Abstract:
An eco-friendly method is designed to recycle copper contained in the discarded printed circuit boards and the like. The method involves use of various acids, such as hydrochloric acid, sulphuric acid, oxalic acid, to bring about the ionization of the copper, thereby resulting in formation of copper-containing solutions. The copper is brought back in the form of copper oxide or copper powder by use of various reducing agents. All byproducts produced in the course of recycling the copper are useful for other industrial applications.

Description:
FIELD OF THE PRESENT INVENTION  
       [0001]     The present invention relates generally to a process for recycling copper from a substance containing the copper, and more particularly to the methods and the devices by which the copper is completely recycled from a discarded printed circuit board (PCB) and from a discarded fluid containing the copper.  
       BACKGROUND OF THE PRESENT INVENTION  
       [0002]     As a result of the rapid development of information technology in recent years, the use of the low-end computers as well as the hand sets is wide-spread. Such a wide-spread use of the computers and the hand sets brings about a substantial increase in demand for the printed circuit board. Accordingly, the discarded printed circuit boards pose an environmental problem. In light of the fact that the process for making PCB involves the use of a chemical etching solution, such as copper chloride or the like. As a result, the process for making PCB results in production of a discarded fluid containing an extremely high concentration of copper ions. Without being properly treated, the discard fluid poses a potential environmental hazard. In addition, the copper which is contained in the discarded fluid should be recycled as a matter of cost-effectiveness. It is therefore imperative that copper should be recycled from a discarded or rejected PCB for economic and environmental reasons. A number of electronic components are attached to the PCB by tin soldering. The tin can be easily recycled by use of a stripping fluid. However, the copper contained in the discarded or rejected PCB can not be easily recycled by use of a stripping fluid. There are two conventional methods, by which the copper contained in the discarded PCB is recycled. These two conventional methods are described hereinafter.  
         [0003]     The first conventional method involves the comminution of the discarded printed circuit boards. By virtue of the principle of specific gravity, the powder is divided into two groups, one of which contains a greater amount of copper. This method is rather primitive and ineffective at best.  
         [0004]     The second conventional method involves the burning of the glass fiber and the adhesive of the discarded printed circuit boards. The adhesive contains epoxy resin and bromide. As a result. the burning of the adhesive is bound to produce bromine hydride which is a pollutant. In addition, the burning of the glass fiber must be done at a temperature greater than 1000 degress in Celsius and is therefore not cost-effective.  
       SUMMARY OF THE PRESENT INVENTION  
       [0005]     The primary objective of the present invention is to provide an economically feasible method for recycling copper that is contained in the discarded printed circuit boards or the discarded fluid which is resulted from the electroplating process or the etching process of the PCB production. The method involves the saturation of copper ions, which are then reduced by use of sodium carbonate or sodium hydroxide.  
         [0006]     Another objective of the present invention is to provide a copper recycling method, which involves use of hydrochloric acid. The discarded printed circuit boards are showered with the hydrochloric acid to obtain a fluid containing copper. The copper-containing fluid is provided with sodium carbonate, thereby resulting in formation of sodium salt and copper carbonate. The sodium salt can be crystallized by heating for industrial application. The copper carbonate is converted by heating into copper oxide, which is sold to generate an additional income. This method is economical and free from a pollutant.  
         [0007]     Another objective of the present invention is to provide a method for recycling copper which is contained in the discarded printed circuit boards. The method involves the use of hydrochloric acid or sulphuric acid, by which the copper is ionized in a solution. The solution is then provided with sodium hydroxide to form sodium salt and copper hydroxide. The copper hydroxide is converted by heating into copper oxide, which can be used as an industrial material. Meanwhile, the sodium salt is crystallized by heating for industrial application.  
         [0008]     Another objective of the present invention is to provide a copper recycling process in which the discarded printed circuit boards are bathed in a solution containing oxalic acid (HOOCCOOH-½H 2 O). The copper contained in the discarded printed circuit boards is made into copper oxalate (CuC 2 O 4 -½H 2 O), which is precipitated and harvested. The copper oxalate is heated in presence of oxygen so as to be converted into copper oxide which is of a commercial value.  
         [0009]     A further objective of the present invention is to provide a process for recycling copper that is contained in the discarded printed circuit boards. The process involves the use of hydrochloric acid or sulphuric acid, in which the discarded printed circuit boards are bathed to produce a solution containing the copper ions. An aluminum material is then introduced into the solution to result in formation of copper powder. The aluminum-containing solution can be used as PAC in the water treatment. The aluminum is used in the process by virtue of the aluminum being greater in activity than the copper. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0010]      FIG. 1  shows a flow block diagram of a first preferred embodiment of the present invention.  
         [0011]      FIG. 2  shows a flow block diagram of a second preferred embodiment of the present invention.  
         [0012]      FIG. 3  shows a flow diagram of a third preferred embodiment of the present invention.  
         [0013]      FIG. 4  shows a flow block diagram of a fourth preferred embodiment of the present invention.  
         [0014]      FIG. 5  shows a flow block diagram of a fifth preferred embodiment of the present invention.  
         [0015]      FIG. 6  shows a schematic view of a device which is used in the preferred embodiments as shown in  FIG. 1  through  FIG. 5 .  
         [0016]      FIG. 7  shows a flow block diagram of a sixth preferred embodiment of the present invention.  
         [0017]      FIG. 8  shows a flow block diagram of a seventh preferred embodiment of the present invention.  
         [0018]      FIG. 9  shows a schematic view of a device which is used in the preferred embodiments as shown in  FIG. 7a nd  FIG. 8 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]     It must be noted here that the present invention deals with the recycling of the copper that is contained in a discarded printed circuit board (PCB). Accordingly, the electronic components of the PCB and the tin solder, by which the electronic components are attached to the PCB, are not the subject matters of the present invention.  
         [0020]     Referring to  FIG. 1 , a method embodied in the present invention is used to recycle copper from the discarded printed circuit boards. The method involves a first step in which a predetermined number of the discarded printed circuit boards are immersed in the hydrochloric acid (HCl) so as to cause copper contained in the discarded printed circuit boards to remain in the ionizing state, thereby resulting in formation of a copper chloride (CuCl 2 ) solution. The chemical reaction is expressed as follows: 
 
Cu+2HCl→CuCl 2 +H 2 ↑
 
         [0021]     Thereafter, the copper chloride (CuCl 2 ) solution is mixed with a predetermined amount of sodium carbonate (Na 2 CO 3 ), as illustrated by the following chemical reaction: 
 
CuCl 2 +Na 2 CO 3 →CuCO 3 ↓+2NaCl 
 
         [0022]     The copper carbonate (CuCO 3 ) is precipitated and harvested. The copper carbonate is converted by heating into copper oxide (CuO), as shown in the following chemical reaction.  
                         
 
         [0023]     The copper oxide is used as an industrial raw material. The sodium chloride (NaCl) is also used as an industrial raw material. However, the sodium chloride so formed must be first crystallized by heating prior to being used as the industrial raw material.  
         [0024]     The use of the hydrochloric acid is to effect the ionization of the copper that is contained in the discarded printed circuit boards. The copper ionization can be enhanced by use of hydrogen peroxide, aeration, or electrode. The reduction of the copper ions is brought about by use of sodium carbonate (Na 2 CO 3 ).  
         [0025]     It must be noted here that the hydrochloric acid may be replaced by an electroplating waste fluid, etching waste fluid, or copper chloride waste fluid, which is a waste product of the manufacturing process of PCB. These waste fluids contain copper, as well as ionizing acid capable of ionizing the copper. The copper ions are then reduced by sodium carbonate (Na2CO 3 ), thereby resulting in formation of copper carbonate (CuCO 3 ), which is then converted by heating into copper oxide (CuO).  
         [0026]     As shown in  FIG. 2 , a second method embodied in the present invention is intended to recycle copper from the discarded printed circuit boards. This second method comprises an initial step in which the discarded printed circuit boards are immersed in the hydrochloric acid (HCl) so as to form a copper chloride (CuCl 2 ) solution, as illustrated by the following chemical equation. 
 
Cu+2HCl→CuCl 2 +H2↑
 
         [0027]     The copper chloride solution is then mixed with sodium hydroxide (NaOH) to form copper hydroxide, Cu(OH) 2 , and sodium chloride (NaCl), as shown in the following reaction equation. 
 
CuCl 2 +2NaOH Cu(OH) 2 ↓+2NaCl 
 
         [0028]     The copper hydroxide is precipitated and harvested; it is then converted by heating into copper oxide as shown in the following chemical equation.  
                         
 
         [0029]     The sodium chloride is crystallized by heating before it is used as an industrial raw material. The copper oxide can be used directly as an industrial raw material. It must be noted here that the ionization of copper by the hydrochioric acid can be accelerated by use of hydrogen peroxide, aeration, or electrode.  
         [0030]     It must be noted here that the hydrochloric acid may be replaced by an electroplating waste fluid, etching waste fluid, or copper chloride waste fluid, which is a waste product of the manufacturing process of PCB. These waste fluids contain copper, as well as ionizing acid capable of ionizing the copper. The copper ions are then reduced by sodium hydroxide (NaOH), thereby resulting in formation of copper carbonate (CuCO 3 ), which is then converted by heating into copper oxide(CuO).  
         [0031]     Referring to  FIG. 3 , a third method embodied in the present invention is designed to recycle copper from the discarded printed circuit boards. In the first place, the discarded printed circuit boards are immersed in the sulphuric acid (H 2 SO 4 ), thereby resulting in formation of copper sulphate (CuSO 4 ) as shown in the following chemical equation. 
 
Cu+H 2 SO 4 =CuSO 4 +H 2 ↑
 
         [0032]     A reducing agent, sodium carbonate (Na 2 CO 3 ), is added to the copper sulphate solution, thereby resulting in formation of copper carbonate (CuCO 3 ) and sodium sulphate (Na 2 SO 4 ) as shown in the following chemical reaction. 
 
CuSO 4 +Na 2 CO 3 →CuCO 3 ↓+Na 2 SO 4  
 
         [0033]     The copper carbonate is precipitated and harvested; it is then converted by heating into copper oxide (CuO), which is used as an industrial raw material.  
                         
 
         [0034]     The ionization of copper by sulphuric acid can be enhanced by use of hydrogen peroxide, aeration, or electrode. The byproduct, such as sodium sulphate (Na 2 SO 4 ), is crystallized by heating prior to being used as an industrial raw material.  
         [0035]     It must be noted here that the hydrochloric acid may be replaced by an electroplating waste fluid, etching waste fluid, or copper chloride waste fluid, which is a waste product of the manufacturing process of PCB. These waste fluids contain copper, as well as ionizing acid capable of ionizing the copper. The copper ions are then reduced by sodium carbonate (Na 2 CO 3 ), thereby resulting in formation of copper carbonate (CuCO 3 ), which is then converted by heating into copper oxide (CuO).  
         [0036]     As shown in  FIG. 4 , a fourth method embodied in the present invention is used to recycle copper contained in the PCB. The method involves a first step in which the discarded printed circuit boards are immersed in the sulphuric acid (H 2 SO 4 ), thereby resulting in formation of copper sulphate (CuSO 4 ) as shown in the following chemical reaction. 
 
Cu+H 2 SO 4 →CuSO 4 +H 2 ↑
 
         [0037]     A reductant, sodium hydroxide (NaOH), is added to the copper sulphate (CuSO 4 ) solution to form copper hydroxide, Cu(OH) 2 , and sodium sulphate, Na 2 SO 4 , as shown in the following chemical equation. 
 
CuSO 4 +2NaOH→Cu(OH) 2 ↓+Na 2 SO 4  
 
         [0038]     The copper hydroxide, Cu(OH) 2 , is harvested and then converted by heating into copper oxide (CuO) as shown in the following chemical reaction.  
                         
 
         [0039]     The ionization of copper by sulphuric acid (H 2 SO 4 ) may be accelerated by use of hydrogen peroxide, aeration, or electrode. The copper oxide so formed can be used directly as an industrial raw material, while the sodium sulphate (Na 2 SO 4 ) is crystallized by heating prior to being useful as industrial raw material.  
         [0040]     It must be noted here that the hydrochloric acid may be replaced by an electroplating waste fluid, etching waste fluid, or copper chloride waste fluid, which is a waste product of the manufacturing process of PCB. These waste fluids contain copper, as well as ionizing acid capable of ionizing the copper. The copper ions are then reduced by sodium hydroxide (NaOH), thereby resulting in formation of copper carbonate (CuCO 3 ), which is then converted by heating into copper oxide (CuO).  
         [0041]     Referring to  FIG. 5 , a fifth method embodied in the present invention is designed to recycle copper from the discarded printed circuit boards. The method involves an initial step in which the discarded printed circuit boards are immersed in a solution of oxalic acid (HOOCCOOH-½H 2 O). As a result, a powdered copper oxalate (CuC 2 O 4 -½H 2 O) is formed, as shown in the following chemical equation. 
 
O 2 +2Cu+2(HOOCCOOH-2H 2 O)→2(CuC 2 O 4 -½H 2 O)↓+5H 2 O 
 
         [0042]     The precipitate of copper oxalate is converted by heating in presence of oxygen into copper oxide (CuO), as shown in the following chemical equating.  
                         
 
         [0043]     It must be noted here that the precipitate of copper oxalate (CuC 2 O 4 -½H 2 O) is obtained by filtration. The copper oxide so produced is directly used as an industrial raw material.  
         [0044]     As shown in  FIG. 6 , a device is designed for use in the methods of the present invention as described above with reference to FIGS.  1  through  FIG. 5 . The device comprises a reaction tank  10 , a precipitation bath  20 , a conversion oven  30 , and a heater  40 . The reaction tank  10  is provided in the wall with an acid exit  11 . The precipitation bath  20  is provided in the wall with an acid inlet  21 , an outlet  22 , and a discharge port  23  of sodium salt The acid inlet  21  is connected with the acid exit  11  of the reaction tank  10  by a connection pipe  24  which is provided with a valve  241 . The precipitation bath  20  is provided with an electric agitator M. The conversion oven  30  has a feeding port  31 , a discharging port  32 , a feeding controller  33 , a see-through window  34 , an isolation tank  35 , and a dust remover  36 . The feeding port  31  is located at the top of the conversion oven  30 . The discharging port  32  is located at the bottom of the conversion oven  30 . The feeding controller  33  is disposed under the feeding port  31  for controlling the feeding speed. The see-through window  34  is located in the wall of the conversion oven  30  to facilitate the visual observation of the process in progress. The isolation tank  35  is disposed on the discharging port  32  for preventing copper oxide (CuO) from being contaminated in the course of transfer of the copper oxide. The dust remover  36  comprises a dust collecting tube  361 , a water bath  362 , and a venture tube dust cleaner  363 . The dust collecting tube  361  is connected to the wall of the conversion oven  30 . The venture tube dust cleaner  363  is mounted on the tube wall of the dust collecting tube  361 . A water pipe  364  is connected with the venture tube dust cleaner  363  and the water bath  362 . The water pipe  364  is provided with a pump  365 . The venture tube dust cleaner  363  has a suction force, by means of which the steam and the powered copper oxide are drawn form the conversion oven  30  into the dust collecting tube  361 . Meanwhile, the water is pumped by the pump  365  into the venture tube dust cleaner  363  from the water bath  362 , so as to facilitate the collecting of the powered copper oxide and the steam in the water bath  362  in which the copper oxide precipitates. The heater  40  is disposed in the interior of the conversion oven  30  and is provided with a plurality of conveyers  41  which are used to extend the reaction and to turn over the conversion product. Each set of conveyers  41  is provided with a heating apparatus  42  by which the temperature of the interior of the conversion oven  30  is kept between 230 and 350. In addition, the conveyers  41  are provided therebetween with a crushing wheel  43  and a dust shield  44  which is located over the crushing wheel  43  to avert dispersion of dust.  
         [0045]     Now referring to  FIG. 1  and  FIG. 6 , the operation of the device of the present invention calls for an introduction of an appropriate amount of hydrochloric acid (HCl) into the reaction tank  10 . Subsequently, a predetermined number of the discarded printed circuit boards are immersed in the reaction tank  10  containing the hydrochloric acid (HCl). As a result, the copper of the discarded printed circuit boards is ionized to form a copper chloride solution, which is transferred via the valve  241  to the precipitation bath  20 . As soon as the precipitation bath  20  contains an appropriate amount of the copper chloride solution, the valve  241  is shut off. An appropriate amount of sodium carbonate (Na 2 CO 3 ) is added to the precipitation bath  20 . The mixture is stirred thoroughly by the electric agitator M. The reaction products, sodium chloride (NaCl) and copper carbonate (CuCO 3 ), are formed, with the sodium chloride (NaCl) being discharged via the discharging port  23  of the precipitation bath  20 . The sodium chloride is crystallized by heating and is then used as an industrial raw material. In the meantime, the copper carbonate (CuCO 3 ) is precipitated at the bottom of the precipitation bath  20  and is discharged via the outlet  22  of the precipitation bath  20  such that the copper carbonate is put through a washing-dehydrating equipment “P”, and that the copper carbonate is fed into the conversion oven  30  via the feeding port  31  of the conversion oven  30 . The copper carbonate is heated in the interior of the conversion oven  30  in such a manner that it moves from one conveyer  41  to another. The copper carbonate (CuCO 3 ) is thus converted by heating into copper oxide (CuO), which is discharged via the discharging port  32  and is used as an industrial raw material.  
         [0046]     As far as the embodiments described with reference to  FIG. 2  through  FIG. 5 , the device is operated in similar manners described above with reference to  FIG. 1  and  FIG. 6 .  
         [0047]     Referring to  FIG. 7 , a sixth method embodied in the present invention is intended to recycle copper from the discarded printed circuit boards. The method comprises a first step in which a predetermined number of the discarded printed circuit boards are immersed in a hydrochloric acid solution for ionizing the copper contained in the discarded printed circuit boards, thereby resulting in formation of a copper chloride (CuCl 2 ) solution as shown in the following chemical equation. 
 
Cu+2HCl→CuCl 2 +H 2 ↑
 
         [0048]     The copper chloride (CuCl 2 ) solution is mixed with an aluminum material to form the copper powder and a poly aluminium chloride, [Al 2 (OH) n Cl 6-n .XH 2 O]m, aqueous solution, as shown in the following chemical reaction. 
 
m[(n+x)H 2 O+3[CuCl 2 ]+2Al]→3 m C u +[Al 2 (OH) n Cl 6-n″ XH 2 O] m +½ nm H 2  
 
         [0049]     In the above chemical equation, n=1-5, m≦10. The aluminum material is dissolved in the copper chloride solution. The aluminum material is recycled from the discarded material containing aluminum, or from the aluminium chips, so as to reduce the cost. In light of aluminium molecule being greater in activity than copper molecule, the copper of the copper chloride (CuCl 2 ) is replaced by the aluminium, thereby resulting in production of copper powder. The aqueous solution of the poly aluminum chloride [Al 2 (OH) n Cl 6-n .XH 2 O] m  is used as a metal PAC in the water treatment.  
         [0050]     As shown in  FIG. 8 , a seventh method embodied in the present invention is used to recycle copper from the discarded printed circuit boards. The method involves an initial step in which the discarded printed circuit boards are immersed in a sulphuric acid solution (H 2 SO 4 ), thereby resulting in formation of a copper sulphate (CuSO 4 ) solution, as shown in the following chemical equation. 
 
Cu+H 2 SO 4 →CuSO 4 +H 2 ↑
 
         [0051]     The copper sulphate solution is then mixed with an aluminium material to form copper powder and an aluminium sulphate aqueous solution (Al 2 [SO 4 ] 3 ), as shown in the following chemical reaction. 
 
3[CuSO 4 ]+2Al→Al 2 [SO 4 ] 3 +3Cu 
 
         [0052]     The aluminium material is obtained from the discarded material containing aluminium, or from the aluminium chips, so as to reduce the cost. In light of the aluminium molecule being greater in activity than the copper molecule, the copper of the copper sulphate (CuSO 4 ) is replaced by the aluminium, thereby resulting in production of copper powder. The Al 2 [SO 4 ] 3  aqueous solution is used as a metal PAC in the water treatment.  
         [0053]     Referring to  FIG. 9 , a device is used to carry out the methods described above with reference to  FIG. 7  and  FIG. 8  The device comprises a reactor  50 , an acid reservoir  60 , a PAC reaction precipitation bath  70 , a water tower  80 , and a PAC washing and storing apparatus  90 . The reactor  50  and the acid reservoir  60  are connected by a pipe  51  which is provided with a valve  52 . The acid reservoir  60  is provided in the wall with a solution transporting pipe  61  which is in turn provided with a pump  62 . The pipe  61  has one end, which is extended into the PAC reaction precipitation bath  70 . Located at the top of PAC reaction precipitation bath  70  is a basket  71  for holding aluminium. Located at the bottom of the precipitation bath  70  is a copper powder exit  72 . The precipitation bath  70  is further provided in the wall with a reaction circulation pipe  73 , which is provided with a reaction circulation pump  74  and a reaction circulation valve  75 . The reaction circulation pipe  73  has one end which is located at the top of the basket  71 . A PAC drain pipe  76  is disposed on the reaction circulation pipe  73  located between the reaction circulation pump  74  and the reaction circulation valve  75 . The PAC drain pipe  76  is provided with a PAC output valve  77 . The end of the drain pipe  76  is extended into the PAC washing and storing apparatus  90 . The water tower  80  is provided in the wall with a water pipe  81  which is provided with a reaction water admission valve  82  and has one end being extended into the reaction precipitation bath  70 . The PAC washing and storing apparatus  90  has a washing and filtering tank  91  and a PAC storage tank  92 . The washing and filtering tank  91  is provided at the top with a filter  93  and is provided in the wall with a PAC output pipe  94  which is provided with a pump  95 . The top of the washing and filtering tank  91  is connected with a PAC filtration pipe  96  a PAC storage pipe  97  and a return pipe  98 . The PAC filtration pipe  96 , the PAC storage pipe  97 , and the return pipe  98  are all connected with the PAC output pipe  94  and are provided with a valve “V”. The filter  93  and the water tower  80  are connected by a washing pipe  931  which is provided with a valve  932 .  
         [0054]     Now referring to  FIG. 7  through  FIG. 9 , the operation is carried out by providing the reactor  50  with an appropriate amount of hydrochloric acid (HCl) or sulphuric acid (H 2 SO 4 ). Thereafter, a predetermined number of the discarded printed circuit boards are immersed in the reactor  50  for the purpose of effecting the ionization of copper contained in the discarded printed circuit boards, so as to form a solution containing copper. The valve  52  is then opened to allow the copper-containing solution to flow into the acid reservoir  60 . As soon as the acid reservoir  60  contains an appropriate amount of the copper-containing solution, the valve  52  is shut off. An appropriate amount of an aluminium material is held in the basket  71 . Meanwhile, the reaction water admission valve  82  is opened to allow a small amount of clean water to enter the reaction precipitation bath  70 . The pump  62  is then started to pump the copper-containing solution into the PAC reaction precipitation bath  70  from the acid reservoir  60 . The reaction circulation pump  74  is simultaneously started while the reaction circulation valve  75  is opened. As a result, the aluminium material held in the basket  71  is thoroughly bathed in the copper-containing solution until such time when the PAC reaction precipitation bath  70  is filled with the copper-containing solution. The copper of the copper-containing solution is replaced by aluminium. The aluminium product is precipitated at the bottom of the PAC reaction precipitation bath  70  and is then discharged via the copper powder exit  72 . The PAC solution produced in the reaction is allowed to enter the washing and filtering tank  91  via the PAC output valve  77  and the drain pipe  76 . The valve “V” of the PAC filtration pipe  96  is opened to allow the passage of the PAC solution through the filter  93 . The valve “V” of the PAC storage pipe  97  is then opened to allow the clean PAC solution to enter the PAC storage tank  92 . Upon completion of the filtration of the PAC solution, the valve  932  of the washing pipe  931  is opened to allow the water in the water tower  80  to wash the filter  93  via the washing pipe  931 . The waste water contains PAC and is sent back to the PAC reaction precipitation bath  70  via the return pipe  98 .  
         [0055]     The copper-recycling methods of the present invention produce no by-product hazardous to environment. The present invention described above is to be regarded in all respects as being illustrative and nonrestrictive. Accordingly, the present invention may be embodied in other specific forms without deviation from the spirit thereof. The present invention is therefore to be limited only by the scopes of the following claims.