CN113045089B - Method for refining and purifying etching waste liquid - Google Patents
Method for refining and purifying etching waste liquid Download PDFInfo
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- CN113045089B CN113045089B CN202110275561.2A CN202110275561A CN113045089B CN 113045089 B CN113045089 B CN 113045089B CN 202110275561 A CN202110275561 A CN 202110275561A CN 113045089 B CN113045089 B CN 113045089B
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Abstract
The invention provides a method for refining and purifying etching waste liquid, which comprises the following steps: sequentially evaporating, cooling and crystallizing waste liquid generated by the etching process to obtain a crude ammonium bifluoride product and steam; re-dissolving the crude ammonium bifluoride product, adsorbing, and performing nanofiltration on the adsorbed solution to obtain a refined etching solution; condensing the steam to obtain condensate, and performing reverse osmosis on the condensate after adsorption to obtain reverse osmosis concentrated water and reverse osmosis fresh water. The method comprises the steps of evaporating, cooling and crystallizing etching waste liquid, primarily purifying to obtain a crude ammonium bifluoride product, dissolving the crude ammonium bifluoride product, and then refining through adsorption and nanofiltration treatment to obtain the ammonium bifluoride with electronic-grade purity; the steam in the evaporation stage of the method is separated and purified through condensation, adsorption and reverse osmosis treatment, so that the comprehensive treatment of the etching waste liquid is integrally realized; the method has the advantages of simple process, low cost of raw materials and operation, and wide application range.
Description
Technical Field
The invention belongs to the technical field of waste liquid treatment, and relates to a method for refining and purifying etching waste liquid.
Background
With the rapid development of semiconductor and microelectronic technologies, the application range of electronic chips is increasingly expanding, and etching of micro-scale patterns is an important factor affecting the performance of chips based on the requirement of chip refinement. The etching technology is an important process for chip production, wherein the wet etching is to use some specific chemical reagents to decompose part of a film to be etched and convert the film into a soluble compound to enter a water phase so as to achieve the purpose of etching. According to the choice of chip material, the commonly used etchant mainly comprises hydrofluoric acid, usually ammonium fluoride is used as a buffer to be mixed with the hydrofluoric acid to control the etching rate, meanwhile, an organic additive or a surfactant is also added to improve the wettability, and based on the complexity of the components of the etching solution, waste liquid and waste gas are generated after the etching is finished, and if the waste liquid and the waste gas are directly discharged without treatment, serious environmental damage can be caused.
Based on the selection of an etchant and an etching chip, waste liquid generated in an etching process usually contains fluorine, ammonium ions and the like, and also contains metal ions, organic components and the like.
CN 110104842A discloses a method for treating fluorine-containing ammonium-containing etching wastewater, which comprises the following steps: adding ammonium bicarbonate into the wastewater, carrying out solid-liquid separation after reaction, and absorbing tail gas by water; concentrating the filtrate after solid-liquid separation and the water solution absorbing the tail gas by a reverse osmosis system to prepare fresh water and concentrated water; washing the solid obtained by solid-liquid separation with the fresh water, drying to obtain white carbon black, and recycling the washing water to reverse osmosis treatment; adding white carbon black into concentrated water, adding boric acid, stirring, reacting at a constant temperature, filtering, and drying; and roasting the dried solid to obtain the boron-containing heteroatom molecular sieve. The method for treating the etching waste water is to convert components such as fluorine, ammonium and the like into other substances together, so that the components cannot be used in the etching process again, and the method has the advantages of numerous operation steps and high raw material and operation cost.
CN 106517244A discloses a method for producing ammonium bifluoride from fluorine-containing etching waste liquid, which comprises the following steps: removing impurities from the fluorine-containing etching waste liquid to remove sulfate ions, chloride ions and nitrate ions in the waste liquid; introducing liquid ammonia into the waste liquid after impurity removal until no new precipitate is generated, heating to discharge unreacted ammonia gas for recycling treatment, and filtering and separating the liquid and the precipitate to obtain filtrate and filter residue; and adding hydrofluoric acid into the obtained filtrate until the pH value is not changed any more, and evaporating, crystallizing, washing, drying and crushing to obtain the ammonium bifluoride product. According to the method, the silicon-containing component is precipitated by additionally adding ammonia, and fluorine in the waste liquid is recovered, but the obtained precipitate has limited purity and cannot be applied to precision industries such as semiconductors and electrons, which have extremely high requirements on purity.
In summary, for the treatment and recycling of the waste liquid of the etching process, a proper refining process needs to be selected, so that the components of the waste liquid can be fully separated and recycled, the purity of the product is greatly improved, the process operation is simplified, and the cost is reduced.
Disclosure of Invention
Aiming at the problems in the prior art, the invention aims to provide a method for refining and purifying etching waste liquid, which is characterized in that the etching waste liquid is subjected to evaporation, cooling and crystallization treatment, a crude ammonium bifluoride product is extracted, and then the ammonium bifluoride product is subjected to adsorption and nanofiltration treatment to be refined, so that high-purity ammonium bifluoride is obtained, the purification and utilization of evaporation steam are realized, the comprehensive recycling and utilization of the etching waste liquid are integrally realized, the method is simple in process and low in cost, and the problem of pollution easily caused by the waste liquid can be effectively solved.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a method for refining and purifying etching waste liquid, which comprises the following steps:
(1) Sequentially evaporating, cooling and crystallizing waste liquid generated by the etching process to obtain a crude ammonium bifluoride product and steam;
(2) Re-dissolving the crude ammonium bifluoride product obtained in the step (1), adsorbing, and performing nanofiltration on the adsorbed solution to obtain a refined etching solution;
(3) Condensing the steam obtained in the step (1) to obtain condensate, adsorbing the condensate, and performing reverse osmosis to obtain reverse osmosis concentrated water and reverse osmosis fresh water, wherein the reverse osmosis concentrated water returns to the step (1) to be mixed with the waste liquid;
wherein, the operation sequence of the step (2) and the step (3) is not limited.
According to the invention, as for an etching process adopted in the preparation process of a semiconductor device, waste liquid can be generated after etching, the etching waste liquid is subjected to evaporation, cooling and crystallization treatment, primary purification is carried out to obtain a crude ammonium bifluoride product, then the crude ammonium bifluoride product is dissolved and then is subjected to adsorption and nanofiltration treatment to be refined to obtain electronic-grade ammonium bifluoride, the product utilization value is high, the application field is expanded, and steam in the evaporation stage is subjected to condensation, adsorption and reverse osmosis treatment to carry out separation and purification, so that the comprehensive treatment of the etching waste liquid is integrally realized, and the damage of direct discharge to the environment is avoided; the method is simple to operate, the used raw materials and the operation cost are low, and the application range is wide.
In the method, the steps (2) and (3) are respectively the subsequent treatment of the two products obtained in the step (1), and the two products belong to parallel operation without the requirement of the sequence.
The following technical solutions are preferred technical solutions of the present invention, but not limited to the technical solutions provided by the present invention, and technical objects and advantageous effects of the present invention can be better achieved and achieved by the following technical solutions.
As a preferable embodiment of the present invention, the object to be processed in the etching process in the step (1) includes a semiconductor chip.
Preferably, the etching process of step (1) uses an etchant composition comprising any one or a combination of at least two of hydrofluoric acid, ammonium fluoride or ammonium bifluoride, and the combination is exemplified by, but not limited to: combinations of hydrofluoric acid and ammonium fluoride, ammonium fluoride and ammonium bifluoride, combinations of hydrofluoric acid, ammonium fluoride and ammonium bifluoride, and the like.
In the present invention, the etchant used is usually hydrofluoric acid or ammonium fluoride, depending on the semiconductor silicon material most used for the chip, and both are preferably used together, and the latter can be used as a buffer to control the etching rate.
Preferably, the composition of the etchant further comprises calcium ions, magnesium ions and organic matter.
Preferably, the organic substance comprises a surfactant and/or an organic additive.
As a preferred embodiment of the present invention, the temperature of the evaporation in the step (1) is 80 to 100 ℃, for example, 80 ℃, 85 ℃, 90 ℃, 95 ℃ or 100 ℃, but the evaporation is not limited to the above-mentioned values, and other values not shown in the above-mentioned range are also applicable.
Preferably, the evaporation in step (1) results in an evaporated concentrate having a concentration of 50 to 80 wt.%, such as 50 wt.%, 55 wt.%, 60 wt.%, 65 wt.%, 70 wt.%, 75 wt.%, or 80 wt.%, but not limited to the recited values, and other unrecited values within the range of values are equally applicable.
Preferably, the evaporative concentrate has a pH of 3 to 4, such as 3, 3.2, 3.5, 3.8, or 4, but is not limited to the recited values, and other values not recited within this range are equally applicable.
In the invention, the waste liquid generated by the etching process is evaporated, so that not only can the redundant ammonia component be removed, but also the concentration of the residual fluorine-containing ammonium-containing salt can be improved, and the proportion of fluorine and ammonium is controlled by controlling the pH value of the evaporation concentrated solution, thereby crystallizing to obtain the ammonium bifluoride.
As a preferred embodiment of the present invention, the cooling rate of the cooled crystal in the step (1) is 5 to 15 ℃/h, for example, 5 ℃/h, 6 ℃/h, 8 ℃/h, 10 ℃/h, 12 ℃/h, 14 ℃/h or 15 ℃/h, etc., but the cooling rate is not limited to the above-mentioned values, and other values not shown in the above-mentioned range of values are also applicable.
Preferably, the temperature of the cooled crystals in step (1) is reduced to 20 to 30 ℃, such as 20 ℃, 22 ℃, 24 ℃, 25 ℃, 27 ℃ or 30 ℃, but is not limited to the recited values, and other values not recited in the range of values are also applicable.
In the invention, because the solubility of the ammonium bifluoride increases with the increase of the temperature and the ammonium bifluoride is easy to decompose when the temperature is higher, the crystallization is carried out by adopting a cooling crystallization mode, and the control of the cooling rate is based on the consideration that the crystallization speed can be improved when the ammonium bifluoride crystallization needs to form crystal seeds in the early stage and the subsequent cooling is carried out for a large amount of precipitation.
As a preferred embodiment of the present invention, the purity of the crude ammonium acid fluoride in step (1) is 96-98 wt%, for example, 96wt%, 96.5wt%, 97wt%, 97.5wt% or 98wt%, but not limited to the recited values, and other values not recited in the above range are also applicable.
Preferably, the impurity composition of the crude ammonium bifluoride in step (1) comprises calcium ions, magnesium ions and silicon ions.
Preferably, the steam of step (1) comprises water, ammonia gas and hydrogen fluoride.
In the invention, the impurities of the ammonium bifluoride mainly come from silicate in the chip in the etching process and organic matters added in the etching agent, and in the evaporation process of the etching waste liquid, ammonia, volatile organic matters and other components form steam.
As a preferable technical scheme of the invention, the crude ammonium bifluoride in the step (2) is dissolved by water.
Preferably, the adsorbent used in the adsorption in step (2) comprises activated carbon or organic adsorption resin.
Preferably, the adsorbate of the adsorbent comprises a surfactant and/or an organic additive.
Preferably, after the adsorption in the step (2) is finished, solid-liquid separation is carried out to obtain an adsorbed liquid and a saturated adsorbent.
In a preferred embodiment of the present invention, the nanofiltration membrane used in the nanofiltration in step (2) has a molecular weight cut-off of 200 or more, for example, 200, 250, 300, 350, 400, 450, or 500, but is not limited to the above-mentioned values, and other values not shown in the above-mentioned range are also applicable, preferably 200 to 400.
Preferably, the nanofiltration in step (2) is performed at a pressure of 0.3 to 0.5MPa, such as 0.3MPa, 0.32MPa, 0.35MPa, 0.38MPa, 0.4MPa, 0.42MPa, 0.45MPa or 0.5MPa, but not limited to the recited values, and other values not recited in the numerical range are also applicable.
Preferably, a permeate liquid and a retentate liquid are obtained after nanofiltration in the step (2), the permeate liquid is refined etching liquid, and the retentate liquid is subjected to subsequent treatment.
In the present invention, the nanofiltration membrane can retain divalent and multivalent ions, such as calcium and magnesium ions and ions such as fluorosilicate, and the obtained retentate can be directly returned to be mixed with the waste etching solution for treatment, so that impurity ions are introduced, and thus additional treatment is required.
Preferably, the refined etching solution in step (2) is an electronic-grade ammonium bifluoride solution.
As a preferred technical scheme of the invention, the adsorbent used for the adsorption in the step (3) comprises activated carbon or organic adsorption resin.
Preferably, the adsorbate of the adsorbent comprises a volatile small molecule organic.
Preferably, after the adsorption in step (3) is completed, solid-liquid separation is performed to obtain an adsorbed liquid and a saturated adsorbent.
In a preferred embodiment of the present invention, the reverse osmosis in step (3) is performed at a pressure of 0.8 to 1.5MPa, such as 0.8MPa, 0.9MPa, 1.0MPa, 1.4MPa or 1.5MPa, but the reverse osmosis is not limited to the above-mentioned values, and other values not shown in the above-mentioned range are also applicable.
Preferably, the composition of the reverse osmosis concentrated water in the step (3) comprises fluorine and ammonium.
Preferably, the reverse osmosis fresh water in the step (3) is returned to the step (2) for dissolving the crude ammonium bifluoride product.
As a preferred technical scheme of the invention, the method comprises the following steps:
(1) Evaporating waste liquid generated by a semiconductor chip etching process to obtain steam and evaporated concentrated liquid, wherein the evaporation temperature is 80-100 ℃, the concentration of the evaporated concentrated liquid is 50-80 wt%, the pH value is 3-4, the evaporated concentrated liquid is cooled and crystallized, the cooling rate of the cooled and crystallized is 5-15 ℃/h, the cooled and crystallized temperature is reduced to 20-30 ℃, and a crude ammonium bifluoride product is obtained, and the purity of the crude ammonium bifluoride product is 96-98 wt%;
(2) Redissolving the ammonium bifluoride crude product obtained in the step (1) by using water, adsorbing by using active carbon or organic adsorption resin, after adsorption, carrying out solid-liquid separation to obtain adsorbed liquid and saturated adsorbent, carrying out nanofiltration on the adsorbed liquid, wherein the interception molecular weight of the nanofiltration membrane is more than 200, the pressure of the nanofiltration is 0.3-0.5 MPa, obtaining permeate and retentate after the nanofiltration, wherein the permeate is refined etching solution, and the retentate is subjected to subsequent treatment;
(3) Condensing the steam obtained in the step (1) to obtain condensate, adsorbing the condensate by using activated carbon or organic adsorption resin, performing reverse osmosis on the obtained adsorbed liquid, wherein the pressure of the reverse osmosis is 0.8-1.5 MPa to obtain reverse osmosis concentrated water and reverse osmosis fresh water, returning the reverse osmosis concentrated water to the step (1) to be mixed with the waste liquid, and returning the reverse osmosis fresh water to the step (2) to dissolve a crude product of ammonium bifluoride;
wherein, the operation sequence of the step (2) and the step (3) is not limited.
Compared with the prior art, the invention has the following beneficial effects:
(1) According to the method, the etching waste liquid is subjected to evaporation, cooling crystallization treatment and preliminary purification to obtain a crude ammonium bifluoride product, the crude ammonium bifluoride product is dissolved and then is subjected to adsorption and nanofiltration treatment to be refined to obtain the ammonium bifluoride with electronic-grade purity, the product has high utilization value, and the application field is expanded;
(2) The steam in the evaporation stage of the method is separated and purified through condensation, adsorption and reverse osmosis treatment, so that the comprehensive treatment of the etching waste liquid is integrally realized, and the recovery rate of fluorine and ammonium in the waste liquid can reach more than 99 percent;
(3) The method has simple process, low cost of used raw materials and operation, wide application range and capability of effectively solving the problem of pollution caused by easy discharge of waste liquid.
Drawings
Fig. 1 is a process flow diagram of a method for refining and purifying an etching waste liquid provided in embodiment 1 of the present invention.
Detailed Description
In order to better illustrate the present invention and facilitate the understanding of the technical solutions of the present invention, the present invention is further described in detail below. However, the following examples are only simple examples of the present invention and do not represent or limit the scope of the present invention, which is defined by the claims.
The invention provides a method for refining and purifying etching waste liquid, which comprises the following steps:
(1) Sequentially evaporating, cooling and crystallizing waste liquid generated by an etching process to obtain a crude product of ammonium bifluoride and steam;
(2) Re-dissolving the crude ammonium bifluoride product obtained in the step (1), adsorbing, and performing nanofiltration on the solution after adsorption to obtain a refined etching solution;
(3) Condensing the steam obtained in the step (1) to obtain condensate, adsorbing the condensate, and performing reverse osmosis to obtain reverse osmosis concentrated water and reverse osmosis fresh water, wherein the reverse osmosis concentrated water returns to the step (1) to be mixed with the waste liquid;
wherein, the operation sequence of the step (2) and the step (3) is not limited.
The following are typical, but non-limiting, examples of the present invention:
example 1:
the embodiment provides a method for refining and purifying etching waste liquid, wherein a process flow chart of the method is shown in figure 1, and the method comprises the following steps:
(1) Evaporating waste liquid generated by a semiconductor silicon chip etching process, wherein an etchant adopted by the etching process comprises hydrofluoric acid, ammonium bifluoride and sodium dodecyl benzene sulfonate, the evaporation treatment temperature is 90 ℃, steam and evaporation concentrated solution are obtained, the concentration of the evaporation concentrated solution is 65wt%, the pH value is 3.5, the evaporation concentrated solution is cooled and crystallized, the cooling rate of the cooling crystallization is 10 ℃/h, the cooling is carried out to 25 ℃, and a crude ammonium bifluoride product with the purity of 97.0wt% is obtained;
(2) Redissolving the ammonium bifluoride crude product obtained in the step (1) by using water, adsorbing by using activated carbon, wherein an adsorbate is an organic matter added into an etchant, filtering and separating after adsorption is finished, and the obtained adsorbed liquid is subjected to nanofiltration, wherein the cut-off molecular weight of the nanofiltration membrane is more than 300, the pressure of the nanofiltration is 0.4MPa, a permeate liquid and a cut-off liquid are obtained after the nanofiltration, the permeate liquid is the refined etchant, and the cut-off liquid contains calcium ions, magnesium ions and fluosilicic acid ions and is subjected to additional treatment;
(3) Condensing the steam obtained in the step (1) to obtain condensate, wherein the condensate is a fluorine-containing ammonia-containing solution, the condensate is adsorbed by using activated carbon, the obtained adsorbed solution is subjected to reverse osmosis, the pressure of the reverse osmosis is 1.0MPa, reverse osmosis concentrated water and reverse osmosis fresh water are obtained, the reverse osmosis concentrated water is returned to the step (1) and mixed with the waste liquid, and the reverse osmosis fresh water is returned to the step (2) and used for dissolving the crude ammonium bifluoride.
In the embodiment, the method is adopted to treat the etching waste liquid, the obtained ammonium bifluoride can reach the electronic-grade purity, and the recovery rate of fluorine and ammonium in the etching waste liquid can reach 99.2%.
Example 2:
the embodiment provides a method for refining and purifying etching waste liquid, which comprises the following steps:
(1) Evaporating waste liquid generated by a semiconductor silicon chip etching process, wherein an etchant adopted by the etching process comprises hydrofluoric acid, ammonium fluoride and sodium dodecyl benzene sulfonate, the evaporation treatment temperature is 100 ℃, steam and evaporation concentrated liquid are obtained, the concentration of the evaporation concentrated liquid is 80wt%, the pH value is 3, the evaporation concentrated liquid is cooled and crystallized, the cooling rate of the cooling and crystallization is 15 ℃/h, the cooling is carried out to 20 ℃, and a crude ammonium bifluoride product with the purity of 97.8wt% is obtained;
(2) Redissolving the crude ammonium bifluoride product obtained in the step (1) by using water, adsorbing by using active carbon, wherein an adsorbate is an organic matter added into an etchant, after adsorption is finished, filtering and separating are carried out, the obtained adsorbed liquid is subjected to nanofiltration, the cut-off molecular weight of the nanofiltration membrane is more than 350, the pressure of the nanofiltration is 0.5MPa, a permeate liquid and a retentate liquid are obtained after the nanofiltration, the permeate liquid is the refined etchant, and the retentate liquid contains calcium ions, magnesium ions and fluosilicic acid ions, and additional treatment is carried out;
(3) Condensing the steam obtained in the step (1) to obtain a condensate, wherein the condensate is a fluorine-containing ammonia-containing solution, the condensate is adsorbed by using activated carbon, the obtained adsorbed solution is subjected to reverse osmosis, the reverse osmosis pressure is 1.5MPa, reverse osmosis concentrated water and reverse osmosis fresh water are obtained, the reverse osmosis concentrated water is returned to the step (1) and mixed with the waste liquid, and the reverse osmosis fresh water is returned to the step (2) and used for dissolving the crude ammonium bifluoride product.
In the embodiment, the method is adopted to treat the etching waste liquid, the obtained ammonium bifluoride can reach the electronic grade purity, and the recovery rate of fluorine and ammonium in the etching waste liquid can reach 99.5%.
Example 3:
the embodiment provides a method for refining and purifying etching waste liquid, which comprises the following steps:
(1) Evaporating waste liquid generated by a semiconductor silicon chip etching process, wherein an etchant adopted by the etching process comprises ammonium fluoride, ammonium bifluoride and sodium dodecyl sulfate, the evaporation treatment temperature is 80 ℃, steam and an evaporation concentrated solution are obtained, the concentration of the evaporation concentrated solution is 50wt%, the pH value is 4, the evaporation concentrated solution is cooled and crystallized, the cooling rate of the cooling crystallization is 5 ℃/h, the cooling is carried out to 30 ℃, and a crude ammonium bifluoride product with the purity of 96.2wt% is obtained;
(2) Condensing the steam obtained in the step (1) to obtain a condensate, wherein the condensate is a fluorine-containing ammonia-containing solution, the condensate is adsorbed by using activated carbon, the obtained adsorbed solution is subjected to reverse osmosis, the reverse osmosis pressure is 0.8MPa, reverse osmosis concentrated water and reverse osmosis fresh water are obtained, the reverse osmosis concentrated water is returned to the step (1) and mixed with the waste liquid, and the reverse osmosis fresh water is used for dissolving an ammonium bifluoride crude product in the step (3);
(3) And (2) re-dissolving the ammonium bifluoride crude product obtained in the step (1) by using water, adsorbing by using activated carbon, taking an adsorbed substance as an organic matter added into an etchant, filtering and separating after adsorption is finished, and performing nanofiltration on the obtained adsorbed solution, wherein the cut-off molecular weight of the nanofiltration membrane is more than 200, the pressure of the nanofiltration is 0.3MPa, and a permeate solution and a cut-off solution are obtained after the nanofiltration, the permeate solution is the refined etchant, and the cut-off solution contains calcium ions, magnesium ions and fluosilicic acid ions and is subjected to additional treatment.
In the embodiment, the method is adopted to treat the etching waste liquid, the obtained ammonium bifluoride can reach the electronic grade purity, and the recovery rate of fluorine and ammonium in the etching waste liquid can reach 99.0%.
Example 4:
the embodiment provides a method for refining and purifying etching waste liquid, which comprises the following steps:
(1) Evaporating waste liquid generated by a semiconductor silicon chip etching process, wherein an etchant adopted by the etching process comprises ammonium bifluoride and sodium dodecyl sulfate, the evaporation treatment temperature is 95 ℃, steam and evaporation concentrated liquid are obtained, the concentration of the evaporation concentrated liquid is 75wt%, the pH value is 3.2, the evaporation concentrated liquid is cooled and crystallized, the cooling rate of the cooling crystallization is 12 ℃/h, the cooling is carried out to 22 ℃, and a crude product of the ammonium bifluoride is obtained, and the purity of the crude product is 97.5wt%;
(2) Redissolving the ammonium bifluoride crude product obtained in the step (1) by using water, adsorbing by using organic adsorption resin, wherein an adsorbate is an organic matter added into an etchant, after adsorption is finished, filtering and separating are carried out, the obtained adsorbed liquid is subjected to nanofiltration, the cut-off molecular weight of the nanofiltration membrane is more than 250, the pressure of the nanofiltration is 0.35MPa, a permeate liquid and a cut-off liquid are obtained after the nanofiltration, the permeate liquid is the refined etchant, and the cut-off liquid contains calcium ions, magnesium ions and fluosilicic acid ions and is subjected to additional treatment;
(3) Condensing the steam obtained in the step (1) to obtain a condensate, wherein the condensate is a fluorine-containing ammonia-containing solution, the condensate is adsorbed by using organic adsorption resin, the obtained adsorbed solution is subjected to reverse osmosis, the reverse osmosis pressure is 1.2MPa, reverse osmosis concentrated water and reverse osmosis fresh water are obtained, the reverse osmosis concentrated water is returned to the step (1) and mixed with the waste liquid, and the reverse osmosis fresh water is returned to the step (2) and used for dissolving the crude ammonium bifluoride product.
In the embodiment, the method is adopted to treat the etching waste liquid, the obtained ammonium bifluoride can reach the electronic-grade purity, and the recovery rate of fluorine and ammonium in the etching waste liquid can reach 99.3%.
Example 5:
the embodiment provides a method for refining and purifying etching waste liquid, which comprises the following steps:
(1) Evaporating waste liquid generated by a semiconductor silicon chip etching process, wherein an etchant adopted by the etching process comprises ammonium fluoride, stearic acid and sodium dodecyl benzene sulfonate, the evaporation treatment temperature is 85 ℃, steam and evaporation concentrated solution are obtained, the concentration of the evaporation concentrated solution is 60wt%, the pH value is 3.8, the evaporation concentrated solution is cooled and crystallized, the cooling rate of the cooling crystallization is 8 ℃/h, the cooling is carried out to 27 ℃, and a crude ammonium bifluoride product with the purity of 96.6wt% is obtained;
(2) Condensing the steam obtained in the step (1) to obtain a condensate, wherein the condensate is a fluorine-containing ammonia-containing solution, the condensate is adsorbed by using organic adsorption resin, the obtained adsorbed solution is subjected to reverse osmosis, the reverse osmosis pressure is 1.4MPa, reverse osmosis concentrated water and reverse osmosis fresh water are obtained, the reverse osmosis concentrated water is returned to the step (1) and mixed with the waste liquid, and the reverse osmosis fresh water is used for dissolving a crude ammonium bifluoride product in the step (3);
(3) And (2) re-dissolving the ammonium bifluoride crude product obtained in the step (1) by using water, adsorbing by using organic adsorption resin, wherein an adsorbate is an organic matter added into an etchant, after adsorption is completed, filtering and separating are carried out, the obtained adsorbed liquid is subjected to nanofiltration, the cut-off molecular weight of the nanofiltration membrane is more than 400, the pressure of the nanofiltration is 0.45MPa, a permeate liquid and a cut-off liquid are obtained after the nanofiltration, the permeate liquid is the refined etchant, and the cut-off liquid contains calcium ions, magnesium ions and fluosilicic acid ions and is subjected to additional treatment.
In the embodiment, the method is adopted to treat the etching waste liquid, the obtained ammonium bifluoride can reach the electronic grade purity, and the recovery rate of fluorine and ammonium in the etching waste liquid can reach 99.2%.
Comparative example 1:
this comparative example provides a method for purification of an etching waste liquid, which is referred to the method of example 1 except that: the step (2) does not comprise an adsorption step, namely, nanofiltration is directly carried out after the crude ammonium bifluoride product is dissolved.
In the comparative example, because the adsorption operation is not carried out, organic impurities in the ammonium bifluoride solution cannot be removed, the purity of the refined ammonium bifluoride etching solution is 98.5wt%, the purity cannot reach the electronic grade purity, and the method is difficult to be applied to the precision industry fields of semiconductors, electronics and the like.
Comparative example 2:
this comparative example provides a process for purification of etching waste liquid, which is referred to the process of example 1 except that: and (3) the step (2) does not comprise a nanofiltration step, namely, the crude ammonium bifluoride product is dissolved and then only absorbed, and the obtained absorbed liquid is the refined etching liquid.
In the comparative example, because nanofiltration operation is not carried out, calcium ions, magnesium ions, fluorosilicate ions and the like in the ammonium bifluoride solution cannot be removed, the purity of the refined ammonium bifluoride etching solution is 98.8wt%, the purity of the ammonium bifluoride etching solution cannot reach the electronic grade purity, and the ammonium bifluoride etching solution is difficult to apply to the fields of precision industries such as semiconductors and electronics.
It can be seen from the above examples and comparative examples that, the method of the present invention obtains crude ammonium bifluoride by evaporating, cooling and crystallizing the etching waste liquid, preliminarily purifying, dissolving the crude ammonium bifluoride, and then refining by adsorption and nanofiltration treatment to obtain the ammonium bifluoride with electronic grade purity, the product has high utilization value, and the application field is expanded; the steam in the evaporation stage of the method is separated and purified through condensation, adsorption and reverse osmosis treatment, so that the comprehensive treatment of the etching waste liquid is integrally realized, and the recovery rate of fluorine and ammonium in the waste liquid can reach more than 99 percent; the method has simple process, low cost of raw materials and operation, wide application range and capability of effectively solving the problem of pollution caused by waste liquid discharge.
The applicant states that the present invention is illustrated in detail by the above examples, but the present invention is not limited to the above detailed methods, i.e. it is not meant that the present invention must rely on the above detailed methods for its implementation. It will be apparent to those skilled in the art that any modification, equivalent substitution of the process of the invention and addition of ancillary operations, selection of specific means, etc., of the present invention are within the scope and disclosure of the invention.
Claims (22)
1. A method for refining and purifying etching waste liquid is characterized by comprising the following steps:
(1) Sequentially evaporating and cooling and crystallizing waste liquid generated by an etching process, wherein the evaporation temperature is 80-100 ℃, the cooling rate of the cooling and crystallizing is 5-15 ℃/h, so as to obtain a crude product of ammonium bifluoride and steam, and the steam comprises water, ammonia gas and hydrogen fluoride;
(2) Re-dissolving the crude ammonium bifluoride product obtained in the step (1), and then adsorbing by using activated carbon or organic adsorption resin, wherein an adsorbed substance comprises a surfactant and/or an organic additive, and performing nanofiltration on the adsorbed solution, wherein the nanofiltration pressure is 0.3-0.5 MPa, so as to obtain a refined etching solution;
(3) Condensing the steam obtained in the step (1) to obtain condensate, adsorbing the condensate and performing reverse osmosis to obtain reverse osmosis concentrated water and reverse osmosis fresh water, wherein the adsorbed substances comprise volatile small molecular organic matters, and the reverse osmosis concentrated water is returned to the step (1) and mixed with the waste liquid;
wherein, the operation sequence of the step (2) and the step (3) is not limited.
2. The method according to claim 1, wherein the processing object of the etching process of step (1) comprises a semiconductor chip.
3. The method according to claim 1, wherein the etching process of step (1) adopts an etchant composition comprising any one of hydrofluoric acid, ammonium fluoride or ammonium bifluoride or a combination of at least two of the hydrofluoric acid, the ammonium fluoride or the ammonium bifluoride.
4. The method of claim 3, wherein the composition of the etchant further comprises calcium, magnesium ions, and organic matter.
5. The method of claim 4, wherein the organic substance comprises a surfactant and/or an organic additive.
6. The process of claim 1, wherein said evaporating of step (1) results in an evaporated concentrate having a concentration of 50 to 80 wt.%.
7. The method of claim 6, wherein the evaporative concentrate has a pH of 3 to 4.
8. The method as claimed in claim 1, wherein the temperature of the cooled crystal in the step (1) is reduced to 20-30 ℃.
9. The method according to claim 1, wherein the purity of the crude ammonium bifluoride in step (1) is 96-98 wt%.
10. The method according to claim 1, wherein the impurity composition of the crude ammonium acid fluoride in step (1) comprises calcium ions, magnesium ions and silicon ions.
11. The method of claim 1, wherein the crude ammonium bifluoride in step (2) is dissolved with water.
12. The method according to claim 1, wherein after the adsorption in step (2) is completed, solid-liquid separation is performed to obtain an adsorbed liquid and a saturated adsorbent.
13. The method as claimed in claim 1, wherein the nanofiltration membrane used in the nanofiltration of step (2) has a molecular weight cut-off of 200 or more.
14. The method as claimed in claim 13, wherein the nanofiltration membrane used in the nanofiltration of step (2) has a molecular weight cut-off of 200 to 400.
15. The method according to claim 1, wherein a permeate and a retentate are obtained after nanofiltration in step (2), the permeate is a refined etching solution, and the retentate is subjected to subsequent treatment.
16. The method according to claim 1, wherein the refined etching solution in step (2) is an electronic grade ammonium bifluoride solution.
17. The method according to claim 1, wherein the adsorbent used in the adsorption in step (3) comprises activated carbon or organic adsorption resin.
18. The method according to claim 1, wherein after the adsorption in step (3) is completed, solid-liquid separation is performed to obtain an adsorbed liquid and a saturated adsorbent.
19. The method of claim 1, wherein the reverse osmosis in the step (3) is performed at a pressure of 0.8 to 1.5MPa.
20. The method of claim 1, wherein the composition of the reverse osmosis concentrate of step (3) comprises fluorine and ammonium.
21. The method of claim 1 wherein the reverse osmosis fresh water of step (3) is returned to step (2) for dissolving the crude ammonium acid fluoride.
22. Method according to claim 1, characterized in that it comprises the following steps:
(1) Evaporating waste liquid generated by a semiconductor chip etching process to obtain steam and evaporated concentrated liquid, wherein the evaporation temperature is 80-100 ℃, the concentration of the evaporated concentrated liquid is 50-80 wt%, the pH value is 3-4, the evaporated concentrated liquid is cooled and crystallized, the cooling rate of the cooled and crystallized is 5-15 ℃/h, the cooled and crystallized temperature is reduced to 20-30 ℃, and a crude ammonium bifluoride product is obtained, and the purity of the crude ammonium bifluoride product is 96-98 wt%;
(2) Redissolving the ammonium bifluoride crude product obtained in the step (1) by using water, adsorbing by using active carbon or organic adsorption resin, after adsorption, carrying out solid-liquid separation to obtain adsorbed liquid and saturated adsorbent, carrying out nanofiltration on the adsorbed liquid, wherein the interception molecular weight of the nanofiltration membrane is more than 200, the pressure of the nanofiltration is 0.3-0.5 MPa, obtaining permeate and retentate after the nanofiltration, wherein the permeate is refined etching solution, and the retentate is subjected to subsequent treatment;
(3) Condensing the steam obtained in the step (1) to obtain condensate, adsorbing the condensate by using activated carbon or organic adsorption resin, performing reverse osmosis on the obtained adsorbed liquid, wherein the reverse osmosis pressure is 0.8-1.5 MPa to obtain reverse osmosis concentrated water and reverse osmosis fresh water, returning the reverse osmosis concentrated water to the step (1) to be mixed with the waste liquid, and returning the reverse osmosis fresh water to the step (2) to be used for dissolving a crude ammonium bifluoride product;
wherein, the operation sequence of the step (2) and the step (3) is not limited.
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| CN114349231A (en) * | 2022-01-17 | 2022-04-15 | 江苏电科环保有限公司 | Method for treating low-concentration fluorine-containing wastewater |
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