Recycle process for a metal bearing sludge concentrate

Abstract

A recycling treatment of heavy metal sludge uses a cracking process which releases macromolecular agglutinant and a metal hydrate mixture. Next the mixture is acidified in a primary homogenization process and then a primary separation process separates the macromolecular agglutinant and acid solution with metal ions. A second homogenization process adjusts the pH value of the acid solution with metal ions to be alkaline and then a second separation process separates copper oxide and the remaining salt solution with oxidant. Lastly, salt compounds and oxidant solution is separated through the use of a crystal separation process.

Description

[0001] The recycling treatment of heavy metal sludge includes: the cracking process, the primary homogenization process, the primary separation process, the secondary homogenization process, the secondary separation process and the crystal separation process. The cracking process is used to mix the sludge with acid solution and peroxide proportional to the sludge in weight. The mixture is then treated under high temperature and normal pressure. Macromolecular agglutinant and metal ion mixture will be released after a certain period of reaction. Next, the resulting mixtures go through the processes of primary homogenization and primary separation to separate macromolecular agglutinant which can then be used in sewage treatment system. Further, the secondary homogenization process and the secondary separation process will separate metal oxide while the process of crystal separation will filter out neutralization material that can be applied in soil or other exhausted liquid along with an oxidant that can be used for water treatment. The metal oxides and macromolecular agglutinant are thus recycled and reused while other end products are used in this treatment system or the sewage treatment system to avoid causing further environmental pollution. Also, production cost is lowered and resources are recycled.

FIELD OF INVENTION

[0002] The invention involves the recycling treatment of sludge containing heavy metal, in particular a treatment that can recycle and reuse the heavy metal sludge and the exhausted liquid of etching solution generated in the process of producing printed circuit boards. The solid metal oxide, liquid treating compound and agglutinant produced in the treatment can be recycled and used in the process, the sewage treatment system or other uses. This treatment is a method that treats and recycles heavy metal sludge without causing further pollution.

BACKGROUND

[0003] Circuit board manufacturing has played an important role in the strategic industry in Taiwan. It is considered an essential industry that will allow Taiwan to become an island of technology. However, the sludge and the etching solution of different concentrations generated in the process are classified as hazardous waste. Hence, despite the high growth and high profitability, the industry has long been troubled with the problem of causing environmental pollution. According to domestic statistics, the circuit board manufacturing industry produces more than 200,000 tons of hazardous sludge every year. This number increases 20% every year. What is more, the organic or inorganic chemicals used by various production units in the printed circuit board manufacturing process also generate exhausted liquid of high concentration, including the exhausted liquid of developer, the exhausted liquid of stripping, the exhausted liquid of etching solution and the exhausted liquid of stannum and lead stripping. Thus, the industry has long tried to effectively resolve the problems of heavy metal sludge and exhaust gas.

[0004] In Taiwan and in other countries, many methods have been developed to handle heavy metal sludge, which includes burial, calcinations, solidification, fusion, acid maceration and ammonia leach. For all relevant technology, please refer to Patent No. GE844722 of UK, Patent Nos. 3,300,299, 4,428,773, 4,242,127, 4,162,294, 5,599,458, 5,807,478 and 5,234,669 of USA as well as U.S. Pat. Nos. 81,106,585, 82,103,460, 89,123,260, 89,112,071, 89,116,503 of the Republic of China. Nevertheless, none of these methods can avoid the problem of causing further environmental pollution, i.e. none of these methods can completely eliminate hazardous exhaust gases, wastewater and waste created during or after the treatment. Instead, these treatments can simply reduce the amount of hazardous materials to an acceptable degree. The hazardous materials are then disposed of by a professional cleaning institution according to relevant laws and regulations. Possible risks of such treatments include water or land pollution when hazardous materials are disposed or buried at discretion or were not transported to the designated disposal area. Besides, such methods also waste a lot of resources. So far, current heavy metal sludge treatments cannot solve such problems.

[0005] In addition to the problem of environmental pollution, the high cost of treatment is also a heavy burden to the industry. At present, the only method recognized by the government is solidification whose treatment cost reaches 10-12 NT$/kg (excluding the cost of cleaning and burial). For a company that might have to dispose of several tones of sludge every day, the cost of treatment is nearly unbearable. Thus, such method of treatment is not cost efficient, nor does it fit in the goal of enterprises to reuse resources for sustainable development.

[0006] [Goal]

[0007] The goal of this invention is to provide a method to treat and to recycle heavy metal sludge. The process of such treatment can establish a complete lifespan cycle of waste to recycle and reuse treatment products in different units or to use them in sewage treatment systems or recycle system so as to avoid causing further environmental pollution.

[0008] Another objective of this invention is to lower the production cost, to increase the production efficiency and to reduce the amount of waste for enterprises' goal of sustainable development.

[0009] [Description]

[0010] The major feature of this heavy metal sludge treatment is the inclusion of the cracking process, in which sludge is mixed with acid solutions such as sulphuric acid, nitric acid and hydrochloric acid as well as peroxides such as hydrogen peroxide, dibutyl peroxide, bicumyl peroxide, (tertbutyl peroxide) hexene and (tertbutyl peroxide) hexane in an amount proportional to the amount of sludge. The mixture is stirred and treated under high temperature and normal pressure. After four hours of reaction, the heavy metal in the mixture is released while macromolecular agglutinant in the sludge mixture is broken by peroxide and release heavy metal hydrate, which then reacts with acid solution to release metal ions.

[0011] Based on the above-mentioned feature, the weight ratio of peroxide to sludge is 0.5-2 to 40-50.

[0012] Another feature of this invention is the inclusion of the primary homogenization process and the primary separation process which can use an acid solution to treat the mixture after the cracking process to change the pH value of the mixture to be between 2 and 7 and separate macromolecular agglutinant that contains 70% water as well as an acid solution with heavy metal ions. The macromolecular agglutinant can then be recycled and used in a sewage treatment system.

[0013] The next feature of the invention is to further include the processes of secondary homogenization and secondary separation, which add ammonia, and Alkaline Earth Metal into the acid solution with heavy metal ions generated in the primary separation process so as to change the pH value of the solution to be between 7 and 11. The crystalline deposit process then separates metal oxides and salt solutions containing oxidant. Metal oxides can be used as the raw material for chemical processing or otherwise recycled.

[0014] The invention further includes the process of crystal separation to freeze and crystallize the salt solution that contains oxidant after the secondary separation process and to separate salt compounds. The salt compounds can be recycled and reused in soil treatment or other industries while the remaining oxidant solution can be used directly in the cracking process or used as an oxidant in water treatment after the solution reaches a certain concentration.

[0015] The last feature of this invention is to include the digesting process to direct the exhausted liquid into the cracking process or to use normal acid to mix with the mixture of sludge.

[0016] The digesting process can further mix the hydrate treated in the primary separation process with the sludge mixture in the primary homogenization process and/or the secondary homogenization process.

DESCRIPTION OF FIGURES

[0017] FIG. 1 is the flowchart of the first example of the heavy metal sludge recycling treatment.

[0018] FIG. 2 is the flowchart of the second example of the heavy metal sludge recycling treatment.

[0019] FIG. 3 is the flowchart of the third example of the heavy metal sludge recycling treatment.

DESCRIPTION OF EXAMPLES

[0020] Please refer to FIG. 1 for the heavy metal sludge recycling treatment which includes the cracking process (2), the primary homogenization process (3), the primary separation process (4), th secondary homogenization process (5), the secondary separation process (6), the crystal separation process (7) and the digesting process (8). The flow diagram is illustrated below:

[0021] In the cracking process (2), the tank containing the treating compound (20) is used to store peroxide. In this example, dibutyl peroxide (or any peroxide sold in the market such as hydrogen peroxide, bicumyl peroxide, (tertbutyl peroxide) hexane, or (tertbutyl peroxide) hexane are used. The sulphuric acid solution tank (21) is used to store sulphuric acid solution while the reaction tank (22) has a beater to mix the sludge and the above-mentioned solution. In this process, 40 kg of dibutyl peroxide (or any other peroxide) and 200 kg of sulphuric acid solution are put in the reaction tank (22), then 1000 kg of sludge with 10% of copper (9) is put into the reaction tank (22). The mixture of 1240 kg is then stirred while the temperature is increased to 220° C. After four hours of reaction under normal pressure, the metal in the sludge that can't be solved by the sulphuric acid solution is then released and the macromolecular agglutinant in the sludge mixture is destroyed by organic peroxide to release m tal hydrate in the sludge. The weight ratio of peroxide and sludge is 0.5-2 to 40-50. After treatment, the mixture goes through the primary homogenization process (3).

[0022] In the process of primary homogenization (3), a digestion tank (30) is used to store an acid solution, such as sulphuric acid. It is noteworthy that the digesting process (8) of this invention uses a digesting liquid tank (80) to store the exhausted liquid of micro etching for recycling. The tank also stores the acid solution (or hydrate) containing copper ions after the primary separation process (4) to be described later so as to be directly used in the digestion tank (30) or to be stored in the sulphuric acid solution tank (21). To better enhance the treatment of filter press in the primary separation process (4), the pH value of the 1240 kg of sludge mixture treated in the cracking process (2) is adjusted to be between 2 and 7. In this example, 600 kg of acid solution is used to mix with the sludge mixture and the pH value is adjusted to 5. 950 kg of macromolecular agglutinant containing 70% water and 600 kg of acid solution with copper ions are filtered out. Among which, the macromolecular agglutinant can be recycled and used in sewage treatment systems.

[0023] In the secondary homogenization process (5), a precipitator tank (50) and a precipitation tank (51) are used. The precipitator tank (50) can store alkaline solution such as lime, sodium hydroxide, ammonia for use in the precipitation tank (51). In this example, 50 kg of lime is added in the 600 kg of acid solution with copper ions filtered during the primary separation process (4) to create a 650 kg of mixture. The pH value of the mixture is adjusted to be between 7 and 9 after the filter press treatment in the secondary separation process (6) to precipitate 250 kg of 50% copper oxide and 400 kg of remaining alkaline solution. Copper oxide can then be used as raw material in the chemical industry or copper industry.

[0024] Finally, after the crystal separation process (7), the tank that stores alkaline solution with a sulfate radical (70), the crystallizer tank (71) and centrifugal filter (72) filter out sulphate and peroxide solution from the remaining digesting liquid after the secondary separation treatment. Filtered sulphate can be recycled and used as raw material for industrial usage or civil usage while the remaining peroxide solution can be led into the treating compound tank (20) for the cracking process (2) after the pH value is adjusted to be neutral. It can also be used as an oxidant for water treatment.

[0025] From the flowchart, we can see that during each part of the treatment process of the sludge with copper, all products were either reused in the process or led into a sewage treatment system or recycled back into the system for further use. Hence, the problem of causing further pollution is resolved.

[0026] FIGS. 2 and 3 are the second and third example of this invention. The second example includes the cracking process (2′), the primary homogenization process (3′), the primary separation process (4′), the secondary homogenization process (5′), the secondary separation process (6′) and the crystal separation process (7′) as well as the digesting process. However, the digesting process (8′) is different from example one while the other processes are exactly the same. In example two, the digesting process is divid d into two. One tank of micro etching exhausted liquid (81′) is used to store micro etching exhausted liquid with copper (hereinafter as micro etching bath) from a factory of printed circuit board and a tank of digesting liquid (82′) for the acid solution with copper ions after the treatment of primary separation (4′). Example three also includes the cracking process (2″), the primary homogenization process (3″), the primary separation process (4″), the secondary homogenization process (5″), the secondary separation process (6″), the crystal separation process (7″) and the digesting process. The only difference is that the digesting process is divided into three parts with th micro etching exhausted liquid tank (81″) and th digesting liquid tank (82″) in example two and a tank containing etching exhausted liquid (83″). All the other processes are exactly the same as example one.

[0027] In addition, example four used hydrogen peroxide as the peroxide while the other processes are the same as examples one, two, and three. Example five used hydrochloric acid for the acid solution and example six used limes as the precipitator, all the other processes are the same.

[0028] For example seven, eight and nine, all the processes are the same except that example seven used a dibutyl peroxide with the ratio of 1-5 to 5-1, example eight used tertbutyl peroxide ethene for its peroxide, and example nine used nitric acid as the acid digesting liquid and ammonia as the precipitator.

[0029] As for the products of all the examples, the analysis of copper oxide is shown in Table 1 and the results of function testing of macromolecular agglutinant and oxidant are shown in Table 2. 1 TABLE 1 Example Cu (%) Fe (ppm) Sn (ppm) Ni (ppm) Zn (ppm) Pb (ppm) Salt 1 36.73 903.15 2837.6 683.4 481.2 103.4 sodium sulphate 2 37.24 914.22 2854.2 672.6 489.5 107.2 sodium sulphate 3 28.01 898.63 2812.9 693.5 498.3 115.8 ammiaonia sulfate 4 42.33 951.78 2962.1 722.2 535.6 137.2 calcium chloride 5 43.57 966.69 2945.8 737.8 547.2 142.6 calcium chloride calcium sulphate 6 43.46 942.59 2973.9 713.9 551.5 132.6 ammonium chloride 7 41.39 875.34 2621.7 654.3 461.7 87.7 ammonium nitrate 8 40.99 879.12 2654.8 662.4 453.4 91.4 ammonium nitrate ammiaonia sulfate 9 41.83 869.37 2663.2 649.1 442.2 80.6 ammonium nitrate

[0030] 2 TABLE 2 Macromolecular Example agglutinant (Note 1) % Oxidant (Note 3) % 1 4.7 (25) (Note 2) 6.7 2 4.2 (27) 7.0 3 5.0 (22) 6.9 4 — 4.2 5 — 4.6 6 — 4.5 7 3.2 (31) 5.3 8 3.5 (33) 5.9 9 3.1 (30) 6.4 Note 1: the required permillage needed to remove the amount of metal ions to reach the standards of waste water effluent for printed circuit board manufacturing industry. Note 2: the content of macromolecular agglutinant. Note 3: the required permillage needed to ensure that the sewage of COD 200 to 500 ppm reaches the standards of waste water effluent for printed circuit board manufacturing industry

[0031] In sum, this invention of heavy metal sludge recycling treatment is not only creative and innovative, but also fits the need of the industry. Please note the above-mentioned examples are just some of the best examples and the scope of patent of this invention should not be limited to these examples. Any change or modification made based on this invention should be within the scope of patent of this invention. 3 [Reference list of component symbols] the cracking process 2, 2′, 2″ the primary 3, 3′, homogenization process 3″ the primary separation 4, 4′, process 4″ the secondary 5, 5′, homogenization process 5″ the secondary separation 6, 6′, process 6″ the crystal separation 7, 7′, process 7″ the digesting process 8 the tank of treating 20 the tank of 21 compound sulphuric acid solution the reaction tank 22 the digestion 30 tank the precipitator tank 50 the precipitation 51 tank the liquid tank 70 the crystallizer 71 tank the centrifugal filter 72 the tank of micro 81′, etching exhausted 81″ liquid the tank of digesting 82′, liquid 82″ tank of etching 83′, exhausted liquid 83″

Claims

1. A recycling treatment of heavy metal sludge which includes:

The cracking process, in which the sludge is mixed with a sulphuric acid solution and peroxide proportional to the sludge in weight and treated under high temperature and normal pressure,

After a certain period of reaction, macromolecular agglutinant and a metal hydrate mixture are released;

The primary homogenization process, which adjusts the pH value of the mixture after the cracking process to be acidic;

The primary separation process, which mixes the acid mixture from the primary homogenization process to separate macromolecular agglutinant and acid solution with metal ions;

The second homogenization process, which adjusts the pH value of the acid solution with metal ions to be alkaline;

The second separation process, which separates copper oxide and the remaining salt solution with oxidant after second homogenization; and

The crystal separation process, which treats the remaining acid exhausted liquid after second separation to filter out salt compounds and oxidant solution.

2. For the cracking process mentioned in claim 1 of the heavy metal sludge recycling treatment, the weight ratio of peroxide and sludge is 0.5-2 to 40-50.

3. The peroxide used in the cracking process mentioned in claim 1 of the heavy metal sludge recycling treatment can be hydrogen peroxide, dibutyl peroxide, dicumyl peroxide, (tertbutyl peroxide) hexene, (tertbutyl peroxide) hexane.

4. The primary homogenization process mentioned in claim 1 uses one or more acid solution including sulphuric acid, hydrochloric acid, nitric acid and micro etching exhausted liquid to change the pH value.

5. The secondary homogenization process mentioned in claim 1 uses one or more alkaline solution including sodium hydroxide, lime, ammonia and etching exhausted liquid to change the pH value.

6. The temperature used in the cracking process mentioned in claim 1 is between 200° C. and 250° C.

7. The time needed for the process of cracking mentioned in claim 1 is three to six hours.

8. The best pH value for primary homogenization process mentioned in claim 1 should be 2 to 7.

9. The best pH value for secondary homogenization process mentioned in claim 1 should be 7 to 10.

10. The products of the crystal separation process mentioned in claim 1 include: sodium sulphate, ammiaonia sulfate, sodium chloride, sodium chloride, sodium nitrate, ammonium nitrate, calcium sulphate and calcium chloride.

11. The digesting process mentioned in claim 1 is used to mix either the existing micro etching exhausted liquid from a printed circuit board factory or any normal acid with the sludge mixture in the process of cracking.

12. The digesting process mentioned in claim 1 can further use the hydrate treated in primary separation or the hydrate can be used in the primary homogenization and/or secondary homogenization to be mixed with the sludge mixture.

13. The copper oxide produced in the process as described in claim 1 contains a copper content of 30-50% of its weight.

14. For the macromolecular agglutinant mentioned in claim 1 in the patent application, the content of macromolecule is 20-40% in weight.

15. For the oxidant solution mentioned in claim 1 in the patent application, the oxidizing ability can reach the standard of sewage discharge of COD 200 to 500 ppm after adding 3.0-9.0 permillage in weight.