CN115557635A - Method for treating nitric acid type tin stripping wastewater - Google Patents

Method for treating nitric acid type tin stripping wastewater Download PDF

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CN115557635A
CN115557635A CN202211214938.4A CN202211214938A CN115557635A CN 115557635 A CN115557635 A CN 115557635A CN 202211214938 A CN202211214938 A CN 202211214938A CN 115557635 A CN115557635 A CN 115557635A
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tin
nitric acid
stripping wastewater
ammonia water
filtrate
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CN115557635B (en
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宁寻安
张艳林
沈君华
王逸
何峣
路星雯
杨利鸿
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Guangdong University of Technology
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    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F9/00—Multistage treatment of water, waste water or sewage
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/72—Treatment of water, waste water, or sewage by oxidation
    • C02F1/722—Oxidation by peroxides
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/72—Treatment of water, waste water, or sewage by oxidation
    • C02F1/725—Treatment of water, waste water, or sewage by oxidation by catalytic oxidation
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/42—Treatment of water, waste water, or sewage by ion-exchange
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/16—Nitrogen compounds, e.g. ammonia
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/20—Heavy metals or heavy metal compounds
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/20—Heavy metals or heavy metal compounds
    • C02F2101/203—Iron or iron compound
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/16—Nature of the water, waste water, sewage or sludge to be treated from metallurgical processes, i.e. from the production, refining or treatment of metals, e.g. galvanic wastes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

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Abstract

The invention discloses a method for treating nitric acid type tin stripping wastewater, and belongs to the field of tin stripping wastewater treatment. The invention comprehensively treats the nitric acid type tin-stripping wastewater by combining an ammonia water neutralization method and a Fenton-like method, and obtains a nitric acid solution and ammonium sulfate crystals by reduced pressure distillation and evaporation concentration. Controlling the pH value of the precipitation reaction to be 0.8-1.5 by ammonia water, and then adding hydrogen peroxide to react with the hydrogen peroxideFe 3+ And Cu 2+ Forming Fenton-like reaction by the transition metal ions, catalyzing and degrading organic matters, and removing Sn in the tin-stripping wastewater 2+ Oxidized to Sn 4+ The generated n-stannic acid (Sn (H) 2 O) 2 (OH) 4 ) Oxidation to alpha-stannic acid (Sn (OH) 4 ) The purity of the tin product is improved, and finally, a better copper-tin separation effect is realized while the tin recovery rate is kept higher; in addition, concentrated sulfuric acid is added during reduced pressure distillation, so that the recovery rate of nitrate is improved, the recovery rate of nitrate is over 84%, and the nitrogen content of ammonium sulfate is over 21%.

Description

Method for treating nitric acid type tin stripping wastewater
Technical Field
The invention relates to the field of tin-stripping wastewater treatment, and particularly relates to a treatment method of nitric acid type tin-stripping wastewater.
Background
The nitric acid type tin stripping wastewater is wastewater generated in the production process of Printed Circuit Boards (PCBs), generally contains tin, copper, iron, nitric acid, various organic substances such as heterocyclic compounds, polycyclic compounds, polymers and the like, and is directly discharged to seriously pollute the environment, so that the wastewater needs to be treated. In addition, because the potential value of the metallic tin is high, the improvement of the recovery purity of the tin is also very beneficial to the utilization of the subsequent metallic tin.
At present, the tin stripping wastewater is treated by the following main technical routes: acid-base neutralization, flocculation precipitation, electrolysis, solvent extraction, etc. The ammonia water neutralization method has the advantages of small equipment investment, simple process and mild reaction process, and is adopted by most tin-stripping wastewater treatment enterprises. However, the ammonia water neutralization method in the prior art generally has the problems that the pH value is high during tin precipitation, the obtained tin product often contains more copper metal, and the recovery purity of tin is low, and the copper-tin alloy can be generated with copper during tin recovery by a pyrogenic process, so that the separation difficulty of copper and tin is high, the waste of metal tin is finally caused, and the hidden danger of long-term environmental pollution can be even brought. Therefore, the realization of copper and tin separation and recovery is very important when the tin stripping wastewater is treated, but most ammonia water neutralization process processes do not solve the problem.
In order to improve the recovery purity of tin and realize the separation and recovery of copper and tin, the prior art discloses a treatment method of tin stripping waste liquid, which comprises the steps of adding concentrated sulfuric acid to oxidize tin, iron, copper and other metals to generate a metal sulfate solution, then adding ammonia water and carrying out solid-liquid separation, and adjusting the pH value to be between 0.6 and 0.8 to facilitate the precipitation of tin hydroxide and reduce the precipitation of other metal hydroxides as much as possible so as to separate and precipitate the metals.
The prior art also discloses a method for preparing a urea ammonium nitrate solution by using the circuit board tin stripping waste nitric acid, wherein the tin stripping waste nitric acid solution is treated by matching an acid-base neutralization method, a replacement method, a Fenton method and a precipitation method to obtain tin mud, crude copper powder, iron mud and an ammonium nitrate solution, urea is added into the ammonium nitrate solution to obtain the urea ammonium nitrate solution with the total nitrogen content of 28-32%, but the pH value of the acid-base neutralization precipitation reaction in the technical scheme is 4-5, copper ions are easy to precipitate at the moment, the copper-tin separation effect in waste liquid is poor, and the tin purity in the obtained tin mud is low.
Disclosure of Invention
The invention aims to solve the problems that the recovery purity of tin and the recovery rate of nitrate radical are low when nitric acid type tin stripping wastewater is treated by using an ammonia water neutralization method in the prior art, and provides a method for treating nitric acid type tin stripping wastewater.
The technical problem to be solved by the invention is realized by the following technical scheme:
a method for treating nitric acid type tin stripping wastewater specifically comprises the following steps:
s1, adding ammonia water into the tin stripping wastewater of the nitric acid circuit board, adjusting the pH to 0.8-1.5, adding hydrogen peroxide for oxidation, and separating to obtain primary tin mud and primary filtrate; the volume ratio of the tin stripping wastewater to hydrogen peroxide is less than or equal to 10;
s2, adding deionized water or ammonia water into the primary tin mud obtained in the step S1 to remove copper impurities, separating to obtain secondary tin mud and secondary filtrate, and mixing the secondary filtrate with the primary filtrate obtained in the step S1 to obtain mixed filtrate;
s3, adding ammonia water into the mixed filtrate obtained in the step S2, adjusting the pH to 5.5-6, adding a polyacrylamide aqueous solution, and separating to obtain iron-containing copper mud and tertiary filtrate; treating the third filtrate by ion exchange resin to obtain ammonium nitrate solution;
s4, adding concentrated sulfuric acid into the ammonium nitrate solution obtained in the step S3, wherein the molar ratio of nitrate radicals to sulfate radicals is less than or equal to 1:1, carrying out reduced pressure distillation to obtain a nitric acid solution and an ammonium bisulfate solution; and adding ammonia water into the ammonium bisulfate solution, adjusting the pH value to be neutral, evaporating, concentrating, cooling and crystallizing to obtain ammonium sulfate crystals.
Wherein, it is required to be noted that:
in the invention, the ammonia water is firstly added into S1 to control the pH value of the tin stripping wastewater to be 0.8-1.5, and then the hydrogen peroxide is added to enable the hydrogen peroxide to react with Sn 2+ Oxidized to Sn 4+ The optimum precipitation pH of tin ions in the wastewater is reduced to about 1, so that tin can be completely precipitated in the pH range of 0.8-1.5, and Fe in the wastewater is precipitated 3+ And Cu 2+ The optimum precipitation pH of the metal ions is more than 3, the metal ions are not easy to separate out when the pH is 0.8-1.5, the copper-tin separation effect of the treated tin-stripping waste water is good, and the recovery purity of tin in the obtained primary tin mud is high. Meanwhile, the hydrogen peroxide can also oxidize the generated stannic acid into alpha-stannic acid, and the alpha-stannic acid has less adsorption on copper and iron compared with the product of the stannic acid, so that the hydrogen peroxide is added to promote the generation of the alpha-stannic acid, the adsorption of tin precipitates on impurities such as copper, iron and the like can be further reduced, the tin purity is improved, and the recovery purity of tin in the finally obtained primary tin mud is high. In addition, hydrogen peroxide can react with Fe in tin stripping wastewater 3+ And Cu 2+ And the transition metal ions form Fenton-like reaction, so that organic pollutants are catalytically degraded, and the COD concentration in the tin stripping wastewater is effectively reduced. Wherein the volume fraction of the hydrogen peroxide is 27.5-35%, the hydrogen peroxide in the volume fraction is more beneficial to the oxidation of ions in the tin stripping wastewater and the occurrence of Fenton-like reaction, and the preferred volume fraction is 30%.
In addition, the pH value of the precipitation reaction is controlled to be 0.8-1.5, so that hydrogen peroxide can generate more hydroxyl radicals, and the oxidability is stronger. When the pH is lower than 0.8, on one hand, tin is difficult to separate out, so that the recovery rate of tin is not high; on the other hand, the hydrogen peroxide has low activity, so that the orthostannic acid is difficult to be oxidized into alpha-stannic acid, the adsorbed copper impurities become more, the recovered tin mud has low purity, and the copper-tin separation effect is poor; and when the pH value is higher than 1.5, cu in the wastewater 2+ And the copper and the tin are easy to precipitate and are not beneficial to copper and tin separation.
When the volume ratio of the tin stripping wastewater to the hydrogen peroxide is less than or equal to 10, the hydrogen peroxide cannot completely convert Sn into Sn 2+ Oxidized to Sn 4+ And Sn 2+ The pH of the precipitate is high, the tin is difficult to be completely separated out, and the recovery rate of the tin is low; in addition, too little hydrogen peroxide is added to effectively remove COD in the wastewater.
According to the invention, deionized water is added to wash the primary tin mud in S2, copper ions adsorbed on the tin mud can be further removed, the tin in the tin mud exists in an alpha-stannic acid form, the alpha-stannic acid is insoluble in water, and the washing of the deionized water can not cause tin loss, so that the copper-tin separation can be better realized; and the added ammonia water can react with copper ions absorbed in the primary tin mud to generate a copper ammonia complex, so that copper ion impurities doped in the tin mud are removed, and the tin purity in the tin mud is further improved.
The ion exchange resin in the S3 of the invention is preferably a sodium type chelating resin, which is selected to better carry away metal ions in solution, and in addition, cu can be washed out after the regenerated resin is activated by hydrochloric acid 2+ To obtain copper chloride solution and further realize Cu 2+ The utilization of (1).
In the step S4, the recovery of nitrate ions in the form of a nitric acid solution can be promoted by adding concentrated sulfuric acid, and when the molar ratio of nitrate to sulfate is not more than 1:1, a high nitrate recovery rate can be obtained, so that the resource utilization of nitric acid in the nitric acid type tin stripping wastewater is realized. The reduced pressure distillation is to ensure that nitric acid is not decomposed into nitrogen-oxygen gas, so that the recovery rate of nitrate is reduced, and the condition of the reduced pressure distillation is preferably 0.02-0.03 MPa, so that the temperature of distillation can be better controlled under the condition to recover the nitric acid solution. In addition, after reduced pressure distillation in the step S4, distillation components with extremely low front part nitric acid content are discarded, the rear part distillation components are collected to obtain a nitric acid solution with the volume fraction of 23% -33% and an ammonium bisulfate concentrated solution, ammonia water is added into the ammonium bisulfate concentrated solution for further evaporation and concentration to obtain an ammonium sulfate product with the total nitrogen content of more than 21%, the prepared nitric acid solution meets the III class products in the regeneration tin stripping solution (2021-0025T-HG), and the ammonium sulfate crystal meets the class products in the ammonium sulfate (GB 535-1995) standard.
Preferably, in step S1, the pH is 0.8 to 1, more preferably 1.
Preferably, in the step S1, the volume ratio of the tin stripping wastewater to the hydrogen peroxide is 10: (1-2).
When the proportion of the hydrogen peroxide is too high, the cost is increased, and the recovery rate of the tin cannot be further improved.
More preferably, in step S1, the volume ratio of the tin stripping wastewater to the hydrogen peroxide is 10: (1 to 1.5), and more preferably 10.
Preferably, in step S2, the mass ratio of the primary tin mud to the deionized water is 1: (5-11), more preferably 1 (5-10), still more preferably 1.
When the proportion of the deionized water is too low, the washing effect is poor, the removal rate of copper ions is low, and when the proportion of the deionized water is too high, the pH of the tin mud is increased due to the excessive amount of the deionized water being 7, and at the moment, fe 3+ And Cu 2+ The impurity removal effect is also poor.
Preferably, in step S2, after adding deionized water, dilute nitric acid is used to adjust the pH of the solution to 0.9 to 1, more preferably 1.
After the addition of deionized water, the pH of the primary tin sludge will rise, at which point the Fe content will rise 3+ And Cu 2+ The trace amount of precipitate is easy to form and separate out, the purity of the tin mud is influenced, and the pH value is reduced by adding dilute nitric acid, which is beneficial to Fe 3+ And Cu 2+ And the pH is not sufficient to dissolve the alpha-stannic acid without loss of tin.
Preferably, in step S2, the mass ratio of the primary tin mud to the ammonia water is 10: (4 to 7), more preferably 10: (4 to 6), and more preferably 10.
The inventors found that when the mass ratio of the primary tin sludge to the aqueous ammonia is in this range, the complexation reaction can occur better, and that Cu is 2+ The removal effect is better.
Preferably, in step S3, the mass concentration of the polyacrylamide aqueous solution is 0.1%, and the volume ratio of the polyacrylamide aqueous solution to the mixed filtrate is (1-2.5): 10.
preferably, in step S4, the molar ratio of nitrate to sulfate is 1: (1 to 1.4), more preferably 1 (1 to 1.2), still more preferably 1:1.
When the molar ratio of nitrate to sulfate is in the range, the recovery of nitrate can be well promoted, and the problem of high cost caused by excessive addition of the subsequent ammonia water can be avoided.
Preferably, in step S4, the reduced pressure distillation treatment temperature is 80 to 100 ℃.
Compared with the prior art, the technical scheme of the invention has the following beneficial effects:
(1) The invention comprehensively treats the nitric acid type tin-stripping wastewater by adjusting the pH, adding hydrogen peroxide, combining an ammonia water neutralization method and a Fenton-like method, further washing primary tin mud by using deionized water or ammonia water, and removing Fe 3+ And Cu 2+ Finally, the total recovery rate of tin is more than 99%, the tin content in the tin product is more than 55%, and the copper content in the tin product is less than 1.5%, so that the better copper-tin separation effect is realized while the tin recovery rate is kept higher, and the recovery purity of tin is higher.
(2) The invention promotes the formation of nitric acid by adding concentrated sulfuric acid, performs reduced pressure distillation to obtain nitric acid solution, and obtains ammonium sulfate crystal by adding ammonia water to treat ammonium bisulfate, thereby realizing the resource utilization of nitrate radical in nitric acid type tin stripping waste water, and recycling subsequently introduced sulfate radical and ammonium radical, wherein the obtained nitric acid solution conforms to III class products in regeneration tin stripping liquid (2021-0025T-HG), and the ammonium sulfate crystal conforms to class products in ammonium sulfate (GB 535-1995).
Detailed Description
The present invention will be further described with reference to specific embodiments, but the present invention is not limited to the examples in any way. The starting reagents employed in the examples of the present invention are, unless otherwise specified, those that are conventionally purchased. The components of the tin stripping wastewater in the following examples are shown in Table 1.
TABLE 1 main components of tin stripping wastewater
Composition (I) Sn Fe Cu Zn Mn Ni Bi
g/L 87.31 15.75 9.88 0.07 0.07 0.01 0.01
Composition (A) H + COD NO 3 -N Cl - SO 4 2- NO 2 -N NH 3 -N
g/L 3.37 5.45 54.4 5.51 7.5 54.4 0.00
Example 1
A method for treating tin stripping wastewater of a nitric acid circuit board specifically comprises the following steps:
s1, placing a 2L beaker on an electric stirrer, adding 800mL of tin-stripping wastewater at the normal temperature and the rotation speed of 350r/min, and inserting a pH meter below the liquid level; adjusting the pH value to be =1 by 13% ammonia water, and adding 80mL of 30% hydrogen peroxide (namely the volume ratio of the tin stripping wastewater to the hydrogen peroxide is 10; after reacting for 1 hour, centrifugally filtering to obtain primary tin mud and primary filtrate; detecting the contents of tin and copper in the primary filtrate, measuring the COD content in the primary filtrate by a potassium permanganate method, calculating the recovery rate and the COD removal rate of tin and copper by the following formulas, and recording the results in a table 2:
Figure BDA0003876409900000051
Figure BDA0003876409900000052
Figure BDA0003876409900000053
s2, adding deionized water into the primary tin mud, wherein the mass ratio of the primary tin mud to the deionized water is 1:10, at the time, the pH value of the system is 1.8, then the pH =1 is adjusted by dilute nitric acid to wash out a small amount of metal impurities adsorbed in the primary tin sludge, the mixture is stirred for 15 minutes and then centrifugally filtered to obtain secondary tin sludge and secondary filtrate, and the secondary filtrate is mixed with the primary filtrate to obtain a mixed filtrate. Detecting the content of tin and copper in the secondary tin mud and the content of tin in the mixed filtrate, calculating the final recovery rate of tin according to the following formula, and recording the result in table 3:
Figure BDA0003876409900000061
s3, adding 13% ammonia water into the mixed filtrate obtained in the step S2, adjusting the pH value to 5.5, reacting for 5 minutes, and mixing the mixed filtrate with a polyacrylamide aqueous solution (0.1 wt%) according to a volume ratio of 10:2.5 adding the mixture into the system, reacting, and then performing centrifugal filtration to obtain iron-containing copper mud and third filtrate; treating the third filtrate by sodium type ion exchange resin to obtain an ammonium nitrate solution, wherein the main components of the ammonium nitrate solution are recorded in a table 4; then regenerating resin by hydrochloric acid and washing out copper to obtain a copper chloride solution byproduct;
s4, adding 98% concentrated sulfuric acid into the ammonium nitrate solution obtained in the step S3, wherein the molar ratio of nitrate radicals to sulfate radicals is 1:1, carrying out reduced pressure distillation at 0.02MPa and 80 ℃, discarding fractions with the front part having extremely low nitric acid content, and collecting the rear part of the distilled components to obtain a 23.16% nitric acid solution and an ammonium bisulfate concentrated solution, wherein the main components of the nitric acid solution are recorded in Table 5; and adding 13% ammonia water into the ammonium bisulfate concentrated solution, adjusting the pH value to 7, carrying out evaporation concentration, cooling to room temperature, crystallizing to obtain ammonium sulfate crystals, wherein the main components of the ammonium sulfate crystals are recorded in table 6.
Example 2
A method for treating tin-stripping wastewater of a nitric acid circuit board, which is basically the same as in example 1, except that the volume ratio of the tin-stripping wastewater to hydrogen peroxide in step S1 is 10:1.5.
example 3
A method for treating tin-stripping wastewater of a nitric acid circuit board, which is basically the same as in example 1, except that the volume ratio of the tin-stripping wastewater to hydrogen peroxide in step S1 is 10:2.
example 4
A method for treating tin-stripping wastewater of a nitric acid circuit board, which is substantially the same as that in example 1, except that in step S1, ammonia water is used to adjust the pH =0.8.
Example 5
A method for treating tin-stripping wastewater of a nitric acid circuit board, which is substantially the same as that in example 1, except that in step S1, ammonia water is used to adjust the pH =1.5.
Example 6
A method for treating tin-stripping wastewater of a nitric acid circuit board is basically the same as that in example 1, except that in step S2, the mass ratio of tin mud to deionized water is 1:5.
example 7
A method for treating tin-stripping wastewater of a nitric acid type circuit board is basically the same as that in example 1, except that pH is not adjusted by dilute nitric acid in step S2.
Example 8
The treatment method of the tin stripping wastewater of the nitric acid circuit board is basically the same as that in the embodiment 1, except that in the step S2, deionized water is replaced by 13% ammonia water, and the copper content in primary tin mud is measured before the ammonia water is added, wherein the mass ratio of the primary tin mud to the ammonia water is 10:4 adding ammonia water.
Example 9
The treatment method of the tin stripping wastewater of the nitric acid circuit board is basically the same as that in the embodiment 1, except that in the step S2, deionized water is replaced by 13% ammonia water, and the copper content in the primary tin mud is measured before the ammonia water is added, wherein the mass ratio of the primary tin mud to the ammonia water is 10:6 adding ammonia water.
Example 10
A method for treating tin-stripping wastewater of nitric acid circuit boards, which is substantially the same as in example 1 except that the molar ratio of nitrate radicals to sulfate radicals in step S4 is 1:1.2.
example 11
A method for treating tin-stripping wastewater of a nitric acid circuit board, which is substantially the same as that in example 1, except that the molar ratio of nitrate radicals to sulfate radicals in step S4 is 1:1.4.
comparative example 1
A method for treating tin-stripping wastewater of a nitric acid circuit board, which is basically the same as in example 1, except that the volume ratio of the tin-stripping wastewater to hydrogen peroxide in step S1 is 10:0.5.
comparative example 2
The treatment method of the nitric acid type circuit board tin stripping wastewater is basically the same as that in the embodiment 1, except that hydrogen peroxide is not added in the step S1.
Comparative example 3
The treatment method of the nitric acid type circuit board tin stripping wastewater is basically the same as that in the embodiment 1, except that hydrogen peroxide is not added in the step S1, and the pH value is adjusted to 2.5 by ammonia water.
Comparative example 4
A method for treating tin-stripping wastewater of a nitric acid circuit board, which is substantially the same as that in example 1, except that in step S1, ammonia water is used to adjust the pH =0.5.
Comparative example 5
A method for treating tin-stripping wastewater of a nitric acid circuit board, which is substantially the same as that in example 1 except that in step S1, ammonia water is used to adjust the pH =3.
Comparative example 6
A method for treating tin-stripping wastewater of nitric acid circuit boards, which is substantially the same as in example 1 except that the molar ratio of nitrate radicals to sulfate radicals in step S4 is 1:0.8.
results and analysis
Table 2. Removal rate of S1COD and recovery rate of tin and copper in primary tin sludge in examples 1 to 5 and comparative examples 1 to 5
Figure BDA0003876409900000081
The S1 tin and copper recovery rates and COD removal rates of examples 1 to 5 and comparative examples 1 to 5 are reported in Table 2. From examples 1 to 3 and comparative examples 1 to 2, when the volume ratio of the tin stripping wastewater to the hydrogen peroxide is less than 10, the tin recovery rate is more than 99%, and the copper recovery rate is less than 30%, that is, the doping of copper can be reduced during the precipitation and recovery of tin, so that the higher recovery purity of tin is realized, and the COD in the wastewater is effectively removed, the COD removal rate is more than 90%, and the tin recovery rate is further improved with the increase of the added amount of the hydrogen peroxide, when the volume ratio of the tin stripping wastewater to the hydrogen peroxide is 10 2+ The oxidation effect of the tin is not obvious, so that the pH value of the tin is still high, the tin cannot be completely precipitated when the pH value is =1, the recovery rate of the tin is low and is only 93.76%, and the removal rate of COD is also low; if hydrogen peroxide is not added, tin is not completely precipitated when the pH =1, and the recovery rate of tin is low. As can be seen from comparative examples 2 to 3, at pH =2.5, the tin recovery rate could be made 99% or more without adding hydrogen peroxide, but at this time, the copper recovery rate was high, that is, a large amount of copper impurities were also carried in the primary tin sludge, and the tin recovery purity was low.
It is understood from examples 4 to 5 and comparative examples 4 to 5 that the recovery rate of tin is effectively improved, the doping of copper is reduced, and COD in wastewater is removed when the pH value of the solution is adjusted to 0.8 to 1.5. When the pH value is 1.5, the tin recovery rate reaches 100%, the copper recovery rate is lower than 30%, the tin recovery purity is high, and when the pH value is higher than 1.5, the tin recovery rate also reaches 100%, and the COD removal rate also reaches 100%, but other impurities such as copper, iron and the like are separated out due to the increase of the pH value, so that a large amount of copper is doped in the tin mud, the copper recovery rate reaches 43.19%, and the tin recovery purity is low; and when the pH value is lower than 0.8, the tin can not be completely precipitated, the recovery rate of the tin is only 95.68%, and the COD removal rate is also lower than 90%.
TABLE 3 tin-copper content and tin recovery in the secondary tin sludge of examples 1, 6 to 9
Figure BDA0003876409900000091
The primary tin sludge obtained in examples 1, 6 to 9 had a tin content of 44.30%, a copper content of 1.30% and a tin recovery of 99.97%, and was subjected to the treatment of the primary tin sludge in step S2 to obtain the results shown in table 3.
From examples 1 and 6 to 9, it can be seen that the primary tin mud is washed by deionized water to obtain secondary tin mud with higher tin content and lower copper content, and when the mass ratio of the primary tin mud to the deionized water is 1: (5-10), when the washing is carried out when the pH is adjusted to 1 by dilute nitric acid, copper impurities in the primary tin mud can be effectively removed, and the tin treated by the steps is not easy to dissolve in a solution with the pH =1, so that the precipitation of the tin can be effectively inhibited, the loss of the tin during the washing is reduced, and the tin mud with higher tin recovery rate and higher purity can be obtained; if the pH is not adjusted by dilute nitric acid and the deionized water is directly used for washing, the copper impurities can also be removed, but the pH is 1.8 at the moment, more copper and iron can be enriched in the secondary tin mud, and the tin content is relatively low. And deionized water is used for washing, so that the total recovery rate of tin is more than 99.47%, the tin content in the tin product is more than 55.40%, and the copper content in the tin product is less than 0.66%, and the good copper-tin separation effect is realized while the high recovery rate of tin is maintained.
From examples 8 to 9, it is understood that the mass ratio of the primary tin sludge to the ammonia water is 10: (4 to 6), the copper impurities in the tin sludge can be removed by washing with aqueous ammonia, and the copper impurities are mainly removed by forming a copper-ammonia complex with copper by aqueous ammonia, and the dissolution of tin can be suppressed by washing with aqueous ammonia, so that the effect on the final recovery rate of tin is small, but the effect on the removal of copper impurities is not as good as that by washing with deionized water. The method is washed by ammonia water, so that the total recovery rate of tin is up to 99.96 percent, the tin content in the tin product is more than 55.76 percent, the copper content in the tin product is less than 1.18 percent, and the good copper-tin separation effect is realized while the high recovery rate of tin is maintained.
TABLE 4 main components of ammonium nitrate solution in example 1
Composition (I) Sn Fe Cu
g/L 0.002 0 0.002
Composition (I) NO 3 -N NH 3 -N SO 4 2-
mol/L 2.79 3 0.001
As can be seen from table 4, the content of metal ions in the ammonium nitrate solution obtained in example 1 is very low, which further illustrates that after the treatment in steps S1 to S3, metal impurities such as tin, iron, and copper in the tin-stripping wastewater are effectively removed, the content of metal ions in the filtrate is low, and the purity of the obtained ammonium nitrate solution is high.
TABLE 5 nitric acid solutions of example 1, example 10, example 11 and comparative example 6 main Components
Figure BDA0003876409900000101
As can be seen from Table 5, after concentrated sulfuric acid is added and the reduced pressure distillation treatment is carried out, the obtained 23.16-23.98% nitric acid solution has almost no residual impurities and high purity, and meets the industrial standard' regenerated tin stripping solution
(2021-0025T-HG). In comparative example 6, when the amount of concentrated sulfuric acid added was small, a 22.7% nitric acid solution was obtained, which did not meet the class III of (2021-0025T-HG).
TABLE 6 nitrate recovery rates and corresponding components in ammonium sulfate for example 1, example 10, example 11 and comparative example 6
Figure BDA0003876409900000111
As can be seen from Table 6, the treatment method of the invention has high recovery rate of nitrate in the nitric acid type tin-stripping waste water, which is not less than 84%, and the finally obtained ammonium sulfate has little nitrate residue and high purity.
TABLE 7 ammonium sulfate product main component of example 1, example 10, example 11, comparative example 6
Figure BDA0003876409900000112
Figure BDA0003876409900000121
As can be seen from Table 7, the first-class ammonium sulfate crystals meeting the standard ammonium sulfate (GB 535-1995) were obtained by adding ammonia water, and evaporating, concentrating, cooling and crystallizing, and were used as fertilizers, wherein the nitrogen content was more than 21.67%. Although the nitrogen content in the ammonium sulfate obtained in comparative example 6 was also more than 21%, it can be seen from table 5 that the nitrogen content was high because the nitrate residue was large, that is, the ammonium sulfate contained nitrate nitrogen.
It should be understood that the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.

Claims (10)

1. A method for treating nitric acid type tin stripping wastewater is characterized by comprising the following steps:
s1, adding ammonia water into the tin stripping wastewater of the nitric acid circuit board, adjusting the pH to 0.8-1.5, adding hydrogen peroxide for oxidation, and separating to obtain primary tin mud and primary filtrate; the volume ratio of the tin stripping wastewater to hydrogen peroxide is less than or equal to 10;
s2, adding deionized water or ammonia water into the primary tin mud obtained in the step S1 to remove copper impurities, separating to obtain secondary tin mud and secondary filtrate, and mixing the secondary filtrate with the primary filtrate obtained in the step S1 to obtain mixed filtrate;
s3, adding ammonia water into the mixed filtrate obtained in the step S2, adjusting the pH to 5.5-6, adding a polyacrylamide aqueous solution, and separating to obtain iron-containing copper mud and tertiary filtrate; treating the third filtrate by ion exchange resin to obtain ammonium nitrate solution;
s4, adding concentrated sulfuric acid into the ammonium nitrate solution obtained in the step S3, wherein the molar ratio of nitrate radicals to sulfate radicals is less than or equal to 1:1, carrying out reduced pressure distillation to obtain a nitric acid solution and an ammonium bisulfate solution; and adding ammonia water into the ammonium bisulfate solution, adjusting the pH value to be neutral, evaporating, concentrating, cooling and crystallizing to obtain ammonium sulfate crystals.
2. The treatment method according to claim 1, wherein the pH is 0.8 to 1 in step S1.
3. The treatment method according to claim 1, wherein in the step S1, the volume ratio of the tin stripping wastewater to the hydrogen peroxide is 10: (1-2).
4. The treatment method according to claim 3, wherein in the step S1, the volume ratio of the tin stripping wastewater to the hydrogen peroxide is 10: (1-1.5).
5. The treatment method according to claim 1, wherein in the step S2, the mass ratio of the primary tin mud to the deionized water is 1: (5-11).
6. The treatment method according to claim 1, wherein in step S2, after adding deionized water, the pH of the solution is adjusted to 0.9 to 1 with dilute nitric acid.
7. The treatment method according to claim 1, wherein in the step S2, the mass ratio of the primary tin mud to the ammonia water is 10: (4-7).
8. The treatment method according to claim 1, wherein in step S3, the mass concentration of the polyacrylamide aqueous solution is 0.1%, and the volume ratio of the polyacrylamide aqueous solution to the mixed filtrate is (1-2.5): 10.
9. the treatment method according to claim 1, wherein in step S4, the molar ratio of nitrate to sulfate is 1: (1-1.4).
10. The process according to claim 1, wherein the reduced pressure distillation temperature in step S4 is 80 to 100 ℃.
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