GB2261443A - Process for recovering tin from a waste liquid containing tin recovered from printed circuit boards - Google Patents
Process for recovering tin from a waste liquid containing tin recovered from printed circuit boards Download PDFInfo
- Publication number
- GB2261443A GB2261443A GB9124378A GB9124378A GB2261443A GB 2261443 A GB2261443 A GB 2261443A GB 9124378 A GB9124378 A GB 9124378A GB 9124378 A GB9124378 A GB 9124378A GB 2261443 A GB2261443 A GB 2261443A
- Authority
- GB
- United Kingdom
- Prior art keywords
- tin
- waste liquid
- range
- filtrate
- ions
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B25/00—Obtaining tin
- C22B25/06—Obtaining tin from scrap, especially tin scrap
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
- C22B3/20—Treatment or purification of solutions, e.g. obtained by leaching
- C22B3/44—Treatment or purification of solutions, e.g. obtained by leaching by chemical processes
- C22B3/46—Treatment or purification of solutions, e.g. obtained by leaching by chemical processes by substitution, e.g. by cementation
-
- 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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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Life Sciences & Earth Sciences (AREA)
- Environmental & Geological Engineering (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Geology (AREA)
- Removal Of Specific Substances (AREA)
- Manufacture And Refinement Of Metals (AREA)
Abstract
A process for recovering tin from a waste liquid containing recovered tin including the steps of (a) reducing an oxidizer in the waste liquid by adding a reducer, or by heating the waste liquid, (b) precipitating out metal ions other than those of tin and filtrating the resulted liquid into filtrate and precipitates, (c) removing fluorine ions from the filtrate by adding a liquid containing aluminium ions, (d) replacing the tin ions contained in the filtrate and filtrating the resultant solution into a filtrate and tin powder or granules, (e) refining the obtained tin powder or granules by smelting. <IMAGE>
Description
PROCESS FOR RECOVERING TIN FROM A WASTE LIOUID CONTAINING
TIN RECOVERED FROM PRINTED CIRCUIT BOARDS
BACKGROUND OF THE INVENTION
The present invention relates to a process for
recovering tin from liquid containing tin. More
particularly, the present invention relates to a
process for recovering tin from a waste liquid
containing tin recovered from printed circuit boards,
which comprises controlled conditions and steps so as
to reduce the tin content of the waste liquid and to
yield tin of high purity.
In the field of producing printed circuit boards,
because of the requirements of enhancing the quality
and the development of surf ace mounting devices (SMD),
the method of spraying tin has been widely adapted
instead of the conventional method of soldering. This
method can prevent the destruction of the printed
circuit boards by eliminating the repeated heating
during production and by avoiding the drawbacks of pool
production on account of the increase in circuit
density on the boards. Therefore, this method is now
widely adapted in producing printed circuit boards.
However, there is a very important step when adopting
this method; that is, the tin (or tin/copper) of the
circuit of the PC boards must be recovered so that tin
can be sprayed upon the circuit. As a result, a large
amount of waste liquid containing the recovered tin is
produced, which contains high concentrations of tin ions. These ions are environmental contaminants.
There are three types of waste liquid containing tin recovered from printed circuit boards: nitric acid type, organic acid type, and inorganic acid type. The nitric acid type has the serious drawback of etching the circuit on the board, thus forming nitrogen oxide (NOx) during the reaction between nitric acid and tin ion, which can seriously contaminate the atmosphere.
Thus, this type of process is obsolete. As for the waste liquid produced by the organic acid type process, because it has the drawbacks of low reaction speed and requiring high chemical oxygen demand (COD), it is now scarcely used in industry. Currently, the most popular process for recovering tin from printed circuit board is the inorganic acid type process, in which ammonium hydrogen fluoride (NH4HF2) is employed, and which possesses the characteristics of rapid reaction and easy operation.
Although the inorganic acid type process for recovering tin from printed circuit boards possesses many positive characteristics, if the waste liquid produced thereby is not adequately treated before being expelled into the environment, as other industrial waste liquid, it will also seriously contaminate the environment.
There are two major contaminative sources for the inorganic acid type process:
(a) Tin ions. Although tin ions can be removed from the waste liquid by a precipitating process, tin ions are amphoteric and will not form precipitates if the pH value of the solution is too high or too low.
Therefore, the existence of tin ions will narrow the operation range for treating the waste liquid.
(b) Fluorine ions. In the waste liquid, the fluorine ion concentration contained therein can be up to 100g/l, which will seriously contaminate the environment.
The current art usually treats this type of waste liquid by adding zinc (Zn) powder, so as to replace the tin ions. However, its efficacy is very low and cannot treat fluorine ions simultaneously, and the zinc ions to be high pollution source of the waste water. Thus, it is not an economical and powerful process for treating this type of waste liquid.
The present invention is developed to treat waste liquid containing tin recovered from printed circuit boards, so as to make the waste liquid meet the standards of environmental protection. Furthermore, the tin recovered from the liquid waste can be reused.
SUMMARY FO THE INVENTION
It is, therefore, a primary object of the present invention to provide a process for recovering tin from waste liquid containing tin recovered from printed circuit boards.
Another object of the present invention is to provide a process for treating waste liquid produced from the production of printed circuit boards, in which the waste liquid is treated by a series of chemical steps, comprising adding precipitants and reducers and controlling the pH value, the temperature, and the rotation speed of the liquid, so as to obtain a liquid, in which the concentration of tin ions is below 10 ppm, meeting the requirements of environment protection when it is expelled.
A further object of the present invention is to prpvide a process for recovering tin from waste liquid in which the purity of the recovered tin is more than 99.9%.
Another object of the present invention is to provide a process for recovering tin from waste liquid containing tin recovered from printed circuit boards, in which fluorine ions contained in the waste liquid can be precipitated out in the form of aluminum trifluoride (A12F6) or ammonium fluoalumunate [(NH4)2A1F6], which can then be used as raw material for aluminium smelting.
A further object of the present invention is to provide a process for recovering tin from waste liquid containing recovered tin which has high efficacy and low cost.
Additional features and objects will become apparent from the detailed description of the preferred embodiment, with appropriate reference to the attached drawings, and are accomplished by a process for recovering tin from waste liquid containing recovered tin.
BRIEF DESCRIPTION OF THE DRAWING
Fig. 1 is a flow chart of the process in accordance with the present application.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Throughout the specification and claims, all parts and percentages are by weight, temperatures are in degrees Celsius, and rotation speeds are in revolutions per minute, unless otherwise indicated. In order to illustrate the invention more fully, reference is made to the accompanying schematic drawing. All values are merely exemplary or calculated.
Referring to Fig. 1, a flow chart showing a process for recovering tin from a waste liquid containing tin recovered from printed circuit boards in accordance with the present invention is shown, which process includes primarily the steps of reducing the oxidizer contained in the waste liquid, precipitating out metal ions other than those of tin ion, removing fluorine ions, replacing the tin ions, filtrating out filtrating out the tin, and refining the tin, wherein the temperature, pH value and the rotation speed of the treated solution is controlled such that the solid tin is obtained in high yield and purity, and at the same time, the final solution will contain tin ions in a concentration below 0.3 ppm before being expelled to the surroundings.
The following illustrates a best mode for recovering tin from a waste liquid containing tin recovered from printed circuit boards, which process comprises the steps of:
(A) Reducing an Oxidizer in the Waste Liquid
The oxidizer contained in the waste liquid can be reduced by adding a reducer or metal tin. Suitably, the reducer is selected from a group comprising sodium sulfite (Na2SO3), sodium hydrogen sulfite (NaHSO3), and formaldehyde. The added amount of the reducer is greater than or equal to one equivalent which is required to reduce the oxidizer. During the addition the reducer, the pH value of the waste liquid is kept within a range of 1.0-8.0, and the temperature is kept within the range of room temperature to 70 C. The reaction time is more than 10 minutes, and the liquid is kept motionless or has a rotation speed in the range of 30 to 200 rpm after adding the reducer.
Alternatively, the oxidizer contained in the waste liquid may be reduced by waste materials containing tin. The waste materials containing tin not only reduce the oxidizer in the waste liquid but also increase the content of tin in the waste liquid and enhance the yield of tin. Usually, the added amount of the waste materials containing tin is in the range of 1.0 to 1.2 times equivalent which is required to reduce the oxidizer.
Hydrogen peroxide contained in the waste liquid can be removed by directly heating the liquid. The operational requirements of heating the waste liquid are as follows: (1) adjusting the pH value of the waste liquid to be less than three, (2) keeping the temperature of the waste liquid in the range of 450 to 800C, and (3) setting the reaction time dependent on the residury amount of the hydrogen peroxide.
Additionally, the heating reaction may be accelerated by adding one or more salts including ferrite, such as ferric chloride (FeC13), ferrous chloride (FeC12), and ferrous sulfate (FeSO4)
(B). PreciDitatina Out Metal Ions Other Than Those of Tin and Filtrating the Resulted Liquid into Filtrate and Precipitates
The metal ions other than tin can be precipitated by adding appropriate precipitants. The appropriate precipitants comprise sodium oxalate (Na2C204), sodium carbonate (Na2CO3), or sodium sulfide (Na2S). The added amount of the precipitant is greater than or equal to one equivalent which is required to precipitate the ions other than tin ion. The pH value of the waste liquid is kept within the range of 1.0 to 8.0, and the temperature is kept within the range of 150 to 650C.The rotation speed is kept within the range of 60 to 300 rpm.
The metal ions other than tin ions can be also precipitated by adjusting the pH value of the waste liquid to the range of 7 to 10. The pH value of the waste liquid can be adjusted by adding potassium hydrate (KOH) or sodium hydrate (NaOH). The concentration of the potassium (KOH) or sodium hydrate (NaOH) is preferably more than 0.1M.
The precipitate formed in this step is MZ or
M(OH)2, in which M=Cu+2, Fe+2 or Fe+3 and Z=S 2, C204 2 -2 or C03-2.
(C). Removing Fluorine Ion from the Waste Liquid
Fluorine ions can be removed by adding the liquid containing aluminium ions so as to form precipitates of aluminium trifluoride (AlF3) or ammonium fluoaluminate [(NH4)2A1F6). The operational requirements are as follows: the rotation speed of the waste liquid is kept within the range of 30 to 300 rpm, the pH value is kept within the range of 1.0 to 8.0, and the temperature is kept between 150 and 650C. The purity of the obtained aluminium trifluoride (A1F3) is more than 99 so as to allow it to be used as material for aluminium smelting.
(D) Renlacinq the Tin Ions Contained in the Filtrate of the Above Step and Filtrating the Resultant Solution into a Filtrate and Tin Powder or Granules
Tin ions contained in the waste liquid can be replaced by adding aluminium. The added amount of aluminium is more than 0.2 to 2.0 times, by weight, of the tin contained in the filtrate. The pH value of the filtrate is adjusted to be less than 4.0 before the aluminium is added, and the rotation speed is kept within the range of 300 to 1,000 rpm. The temperature of the filtrate is kept within the range of 300 to 800C, and the reaction time between the aluminium and the tin ions is about one to four hours.During the procedure of this reaction, the pH value of the filtrate is kept less than 3.0 by continuously adding sulfuric acid (H2S04), nitric acid (HNO3), or hydrochloric acid (HC1).
A portion of the filtrate is recycled to step (c) so as to form precipitates of aluminium trifluoride (A1F3) or ammonium fluoaluminate [(NH4)2A1F6] and to remove fluorine ions contained in the filtrate of step (c).
Preferably, the filtrate of this step is treated by an ion exchange resin tower and a sludge process before being expelled to the surroundings. As a result, the tin concentration and sludge amount of the expelled solution meet the requirements of environmental protection. The sludge amount of the waste liquid is dramatically decreased after the treatment of the present steps (about 0.001 of the original amount), which is one characteristic of the present invention.
Preferably, the pH value of the filtrate is adjusted before being expelled to surroundings. The concentration of tin ions of the expelled filtrate is below 0.3 ppm.
The purity of the obtained tin powder or granules is more than 99.9%; thus, it is suitable for being the raw material of smelting tin.
(E) Refining the Obtained Tin Powder or Granules bv
Smelting Process
The obtained tin is washed with 0.1% to 3.0t acid solution before being subjected to the tin smelting process. The temperature of the furnace is about 2200 to 3200C, and the smelting time is about 10 to 30 minutes.
Additionally, the present invention is also suitable to the waste liquid containing recovered tin which is concerned with nitric acid or sulfonic acid processes except that step (c) is omitted and the added amount of aluminium of step (d) is changed to 0.2 to 5.0 times of the tin contained in the filtrate.
Moreover, the present invention is also suitable to the waste liquid containing recovered tin/lead, except that lead oxide should be filtrated out before carrying out step (a).
While the present invention has been explained in relation to its preferred embodiment, it is to be understood that various modification thereof will be apparent to those skilled in the art upon reading this specification. Therefore, it is to be understood that the invention disclosed herein is intended to cover all such modification as fall within the scope of the appended claims.
Claims (16)
1. A process for recovering tin from waste liquid containing recovered tin comprising the steps of:
(a) reducing an oxidizer in the waste liquid (1) by adding at least one reducer selected from the group including sodium sulfite (Na2SO3), sodium hydrogen sulfite (NaNS03), and formaldehyde, so as to reduce said oxidizer, an added amount of said reducer being greater than or equal to 1.0 equivalent which is required to reduce the oxidizer; said waste liquid having a pH value in a range of 1.0 to 8.0, a temperature in the range of room temperature ambient to 700C, a reaction time of at least 10 minutes; or (2) by heating said waste liquid to remove hydrogen peroxide contained therein by adjusting said pH value to be less than 3.0, keeping said temperature in a range of 450 to 800C;
(b) precipitating out metal ions other than those of tin from said waste liquid (1) by adding at least one precipitant selected from a group including sodium oxalate (Na2C204), sodium carbonate (Na2CO3), and sodium sulfide (Na2 S), an added amount of said precipitant being greater than or equal to 1.0 equivalent which is required to precipitate said metal ions, said pH value being within a range of 1.0 to 8.0, said temperature being within a range of 150 to 650C, a rotation speed of said waste liquid being within a range of 60 to 300 rpm; or (2) by adding potassium hydrate (KOH) or sodium hydrate (NaOH) to adjust said pH value within a range of 7.0 to 10, so as to precipitate said; and filtrating the resultant liquid into filtrate and precipitates;
(c) adding 0.5 to 5.0 times, by weight, of a liquid containing aluminium ions to form precipitates of aluminium trifluoride (A12F6) or ammonium fluoaluminate t(NH4)2AlF6] so as to remove fluorine ions, said rotation speed being within a range of 30 to 300 rpm, said pH value being within a range of 1.0 to 8.0, and said temperature being within a range of 150 and 650C;;
(d) replacing tin ions by adding aluminium, an added amount of said aluminium being more than 0.2 times, by weight, of said tin contained in said waste liquid, a pH value of said waste liquid being adjusted to less than 4.0 before said aluminium is added, a rotation speed being within a range of 300 and 1,000 rpm, a temperature of said waste liquid being within a range of 300 to 80 C, a reaction time between said aluminium and said tin contained in said waste liquid being about one to four hours; during said reaction, said pH value of said waste liquid being less than 3.0; said replaced tin being in the form of powder or granules; said resulted waste liquid being filtrated into a filtrate and tin powder or granules; a portion of said filtrate being recycled to step (c) so as to remove fluorine ions from said waste liquid;
(e) refining said obtained tin powder or granules by smelting, a smelting temperature being in a range of 2200 to 3200C, a reaction time being in the range of 10 to 30 minutes.
2. A process as claimed in claim 1, wherein said waste liquid of step (a) is kept standing or has a rotation speed in the range of 30 to 200 rpm after adding said reducer.
3. A process as claimed in claim 1, wherein said heating of step (a) further comprises the step of adding ferrite salt, such as ferric chloride (FeC13), ferrous chloride (FeC12), or ferrous sulfate (FeSO4) to accerelate a decomposition reaction of said hydrogen peroxide contained in said waste liquid.
4. A process as claimed in claim 1, wherein in step (b), a concentration of said potassium hydrate (KOH) or sodium hydrate (NaOH) is greater than 0.1M.
5. A process as claimed in claim 1, wherein in step (c), a purity of said aluminium trifluoride (A1F3) is greater than 99%.
6. A process as claimed in claim 1, wherein in step (d), said pH value is maintained less than 3.0 by adding sulfuric acid (H2S04), nitric acid (HNO3), or hydrochloric acid (HC1).
7. A process as claimed in claim 1, wherein in step (d), sulfuric acid (H2SO4), nitric acid (HN03) or hydrochloric acid (HC1) are continuously added to maintain said pH value less than 3.0.
8. A process as claimed in claim 1, wherein in step (d), a purity of said metal powder or granules is greater than 99.9%.
9. A process as claimed in claim 1, wherein in step (e), said tin powder or granules are washed with acid solution of 0.1% to 3.0% before smelting.
10. A process as claimed in claim 1, wherein in step (b), said precipitate is MZ or M(OH)2, M being Cu+2, Fe+2 or Fe+3 and Z being S 2, C20 or CO3 -2
11. A process as claimed in claims 1, wherein in step (d), said filtrate is expelled out when said recycled filtrate exceeds an amount which is required to remove said fluorine ions.
12. A process as claimed in claim 1 or 11, wherein said expelled filtrate is subjected to an ion exchange resin tower to adjust the pH value of the filtrate, so as to reduce the concentration of tin ions to be below 0.3 ppm.
13. A process as claimed in claims 1 or 11, wherein sodium sulfide (Na2 S) is added into said filtrate so as to precipitate tin ions before said filtrate is expelled so as to reduce the concentration of tin ions in said filtrate to be below 0.3 ppm.
14. A process as claimed in claim 1, wherein said process is also suitable for recovering tin from waste liquid containing tin concerned with nitric acid or sulfonic acid, but step (c) is omitted, and the added amount of aluminium at step (d) is changed to 0.2 to 5.0 times.
15. A process as claimed in claim 1, wherein said process is also suitable for recovering tin from waste liquid containing tin/lead, but lead oxide is filtrated out before step (a).
16. A process substantially as described herein with reference to the accompanying drawing.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9124378A GB2261443A (en) | 1991-11-15 | 1991-11-15 | Process for recovering tin from a waste liquid containing tin recovered from printed circuit boards |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9124378A GB2261443A (en) | 1991-11-15 | 1991-11-15 | Process for recovering tin from a waste liquid containing tin recovered from printed circuit boards |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB9124378D0 GB9124378D0 (en) | 1992-01-08 |
| GB2261443A true GB2261443A (en) | 1993-05-19 |
Family
ID=10704745
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9124378A Withdrawn GB2261443A (en) | 1991-11-15 | 1991-11-15 | Process for recovering tin from a waste liquid containing tin recovered from printed circuit boards |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2261443A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106435188A (en) * | 2016-08-30 | 2017-02-22 | 江苏省冶金设计院有限公司 | Treatment method and system for hot metallized pellets |
| CN110699558A (en) * | 2019-04-02 | 2020-01-17 | 柳州光华科技有限公司 | Method for extracting high-purity tin from industrial waste |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112280993B (en) * | 2020-10-30 | 2022-07-29 | 大冶市金欣环保科技有限公司 | Device and method for extracting tin from tin smelting alkaline residue by adopting water leaching and neutralization |
| CN112708781B (en) * | 2020-12-23 | 2022-11-25 | 长春黄金研究院有限公司 | Method for recovering metal Sn from waste circuit board by adopting efficient Sn-removing medicament |
| CN113620475A (en) * | 2021-09-02 | 2021-11-09 | 徐红艳 | Circuit board contains tin effluent treatment plant |
| CN114351145B (en) * | 2021-12-30 | 2023-02-03 | 华南理工大学 | Tin and copper stripping liquid additive for hanger and preparation method and application thereof |
-
1991
- 1991-11-15 GB GB9124378A patent/GB2261443A/en not_active Withdrawn
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106435188A (en) * | 2016-08-30 | 2017-02-22 | 江苏省冶金设计院有限公司 | Treatment method and system for hot metallized pellets |
| CN110699558A (en) * | 2019-04-02 | 2020-01-17 | 柳州光华科技有限公司 | Method for extracting high-purity tin from industrial waste |
Also Published As
| Publication number | Publication date |
|---|---|
| GB9124378D0 (en) | 1992-01-08 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |