Co-processing waste printed circuit boards and spent tin stripping ...

Research Article pubs.acs.org/journal/ascecg

Green Process of Metal Recycling: Coprocessing Waste Printed Circuit Boards and Spent Tin Stripping Solution Congren Yang,† Jinhui Li,*,† Quanyin Tan,† Lili Liu,‡ and Qingyin Dong‡ †

State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China ‡ Basel Convention Regional Centre for Asia and the Pacific, Beijing 100084, China S Supporting Information *

ABSTRACT: Electronic waste (e-waste), including waste printed circuit boards (PCBs), has caused global concern owing to its potential environmental pollution and rich resource content. Previous studies have indicated that urban mining for metals recycling can decrease energy consumption and pollutants emission compared to the extraction of metals from natural minerals. During the production of PCBs, a large amount of spent tin stripping solution (TSS) is simultaneously generated, containing the significant amounts of metal ions and residue nitric acid. In this study, the coprocessing of waste PCBs and spent TSS at room temperature was proposed and investigated, with the aim of developing an environmentally sound process to address these problems. This coprocessing approach proved to be effective. 87% of the Sn−Pb solder, 30% of the Cu, 29% of the Fe, and 78% of the Zn was leached from waste PCBs with spent TSS after 2 h, at room temperature. Moreover, approximately 87% of the electronic components were dismantled from waste PCBs. About 99% of the Sn, Pb, Fe, Cu, and Zn were recovered from the leaching solutions by chemical precipitation. The proposed green process has substantial advantages over traditional recovery methods of heating waste PCBs, in terms of both material and energy efficiency. KEYWORDS: E-waste, Waste printed circuit boards, Spent tin stripping solution, Green chemistry, Coprocess, Metal recycling

■

these methods generally operate at about 250 °C. For example, Zeng et al.31 used water-soluble ionic liquid as a heating medium to dismantle ECs and recover tin solder from waste PCBs, nearly 90% of the ECs were removed from the waste PCBs, at 250 °C. Simultaneously, an automatic system for disassembling waste PCBs with heated air at 265 ± 5 °C was developed by Wang et al.32 But more energy was consumed by heating waste PCBs above the melting point of tin solder. Recently, a chemical reagent was used to recover tin solder from waste PCBs. Yang et al. reported that 99% of tin could be leached with SnCl4 and HCl at 60 to 90 °C, and the tin was then recovered from the purified solution by electrodeposition.33 HBF4 containing H2O2 was used to dissolve tin solder by Zhang et al., and almost 100% of the solder was dissolved.34 Recently, Zhang et al.35 reported that a leachant containing methanesulfonic acid and hydrogen peroxide can also selectively dissolve the Sn−Pb solder. Although these techniques were conducted at lower temperatures, new chemical reagents (such as SnCl4, HCl, HBF4, H2O2) were consumed. For metals recycling from waste PCBs without ECs,

INTRODUCTION In order to achieve environmental and metal sustainability, green processes need to be developed for the recycling of metal from waste.1−4 For example, printed circuit boards (PCBs) are widely used in different fields such as electric and electronic equipment, information, and sensing industries.5−8 Waste PCBs contain more than 40 metals, including valuable metals (e.g., Sn, Fe, Cu, Zn) and hazardous substances (e.g., Pb, Cr, Cd).9,10 The informal recycling of metals from waste PCBs, especially in developing countries, has caused serious environmental pollution and human health risks.11−15 Using the “Twelve Principles of Green Chemistry” is the most effective way to solve these issues while at the same time alleviating the shortage of mineral resources.16−19 Based on the principles of Green Chemistry, many environmentally sound processes have been developed to recover metal from e-waste.20−25 Undoubtedly, the metal recycling from waste PCBs is necessary to the sustainable development of the electronics industry, and many techniques for waste PCB dismantling and metals recycling have been developed. For dismantling the electronic components (ECs) and recovering the tin solder from waste PCBs, thermal treatmentssuch as infrared heating, using an electric heating tube, liquid-medium heating, and solder-bath heatingare most commonly used.26−30 All © 2017 American Chemical Society

Received: January 21, 2017 Revised: March 2, 2017 Published: March 9, 2017 3524

DOI: 10.1021/acssuschemeng.7b00245 ACS Sustainable Chem. Eng. 2017, 5, 3524−3534

Research Article

ACS Sustainable Chemistry & Engineering Table 1. Composition of Waste Printed Circuit Boards (%) element

Sn

Pb

Cu

Fe

Al

Zn

Ni

Cr

Cd (g/t)

Au (g/t)

Ag (g/t)

bare boards ECs total

10.12 3.20 6.0

3.20 0.68 1.7

21.62 13.80 16.9

0.21 19.49 11.8

1.36 6.91 4.7

0.056 5.66 3.4

0.036 0.65 0.4

0.027 0.53 0.3

0.53 14.45 8.9

40.76 24.4

194.91 112.68 145.7

Table 2. Metal Concentrations in Spent Tin Stripping Solution Sn (g/L)

Cu (g/L)

Fe (g/L)

Pb (mg/L)

Zn (mg/L)

Ni (mg/L)

Al (mg/L)

Cr (mg/L)

Cd (μg/L)

H+ (mol/L)

NO3− (mol/L)

3.59

4.57

5.17

6.35

3.93

36.83

15.81

7.97

1.64

4.4

4.9

electrostatic separation,36−39 wet jigging,40 froth flotation,40,41 air current separation,42 etc., have been used to separate metals from nonmetals, pure metals can then be extracted from the mixed metals by vacuum metallurgy.43−46 Hydrometallurgy, 47−51 biohydrometallurgy, 52−56 and supercritical fluid57−59 have also been applied, to leach valuable metals from waste PCBs. Valuable metals can be further recovered from leaching solution by adsorption-elution,60 electrowinning,61,62 and so on. Spent tin stripping solution (TSS)the tin, iron, copper, and nitric acid containing waste solutions originally from PCBs productionis also classified as hazardous waste.63 Nitric acid can be regenerated by solvent extraction−stripping64 and diffusion dialysis,65,66 and the valuable metals can then be recovered by electrowinning,63,66−68 precipitation,64−67 etc. The recycling of metals (e.g., Sn, Cu, et al.) is becoming more and more important, in order to counteract the depletion of mineral resources, especially as the demand for these metals continues to increase. While all of the methods discussed above have proved effective at recovering metals from waste PCBs, it is essential to develop more environmentally friendly processes that exhibit better performance in terms of both valuable-metal recycling and hazardous-substance control. In this study, a technique for coprocessing waste PCBs and spent TSS at room temperature was developed and analyzed. This proposed process can not only meet these goals but also conserve energy, compared to traditional methods.

■

EXPERIMENTAL SECTION

Characteristics of the Samples. Waste PCBs from desktop and laptop personal computersafter the central processing unit (CPU) and random access memory (RAM) had been removedwere used in all the experiments. First, ECs were removed from the PCBs by heating. The mass fractions of the ECs and the bare boards (without ECs) were 60% and 40%, respectively. The bare boards and ECs were crushed and screened to −1 mm. An appropriate amount of sample was dissolved in aqua regia for 1 day, and then, the leached liquid was filtered through a 0.45 μm microfiltration membrane. The metal content in the filtrate was detected via inductively coupled plasma (ICP) (PE OPTIMA 8000). The results are presented in Table 1. Most of the Sn in the spent TSS presented as insoluble hydrated stannic oxide. The spent TSS was therefore filtered through a 0.45 μm microfiltration membrane before determining the metal concentration via ICP. The results are presented in Table 2. Leaching of Waste PCBs with Spent TSS. The process discussed in this study is shown in Figure 1. At the top of this figure is illustrated the method for coprocessing the waste PCBs and the spent TSS. The leachate was then treated through five precipitation steps, with filtration in between each two steps. In order to the recovery Sn, Fe, Cu, and Zn from the leaching solutions by chemical precipitation, the pH of the solution was adjusted to 1.5, 3, 6, and 8, respectively. A 98% H2SO4 was used to precipitate the Pb, the molar ratio of [SO42−]/[Pb2+] was always more than 1.4.

Figure 1. Flowchart for dismantling and recovering valuable metals from waste PCBs with spent TSS. All leaching experiments were conducted at room temperature. A piece of waste PCB without the CPU and RAM was placed into a plastic box (305 mm × 240 mm × 205 mm), and then 2 L of spent TSS was added to the box. The waste PCB was completely submerged within the spent TSS. Each 0.5 h, 5 mL of solution was sampled to detect the target metals and H+ concentration. The soluble metals were determined with ICP. After the leaching, the PCB and ECs were washed with water and dried at room temperature, and the Sn, Pb, Fe, Cu, and Zn were recovered from the leaching solution via chemical precipitation (Figure 1). Small-scale pilot plant leaching experiments were also conducted at room temperature. A 24.5 kg portion of waste PCBs without CPUs 3525


Research Article

ACS Sustainable Chemistry & Engineering

Figure 2. Concentrations of H+ in solution (A), concentrations of Sn in solution and Pb extraction (B), metal extraction (C−F) during the leaching of waste PCBs. and RAM were placed into a plastic basket (675 mm × 485 mm × 400 mm), and then the plastic basket was placed into a plastic box (755 mm × 530 mm × 500 mm). A 194.5 kg portion of spent TSS was then added to the plastic box; the waste PCBs were completely submerged within the spent TSS. After leaching, the solution was sampled, to detect the target metals via ICP, and the PCBs and ECs were washed with water and dried at room temperature. Recovery of Valuable Metals. The composition of metals in solution changed with pH was calculated using Visual MINTEQ. All chemical reagents used in the experiments were analytical grade. First, 32% NaOH solution was added with a dropper, to 200 mL of the leaching solution, with a stirring speed of 160 rpm at room temperature for 1 h, and the end point pH was adjusted to 1.5. The tin precipitate was filtered, washed with deionized water, and dried at 60 °C. 2.5 mL 98% H2SO4 was then added into the filtrate to

precipitate the lead. The iron, copper, and zinc precipitation was similar to the precipitation of tin, but the pH end points were 3, 6, and 8, respectively (Figure 1). The precipitate was examined using X-ray diffraction (XRD) (Bruker D8 Advance) and X-ray fluorescence (XRF) (Shimadzu XRF-1800). The pH value of the solution was measured with a pH meter (Mettler Toledo Five Easy).

■

RESULTS AND DISCUSSION Characteristics of Waste PCBs Leached with Spent TSS. The characteristics of waste PCBs leached with spent TSS, in terms of changes in the concentrations of H+, concentrations of dissolved tin ions, and metal extraction percentage, are shown in Figure 2. The concentrations of H+ decreased from 4.4 to 2.2 mol/L in the first 2 h (Figure 2A) due to the 3526


Research Article

ACS Sustainable Chemistry & Engineering consumption of nitric acid. In the leaching process, a metal was oxidized to its ions by nitric acid; for instance, Sn0 was oxidized to Sn4+.69 Then, within the next 1 h, the concentrations of H+ further decreased (albeit more slowly) from 2.2 to 2.0 mol/L. The Sn and Pb in the waste PCBs are in the form of Sn−Pb solder. The Sn−Pb solder quickly was dissolved from waste PCBs. The Sn concentration increased from 3.6 to 11.9 g/L, and the Pb extraction percentage reached 81% after 1 h (Figure 2B). Over the subsequent 2 h, the dissolution of Pb proceeded more and more slowly, and the Pb extraction percentage finally reached 90% after 3 h. The Sn concentration in solution was 15.8 g/L after 3 h. It is well-known that tin reacts with nitric acid, which converts it into an insoluble hydrated stannic oxide. 67,69 When we used ICP to detect the metal concentrations in the leach liquid, the leach liquids had to be filtered through a 0.45 μm microfiltration membrane. Since Pb presents as Pb2+ ions in solution, the Pb extraction percentage can be used to indicate the dissolution of Sn−Pb solder. In other words, 90% of the Pb was extracted from the waste PCBs, indicating that 90% of the Sn−Pb solder was dissolved. The Cu extraction percentage increased with time, and after 3 h 36% of the Cu had been leached (Figure 2C). Scott et al.67 reported that at higher nitric acid concentrations (>2.1 mol/L), both Sn−Pb solder and Cu dissolved quickly, while at lower nitric acid concentrations ( Cu4SO4(OH)6·H2O > Cu2NO3(OH)3 > Cu(OH)2. It was concluded therefore that Cu4SO4(OH)6 and/or Cu4SO4(OH)6·H2O preferentially precipitate.72 The Cu4SO4(OH)6 or Cu4SO4(OH)6·H2O can be obtained by titration of CuSO4 solution with NaOH solution.73−76 Furthermore, the Cu4SO4(OH)6 was synthesized with urea and Cu(NO3)2 solutions containing SO42−, and the addition of sulfate caused precipitation to occur earlier.77 Cu4SO4(OH)6· H2O can also be obtained by using CuSO4 and urea as starting solutions; these can be transformed into Cu(OH)2 by adding NaOH into the solution.72 In spite of this possibility, only the characteristic peaks of Cu4SO4(OH)6·H2O were detected, in practice, with XRD (Figure 7D). The Cu4SO4(OH)6·H2O was considered as a type of metastable form of Cu4SO4(OH)6 by Zittlau et al. The hydrate form was observed to precipitate between 20 and 40 °C with pH values up to 10, but the Cu4SO4(OH)6·H2O will only transform into Cu4SO4(OH)6 at 40−50 °C. 75 This difference can explain why the Cu4SO4(OH)6·H2O precipitated first from the Cu(NO3)2 solution containing NO3− and SO42−, although the concentration of NO3− was far higher than that of SO42−. Alternatively, the formation of Cu4SO4(OH)6·H2O may be due to anion-exchange reactions of Cu 2 NO 3 (OH) 3 . Cu 2NO 3(OH)3 is a layered structure compound [like Cu2(OH)4], in which one of the OH− ions in Cu2(OH)4 has been substituted by NO3−. This NO3− ion is incorporated in the interlayer between the Cu2(OH)3 layers.80,81 Furthermore, many research reports have indicated that the NO3− ions in (M, Me)2NO3(OH)3 compounds [such as Cu2NO3(OH)3, (Cu, Zn)2NO3(OH)3, (Cu, Ni)2NO3(OH)3, etc.] can be replaced by monovalent anions (such as OH−, Cl−). Also, divalent anions (such as CO32−, SO42−), organic anions (such as acetate, terephthalate, benzoate, alkyl sulfate and alkanesulfonate ions) can replace NO3−.80−84 For instance, Meyn et al. reported that the NO3− ions in Cu2NO3(OH)3 were very easily replaced by alkyl sulfate and alkanesulfonate ions.80 Newman et al. prepared Cu2(Ac) (OH)3 by exchanging NO3− with acetate anions (Ac).81 Jimenezlopez et al. found that the Ac in Cu2(Ac) (OH)3 could be substituted by I−, simultaneously as a that anion-exchange reactions Ac−/I− was reversible.84 Stanimirova et al. stated that the NO3− in Cu2NO3(OH)3 can be replaced by Cl− to form Cu2Cl(OH)3. In this case, the Cu2Cl(OH)3 transformed into Cu4SO4(OH)6 by exchanging Cl− with SO42−.85 Figure 5C shows that Cu4SO4(OH)6·H2O(s) is converted into Cu(OH)2 when the solution pH is more than 8.70. Similar results were observed by Kratohvil et al.72 The Zn precipitation from leaching solution is similar to that for Cu, and hence, we need not discuss the Zn case here in detail again. Especially, except the anion-exchange reactions of basic Zn salts [such as Zn5(OH)8(NO3)2·2H2O],80,81 some of the Zn can also be substituted by other metal ions to form hydroxy double salts [such as (Zn, Me)5(OH)8(NO3)2·2H2O],

where the ionic radii difference between Zn and Me should be not more than 0.05 Å, such as is the case with Zn2+ and Co2+, Zn2+ and Ni2+, and Zn2+ and Cu2+.80

■

CONCLUSIONS Environmentally friendly and efficient technologies for recycling of metals from waste PCBs need to be developed. This study represents an important contribution toward this goal. A green coprocessing technology is here proposed, which can be applied to the recovery of valuable metals from waste PCBs and spent TSS at room temperature. The proposed green process proved to be effective for waste PCBs dismantling and metals recycling. Approximately 87% of the Sn−Pb solder was successfully leached from waste PCBs with spent TSS after 2 h. Simultaneously, more than 87% of the ECs were removed from waste PCBs, and 30% of the Cu, 29% of the Fe, and 78% of the Zn were also leached from waste PCBs. Small-scale pilot plant leaching experiments were conducted as well, and similarly effective results were obtained. Based on the solution composition calculation, the pH values selected for the precipitation of Sn, Fe, Cu, and Zn were 1.5, 3, 6, and 8, respectively, and the molar ratio of [SO42−]/[Pb2+] selected for the precipitation of Pb should be more than 1.4. About 99% of the Sn, Pb, Fe, Cu, and Zn were recovered from the leaching solutions by precipitation. The pure metals can be further obtained from precipitates using existing upgrading processes. As a side result, the anion−exchange reactions and metal ions substitution reactions that occurred during the precipitation of Cu and Zn were studied. Furthermore, based on the literature, a satisfactory explanation can be offered for the observations made by XRD.

■

ASSOCIATED CONTENT

* Supporting Information S

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acssuschemeng.7b00245. Development of chip packaging types; chips remained on the PCBs after 2 h of leaching with spent TSS; metal content in solution; leaching of waste PCBs with spent TSS (PDF)

■

AUTHOR INFORMATION

Corresponding Author

*Mailing address: Room 805, Sino-Italian Environmental and Energy-efficient Building, School of Environment, Tsinghua University, Haidian District, Beijing 100084, China. E-mail address: [email protected] (J.L.). Tel.: +86-10-62794143. Fax: +86-10-62772048. 3531


Research Article

ACS Sustainable Chemistry & Engineering ORCID

(18) Matus, K. J. M.; Xiao, X.; Zimmerman, J. B. Green chemistry and green engineering in China: drivers, policies and barriers to innovation. J. Cleaner Prod. 2012, 32, 193−203. (19) O’Connor, M. P.; Zimmerman, J. B.; Anastas, P. T.; Plata, D. L. A Strategy for Material Supply Chain Sustainability: Enabling a Circular Economy in the Electronics Industry through Green Engineering. ACS Sustainable Chem. Eng. 2016, 4 (11), 5879−5888. (20) Hu, Z.; Kurien, U.; Murwira, K.; Ghoshdastidar, A.; Nepotchatykh, O.; Ariya, P. A. Development of a Green Technology for Mercury Recycling from Spent Compact Fluorescent Lamps Using Iron Oxides Nanoparticles and Electrochemistry. ACS Sustainable Chem. Eng. 2016, 4 (4), 2150−2157. (21) Maât, N.; Nachbaur, V.; Lardé, R.; Juraszek, J.; Le Breton, J.-M. An Innovative Process Using Only Water and Sodium Chloride for Recovering Rare Earth Elements from Nd−Fe−B Permanent Magnets Found in the Waste of Electrical and Electronic Equipment. ACS Sustainable Chem. Eng. 2016, 4 (12), 6455−6462. (22) Singh, N.; Li, J.; Zeng, X. An Innovative Method for the Extraction of Metal from Waste Cathode Ray Tubes through a Mechanochemical Process Using 2-[Bis(carboxymethyl)amino]acetic Acid Chelating Reagent. ACS Sustainable Chem. Eng. 2016, 4 (9), 4704−4709. (23) Sun, Z.; Cao, H.; Xiao, Y.; Sietsma, J.; Jin, W.; Agterhuis, H.; Yang, Y. Toward Sustainability for Recovery of Critical Metals from Electronic Waste: The Hydrochemistry Processes. ACS Sustainable Chem. Eng. 2017, 5 (1), 21−40. (24) Zeng, X.; Wang, F.; Sun, X.; Li, J. Recycling Indium from Scraped Glass of Liquid Crystal Display: Process Optimizing and Mechanism Exploring. ACS Sustainable Chem. Eng. 2015, 3 (7), 1306− 1312. (25) Guan, J.; Wang, S.; Ren, H.; Guo, Y.; Yuan, H.; Yan, X.; Guo, J.; Gu, W.; Su, R.; Liang, B.; Gao, G.; Zhou, Y.; Xu, J.; Guo, Z. Indium recovery from waste liquid crystal displays by polyvinyl chloride waste. RSC Adv. 2015, 5 (124), 102836−102843. (26) Park, S.; Kim, S.; Han, Y.; Park, J. Apparatus for electronic component disassembly from printed circuit board assembly in ewastes. Int. J. Miner. Process. 2015, 144, 11−15. (27) Duan, H.; Hou, K.; Li, J.; Zhu, X. Examining the technology acceptance for dismantling of waste printed circuit boards in light of recycling and environmental concerns. J. Environ. Manage. 2011, 92 (3), 392−399. (28) Zhou, Y.; Qiu, K. A new technology for recycling materials from waste printed circuit boards. J. Hazard. Mater. 2010, 175 (1−3), 823− 828. (29) Wang, J.; Xu, Z. Disposing and Recycling Waste Printed Circuit Boards: Disconnecting, Resource Recovery, and Pollution Control. Environ. Sci. Technol. 2015, 49 (2), 721−733. (30) Lee, J.; Kim, Y.; Lee, J.-c. Disassembly and physical separation of electric/electronic components layered in printed circuit boards (PCB). J. Hazard. Mater. 2012, 241−242, 387−394. (31) Zeng, X.; Li, J.; Xie, H.; Liu, L. A novel dismantling process of waste printed circuit boards using water-soluble ionic liquid. Chemosphere 2013, 93 (7), 1288−1294. (32) Wang, J.; Guo, J.; Xu, Z. An environmentally friendly technology of disassembling electronic components from waste printed circuit boards. Waste Manage. 2016, 53, 218−224. (33) Yang, J.; Lei, J.; Peng, S.; Lv, Y.; Shi, W. A new membrane electro-deposition based process for tin recovery from waste printed circuit boards. J. Hazard. Mater. 2016, 304, 409−416. (34) Zhang, X.; Guan, J.; Guo, Y.; Yan, X.; Yuan, H.; Xu, J.; Guo, J.; Zhou, Y.; Su, R.; Guo, Z. Selective Desoldering Separation of Tin− Lead Alloy for Dismantling of Electronic Components from Printed Circuit Boards. ACS Sustainable Chem. Eng. 2015, 3 (8), 1696−1700. (35) Zhang, X.; Guan, J.; Guo, Y.; Cao, Y.; Guo, J.; Yuan, H.; Su, R.; Liang, B.; Gao, G.; Zhou, Y.; Xu, J.; Guo, Z. Effective dismantling of waste printed circuit board assembly with methanesulfonic acid containing hydrogen peroxide. Environ. Prog. Sustainable Energy 2017, DOI: 10.1002/ep.12527.

Jinhui Li: 0000-0001-7819-478X Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS This work was supported by the National Key Technology R&D Program (2014BAC03B04). We also thank Dr. Xianlai Zeng and Prof. Ab Stevels for their valuable advice. We are also very grateful to Dr. Abhishek Kumar Awasthi for reviewing the grammar of the manuscript.

■

REFERENCES

(1) Dodson, J. R.; Parker, H. L.; Garcia, A. M.; Hicken, A.; Asemave, K.; Farmer, T. J.; He, H.; Clark, J. H.; Hunt, A. J. Bio-derived materials as a green route for precious & critical metal recovery and re-use. Green Chem. 2015, 17 (4), 1951−1965. (2) Clark, J. H.; Farmer, T. J.; Herrero-Davila, L.; Sherwood, J. Circular economy design considerations for research and process development in the chemical sciences. Green Chem. 2016, 18 (14), 3914−3934. (3) Dodson, J. R.; Hunt, A. J.; Parker, H. L.; Yang, Y.; Clark, J. H. Elemental sustainability: Towards the total recovery of scarce metals. Chem. Eng. Process. 2012, 51, 69−78. (4) Hunt, A. J.; Matharu, A. S.; King, A. H.; Clark, J. H. The importance of elemental sustainability and critical element recovery. Green Chem. 2015, 17 (4), 1949−1950. (5) Alippi, C. A unique timely moment for embedding intelligence in applications. CAAI Trans. Intelligence Technol. 2016, 1 (1), 1−3. (6) Jin, H.; Chen, Q.; Chen, Z.; Hu, Y.; Zhang, J. Multi-LeapMotion sensor based demonstration for robotic refine tabletop object manipulation task. CAAI Trans. Intelligence Technol. 2016, 1 (1), 104−113. (7) Hadi, P.; Xu, M.; Lin, C. S. K.; Hui, C.-W.; McKay, G. Waste printed circuit board recycling techniques and product utilization. J. Hazard. Mater. 2015, 283, 234−243. (8) Zeng, X. L.; Gong, R. Y.; Chen, W. Q.; Li, J. H. Uncovering the Recycling Potential of ″New″ WEEE in China. Environ. Sci. Technol. 2016, 50 (3), 1347−1358. (9) Zeng, X.; Yang, C.; Chiang, J. F.; Li, J. Innovating e-waste management: From macroscopic to microscopic scales. Sci. Total Environ. 2017, 575, 1−5. (10) Chen, M.; Ogunseitan, O. A.; Wang, J.; Chen, H.; Wang, B.; Chen, S. Evolution of electronic waste toxicity: Trends in innovation and regulation. Environ. Int. 2016, 89−90, 147−154. (11) Yu, G.; Bu, Q.; Cao, Z.; Du, X.; Xia, J.; Wu, M.; Huang, J. Brominated flame retardants (BFRs): A review on environmental contamination in China. Chemosphere 2016, 150, 479−490. (12) Fu, J.; Zhang, A.; Wang, T.; Qu, G.; Shao, J.; Yuan, B.; Wang, Y.; Jiang, G. Influence of E-Waste Dismantling and Its Regulations: Temporal Trend, Spatial Distribution of Heavy Metals in Rice Grains, and Its Potential Health Risk. Environ. Sci. Technol. 2013, 47 (13), 7437−7445. (13) Zeng, X.; Xu, X.; Boezen, H. M.; Huo, X. Children with health impairments by heavy metals in an e-waste recycling area. Chemosphere 2016, 148, 408−415. (14) Awasthi, A. K.; Zeng, X.; Li, J. Environmental pollution of electronic waste recycling in India: A critical review. Environ. Pollut. 2016, 211, 259−270. (15) Li, J.; Zeng, X.; Chen, M.; Ogunseitan, O. A.; Stevels, A. ″Control-Alt-Delete″: Rebooting Solutions for the E-Waste Problem. Environ. Sci. Technol. 2015, 49 (12), 7095−7108. (16) Matus, K. J. M.; Clark, W. C.; Anastas, P. T.; Zimmerman, J. B. Barriers to the Implementation of Green Chemistry in the United States. Environ. Sci. Technol. 2012, 46 (20), 10892−10899. (17) Sheldon, R. A. Green chemistry and resource efficiency: towards a green economy. Green Chem. 2016, 18 (11), 3180−3183. 3532


Research Article

ACS Sustainable Chemistry & Engineering

(56) Chen, S.; Yang, Y.; Liu, C.; Dong, F.; Liu, B. Column bioleaching copper and its kinetics of waste printed circuit boards (WPCBs) by Acidithiobacillus ferrooxidans. Chemosphere 2015, 141, 162−168. (57) Liu, K.; Zhang, Z. Y.; Zhang, F. S. Direct extraction of palladium and silver from waste printed circuit boards powder by supercritical fluids oxidation-extraction process. J. Hazard. Mater. 2016, 318, 216− 223. (58) Calgaro, C. O.; Schlemmer, D. F.; da Silva, M. D. C. R.; Maziero, E. V.; Tanabe, E. H.; Bertuol, D. A. Fast copper extraction from printed circuit boards using supercritical carbon dioxide. Waste Manage. 2015, 45, 289−297. (59) Xiu, F. R.; Qi, Y. Y.; Zhang, F. S. Leaching of Au, Ag, and Pd from waste printed circuit boards of mobile phone by iodide lixiviant after supercritical water pre-treatment. Waste Manage. 2015, 41, 134− 141. (60) Neto, I. F. F.; Sousa, C. A.; Brito, M. S. C. A.; Futuro, A. M.; Soares, H. M. V. M. A simple and nearly-closed cycle process for recycling copper with high purity from end life printed circuit boards. Sep. Purif. Technol. 2016, 164, 19−27. (61) Fogarasi, S.; Imre-Lucaci, F.; Imre-Lucaci, Á .; Ilea, P. Copper recovery and gold enrichment from waste printed circuit boards by mediated electrochemical oxidation. J. Hazard. Mater. 2014, 273, 215− 221. (62) Fogarasi, S.; Imre-Lucaci, F.; Egedy, A.; Imre-Lucaci, Á .; Ilea, P. Eco-friendly copper recovery process from waste printed circuit boards using Fe3+/Fe2+ redox system. Waste Manage. 2015, 40, 136−143. (63) Silva-Martinez, S.; Roy, S. Copper recovery from tin stripping solution: Galvanostatic deposition in a batch-recycle system. Sep. Purif. Technol. 2013, 118, 6−12. (64) Lee, M.-S.; Ahn, J.-G.; Ahn, J.-W. Recovery of copper, tin and lead from the spent nitric etching solutions of printed circuit board and regeneration of the etching solution. Hydrometallurgy 2003, 70 (1−3), 23−29. (65) Ahn, J. W.; Ryu, S. H.; Kim, T. Y. Recovery of Tin and Nitric Acid from Spent Solder Stripping Solutions. J. Korean Inst. Met. Mater. 2015, 53 (6), 426−431. (66) Buckle, R.; Roy, S. The recovery of copper and tin from waste tin stripping solution. Part I. Thermodynamic analysis. Sep. Purif. Technol. 2008, 62 (1), 86−96. (67) Scott, K.; Chen, X.; Atkinson, J. W.; Todd, M.; Armstrong, R. D. Electrochemical recycling of tin, lead and copper from stripping solution in the manufacture of circuit boards. Resour. Conserv. Recycl. 1997, 20 (1), 43−55. (68) Roy, S.; Buckle, R. The recovery of copper and tin from waste tin stripping solution Part II: Kinetic analysis of synthetic and real process waste. Sep. Purif. Technol. 2009, 68 (2), 185−192. (69) Keskitalo, T.; Tanskanen, J.; Kuokkanen, T. Analysis of key patents of the regeneration of acidic cupric chloride etchant waste and tin stripping waste. Resour. Conserv. Recycl. 2007, 49 (3), 217−243. (70) Farley, K. J.; Dzombak, D. A.; Morel, F. M. M. A surface precipitation model for the sorption of cations on metal oxides. J. Colloid Interface Sci. 1985, 106 (1), 226−242. (71) Giannopoulou, I.; Panias, D. Differential precipitation of copper and nickel from acidic polymetallic aqueous solutions. Hydrometallurgy 2008, 90 (2−4), 137−146. (72) Kratohvil, S.; Matijevic, E. Preparation of copper compounds of different compositions and particle morphologies. J. Mater. Res. 1991, 6 (4), 766−777. (73) Weiser, H. B.; Milligan, W. O.; Cook, E. L. Hydrous cupric hydroxide and basic cupric sulfates. J. Am. Chem. Soc. 1942, 64, 503− 508. (74) Yoder, C. H.; Agee, T. M.; Ginion, K. E.; Hofmann, A. E.; Ewanichak, J. E.; Schaeffer, C. D.; Carroll, M. J.; Schaeffer, R. W.; McCaffrey, P. F. The relative stabilities of the copper hydroxyl sulphates. Mineral. Mag. 2007, 71 (5), 571−577. (75) Zittlau, A. H.; Shi, Q.; Boerio-Goates, J.; Woodfield, B. F.; Majzlan, J. Thermodynamics of the basic copper sulfates antlerite, posnjakite, and brochantite. Chem. Erde 2013, 73 (1), 39−50.

(36) Hou, S. B.; Wu, J. A.; Qin, Y. F.; Xu, Z. M. Electrostatic Separation for Recycling Waste Printed Circuit Board: A Study on External Factor and a Robust Design for Optimization. Environ. Sci. Technol. 2010, 44 (13), 5177−5181. (37) Wu, J.; Li, J.; Xu, Z. M. Electrostatic separation for recovering metals and nonmetals from waste printed circuit board: Problems and improvements. Environ. Sci. Technol. 2008, 42 (14), 5272−5276. (38) Li, J.; Xu, Z. M. Environmental Friendly Automatic Line for Recovering Metal from Waste Printed Circuit Boards. Environ. Sci. Technol. 2010, 44 (4), 1418−1423. (39) Li, J.; Lu, H.; Guo, J.; Xu, Z.; Zhou, Y. Recycle Technology for Recovering Resources and Products from Waste Printed Circuit Boards. Environ. Sci. Technol. 2007, 41 (6), 1995−2000. (40) Sarvar, M.; Salarirad, M. M.; Shabani, M. A. Characterization and mechanical separation of metals from computer Printed Circuit Boards (PCBs) based on mineral processing methods. Waste Manage. 2015, 45, 246−257. (41) Estrada-Ruiz, R. H.; Flores-Campos, R.; Gámez-Altamirano, H. A.; Velarde-Sánchez, E. J. Separation of the metallic and non-metallic fraction from printed circuit boards employing green technology. J. Hazard. Mater. 2016, 311, 91−99. (42) Xue, M.; Xu, Z. Computer Simulation of the Pneumatic Separator in the Pneumatic-Electrostatic Separation System for Recycling Waste Printed Circuit Boards with Electronic Components. Environ. Sci. Technol. 2013, 47 (9), 4598−4604. (43) Zhan, L.; Xu, Z. M. Application of Vacuum Metallurgy to Separate Pure Metal from Mixed Metallic Particles of Crushed Waste Printed Circuit Board Scraps. Environ. Sci. Technol. 2008, 42 (20), 7676−7681. (44) Zhan, L.; Xiang, X.; Xie, B.; Sun, J. A novel method of preparing highly dispersed spherical lead nanoparticles from solders of waste printed circuit boards. Chem. Eng. J. 2016, 303, 261−267. (45) Gao, Y.; Li, X.; Ding, H. Layer modeling of zinc removal from metallic mixture of waste printed circuit boards by vacuum distillation. Waste Manage. 2015, 42, 188−195. (46) Zhan, L.; Xu, Z. M. Separating and Recovering Pb from CopperRich Particles of Crushed Waste Printed Circuit Boards by Evaporation and Condensation. Environ. Sci. Technol. 2011, 45 (12), 5359−5365. (47) Chen, M. J.; Huang, J. X.; Ogunseitan, O. A.; Zhu, N. M.; Wang, Y. M. Comparative study on copper leaching from waste printed circuit boards by typical ionic liquid acids. Waste Manage. 2015, 41, 142−147. (48) Jadhav, U.; Hocheng, H. Hydrometallurgical Recovery of Metals from Large Printed Circuit Board Pieces. Sci. Rep. 2015, 5, 14574. (49) Chen, M.; Zhang, S.; Huang, J.; Chen, H. Lead during the leaching process of copper from waste printed circuit boards by five typical ionic liquid acids. J. Cleaner Prod. 2015, 95, 142−147. (50) Ou, Z.; Li, J. Synergism of mechanical activation and sulfurization to recover copper from waste printed circuit boards. RSC Adv. 2014, 4 (94), 51970−51976. (51) Serpe, A.; Rigoldi, A.; Marras, C.; Artizzu, F.; Laura Mercuri, M.; Deplano, P. Chameleon behaviour of iodine in recovering noblemetals from WEEE: towards sustainability and ″zero″ waste. Green Chem. 2015, 17 (4), 2208−2216. (52) Rodrigues, M. L. M.; Leão, V. A.; Gomes, O.; Lambert, F.; Bastin, D.; Gaydardzhiev, S. Copper extraction from coarsely ground printed circuit boards using moderate thermophilic bacteria in a rotating-drum reactor. Waste Manage. 2015, 41, 148−158. (53) Arshadi, M.; Mousavi, S. M. Enhancement of simultaneous gold and copper extraction from computer printed circuit boards using Bacillus megaterium. Bioresour. Technol. 2015, 175, 315−324. (54) Jadhav, U.; Su, C.; Hocheng, H. Leaching of metals from printed circuit board powder by an Aspergillus niger culture supernatant and hydrogen peroxide. RSC Adv. 2016, 6 (49), 43442−43452. (55) Arshadi, M.; Mousavi, S. M. Simultaneous recovery of Ni and Cu from computer-printed circuit boards using bioleaching: Statistical evaluation and optimization. Bioresour. Technol. 2014, 174, 233−242. 3533


Research Article

ACS Sustainable Chemistry & Engineering (76) Tanaka, H.; Koga, N. The thermal decomposition of basic copper(II) sulfate: An undergraduate thermal analysis experiment. J. Chem. Educ. 1990, 67 (7), 612−614. (77) Candal, R. J.; Regazzoni, A. E.; Blesa, M. A. Precipitation of copper(II) hydrous oxides and copper(II) basic salts. J. Mater. Chem. 1992, 2 (6), 657−661. (78) Speight, J. G. Lange’s Handbook of Chemistry, 16th ed.; McGrawHill Education: New York, 2005. (79) Yoder, C. H.; Bushong, E.; Liu, X.; Weidner, V.; McWilliams, P.; Martin, K.; Lorgunpai, J.; Haller, J.; Schaeffer, R. W. The synthesis and solubility of the copper hydroxyl nitrates: gerhardtite, rouaite and likasite. Mineral. Mag. 2010, 74 (3), 433−440. (80) Meyn, M.; Beneke, K.; Lagaly, G. Anion-exchange reactions of hydroxy double salts. Inorg. Chem. 1993, 32 (7), 1209−1215. (81) Newman, S. P.; Jones, W. Comparative study of some layered hydroxide salts containing exchangeable interlayer anions. J. Solid State Chem. 1999, 148 (1), 26−40. (82) Biswick, T.; Jones, W.; Pacula, A.; Serwicka, E. Synthesis, characterisation and anion exchange properties of copper, magnesium, zinc and nickel hydroxy nitrates. J. Solid State Chem. 2006, 179 (1), 49−55. (83) Park, S. H.; Lee, C. E. Layered copper hydroxide nalkylsulfonate salts: Synthesis, characterization, and magnetic behaviors in relation to the basal spacing. J. Phys. Chem. B 2005, 109 (3), 1118− 1124. (84) Jimenezlopez, A.; Rodriguezcastellon, E.; Oliverapastor, P.; Mairelestorres, P.; Tomlinson, A. A. G.; Jones, D. J.; Roziere, J. Layered Basic Copper Anion Exchangers: Chemical Characterisation and X-Ray Absorption Study. J. Mater. Chem. 1993, 3 (3), 303−307. (85) Stanimirova, T.; Dencheva, S.; Kirov, G. Structural interpretation of anion exchange in divalent copper hydroxysalt minerals. Clay Miner. 2013, 48 (1), 21−36.

3534
