Recycling Tin from Electronic Waste: A Problem That Needs More

Subscriber access provided by FLORIDA ATLANTIC UNIV

Perspective

Recycling Tin from E-waste: A Problem That Needs More Attention Congren Yang, Quanyin Tan, Lili Liu, Qingyin Dong, and Jinhui Li ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.7b02903 • Publication Date (Web): 13 Sep 2017 Downloaded from http://pubs.acs.org on September 18, 2017

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

ACS Sustainable Chemistry & Engineering is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 47

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Sustainable Chemistry & Engineering

Recycling Tin from E-waste: A Problem That Needs More Attention

Congren Yang,† Quanyin Tan,† Lili Liu,‡ Qingyin Dong,‡ Jinhui Li*, †

†

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

Mailing address: Congren Yang: Room 825, Sino-Italian Environmental and Energy-efficient Building, School of Environment,

Tsinghua

University,

Haidian

District,

Beijing

100084,

China

([email protected]) Quanyin Tan: Room 825, Sino-Italian Environmental and Energy-efficient Building, School of Environment,

Tsinghua

University,

Haidian

District,

Beijing

100084,

China

([email protected]) Lili Liu: Room 805, Sino-Italian Environmental and Energy-efficient Building, School of Environment,

Tsinghua

University,

Haidian

District,

Beijing

100084,

China

([email protected]) Qingyin Dong: Room 805, Sino-Italian Environmental and Energy-efficient Building, School of Environment,

Tsinghua

University,

Haidian

District,

Beijing

100084,

China

([email protected]) 1 ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 47

Jinhui Li: Room 804, Sino-Italian Environmental and Energy-efficient Building, School of Environment,

Tsinghua

University,

Haidian

District,

Beijing

100084,

China

([email protected])

* Corresponding Author Mailing address: Room 804, 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.

2 ACS Paragon Plus Environment

Page 3 of 47

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


ABSTRACT The rapid generation of e-waste has become a global problem owing to its potential environmental pollution and human-health risk, especially from informal recycling in developing countries. In 2014, however, only about 15.5% of the total global e-waste was formally treated by national take-back programs. Waste printed circuit boards (PCBs) are an integral part of e-waste, and they contain many valuable metal resources. Most recycling from waste PCBs has focused on metals like Au, PGMs (platinum group metals), and Cu, which have high economic value, but tin also makes up a large proportion of the metal in waste PCBs. Over the last decade, about 44% of the refined tin has been used as solder in the electronics industry each year. Although current global tin reserves can meet the short-term demand, for long-term sustainable development, recycling tin from secondary resources, especially from e-waste, is essential. In order to address the shortage of mineral resources and conserve energy, tin recycling from e-waste needs more attention.

Keywords: E-waste, Waste PCBs, Tin, Recycling, Sustainability



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 47

INTRODUCTION Waste electrical and electronic equipment (WEEE or e-waste) is a rapidly increasing waste stream, and coping with it is a complex problem. The worldwide amount of e-waste generation was estimated to be about 45.7 million tons (Mt) in 2016, and is expected to be 49.8 Mt by 2018. China is the largest producer of e-waste, and its e-waste generation was estimated to be about 10.4 Mt in 2016, and is expected to be 12.9 Mt by 2018

1-3

. E-waste contains not only a

significant amount of valuable metals (e.g., Cu, Fe, Al, Au, Ag, Pd), but also many hazardous substances [e.g., Pb, Cr, Cd, polybrominated diphenyl ethers (PBDEs), polybrominated biphenyls (PBBs)]

4-6

. The rapid generation of e-waste has become a global issue owing to its

potential for environmental pollution and human-health risks, especially when it is informally recycled in developing countries

7-10

. Over the past several decades, informal recycling

techniques like simple heating, open burning, and leaching with aqua regia, have caused serious environmental and human-health problems

11-13

. In an attempt to solve the e-waste problem,

many countries and regions, such as the European Union (EU), China, Japan, and South Korea, have established a series of legislations and regulations 1, 14-16. Waste printed circuit boards (PCBs) are an integral part of e-waste (about 4 wt.% of e-waste) 17, 18

. Formally recycling metals from waste PCBs will not only address the shortage of mineral

resources but also reduce environmental pollution and human-health risks. Therefore, many environmentally sound processes have been developed for recovering valuable metals from waste PCBs: for example, physical separation based on differences in electrical 22-24

properties, froth flotation based on differences in surface properties

23, 25

19-21

and density

, pyrometallurgy 26, 4

ACS Paragon Plus Environment

Page 5 of 47

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


27

, hydrometallurgy 28-31, bio-hydrometallurgy 32-35, and supercritical fluid 36-38. De-soldering and

removing ECs was the first step in recovering valuable metals from waste PCBs 39. Tin is an essential metal for the electronics industry. During PCB manufacturing, tin solder is plated onto the copper surface as an etch resistant, and electronic components (ECs) like chips, resistors, capacitors, expansion slots, etc., are mounted onto the surface of the PCBs with tin solder. In this study, we investigated world reserves, mining production, smelter production, and commercial applications of tin, summarized the various technologies available for the recovery of tin from waste PCBs, and analyzed the current status of recycling tin from e-waste.

GLOBAL TIN RESERVES, PRODUCTION AND APPLICATION Global tin reserves declined from 6,100,000 tons in 2005 to 4,700,000 tons in 2016 (Figure 1A). Estimated tin reserves have remained at about 4,800,000 tons over last five years, even though about 266,000 tons are mined per year; reserves amounts are dynamic because although they may be reduced as ore is mined, they may also be increased as new deposits are discovered, or as economic variables and/or new technology improve the economic feasibility of further exploiting current deposits. In 2016, the majority of tin reserves were in China (24%), Indonesia (17%), Brazil (15%), Bolivia (9%), Australia (8%), and Russia (7%). Global tin mine production reached peak value (more than 301,000 tons) in 2007 (Figure 1B). Production was 280,000 tons in 2016; China was the leading producer (36% of world output), followed by Indonesia (20%), Burma (12%), Brazil (9%), Bolivia (7%), and Peru (6%) (Figure 1B).



7000

350

A

6000

B

300

Australia Bolivia Brazil Burma China Indonesia Malaysia Peru Russia Thailand Other countries

5000

4000

3000

2000

1000

0

Tin mine production (Thousand tons)

Reserves (Thousand tons)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 6 of 47

Australia Bolivia Brazil Burma China Indonesia Malaysia Peru Russia Thailand Other countries

250

200

150

100

50

0

2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016

2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016

Years

Years

Figure 1. World tin reserves (A) and mine production (B). Data sources: Reserves: USGS (United States Geological Survey) 40; Mine production: USGS 40, 41.

There are about 23 different types of naturally occurring tin minerals, but only cassiterite is economically feasible to mine and recover. The grade of tin in ore is about 0.2−1.5% 42-45. While the content of tin in waste PCBs is about 1−6%, the average value is about 4% 44-47. Cassiterite is concentrated from tin ore using jigs, spirals, shaking tables, centrifugal concentrators, and froth flotation. About 50–60% of cassiterite is recovered using gravity concentration is. The fine particles are lost in the gravity tailings, but these can be recovered with centrifugal concentrators and froth flotation. The overall recovery rate of cassiterite is over 80%

42, 43, 48

. Metallic tin is

obtained from cassiterite concentrate via smelting (using ausmelt furnace, reverberatory furnace, electric furnace, etc.) followed by refining (using pyrometallurgy, electrolysis, etc.)

49

. The

flowsheet of the recovery process of tin from ore is shown in Figure 2.


Page 7 of 47

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 2. Process of recovering tin from ore.

Figure 3 shows the applications of refined tin, worldwide. Global refined tin use reached peak value (about 372,700 tons) in 2007. Most refined tin is used for solders in electronics (44.1%); solders in industrial applications (8.8%); tin platings (16.4%); chemicals (13.9%); brass & bronze (5.5%); and float glass (2.1%). Refined tin use in 2010 was similar to that in 2007. In 2014, global refined tin use was estimated to be 358,500 tons, distributed thus: solders-electronic (43.5%); solders-industrial (8%); tin platings (14.7%); chemicals (15.5%); lead acid batteries (7.3%); brass & bronze (5.2%); and float glass (2%). Sn-Pb solder (such as 63Sn-37Pb solder) 7 ACS Paragon Plus Environment


has been used extensively in the electronics industry. However, lead is restricted for use in electrical and electronic equipment by legislations and regulations like Restriction of the use of certain hazardous substances in electrical and electronic equipment, Ordinance on Management of Prevention and Control of Pollution from Electronic and Information Products 14, 50, because it is harmful to the environment and human health

51-54

. Lead-free solders, such as Sn-Cu, Sn-Ag,

and Sn-Ag-Cu alloys, have therefore been developed 55. 400

Solders Brass & Bronze

Tin platings Float glass

Chemicals Others

350

Tin use (Thousand tons)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 8 of 47

Solders-electronic 16.4%

300

13.9%

8.8%

250

Solders-industrial 5.5% 2.1%

200

Tin platings Chemicals

150

9.2% 100

Brass & Bronze Float glass

44.1%

50

Others

2007

0 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016

Years

Solders-electronic

Solders-electronic 16.2%

14.8%

15.5%

14.7%

Solders-industrial

Solders-industrial 7.3%

9.1%

5.2% 2%

Tin platings

4.8%

5.2%

Chemicals 9%

2% 7%

Brass & Bronze Float glass 43.5%

43.7%

Chemicals Lead acid batteries Brass and Bronze Float glass

Others

2010

Tin platings

2014

Others

Figure 3. Applications of refined tin, worldwide. Data sources: ITRI (International Tin Research Institute) 56-58.


Page 9 of 47

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


RECYCLING TIN FROM WASTE PCBS Overall energy consumption can be reduced by recycling metal from end-of-life products (Table 1) 59-63. For example, the electricity consumption for aluminum production from bauxite is almost 35 times higher than the consumption for recycling aluminum from end-of-life products, and the fuel consumption is more than 2.5 times higher

64

. Furthermore, recycling metal from

waste can significantly reduce the mine production. In 2016, the metallic lead production and usage was 11,144,000 and 11,121,000 tons, respectively; but only 4,721,000 tons of lead were mined 65. About 44% of refined tin has been used as solder in electronics manufacturing, over the last decade. Thus, recycling tin from e-waste is necessary for both the sustainable development of the electrical and electronics industry and for reduced of energy consumption. Table 1. Recycled metals energy savings over ore 66, 67 Metals Cu Pb Zn Al Fe

Energy savings (%) 85 65 60 95 74

Waste PCBs are integral parts of e-waste, containing wire boards and electronic components (ECs). The ECs are mounted onto the surface of the PCBs with tin solder. The compositions and melting points of solders are shown in Table 2. Sn-Pb (63Sn-37Pb, 60Sn-40Pb), Sn-Cu (99.3Sn-0.7Cu), Sn-Ag (96.5Sn-3.5Ag), and Sn-Ag-Cu (95.5Sn-3.8Ag-0.7Cu, 95.5-4Ag-0.5Cu, 95.5Sn-3.9Ag-0.6Cu, 96.5Sn-3Ag-0.5Cu, 98.5Sn-1Ag-0.5Cu) solder are widely used in the



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 47

electronics industry; the melting points of these tin solders are in the range of 183 to 227°C. Table 2. Composition and melting points of various solders 55, 68-71 Alloy In-Bi-Sn In-Bi Bi-In-Sn Bi-In In-Sn Bi-Sn Sn-Bi-In Sn-Zn-In-Bi Sn-In-Ag Sn-In-Zn Sn-Pb Sn-Zn-Bi Sn-Zn Sn-In-Ag Sn-Ag-Bi Sn-Bi-Ag Sn-Ag-Bi Sn-Bi-Ag Sn-Ag-Cu-Sb Sn-Ag-Zn Sn-Ag-Cu

Sn-Au Sn-Ag Sn-Cu Sn-Sb Sn-Ag-Sb

Composition 51In-32.5Bi-16.5Sn 66.3In-33Bi 57Bi-26In-17Sn 54.02Bi-29.68In-16.3Sn 67Bi-33In 52In-48Sn 50In-50Sn 58Bi-42Sn 70Sn-20Bi-10In 86.5Sn-5.5Zn-4.5In-3.5Bi 77.2Sn-20In-2.8Ag 83.6Sn-8.8In-7.6Zn 63Sn-37Sn 60Sn-40Pb 89Sn-8Zn3Bi 91Sn-9Zn 86.9Sn-10In-3.1Ag 93.5Sn-3.5Ag-3Bi 95Sn-2Bi-3Ag 91.8Sn-3.4Ag-4.8Bi 91Sn-7.5Bi-2Ag 96.7Sn-2Ag-0.8Cu-0.5Sb 95.5Sn-3.5Ag-1Zn 95.5Sn-3.8Ag-0.7Cu 95.5Sn-4Ag-0.5Cu 95.5Sn-3.9Ag-0.6Cu 96.5Sn-3Ag-0.5Cu 93.6Sn-4.7Ag-1.7Cu 98.5Sn-1Ag-0.5Cu 90Sn-10Au 96.5Sn-3.5Ag 98Sn-2Ag 99.3Sn-0.7Cu 99Sn-1Sb 97Sn-3Sb 65Sn-25Ag-10Sb

Melting range (°C) 60 (eutectic) 72 (eutectic) 79 (eutectic) 81 (eutectic) 109 (eutectic) 118 (eutectic) 118-125 138 (eutectic) 143-193 174 175 181 183 (eutectic) 183 (near eutectic) 189-199 198.5 (eutectic) 204 206 210 211 212 216 217 217 (near eutectic) 217 217 217 217 217 217 221 (eutectic) 221-226 227 (eutectic) 232 232 233 10

ACS Paragon Plus Environment

Page 11 of 47

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Sn-Sb Au-Sn

95Sn-5Sb 80Au-20Sn

235 280 (eutectic)

Thermal treatment. In order to recover the tin solder and dismantle the ECs from waste PCBs, the waste PCBs should be heated to a temperature above the melting point of tin solder. Infrared heaters, electric heaters, and liquid-medium heating are the most commonly used for this purpose. A technique consisting of vacuum pyrolysis of waste PCBs, followed by centrifugal separation of solder, was proposed by Zhou et al.

72

. The waste PCBs were first pyrolyzed at

600°C for 30 min, and the pyrolysis oil and gas were obtained, which can be used as fuel or chemical feedstock after treatment. Then the solder was recovered via centrifugal separation when the pyrolysis residue was heated to 400°C under vacuum. These researchers also proposed another method for recovering solder: heating the waste PCBs to 240°C using diesel oil as a heating medium, then separating the solder via centrifuge 73. Park et al. 74 used an infra-red heater to heat waste PCBs to 250°C, and a maximum 94% of ECs were removed from the waste PCBs, but they did not mention the recovery of solder. Wang et al.

75

developed an automatic system at the pilot-scale, for disassembling waste PCBs and

recycling solder with heated air. The solder was completely removed from the waste PCBs at a temperature of 265 ± 5°C. Zeng et al.

39

used water-soluble ionic liquid [BMIm]BF4 (1-Butyl-3-methylimidazolium

tetrafluoroborate) as a heating medium to dismantle ECs and recover tin solder from waste PCBs;



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 47

nearly 90% of the ECs were removed from the waste PCBs at 250°C, and high-purity solder was obtained from the water-soluble ionic liquid. Simultaneously, the water-soluble ionic liquid can be reused. Moreover, only a minute amount of benzene and methylbenzene was generated during the disassembling process. A set of pilot equipment using water-soluble ionic liquid for dismantling waste PCBs was also designed. The equipment consisted of a waste PCBs feeding system, a water-soluble ionic liquid spraying system, a waste PCBs washing system, a water-soluble ionic liquid recycling system, a system for separating and collecting ECs and bare boards, and an air releasing system. The dismantling of waste PCBs using an ionic liquid of [EMIM]BF4 (1-ethyl-3-methylimizadolium tetrafluoroborate) was also investigated by Zhu et al. 76, 77

. The solder was removed at 240°C with a stirring speed of 150 rpm, with a desoldering time

of 10 min.

Hydrometallurgy. Hydrometallurgical technology is widely used to recover tin from waste PCBs, owing to its low operating temperature. HNO3 and HCl are most commonly used. Mecucci and Scott

78

achieved the recycling of Cu, Pb, and Sn from waste PCBs. The waste

PCBs were first crushed to 2.5 mm2, then the valuable metals—e.g. Cu, Pb, Sn, Zn, Ni—were leached from the crushed waste PCBs with HNO3. It is well established in the literature that Sn reacts with HNO3, which converts it into an insoluble SnO2 because hydrolysis of Sn4+ to Sn(OH)4 occurs very easily

79-81

. The SnO2 was then separated from the leaching solution via

filtration. The insoluble SnO2 was dissolved in 1.5 mol/L HCl followed by electrodeposition of Sn. Cu and Pb were also recycled using electrodeposition. In another study, essentially all of the 12 ACS Paragon Plus Environment

Page 13 of 47

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Pb was selectively leached from waste PCBs with 0.2 mol/L HNO3 at 90°C for 45 min, and then 98.74% of Sn was leached with 3.5 mol/L HCl at 90°C for 120 min 82. As the tin can be oxidized to Sn4+ by nitric acid, then which converts it into an insoluble SnO2, but the SnO2 can be dissolved in hydrochloric acid solution. Thus, Castro and Martins 83 used a solution consisting of 3.0 mol/L HCl and 1.0 mol/L HNO3 to leach Sn and Cu from waste PCBs powder, and the Sn and Cu extraction percentages were 98% and 93%, respectively. Finally, 85.8% of Sn and 34.3% of Cu were recovered by neutralizing the leaching solution using NaOH via precipitation. In a 1 mol/L HCl solution, about 90% of Sn was leached out from the waste PCBs with a particle size of −3 mm at 80°C 84, 85. Moreover, the waste PCBs with a particle size of −8 mm were first pyrolysed at 900°C under nitrogen atmosphere, followed by leaching of Sn from pyrolysed sample was investigated in a 1 mol/L HCl solution at 80°C. Nearly 95% of Sn was leached out 85. Zhang et al. 86 reported a selective dissolution of tin−lead solder from waste PCBs. Almost 100% of the solder was dissolved selectively with 2.5 mol/L of HBF4 and 0.4 mol/L of H2O2 at 20 °C. The standard electrode potentials of H2O2, Sn, and Pb are 1.776, −0.136 and −0.126 V, respectively (Eqs. 1−3). The differences of the standard electrode potentials, between H2O2 and Sn, H2O2 and Pb, are 1.912 and 1.902 V, respectively (Eqs. 4−5). Thus Sn and Pb can be oxidized by H2O2 at room temperature. For Cu, the standard electrode potential is 0.337 V (Eq. 6). The Cu can also be oxidized by H2O2 at room temperature, because the difference in the standard electrode potential between H2O2 and Cu is 1.439 V (Eq. 7). Actually, however, very little Cu was leached out, for two reasons: galvanic corrosion, and the displacement reaction 13 ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 14 of 47

between Cu2+ and both Sn and Pb. In the galvanic corrosion process, the metal with the higher electrode potential acts as a cathode, while the metal with the lower electrode potential acts as an anode. Therefore, the dissolution rate of the metal with the lower potential (anode) increases, but the dissolution rate of the metal with the higher potential (cathode) decreases

87

. As for the

displacement reactions between Cu2+, and Sn or Pb (Eqs. 8-9), the standard electrode potential of Cu is far less than that of either Sn or Pb. Nevertheless, the tin−lead solder can be dissolved selectively with 3.5 mol/L of methanesulfonic acid (MSA) and 0.5 mol/L of H2O2 88.

H 2 O2 +2H + +2e− =2H 2O ϕ10 =+1.776 V

(1)

Sn 2+ +2e− =Sn ϕ20 = − 0.136 V

(2)

Pb2+ +2e− =Pb ϕ30 = − 0.126 V

(3)

H 2 O2 +Sn+2H + =Sn 2+ +2H 2 O ∆ϕ1 =+1.912 V

(4)

H 2 O2 +Pb+2H + =Pb2+ +2H 2 O ∆ϕ2 =+1.902 V

(5)

Cu 2+ +2e − =Cu ϕ40 =+0.337 V

(6)

H2 O2 +Cu+2H+ =Cu 2+ +2H2 O ∆ϕ3 =+1.439 V

(7)

Sn+Cu 2+ =Sn 2+ +Cu

(8)

Pb+Cu 2+ =Pb2+ +Cu

(9)

Yang et al.

89

proposed a closed-loop process for recycling tin from multi-metal powder

originating from waste PCBs. The results showed that 99% of the tin was leached out with SnCl4 and HCl at 60 to 90°C, and the tin was then recovered from the purified solution by electro-deposition. During the leaching process, Sn was oxidized by SnCl4, according to Eq. 10. The leachate was purified to remove impurities such as Cu2+ and Pb2+, for electrowinning. 14 ACS Paragon Plus Environment

Page 15 of 47

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


During the electrowinning process, Sn2+ in the purified solution was reduced to Sn at the cathode (Eq. 2). Simultaneously, H+ was reduced to H2 at the cathode (Eq. 11), casing a decrease of current efficiency. At the anode, Sn2+ was oxidized to Sn4+ (Eq. 12), while Cl−—a toxic and environmentally dangerous gas—may have been oxidized to Cl2 (Eq. 13). After electrowinning, the anode and cathode waste solution was reused for leaching tin from the multi-metal powders.

Sn+SnCl4 =2SnCl2

(10)

2H+ +2e− =H 2 ↑

(11)

Sn 2+ =Sn 4+ +2e −

(12)

2Cl− =Cl2 ↑ +2e−

(13)

Tin stripping is one of the key processes of PCB manufacturing. During the production of PCBs, a large volume of spent tin stripping solution (spent TSS), containing ~5% Sn with ~6 g/L Cu, ~10 g/L Fe, and ~4 mol/L HNO3, is produced. Most of the Sn in the spent TSS presents as insoluble hydrated SnO2. Currently, valuable metal in spent TSS is usually recycled via neutralization-precipitation with NaOH, but a large amount of NaOH is consumed because of its high nitric acid concentration. Nevertheless, many environmentally sound processes for recycling HNO3 and metals have been developed

90-95

. Recently, a novel technique for

coprocessing waste PCBs and spent TSS at room temperature was developed by Yang et al.

81

.

Approximately 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 hours. About 99% of the Sn, Pb, Fe, Cu and Zn were recovered from the leaching solution by step precipitation, in the following order: Sn→Pb→Fe→Cu→Zn. At the same time, more than 87% of the ECs were removed from the 15 ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 16 of 47

waste PCBs. This proposed environmentally friendly process has substantial advantages over traditional recovery methods of heating waste PCBs, in terms of both material recovery and energy efficiency.

Other methods. Estrada-Ruiz et al. 25 developed a technology for separating of the metallic and non-metallic fractions from waste PCBs. The waste PCBs were first crushed to −250 µm. The metallic fraction was then separated from the non-metallic portion by froth flotation using a flotation column with a superficial air velocity of 0.4 cm/s, taking advantage of the difference in surface properties between the non-metals and metals: the non-metallic portion is hydrophobic while the metallic portion is hydrophilic. Hence, the metals were separated from the non-metallic portion, as concentrate and tailings, respectively. The metallic fraction consisted of 7.91% C, 12.27% O, 0.44% Al, 52.57% Sn, and 26.81% Pb. Mechanical–physical recycling processes have also been widely used to recycle metal from waste PCBs. The waste PCBs is first crushed, and then the metallic fraction is separated from the non-metallic portion by electrostatic separation, obtaining a product containing various metals (e.g., Cu, Pb, Sn, Zn). The pure metal can be separated from the mixed metallic particles with vacuum metallurgy 96. For example, Pb is first separated from Cu-rich particles containing Cu, Pb, and Sn at 1123 K under 0.1-1 Pa. Then an aggregate Cu-Sn intermetallic compound is formed during the separation of Pb from Cu-rich particles using vacuum metallurgy. The aggregate Sn-rich materials are then further separated from Cu particles by sieving 97.


Page 17 of 47

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Environmental impact. Various technologies for recycling tin from waste PCBs are summarized in Table 3. Heating is the most effective way to disassemble waste PCBs and recover solder. The melting points of tin solders are in the range of 183 to 280°C. The recovered solder is a good resource of tin for refining. However, several studies have indicated that PCDD/Fs (polychlorinated dibenzo-p-dioxin and dibenzofurans) and PBDD/Fs (polybrominated dibenzo-pdioxin and dibenzofurans) are formed during the thermal processing of waste PCBs at temperatures between 250 and 400°C

98, 99

. Heavy metals (e.g., Cu, Pb, Cd, Cr) and persistent

organic pollutants (POPs) have been found in e-waste recycling site 9, 100-102. Therefore, pollution control technology also needs to be developed. Hydrometallurgical technology is therefore widely used to recover tin from waste PCBs, because of the low operating temperature. However, a lot of pollutants like NOx, HCl, Cl2, etc., could be released into the environment, a large volume of heavy metal wastewater will also be produced. Like the thermal treatment, pollution control technology needs to be developed too, but there are few studies on the pollutants release and control in the process of hydrometallurgy. Furthermore, coprocessing hazardous waste may be a good way to disassemble waste PCBs and recycle valuable metals. Recently, hazardous wastes have been coprocessed in cement kilns at the industrial scale, and coprocessing methods have also been developed for CRT funnel glass and lead concentrates 103, 104.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48

Page 18 of 47

Table 3. Summary of various technologies for recycling tin from waste PCBs Technological process Thermal treatment 1. Vacuum pyrolysis of waste PCBs at 600°C (30 min) → Heating pyrolysis residue to 400°C (vacuum) → Centrifugal separation of solder (1200 rpm, 10 min)

Products

Tin recovery

Environmental impact High energy consumption, heavy metals, POPs High energy consumption, heavy metals, POPs High energy consumption, heavy metals, POPs High energy consumption, heavy metals High energy consumption, heavy metals, organic pollutants High energy consumption, heavy metals, organic pollutants

Solder

*

2. Heating waste PCBs to 250°C with infra-red heater

Solder

**

3. Heating waste PCBs to 265 ± 5°C with heated air

Solder

*

4. Heating waste PCBs in diesel oil (240°C) → Centrifugal separation of solder (1400 rpm, 6 min)

Solder

*

5. Heating waste PCBs via [BMIm]BF4 (250°C, 45 rpm, 12 min) → Condensation → Solid-liquid separation → High-purity solder

Solder

**

6. Heating waste PCBs via [EMIM+][BF4−] (240°C, 150 rpm, 10 min) → Condensation → Solid-liquid separation → Solder

Solder

*

Hydrometallurgy 7. Leaching solder with 2 mol/L HNO3 → Dissolution of SnO2 precipitate with 1.5 mol/L HCl → Electrodeposition 8. Selectively leaching Pb with 0.2 mol/L HNO3 (90°C,

Metallic tin

/

NOx, HCl, Cl2, heavy metal wastewater

/

98.74%

NOx, HCl, heavy metal

References

72

74

75

73

39

76, 77

78

82


Page 19 of 47

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48


45 min) → Leaching Sn with 3.5 mol/L HCl (90°C, 120 min) 9. Leaching waste PCBs powder with 3.0 mol/L HCl + SnO2 precipitate 1.0 mol/L HNO3 → Precipitation 10. Leaching tin from waste PCBs (−3 mm) with 1 mol/L / HCl (80°C, 180 min)

wastewater 84.1%

11. Pyrolysis of waste PCBs (−8 mm) at 900°C → Leaching tin from pyrolysis residue with 1 mol/L HCl (80°C, 180 min)

~95%

~90%

/

12. Selectively leaching solder with 2.5 mol/L HBF4 and / 0.4 mol/L H2O2 (20 °C, 35 min) 13. Selectively leaching solder with 3.5 mol/L MSA and / 0.5 mol/L H2O2 (20 °C, 45 min) 14. Leaching tin with SnCl4 and HCl (60 to 90°C) Metallic tin →Purification→ Electrodeposition 15. Leaching waste PCBs with spent TSS (S/L=1:5~1:8, SnO2 precipitate 2 h) → Precipitation of Sn Crushing-Separation 16. Crushing → Flotation → Sn-rich products Sn-rich products 17. Crushing → Electrostatic separation → Mixed Sn-rich metallic particles → Vacuum metallurgy → Sn-rich materials materials

~100% ~100% 99% 86%~97%

NOx, HCl, heavy metal wastewater HCl, heavy metal wastewater High energy consumption, heavy metals, POPs, HCl, heavy metal wastewater Heavy metal wastewater Organic pollutants, heavy metal wastewater HCl, Cl2, heavy metal wastewater NOx, heavy metal wastewater

/

Wastewater

/

High energy consumption

83

84

85

86

88

89

81

25

96, 97

* The solder was completely separated. ** 90%~94% of the ECs were removed.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 47

TIN LONG-TERM SUSTAINABLE SUPPLY Waste PCBs are the most valuable part of e-waste; they contain a significant mass of valuable metals, accounting for about 40% of the metal recovery value of e-waste

18

. In 2014,

approximately 51% of the refined tin was used in the electronics industry and in lead acid batteries. The amount of tin in e-waste in 2014 was estimated at 35% of the mined metal in the same year 18. In 2016, world tin reserves and mine production were estimated at 4,700,000 and 280,000 tons, respectively 40. At these rates, current reserves of tin will be depleted in ~16 years. For long-term sustainable development, recycling tin from secondary sources will be essential. According to USGS statistics

41

, world tin smelter production increased from 344,000 tons in

2005 to 349,000 tons in 2015, with about 94% of these amounts produced by primary tin smelters (Figure 4A). The majority of primary tin smelters were in China, Indonesia, Peru, and Thailand (Figure 4B). Most of the secondary tin smelters were in the United States and Belgium. In the United States in 2015, about 12,000 tons of tin was recycled from old scrap—metal in products have reached their end-of-life manufacturing process

105, 106

105, 106

, and new scrap—originating from a fabrication or

(Figure 4C), accounting for about 30% of apparent consumption.

Most of the tin was recovered from old scrap at detinning plants and secondary nonferrous metal-processing plants

107

. ITRI survey results showed that, in recent years, the global refined

tin production was about 330,000 to 370,000 tons per year; the mine production was about 270,000 to 310,000 tons per year; the difference between the two filled by some 50,000 to 70,000 tons per year of secondary refined tin production 108. The proportion of secondary refined tin production is only about 17%. 20 ACS Paragon Plus Environment

Page 21 of 47

400

Primary Secondary

350

A

Primary

B

350

Tin smelter production (Thousand tons)

Tin smelter production (Thousand tons)

400

300 250 200 150 100 50 0 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015

Bolivia Brazil China Indonesia Malaysia Peru Thailand Other countries

300

250

200

150

100

50

0 2005

2006

2007

2008

2009

Years

2010

2011

2012

2013

2014

2015

Years

25

C

Secondary Tin smelter production (Thousand tons)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Australia Belgium Brazil Russia United States Other countries

20

15

10

5

0 2005

2006

2007

2008

2009

2010

2011

2012

2013

2014

2015

Years

Figure 4. World tin smelter production (A), primary tin smelter production (B) and secondary tin smelter production (C) (Data sources: USGS 41). According to Balde et al. 3, the worldwide amount of e-waste generation was about 41.8 Mt in 2014. The regions and countries with the highest e-waste generation were the European Union, China, United States, and Japan, where 11.6, 8.53, 7.1 and 2.2 Mt of e-waste were generated, respectively. At the same time, almost 50% of the e-waste generated by the developed countries was illegally exported to developing countries like China and India

63

. In the European Union,

about 40% of the e-waste was collected and treated by official take-back systems owing to a series of legislations and regulations, e.g. Directive on Waste Electrical and Electronic Equipment (WEEE directive) 1. Simultaneously, 8% (0.7Mt) of the total e-waste (such as phones, USB-sticks, lamps, etc.) was thrown into the waste bin. About 12% of the e-waste generated in 21 ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 47

the United States was collected by official take-back systems, but Namias

109

reported that the

United States did not process any of this e-waste: 50%-80% of it was illegally exported to developing countries such as China, India, and Pakistan, the remainder was processed via pyrometallurgical processing at copper smelters in Western Europe and Canada. About 24% of the e-waste generated in Japan was collected by official take-back systems. In China, about 28% of the e-waste generated was officially collected and treated; although there are a total of 109 formal e-waste dismantling enterprises in China, but informal collection and recycling of e-waste still play a major role. For some small equipment like waste mobile phones, the recycling rate is even lower 110, 111. Tan et al. 112 reported that less than 20% of the old mobile phones are collected, and more than half are stored in homes. In summary, only around 15.5% (about 6.5 Mt) of the e-waste generated at the global scale in 2014 was formally treated by national take-back programs. The economic value of Au, PGMs (platinum group metals), Cu, Sn, and Ag present in waste PCBs constitutes 59%, 15%, 15%, 7%, and 4% of their value, respectively

18

. Compared with

recycled Au, PGMs, and Cu from waste PCBs, the economic value of tin is lower 18, 112, 113. And recovering these more valuable metals from e-waste has had the highest priority, especially in informal recycling sector

112, 114

. Surprisingly, most of these metals in waste mobile

phones—such as Au (88-92%), Pd (88%), and Ag (89%)—are discarded

115, 116

. This disregard

for even the more valuable metals, combined with the comparatively lower value of tin, can explain the low rate of tin recycling from e-waste. Yet, as is clear from the recycling practices in the European Union, there is a proven benefit from recycling e-waste, given the sound 22 ACS Paragon Plus Environment

Page 23 of 47

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


legislations and regulations there 1, 14, 15. The effect of the e-waste collection rate by official take-back systems, on global tin long-term sustainable supply, was evaluated in this study, under the following assumptions: (1) the worldwide amount of e-waste generation was about 45.7 Mt in 2016, and the annual growth rate of e-waste was set to 4.5% based on Baldé et al. 3; (2) the e-waste collection rate (CR) by official take-back systems was set to 15.5%, 40%, 60%, 80%, and 100%; (3) the average weight of the waste PCBs in e-waste was 4%, and the average value of the tin content (CTin) in waste PCBs was 4%; (4) the tin recovery rate, also called the recycling process efficiency rate (RR), was set to 85%, based on Table 3; (5) world tin reserves were estimated at 4,700,000 tons in 2016, and the future global mine production was assumed to be 270,000 tons per year, based on the annual average values over the last decade (Figure 1B). The tin mine production can be reduced by recycling tin from waste PCBs. Based on the above hypotheses, the future global mine production per year (Qmine/year) can be estimated with the following equation: ( year − 2016) Q(year)(CR, CTin ) = 270, 000 − 45.7 ×1, 000, 000 ×（1+4.5%） × CR × 4% × CTin × 85% (tons)(14)

The cumulative tin mine production under different e-waste collection rate can be estimated with the following equation: year

∑ Q(year)

(CR,CTin )

≤ 4,700,000 (tons)

(15)

2016

The cumulative tin mine production amounts under different e-waste collection rate and contents of tin in waste PCBs are shown in Figure 5. The circulability (CM) defined by Sun et al. 117

was also presented in Figure 5. Where, CM=R/(R+M), R is the amount of tin recycling from 23 ACS Paragon Plus Environment


waste PCBs each year; M is the amount of tin mine production each year; and R+M equals to 270,000 tons per year. When CM =0, it indicates that the tin to meet the consumption demand is only supplied by mining; when CM =1, it indicates that the tin to meet the consumption demand is only supplied by recycling from waste PCBs. All the recycling scenarios showed that the recovery of tin from e-waste could significantly reduce the tin mine production and extend the service life of mine, especially when a large amount of e-waste was generated and high e-waste collection rate were achieved. Therefore, a proposed scenario for tin sustainable development is shown in Figure 6.

8000

A

1.0

CTin=4%

0.9

7000

0.8

6000

0.7

5000

Tin reserves

4000 3000

No tin recycling CR=15.5%, RR=85% CR=40%, RR=85% CR=60%, RR=85% CR=80%, RR=85% CR=100%, RR=85%

2000 1000 0 2015

2020

2025

2030

2035

2040

2045

Circulability

Cumulative mine production (Thousand tons)

9000

B

CTin=4% No tin recycling CR=15.5%, RR=85% CR=40%, RR=85% CR=60%, RR=85% CR=80%, RR=85% CR=100%, RR=85%

0.6 0.5 0.4 0.3 0.2 0.1 0.0 2015

2050

2020

2025

2030

9000

c

1.0

CR=80%, RR=85%

8000

0.9

7000

0.8

6000

0.7

Tin reserves

Circulability

5000 4000 3000

1000

0.1

2030

2050

2035

2040

2040

2045

2050

CR=80%, RR=85% No tin recycling CTin=2% CTin=4% CTin=6%

0.3 0.2

2025

2045

0.4

CTin=4%

2020

2040

0.5

No tin recycling CTin=2% CTin=6%

D

0.6

2000

0 2015

2035

Year

Year

Cumulative mine production (Thousand tons)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 24 of 47

0.0

2045

2050

2015

2020

2025

2030

2035

Year

Year

Figure 5. Cumulative tin mine production and circulability values for tin under different e-waste 24 ACS Paragon Plus Environment

Page 25 of 47

collection rate (A and B) and content of tin in waste PCBs (C and D).

Reducing the tin mine production Extending the service life of mine Cumulative mine production (Thousand tons)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


9000 8000 7000 6000 5000 4000

Tin reserves CTin=4%

3000

No tin recycling CR=80%, RR=85%

2000 1000 0

2015

2020

2025

2030

2035

2040

2045

2050

Year

Electric heating Heated air Ionic liquid heating Spent TSS, HNO3, HCl, H2O2

······ EEE

WEEE

Figure 6. The proposed scenario for tin sustainable development.

CONCLUSIONS AND PERSPECTIVES The rapid generation of e-waste has become a global problem owing to its potential for environmental pollution and human-health risks, especially when it is informally recycled in 25 ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 26 of 47

developing countries. Waste PCBs are an integral part of e-waste, and they contain many valuable metal resources. Throughout the last decade, about 44% of the refined tin has been used as solder in the electronics industry each year. In 2014, the amount of tin in e-waste was estimated to be about 35% of the amount of metal mined in that year. Current reserves of tin will be depleted in ~16 years. For long-term sustainable development, therefore, recycling tin from secondary sources (especially from e-waste) will be essential. Many environmentally sound processes have been developed, for recycling tin from waste PCBs. In actuality, however, the worldwide amount of e-waste generation was about 41.8 Mt in 2014, but only around 15.5% (about 6.5 Mt) of the e-waste generated at the global scale in 2014 was formally treated by national take-back programs. On the other hands, compared with Au, PGMs and Cu recycled from waste PCBs, the economic value of tin is low. These can explain the low tin recycling rate from e-waste. Nevertheless, there is a clear benefit to recycling e-waste, where there is a sound legislations and regulations system, as in the European Union, recovering tin from e-waste can significantly reduce the tin mine production and extend the service life of mines. Therefore, in order to address the shortage of mineral resources and conserve energy, a sound e-waste legislations and regulations must be established to improve the collection rate of e-waste by official take-back systems. Simultaneously, green technology for recycling of tin from e-waste needs to be developed. Recycling tin from e-waste will play a significant role in tin long-term sustainable development, but recycling tin will depend on the balance between the revenue of recycling tin from e-waste and the falling concentrations of tin found in end-of-life 26 ACS Paragon Plus Environment

Page 27 of 47

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


products as a result of development of science and technology.

AUTHOR INFORMATION Corresponding Author *

E-mail address: [email protected] (J.L.). Tel.: +86-10-62794143. Fax: +86-10-62772048.

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 Dr. Abhishek Kumar Awasthi for their valuable advice.

REFERENCES (1) 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. (2) Zeng, X.; Gong, R.; Chen, W.-Q.; Li, J., Uncovering the Recycling Potential of "New" WEEE in China. Environ. Sci. Technol. 2016, 50, (3), 1347-1358. (3) Baldé, C. P.; Wang, F.; Kuehr, R.; Huisman, J., The global e-waste monitor – 2014, United Nations University, IAS – SCYCLE, Bonn, Germany. 2015. (4) Chen, M.; Ogunseitan, O. A.; Wang, J.; Chen, H.; Wang, B.; Chen, S., Evolution of electronic 27 ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 28 of 47

waste toxicity: Trends in innovation and regulation. Environ. Int. 2016, 89–90, 147-154. (5) Zhang, L.; Xu, Z., A review of current progress of recycling technologies for metals from waste electrical and electronic equipment. J. Clean Prod. 2016, 127, 19-36. (6) Mengmeng Wang, Q. T., Joseph F. Chiang, Jinhui Li, Recovery of rare and precious metals from urban mines–A review. Front. Environ. Sci. Eng. 2017, 11, (5), 1. (7) 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. (8) 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. (9) Awasthi, A. K.; Zeng, X.; Li, J., Environmental pollution of electronic waste recycling in India: A critical review. Environ. Pollut. 2016, 211, 259-270. (10) Awasthi, A. K.; Zeng, X.; Li, J., Relationship between e-waste recycling and human health risk in India: a critical review. Environ. Sci. Pollut. Res. 2016, 23, (12), 11509-11532. (11) Wong, C. S. C.; Duzgoren-Aydin, N. S.; Aydin, A.; Wong, M. H., Evidence of excessive releases of metals from primitive e-waste processing in Guiyu, China. Environ. Pollut. 2007, 148, (1), 62-72. (12) Huang, K.; Guo, J.; Xu, Z., Recycling of waste printed circuit boards: A review of current technologies and treatment status in China. J. Hazard. Mater. 2009, 164, (2–3), 399-408. (13) 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. 28 ACS Paragon Plus Environment

Page 29 of 47

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(14) Zeng, X.; Li, J.; Stevels, A. L. N.; Liu, L., Perspective of electronic waste management in China based on a legislation comparison between China and the EU. J. Clean Prod. 2013, 51, 80-87. (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) Xiaolong Song, J. W., Jianxin Yang, Bin Lu, An updated review and conceptual model for optimizing WEEE management in China from a life cycle perspective. Front. Environ. Sci. Eng. 2017, 11, (5), 3. (17) Wang, J. B.; Xu, Z. M., Disposing and Recycling Waste Printed Circuit Boards: Disconnecting, Resource Recovery, and Pollution Control. Environ. Sci. Technol. 2015, 49, (2), 721-733. (18) Golev, A.; Schmeda-Lopez, D. R.; Smart, S. K.; Corder, G. D.; McFarland, E. W., Where next on e-waste in Australia? Waste Manage. 2016, 58, 348-358. (19) 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. (20) 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. (21) 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. 29 ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 30 of 47

(22) 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. (23) 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. (24) 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. (25) 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. (26) 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. (27) 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. (28) 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. (29) Jadhav, U.; Hocheng, H., Hydrometallurgical Recovery of Metals from Large Printed Circuit Board Pieces. Sci. Rep. 2015, 5, 14574. 30 ACS Paragon Plus Environment

Page 31 of 47

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(30) 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. (31) Serpe, A.; Rigoldi, A.; Marras, C.; Artizzu, F.; Laura Mercuri, M.; Deplano, P., Chameleon behaviour of iodine in recovering noble-metals from WEEE: towards sustainability and "zero" waste. Green Chem. 2015, 17, (4), 2208-2216. (32) 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. (33) 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. (34) 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. (35) 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. (36) 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. (37) Calgaro, C. O.; Schlemmer, D. F.; da Silva, M. D. C. R.; Maziero, E. V.; Tanabe, E. H.; 31 ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 32 of 47

Bertuol, D. A., Fast copper extraction from printed circuit boards using supercritical carbon dioxide. Waste Manage. 2015, 45, 289-297. (38) 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. (39) 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. (40)

USGS,

Mineral

Commodity

Summaries-Tin.

2007-2017,

https://minerals.usgs.gov/minerals/pubs/commodity/tin/. (41)

USGS,

Minerals

Yearbook-Tin.

2009-2014,

https://minerals.usgs.gov/minerals/pubs/commodity/tin/. (42) Angadi, S. I.; Sreenivas, T.; Jeon, H.-S.; Baek, S.-H.; Mishra, B. K., A review of cassiterite beneficiation fundamentals and plant practices. Miner. Eng. 2015, 70, 178-200. (43) Bulatovic, S. M., Flotation of Tin Minerals. In Handbook of Flotation Reagents: Chemistry, Theory and Practice, Elsevier: Amsterdam, 2010; pp 87-109. (44) Bizzo, W. A.; Figueiredo, R. A.; de Andrade, V. F., Characterization of Printed Circuit Boards for Metal and Energy Recovery after Milling and Mechanical Separation. Materials 2014, 7, (6), 4555-4566. (45) Veit, H. M.; de Pereira, C. C.; Bernardes, A. M., Using mechanical processing in recycling printed wiring boards. JOM 2002, 54, (6), 45-47. (46) Le, H.; Yamasue, E.; Okumura, H.; Ishihara, K., MEMRECS—A Sustainable View for 32 ACS Paragon Plus Environment

Page 33 of 47

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Metal Recycling from Waste Printed Circuit Boards. J. Environ. Prot. 2013, 4, (8), 803-810. (47) Adie, G. U.; Sun, L.; Zeng, X.; Zheng, L.; Osibanjo, O.; Li, J., Examining the evolution of metals utilized in printed circuit boards. Environ. Technol. 2016, 1-6. (48) Leistner, T.; Embrechts, M.; Leißner, T.; Chehreh Chelgani, S.; Osbahr, I.; Möckel, R.; Peuker, U. A.; Rudolph, M., A study of the reprocessing of fine and ultrafine cassiterite from gravity tailing residues by using various flotation techniques. Miner. Eng. 2016, 96–97, 94-98. (49) Zhang, Y.; Liu, B.; Su, Z.; Chen, J.; Li, G.; Jiang, T., Effect of Na2CO3 on the preparation of metallic tin from cassiterite roasted under strong reductive. J. Min. Metall. Sect. B-Metall. 2016, 52, (1), 9-15. (50) Li, J.; Zeng, X.; Stevels, A., Ecodesign in Consumer Electronics: Past, Present, and Future. Crit. Rev. Environ. Sci. Technol. 2015, 45, (8), 840-860. (51) Frazzoli, C.; Mantovani, A.; Orisakwe, O. E., Electronic Waste and Human Health. In Encyclopedia of Environmental Health, Elsevier: Burlington, 2011; pp 269-281. (52) Song, Q.; Li, J., A review on human health consequences of metals exposure to e-waste in China. Environ. Pollut. 2015, 196, 450-461. (53) Subramanian, A.; Kunisue, T.; Tanabe, S., Recent status of organohalogens, heavy metals and PAHs pollution in specific locations in India. Chemosphere 2015, 137, 122-134. (54) Song, Q.; Li, J., A systematic review of the human body burden of e-waste exposure in China. Environ. Int. 2014, 68, 82-93. (55) Xu, S.; Habib, A. H.; Pickel, A. D.; McHenry, M. E., Magnetic nanoparticle-based solder composites for electronic packaging applications. Prog. Mater. Sci. 2015, 67, 95-160. 33 ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 34 of 47

(56) Kettle, P.; Mulqueen, T.; Pearce, J., Tin use survey and market outlook. 2015, https://www.itri.co.uk/index.php?option=com_mtree&task=att_download&link_id=55370&cf_id =24. (57) ITRI, ITRI Reports New Data On Global Tin Use and Recycling. 2008, https://www.itri.co.uk/sustainability/itri-reports-new-data-on-global-tin-use-and-recycling. (58)

ITRI,

ITRI

survey:

tin

demand

growing

slowly.

2012,

https://www.itri.co.uk/sustainability/news-5/itri-survey-tin-demand-growing-slowly. (59) 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 Sustain. Chem. Eng. 2016, 4, (11), 5879-5888. (60) Martchek, K. J., The Importance of Recycling to the Environmental Profile of Metal Products. In Recycling of Metals and Engineered Materials, John Wiley & Sons, Inc.: 2013; pp 19-28. (61) Worrell, E., Recycling of Metals. In Encyclopedia of Energy, Cleveland, C. J., Ed. Elsevier: New York, 2004; pp 245-252. (62) Johnson, J.; Reck, B. K.; Wang, T.; Graedel, T. E., The energy benefit of stainless steel recycling. Energy Policy 2008, 36, (1), 181-192. (63) Kumar, A.; Holuszko, M.; Espinosa, D. C. R., E-waste: An overview on generation, collection, legislation and recycling practices. Resour. Conserv. Recycl. 2017, 122, 32-42. (64) Schwarz, H. G., Aluminum Production and Energy. In Encyclopedia of Energy, Cleveland, C. J., Ed. Elsevier: New York, 2004; pp 81-95. 34 ACS Paragon Plus Environment

Page 35 of 47

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(65) ILZSG, Lead and Zinc Statistics. http://www.ilzsg.org/static/statistics.aspx?from=4 (Accessed 4 April 2017). (66) Cui, J.; Forssberg, E., Mechanical recycling of waste electric and electronic equipment: a review. J. Hazard. Mater. 2003, 99, (3), 243-263. (67) Awasthi, A. K.; Li, J., Management of electrical and electronic waste: A comparative evaluation of China and India. Renew. Sust. Energ. Rev. 2017, 76, 434-447. (68) Kotadia, H. R.; Howes, P. D.; Mannan, S. H., A review: On the development of low melting temperature Pb-free solders. Microelectron. Reliab. 2014, 54, (6–7), 1253-1273. (69) Herat, S., Green Electronics through Legislation and Lead Free Soldering. Clean-Soil Air Water 2008, 36, (2), 145-151. (70) Zeng, K.; Tu, K. N., Six cases of reliability study of Pb-free solder joints in electronic packaging technology. Mater. Sci. Eng. R-Rep. 2002, 38, (2), 55-105. (71) Noor, E. E. M.; Nasir, N. F. M.; Idris, S. R. A., A review: lead free solder and its wettability properties. Solder. Surf. Mt. Technol. 2016, 28, (3), 125-132. (72) Zhou, Y.; Wu, W.; Qiu, K., Recovery of materials from waste printed circuit boards by vacuum pyrolysis and vacuum centrifugal separation. Waste Manage. 2010, 30, (11), 2299-2304. (73) Zhou, Y.; Qiu, K., A new technology for recycling materials from waste printed circuit boards. J. Hazard. Mater. 2010, 175, (1–3), 823-828. (74) Park, S.; Kim, S.; Han, Y.; Park, J., Apparatus for electronic component disassembly from printed circuit board assembly in e-wastes. Int. J. Miner. Process. 2015, 144, 11-15. (75) Wang, J.; Guo, J.; Xu, Z., An environmentally friendly technology of disassembling 35 ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 36 of 47

electronic components from waste printed circuit boards. Waste Manage. 2016, 53, 218-224. (76) Zhu, P.; Chen, Y.; Wang, L. y.; Zhou, M., A new technology for recycling solder from waste printed circuit boards using ionic liquid. Waste Manage. Res. 2012, 30, (11), 1222-1226. (77) Zhu, P.; Chen, Y.; Wang, L. Y.; Qian, G. Y.; Zhou, M.; Zhou, J., A new technology for separation and recovery of materials from waste printed circuit boards by dissolving bromine epoxy resins using ionic liquid. J. Hazard. Mater. 2012, 239–240, 270-278. (78) Mecucci, A.; Scott, K., Leaching and electrochemical recovery of copper, lead and tin from scrap printed circuit boards. J. Chem. Technol. Biotechnol. 2002, 77, (4), 449-457. (79) 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. (80) 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. (81) Yang, C.; Li, J.; Tan, Q.; Liu, L.; Dong, Q., Green Process of Metal Recycling: Coprocessing Waste Printed Circuit Boards and Spent Tin Stripping Solution. ACS Sustain. Chem. Eng. 2017, 5, (4), 3524-3534. (82) Jha, M. K.; Kumari, A.; Choubey, P. K.; Lee, J.-c.; Kumar, V.; Jeong, J., Leaching of lead from solder material of waste printed circuit boards (PCBs). Hydrometallurgy 2012, 121–124, 28-34. (83) Castro, L. A.; Martins, A. H., Recovery of Tin and Copper by Recycling of Printed Circuit 36 ACS Paragon Plus Environment

Page 37 of 47

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Boards from Obsolete Computers. Braz. J. Chem. Eng. 2009, 26, (4), 649-657. (84) Havlik, T.; Orac, D.; Petranikova, M.; Miskufova, A., Hydrometallurgical treatment of used printed circuit boards after thermal treatment. Waste Manage. 2011, 31, (7), 1542-1546. (85) Havlik, T.; Orac, D.; Petranikova, M.; Miskufova, A.; Kukurugya, F.; Takacova, Z., Leaching of copper and tin from used printed circuit boards after thermal treatment. J. Hazard. Mater. 2010, 183, (1–3), 866-873. (86) 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 Sustain. Chem. Eng. 2015, 3, (8), 1696-1700. (87) Holmes, P. R.; Crundwell, F. K., Kinetic aspects of galvanic interactions between minerals during dissolution. Hydrometallurgy 1995, 39, (1-3), 353-375. (88) 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. Sustain. Energy 2017, 36, (3), 873–878 (89) 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. (90) Li, B.; Pan, D. A.; Jiang, Y. H.; Tian, J. J.; Zhang, S. G.; Zhang, K., Recovery of copper and tin from stripping tin solution by electrodeposition. Rare Metals 2014, 33, (3), 353-357. (91) 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. 37 ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 38 of 47

Hydrometallurgy 2003, 70, (1–3), 23-29. (92) Ahn, J. W.; Ryu, S. H.; Kim, T. Y., Recovery of Tin and Nitric Acid from Spent Solder Stripping Solutions. Korean J. Met. Mater. 2015, 53, (6), 426-431. (93) 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. (94) 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. (95) 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. (96) 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. (97) Zhan, L.; Xu, Z. M., Separating and Recovering Pb from Copper-Rich Particles of Crushed Waste Printed Circuit Boards by Evaporation and Condensation. Environ. Sci. Technol. 2011, 45, (12), 5359-5365. (98) Duan, H.; Li, J.; Liu, Y.; Yamazaki, N.; Jiang, W., Characterization and Inventory of PCDD/Fs and PBDD/Fs Emissions from the Incineration of Waste Printed Circuit Board. Environ. Sci. Technol. 2011, 45, (15), 6322-6328. (99) Duan, H.; Li, J.; Liu, Y.; Yamazaki, N.; Jiang, W., Characterizing the emission of chlorinated/brominated dibenzo-p-dioxins and furans from low-temperature thermal processing of waste printed circuit board. Environ. Pollut. 2012, 161, 185-191. 38 ACS Paragon Plus Environment

Page 39 of 47

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(100) Wen, S.; Yang, F.; Li, J. G.; Gong, Y.; Zhang, X. L.; Hui, Y.; Wu, Y. N.; Zhao, Y. F.; Xu, Y., Polychlorinated dibenzo-p-dioxin and dibenzofurans (PCDD/Fs), polybrominated diphenyl ethers (PBDEs), and polychlorinated biphenyls (PCBs) monitored by tree bark in an E-waste recycling area. Chemosphere 2009, 74, (7), 981-987. (101) Li, H.; Yu, L.; Sheng, G.; Fu, J.; Peng, P. A., Severe PCDD/F and PBDD/F pollution in air around an electronic waste dismantling area in China. Environ. Sci. Technol. 2007, 41, (16), 5641-5646. (102) Wu, Y.; Li, Y.; Kang, D.; Wang, J.; Zhang, Y.; Du, D.; Pan, B.; Lin, Z.; Huang, C.; Dong, Q., Tetrabromobisphenol A and heavy metal exposure via dust ingestion in an e-waste recycling region in Southeast China. Sci. Total Environ. 2016, 541, 356-364. (103) Yoshida, A.; Terazono, A.; Ballesteros Jr, F. C.; Nguyen, D.-Q.; Sukandar, S.; Kojima, M.; Sakata, S., E-waste recycling processes in Indonesia, the Philippines, and Vietnam: A case study of cathode ray tube TVs and monitors. Resour. Conserv. Recycl. 2016, 106, 48-58. (104)

Bleher,

D.,

Recycling

Options

for

Waste

CRT

Glass.

2014,

https://www.oeko.de/oekodoc/2061/2014-635-en.pdf. (105) Graedel, T. E.; J., A.; J.P., B.; Reck, B. K.; Sibley, S. F.; Sonnemann, G., UNEP (2011) Recycling Rates of Metals – A Status Report, A Report of the Working Group on the Global Metal Flows to the International Resource Panel. United Nations Environment Programme: 2011. (106) Graedel, T. E.; Allwood, J.; Birat, J. P.; Buchert, M.; Hageluken, C.; Reck, B. K.; Sibley, S. F.; Sonnemann, G., What Do We Know About Metal Recycling Rates? Journal of Industrial Ecology 2011, 15, (3), 355-366. 39 ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(107)

USGS,

Mineral

Commodity

Page 40 of 47

Summaries-Tin.

2017,

https://minerals.usgs.gov/minerals/pubs/commodity/tin/mcs-2017-tin.pdf. (108)

ITRI,

2016

Report

on

Global

Tin

Resources

&

Reserves.

2016,

https://www.itri.co.uk/index.php?option=com_mtree&task=att_download&link_id=55516&cf_id =24. (109) Namias, J. The Future of Electronic Waste Recycling in the United States: Obstacles and Domestic Solutions. Columbia University, New York, United States, 2013. (110) Yin, J.; Gao, Y.; Xu, H., Survey and analysis of consumers' behaviour of waste mobile phone recycling in China. J. Clean Prod. 2014, 65, 517-525. (111) Li, B.; Yang, J.; Song, X.; Lu, B., Survey on Disposal Behaviour and Awareness of Mobile Phones in Chinese University Students. Proc. Environ. Sci. 2012, 16, 469-476. (112) Tan, Q.; Dong, Q.; Liu, L.; Song, Q.; Liang, Y.; Li, J., Potential recycling availability and capacity assessment on typical metals in waste mobile phones: A current research study in China. J. Clean Prod. 2017, 148, 509-517. (113) Akcil, A.; Erust, C.; Gahan, C. S.; Ozgun, M.; Sahin, M.; Tuncuk, A., Precious metal recovery from waste printed circuit boards using cyanide and non-cyanide lixiviants – A review. Waste Manage. 2015, 45, 258-271. (114) Lu, Y.; Xu, Z., Precious metals recovery from waste printed circuit boards: A review for current status and perspective. Resour. Conserv. Recycl. 2016, 113, 28-39. (115) Sakai, S.-i.; Yano, J.; Hirai, Y.; Asari, M.; Yanagawa, R.; Matsuda, T.; Yoshida, H.; Yamada, T.; Kajiwara, N.; Suzuki, G.; Kunisue, T.; Takahashi, S.; Tomoda, K.; Wuttke, J.; Mählitz, P.; 40 ACS Paragon Plus Environment

Page 41 of 47

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Rotter, V. S.; Grosso, M.; Astrup, T. F.; Cleary, J.; Oh, G.-J.; Liu, L.; Li, J.; Ma, H.-w.; Chi, N. K.; Moore, S., Waste prevention for sustainable resource and waste management. J. Mater. Cycles Waste Manag. 2017, 1-19. (116) Rotter, V. S.; Chancerel, P. In Recycling of critical resources - Upgrade introduction, 2012 Electronics Goes Green 2012+, 9-12 Sept. 2012, 2012; 2012; pp 1-6. (117) 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 Sustain. Chem. Eng. 2017, 5, (1), 21-40.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 42 of 47

For Table of Contents Use Only

Recycling？？

E-waste

Where to go？？

Throwing away？？

Synopsis In order to address the shortage of mineral resources and conserve energy, tin recycling from e-waste needs more attention.


Page 43 of 47

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Biographies

Dr. Congren Yang is a postdoctoral fellow at the School of Environment of Tsinghua University (Beijing, China). He received B.Sc., M.Sc., and Ph.D. in minerals processing engineering from the School of Minerals Processing and Bioengineering, Central South University (Changsha, China). His research interest focuses on mineral processing, hydrometallurgy, electronic waste treatment, and metals recycling and sustainability. He has published over 20 peer-reviewed journal articles.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 44 of 47

Dr Quanyin Tan received his diploma and Ph. D degree in Environmental Science and Engineering from Tsinghua University (Beijing, China). Presently, he is a post-doctoral fellow of School of Environment, Tsinghua University and focuses his interests on waste management, technologies for critical and valuable metals recycling from wastes, and on the sustainability and life cycle environmental impacts of these elements.


Page 45 of 47

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Dr Lili Liu is senior program officer of Basel Convention Regional Centre for Asia and the Pacific. She received B.Sc. degree in Chemistry, M.Sc. degree in Organic Chemistry and Ph.D. in Environmental Chemistry. Her research interest is circular economy and urban mining, environmental technology and risk assessment, e-waste policy and management, solid waste treatment and disposal technology. She has led about 50 projects related to solid waste treatment, policy and management. She has published over 30 articles and obtained 15 patents.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 46 of 47

Qingyin Dong is program officer of convention implementation support branch at Basel Convention Regional Centre for Asia and the Pacific. He is an engineer with experience in solid waste management and governance, recycling technologies and demonstration. Currently research focuses on developing new governance models on hazardous waste from social resources in China.


Page 47 of 47

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Dr Jinhui Li is professor in School of Environment of Tsinghua University, executive director of Basel Convention Regional Centre for Asia and the Pacific, and director of Circular Economy Branch of Chinese Society of Environmental Sciences. He obtained a B.Sc. in 1987, a M.Sc. in 1990, and a Ph.D. in environmental chemistry in 1997. His research includes circular economy and urban mining, policy and management of solid waste and hazardous waste, resource technology for e-waste and hazardous waste, environmental risk assessment. He won the 2nd prize of National Science and Technology Progress Award. He has published over 300 articles, and chaired decades of the International Conference on Waste Management and Technology (ICWMT).


Recycling Tin from Electronic Waste: A Problem That Needs More

Recommend Documents