A REVIEW OF ELECTRONIC WASTE (E-WASTE) RECYCLING TECHNOLOGIES
“IS E-WASTE AN OPPORTUNITY OR TREAT?”
Muammer Kaya and Ayça Sözeri
Osmangazi University, Technological Research Centre (TEKAM), Eskişehir, 26480, Turkey
Keywords: E-waste, Recycling, WEEE, RoHS
Abstract
The purpose of this review is to raise awareness about e-waste
problem in the World. Whether generated at our home or our
office, e-waste is most rapidly growing waste problem in the
world. Even though there are conventional disposal methods (such
as landfill and incineration) for e-waste, these methods have both
economic and environmental disadvantages; recycling is a new
waste management option which diverts end-of-life (EOL)
electrical and electronic equipment (EEE) from landfill and
incineration [1, 2]. Successful diversion strategy must be based on
economic sustainability, technical feasibility and social support
[3]. Recycling infrastructure includes transportation, collection,
recovery and resale establishments. The first part of this paper
describes the e-waste facts, how big is the e-waste problem and
existing recycling programmes and collecting methods in the USA
and EU; second part, describes various methods available to
recover valuable materials (glass, plastic and metals (Pb, Cu, Al,
Steel, Ni, Au, Pd, Cu etc)) in e-waste for a safe and environmental
friendly disposal
Introduction
Since the 1980s, with the development of consumer-oriented
electrical and electronic technologies, countless units of electronic
equipment have been sold to consumers When electronic products
become obsolete and are ready for disposal, they are known as ewaste. Information Technology and Electronic Industry are the
world’s largest and fastest growing manufacturing industries and
as a consequences of this alarming growth, combined with rapid
product obsolescence, discarded electronics is now the fastest
growing solid waste stream in the industrialized world. Most of
the governments have been forced to solve this serious problem
Developed countries that use most of the world’s electronic
products and generate most of the e-waste, tried to solve the
problem by exporting hazardous e-waste to the developing poor
countries of Asia and Africa. Waste Electrical and Electronic
Equipment (WEEE) directive classifies e-waste into 10 groups. Ewaste recovery rate changes from 70% to 80% and reuse and
recycling rate from 50% to 75% (Table 1) 4.
Table I. E-Waste Classification and Recovery, Reuse and
Recycling Ratio in WEEE Directives.
WEEE Category
Rate of Rate of Reuse
Recovery & Recycling
1. Large household appliances (ovens,
refrigerators, driers, washing machines,
air conditioners etc.)
2. Small household appliances (toasters, vacuum cleaners, mixers, ovens)
80%
75%
70%
50%
3. IT& telecommunication appliances
(PCs, desk tops, laptops, printers,
phones, scanners, mouses, faxes,
photocopy machines, computer peripherals, wireless devices etc.)
4. Consumer equipments electronics
(TVs, flat panels, plasmas, LCDs,
HiFis, portable CD players, DVDs,
VCDs, iPods, MP3s, PDAs etc.)
5. Lighting equipments (mainly fluores
cent tubes/bulbs, gas discharge lamp)
75%
65%
75%
65%
70%
50%
6. Electrical and electronic tools (Etools) (drilling machines, electric lawnmowers etc.)
7. Toys, leisure & sports equipments
(electronic toys training machines etc.)
70%
50%
70%
50%
8. Medical devices (X-Ray, MRI, To be established by end
EKG, SEM, Microscopes etc)
of 2008
9. Monitoring and control instruments
70%
50%
(Lasers, GPRS etc)
10. Automatic dispensers (ticket issu80%
75%
ing, vending machines automats).
The volume of obsolete electronics thrown out or temporarily
stored for later disposal is already a serious problem. Land filling,
exporting, re-using and recycling are the currently used processes.
The overwhelming majority of the world’s hazardous waste is
generated by industrialized market economies. Exporting this
waste to less developed countries has been one way in which the
industrialized world has avoided having to deal with the problem
of expensive disposal and close public scrutiny at home.
Exporting of e-waste is profitable and cheaper because of labor
costs and regulations offshore are lax compared to developed
countries law. Shipping monitors (at a price of working $24 and
non-working $6 each) to poor countries for reclamation is 10
times cheaper than recycling the same units at home. Due to
horrific working conditions and weak labor standards in many
developing countries where e-waste is sent, women, children and
prisoners are often occupied and directly exposed to Pb and other
toxic materials when they manually dismantle the EEE to recover
valuable parts for resell. The open burning, acid baths and toxic
dumping into the land, air and water expose the men, women and
children of poor peoples to poison. These operations are likely to
be seriously harming human health. Free trade in hazardous
wastes leaves the poorer people of the world with an untenable
choose between poverty and poison. This e-waste practice should
not be encouraged. Basel Convention banned the export of toxic
components/hazardous e-waste from rich countries to poor
countries for final disposal in 1997. Today, 149 countries signed
Basel convention. However the USA has refused to participate in
this ban. The USA has lobbied Asian governments to establish
bilateral trade agreement to continue dumping hazardous waste
after the Basel Ban came into effect on Jan. 1, 1998 5,1. Re-use
constitutes direct second-hand use, or use after slight
modifications are made to the original functioning equipmentmemory upgrade etc. Re-use makes up a small percentage (about
3% in 1998) of the computers that have been discarded by their
users 5. Sometimes some companies/ organizations donate used
computers/electronic equipment which may/may not work to
schools, non-profit organizations or poor countries. While there
are no figures available, the amount of computers being exported
for re-use is increasingly significant. While extending the useable
life of a computers is good thing, this older units obviously have
limited life-span and will end up as waste sooner or later. Thus
these used computers will also end up as e-waste on foreign
shores, ofter in contries that are least able to deal with them
appropriately. Illegal shipment of e-waste for re-use, but not
suitable for re-use, is often carried out to evade the Basel
Convention by developed countries 5, 1.
E-waste has become a serious problem not only of quantity but
also a crisis born from toxic ingredients (such as Pb, Be, Hg, Cd,
Cr and brominated flame retardants (BFRs) which create
occupational/environmental health threats and hazards. E-waste
contains over 1000 different substances, many of which are toxic,
and creates serious pollution problems upon land filling/burning.
Cathode Ray Tubes (CRTs) in computer monitors, TV sets and
video display devices contain significant concentrations of Pb and
heavy metals. For these type of hazardous waste disposal to the
municipal solid waste (MSW) landfills is prohibited. Each
computer or TV set display contains 2-4 kg of Pb which protects
consumers from X-ray radiation. Consumer electronics already
constitute 40% of Pb and about 70% of the heavy metals (Hg and
Cd) found in landfills. These heavy metals and other hazardous
substances found in electronics can contaminate ground water and
pose other environmental and public health risks. Historically, ewaste has been dumped in landfills or burned in incinerators, just
like other MSW.
Some Facts about e-Waste in the World
According to the US Environmental Protection Agency (EPA),
yearly e-waste produced in the USA, is estimated 5 to 7 million
tons. Only 10% of this e-waste is recycled. 30% or more stored
typically for 3-5 years for future disposal and the rest is land filled
[2]. E-waste already constitutes 2-5% of the US MSW stream and
is growing rapidly [5]. In the EU, 6.5 million tones of e-waste are
generated yearly [3]. In Europe, the volume of e-waste is raising
3-5% per year- almost three times faster than the MWS. Today’s
computer industry innovates very rapidly, bringing new
technologies and “upgrades” to market on average of every 18
months. Conventional TV sets will be replaced by high-definition
(HD) TVs soon, which will put millions of kilos of CRT Pb into
the environment. Between 1980 and 2005, an estimated 410 to
460 million computer CRTs have been sold in the USA.
Approximately 25 million TV sets are sold in the USA annually.
Each year, some 50 million computers and 20 million TVs
become obsolete. The use of TVs in USA may be double that of
computer monitors. But the rate of sales growth (and
obsolescence) is slower in TVs than in computers. Annually less
than 20000 TV units are being recycled in the USA where 5080% of the collected e-waste for recycling are not recycled
domestically at all, but very quickly placed on container ships
bound for destinations like China, India, and Nigeria etc. [3].
India exports 4.5 million PC every year from developed countries.
Currently over 50% of US households own computers. Half of the
turned-in computers are in good working conditions but they are
replaced with the latest technology. In the USA, there are 315 to
680 million unused computers. There were nearly 500 million
obsolete computers in USA between 1997 and 2007. In 1999, 1115% discarded computer is recycled compared with 28% of
overall MSW and 70% of the major appliances recycling in the
USA. Americans own about 2 billion electronic devices or 25 per
household. Consumers have on average 2 to 3 obsolete computers
in their garages, closets, basements, storerooms, attics or storage
spaces for later disposal. Americans have buying more computers,
than any other nations. In California alone, over $1.2 billion will
be spent for e-waste disposal over the next 5 years. Recycling
price of a computer is about $10 to $30 per unit. The cost of
properly disposal of TVs or PCs could easily be $25 to $50. [3].
According to the International Association of Electronics
Recyclers (IAER), 7000 employees were working and $ 700
million annual revenue were obtained from electronic recycling
in the USA in 2003. One hundred thirty million cell phones are
retired each year in the USA.
According to EPA, approximately 78 to 80 million automotive
batteries are consumed and replaced in the USA, not including
those used for large tracks or non-automotive uses, such as lawn
and garden machinery and emergency power and the nationwide
recycling rate is about 90%. 80% of the consumed Pb is
manufactured by the recycling of old Pb-acid batteries in the
secondary smelters. Average battery contains about 9 kilos of Pb.
Primary Pb industry is declining and national demands are filled
by secondary smelters using recycled materials [6]. Household
battery industry in the USA is estimated to be a $ 2.5 billion with
annual sales of nearly 3 billion batteries. These batteries are used
in over 900 million battery operated devices [7] In 2000, over 75
million NiCd batteries, which are considered one of the most
hazardous with respect to disposal, were sold. In Europe the
battery consumption per person is about 10 [5] and 5 billion units
of batteries were produced in year 2000 [7]. Zn-C cells represent
39%, alkaline cells 51% and rechargeable batteries represent 8%
of European portable household battery market. Among the
rechargeable batteries NiCd represents 38%, NiMH 35% and Liion 18% of the European market [8].
Current e-Waste Disposal Methods
Land filling, exporting, re-using and recycling are the currently
used processes. The overwhelming majority of the world’s
hazardous waste is generated by industrialized market economies.
Exporting this waste to less developed countries has been one way
in which the industrialized world has avoided having to deal with
the problem of expensive disposal and close public scrutiny at
home. Due to horrific working conditions and weak labor
standards in many developing countries where e-waste is sent,
women, children and prisoners are often occupied and directly
exposed to Pb and other toxic materials when they manually
dismantle the WEEE to recover valuable parts for resell. The
presence of toxic chemicals also makes e-waste recycling
particularly hazardous to workers, as well as the environment. Ewaste is classified as hazardous waste in some countries.
Current Regulations/Legislations for Solving e-Waste
Problem in the World
E-wastes contain some valuable materials and components that
are technically recyclable. The problem is the lack of collection
incentives and recycling infrastructure as well as high cost of
material collection, handling and processing. Consumers and local
governments have neither the technical ability nor financial
resources to address this problem on their own. Recently, some
local governments and at least two computer manufacturers have
established “pay-as-you-go” collection program that require consumer and small business to pay a fee (7-30 $) in order to drop off
or ship their obsolete computers for recycling. Europe has taken
the lead in addressing the e-waste problem by proposing an
ambitious system of “Extended Producer Responsibility-EPR”.
Most of the legislation for solving e-waste problem falls into three
groups: Producer Take Back, Advanced Recycling Fee (ARF) and
Tax Incentives. E-waste takeback campaign aims to create an
effective system for environmentally responsible recycling and
reuse of consumer electronic products. This campaign promotes
three points: Take it Back, Make it Clean and Recycle Responsibly. Manufacturers may be slowly acknowledging the inevitability of EPR campaigns. The EU has recognized the scope and
urgency of the e-waste problem, recently approved two directives
dealing with this important issue; “Waste Electrical and Electronic Equipment” and “Restriction on the Use of Certain Hazardous Substances” (RoHS). in EEE. The first directive requires that
producers supply systems for the treatment of EEE. The directive
also requires labeling of e-waste identifying the different
components and materials within those components. The RoHS
takes prevention a step further by phasing out the use of
hazardous substances in the production of EEE by 2008. US
should follow the EU’s lead. At both directives, Cd limit is 100
mg/kg (%0.01) and Pb, Cd, Cr, PBB and PBDE limits are 1000
mg/kg ((%0.1). Essentially, the EU is demanding that the industry
find better, less toxic ways to produce their products in hopes of
diminishing the risks of the equipment in the future. The
directives also place full financial responsibility on producers to
set up collection, recycling and disposal systems, and contain
effective and feasible goals for recycling. The cost for this
legislation is only an additional 1% to 3% of retail prices. In ARF
model, only consumer pay in advance the recycling fee, and
producer does not have any responsibility for their products. In
September 2003, SWICO ARF fund was established in
Switzerland [9].
e-Waste Recycling Processes and Technologies
There are different alternatives to the final disposal of e-waste:
landfill (contaminates ground-water), stabilization (requires pretreatment and expensive), incineration (releases metal to air and to
the ashes) and recycling (by hydro/pyrometallurgical processes).
E-waste recyclers first identify products which can be resold for
reuse. Then the remaining products are manually/mechanically
disassembled starting from valuable to cheap ones respectively for
recycling [4, 9]. Permanent collection, special drop-off and
curbside collection are the most extensively used programs for
recycling [3]. E-waste firstly plug-and-play tested and sorted for
reuse, resale or recycle for valuable materials. After working
valuable components and hazardous materials are removed from
the e-waste, ferrous metals are recovered by magnetic separation,
non-ferrous metals by eddy current separation and plastics by
density separation.
Cathode Ray Tube (CRT) Recycling
CRTs are one of the major toxic items in e-waste recycling due to
their volume, costs and disposal restrictions in many countries. A
CRT consists of two parts. One is glass components (funnel, panel
and solder glasses and neck) and the non-glass components
(plastics, steel, Cu, electron gun and phosphor coating). CRT
glass consists of SiO2, Na2O, CaO and other components for
coloring, oxidizing and X-rays protection (K2O, MgO, ZnO, BaO
and PbO). CRTs contain Pb, thus proper handling to avoid
contamination of air, soil and ground water is necessary. CRT
recycling can be performed either glass-to-glass (GTG) or glassto-lead (GTL) recycling. In manual disassembly after washing the
CRTs, the case is removed and the tubes are depressurized. Metals
are separated and plastics are shredded and then one of the GTG
or GTL recycling methods is used. GTG recycling is a closed loop
recycling process. Collected CRTs are ground as a whole into
cullets, which are used to make new CRTs, without separation of
panel and funnel glasses at the recyclers. If the panel glass is
separated from funnel glass with special saw, contamination of
panel glass is avoided. Cullets replace the virgin material reduces
cost and energy demand and emissions from the furnace. GTG
recycling is labor intensive and expensive than GTL recycling.
CRTs may contain 0.5-5 kg Pb in glass. Before smelting CRTs in
the GTL melting, CRTs are shredded and then metals and plastics
are separated. Recovered CRT glass goes to the Pb smelter as a
fluxing agent. GTL process is cheap, automated and has a high
overall throughput. However the process reduces the value of high
quality glass. CRTs disposal at the MSW in Massachusetts,
California, Maine and Minnesota has been banned [3, 10].
According to California Electronics Recycling Act (2003) by
2010 each manufacturer that sales electronic devices must either
collect an equivalent to 90% of the number of devices they sell or
they must pay the alternative fee for recycling the devices they
sell.
Battery Recycling
Most of the Pb-acid accumulators and some of the household
batteries, which contain hazardous waste, are recycled by
manufacturers and recyclers. Secondary smelters recover 90% of
the Pb from used accumulators/batteries all over the world. Pbacid accumulators’ recycling is very similar to the primary Pb
production process. The recycling sequential steps normally are
the separation of plastic case, acid removal, separation of the
plastic, metallic Pb and paste separation, pyrometallurgical
reduction, refining and casting [11]. Rotary, shaft and reverberatory furnaces are the most used. Baghouses provides the
treatment of the gases originated in the furnace. The increasing
environmental pressure exercised during the last 30 years, on both
primary and secondary lead facilities, has stimulated the research
of new and more environment friendly technologies, such as
hydrometallurgy and electrochemistry, as alternative to
pyrometallurgy [12]. Engitec developed the best available CX,
CX-EW and flubor technologies for clean and safe recycling of
the spent Pb-acid batteries [13]. Traditional pyrometallurgical
technologies for the recovery of lead and other materials from
lead-acid batteries have required the use of massive and expensive
air pollution control systems from wastewater treatment plants in
order to attempt to meet environmental requlations. Waste
minimization, pollution prevention and environmentally safe
recycling today are public policy of governments throughout the
world.
In USA, 3 billion household batteries are used every year. In
Germany, yearly 31000 and in England 20000 tones of household
batteries are consumed. In Germany 13000 t/y batteries are
collected and recycled. Household batteries may contain heavy
metals of Pb, Zn, Cd, Hg, Ni, As, Mn, Cr etc. 88% of the Hg and
54% of Cd in MSW in the USA and 10% of Zn, 67% of Ni, and
85% of Cd in MSW of Germany come from discarded household
batteries. In the EU and USA, approximately every year 2 buttons
and 10 household batteries are consumed for each person [4].
In EU, 160000 t/y household, 190000 t/y industrial and 800000 t/y
automobile batteries are consumed. Belqium collects and recycles
59% and Sweden 55% of the batteries sold. In 1991, EU issued a
special requlation regarding the disposal and recycling of batteries
and accumulators containing hazardous materials [14]. According
to an European requlation, all batteries must be regarded as
hazardous wastes and thus need to be treated prior to disposal.
Battery recycling will be compulsory in EU after 2008 and 25%
battery recycling ratio will be achieved until 2016. In linee with
the EU Directives, as of 1 June 2000 the use of batteries
containing more than 25 mg Hg per unit has been prohibited
throughout the EU countries [15]. In Turkey approximately 11000
t/y (200-300 million pieces) household batteries are consumed
ony 260 t/y is collected for recycling [15]. Recycling of mixed
household batteries is difficult and may present Hg vapor hazard.
Only Ni-Cd cells, mercuric oxide and silver oxide button batteries
are recyclable. Li batteries may be deactivated. Hg and Cd use in
batteries are being banned at many countries. In the EU, 75% of
the batteries used at home and 95% used at industry will be
collected and recycled soon. Ni-Cd batteries are more hazardous
than NiMH and Li-ion batteries. Li-ion batteries do not contain
any toxic metals [8]. Table II shows the properties of nonrechargeable, rechargeable batteries and accumulators.
In 1994, The Rechargeable Battery Recycling Corporation
(RBRC) was founded to promote recycling of rechargeable
batteries in N. America. RBRC is a non-profit organization that
collects batteries from consumers and businesses and sends them
to recycling organizations. Inmetco and Toxco are among the
best-known recycling companies in N. America. Europe and Asia
have had programs to recycle spent batteries for many years. Sony
and Sumitomo Metal in Japan have developed a technology to
recycle Co and other precious metals from spent Lion batteries
[16]. Battery recycling process starts by sorting and removing
combustible material (plastics and insulation) with a gas fired
thermal oxidizer. Gases from the thermal oxidizer are sent to the
plant’s scrubber where they are neutralized to remove pollutants.
The process leaves the clean, naked cells, which contain valuable
metal content. Cd is relatively light and vaporizes at high
temperature. In a process that appears like a pan boiling over, a
fan blows the Cd vapor into a large tube which is cooled with
water mist This causes the vapors to condense and produces Cd
that is 99.95% pure. Some recyclers do not separate the metals on
site but pour the liquid metals directly into what the industry
refers as “pigs” (65 pounds) or “hogs” (2000 pounds). The pigs
and hogs are then shipped to metal recovery plants. Here, the
material is used to produce Ni, Ch and Fe re-melt alloy for the
manufacturing of stainless steel and higher products. Current
battery recycling methods requires a high amount of energy. It
takes six to ten times the amount of energy to reclaim materials
from recycled batteries than it would through other means.
NiMH yields the best return. It produces enough Ni to pay for the
process. The highest recycling fees apply to Ni-Cd and Lion
because the demand for Cd is low and Lion contains little
retrievable metal [16]. The flat cost to recycle batteries is about
1000-2000 $ per ton. Europe hopes to achieve a cost per ton of
300$. Transportation cost is important for this reason. Europe sets
up several smaller processing locations in strategic geographical
locations [16].
Table II. Classification and Properties of Batteries/Accumulators.
Type
Properties
NON-RECHARGEABLE BATTERİES
Zn-C
Use: Low energy required applications
Price: Low cost
Recycling: Hydrometallurgical route (H2S04-H2O2
leaching + NaOH Precipitation
Alkaline/
Use: High energy required applications, long life
Manganese Recycling: Same as Zn-C batteries
RECHARGEABLE BATTERIES
Ni-Cd
Commercialization/Development: 1950
(Nic
Use: Portable/ındustrial (wireless communication,
mobile computing, portable applications)
Environmental Impact: Most hazardous (Cd seeps
into the water)
Price: Cheap
NiMH
Commercialization/Development: 1990
(Nickel
Use: Replaced Ni-Cd cells (battery cells)
Metal
Environmental Impact: Environmentally friendly
Hydrate)
(Ni is semi-toxic, electrolyte in large amounts is
hazardous)
Price: Expensive than Ni-Cd
Advantages: Efficient within wide range (-20 to
600C), long lives (500-1000 cycles), low selfdischarge rates)
Li-On
Commercialization/Development: 1990
Use: Cameras, hearing aids and defense applications, cell phones, laptops
Price: Expensive
Environmental Impact: No toxic metals, flammable
with moisture, electrolyte is toxic and flamable
Disposal: Li metal must be totally consumed/
discharged.
Advanyaged: Thin geometry, high charge density
ACCUMULATORS (Auto Baterries)
Pb-Acid
Use: Automobiles, alarm systems, uninterruptible
power supply
Environmental Impact: Hazardous (since 1985
EPA), Pb and H2SO4
Recycling: Pyro/hydrometallurgical. CX, CX-EW
There are several processes for battery recycling [11,17,18].
Sumitomo, Recytec, Atech, Snam-Savam, Sab Nife, Inmetco,
Waelz, TNO and Accurec recycling technologies are currently
available [11]. Sumitomo is a Japonese pyrometallurgical process.
It is expensive and used for recycling all types of portable
batteries except for Ni-Cd. Recytec is a Swiss process that
combines pyro and hydro metallurgies and physical treatment.
Which is suitable for all types of batteries except for Ni-Cd.
Investment cost is low but operating cost is high. Atech is a
physical treatment method for recycling portable batteries. SnamSavam (French) and Sab Nife (Swedish) and Inmetco (N.
American) processes are pyrometallurgical Ni-Cd battery
recycling technologies. TNO is hydrometallurgical Dutch process
for Zn-C and Ni-Cd batteries’ recycling. Accurec process is a
German pyrometallurgical technique for Ni-Cd batteries [11].
Plastic Recycling
Plastics in the EEE are highly visible or hidden in the infrastructure due to insulating properties, strength, resistance,
flexibility and durability. In the EU; in 2002, 2.78 and in 2005,
1.13 million tones of plastic were consumed in the EEE industries
[4,19]. Termoset plastics are shredded when recycling. They are
used in electronics for circuit wiring boards, switch housings,
motor components, breakers etc. Engineering thermoplastics are
used in a wide variety of applications in EEE. Recyclibility of
thermoplastic resins is better than thermoset resins. There are
three ways of post consumer plastic recycling: chemical recycling
process uses waste plastics as raw materials for petrochemical
processes or as a reductant in a metal smelter. Conventional
mechanical recycling process uses shredding, identification and
separation for making new plastic products [12]. In thermal
recycling, plastics are used as an alternative fuel for power
generation or cement kilns. The major resins in TV sets and
computers are HIPS (56%) and ABS (20%) [5]. Generally, 8-12
different types of plastics are found in e-waste. Mixed/unsorted
recycled plastics are cheap. Contaminated and painted plastics
have to be firstly removed before recycling. [3, 4]. In mechanical
recycling, firstly plastics are sorted and identified after removing
of paints and coatings (by cryogenic grinding, abrasion or solvent
stripping) on the surfaces. Shear shredders and hammer mills are
used for size reduction and coarse liberation to separate metals,
fluff and fines. Size reduction achieves easily handled liberated
uniform sizes for separation of dissimilar materials. After metal
removal, mills can be used for further grinding and liberation.
Magnetic separation can be used to remove ferrous material, eddy
current process is used to remove non-ferrous Al. Then, air
classification is used to separate light fractions (such as labels,
papers, films etc) by controlling the air flow velocity. Resin
identification and sorting of plastics are performed later.
Automated sorting and density sorting are not successful.
Triboelectric separator separates material on the basis of surface
charged occurred under rubbing each other. For example, when 24 mm in size ABS is mixed with HIPs, HIPs become negatively
charged and collected at the positively charged electrode and ABS
becomes positively charged and collected at the negatively
charged electrode and separated between each other at a rate of
98% or higher by weight. Delamination of shredded plastics at the
high speed accelerator for plastic separation and XRF
spectroscopy for identify flame-retardants (Br,Sb,P) and restricted
heavy metals (Pb, Hg, Cd) can also be used [3,4]. About one-third
of materials in EEE devices is plastic but only 25% of that is
clean, homogeneous and free from contamination. In the USA,
recycled plastics are used in plastic lumber, outdoor furniture and
roadbed fill materials. Recycled ABS can be used for battery
boxes, compact disc trays, camera casings, laminated floorings,
automotive parts, pallets and roads material as substitute for
stones and gravel.
Metals Recycling
Magnetic and eddy current separators are generally used for metal
separation. The overhead belt magnet separates shredded ferrous
metals from non-ferrous metals. Eddy current separators can
remove non-ferrous Al and Cu from non-metallic materials
according to the electrical conductivity/density (c/d) ratio. Al can
easily be separated from other materials. Stainless steel, plastic
and glass have zero value for c/d ratio, thus they can not be
separated by eddy current separators. The increasing environ-
mental pressure exercised during the last 20 years, on both
primary and secondary metal producing/refining facilities, has
stimulated the research of new and more environmental friendly
technologies, such as hydrometallurgy and electrochemisty, as an
alternative to pyrometallurgy.
Pb Recovery: Pb containing materials are charged to the
reverberatory/rotary furnace where metallic soft Pb bullion (at
99.9% purity) and slag occur from oxidized Sb, As, Sn etc. Slag,
which occurs a thin fluid layer on top, is tapped continuously,
Dust in the flue gas is collected by bag house and fed back into
the furnace to recover Pb. The slag is then charged to blast
furnace along with silica, iron and limestone as fluxing and
scavenging agents to enhance the furnace efficiency. Hard Pb (7585% Pb + 15-25% Sb) is continuously obtained/tapped from blast
furnace. Final slag, which is disposed of in landfills, contains 13% Pb, CaO, SiO2 and FeO [3,4]. Secondary smelters recover
70% of the Pb from old Pb-acid batteries. Isasmelt process for
smelting battery paste and grids was implemented on a
commercial scale in 1991 in Britannia Refined Metals in UK. The
plant was designed to accept whole batteries and produce
approximately 30000 t/y of Pb alloys [21].
Cu Recovery: There are two cost effective methods to recover Cu:
pyro and hydro metallurgical processes. Environment friendly
hydrometallurgical process uses H2SO4 for leaching in
combination with solvent extraction and electrowinning (SXEW). In pyrometallurgical route; roasting, smelting and electrochemical refining steps are used. Outokumpu and Inco flash
smelting, TBRC, Noranda, Mitsubishi smelting methods can be
used. In conventional processes, 5-40% Cu containing e-waste
scrap is charged to the blast/reverberatory furnace along with
scrap Fe and plastics as reducing agents. Sn, Pb and Zn impurities
in the feed are also reduced as gas fumes for 70-85% Cu
containing black Cu production. An air/oxygen converter is used
to produce blister Cu with a 95% Cu purity. In the converter,
impurities are burned out and Fe is removed as slag. Blister Cu
and scrap Cu are melted in the anode furnace with the help of
reductants (such as coke, wood or waste plastics) to produce
anode Cu cast with a purity of 98.5% Cu. Reduction also removes
S. Electrolytic refinery of anode Cu is performed after dissolving
it with H2SO4. Pure cathodic Cu containing 99.99% Cu is
deposited on the cathodes. Slag can be used as roof shingle, sand
blasting and ballasts for rail roods. Energy consumption for
producing Cu from e-waste, is six times less than for producing
Cu ores [3,4].
Precious Metal Recovery: Au, Ag, Pd and Pt can be recovered in
the precious metal refinery. Anode Cu slimes from electrolysis is
pressure leached, dried and smelted with fluxes. During smelting,
Se is recovered. Ag is casted into an Ag anode. After high
intensity electrolytic refining, a high purity Ag cathode and Au
slime anode are formed. The anode Au slime is then leached and
high purity Au, as well as Pd and Pt sludge, is precipitated [3]. Au
recovery from e-waste is the most profitable part of recycling. Ewaste materials contain 40 times more Au than gold ores in the
USA.
Conclusions
Over the last two-three decades, a technological revolution has
taken place in the World. Driven primarily by faster, smaller and
cheaper microchip technology, society is experiencing an
exponential evolution in personal electronic appliances. E-waste is
inevitable by-product of a technological revolution. Market-based
policy approach encourages waste reduction and minimizes
taxpayer responsibility while increasing producer responsibility
from “cradle-to-grave“. E-waste recycling infrastructure for
collection and processing are not well established yet. Exporting
e-waste to overseas is not right, fair and humanistic solution.
Current recycling technologies are not cost-effective and most of
them are not automated and depend on manual operations.
Existing techniques can not also handle easily mixed and complex
e-waste products. Government policies fail to hold manufacturers
responsible for EOL management of their products. Real solution
is producer responsibility and cleaner and safer high-tech
industry. New products should be easier and less expensive to
recycle. Producer responsibility along with state-led recycling
plans for e-waste is the best way for now to solve this fastgrowing problem. Producers also should design their products
with longer life-span and increased recyclibility.
GTL recycling for CRT’s is the best process for economical and
environmental aspects. The best available technology (BAT) for
Pb-acid batteries is afterter paste desuphurization CX, CX-EW
and flubor technologies developed by Engitec for clean and safe
Pb recycling. Conventional pyrometallurgical reduction should be
avoided. Zn-C and alkaline household batteries must be recycled
by hydrometallurgically. Since Ni-Cd batteries are more
hazardous than NiMH and Lion batteries, Sumitomo and Recytec
processes for all type of portable batteries except for Ni-Cd cells
and Snam, Sab Nife, TNO and Accurec processes for Ni-Cd
batteries can be used. Thermoplastics in e-waste can easily be
mechanically recycled using magnetic, electrostatic, gravity and
flotation separation methods. Magnetic and eddy current
separators; pyro and/or hydrometallugical methods are commonly
used for metal (Pb, Cu, precious, etc.) recycling from e-wastes.
Hydrometallurgical
leaching,
solvent
extraction
and
electrowinning are preferred to pyrometallurgical roasting,
smelting or convertion from environmental and/or economical
point of view.
Total e-waste generated in Switzerland 66.046 t/y (2004), in UK
915.000 t/y (2000), in USA 2.124.400 t/y (2002) and in Germany
1.089.000 t/y (2005), respectively. In Switzerland per capita ewaste generation is 9.05, in UK 13.41 kg, in USA 7.33 kg and in
Germany 13.41 kg/person [22]. Thus, 4 kg WEEE should be
collected per person and 75% of this must be recycled each year
in any country. All e-waste must be regarded as hazardous waste
and they must be treated prior to disposal in MSW. Waste
reduction at the source by introducing cleaner products and
processes, recovery of valuables from wastes where possible and
treatment of non-recoverable wastes for safe disposal are required.
Countries must also obey the Basel Convention. E-waste market
generated $ 7.2 billion in 2007 and will generate $11 billion in
2009 in the world [4].
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