CN109678167B - Method for producing boric acid from lithium extraction boron-containing waste liquid - Google Patents
Method for producing boric acid from lithium extraction boron-containing waste liquid Download PDFInfo
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- CN109678167B CN109678167B CN201910163180.8A CN201910163180A CN109678167B CN 109678167 B CN109678167 B CN 109678167B CN 201910163180 A CN201910163180 A CN 201910163180A CN 109678167 B CN109678167 B CN 109678167B
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- C01B35/10—Compounds containing boron and oxygen
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Abstract
The invention provides a method for recovering boric acid from a lithium extraction boron-containing waste liquid, belonging to the technical field of inorganic salt production processes. The method comprises the steps of adjusting the pH value of the lithium extraction boron-containing waste liquid to 3.5-4.5, then discharging the lithium extraction boron-containing waste liquid to a boron salt precipitation field for evaporation crystallization, and evaporating water to form boric acid crystals and boric acid mother liquid; the boric acid crystal and boric acid mother liquor are transferred out of a boron salt field in the form of mixed boric acid feed liquid, and after thickening and deposition, boric acid crystal slurry and supernatant are obtained; refluxing the supernatant to a boron salt precipitation field for further evaporation and crystallization; carrying out solid-liquid separation on the boric acid crystal slurry to obtain boric acid and boron-containing liquid; and refluxing the boron-containing liquid to a boron salt precipitation field for further evaporation and crystallization. The mass percentage of the boric acid obtained by the invention is 87-98%, so that the lithium extraction boron-containing waste liquid is efficiently utilized, and the efficient utilization of the discharged boron-containing waste water is realized; and the method has the advantages of small pollution, low energy consumption, high yield, good crude boron quality and the like.
Description
Technical Field
The invention relates to the technical field of inorganic salt production processes, in particular to a method for producing boric acid from lithium extraction boron-containing waste liquid.
Background
The boric acid is produced almost completely by solid boron ore in the world at present, a large amount of strong acid is consumed in the production process, the operation condition in the production process is poor, the subsequent treatment of waste liquid and solid waste is difficult in technology and large in investment, great obstacles are caused to environmental ecological protection, and certain economic influence is brought to production enterprises.
China's boron mineral exploration reserves (turn B) 2 O 3 ) About 5000 ten thousand tons, most of which are mixed ores of ludwigite and ludwigite, and the other part of which is about 2000 ten thousand tons (turn B) 2 O 3 ) Is a bittern type and salt lake solid boron ore, which is mainly distributed in the modern salt lake of Qinghai and Tibet. Liaoning boron ore resources are all solid ores; accounts for 64 percent of the national reserves, the yield accounts for 88.8 percent of the national boron product yield, and is the main boron ore and boron product in ChinaAnd (5) a product production and processing base. Since the beginning of the production in the fifties of the last century, with the production process of the last half century, the situation of resource exhaustion is approaching.
The reserves of lithium resource and boron resource in salt lake brine and oil field water in China are large, but the percentage contents of the lithium resource and the boron resource in the salt lake brine and the oil field water are both lower by 0.1-3%, and the pH value is as follows: 6-7, the direct development difficulty is large. In recent years, along with the rapid development of the electric automobile industry in China and all over the world, the rapid development of the technology for extracting lithium from salt lake brine and oil field water in China is promoted, and the main production processes comprise a resin adsorption method, an extraction method, an electrodialysis method, a membrane method and the like, and all the production processes have industrial production application examples.
For lithium extraction from salt lake brine and oil field water, boron is an impurity ion, and in order to ensure the quality of a lithium product, boron element must be discharged from the salt lake brine and the oil field water out of a lithium processing system in the form of lithium extraction boron-containing waste liquid in the process of lithium extraction, so that the quality of the lithium product is ensured. In order to improve the comprehensive yield of lithium and the removal efficiency of boron, boron is enriched to a certain extent in the process and then is discharged out of the system in the form of lithium-extracting boron-containing waste liquid. If the lithium-extracting boron-containing waste liquid is not reasonably utilized and developed, not only is the boron resource lost, but also the embarrassment situation that the development of solid boron ore is almost exhausted is difficult to solve. The mass percentage of boric acid in the lithium extraction boron-containing waste liquid is 0.2-6%, and the pH value is as follows: 1-6.5, if forced evaporative crystallization is adopted, the problems of high energy consumption, high cost and serious corrosion of equipment exist, and if salt pan natural evaporative crystallization is adopted, the problems of environmental pollution caused by acid gas evaporation and poor product quality exist if pH adjustment is not carried out in advance, and the mass percentage of boric acid in the crude boric acid is generally 70-85%.
How to scientifically and reasonably solve the major problem is always the direction of cumin to seek effort by scientific workers in the boron field.
Disclosure of Invention
In view of the above, the present invention aims to provide a method for producing boric acid from a lithium extraction boron-containing waste liquid. The method can efficiently recover boron in the lithium extraction boron-containing waste liquid, is environment-friendly and energy-saving, and has good product quality and high comprehensive yield.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a method for preparing boric acid from a lithium extraction boron-containing waste liquid, which comprises the following steps:
(1) Adjusting the pH value of the lithium-extraction boron-containing waste liquid to 3.5-4.5 to obtain the pretreated lithium-extraction boron-containing waste liquid;
(2) Discharging the pretreated lithium-extracting boron-containing waste liquid obtained in the step (1) into a boron-precipitating salt pan, and performing natural evaporation crystallization to obtain high-quality boric acid crystals and boric acid mother liquor;
(3) Transferring the boric acid crystals and part of boric acid mother liquor obtained in the step (2) out of the boron salt precipitation field in the form of a mixture boric acid feed liquid, and then carrying out thickening, wherein the thickening feed liquid is deposited to form boric acid crystal slurry on the lower layer and supernatant on the upper layer;
(4) And (4) carrying out solid-liquid separation on the boric acid crystal slurry in the step (3) to obtain boric acid and boron-containing liquid.
Preferably, the pH value of the lithium extraction boron-containing waste liquid in the step (1) is 0.1-6.5.
Preferably, the source of the boron-containing lithium-extracting waste liquid in the step (1) comprises a lithium extracting process from salt lake brine or a lithium extracting process from oil field water.
Preferably, the reagent used for adjusting the pH of the lithium extraction boron-containing waste liquid in step (1) comprises one or more of quick lime, limestone, magnesium oxide, magnesium sulfate, sodium hydroxide, sodium carbonate, sodium bicarbonate, hydrochloric acid or sulfuric acid.
Preferably, the boron-precipitation salt field in the step (2) is formed by stacking clay, and the bottom of the boron-precipitation salt field is paved with an anti-ultraviolet anti-seepage plastic film material.
Preferably, the liquid level depth in the boron salt analysis field in the step (2) is 1-3 m.
Preferably, the solid content of the concentrated thickening feed liquid in the step (3) is 30-60%.
Preferably, the method further comprises discharging the supernatant obtained in the step (3) into a boron-precipitating salt field for evaporation crystallization.
Preferably, the method further comprises discharging the boron-containing liquid obtained in the step (4) into a boron precipitation salt field for evaporation crystallization.
Preferably, the boric acid in the boric acid obtained in the step (4) is 87-98% by mass.
The method comprises the steps of firstly adjusting the pH value of the lithium-extracting boron-containing waste liquid, and then feeding the lithium-extracting boron-containing waste liquid into a boron salt precipitation field for natural evaporation crystallization; thickening the obtained boric acid crystal and boric acid mother liquor, and carrying out solid-liquid separation to obtain boric acid with the boric acid mass percentage of 87-98%; the method can efficiently recover boron in the lithium-extracting boron-containing waste liquid, energy consumption can be greatly saved by adopting natural evaporation, the environmental pollution caused by the evaporation of acid gas into the atmosphere during the natural evaporation can be avoided by adjusting the pH value, and large-particle single crystal crystals can be obtained by the natural crystallization when the pH value is within the range of 3.5-4.5, so that good product quality is obtained.
Drawings
FIG. 1 is a flow chart of the method for preparing boric acid from a lithium extraction boron-containing waste liquid according to the present invention;
FIG. 2 is a scanning electron micrograph of boric acid crystals obtained in example 1;
FIG. 3 is a scanning electron micrograph of boric acid crystals obtained in example 2;
FIG. 4 is a scanning electron micrograph of a boric acid crystal obtained in example 3;
FIG. 5 is a scanning electron micrograph of boric acid crystals obtained in example 4;
FIG. 6 is a scanning electron micrograph of a boric acid crystal obtained in example 5;
FIG. 7 is a scanning electron micrograph of boric acid crystals obtained in example 6.
Detailed Description
The invention provides a method for preparing boric acid from a lithium extraction boron-containing waste liquid, which comprises the following steps:
(1) Adjusting the pH value of the lithium-extracting boron-containing waste liquid to 3.5-4.5 to obtain the pretreated lithium-extracting boron-containing waste liquid;
(2) Discharging the pretreated lithium-extracting boron-containing waste liquid obtained in the step (1) into a boron-precipitating salt pan, and performing natural evaporation crystallization to obtain high-quality boric acid crystals and boric acid mother liquor;
(3) Transferring the boric acid crystals and part of boric acid mother liquor obtained in the step (2) out of the boric acid salt precipitation field in the form of a mixture boric acid feed liquid, and then carrying out thickening, wherein the thickening feed liquid is deposited to form boric acid crystal slurry on the lower layer and supernatant on the upper layer;
(4) And (4) carrying out solid-liquid separation on the boric acid crystal slurry in the step (3) to obtain boric acid and boron-containing liquid.
The pH value of the lithium-extracting boron-containing waste liquid is adjusted to 3.5-4.5, and the pretreated lithium-extracting boron-containing waste liquid is obtained.
In the invention, the source of the lithium extraction boron-containing waste liquid is preferably a salt lake brine lithium extraction process or an oil field water lithium extraction process. In the invention, the mass concentration of boric acid in the lithium extraction boron-containing waste liquid is preferably 0.1-10%, and the pH value of the lithium extraction boron-containing waste liquid is preferably 0.1-6.5. In the invention, the reagent used for adjusting the pH value of the lithium-extracting boron-containing waste liquid preferably comprises one or more of quick lime, limestone, magnesium oxide, magnesium sulfate, sodium hydroxide, sodium carbonate, sodium bicarbonate, hydrochloric acid and sulfuric acid. In the invention, the pH value of the pretreated lithium-extracting boron-containing waste liquid is 3.5-4.5, and preferably 4.0.
The pH value of the pretreated lithium-extracting boron-containing waste liquid is 3.5-4.5, so that the subsequent evaporation speed in a boron salt precipitation field is high, the corrosion to equipment and the corrosion prevention requirement on equipment materials can be reduced, and excessive investment waste is avoided.
In the obtained pretreated lithium-extracting boron-containing waste liquid, the pretreated lithium-extracting boron-containing waste liquid is discharged into a boron salt precipitation field for natural evaporation crystallization to obtain high-quality boric acid single crystal crystals and boric acid mother liquid.
In the invention, the size of the boron-separating salt pan is preferably 500m × 600m × 2.5m. In the invention, the boron-separating salt field is preferably formed by stacking clay, and the bottom of the boron-separating salt field is paved with an anti-ultraviolet anti-seepage plastic film material. The source of the anti-ultraviolet anti-seepage plastic film material is not particularly limited in the invention, and a commercially available product well known to those skilled in the art can be adopted.
The pretreated lithium-extracting boron-containing waste liquid is naturally evaporated to remove part of fresh water to reach the supersaturated state of boric acid by utilizing natural energy sources such as solar energy, wind energy and the like in a boron-separating salt field, so that boric acid crystals are separated out at the bottom of the salt field and are accompanied with the formation of boric acid mother liquor.
After boric acid crystals and boric acid mother liquor are obtained, the boric acid crystals and part of the boric acid mother liquor are transferred out of a boron salt precipitation field in the form of a mixture boric acid feed liquor, then the boric acid crystal slurry is thickened, and the thickened boric acid crystal slurry at the lower layer and the supernatant at the upper layer are formed by sedimentation of the thickened boric acid feed liquor.
In the invention, the transfer mode of the boric acid solution is preferably that a special machine is adopted to transfer the boric acid crystals and part of the boric acid mother liquor at the bottom of the salt pan in the form of the boric acid solution; the special machinery preferably comprises a water mining ship, a sand mining ship or a crawler belt ore pulp recovery machine and the like. In the present invention, the solid content of the boric acid solution is preferably 5 to 45%, more preferably 20 to 40%, and still more preferably 25 to 35%. The invention has no limit on the amount of the partial boric acid mother liquor in the boric acid mother liquor, and the solid content in the boric acid feed liquor can be 5-45%. In the invention, because the boric acid crystals are difficult to directly collect, the boric acid crystals and part of the boric acid mother liquor are transferred in the form of boric acid slurry.
In the present invention, the apparatus for thickening is preferably a thickener. In the present invention, the solid content of the concentrated thickening feed liquid is preferably 30 to 60%, more preferably 40 to 50%, and still more preferably 45%. The time for the thick thickening liquid to stand is not particularly limited, and the thick thickening liquid only needs to be deposited to form boric acid crystal slurry on the lower layer and supernatant liquid on the upper layer. The invention preferably discharges the supernatant into a boron precipitation salt field for evaporation and crystallization, thereby realizing further boron recovery. In the invention, the parameters of the evaporation crystallization of the supernatant in the boron salt separating field are consistent with the parameters of the evaporation crystallization of the pretreated lithium-extracting boron-containing waste liquid in the boron salt separating field, and are not described herein again.
After obtaining the boric acid crystal slurry and the supernatant, the invention carries out solid-liquid separation on the boric acid crystal slurry to obtain the boric acid and the boron-containing liquid.
In the present invention, the apparatus for performing the solid-liquid separation is preferably a belt filter, a centrifuge, or a filter press, and more preferably a centrifuge. In the present invention, the boric acid is preferably contained in the boric acid in an amount of 87 to 98% by mass. According to the invention, the boron-containing liquid is preferably discharged into a boron salt precipitation field for evaporation crystallization, so that further boron recovery is realized. In the invention, the parameters of the evaporation crystallization of the boron-containing liquid in the boron analysis salt field are consistent with the parameters of the evaporation crystallization of the pretreated lithium-extraction boron-containing waste liquid in the boron analysis salt field, and are not described again.
FIG. 1 is a flow chart of a method for preparing boric acid from a lithium extraction boron-containing waste liquid, which comprises the following steps: adjusting the pH value of the lithium-extracting boron-containing waste liquid to 3.5-4.5, then discharging the lithium-extracting boron-containing waste liquid to a boron salt precipitation field for natural evaporation crystallization, and evaporating water to form boric acid crystals and boric acid mother liquid; transferring the boric acid crystals and the boric acid mother liquor out of a boron salt precipitation field in the form of mixed boric acid liquor, and thickening to obtain boric acid crystal slurry and supernate; refluxing the supernatant to a boron salt precipitation field for further evaporation and crystallization; carrying out solid-liquid separation on the boric acid crystal slurry to obtain boric acid and boron-containing liquid; and refluxing the boron-containing liquid to a boron-precipitation salt field for further evaporation and crystallization.
The following examples are provided to illustrate the method for preparing boric acid from the lithium-extracting boron-containing waste liquid of the present invention in detail, but they should not be construed as limiting the scope of the present invention.
Example 1
Taking the waste liquid containing boron and lithium extracted from the lithium extraction process of the large diesel salt lake brine as an example: the lithium extraction boron-containing waste liquid comprises the following components in mass concentration: h 3 BO 3 4.89％，MgCl 2 0.37％，HCl 0.26％，H 2 O94.48 percent; the pH value of the lithium extraction boron-containing waste liquid is 1.5;
(1) Regulating the pH value of the lithium extraction boron-containing waste liquid to 4.0 by using limestone (calcium carbonate) to obtain the pretreated lithium extraction boron-containing waste liquid;
(2) Discharging the pretreated lithium-extracting boron-containing waste liquid obtained in the step (1) into a boron-separating salt pan by using a conveying pump device, wherein the liquid level depth of the boron-separating salt pan is 3.0m, and naturally evaporating and crystallizing for 300 days to obtain boric acid crystals and boric acid mother liquid; the size of the boron-separating salt field is 20m multiplied by 3m; the boron-separating salt field is preferably formed by stacking clay, and the bottom of the boron-separating salt field is paved with an anti-ultraviolet anti-seepage plastic film material.
(3) Transferring the boric acid crystals and part of boric acid mother liquor obtained in the step (2) from a boron salt precipitation field in the form of a mixture boric acid feed liquid (the solid content is about 15%), and then carrying out thickening for 1.5h by using a thickener to obtain a thickened liquid (the solid content is about 45%); standing the concentrated thickening solution for 1h to obtain boric acid crystal slurry deposited on the lower layer and supernatant liquid on the upper layer; the supernatant fluid flows back to a boron salt precipitation field;
(4) Carrying out solid-liquid separation on the boric acid crystal slurry in the step (3) for 5min by using a centrifugal machine to obtain boric acid and boron-containing liquid; the boron-containing liquid flows back to a boron-separating salt field; the boric acid crystal is long columnar single crystal particles, and a scanning electron micrograph of the boric acid crystal is shown in FIG. 2, and can be seen from FIG. 2: the average particle size of the obtained boric acid crystals is 1.2mm; the boric acid in the boric acid accounts for 96.5 percent by mass.
Example 2
Taking the lithium extraction boron-containing waste liquid generated in the lithium extraction process of the large diesel salt lake brine as an example: the lithium extraction boron-containing waste liquid comprises the following components in mass concentration: h 3 BO 3 5.2％，MgCl 2 0.47％，HCl 0.22％，H 2 O94.11 percent; the pH value of the lithium extraction boron-containing waste liquid is 1.5;
(1) Adjusting the pH value of the lithium-extracting boron-containing waste liquid to 4.0 by using quick lime (calcium oxide) to obtain the pretreated lithium-extracting boron-containing waste liquid;
(2) Discharging the pretreated lithium-extraction boron-containing waste liquid obtained in the step (1) into a boron-precipitation salt field by using a conveying pump device, wherein the liquid level depth of the boron-precipitation salt field is 2.5m, and naturally evaporating and crystallizing for 300 days to obtain boric acid crystals and boric acid mother liquor; the size of the boron precipitation salt field is 20m multiplied by 3m; the boron-separating salt field is preferably formed by stacking clay, and the bottom of the boron-separating salt field is paved with an anti-ultraviolet anti-seepage plastic film material.
(3) Transferring the boric acid crystals and part of boric acid mother liquor obtained in the step (2) from a boron salt precipitation field in the form of a mixture boric acid feed liquid (the solid content is about 25%), and then carrying out thickening for 1.5 hours by using a thickener to obtain a thickened liquid (the solid content is about 45%); standing the concentrated thickening solution for 1.0h to obtain boric acid crystal slurry deposited on the lower layer and supernatant liquid on the upper layer; the supernatant liquid flows back to a boron salt precipitation field;
(4) Carrying out solid-liquid separation on the boric acid crystal slurry in the step (3) for 5min by using a centrifugal machine to obtain boric acid and boron-containing liquid; the boron-containing liquid flows back to a boron-separating salt field; the boric acid crystal is a long cylindrical single crystal particle, and the scanning electron micrograph of the boric acid crystal is shown in fig. 3, and can be seen from fig. 3: the average particle size of the obtained boric acid crystal is 1.1mm; the boric acid in the boric acid accounts for 96.1 percent by mass.
Example 3
Taking the waste liquid containing boron and lithium extracted from the lithium extraction process of the large diesel salt lake brine as an example: the lithium extraction boron-containing waste liquid comprises the following components in mass concentration: h 3 BO 3 5.6％，MgCl 2 0.48％，HCl 0.28％，H 2 O93.64 percent; the pH value of the lithium extraction boron-containing waste liquid is 1.5;
(1) Adjusting the pH value of the lithium-extracting boron-containing waste liquid to 4.0 by using quick lime (calcium oxide) to obtain the pretreated lithium-extracting boron-containing waste liquid;
(2) Discharging the pretreated lithium-extracting boron-containing waste liquid obtained in the step (1) into a boron-precipitation salt pan by using a conveying pump device, wherein the liquid level depth of the boron-precipitation salt pan is 2.0m, and naturally evaporating and crystallizing for 300 days to obtain boric acid crystals and boric acid mother liquid; the size of the boron precipitation salt field is 20m multiplied by 3m; the boron-separating salt field is preferably formed by stacking clay, and the bottom of the boron-separating salt field is paved with an anti-ultraviolet and anti-seepage plastic film material.
(3) Transferring the boric acid crystals and part of boric acid mother liquor obtained in the step (2) from a boron salt precipitation field in the form of a mixture boric acid feed liquid (the solid content is about 30%), and then carrying out thickening for 1.0h by using a thickener to obtain a thickened liquid (the solid content is about 45%); standing the thick thickening liquid for 1.0h to obtain boric acid crystal slurry deposited on the lower layer and supernatant liquid on the upper layer; the supernatant liquid flows back to a boron salt precipitation field;
(4) Carrying out solid-liquid separation on the boric acid crystal slurry in the step (3) for 5min by using a centrifugal machine to obtain boric acid and boron-containing liquid; the boron-containing liquid flows back to a boron-separating salt field; the boric acid crystal is a long columnar single crystal particle, and a scanning electron micrograph of the boric acid crystal is shown in FIG. 4, and it can be seen from FIG. 4 that: the average particle size of the obtained boric acid crystal is 0.8mm; the boric acid accounts for 94.2 percent by mass of the boric acid.
Example 4
Taking the lithium extraction boron-containing waste liquid generated in the lithium extraction process of the large diesel salt lake brine as an example: the lithium extraction boron-containing waste liquid comprises the following components in mass concentration: h 3 BO 3 5.1％，MgCl 2 0.39％，HCl 0.27％，H 2 O94.24 percent; the pH value of the lithium extraction boron-containing waste liquid is 1.5;
(1) Regulating the pH value of the lithium extraction boron-containing waste liquid to 4 by using limestone (calcium carbonate) to obtain the pretreated lithium extraction boron-containing waste liquid;
(2) Discharging the pretreated lithium-extraction boron-containing waste liquid obtained in the step (1) into a boron-precipitation salt field by using a conveying pump device, wherein the liquid level depth is 1.5m, and naturally evaporating and crystallizing for 300 days to obtain boric acid crystals and boric acid mother liquor; the size of the boron-separating salt field is 20m multiplied by 3m; the boron-separating salt field is preferably formed by stacking clay, and an anti-ultraviolet anti-seepage plastic film material is laid at the bottom of the boron-separating salt field;
(3) Transferring the boric acid crystals and part of boric acid mother liquor obtained in the step (2) from a boron salt precipitation field in the form of a mixture boric acid feed liquid (the solid content is about 50%), and then carrying out thickening for 1h by using a thickener to obtain a thickened liquor (the solid content is about 60%); standing the concentrated thickening solution for 1h to obtain boric acid crystal slurry deposited on the lower layer and supernatant liquid on the upper layer; the supernatant liquid flows back to a boron salt precipitation field;
(4) Carrying out solid-liquid separation on the boric acid crystal slurry in the step (3) for 5min by using a centrifugal machine to obtain boric acid and boron-containing liquid; the boron-containing liquid flows back to a boron-separating salt field; the boric acid crystal is needle-shaped and column-shaped mixed crystal, and the scanning electron micrograph thereof is shown in FIG. 5, and it can be seen from FIG. 5 that: the average particle size of the obtained boric acid crystal is 0.5mm, and the mass percentage of boric acid in the boric acid is 90.6%.
Based on this example, the effect of different boron-containing waste liquid depths on boric acid crystals obtained by natural evaporation was investigated, and the results are shown in table 1.
Table 1 table of data of natural evaporation experiment of lithium-extracting boron-containing waste liquid at different depths
Example 5
Taking boron-containing waste liquid in the process of extracting lithium from the wiping salt lake brine as an example (membrane process): the lithium boron-containing waste liquid comprises the following components in mass concentration: h 3 BO 3 0.65％，MgCl 2 0.52％，H 2 O98.83 percent; the pH value of the lithium extraction boron-containing waste liquid is 6.5;
(1) Adjusting the pH value of the lithium extraction boron-containing waste liquid to 4 by using hydrochloric acid (HCl) to obtain the pretreated lithium extraction boron-containing waste liquid;
(2) Discharging the pretreated lithium-extracting boron-containing waste liquid obtained in the step (1) into a boron-precipitating salt pan by using a conveying pump device, wherein the liquid level depth is 3.0m, and naturally evaporating and crystallizing for 300 days to obtain boric acid crystals and boric acid mother liquor; the size of the boron-separating salt field is 20m multiplied by 3m; the boron-separating salt field is preferably formed by stacking clay, and the bottom of the boron-separating salt field is paved with an anti-ultraviolet and anti-seepage plastic film material;
(3) Transferring the boric acid crystals and part of boric acid mother liquor obtained in the step (2) from a boron salt precipitation field in the form of a mixture boric acid feed liquid (the solid content is about 15%), and then carrying out thickening for 1.5h by using a thickener to obtain a thickened liquid (the solid content is about 40%); standing the concentrated thickening solution for 1h to obtain boric acid crystal slurry deposited on the lower layer and supernatant liquid on the upper layer; the supernatant fluid flows back to a boron salt precipitation field;
(4) Carrying out solid-liquid separation on the boric acid crystal slurry in the step (3) for 5min by using a centrifugal machine to obtain boric acid and boron-containing liquid; the boron-containing liquid flows back to a boron-separating salt field; the boric acid crystal is a cylindrical single crystal, and a scanning electron micrograph of the boric acid crystal is shown in FIG. 6, and it can be seen from FIG. 6 that: the average particle size of the obtained boric acid crystals is 1.2mm; the boric acid accounts for 94.6 percent by mass of the boric acid.
Example 6
The lithium extraction boron-containing waste liquid produced in the lithium extraction process of the large-diesel-denier salt lake brine is used as a raw material, and comprises the following components in mass concentration: h 3 BO 3 5.5％，MgCl 2 0.45％，HCl 0.25％，H 2 O93.8 percent; the lifting handleThe pH value of the lithium boron-containing waste liquid is 1.5;
(1) Respectively taking 8 parts of 250L of the lithium extraction boron-containing waste liquid, and respectively adjusting the pH value of the lithium extraction boron-containing waste liquid to 1.5, 2.0, 3.0, 3.5, 4.0, 4.5, 5.0 and 6.0 by using limestone (calcium carbonate) to obtain the pretreated lithium extraction boron-containing waste liquid;
(2) Respectively pouring the pretreated lithium-extracting boron-containing waste liquid obtained in the step (1) into 8 containers of 0.6m multiplied by 0.8m, wherein the liquid level depth is 0.7m, placing the containers in a salt pan evaporation simulation device, and evaporating for 100 days to obtain boric acid crystals and boric acid mother liquor; the container is a square cylinder made of plastic materials and ordered by external processing, and the inner wall of the container is paved with an anti-ultraviolet anti-seepage plastic film material;
(3) And (3) removing supernatant liquid with the height of about 70L of 0.2m from the residual liquid after evaporation in the step (2) by a siphoning method, transferring the obtained boric acid crystals and part of boric acid mother liquor from a boron precipitation container to a centrifuge in the form of mixture boric acid feed liquid, and performing solid-liquid separation for 4min to compare the quality of wet products. The test data are in table 2 below.
Table 2 table of natural evaporation experimental data of lithium-extracting boron-containing waste liquid at different pH
The scanning electron micrograph of the obtained boric acid crystal is shown in FIG. 7, wherein in FIG. 7, a represents a flaky crystal; the b picture is needle crystal, the c picture is column crystal.
The embodiment shows that the growth of boric acid in the form of single crystal can be promoted by controlling the liquid level depth of the boron-separating salt field and the pH value of the waste liquid, the average particle size of the product reaches more than 1.0mm, and the entrainment of impurity-containing mother liquid is reduced, which is beneficial to the improvement of the product quality; otherwise, boric acid is formed in a needle or sheet form, the average particle size of the product is below 0.5mm, and a large amount of sheet crystals and fine needle crystals carry a large amount of impurity-containing mother liquor in the crystals and among the crystals, so that the yield of boron is influenced, the operation cost of the product is increased, and the quality of the product is difficult to be well improved.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and amendments can be made without departing from the principle of the present invention, and these modifications and amendments should also be considered as the protection scope of the present invention.
Claims (8)
1. A method for preparing boric acid from a lithium extraction boron-containing waste liquid is characterized by comprising the following steps:
(1) Adjusting the pH value of the lithium-extracting boron-containing waste liquid to 4.0-4.5 to obtain the pretreated lithium-extracting boron-containing waste liquid;
(2) Discharging the pretreated lithium-extraction boron-containing waste liquid obtained in the step (1) into a boron precipitation salt field, and performing natural evaporation crystallization to obtain high-quality boric acid crystals and boric acid mother liquor;
(3) Transferring the boric acid crystals and part of boric acid mother liquor obtained in the step (2) out of the boric acid salt precipitation field in the form of a mixture boric acid feed liquid, and then carrying out thickening, wherein the thickening feed liquid is deposited to form boric acid crystal slurry on the lower layer and supernatant on the upper layer;
(4) Carrying out solid-liquid separation on the boric acid crystal slurry in the step (3) to obtain boric acid and boron-containing liquid;
the reagent used for adjusting the pH value of the lithium-extracting boron-containing waste liquid in the step (1) comprises one or more of quick lime, limestone, magnesium oxide, magnesium sulfate, sodium hydroxide, sodium carbonate or sodium bicarbonate;
the depth of the liquid level in the boron salt separation field in the step (2) is 1-3 m.
2. The method for preparing boric acid from the lithium-extracting boron-containing waste liquid according to claim 1, wherein the pH value of the lithium-extracting boron-containing waste liquid in the step (1) is 0.1-6.5.
3. The method for preparing boric acid from the lithium-extracting boron-containing waste liquid according to claim 1 or 2, wherein the source of the lithium-extracting boron-containing waste liquid in the step (1) comprises a salt lake brine lithium extracting process or an oil field water lithium extracting process.
4. The method for preparing boric acid from the lithium-extracting boron-containing waste liquid according to claim 1, wherein the boron-separating salt field in the step (2) is formed by stacking clay, and an anti-ultraviolet impermeable plastic film material is laid at the bottom.
5. The method for preparing the boric acid from the lithium-extracting boron-containing waste liquid according to claim 1, wherein the solid content of the concentrated thickening feed liquid in the step (3) is 30-60%.
6. The method for preparing boric acid from the lithium-extracting boron-containing waste liquid according to claim 1, further comprising discharging the supernatant obtained in the step (3) into a boron-precipitating salt field for evaporation crystallization.
7. The method for preparing boric acid from the lithium-extracting boron-containing waste liquid according to claim 1, further comprising discharging the boron-containing liquid obtained in the step (4) into a boron precipitation salt field for evaporation and crystallization.
8. The method for preparing the boric acid from the lithium-extracting boron-containing waste liquid according to claim 1, wherein the boric acid obtained in the step (4) is 87-98% in percentage by mass.
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| CN102602953A (en) * | 2012-04-12 | 2012-07-25 | 青海锂业有限公司 | Method for preparing high borosilicate glass industry-level boric acid by utilizing salt lake lithium-extracting mother solution |
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| AR001918A1 (en) * | 1995-05-12 | 1997-12-10 | Minera Salar De Atacama S A So | Procedure for the extraction of boron contained in brines from natural or industrial salt flats |
| AR001916A1 (en) * | 1996-02-20 | 1997-12-10 | Minera Salar De Atacama S A So | Process to extract boron from natural or industrial brines using solvent extraction |
| CN1302988C (en) * | 2005-01-26 | 2007-03-07 | 李洪岭 | Crystallization control and whitening control method for producing boric acid with salt lake type boron mineral |
| CN1289394C (en) * | 2005-01-26 | 2006-12-13 | 李洪岭 | Prepn process of recovering boric acid and magnesium sulfate from evaporation concentrated boric acid mother liquor in salt field |
| CN101676206A (en) * | 2008-09-19 | 2010-03-24 | 于网林 | Boron extraction technology |
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