Calcium phosphate preparation method based on byproduct ammonium chloride

Abstract

The invention discloses a calcium phosphate preparation method based on by-product ammonium chloride, which effectively reduces the generation of calcium sulfate and calcium fluoride solid waste, and comprises the following steps: S1, adding a fluorine removal agent into 300-360 parts by mass of by-product ammonium chloride solution containing fluorine impurities and phosphate radicals, and carrying out fluorine removal treatment, a fluorine-removed ammonium chloride solution and fluorine-containing residues are obtained; s2, adjusting the pH value of the defluorinated ammonium chloride solution obtained in the step S1 to be neutral or alkalescent; s3, adding a calcium source into the solution of which the pH is adjusted in the step S2, and reacting to generate calcium phosphate precipitate; s4, solid-liquid separation to obtain calcium phosphate solid and further treated ammonium chloride solution. The method is novel in structure, ingenious in conception and simple and convenient to operate, effectively realizes waste liquid resource utilization, improves the fluorine removal effect, accelerates the flocculation speed, improves the recovery rate of the byproduct ammonium chloride, and obtains high-purity calcium phosphate.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical production and relates to a method for preparing calcium phosphate based on by-product ammonium chloride. Background Art

[0002] In the phosphorus chemical industry, fertilizer production and other industries, a large amount of fluoride ions (F - ) and phosphate ions (PO4 3- ) ammonium chloride solution. The resource treatment of this type of waste liquid faces two major challenges: 1. Fluorine impurities are difficult to remove deeply: The traditional process uses the direct addition of calcium salts (such as calcium chloride) to precipitate fluoride, but this will simultaneously generate mixed solid waste of calcium sulfate (CaSO4) and calcium fluoride (CaF2), which has high treatment costs and is prone to environmental risks.

[0003] 2. Waste of phosphate resources: Phosphates in waste liquid are prematurely combined with calcium ions and are wrapped in low-value solid waste, making them unable to be recycled into high-purity calcium phosphate.

[0004] Regarding existing technologies, current improved processes mostly focus on single problems in fluoride removal or calcium phosphate preparation. In the fluoride removal process, polyaluminum chloride (PAC) or activated alumina adsorption is mostly used, but the efficiency is low when treating high-salt ammonium chloride solutions, resulting in more fluoride residues; in the recovery and preparation process of calcium phosphate, additional phosphate ions need to be introduced, resulting in a doubling of costs.

[0005] Therefore, a calcium phosphate preparation method that can simultaneously achieve fluoride removal and efficient calcium phosphate recovery is needed to reduce solid waste generation and increase resource value. Summary of the Invention

[0006] In view of the above problems, the present invention proposes a method for preparing calcium phosphate based on by-product ammonium chloride, which effectively solves the problems in the prior art.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows: A method for preparing calcium phosphate based on by-product ammonium chloride comprises the following steps: Step S1, adding a defluorinating agent to 300-360 parts by mass of a by-product ammonium chloride solution containing fluorine impurities and phosphate groups to perform a defluorination treatment to obtain a defluorinated ammonium chloride solution and a fluorine-containing residue; Step S2, adjusting the pH value of the ammonium chloride solution after defluorination obtained in step S1 to neutral or weak alkaline; Step S3, adding a calcium source to the solution after pH adjustment in step S2 to react and generate calcium phosphate precipitate; Step S4: solid-liquid separation to obtain calcium phosphate solid and ammonium chloride solution after further treatment.

[0008] Preferably, in step S1, the amount of the defluorinating agent added is 0.60-0.72 parts by mass; In step S3, the amount of calcium source added is 6.70-8.05 parts by mass.

[0009] Preferably, in step S1, the defluoridating agent comprises a metal salt and an organic polymer, wherein the metal salt is selected from one or more of iron salts, aluminum salts, and manganese salts; and the organic polymer is selected from one or more of polyaluminum chloride, polyacrylamide, and humic acid.

[0010] Preferably, in step S1, the defluorination treatment includes stirring, precipitation and filtration.

[0011] Preferably, in step S2, the pH value is adjusted to a range of 7-8.

[0012] Preferably, in step S3, the calcium source is calcium chloride.

[0013] Preferably, the calcium chloride is dried before use at a temperature of 250-300° C. for 100-140 minutes.

[0014] Preferably, the stirring speed in step S1 is 200-300 r / min.

[0015] Preferably, the calcium phosphate solid obtained in step S4 is washed with water 2-4 times.

[0016] Preferably, the defluorination agent in step S1 is composed of the following components in parts by mass: Humic acid: 25-35 parts, ferric chloride: 8-12 parts, manganese chloride: 15-25 parts, polyaluminium chloride: 35-45 parts, polyacrylamide: 1 part.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The present invention realizes resource utilization of waste liquid through a reaction mode of first removing fluorine and then generating calcium phosphate salt, improves the fluorine removal effect, accelerates the flocculation speed, improves the recovery rate of by-product ammonium chloride, and obtains high-purity calcium phosphate. DETAILED DESCRIPTION

[0018] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described 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 making creative efforts are within the scope of protection of the present invention.

[0019] The following is a further detailed description with reference to the specific embodiments of the present invention.

[0020] Example 1

[0021] Take 320 parts by mass of ammonium chloride solution produced as a by-product of a chemical plant. - 0.5%, PO4 3- 1.2mol / L), add 0.66 parts by mass of defluoridation agent, which contains 30 parts by mass of humic acid, 10 parts by mass of FeCl3, 20 parts by mass of MnCl2, 40 parts by mass of polyaluminium chloride and 1 part by mass of polyacrylamide, stir at 250r / min for 30min, let it stand for 1h, and filter to obtain the defluoridated solution (F - ≤0.008%) and fluorine-containing residues.

[0022] The pH of the filtrate was adjusted to 7.5 with aqueous ammonia, and 7.4 parts by mass of aluminum chloride (CaCl2) dried at 280°C for 120 min was added. The mixture was reacted for 1 h and then filtered.

[0023] The calcium phosphate filter cake was washed with water three times and dried at 105°C to obtain the finished calcium phosphate product; the filtrate was the ammonium chloride solution after defluoridation.

[0024] Example 2

[0025] On the basis of Example 1, the composition of the defluoridating agent was adjusted. The defluoridating agent used the following proportions: 30 parts of humic acid, 8 parts of FeCl3, 25 parts of MnCl2, 35 parts of PAC, and 1 part of PAM. The other step parameters were the same as those in Example 1.

[0026] Example 3

[0027] Take 320 parts by mass of ammonium chloride solution produced as a by-product of a chemical plant. - 0.5%, PO4 3- 1.2mol / L), add 0.66 parts by mass of defluoridation agent, the composition and amount of defluoridation agent are the same as those in Example 1, stir at 200r / min for 30min, let it stand for 1h, and filter to obtain the defluoridated solution (F - ≤0.008%) and fluorine-containing residues.

[0028] The pH of the filtrate was adjusted to 7.5 with aqueous ammonia, and 7.4 parts by mass of aluminum chloride (CaCl2) dried at 300°C for 100 minutes was added. The mixture was reacted for 1 hour and then filtered.

[0029] The calcium phosphate filter cake was washed twice with water and dried at 105°C to obtain the finished calcium phosphate product; the filtrate was the ammonium chloride solution after defluoridation.

[0030] Example 4

[0031] On the basis of Example 1, the composition of the calcium source was adjusted by replacing calcium chloride with calcium nitrate (Ca(NO3)2) in an amount equivalent to 8.9 parts by mass based on the molar amount of calcium ions. The other step parameters were the same as those in Example 1.

[0032] Example 5.1 On the basis of Example 1, the mass parts of ammonium chloride solution were adjusted to 300, the mass parts of defluoridating agent were adjusted to 0.60 parts, and the mass parts of CaCl2 were adjusted to 6.70 parts. The other step parameters were the same; Example 5.2 On the basis of Example 1, the mass parts of ammonium chloride solution, the mass parts of defluoridating agent and CaCl2 were adjusted to 360, 0.72 and 8.05 parts, respectively, and the other step parameters were the same; Comparative Example 1 Take 320 parts by mass of a by-product ammonium chloride solution from a chemical plant as in Example 1. The ammonium chloride solution contains F - 0.5%, PO4 3- 1.2mol / L), directly add 7.4 parts by mass of CaCl2 to generate gray-white solid waste (CaSO4 and CaF2), and filter to obtain the filtrate (F - 0.38%) and solid waste (mixture of CaSO4 and CaF2), and then to the filtrate (F - 0.38%), add 0.66 parts by mass of defluoridating agent (30 parts by mass of humic acid, 10 parts by mass of FeCl3, 20 parts by mass of MnCl2, 40 parts by mass of PAC, and 1 part by mass of PAM), stir at 250 r / min for 30 min, let it stand for 1 h, and filter to obtain a low-fluorine ammonium chloride solution (without the formation of calcium phosphate).

[0033] Comparative Example 2 On the basis of Example 1, the formula and mass ratio of the defluoridating agent were changed to: 15 parts of humic acid and 50 parts of polyaluminium chloride.

[0034] According to the above examples and comparative examples, the products were tested to obtain the following table: Experimental group Fluorine residual rate Total solid waste (g / 320 parts of solution) <![CDATA[磷酸钙纯度(P2O5% / CaO%)]]> Calcium phosphate production Example 1 0.007% 12.8 41.2% / 54.1% High purity Example 2 0.006% 12.5 41.5% / 54.3% High purity Example 3 0.009% 13.2 40.1% / 53.2% meet the standards Example 4 0.021% 13.5 38.7% / 51.0% Low purity Example 5.1 0.010% 11.9 (300 parts solution) 40.1% / 53.0% High purity Example 5.2 0.008% 14.1 (360 parts solution) 40.3% / 53.2% High purity Comparative Example 1 0.092% 89.5 Not generated No output Comparative Example 2 0.12% 15.0 Not generated No output Combining the above embodiments, comparative examples, and test results, we can obtain the following: Example 1 is the main technical solution of the present invention. Compared with the conventional process in Comparative Example 1, the pre-defluorination process of the present invention avoids the generation of mixed solid waste of calcium sulfate (CaSO4) and calcium fluoride (CaF2). The total amount of solid waste generated by the technical solution of the present invention in Example 1 is only 12.8g, while the total amount of solid waste generated by the conventional process in Comparative Example 1 is 89.5g. The technical solution of the present invention reduces the amount of solid waste generated. In Example 2, compared with Example 1, the defluorination effect of the defluorination agent in the technical solution of the present invention is verified by specifically limiting the specific components of the defluorination agent; In Example 3, compared with Example 1, the stirring speed, calcium chloride drying parameters and the number of water washings were changed, but the test results showed that it was not as good as Example 1; In Example 4, compared with Example 1, the calcium source was changed to calcium nitrate. The results showed that calcium nitrate introduced impurity anions, resulting in a decrease in purity and an increase in the ion concentration of the solution; Comparing Example 5.1 with Example 5.2, the results show that the process of the present invention is relatively stable when the by-product ammonium chloride solution is 300-360 parts by mass; Comparative Example 1 is a traditional process. Compared with Example 1, it does not have pre-fluorination, resulting in a surge in solid waste and low product purity; In Comparative Example 2, compared with Example 1, the ratio of the defluoridating agent was changed. The results showed that when the humic acid content was less than 25 parts, the defluoridation efficiency and flocculation performance dropped sharply.

[0035] The invention has an ingenious design and is simple and convenient to operate. Through the design, the generation of calcium sulfate and calcium fluoride solid wastes is effectively reduced, waste liquid resource utilization is realized, the defluorination effect is improved, the flocculation speed is accelerated, the recovery rate of by-product ammonium chloride is increased, and high-purity calcium phosphate is obtained.

[0036] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing calcium phosphate based on by-product ammonium chloride, characterized in that: The following steps are involved: Step S1, adding a defluorinating agent to 300-360 parts by mass of a by-product ammonium chloride solution containing fluorine impurities and phosphate groups to perform a defluorination treatment to obtain a defluorinated ammonium chloride solution and a fluorine-containing residue; Step S2, adjusting the pH value of the ammonium chloride solution after defluorination obtained in step S1 to neutral or weak alkaline; Step S3, adding a calcium source to the solution after pH adjustment in step S2 to react and generate calcium phosphate precipitate; Step S4: solid-liquid separation to obtain calcium phosphate solid and ammonium chloride solution after further treatment.

2. A method for preparing calcium phosphate based on by-product ammonium chloride according to claim 1, characterized in that: In step S1, the amount of the defluoridating agent added is 0.60-0.72 parts by mass; In step S3, the amount of calcium source added is 6.70-8.05 parts by mass.

3. A method for preparing calcium phosphate based on by-product ammonium chloride according to claim 1, characterized in that: In step S1, the defluoridating agent comprises a metal salt and an organic polymer, wherein the metal salt is selected from one or more of iron salts, aluminum salts, and manganese salts; and the organic polymer is selected from one or more of polyaluminum chloride, polyacrylamide, and humic acid.

4. A method for preparing calcium phosphate based on by-product ammonium chloride according to claim 1, characterized in that: In the step S1, the defluorination treatment includes stirring, settling and filtering.

5. A method for preparing calcium phosphate based on by-product ammonium chloride according to claim 1, characterized in that: In step S2, the pH value is adjusted to a range of 7-8.

6. A method for preparing calcium phosphate based on by-product ammonium chloride according to claim 1, characterized in that: In step S3, the calcium source is calcium chloride.

7. A method for preparing calcium phosphate based on by-product ammonium chloride according to claim 6, characterized in that: The calcium chloride is dried before use at a temperature of 250-300° C. for 100-140 minutes.

8. A method for preparing calcium phosphate based on by-product ammonium chloride according to claim 1, characterized in that: The stirring speed in step S1 is 200-300 r / min.

9. A method for preparing calcium phosphate based on by-product ammonium chloride according to claim 1, characterized in that: The calcium phosphate solid obtained in step S4 is washed with water 2-4 times.

10. A method for preparing calcium phosphate based on by-product ammonium chloride according to claim 1, characterized in that: The defluorination agent in step S1 is composed of the following components in parts by mass: composition: Humic acid: 25-35 parts, ferric chloride: 8-12 parts, manganese chloride: 15-25 parts, polyaluminium chloride: 35-45 parts, polyacrylamide: 1 part.