POLLUTANT FORMATION DURING THE THERMAL DECOMPOSITION OF
ELECTRICAL AND ELECTRONIC WASTES
J.A. Conesa*, J. Moltó, R. Font, S. Egea and N. Ortuño
University of Alicante, Department of Chemical Engineering
Ap. 99, E-03080 Alicante (SPAIN)
e-mail:ja.conesa@ua.es
Phone: +34-965903400, Fax: +34-965903826

Abstract
In this contribution we present the results of the research done at the University of Alicante in the last four years [1-7]
about the thermal decomposition of waste electrical and electronic equipment (WEEE). Several materials have beenstudied, including PVC and halogen-free wires, printed circuit boards and casing from mobile phones, as well as
brominated flame reatardants used in the EEE preparation such as TBBPA (tetra-bromo-bisphenol-A). Several
experiments were performed in a nitrogen atmosphere (pyrolysis runs) and also in an oxidative atmosphere with different
oxygen concentrations. Thermogravimetric runs were used to characterize samples, and a horizontal laboratory reactor
was used to study the formation and destruction of pollutants during the thermal decomposition of these samples.
More than 150 compounds, including carbon oxides, light hydrocarbons, polycyclic aromatic hydrocarbons (PAHs),
chlorophenols (ClPhs), chlorobenzenes (ClBzs) and bromophenols (BrPhs) have been identified and quantified.
Furthermore, polychlorodibenzo-p-dioxin and polychlorodibenzofurans (PCDD/Fs), polybromodibenzo-p-dioxin andpolybromodibenzofurans (PBDD/Fs), and dioxin-like PCBs produced were analyzed.

Keywords: pyrolysis, combustion, kinetics, electronic, printed circuit board, dioxins, PAHs, mobile phone

1. Introduction
The wire and cable industry manufactures a wide
range of products that support a multitude ofapplications. Some of the major markets arecommunication cables, power and cable wire, automotive
wiring, control and signal cables, and building wiring.
Generally wires differ in conducting and isolationmaterials. The classic conductor material has been
copper but aluminum is also used frequently today.
Many wire insulation and covering compositions
contain materials, such as lead, halogenatedcompounds, and other compounds, that impart electricalinsulation and fire performance properties. Specifically,
fire retardants are used to avoid the propagation of fire.
One of the most frequently used types of fire retardant,Halogenated Flame Retardants (HFRs), have been
proven to be a hazard to human life and environment,
which has led to regulations on their use with the ultimate
goal of removing from the market.
Recently, The European Parliament has considerate toreview the Restriction of Hazardous Substances (RoHS)
Directive to include compounds not previously coveredby the legislation such as PVC and some HFRs inelectronic equipment. The former directive is closely
related to the directive on Waste Electrical and ElectronicEquipment also known as WEEE directive. WEEE
directive promotes the reuse, recycling, and recovery ofthese wastes as well as the collection of electrical andelectronic wastes as a separate waste stream, which
enhances the prospects for economic recycling. In thissense, End-Of-Life (EOL) communications and low-voltage cables are valuable because these consist ofapproximately 50% copper by weight. The high price ofcopper ensures that an estimated 95% of EOL cable andwire is recycled.
The increase in electronic waste, including cellular
telephones, worldwide is a worrying reality. For thisreason, urgent action on the management of thesewastes is necessary within a framework that respects theenvironment and human health. Mobile phonecomponents can be physically segregated throughgrinding at the dismantling sites, in order to reuse orreprocess (via chemical or physical recycling) therecovered plastics and valuable metals.

2. Materials and Methods
Three different types of EEE were used:
Waste obtained from a mobile phone [1, 4, 5,7]. The first sample was the printed circuitboard alone, including metals (named as EC =Electronic Circuit). The second sample was thecase of the mobile phone (named as MC =Mobile Case) and the last sample was obtainedby crushing mixture of the circuit board and thecase of the phone (named as EW = Electronic
Waste).
Waste from electric PVC and halogen-freewires [2, 6], with and without the presence ofthe metal conductor
Brominated flame retardant used in themanufacture of printed circuit boards, in thiscase TBBPA [3].

7th International Symposium on Feedstock Recycling of Polymeric Materials (7th ISFR 2013)
New Delhi, India, 23-26 October 2013

3. Results and Discussion
A kinetic model for the pyrolysis and combustion ofelectronic waste has been obtained [5,7]. One set ofparameters can explain all the experiments at thedifferent atmospheres and at the different heating rates
used.
At 500 ºC in the combustion of the phone case in thelaboratory reactor high amounts of PCDD/Fs wereobtained, however the pyrolysis of this waste produces alower emission factor for these pollutants, indicating thatfor the thermal treatment of this plastic recovered from ewastes, pyrolysis could be a good option that leads to theformation of gases, oils and chars which can be used as
chemical feedstocks or fuels [5].
Comparisons of pollutant emissions have been carriedout with the thermal treatment of the mobile phonecomponents at 850 ºC, observing the different results
and the possible incidence of the flame-retardants andpresence of copper. The toxicity of the PCDD/Fs
congeners obtained in the combustion of MC is muchless than from the other two wastes. Although they are
not much greater, this indicates the formation of
PCDD/Fs, and consequently the thermal treatment in theindustrial process must be more controlled than whenburning only MC. Details on the possible organic
compounds that can be formed under fuel-rich conditions
can be also useful to analyze the performance ofindustrial processes treating these wastes.
On the other hand, combustion runs of two different
wires, one of them halogen-free and another PVC based,
have been performed in order to study the pollutant
production in different conditions [2, 6]. PAHs, CBs,CPhs, mono to octa-chlorinated dioxins and furans andPCBs where determined for each run. PAHs emission
decreases in the presence of the metal conductor,
whereas the emission of chlorinated species dramaticallyincreases, by using both kinds of wires. PVC wirepresents very much higher emissions than halogenfree
wire, and, as expected, the emission of chlorinatedspecies is also much higher. In this sense, total dioxin
equivalent toxic emissions where approx. 60 pg g-1 in thecase of halogen-free wire, regardless of the presence ofmetal. For PVC wire the emission was 5690 pg g-1 withno metal and 6 times higher in the presence of copper.
PCDD/Fs maximum emissions is of species with a highchlorination degree, except for samples with a highcopper and calcium content, where the maximum isdisplaced to lower chlorine content (2 or 3 chlorineatoms).
Also a kinetic model for the pyrolysis and combustionof PVC and halogen-free electric wires has beenobtained. One set of parameters can explain all theexperiments at the different atmospheres and at thethree different heating rates used. Thermal analysis ofdifferent parts of the cable, cover, insulation andconductive metal, both separately and combined, hasallowed for understanding of the interaction between thedifferent materials [2].
Respect to the TBBPA decomposition [3], in theexperiments carried out at 850 ºC, bromophenols weredetected to a lesser extent, in comparison with theexperiments at 600 ºC. The presence of oxygen does notseem to have a determinant influence in the formation ofthese compounds. A clear predominance of mono-, diand tribrominated phenols was observed, particularly
those with bromine in the positions 2−, 2,6− and 2,4,6−.
For TBBPA pyrolysis, the main isomers are thetetrabrominated ones, whereas in combustion thehexabrominated furans predominate. The yields obtainedin the combustion experiment are nearly four times
higher than those from pyrolysis. An overall examinationof the degradation products emitted during thermal
decomposition of TBBPA has been carried out. Morethan one hundred semivolatile compounds have been
identified with special interest in brominated ones. The
levels of PBDD/Fs have been evaluated, detecting
amounts close to the ppm range. These results should
be considered in the assessment of thermal treatment ofmaterials containing brominated flame retardants, asTBBPA, since the emissions could pose a health andenvironmental risk.

References[1] Moltó, J.; Font, R.; Galvez, A.; Conesa, J.A. Pyrolysis
And Combustion Of Electronic Wastes J. Anal. Appl.
Pyrol. 84, 68-78 (2009)[2] Conesa, J.A.; Egea, S.; Moltó, J.; Font, R. PVC andhalogen-free electric wires thermal decomposition Ind.
Eng. Chem. Res. 49, 11841-11847 (2010)[3] Ortuño, N.; Font, R.; Moltó, J.; Conesa, J.A. Thermaldegradation of TBBPA: emission of polybrominateddibenzo-p-dioxins and dibenzofurans and other organic
compounds Organohalogen Compounds 73, 511-514(2011)[4] Moltó, J.; Egea, S.; Conesa, J.A.; Font, R. Thermal
Decomposition of e-wastes: mobile phone case andother parts Waste Management 31(12) 2546-2552 (2011)[5] Font, R.; Moltó, J.; Egea, S.; Conesa, J.A.
Thermogravimetric kinetic analysis and pollutant
evolution during the pyrolysis and combustion of mobilephone case Chemosphere 85 (3) 516-524 (2011)[6] Conesa, J.A.; Egea, S.; Ortuño, N.; Moltó, J.; Font, R.
Decomposition of Two Types of Electric Wiresconsidering the Effect of the Metal in the Production ofPollutants Chemosphere 91, 118-123 (2013)[7] Ortuño, N.; Moltó, J.; Egea, S.; Font, R.; Conesa, J.A.
Thermogravimetris Study of the Decomposition of Printed
Cirbuit Boards from Mobile Phones J. Anal. Appl. Pyrol.
2013 (in press)

7th International Symposium on Feedstock Recycling of Polymeric Materials (7th ISFR 2013)
New Delhi, India, 23-26 October 2013