CN111232941A - Method for preparing hydroxyapatite based on phosphogypsum cleaning wastewater - Google Patents
Method for preparing hydroxyapatite based on phosphogypsum cleaning wastewater Download PDFInfo
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Abstract
The invention relates to a method for preparing hydroxyapatite based on phosphogypsum cleaning wastewater, which comprises the following steps: (1) carrying out pH adjustment and stirring on the cleaning wastewater, and then carrying out solid-liquid separation to obtain a filtrate; (2) heating and stirring the filtrate obtained in the step (1), adjusting the pH value of the filtrate by a first method, cooling the filtrate, adjusting the pH value of the filtrate by a second method, stirring the filtrate for reaction, and performing solid-liquid separation to obtain a solid; (3) and (3) sequentially washing and calcining the solid obtained in the step (2) to obtain the hydroxyapatite. The method is based on the water washing pretreatment of the phosphogypsum, does not add toxic reagents in the whole process, has mild reaction conditions, can solve the problem of secondary pollution caused by the water washing pretreatment of the phosphogypsum, and does not cause harm to the environment. In addition, the filtrate obtained by filtering the prepared hydroxyapatite can be used for cleaning phosphogypsum, so that the water can be recycled, and the consumption of water resources is reduced.
Description
Technical Field
The invention relates to the field of wastewater treatment, and particularly relates to a method for preparing hydroxyapatite based on phosphogypsum cleaning wastewater.
Background
The phosphogypsum is industrial waste residue discharged in the process of producing phosphoric acid by a chemical wet method, contains various impurities such as soluble phosphorus, fluorine and the like, and is difficult to be directly utilized, so that most of the phosphogypsum is idle and wasted, and not only needs to be stored in an occupied land, but also causes environmental pollution.
The pretreatment of the phosphogypsum is the key of comprehensive utilization of the phosphogypsum, wherein a water washing method is a common treatment method. The water washing method is to repeatedly wash the phosphogypsum by water, can remove most of water-soluble phosphorus, fluorine and part of organic matters, but has very large water consumption and causes secondary pollution if the wastewater is not treated. How to treat the waste liquid generated in the production process becomes a new problem of phosphogypsum utilization. The existing waste water treatment usually adopts a lime neutralization treatment method, in the process of lime neutralization of waste liquid, fluorine ions, sulfate radicals, heavy metal ions and the like in the waste liquid can be synchronously removed, but the sludge amount is large, and the obtained solid waste can only be recycled in a factory and cannot be directly utilized as a new material. For example, CN104495774A provides a method for preparing high-grade nano hydroxyapatite and calcium sulfate whisker from industrial byproduct phosphogypsum, which comprises using cheap industrial byproduct phosphogypsum as raw material, firstly pretreating phosphogypsum, including washing, dissociating, filtering to remove a small amount of insoluble impurities, dissociating the phosphogypsum with complex impurities into pure solutions of calcium ions and sulfate ions, and then mixing and crystallizing respectively to prepare high-grade nano hydroxyapatite and calcium sulfate whisker. The technology and the process adopted by the invention are stable and reliable, the obtained nano-hydroxyapatite can be used for heavy metal ion adsorption and soil improvement and restoration, and the calcium sulfate whisker can be used as a filler to be applied to composite materials, so that the current situations of large accumulation of phosphogypsum, environmental pollution and difficult utilization are improved, and the method has better application prospect and economic and social benefits.
Disclosure of Invention
In view of the problems in the prior art, the invention aims to provide a method for preparing hydroxyapatite based on phosphogypsum cleaning wastewater, harmful soluble impurities in phosphogypsum washing filtrate can be effectively removed through the method, and the hydroxyapatite material can be prepared.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a method for preparing hydroxyapatite based on phosphogypsum cleaning wastewater, which comprises the following steps:
(1) carrying out pH adjustment and stirring on the cleaning wastewater, and then carrying out solid-liquid separation to obtain a filtrate;
(2) heating and stirring the filtrate obtained in the step (1), adjusting the pH value of the filtrate by a first method, cooling the filtrate, adjusting the pH value of the filtrate by a second method, stirring the filtrate for reaction, and performing solid-liquid separation to obtain a solid;
(3) and (3) sequentially washing and calcining the solid obtained in the step (2) to obtain the hydroxyapatite.
The method is based on the water washing pretreatment of the phosphogypsum, does not add toxic reagents in the whole process, has mild reaction conditions, can solve the problem of secondary pollution caused by the water washing pretreatment of the phosphogypsum, and does not cause harm to the environment. In addition, the pH is firstly adjusted by calcium carbonate, so that the pH is not raised too high, the content of soluble phosphorus is reduced, but the pH range of the solution after the adjustment is not suitable for the existence of soluble fluorine and partial metal ions (such as Fe, V and the like), and the aim of removing impurities is fulfilled. In addition, the filtrate obtained by filtering the prepared hydroxyapatite can be used for cleaning phosphogypsum, so that the water can be recycled, and the consumption of water resources is reduced.
In a preferred embodiment of the present invention, the pH at the end of the pH adjustment in step (1) is 5.5 to 6.0, for example, 5.5, 5.6, 5.7, 5.8, 5.9 or 6, but is not limited to the above-mentioned values, and other values not mentioned in this range are also applicable.
Preferably, the agent in the pH adjustment of step (1) comprises calcium carbonate.
Preferably, the calcium carbonate has a purity of > 95%, for example 95%, 96%, 97%, 98%, 99%, or 100%, etc., but is not limited to the recited values, and other values not recited within this range are equally applicable.
In the invention, calcium carbonate reacts under acidic condition, so that hydrogen ions can be consumed to increase the pH of the solution, and introduced calcium ions can further inhibit impurities such as sulfate radicals, fluorine ions and the like in the solution. In addition, calcium carbonate is an insoluble substance, which cannot cause great increase of pH due to excessive amount, so that a great amount of loss of phosphorus source in the filtrate cannot be caused.
In a preferred embodiment of the present invention, the stirring time in step (1) is 20 to 40min, for example, 20min, 25min, 30min, 35min, or 40min, but is not limited to the above-mentioned values, and other values not shown in the above-mentioned range are also applicable.
Preferably, the stirring speed in step (1) is 200-300rpm, such as 200rpm, 220rpm, 240rpm, 260rpm, 280rpm or 300rpm, but not limited to the enumerated values, and other unrecited values in the range are also applicable.
In a preferred embodiment of the present invention, the temperature of heating in the heating and stirring in the step (2) is 50 to 70 ℃, and may be, for example, 50 ℃, 55 ℃, 60 ℃, 65 ℃ or 70 ℃, but is not limited to the above-mentioned values, and other values not shown in the above-mentioned range are also applicable.
Preferably, the heating and stirring time in step (2) is 0.5-2h, such as 0.5h, 1h, 1.5h or 2h, but not limited to the recited values, and other values not recited in the range are also applicable.
Preferably, the rotation speed of the heating and stirring in the step (2) is 100-200rpm, such as 100rpm, 120rpm, 140rpm, 160rpm, 180rpm or 200rpm, but not limited to the enumerated values, and other unrecited values in the range are also applicable.
In a preferred embodiment of the present invention, the end point pH of the first pH adjustment in step (2) is <3, and may be, for example, 3, 2.8, 2.6, 2.4, 2.2, 2, 1.8 or 1.6, but is not limited to the values listed above, and other values not listed within this range are also applicable.
Preferably, the first pH adjusting agent of step (2) comprises phosphoric acid.
As a preferred embodiment of the present invention, the final temperature of the cooling in the step (2) is 20 to 30 ℃ and may be, for example, 20 ℃, 22 ℃, 24 ℃, 26 ℃, 28 ℃ or 30 ℃ or the like, but is not limited to the above-mentioned values, and other values not shown in the above range are also applicable.
In a preferred embodiment of the present invention, the final pH of the second pH adjustment in step (2) is 10 to 12, for example, 10, 10.5, 11, 11.5 or 12, but is not limited to the above-mentioned values and other values not listed in the range are also applicable.
Preferably, the second pH adjusting agent of step (2) comprises calcium oxide and/or calcium hydroxide.
Preferably, the reaction time in step (2) is 20-40min, such as 20min, 25min, 30min, 35min or 40min, but not limited to the recited values, and other values not recited in the range are also applicable.
Preferably, the rotation speed of stirring in the reaction in step (2) is 200-300rpm, such as 200rpm, 220rpm, 240rpm, 260rpm, 280rpm or 300rpm, but not limited to the enumerated values, and other unrecited values in the range are also applicable.
As a preferable technical scheme of the invention, the washing cleaning agent in the step (3) comprises water and/or ethanol.
Preferably, the washing time in step (3) is 3-5min, such as 3min, 3.5min, 4min, 4.5min or 5min, but not limited to the recited values, and other values not recited in the range are also applicable.
Preferably, the temperature of the calcination in step (3) is 700-900 deg.C, such as 700 deg.C, 750 deg.C, 800 deg.C, 850 deg.C or 900 deg.C, but not limited to the recited values, and other values not recited in the range are also applicable.
Preferably, the calcination time in step (3) is 1-4h, such as 1h, 1.5h, 2h, 2.5h, 3h, 3.5h or 4h, but not limited to the recited values, and other values not recited in the range are also applicable.
As a preferred technical scheme of the invention, the cleaning wastewater in the step (1) is obtained by the following process: mixing the phosphogypsum and water uniformly, stirring, standing for layering to remove upper-layer oily suspended matters, and carrying out solid-liquid separation to obtain phosphogypsum solid and cleaning wastewater.
Preferably, the water is present in an amount of 3 to 20 times the weight of the phosphogypsum, for example 3, 5, 10, 15 or 20 times the weight of the phosphogypsum, but is not limited to the recited values, and other values not recited in this range are equally applicable.
Preferably, the liquid obtained by the solid-liquid separation in the step (2) can be used as water when the phosphogypsum is stirred.
As a preferred technical scheme of the invention, the method comprises the following steps:
(1) carrying out pH adjustment and stirring on the cleaning wastewater, and then carrying out solid-liquid separation to obtain a filtrate; wherein the pH value of the pH adjusting end point is 5.5-6.0; the agent in the pH adjustment comprises calcium carbonate; the purity of the calcium carbonate is more than 95 percent; the stirring time is 20-40 min; the rotating speed of the stirring is 200-300 rpm;
(2) heating and stirring the filtrate obtained in the step (1), adjusting the pH value of the filtrate by a first method, cooling the filtrate, adjusting the pH value of the filtrate by a second method, stirring the filtrate for reaction, and performing solid-liquid separation to obtain a solid; wherein the heating temperature in the heating and stirring process is 50-70 ℃; the heating and stirring time is 0.5-2 h; the end point pH of the first pH adjustment is < 3; the first pH adjusting agent comprises phosphoric acid; the final cooling temperature is 20-30 ℃; the end point pH value of the second pH adjustment is 10-12; the second pH adjusting agent comprises calcium oxide and/or calcium hydroxide; the reaction time is 20-40 min; the rotating speed of the heating and stirring is 100-200 rpm; the stirring speed in the reaction is 200-300 rpm;
(3) washing and calcining the solid obtained in the step (2) in sequence to obtain the hydroxyapatite; the washing cleaning agent comprises water and/or ethanol; the washing time is 3-5 min; the calcining temperature is 700-900 ℃; the calcining time is 1-4 h;
wherein, the cleaning wastewater in the step (1) is obtained through the following process: uniformly mixing and stirring phosphogypsum and water, standing for layering to remove upper-layer oily suspended matters, and carrying out solid-liquid separation to obtain phosphogypsum solid and cleaning wastewater; the mass of the water is 3-20 times of that of the phosphogypsum; and (3) performing solid-liquid separation to obtain liquid which can be used as water for stirring the phosphogypsum.
Compared with the prior art, the invention at least has the following beneficial effects:
(1) in the whole process of the invention, no toxic reagent is added, the reaction condition is mild, the problem of secondary pollution caused by phosphogypsum washing pretreatment can be solved, and no harm is caused to the environment.
(2) The filtrate obtained by filtering the prepared hydroxyapatite can be used for cleaning phosphogypsum, so that the water can be recycled, the consumption of water resources is reduced, the content of soluble phosphorus in the filtrate is not higher than 2.6ppm, the content of V in the obtained hydroxyapatite is not higher than 0.07%, the content of Fe in the hydroxyapatite is not higher than 0.117%, and the content of F in the hydroxyapatite is not higher than 1.062%.
Drawings
FIG. 1 is a process diagram of an embodiment of the present invention in example 1.
The present invention is described in further detail below. The following examples are merely illustrative of the present invention and do not represent or limit the scope of the claims, which are defined by the claims.
Detailed Description
The technical scheme of the invention is further explained by the specific implementation mode in combination with the attached drawings.
To better illustrate the invention and to facilitate the understanding of the technical solutions thereof, typical but non-limiting examples of the invention are as follows:
example 1
The embodiment provides a method for preparing hydroxyapatite based on phosphogypsum cleaning wastewater, which comprises the following steps of:
(1) carrying out pH adjustment and stirring on the cleaning wastewater, and then carrying out solid-liquid separation to obtain a filtrate; wherein the end point pH of the pH adjustment is 5.56; the agent in the pH adjustment comprises calcium carbonate; the purity of the calcium carbonate is more than 95 percent; the stirring time is 30 min; the rotating speed of the stirring is 300 rpm;
(2) heating and stirring the filtrate obtained in the step (1), adjusting the pH value of the filtrate by a first method, cooling the filtrate, adjusting the pH value of the filtrate by a second method, stirring the filtrate for reaction, and performing solid-liquid separation to obtain a solid; wherein the heating temperature in the heating and stirring process is 50 ℃; the heating and stirring time is 2 hours; the end point pH of the first pH adjustment is 2.56; the first pH adjusting agent comprises phosphoric acid; the final temperature of the cooling is 25 ℃; the end point pH of the second pH adjustment is 11.43; the second pH adjusting agent comprises calcium oxide; the reaction time is 30 min; the rotating speed of the heating and stirring is 200 rpm; the stirring speed in the reaction is 300 rpm;
(3) washing and calcining the solid obtained in the step (2) in sequence to obtain the hydroxyapatite; the washing cleaning agent comprises water and/or ethanol; the washing time is 3-5 min; the temperature of the calcination is 700 ℃; the calcining time is 4 h;
wherein, the cleaning wastewater in the step (1) is obtained through the following process: uniformly mixing and stirring phosphogypsum and water, standing for layering to remove upper-layer oily suspended matters, and carrying out solid-liquid separation to obtain phosphogypsum solid and cleaning wastewater; the mass of the water is 10 times of that of the phosphogypsum; and (3) performing solid-liquid separation to obtain liquid which can be used as water for stirring the phosphogypsum.
And (3) detecting the filtrate obtained by solid-liquid separation in the step (2), wherein the content of soluble phosphorus in the filtrate is 0.6ppm, and testing the hydroxyapatite in the step (3), wherein the content of F, Fe and the content of V are respectively 1.062%, 0.115% and 0.007%.
Example 2
The embodiment provides a method for preparing hydroxyapatite based on phosphogypsum cleaning wastewater, which comprises the following steps:
(1) carrying out pH adjustment and stirring on the cleaning wastewater, and then carrying out solid-liquid separation to obtain a filtrate; wherein the end point pH of the pH adjustment is 5.68; the agent in the pH adjustment comprises calcium carbonate; the purity of the calcium carbonate is more than 95 percent; the stirring time is 30 min; the rotating speed of the stirring is 200 rpm;
(2) heating and stirring the filtrate obtained in the step (1), adjusting the pH value of the filtrate by a first method, cooling the filtrate, adjusting the pH value of the filtrate by a second method, stirring the filtrate for reaction, and performing solid-liquid separation to obtain a solid; wherein the heating temperature in the heating and stirring process is 70 ℃; the heating and stirring time is 0.5 h; the end point pH of the first pH adjustment is 2.34; the first pH adjusting agent comprises phosphoric acid; the final temperature of the cooling is 20 ℃; the end point pH of the second pH adjustment is 11.32; the second pH adjusting agent comprises calcium oxide; the reaction time is 30 min; the rotating speed of the heating and stirring is 100 rpm; the stirring speed in the reaction is 300 rpm;
(3) washing and calcining the solid obtained in the step (2) in sequence to obtain the hydroxyapatite; the washing cleaning agent comprises water and/or ethanol; the washing time is 3-5 min; the calcining temperature is 800 ℃; the calcining time is 3 hours;
wherein, the cleaning wastewater in the step (1) is obtained through the following process: uniformly mixing and stirring phosphogypsum and water, standing for layering to remove upper-layer oily suspended matters, and carrying out solid-liquid separation to obtain phosphogypsum solid and cleaning wastewater; the mass of the water is 20 times of that of the phosphogypsum; and (3) performing solid-liquid separation to obtain liquid which can be used as water for stirring the phosphogypsum.
And (3) detecting the filtrate obtained by solid-liquid separation in the step (2), wherein the content of soluble phosphorus in the filtrate is 1.2ppm, and testing the hydroxyapatite in the step (3), wherein the contents of F, Fe and V are respectively 0.719%, 0.105% and 0.004%.
Example 3
The embodiment provides a method for preparing hydroxyapatite based on phosphogypsum cleaning wastewater, which comprises the following steps:
(1) carrying out pH adjustment and stirring on the cleaning wastewater, and then carrying out solid-liquid separation to obtain a filtrate; wherein the end point pH of the pH adjustment is 5.50; the agent in the pH adjustment comprises calcium carbonate; the purity of the calcium carbonate is more than 95 percent; the stirring time is 30 min; the rotating speed of the stirring is 250 rpm;
(2) heating and stirring the filtrate obtained in the step (1), adjusting the pH value of the filtrate by a first method, cooling the filtrate, adjusting the pH value of the filtrate by a second method, stirring the filtrate for reaction, and performing solid-liquid separation to obtain a solid; wherein the heating temperature in the heating and stirring process is 50 ℃; the heating and stirring time is 2 hours; the end point pH of the first pH adjustment is 2.88; the first pH adjusting agent comprises phosphoric acid; the final temperature of the cooling is 30 ℃; the end point pH of the second pH adjustment is 10.58; the second pH adjusting agent comprises calcium hydroxide; the reaction time is 30 min; the rotating speed of the heating and stirring is 150 rpm; the stirring speed in the reaction is 200 rpm;
(3) washing and calcining the solid obtained in the step (2) in sequence to obtain the hydroxyapatite; the washing cleaning agent comprises water and/or ethanol; the washing time is 3-5 min; the calcining temperature is 900 ℃; the calcining time is 1 h;
wherein, the cleaning wastewater in the step (1) is obtained through the following process: uniformly mixing and stirring phosphogypsum and water, standing for layering to remove upper-layer oily suspended matters, and carrying out solid-liquid separation to obtain phosphogypsum solid and cleaning wastewater; the mass of the water is 5 times of that of the phosphogypsum; and (3) performing solid-liquid separation to obtain liquid which can be used as water for stirring the phosphogypsum.
And (3) detecting the filtrate obtained by solid-liquid separation in the step (2), wherein the content of soluble phosphorus in the filtrate is 2.6ppm, and testing the hydroxyapatite in the step (3), wherein the contents of F, Fe and V are respectively 0.546%, 0.117% and 0.004%.
Example 4
The embodiment provides a method for preparing hydroxyapatite based on phosphogypsum cleaning wastewater, which comprises the following steps:
(1) carrying out pH adjustment and stirring on the cleaning wastewater, and then carrying out solid-liquid separation to obtain a filtrate; wherein the end point pH of the pH adjustment is 5.77; the agent in the pH adjustment comprises calcium carbonate; the purity of the calcium carbonate is more than 95 percent; the stirring time is 30 min; the rotating speed of the stirring is 300 rpm;
(2) heating and stirring the filtrate obtained in the step (1), adjusting the pH value of the filtrate by a first method, cooling the filtrate, adjusting the pH value of the filtrate by a second method, stirring the filtrate for reaction, and performing solid-liquid separation to obtain a solid; wherein the heating temperature in the heating and stirring process is 50 ℃; the heating and stirring time is 2 hours; the end point pH of the first pH adjustment is 2.23; the first pH adjusting agent comprises phosphoric acid; the final temperature of the cooling is 25 ℃; the end point pH of the second pH adjustment is 11.94; the second pH adjusting agent comprises calcium oxide and calcium hydroxide; the reaction time is 30 min; the rotating speed of the heating and stirring is 200 rpm; the stirring speed in the reaction is 200 rpm;
(3) washing and calcining the solid obtained in the step (2) in sequence to obtain the hydroxyapatite; the washing cleaning agent comprises water and/or ethanol; the washing time is 3-5 min; the calcining temperature is 800 ℃; the calcining time is 2 h;
wherein, the cleaning wastewater in the step (1) is obtained through the following process: uniformly mixing and stirring phosphogypsum and water, standing for layering to remove upper-layer oily suspended matters, and carrying out solid-liquid separation to obtain phosphogypsum solid and cleaning wastewater; the mass of the water is 3 times of that of the phosphogypsum; and (3) performing solid-liquid separation to obtain liquid which can be used as water for stirring the phosphogypsum.
And (3) detecting the filtrate obtained by solid-liquid separation in the step (2), wherein the content of soluble phosphorus in the filtrate is 0.2ppm, and testing the hydroxyapatite in the step (3), wherein the contents of F, Fe and V are respectively 0.315%, 0.085% and 0.003%.
In the present invention, the phosphogypsum used in examples 1 and 2 is from a chemical plant in Anhui province, and has a soluble phosphorus content of 0.28% and a soluble fluorine content of 0.32%, and the phosphogypsum used in examples 3 and 4 is from a chemical plant in Guizhou province, and has a soluble phosphorus content of 0.56% and a soluble fluorine content of 0.08%.
Comparative example 1
The only difference from example 1 is that step (2) was carried out without carrying out step (1). And (3) detecting the filtrate obtained by solid-liquid separation in the step (2), wherein the content of soluble phosphorus in the filtrate is 2.0ppm, and testing the hydroxyapatite in the step (3), wherein the contents of F, Fe and V are 7.665%, 0.757% and 0.018% respectively.
According to the embodiment and the comparative example, the phosphogypsum-based water washing pretreatment is carried out, no toxic reagent is added in the whole process, the reaction condition is mild, the problem of secondary pollution caused by phosphogypsum water washing pretreatment can be solved, and the environment is not damaged. In addition, the content of soluble phosphorus is reduced by firstly adjusting the pH value of the calcium carbonate without causing the pH value to be raised too high, but the pH value range of the solution after the adjustment is not suitable for the existence of soluble fluorine and heavy metal ions, thereby achieving the aim of removing impurities. In addition, the filtrate obtained by filtering the prepared hydroxyapatite can be used for cleaning phosphogypsum, so that the water can be recycled, and the consumption of water resources is reduced.
The applicant declares that the present invention illustrates the detailed structural features of the present invention through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must be implemented depending on the above detailed structural features. It should be understood by those skilled in the art that any modifications of the present invention, equivalent substitutions of selected components of the present invention, additions of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.
The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.
It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition.
In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.
Claims (10)
1. A method for preparing hydroxyapatite based on phosphogypsum cleaning wastewater is characterized by comprising the following steps:
(1) carrying out pH adjustment and stirring on the cleaning wastewater, and then carrying out solid-liquid separation to obtain a filtrate;
(2) heating and stirring the filtrate obtained in the step (1), adjusting the pH value of the filtrate by a first method, cooling the filtrate, adjusting the pH value of the filtrate by a second method, stirring the filtrate for reaction, and performing solid-liquid separation to obtain a solid;
(3) and (3) sequentially washing and calcining the solid obtained in the step (2) to obtain the hydroxyapatite.
2. The method of claim 1, wherein the end point pH of the pH adjustment of step (1) is 5.5 to 6.0;
preferably, the agent in the pH adjustment of step (1) comprises calcium carbonate;
preferably, the calcium carbonate has a purity > 95%.
3. The method of claim 1 or 2, wherein the stirring time of step (1) is 20-40 min;
preferably, the rotation speed of the stirring in the step (1) is 200-300 rpm.
4. The method according to any one of claims 1 to 3, wherein the temperature of heating in the heating and stirring of step (2) is 50 to 70 ℃;
preferably, the heating and stirring time of the step (2) is 0.5-2 h;
preferably, the rotation speed of the heating and stirring in the step (2) is 100-200 rpm.
5. The method of any one of claims 1-4, wherein the endpoint pH of the first pH adjustment of step (2) is < 3;
preferably, the first pH adjusting agent of step (2) comprises phosphoric acid.
6. The method of any one of claims 1-5, wherein the end temperature of the cooling of step (2) is 20-30 ℃.
7. The method of any one of claims 1-6, wherein the endpoint pH of the second pH adjustment of step (2) is from 10 to 12;
preferably, the second pH adjusting agent of step (2) comprises calcium oxide and/or calcium hydroxide;
preferably, the reaction time of the step (2) is 20-40 min;
preferably, the rotation speed of stirring in the reaction in the step (2) is 200-300 rpm.
8. The method of any one of claims 1-7, wherein the washed cleaning agent of step (3) comprises water and/or ethanol;
preferably, the washing time of the step (3) is 3-5 min;
preferably, the temperature of the calcination in the step (3) is 700-900 ℃;
preferably, the calcination time of the step (3) is 1-4 h.
9. The method according to any one of claims 1 to 8, wherein the washing wastewater of step (1) is obtained by: uniformly mixing and stirring phosphogypsum and water, standing for layering to remove upper-layer oily suspended matters, and carrying out solid-liquid separation to obtain phosphogypsum solid and cleaning wastewater;
preferably, the mass of the water is 3-20 times of that of the phosphogypsum;
preferably, the liquid obtained by the solid-liquid separation in the step (2) can be used as water when the phosphogypsum is stirred.
10. A method according to any one of claims 1-9, characterized in that the method comprises the steps of:
(1) carrying out pH adjustment and stirring on the cleaning wastewater, and then carrying out solid-liquid separation to obtain a filtrate; wherein the pH value of the pH adjusting end point is 5.5-6.0; the agent in the pH adjustment comprises calcium carbonate; the purity of the calcium carbonate is more than 95 percent; the stirring time is 20-40 min; the rotating speed of the stirring is 200-300 rpm;
(2) heating and stirring the filtrate obtained in the step (1), adjusting the pH value of the filtrate by a first method, cooling the filtrate, adjusting the pH value of the filtrate by a second method, stirring the filtrate for reaction, and performing solid-liquid separation to obtain a solid; wherein the heating temperature in the heating and stirring process is 50-70 ℃; the heating and stirring time is 0.5-2 h; the end point pH of the first pH adjustment is < 3; the first pH adjusting agent comprises phosphoric acid; the final cooling temperature is 20-30 ℃; the end point pH value of the second pH adjustment is 10-12; the second pH adjusting agent comprises calcium oxide and/or calcium hydroxide; the reaction time is 20-40 min; the rotating speed of the heating and stirring is 100-200 rpm; the stirring speed in the reaction is 200-300 rpm;
(3) washing and calcining the solid obtained in the step (2) in sequence to obtain the hydroxyapatite; the washing cleaning agent comprises water and/or ethanol; the washing time is 3-5 min; the calcining temperature is 700-900 ℃; the calcining time is 1-4 h;
wherein, the cleaning wastewater in the step (1) is obtained through the following process: uniformly mixing and stirring phosphogypsum and water, standing for layering to remove upper-layer oily suspended matters, and carrying out solid-liquid separation to obtain phosphogypsum solid and cleaning wastewater; the mass of the water is 3-20 times of that of the phosphogypsum; and (3) performing solid-liquid separation to obtain liquid which can be used as water for stirring the phosphogypsum.
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| CN113603127A (en) * | 2021-08-18 | 2021-11-05 | 江苏一夫科技股份有限公司 | Method for concentrated sulfuric acid treatment of calcium chloride wastewater and co-production of chemical gypsum |
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| CN113603127A (en) * | 2021-08-18 | 2021-11-05 | 江苏一夫科技股份有限公司 | Method for concentrated sulfuric acid treatment of calcium chloride wastewater and co-production of chemical gypsum |
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