Abstract:
In a method of recovering copper from an industrial waste sludge or liquid, a first treatment agent and/or a second treatment agent is added into a waste feed to separate the coagulants therefrom. A bluish solution and a tail gas are thereby obtained. Alternatively, an acidic etching waste solution is added instead of the first treatment agent and/or the second treatment agent into the waste feed. Then, a converting agent/converting aid agent is added in the bluish solution. Thereafter, the solution is filtrated to obtain a solid copper oxide, a filtrate and a tail oxidizing gas. The filtrate is saturated by the aforementioned gases and fed back to the waste feed. The copper oxide thereby obtained has a high copper content compared to the conventional methods. All of the other resulting products are recycled without being disposed of in the environment.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
         [0001]    This application claims the priority benefits of the Taiwan patent application No. 91101113 filed on Jan. 24, 2002, and the Taiwan patent application No. 91123527, filed on Oct. 11, 2002.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to a method of recovering copper. More specifically, the present invention relates to a method of recovering copper from an industrial sludge containing copper substances and coagulants.  
           [0004]    2. Description of the Related Art  
           [0005]    An electronic product is usually manufactured through many processing steps that produce a lot of waste liquid containing valuable copper ions and harmful ions. To prevent an environmental pollution, the industrial waste liquid produced from the electronic manufacturing plant such as a printed circuit board (PCB) plant should be treated before being disposed. The treatment of the waste liquid includes adjusting the waste liquid in a proper pH value range, properly balancing the charges of charged substances, and removing harmful metallic ions from the waste liquid. The charged substances are usually balanced by adding a coagulant to aggregate fine particles in the waste liquid. The harmful metallic ions are removed in a form of metal salts.  
           [0006]    Many waste treating methods have been proposed in the art. The current waste treating methods recover valuable substances such as copper from the waste liquid, while finally generating a sludge that is usually landfilled. The environmental pollution due to waste disposing therefore has not been completely solved.  
         SUMMARY OF THE INVENTION  
         [0007]    It is an object of the invention to provide a method of recovering copper from an copper-containing industrial sludge, in which in addition to a highly effective recovery of copper, all of the products generated during treating the waste sludge or liquid can be recovered and sold as commercial products. Therefore, no products are disposed or landfilled.  
           [0008]    In order to achieve the above and other objectives, a method of recovering copper from an industrial sludge that contains copper substances and coagulants is proposed. Either a first treatment agent and/or a second treatment agent or an acidic etching waste solution is added in a waste feed to separate the coagulants from the industrial sludge and obtain a bluish solution and a first tail gas. Then, a converting agent/converting aid agent is added in the bluish solution. Thereafter, the solution is filtrated to obtain a solid copper oxide, a filtrate and a second tail gas. The filtrate is saturated with the first and second tail gases and fed back to the sludge feed. The obtained copper oxide has a high copper content compared to the conventional methods. All of the resulting other products are recycled and therefore nothing is disposed of in the environment.  
           [0009]    It is to be understood that both forgoing general description and the following detailed description are exemplary, and intended to provide further explanation of the invention as claimed. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawing illustrate embodiments of the invention and, together with the description, serve to explain the principles if the invention. In the drawings,  
         [0011]    [0011]FIG. 1 is a flow chart of a method of recovering copper according to one preferred embodiment of the invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0012]    The following detailed description of the invention with reference to the accompanying drawings is only illustrative of specific structures and ways of making the invention, and does not limit the scope of the invention. Wherever possible in the description, like reference numerals will refer to like elements and parts unless otherwise illustrated.  
         [0013]    A waste to be treated by the method of the invention may be either a copper-containing waste liquid without coagulant, or an industrial waste sludge that is produced after a coagulant has been added in an industrial waste liquid. An example of the coagulant includes Al 2 (SO 4 ) 2 .18H 2 O, Fe 2 (SO 4 ) 3 , FeSO 4 .7H 2 O, FeCl 3 .6H 2 O, Al 2 (SO 4 ) 3 (NH 4 ) 2 SO 4 .24H 2 O, Al 2 (SO 4 ) 3 , K 2 SO 4 .24H 2 O, Ca(OH) 2 , CaO, Na 2 CO 3 .10H 2 O, Na 2 OAl 2 O 3 , MgO, Na 2 CO 3 , NaHCO 3 , NaOH, active silicic acid and polymeric electrolytes.  
         [0014]    [0014]FIG. 1 is a flow chart of a method of recovering copper according to one preferred embodiment of the invention. In the case that an industrial waste sludge  100  is to be treated, a first treatment agent  200  and/or a second treatment agent  200 ′ and the industrial waste sludge  100  are added in a stirring tank A to obtain a solution and a tail gas  11 . In other preferred embodiments of the present invention, the first treatment agent  200  and/or the second treatment agent  200  can be replaced with an acidic etching waste solution. After either the first treatment agent  200  and/or the second treatment agent  200 ′ or the acidic etching waste solution has been added and stirred, a suspension including a solid phase and an aqueous phase is formed as well as a tail gas  11 . In a solid/liquid separation process, the suspension first is separated into a clear liquid  1  and a residue  2 . The clear liquid  1  is a clear bluish liquid that contains copper ions. The residue  2  is further filtered through a filtering device B to separate into a yellowish brown solid and a solution. The filtering device B can be any conventional solid/liquid separation device, such as a suction filter, a press filter and a centrifugation device. The yellowish brown solid is the coagulant  3  contained in the waste sludge. The solution obtained after the residue  2  has been filtered is a copper-containing aqueous solution  4 .  
         [0015]    The first treatment agent  200  is used to change the bonding structure of the coagulant  3  in the waste sludge to allow the coagulant  3  to be easily recovered from the waste sludge, and further allow the copper ions to be easily released. The first treatment agent  200  can be, but not limited to, a sulfuric acid, a nitric acid, a hydrogen chloride, an oxidant and the like. The oxidant used as the first treatment agent  200  can be any kind of oxidants, as long as oxygen free radicals can be generated after the oxidant has been added in the copper-containing waste sludge  100 . The oxidant can be, but not limited to, potassium permanganate, sodium permanganate, potassium manganate, sodium manganate, sodium sulfite, potassium sulfite, potassium chlorate, sodium chlorate and the like.  
         [0016]    The second treatment agent  200 ′ serves to help the copper ions escape from the industrial waste sludge  100  while preventing the coagulant  3  from being excessively destroyed. The second treatment agent  200 ′ can be, but not limited to, a sulfuric acid, a nitric acid, a hydrogen chloride, an oxidant and the like. The second treatment agent  200 ′ can be the same as or different from the first treatment agent  200 . The oxidant used as the second treatment agent  200 ′ can be any kind of adequate oxidants that allow the generation of oxygen free radicals after the oxidant has been added in the copper-containing waste sludge  100 . The oxidant can be, but not limited to, potassium permanganate, sodium permanganate, potassium manganate, sodium manganate, sodium sulfite, potassium sulfite, potassium chlorate, sodium chlorate and the like.  
         [0017]    The first treatment agent  200  and the second treatment agent  200 ′ can be used alone or in combination. In the case that both first treatment agent  200  and second treatment agent  200 ′ are used, the sequence of adding the first treatment agent  200  and the second treatment agent  200 ′ is determined according to treatment conditions such as a concentration and a content of the waste to be treated. Typically, the first treatment agent  200  therefore can be added before, after, or at the same time as the addition of the second treatment agent  200 ′. The first treatment agent  200  and/or the second treatment agent  200 ′ can be charged in batches or continuously. The first treatment agent  200  and/or the second treatment agent  200 ′ are added in an amount to turn the industrial waste sludge  100  into the suspension and the tail gas  11  after the first treatment agent  200  and/or the second treatment agent  200 ′ are added and stirred. Preferably, the total amount of the first treatment agent  200  and/or the second treatment agent  200 ′ is in a range of 20-800 wt. % based on the total weight of the copper-containing waste sludge  100 .  
         [0018]    The acidic etching waste solution can be originated from, for example, a PCB manufacture plant. The acidic etching waste solution can be, but not limited to, copper sulfate, copper borate, copper borofluoride, copper pyrophsphate, copper nitrate, copper chloride and any etching waste solution. The acidic etching waste solution is added in an amount to turn the industrial waste sludge  100  into a suspension after the acidic etching waste solution is added and stirred. Preferably, the amount of the acidic etching waste solution is in a range of 50-1000 parts by weight based on the total weight of the copper-containing waste sludge  100 .  
         [0019]    The tail gas  11  has an oxidizing ability due to the presence of oxygen free radicals contained therein. The oxygen free radicals can be OH., SOx., ClOx. and the like, and a combination thereof, for example. The tail gas  11  can be recovered as oxidants for commercial sale or for use in subsequent processing steps.  
         [0020]    The copper-containing aqueous solution  4  mainly includes compounds containing Cu 2+ , and Fe 3+  or Fe 2+ . An example of the compounds containing Cu 2+ , and Fe 3+  or Fe 2+  includes copper sulfate, copper nitrate, copper chloride, ferric sulfate, ferric nitrate, ferric chloride, ferrous sulfate, ferrous nitrate and ferrous chloride, and the like, and a combination of more than two thereof.  
         [0021]    The clear liquid  1  is mixed with the copper-containing aqueous solution  4  in a copper solution tank C to obtain a mixture  5  that is then transferred to a crystallization tank D. Thereafter, a converting agent  400  and a converting aid agent  400 ′ are added in the copper-containing aqueous solution  4  to directly convert the copper ions into copper oxide. This is one of the main features of the invention that the copper ions are directly converted into copper oxides without intermediate forms of copper hydroxide. The conversion reaction is as follows:  
                         
 
         [0022]    The converting agent  400  consists of basic salts and water. The basic salts include, for example, potassium hydroxide, sodium hydroxide, calcium hydroxide and the like. The converting aid agent  400 ′ consists of metal oxides and water. The metal oxides include, for example, calcium carbonate, sodium carbonate, potassium carbonate and the like, and a mixture of more than two thereof. However, the converting agent  400  and the converting aid agent  400 ′ are not limited to the above compounds, as long as the copper ions can be directly converted into copper oxides without intermediate forms of copper hydroxide. The amount of the converting agent  400  and the converting aid agent  400 ′ are not particularly limited, t as long as the copper ions can be directly converted into copper oxides without intermediate forms of copper hydroxide.  
         [0023]    The conversion reaction also generates a tail gas  7  which has an oxidizing ability due to its free radicals, especially oxygen free radicals. The oxygen free radicals include, for example, OH., SOx., ClOx. and the like, and a combination thereof. The tail gas  7  is charged to a tail gas recovery equipment G where the tail gas  11  may be previously charged.  
         [0024]    In case that an industrial waste liquid  300  without the coagulant is treated, the industrial waste liquid is used as the copper-containing aqueous solution  4  without the above processing steps. The industrial waste liquid  300  can be optionally mixed with the copper-containing aqueous solution  4  and the clear liquid  1  to form the mixture  5 .  
         [0025]    Optionally, the mixture  5  is concentrated to a predetermined level before being charged in the crystallization tank D to increase the yield of copper oxide. The concentration of the mixture  5  is not particularly limited, as long as the yield of copper oxide is increased. For treating a waste liquid from PCB plant, the mixture  5  can be concentrated up to, for example, 15-25 wt. % copper.  
         [0026]    A stream from the crystallization tank D passes through a solid/liquid separation tank E to be separated into a solid  6  and a filtrate  8 . The solid  6  is dried to obtain copper oxide mass that has up to about 40 wt. % of copper. The filtrate  8  is a saturated aqueous solution containing NaCl, KCl, CaCl 2 , Na 2 SO 4 , K 2 SO 4             CaSO 4 . The solid/liquid separation tank E can be any solid/liquid separation device such as a paper filter, a press filter or a centrifugation device.  
         [0027]    The filtrate  8  is recycled toward a treatment agent recovery tank F. A recovered solution  9  is discharged from the treatment agent recovery tank F and is charged in a tail gas recovery equipment G to be saturated with the tail gases  7 ,  11 . The saturated tail gases  7 ,  11  can be an oxidant product for sale, or recycled to the stirring tank A. The recovered solution  9  saturated with the tail gases  7 ,  11  is clear, and has a powerful oxidizing ability. The ratio of the yield of the tail gas  11  to the tail gas  7  is about 8.5:1.5-9.5:0.5.  
         [0028]    The invention can be applied to, but not limited to, waste treatments of various electronic manufacturing fields such as PCB.  
       EXAMPLE I  
       [0029]    20 T/d of copper-containing waste sludge  100  is weighted and charged in the stirring tank A. 3.5 T/d of sulfuric acid/hydrogen chloride/potassium permanganate (80/15/5) solution is added in the stirring tank A and stirred until the clear liquid  1 , the residue  2  and the tail gas  11  are obtained. The clear liquid  1  is charged in the copper solution tank C. The residue  2  is filtered through the filtering device B to obtain a yellowish brown solid  3  and the copper-containing aqueous solution  4 . The tail gas  11  is charged in the tail gas recovery equipment G. The yellowish brown solid  3  is the polymer coagulant  3 . The yield of the yellowish brown solid is 16.5 T/d.  
         [0030]    The copper-containing aqueous solution  4  is charged in the copper solution tank C and mixed with the clear liquid  1  to obtain the mixture  5 . The converting agent  400  and the converting aid agent  400 ′ are added in the crystallization tank D after the mixture  5  has been charged in the crystallization tank D to generate a stream and a tail gas  7 . The stream from the crystallization tank D then passes through a solid/liquid separation tank E to obtain a filtrate  8  and a solid  6 . The solid  6  has about 40 wt. % of copper oxide after having been dried. The yield of the copper oxide is 30 T/d.  
         [0031]    The filtrate  8  is recycled toward the treatment agent recovery tank F. A recovered solution  9  is discharged from the treatment agent recovery tank F and charged in the tail gas recovery equipment G to be saturated with the tail gases  7 ,  11 . The saturated recovered solution  9  is a clear and colorless solution. About 20 T/d of the saturated recovered solution  9  is recycled toward the stirring tank A, and the remaining of the saturated filtrate may be sold as an oxidant product  10 . The yield of the oxidant  10  is 74 T/d. The ratio of the yield of the tail gas  11  to the tail gas  7  is about 9:1.  
       EXAMPLE II  
       [0032]    20 T/d of copper-containing waste sludge  100  is weighted and charged in the stirring tank A. 100 T/d of acidic etching waste solution is added in the stirring tank A and stirred until the clear liquid  1 , the residue  2  and the tail gas  11  are obtained. The clear liquid  1  is charged in the copper solution tank C. The residue  2  is filtered through the filtering device B to obtain a yellowish brown coagulant solid  3  and the copper-containing aqueous solution  4 . The tail gas  11  is charged in the tail gas recovery equipment G. The yield of the yellowish brown solid is 15 T/d.  
         [0033]    The copper-containing aqueous solution  4  is charged in the copper solution tank C and mixed with the clear liquid  1  to obtain a mixture  5 . A converting agent  400  and a converting aid agent  400 ′ are added in the crystallization tank D after the mixture  5  has been charged in the crystallization tank D. A stream from the crystallization tank D then passes through a solid/liquid separation tank E to obtain a filtrate  8  and a solid  6 . The solid  6  has about 40 wt. % of copper oxide after having been dried. The yield of the copper oxide is 30 T/d.  
         [0034]    The filtrate  8  is recycled toward the treatment agent recovery tank F. A recovered solution  9  is discharged from the treatment agent recovery tank F and charged in the tail gas recovery equipment G to be saturated with the tail gases  7 ,  11 . The saturated recovered solution  9  is a clear and colorless solution. About 21 T/d of the saturated recovered solution  9  is recycled toward the stirring tank A, and the remaining of the saturated filtrate can be sold as an oxidant product  10 . The yield of the oxidant  10  is 75 T/d. The ratio of the yield of the tail gas  11  to the tail gas  7  is about 9:1.  
         [0035]    Usually, a copper mine has about 5 wt. % of copper. However, the copper-containing waste sludge or liquid has about 8-12 wt. %, which is considerably higher than the original copper mine and therefore has a high value. Copper oxide therefore is recovered at a high yield from the copper-containing waste sludge or liquid by the method of the invention. The copper oxide is directly generated without intermediate forms of copper hydroxide, which is an important improvement of the art.  
         [0036]    In the method of the invention, in addition to the highly effective recovery of copper, all of the products generated during the treatment of the waste sludge or liquid by the method of the invention, especially the coagulant and the oxidant, are recovered and recycled, and may even be sold as commercial products. Therefore, nothing is disposed of and no environmental pollution occurs. Furthermore, the acidic etching waste solution can be used instead of the first treatment agent and/or the second treatment agent to separate the coagulant from the copper-containing waste sludge. Therefore, not only the cost of treating the waste sludge or liquid is greatly reduced, but environmental pollution can be also prevented.  
         [0037]    It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the forgoing, it is intended that the present invention cover modification and variation of this invention provided they fall within the scope of the following claims and their equivalents.