2010 International Conference on Digital Manufacturing & Automation
Recovery of copper from bio-leaching solutions of waste printed circuit boards waste by ion exchange Zhang Chenglong, Cai yujia, Wang Jingwei, Bai Jianfeng, Zhou yuan, Wu Wenjie School of Environmental Engineering Shanghai Second Polytechnic University Shanghai 201209, China
[email protected]
Mao Wenxiong Xiongyue Environment Protection Tech. Co. Ltd Huizhou 516000, China
[email protected]
Abstract—According to the properties of bioleaching solutions of printed circuit boards (PCBs), copper in the leaching solution were recovery by ion exchange with macroporous styrene iminodiacetic acid chelating resin D401. The bed height of resin，flow rate，pH value on copper adsorption had been studied. Work Exchange Capacity (WEC) of copper increased with increasing bed height of resin and flow rate. The copper WEC of 7.88 mg/mL can be obtained with pH 2.5 and 200 mm bed height at flow rate of 2 mL/min. More than 99.5% of copper could be eluted from loaded resin to get the copper enriched solution by 1.0 M sulphuric acid at A/R ratio 20 in at flow rate of 2 mL/min. Results of the present investigation indicated that D401 resin can efficiently recovery copper from bioleaching solution of PCBs.
metals from ores, data pertaining to its application for the extraction of electronic waste material is still scanty. Recently, a few studies have been undertaken for the extraction of metals from electronic scrap/printed circuit boards [6]. Our research group has therefore focused on studying bioleaching of metals from PCBs. The studies were conducted with Thiobacillus ferrooxidans and Thiobacillus thiooxidans. Thiobacillus ferrooxidans was able to mobilize Cu into the leachate from actual printed circuit boards by 99.0 % at 9 days of bioleaching time and 0.5~1.0 mm of size range. The typical bioleaching solution contained 1.5-2 g/L Cu, 2.5-3.5 g/L Fe, 0.01-0.02 g/L Cr, 0.06-0.08 g/L Sn, 0.005-0.007g/L Zn [7]. Due to the low pH and multicomponent mixtures of bioleaching solutions (pH < 2.5) from PCBs, little work focused on the study of it’s properties and purification. Ion exchange process has been developed as a major option for separation of metals from different dilute aqueous solutions. Thus, in this study, a process of ion exchange for recovery copper from the bioleaching solutions was developed. The main purpose of thiswork is to investigate the feasibility of adsorbing of copper ions in complex dilute bioleaching solution by using D401.
Keywords- Waste printed circuit boards, Bioleaching, Copper, Ion exchange, Resin
I.
INTRODUCTION
Printed circuit boards (PCBs), an essential part of almost all Electric and electronic equipment (EEE), are widely subsistent in EEE. In recent years, the average rate of worldwide PCBs manufacture increases by 8.7% [1]. PCBs’ composition is quite varied, containing polymers, ceramics and metals. The typical metals in PCBs consist of copper (20%), iron (8%), tin (4%), nickel (2%), lead (2%), zinc (1%), silver (0.2%), gold (0.1%), and palladium (0.005%) [2-3]. Recycling of waste PCBs is an important subject not only from the treatment for waste but also from the recovery of valuable materials. The existing processes of recycling PCBs are either pyrometallurgical; or hydrometallurgical, which generate atmospheric pollution through the release of dioxins and furans or high volumes of effluents[4]. Some authors have used mechanical processing as an alternative to concentrate the metals in one fraction and the polymers and ceramics in another. The metal concentrate fraction can be sent to electrochemistry processes in order to separate the metals among themselves. However, such processes are costly due to high consumption of energy and are not regarded as economical way to extract valuable components from wastes [5]. Use of microorganisms for the recovery of metals from wastes could be an economical alternate to these processes. Bio-hydrometallurgical techniques allow metal cycling by processes similar to natural biogeochemical cycles. Though, this process has been successfully applied for the leaching of 978-0-7695-4286-7/10 $26.00 © 2010 IEEE DOI 10.1109/ICDMA.2010.428
II.
EXPERIMWNTAL
A. Materials The scraps of actual PCBs, which were used as main board of personal computers, were obtained from Shanghai Weimei Corporation of Science and Technology, China. The concentrations of copper in the aqueous solution obtained from the bioleaching of the PCBs was 2.26 g/L. Macroporous styrene iminodiacetic acid chelating resin D401 was supplied by Shanghai Huazhen Science and Technology Corporation, In fact, the functional group of this resin is iminodiacetate, as shown in Fig. 1. All other chemicals such as sulphuric acid, sodium hydroxide, etc were of AR grade.
Figure 1. Functional group of D401 resin [8]
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B. Pre-treatment of resin The chelating resins were eluted with acid solution to remove metal species, rinsed with deionised water, eluted with four bed volumes of NaOH 5% solution and rinsed with distilled water until the pH value of the eluent reached 7.0– 8.5. The resins were dried at 100-110 ℃ and allowed to cool in a desiccator.
W E C (mg/mL)
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C. Effect of pH The initial pH of bioleaching solution used in the experiments was 2.5. The pH of the bioleaching solution was adjusted to the desired value by adding dilute H2SO4 or NaOH solution Figure 4 shows the effect of pH of bioleaching solution on the WEC at room temperature with 150 mm bed height at 2 mL/min. There is an obvious increase in the extraction rate of copper with the increase of initial pH value. In general, most chelating exchangers are weakly acidic in nature. The iminodiacetate and aminophosphonate functional groups are affected by pH, due to the presence of acidic groups, which can dissociate depending on pH. At lower pH values, only a small fraction of the functional groups will likely be dissociated and since cations cannot be removed by neutral acids, the nickel loading capacity of the resins is reduced [9-10]. The pH of the solution leaving the column should be high at the beginning of the experiment, because of the sodium ions, with a basic nature, introduced into the solution from the resin. The pH then should decrease gradually, until reaching the pH of the feed solution. It was verified that some copper was precipitated from solution during the pH adjustment to higher than 3.
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W EC (m g/m L)
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B. Effect of flow rate The results for different solution flow rates at room temperature with 150 mm bed height are shown in Figure 3. When the flowrate increased from 0.5 to 5 ml/min, the WEC decreased. This is because in the high flowrate of the solution, the residence time of the solute in the column is not enough to remove of copper anions from the solution.
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Figure 2. The rffect of bed height on the WEC
D. Elution of copper from loaded resin Sulphuric acid was used to elute all the copper from the copper loaded resin. The elution studies were carried out by varying the sulphuric acid concentration from 0.5 to 2.0 M at flow rate of 2 mL/min. The elution of copper increased with increasing concentration of the acid in eluant. The 99.5% copper was found to be eluted by 1.0 M sulphuric acid at A/R ratio 20 in at flow rate of 2 mL/min.
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Figure 4. The rffect of pH on the WEC
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100 150 200 bed height of resin (mm)
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A. Effect of bed height of resin The effect of height of resin on Work Exchange Capacity (WEC) was investigated at room temperature with pH 2.5 at flow rate of 2 mL/min. The results presented in Figure 2 shows that the WEC of copper increases with the increase in bed height of resin.
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RESULTS AND DISCUSSION
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C. Procedure Ion-exchange experiments were conducted in a cylindrical glass column with a diameter of 11.2 mm and a height of 300 mm. The resin was packed into the column above glass wool. The bioleaching solution of the PCBs was pumped from the top of the column. At the end of every 20 ml, 2 ml of effluent solution was taken and analyzed for Cu. The concentrations of copper was analyzed by Inductively Coupled Plasma-atomic Emission Spectrometry (ICP-AES) and the pH was measured using a pH meter. The breakthrough point has been fi xed at 1% (2 mg/L) of the initial concentration. III.
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flow rate (mL/min)
Figure 3. The rffect of flow rate on the WEC
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IV.
CONCLUSIONS
REFERENCES
In this study, macroporous styrene iminodiacetic acid chelating resin D401 was used to remove copper ions from bioleaching solution of PCBs. The results of this study show that D401 resin can efficiently recovery copper from bioleaching solution with pH of 2.5. The copper WEC of 7.88 mg/mL can be obtained at room temperature with pH 2.5 and 200 mm bed height at flow rate of 2 mL/min. More than 99.5% of copper could be eluted from loaded resin to get the copper enriched solution by 1.0 M sulphuric acid at A/R ratio 20 in at flow rate of 2 mL/min. The spent solution after the adsorption of copper could be again utilized for the leaching of PCBs after bacterial inoculation.
[1]
K. Huang, J. Guo and Z. Xu, Recycling of waste printed circuit boards: A review of current technologies and treatment status in China. Journal of Hazardous Materials, vol.164, pp. 399-408 , 2009. [2] W. He, G. Li, X. Ma, H. Wang, J. Huang, M. Xu, C. Huang, WEEE recovery strategies and the WEEE treatment status in China, J. Hazard. Mater. Vol. B136, pp. 502–512, 2006. [3] T. Lehner, Integrated recycling of non-ferrousmetal at Boliden Ltd., in: Proceedings of the IEEE International Symposium on Electronics and the Environment, 1998, pp. 42–47. [4] Menad, N., Björkman, Bo., Allain, E.G., Combustion of plastics contained in electric and electronic scrap. Resour. Conserv. Recycl. Vol. 24, pp. 65–85, 1998. [5] Sadia Ilyas, Munir A. Anwar, Shahida B, et al. Bioleaching of metals from electronic scrap by moderately thermophilic acidophilic bacteria. Hydrometallurgy, vol. 88, pp.180-188, 2007. [6] Brandl, H., Bosshard, R., Wegmann, M. Computer-munching microbes: metal leaching from electronic scrap by bacteria and fungi. Hydrometallurgy, vol. 59, pp.319-326, 2001. [7] Jingwei Wang, Jianfeng Bai, Jinqiu Xu, Bo Liang, Bioleaching of metals from printed wire boards by Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans and their mixture, Journal of Hazardous Materials, vol. 172, pp. 1100-1105, 2009. [8] Tsz-Him Shek, Anthony Ma, Vinci K.C. Lee, Gordon McKay. Kinetics of zinc ions removal from effluents using ion exchange resin. Chemical Engineering Journal, vol. 146, pp. 63–70, 2009. [9] Kononova, O.N., Kholmogorov, A.G., Kachin, S.V., Mytykh, O.V., Kononov, Y.S., Kalyakina, O.P., Pashkov, G.L.. Ion exchange recovery of nickel from manganese nitrate solution. Hydrometallurgy, vol. 54, pp. 107-115, 2000. [10] F.D. Mendes, A.H. Martins. Recovery of nickel and cobalt from acid leach pulp by ion exchange using chelating resin. Minerals Engineering, vol. 18, pp. 945–954, 2005.
ACKNOWLEDGMENT The authors gratefully acknowledge the financial support from Innovation Program of Scientific Research of Shanghai Municipal Education Commission (No.09YZ451 and No.09YZ448), Chinese National Plan of High Technological Research and Development (No. 2006AA06Z366), Key Scitech Research Project of Guangdong Province (No. 2010A080804008) and Leading Academic Discipline Project of Shanghai Municipal Education Commission, Project Number(No.J51803).
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