 min to obtain the sugar alcohol chelated calcium solution;

[0066] S5: After adding acetone to the calcium sugar alcohol chelate solution, shake for 30 min to obtain a chelating substrate and supernatant, and separate them; repeat step S5 for the obtained chelating substrate three times continuously to obtain white colloidal calcium sugar alcohol chelate.

[0067] In this example, the recovery rate of magnesium is 90.87%; the chelation rate of calcium sugar alcohol chelate is 82.16%.

[0068] Example 4

[0069] This example provides a method for preparing calcium sugar alcohol chelate and magnesium hydroxide using phosphorus tailings, including the following steps:

[0070] This example provides a method for preparing calcium sugar alcohol chelate and magnesium hydroxide using phosphorus tailings. The difference between this example and Example 1 is only that: in step S3, the pH of the leaching solution is 9.

[0071] In this example, the recovery rate of magnesium is 70.95%; the chelation rate of calcium sugar alcohol chelate is 70.58%.

[0072] Example 5

[0073] This example provides a method for preparing calcium sugar alcohol chelate and magnesium hydroxide using phosphorus tailings. The difference between this example and Example 1 is only that: in step S4, the xylitol solution is replaced with a sorbitol solution.

[0074] In this example, the recovery rate of magnesium is 98.8%; the chelation rate of calcium sugar alcohol chelate is 75.45%.

[0075] Example 6

[0076] This example provides a method for preparing calcium sugar alcohol chelate and magnesium hydroxide using phosphorus tailings, including the following steps:

[0077] S1: Calcinate the phosphorus tailings at 900 °C for 1.5 h, and cool to 25 °C to obtain a calcined residue;

[0078] S2: Add the calcined residue and ammonium nitrate solution to a reaction kettle, stir and react at a rotation speed of 200 r / min and a temperature of 80 °C for 45 min to generate ammonia gas, and obtain a leaching solution and a leaching residue through filtration and separation; wherein, the molar ratio of ammonium nitrate in the ammonium nitrate solution to calcium oxide in the calcined residue is 9:1, and the liquid-solid ratio of the ammonium nitrate solution to the calcined residue is 10 g:1 g;

[0079] S3: Heat the leaching solution to 150 °C, distill out ammonia gas until there is no obvious ammonia smell in the leaching solution, then add ammonia water to adjust the pH of the leaching solution to 9.5, and filter to obtain magnesium hydroxide and a filtrate;

[0080] S4: Heat the filtrate to 150 °C, distill off ammonia until there is no obvious ammonia smell in the leaching solution, then cool it to 70 °C, add xylitol solution and react for 60 min to obtain a sugar alcohol chelated calcium solution;

[0081] S5: Add acetone to the sugar alcohol chelated calcium solution, shake for 30 min to obtain a chelated substrate and supernatant, and separate them; Repeat step S5 for the obtained chelated substrate three times continuously to obtain white colloidal sugar alcohol chelated calcium.

[0082] In this example, the recovery rate of magnesium is 72.58%; the chelation rate of sugar alcohol chelated calcium is 74.31%.

[0083] Example 7

[0084] This example provides a method for preparing sugar alcohol chelated calcium and magnesium hydroxide from phosphorus tailings, including the following steps:

[0085] S1: Calcinate the phosphorus tailings at 1000 °C for 1 h, and cool to 25 °C to obtain a calcined slag;

[0086] S2: Add the calcined slag and ammonium nitrate solution to the reaction kettle, stir and react at a rotation speed of 100 r / min and a temperature of 50 °C for 50 min to generate ammonia, and obtain a leaching solution and a leaching residue through filtration and separation; Among them, the molar ratio of ammonium nitrate in the ammonium nitrate solution to calcium oxide in the calcined slag is 9:1, and the liquid-solid ratio of the ammonium nitrate solution to the calcined slag is 7 g:1 g;

[0087] S3: Heat the leaching solution to 150 °C, distill off ammonia until there is no obvious ammonia smell in the leaching solution, then add ammonia water to adjust the pH of the leaching solution to 10, and filter to obtain magnesium hydroxide and a filtrate;

[0088] S4: Heat the filtrate to 150 °C, distill off ammonia until there is no obvious ammonia smell in the leaching solution, then cool it to 80 °C, add xylitol solution and react for 30 min to obtain a sugar alcohol chelated calcium solution;

[0089] S5: Add acetone to the sugar alcohol chelated calcium solution, shake for 30 min to obtain a chelated substrate and supernatant, and separate them; Repeat step S5 for the obtained chelated substrate three times continuously to obtain white colloidal sugar alcohol chelated calcium.

[0090] In this example, the recovery rate of magnesium is 85.97%; the chelation rate of sugar alcohol chelated calcium is 72.94%.

[0091] Comparative Example 1

[0092] This comparative example provides a method for preparing sugar alcohol chelated calcium and magnesium hydroxide from phosphorus tailings. The difference between this comparative example and Example 1 is only that: in step S3, the pH of the leaching solution is 11.

[0093] In this comparative example, the recovery rate of magnesium was 23.76%; the chelation rate of calcium glycitol chelate was 87.26%.

[0094] Comparative Example 2

[0095] This example provides a method for preparing calcium glycitol chelate and magnesium hydroxide from phosphorus tailings, comprising the following steps:

[0096] S1: Calcinate the phosphorus tailings at 1000 °C for 1 h, and cool to 25 °C to obtain the calcined slag;

[0097] S2: Add the calcined slag and ammonium nitrate solution to a reaction kettle, stir and react at a rotation speed of 150 r / min and a temperature of 60 °C for 20 min to generate ammonia gas, and obtain the leaching solution and leaching residue by filtration and separation; wherein, the molar ratio of ammonium nitrate in the ammonium nitrate solution to calcium oxide in the calcined slag is 9:1, and the liquid-solid ratio of the ammonium nitrate solution to the calcined slag is 7 g:1 g;

[0098] S3: Heat the leaching solution to 150 °C, distill out ammonia gas until there is no obvious ammonia smell in the leaching solution, then cool to 65 °C, and add xylitol solution to react for 45 min to obtain a calcium glycitol chelate solution;

[0099] S4: After adding acetone to the calcium glycitol chelate solution, shake for 30 min to obtain the chelating substrate and the supernatant, and separate; repeat step S5 for the obtained chelating substrate 3 times continuously to obtain white colloidal calcium glycitol chelate;

[0100] S5: Add ammonia water to the obtained supernatant to adjust the pH of the supernatant to 10, filter to obtain magnesium hydroxide and the filtrate.

[0101] In this comparative example, the recovery rate of magnesium was 43.58%; the chelation rate of calcium glycitol chelate was 40.26%.

[0102] Finally, it should be noted that the above examples are used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing sugar alcohol chelated calcium and magnesium hydroxide using phosphorus tailings, characterized in that, It includes the following steps: S1: Calcine the phosphorus tailings at 900 - 1000 °C to obtain calcined slag; S2: Add the calcined slag and ammonium nitrate solution into a reaction kettle, stir and react, then filter and separate to obtain leachate and leached residue; the molar ratio of ammonium nitrate in the ammonium nitrate solution to calcium oxide in the calcined slag is 8 - 10:1; the liquid-solid ratio of the ammonium nitrate solution to the calcined slag is 5 - 10 g:1 g; S3: Heat the leachate, distill out ammonia gas, then add ammonia water to adjust the pH of the leachate, filter to obtain magnesium hydroxide and filtrate; the pH of the leachate is 9 - 10; S4: Heat the filtrate, distill out ammonia gas, then add sugar alcohol to react to obtain a sugar alcohol chelated calcium solution; add an organic solvent to the sugar alcohol chelated calcium solution and then separate to obtain sugar alcohol chelated calcium.

2. The method according to claim 1, characterized in that In step S1, the calcination is carried out at 900 - 1000 °C for 40 - 90 min.

3. The method according to claim 1, wherein In step S2, the concentration of ammonium nitrate in the ammonium nitrate solution is 25%.

4. The method according to claim 1, wherein In step S2, the temperature of the stirring reaction is 50 - 80 °C, the rotation speed of the stirring reaction is 100 - 200 r / min, and the time of the stirring reaction is 45 - 60 min.

5. The method according to claim 1, characterized in that, In step S4, the temperature of the reaction is 65 - 80 °C, and the time of the reaction is 30 - 60 min.

6. The method according to claim 1, wherein In step S4, the sugar alcohol is one of xylitol and sorbitol.

7. The method according to claim 1, characterized in that In step S4, the organic solvent is acetone; the separation method is shaking separation.

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