Waste Management 29 (2009) 2842–2845

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Waste Management

journal homepage: www.elsevier .com/ locate/wasman

The general utilization of scrapped PC board

Robert Liu a, R.S. Shieh a, Ruth Y.L. Yeh a,*, C.H. Lin b

a Department of Chemical and Materials Engineering, Minghsin University of Science and Technology, Hsinchu, Taiwanb Graduate School of Optomechatronic and Materials, Wu Feng Institute of Technology, Chiayi, Taiwan

a r t i c l e i n f o a b s t r a c t

Article history:Accepted 13 July 2009Available online 14 August 2009

0956-053X/$ - see front matter � 2009 Elsevier Ltd.doi:10.1016/j.wasman.2009.07.007

* Corresponding author. Tel.: +886 3 6019311; fax:E-mail address: yehyl@must.edu.tw (R.Y.L. Yeh).

The traditional burning process is used to recover copper from scrapped PC board (printed circuit board)but it causes serious environmental problems. In this research a new process was developed which notonly prevents pollution problems, but also maximizes the utility of all the materials on the waste board.First, the scrapped PC board was crushed and grounded, then placed in the NH3/NH5CO3 solution withaeration in order to dissolve copper. After distilling the copper NH3/NH5CO3 solution and then heatingthe distilled residue of copper carbonate, pure copper oxide was obtained with particle size of about0.2 lm and the shape elliptical. The remaining solid residue after copper removal was then leached with6 N hydrochloric acid to remove tin and lead. The last residue was used as a filler in PVC plastics. The PVCplastics with PC board powder as filling material was found to have the same tensile strength as unfilledplastics, but had higher elastic modulus, higher abrasion resistance, and was cheaper.

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1. Introduction

PC board, which is widely used in electronic products, is madefrom fiber glass reinforced epoxy resin as substrates (Zhang andForssberg, 1999; Schlummer et al., 2007). The copper circuit is onthe surface of the PC board, which is usually covered by a layerof tin/lead alloy, and between the layers of multi-layer PC board.Several thousand tons of scrapped PC boards are produced fromelectronic industry annually in Taiwan. Copper is usually recoveredfrom the scrapped PC boards by burning them. Then the burnedresidue is leached by an acid. The burning of PC boards not onlycontaminates the air with the dioxin produced as a result of burn-ing but also pollutes the underground water and rivers with heavymetals. Both tin/lead alloy and fiberglass can not be recovered bythis burning process. Utilization of magnetic and electrostatic sep-aration in the recycling of printed circuit board (PCB) scrap has alsobeen studied (Veit et al., 2005). But, the recovery of tin/lead alloy orfiberglass still remains unresolved. There are some macroscopic re-view papers concerning recovery and recycling of electronic waste(Cui and Zhang, 2008; Lee et al., 2007; Kang and Schoenung, 2005;Guo et al., 2009). In Cui and Zhang (2008), leaching of metals fromelectronic waste, gold for Au-containing e-waste, and recovery ofbase metals, including copper, lead and tin from scrap printed cir-cuit board were discussed. The base metal recovery is achieved byusing nitric acid leaching and electrochemical processing. The cop-per recovery by reduction and electrolytic refinery was also re-viewed by Kang and Schoenung. In Korea, the commercialprocesses and the status of developing new technologies for the

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recycling of metallic values from waste PCB are also briefly de-scribed in Lee’s paper (2007). The recycling of non-metallic frac-tions from waste PCB was reviewed by Guo et al. (2009).

A new method was developed in this study, which utilized NH3/NH5CO3 solution to leach copper and hydrochloric acid to leach tinand lead. The resulting leached residue was then used as a filler forPVC plastics. This method not only had zero pollution but alsomaximized the materials recovered from the PC board. Table 1 isthe composition of the scrapped PC board, in which copper is a ma-jor component of the wasted PC board.

2. Experimental procedure

Scrapped PC board is first crushed and grounded to pass 200mesh sieves and, then was placed into NH3/NH5CO3 solution withaeration. Copper was then dissolved by the following reaction

Cuþ 3NH3 þ NH5CO3 þ 0:5O2 ! CuðNH3Þ4CO3 þH2O ð1Þ

After the residue was filtered, the remaining solution washeated to remove NH3 and CuCO3 was precipitated from the solu-tion as shown in the following equation

CuðNH3Þ4CO3 ! CuCO3 þ 4NH3 ð2Þ

The copper carbonate was subsequently heated at 550 �C toform copper oxide

CuCO3 ! CuOþ CO2 ð3Þ

After NH3/NH5CO3 solution leaching, the residue of PC boardpowder was then extracted by hydrochloric acid at different con-centrations and times. After tin and lead were dissolved, the final

Table 1The composition of scrapped PC board (Liu, 1993).

Manufacturer Cu Sn Pb Total metals(%)

Epoxy and glass fiber (%)

1 37.48 0.98 0.69 39.18 60.822 30.06 1.24 0.73 32.06 67.943 37.90 0.76 0.52 39.21 60.794 15.04 0.18 0.046 15.30 84.915 14.82 0.23 0.026 15.09 84.91

1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5120001400016000180002000022000240002600028000300003200034000360003800040000

Cu

(ppm

)

n1 n2 n3 n4 n5

time (day)

Fig. 2. Cu ion concentration in leaching solution vs time by ICP with variousconcentration of NH3/NH5CO3.

R. Liu et al. / Waste Management 29 (2009) 2842–2845 2843

PC board solid powder was again filtered, washed, dried, ballmilled to pass 50 mesh sieve and was added to PVC plastics asa filler. Ten gram of PVC powder, 2.5 ml of DOP (o-dioctyl phthal-ate) plasticizer and different quantity of final wasted PC boardpowder (0.1–0.9 g) were mixed homogeneously with a magneticstirrer, poured into a teflon sheet and hot pressed at 170 �C toform different shapes of plastic composites. The mechanical prop-erties of the PVC composites were tested. The tensile strengthwas tested by Universal Testing Machine (Testometric Micro350, UK) and abrasion resistance tested by Abrasion Tester (HT-8360 Taber Type Abrasion Tester, Hung TA Instrument Co., Ltd.,Taiwan). The weight of each abrasive wheel was 500 g and thecounts of rotating numbers were 1000. The whole process wasshown in Fig. 1.

3. Results and discussion

Hundred gram of the crushed and grounded wasted PC boardpowder was mixed by magnetic stirrer and aerated with 500 mLof NH3/NH5CO3 solution. Copper was then dissolved and Cu(NH3)4-

CO3 complex was formed as shown in Eq. (1). n1 in Fig. 2 repre-sents exact stoichiometric quantity of NH3/NH5CO3 needed andn2 represents the double stoichiometry needed. Fig. 2 shows that

Scarpped PC board

NH3 recovery

CuCO3

PC board powder liquid

CuO

PVC

PVC Plastics

HCl dissolution

crushing and grinding

distillation

filtration

calcination

hot kneading

Cu dissolution

NH3/NH5CO3 solution

Sn/Pb Solution

aeration

solid liquid

filtration

Fig. 1. The recovery of useful materials from scrapped PC board.

more than stoichiometric quantity of NH3/NH5CO3 was needed inthe solution. The higher the NH3/NH5CO3 concentration is, thehigher the copper ion concentration in the NH3/NH5CO3 leachingsolution is. During aeration, copper ion increased with time firstand subsequently decreased with time because NH3 was drivenoff from the solution after prolonged aeration. Fig. 2 and Table 2show that copper ion was in tens of thousands ppm, and Fe, Al,Pb, Zn, Sn, Ni, Si, and Br ions were only in tens of ppm. Nickeland zinc ion were higher than other ions because they formedcomplex with ammonia too. Br is a component of PC board as a fireretardation agent. The copper and other metal-ion concentrationswere analyzed by ICP (Inductive coupled plasma atomic emission,CirOS, Spectro Co., Germany) with copper oxide powder leached by7 N nitric acid. Table 3 analyzed by XRF (X-ray fluorescence, XEPOS,Spectro Co., Germany) shows that after leaching with NH3/NH5CO3,

the copper left in the PC board powder decreased with the concen-tration of NH3/NH5CO3. For n3 of stoichiometric quantity of NH3/NH5CO3, only 0.263% copper is left in the remaining PC boardpowder.

During the distillation of leaching solution, ammonia was dri-ven off, and blue–white copper carbonate was precipitated, whichwas then heated at 550 �C. A black powder was obtained that wasfound to be copper oxide by XRD (X-Ray Diffractometer, X-RD-6000, Shiomadzu, Japan) spectrum (Fig. 3). Fig. 4 shows the copperoxide particle is elliptical having a size of 0.2 lm. Fig. 5 is the SEMimage of the PC board powder after NH3/NH5CO3 leaching, and it isfiber-like.

After NH3/NH5CO3 leaching, 50 g of the PC board powder wassubsequently leached by 300 mL of hydrochloric acid to removedtin and lead. Fig. 6 shows that the concentrations of tin and leadion in the leaching solution. They increased with the concentrationfrom 2 to 6 N and then leveled off. The concentration of tin washigher than lead because tin concentration was higher than thatof lead in the original PC board powder. Table 4 shows the concen-tration of various ions with different leaching time. The ion con-centrations did not increase with time. The separation process oftin, lead, aluminum, iron, and copper ion needs further investiga-tion. Different solvents instead of hydrochloric acid, NaOH/NaNO3

or silicofluoric acid/H2O2 are suggested for further study. Table 5shows the composition of PC board powder after 6 N hydrochloricacid leaching and concentrations of metals did not increase withtime. Table 5 also shows that glass is a major composition in thefinal PC board powder. After hydrochloric acid leaching, all copper,zinc, and nickel were removed, but some tin and lead were still inthe PC board powder.

Table 6 shows that 10 g of PVC plastic powder mixed with 0.1–0.9 g of final remaining PC board powder as filler was found to have

Table 2Ion concentration in the leaching solution with various concentration of NH3/NH5CO3 after 2 days of leaching by ICP.

Multiple of stoichiometry Ion conc. (ppm)Fe Al Pb Zn Sn Ni Si Br

n3 83.1 22.47 24.82 356.8 11.04 125.2 16.72 10.43n4 6.12 0.601 86.7 320.7 49.28 334.1 9.17 4.758n5 112.9 0.511 74.7 493.4 24.63 438.6 11.23 6.38

Table 3Cu% left in PC board powder after 2 days of NH3/NH5CO3 leaching (analyzed by XRF).

Multiple of stoichiometry n1 n2 n3

wt% 5.21 2.58 0.263

Fig. 3. X-ray spectrum of copper oxide.

Fig. 4. SEM picture of CuO.

Fig. 5. SEM image of scrapped PC board powder after NH3/NH5CO3 leaching.

2 4 6 8 10 120

500

1000

1500

2000

2500

3000

3500

4000

Sn o

r Pb

(pp

m)

HCl (N)

Sn 1day Sn 2days Pb 1day Pb 2days

Fig. 6. Concentration of Sn and Pb in the HCl leaching solution.

Table 4Metal ion concentration leached by 6 N hydrochloric acid by ICP.

Day Conc. (ppm)

Sn Pb Al Fe Cu Zn Ni

1 2544 1109 3475 290.5 271.3 * *

2 2495 1014 4029 241.3 442.9 * *

3 2537 987 2808 244.3 262.9 * *

4 2547 1123 2768 261.4 331.3 * *

Table 5PC board powder composition (excluded oxygen, analyzed by XRF).

Day wt%

Sn Pb Al Fe Si Cu Zn Ni

1 0.271 0.10 17.65 2.103 >70.84 * * *

2 0.592 0.08 15.56 1.287 >72.23 * * *

3 0.418 0.08 14.49 1.04 >73.59 * * *

4 0.467 0.09 16.31 0.76 >73.01 * * *

Table 6Mechanical properties of PVC plastics with PC board powder as filler.

PC boardpowder(g)

Tensile strength(kg/mm2)

Elongation(%)

Elastic modulus(kg/mm2)

Abrasionresistanceindex

0.0 3.46 217.59 81.0200 0.2780.1 2.27 36.71 78.3746 0.3220.3 2.59 11.40 80.4910 0.4620.5 3.43 5.45 98.7784 0.5810.7 3.42 5.72 104.4788 0.2130.9 3.45 5.28 105.0765 0.196

2844 R. Liu et al. / Waste Management 29 (2009) 2842–2845

R. Liu et al. / Waste Management 29 (2009) 2842–2845 2845

the same tensile strength as unfilled plastics, but have high elasticmodulus, more scratch resistance and was cheaper in cost.

4. Conclusions

1. More than stoichiometric quantity of NH3/NH5CO3 is needed inthe leaching solution to completely remove copper in the PCboard powder.

2. For triple amount of stochiometric quantity of NH3 /NH5CO3

used, only very minor (0.263%) copper is left in the remainingPC board powder.

3. The purity of copper oxide is very high because of the high pur-ity of copper NH3/NH5CO3 solution.

4. The particle size of the copper oxide powder is about 0.2 lm,and its shape is elliptical.

5. 6 N hydrochloric acid is needed to leach tin and lead for the PCboard powder, almost all the tin, lead, copper can be leachedout.

6. The plastics kneaded by PVC plastic powder and final remainingPC board powder as filler showed the same strength as unfilledPVC. The PVC composite has a higher elastic modulus andhigher scratch resistance. More importantly, it is much cheaperby using wasted PC board materials.

7. The addition of 0.9 g of final remaining wasted PC board powderinto 10 g of PVC plastic as filler, the tensile strength was3.45 kg/mm2, the strain was 5.28% and the abrasion resistancewas 105.0765 kg/mm2 compared to those of 3.46 kg/mm2,217.59% and 81.02 kg/mm2 respectively of original PVC powder.

Acknowledgement

It is gratefully acknowledged that this research was funded byNational Science Council in Taiwan by the project of NSC-94-2622-E-159-002-CC3.

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