determination of heavy metals and halogens in plastics from electric and electronic waste

7
Determination of heavy metals and halogens in plastics from electric and electronic waste Emmanouil Dimitrakakis a , Alexander Janz b , Bernd Bilitewski b , Evangelos Gidarakos a, * a Laboratory of Toxic and Hazardous Waste Management, Department of Environmental Engineering, Technical University of Crete, University Campus, 73100 Chania, Greece b Institute for Waste Management and Contaminated Site Treatment, Dresden University of Technology, Pratzschwitzerstrasse 15, 01796 Pirna, Germany article info Article history: Accepted 30 May 2009 Available online 5 July 2009 abstract The presence of hazardous substances and preparations in small waste electrical and electronic equip- ment (sWEEE) found in the residual household waste stream of the city of Dresden, Germany has been investigated. The content of sWEEE plastics in heavy metals and halogens is determined using handheld X-ray fluorescence analysis (HXRF), elemental analysis by means of atomic absorption spectrometry (AAS) and ion exchange chromatography (IEC). Mean value of results for heavy metals in samples (n = 51) by AAS are 17.4 mg/kg for Pb, 5.7 mg/kg for Cd, 8.4 mg/kg for Cr. The mass fraction of an additive as shown by HXRF (n = 161) can vary over a wide range. Precise deductions as regards sWEEE plastics content in hazardous substances and preparations cannot be made. Additional research would be expe- dient regarding the influence of hazardous substances to recycling processes, in particular regarding the contamination of clean fractions in the exit streams of a WEEE treatment plant. Suitable standards for calibrating HXRF for use on EEE plastics or complex electr(on)ic components do not exist and should be developed. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Problems associated with WEEE have only been acknowledged recently and focus has been on the disposal of large items, or small items with high residual value (e.g., mobile phones). It is important though to deal with the issue particularly in relation to small items, as even if many countries can easily meet the 2002/96/EC (WEEE) Directive targets by means of systems dealing with large appli- ances, it is expected that all WEEE types must be coped with. Moreover, even if white goods (large household appliances, e.g., fridges, washing machines) make up the majority by weight, small and medium sized items are the majority by number. Small WEEE also poses a number of unique problems for reuse and recycling due to its size and diversity (Darby and Obara, 2005; Janz and Rot- ter, 2006). The collection system in Germany has not been entirely suc- cessful in convincing consumers to hand in their used appliances through dedicated routes. In spite of the obligation for separate collection, sorting analyses reveal that sWEEE compose from 0.4% w/w up to 1.5% w/w of the household residual waste stream (Sed- digh et al., 1996; ARGUS, 2004; Janz and Rotter, 2006; Dimitrakakis et al., 2009). Hence, significant quantities are frequently expected to be found, bringing current collection schemes into question. Application of polymeric materials in electrical and electronic equipment (EEE) constantly increases, while a range of different properties is achieved by the incorporation of various additives to polymeric materials. Additives may be inorganic components like pigments (e.g., TiO 2 , ZnO, Cr 2 O 3 , and Fe 2 O 3 ), flame retardants (often brominated organics combined with Sb 2 O 3 ), and various sta- bilizers or plasticizers (e.g., compounds of Ba, Cd, Pb, Sn and Zn). Furthermore, threshold limit values were enacted by the 2002/ 95/EC (RoHS) Directive and its amendments, as regards inorganic and organic substances of toxicological relevance, namely Pb, Cd, Cr(VI), and Hg compounds, polybrominated biphenyls (PBBs) and polybrominated diphenylethers (PBDEs). Recent analytical proce- dures, based mainly on spectroscopic methods, help successful determination of the composition of polymeric materials as shown by Ernst et al. (2000), Fink et al. (2001), Herrera et al. (2003), Pöh- lein et al. (2005), Schlummer et al. (2005), Mans et al. (2007), Hall and Williams (2007), and Nnorom and Osibanjo (2009). For a brief overview see also Fink et al. (2000). It is reported that sWEEE contribute highly to the pollutant load of residual municipal solid waste (MSW) in, e.g., Cd, Pb, Br (Rotter, 2002; Dimitrakakis et al., 2009). There is however limited information regarding sWEEE plastics content in hazardous sub- stances and preparations, information vital for, among others, plants active in recycling of this waste stream. Only a few studies report of concentrations of selected elements in electrical and electronic plastic waste fractions, and they usually refer to differ- ent methodological approaches and samples taken under diverse 0956-053X/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.wasman.2009.05.020 * Corresponding author. Tel.: +30 2821037789; fax: +30 2821037850. E-mail address: [email protected] (E. Gidarakos). Waste Management 29 (2009) 2700–2706 Contents lists available at ScienceDirect Waste Management journal homepage: www.elsevier.com/locate/wasman

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Page 1: Determination of heavy metals and halogens in plastics from electric and electronic waste

Waste Management 29 (2009) 2700–2706

Contents lists available at ScienceDirect

Waste Management

journal homepage: www.elsevier .com/ locate/wasman

Determination of heavy metals and halogens in plastics from electricand electronic waste

Emmanouil Dimitrakakis a, Alexander Janz b, Bernd Bilitewski b, Evangelos Gidarakos a,*

a Laboratory of Toxic and Hazardous Waste Management, Department of Environmental Engineering, Technical University of Crete, University Campus, 73100 Chania, Greeceb Institute for Waste Management and Contaminated Site Treatment, Dresden University of Technology, Pratzschwitzerstrasse 15, 01796 Pirna, Germany

a r t i c l e i n f o

Article history:Accepted 30 May 2009Available online 5 July 2009

0956-053X/$ - see front matter � 2009 Elsevier Ltd.doi:10.1016/j.wasman.2009.05.020

* Corresponding author. Tel.: +30 2821037789; faxE-mail address: [email protected] (E. Gidarako

a b s t r a c t

The presence of hazardous substances and preparations in small waste electrical and electronic equip-ment (sWEEE) found in the residual household waste stream of the city of Dresden, Germany has beeninvestigated. The content of sWEEE plastics in heavy metals and halogens is determined using handheldX-ray fluorescence analysis (HXRF), elemental analysis by means of atomic absorption spectrometry(AAS) and ion exchange chromatography (IEC). Mean value of results for heavy metals in samples(n = 51) by AAS are 17.4 mg/kg for Pb, 5.7 mg/kg for Cd, 8.4 mg/kg for Cr. The mass fraction of an additiveas shown by HXRF (n = 161) can vary over a wide range. Precise deductions as regards sWEEE plasticscontent in hazardous substances and preparations cannot be made. Additional research would be expe-dient regarding the influence of hazardous substances to recycling processes, in particular regarding thecontamination of clean fractions in the exit streams of a WEEE treatment plant. Suitable standards forcalibrating HXRF for use on EEE plastics or complex electr(on)ic components do not exist and shouldbe developed.

� 2009 Elsevier Ltd. All rights reserved.

1. Introduction

Problems associated with WEEE have only been acknowledgedrecently and focus has been on the disposal of large items, or smallitems with high residual value (e.g., mobile phones). It is importantthough to deal with the issue particularly in relation to small items,as even if many countries can easily meet the 2002/96/EC (WEEE)Directive targets by means of systems dealing with large appli-ances, it is expected that all WEEE types must be coped with.Moreover, even if white goods (large household appliances, e.g.,fridges, washing machines) make up the majority by weight, smalland medium sized items are the majority by number. Small WEEEalso poses a number of unique problems for reuse and recyclingdue to its size and diversity (Darby and Obara, 2005; Janz and Rot-ter, 2006).

The collection system in Germany has not been entirely suc-cessful in convincing consumers to hand in their used appliancesthrough dedicated routes. In spite of the obligation for separatecollection, sorting analyses reveal that sWEEE compose from 0.4%w/w up to 1.5% w/w of the household residual waste stream (Sed-digh et al., 1996; ARGUS, 2004; Janz and Rotter, 2006; Dimitrakakiset al., 2009). Hence, significant quantities are frequently expectedto be found, bringing current collection schemes into question.

All rights reserved.

: +30 2821037850.s).

Application of polymeric materials in electrical and electronicequipment (EEE) constantly increases, while a range of differentproperties is achieved by the incorporation of various additivesto polymeric materials. Additives may be inorganic componentslike pigments (e.g., TiO2, ZnO, Cr2O3, and Fe2O3), flame retardants(often brominated organics combined with Sb2O3), and various sta-bilizers or plasticizers (e.g., compounds of Ba, Cd, Pb, Sn and Zn).Furthermore, threshold limit values were enacted by the 2002/95/EC (RoHS) Directive and its amendments, as regards inorganicand organic substances of toxicological relevance, namely Pb, Cd,Cr(VI), and Hg compounds, polybrominated biphenyls (PBBs) andpolybrominated diphenylethers (PBDEs). Recent analytical proce-dures, based mainly on spectroscopic methods, help successfuldetermination of the composition of polymeric materials as shownby Ernst et al. (2000), Fink et al. (2001), Herrera et al. (2003), Pöh-lein et al. (2005), Schlummer et al. (2005), Mans et al. (2007), Halland Williams (2007), and Nnorom and Osibanjo (2009). For a briefoverview see also Fink et al. (2000).

It is reported that sWEEE contribute highly to the pollutantload of residual municipal solid waste (MSW) in, e.g., Cd, Pb, Br(Rotter, 2002; Dimitrakakis et al., 2009). There is however limitedinformation regarding sWEEE plastics content in hazardous sub-stances and preparations, information vital for, among others,plants active in recycling of this waste stream. Only a few studiesreport of concentrations of selected elements in electrical andelectronic plastic waste fractions, and they usually refer to differ-ent methodological approaches and samples taken under diverse

Page 2: Determination of heavy metals and halogens in plastics from electric and electronic waste

E. Dimitrakakis et al. / Waste Management 29 (2009) 2700–2706 2701

conditions. Contaminants concentrations in these studies rangesfrom 40 to 2100 mg/kg for Pb, 2.3 to 2000 mg/kg for Cd, 0.29 to15 mg/kg for Hg, 1900 to 11,000 for Cl, 150 to 250,000 mg/kgfor Br, and 34 to 900 mg/kg for Cr (Vehlow and Mark, 1997; APMEand VKE, 1997; Fink et al., 2000; Freegard et al., 2005; Rotter et al.,2006; Morf et al., 2007; Nnorom and Osibanjo, 2009).

Small WEEE composition can also change significantly due tolegislative provisions and technical, economic or social develop-ments. Chemical analysis represents therefore a useful means ofdetermining changes in composition and assessing the efficacy oflegislative, organizational and technical measures. The aim of thiswork is to explore the heavy metals and halogen content of sWEEEusing HXRF and AAS analysis, serving optimal investigation of aseries of elements.

2. Experimental

2.1. Samples and sample preparation

Manual separation of sWEEE from residual MSW (ordinary re-fuse bin wastes, misdirected from separate collection bins, thusincluding a variety of materials, e.g., food wastes, plastics, etc.) ofthe boroughs Gorbitz, Dölszchen and Striesen of Dresden, Ger-many, took place, during the second half of 2006. Approximately5 tones of MSW from each region were examined for their sWEEEcontent. This amount was considered as an optimal compromisebetween the effort required by the laboratory workforce and sepa-ration of representative MSW quantities. Approximately 180 kg ofsWEEE and single parts were separated in total. The obtained frac-tions from the sorting analyses were MSW with grain size >10 mm,MSW <10 mm, portable household-type batteries and sWEEE.

Specified sWEEE was selected for size reduction of its plastics.All sWEEE appliances were dismantled by means of simple tools,e.g., screwdriver, pliers, to the extent possible without exercisingexcessive force. Materials were divided by visual identification orpermanent magnets into various fractions, of which plastics arethe one of interest, as the various polymeric materials make upthe biggest fraction, corresponding to more than one third(34.16% w/w) of the sample mass. Electric and electronic compo-nents (e.g., motors and coils) make up ca. a quarter of it, whilstthe ferrous metals content is also important (approximately15.6%). Printed wiring boards (PWBs), non-ferrous metals, not dis-

Table 1sWEEE appliances chosen for AAS and IEC analysis.

EEEcategory

EEE product type Number ofappliances

2 Vacuum cleaner 3Appliances for hair drying and spare parts 5Appliances for tooth brushing and spare parts 4Appliances for massage 1Appliances for shaving 1Other body care appliances 4Clocks and watches 7

3 Answering systems 2PC peripherals 3Pocket calculators 3Cellular telephones and pager 4

4 Speakers 3Radio sets 3

6 Equipment for grinding of wood, metal and othermaterials

1

Chargers for capacitors of tools 2

7 Handheld video game consoles 2Video games 2Sports equipment with electr(on)ic components 1

mantled solidly bonded materials and cables are encountered insmall amounts. Other materials (glass, textile, and wood), batter-ies, rubber and Liquid crystal displays (LCDs) constitute only a verysmall proportion of the sample mass. A laboratory precision bal-ance was used. Samples were air blown and washed with deion-ized water to remove dust articles and other possiblecontaminations. Samples were then cut into pieces and ground toa grain size of less than 2 mm by means of a Retsch SM 2000 cut-ting mill (Göttingen, Germany). Sieving analysis was carried outwith the Retsch VE 1000 sieving tower. Stainless steel sieves (Rets-ch) with various opening diameters were used. Sieving of eachsample took place for 10 min (amplitude 1 mm, interval 30 s). Plas-tics of each appliance were milled together, regardless of colour ortype. Table 1 demonstrates the category and type of appliances, ofwhich the plastic samples originate. WEEE plastics from categoriesII to VII (except for IV) are included, according to EEE categoriza-tion of Annex I B of the WEEE directive.

Only the fraction with grain size smaller then 2 mm was usedfor further digestion. For HXRF analysis of plastics no sample prep-aration took place or is required.

2.2. Reagents and materials

Bi-distilled (milli-Q) water was used for preparation of all aque-ous solutions. For the microwave digestion (MW) nitric acid(HNO3, 65%, GR for analysis) and hydrogen peroxide (H2O2, 30%,medical, extra pure, stabilized) were used, obtained from Merck(Darmstadt, Germany). For the oxygen bomb combustion, sodiumhydroxide (NaOH, pellets, GR for analysis), sodium carbonate(Na2CO3, anhydrous, GR for analysis) and sodium hydrocarbonate(NaHCO3, GR for analysis) were purchased from Merck, and usedfor the preparation of the absorption solution as follows: for theproduction of 1 L stock solution, 21.2 g Na2CO3 and 6.3 g NaHCO3

were diluted in bi-distilled water; 50 ml from this solution werethen mixed with 25 ml 30% H2O2 and 7–8 NaOH pellets and dilutedin 1 L bi-distilled water. IEC mobile phase was prepared by adding137.8 mg Na2CO3 and 168.02 mg NaHCO3 per liter of mobile phaseinto bi-distilled water. For the standards of the oxygen bombdigestions, 4-chlorobenzoic acid (C7H5ClO2, for synthesis) and 4-bromobenzoic acid (C7H5ClO2, for synthesis) were acquired fromMerck Schuchardt (Hohenbrunn, Germany).

2.3. Instrumentation and procedures

Microwave digestion followed by analysis with AAS, was se-lected for determination of heavy metals (Pb, Cd, total Cr). Fordetermination of halogens (Cl and Br) oxygen bomb combustionwas chosen, followed by IEC analysis, according to DIN (2005). Pre-ceding analyses were carried out for elements of atomic number>13 by means of portable XRF with no sample preparation.

2.3.1. Handheld XRFAll data was collected using an Xlt 700 (Niton, Billerica, MA,

USA) HXRF spectrometer having a miniature X-ray tube. Two pri-mary excitation sources were used: 241Am (30 mCi) and 109Cd(40 mCi). Simultaneous analysis of up to 25 elements is possible.The ‘plastics ID’ software also uses detection of a high chlorine con-tent to infer that the sample is PVC. No other polymer-type identi-fication is possible. Concentration results are provided in parts permillion (ppm, mg/kg) by data modelling using the included NDTsoftware. Total testing time for each sample was 60 s.

2.3.2. Microwave digestionA microwave sample preparation system Mars 5 (CEM, Mat-

thews, NC, USA) equipped with a rotating sample holder for 12high-pressure PTFE digestion vessels with a capacity of 100 ml

Page 3: Determination of heavy metals and halogens in plastics from electric and electronic waste

2702 E. Dimitrakakis et al. / Waste Management 29 (2009) 2700–2706

was used to digest the samples. Approximately 250–320 mg ofground, dry sample was weighed into each dry, clean vessel. Fivemilliliters 65% nitric acid and 0.5 ml 30% hydrogen peroxide wereadded. Blank digestions (addition of nitric acid and hydrogen per-oxide only) were carried out in the same way. All vessels were thensealed and placed on the rotary-plate of the microwave oven. Thevessel, in which the highest pressure increase is expected, was con-nected to the pressure regulating system. The samples were thenheated using the microwave program shown in Table 2. Power out-put was set to 600 W. After cooling overnight, the vessels wereopened under vacuum hood in order to avoid exhaustion of nitrousgases. Each digested solution was transferred quantitively to a50 ml volumetric flask and filled to the mark with bi-distilledwater. The resulting solutions were filtered over cellulose acetatefilters (0.45 lm, Sartorius, Göttingen, Germany) by means of a fil-ter holder (SM 16249, Sartorius) into polyethylene bottles for fur-ther analysis by AAS. All digested samples were kept at 4 �C in thedark except while in use.

2.3.3. Oxygen bomb combustionA C 7000 (IKA, Staufen, Germany) calorimeter measurement

cell, equipped with a C 48 oxygen station and C 7010 decomposi-tion vessels was used. About 200–250 mg of ground, dry samplewas weighed into the vessel cup. The ignition wire was wrappedaround its posts, the sample cup was placed in its ring, a cottonthread was bent down to the cup, ca. 10 ml of absorption solutionwere added, and the inner part was placed into the body of thebomb. The vessel was then sealed, filled with oxygen (purity>99.95%) at a pressure of 30 bar, and ignited. Each prepared samplewas transferred quantitatively to a 100 ml volumetric flask andfilled to the mark with bi-distilled water. The resulting solutionswere then filtered over cellulose acetate filters (0.20 lm, Sartorius)by means of an SM 16249 filter holder into polyethylene bottles for

Table 2Heating program for the microwave digestion procedure.

Step Time/temperature Pressure limited to (bar)

1 In 3 min to 150� C 5 or 62 3 min hold 5 or 63 In 5 min to 175� C 84 10 min hold 85 In 5 min to 190� C 9 or 106 15 min hold 9 or 10

Table 3Experimental conditions for FAAS and GFAAS analysis.

Element Wavelength (nm) Slit width (nm

Pb 283.3 0.7Cd 228.8 0.7Cu 324.8 0.7Zn 213.9 0.7Ni 232.0 0.2

Table 4Temperature program in the graphite furnace.

Step Temperature (�C) Ramp time

1. Drying 110 12. Combustion 140 153. Incineration 850 104. Atomization 1800 05. Cleaning 2450 16. Cooling 20 1

further analysis by IEC. Standards were combusted and diluted inthe same manner. All combusted samples were kept at 4 �C inthe dark except during daytime while in use.

2.3.4. AAS analysisA Perkin–Elmer model 4100 atomic absorption spectrometer

(Bodenseewerk Perkin–Elmer, Überlingen, Germany) was usedfor flame atomic absorption measurements. It is equipped withburner heads for air–acetylene or N2O–acetylene flame AAS (FAAS)operations, single- or multi-element hollow cathode lamps (HCLs),deuterium background correction and an AS-90 autosampler.Experimental conditions for FAAS analysis are given in Table 3.

Mercury was measured by hydride generation AAS (HGAAS). APerkin–Elmer MHS-FIAS-400 flow injection analysis system, inconjunction with the aforementioned FAAS system, was used. Inthis system, gaseous mercury hydride generation was obtainedby the continuous pumping of sample (in 0.4% HCl), acid solution(3% HCl) and reducing agent (0.2% NaBH4 in 0.05% NaOH) througha reaction coil and into a gas–liquid separator. Argon was used ascarrier gas. For the atomization of mercury hydrides (detected at253.7 nm), a heating controller, heating mantle (parts of theFIAS-400 system) and quartz cell heated to 100 �C were used.

Additional measurements were performed with a Perkin–Elmer4100 ZL graphite furnace AAS (GFAAS), equipped with a transver-sally heated graphite atomizer (THGA), HCLs, deuterium back-ground compensation and the autosampler AS-70. Measurementswere carried out at the most sensitive resonance line for Pb, Cdand Cu (Table 3). The sample solution was injected (20 ll) to thegraphite tube via the dosing arm of the autosampler in the furnacehearth. Injection temperature was 20 �C. The furnace is thenswitched on to attain the required temperature. The temperatureprogram for trapping and determination of analytes in the furnaceis shown in Table 4.

Calibration standards were prepared by spiking the analytes to1% HNO3 aqueous solution (0.4% HCl for FIAS). Calibrations werebased on linear working curves using four of these standards. Allelements were determined diluted in 1% HNO3 aqueous solution,with the exception of mercury. Dilution ratios were: 1:4–1:50 forZn; 1:2 for Ni; 1:100–1:200 for Cu; 1:50–1:100 for Pb; and 1:5–1:10 for Cd.

2.3.5. IEC analysisAnalyses were carried out with an ion chromatograph 733 IC

separation center. It is equipped with a double piston 709 IC pump,

) Lamp current (mA) Flame (l min�1)

8815

C2H2 2.5, air 8.0C2H2 2.5, air 8.0

(s) Hold time (s) Ar int. flow (mL min�1)

30 25030 25020 2506 07 2504 250

Page 4: Determination of heavy metals and halogens in plastics from electric and electronic waste

Microwave Digestion

Oxygen Bomb Combustion

HXRF Analysis (Z>13)

Separation sWEEE from MSW

Dismantling of sWEEE appliances

Material identification &

separation

Size reduction & Sieving

AAS Analysis

(Pb, Cd, Cr)

IEC Analysis (Cl, Br)

Fig. 1. Block diagram of analytical procedure.

E. Dimitrakakis et al. / Waste Management 29 (2009) 2700–2706 2703

a thermostatted 732 IC conductivity detector, a 750 Autosamplerand a continuously regenerable suppressor containing three car-tridges, which are in turn used for suppression, regenerated with50 mmol H2SO4 and rinsed with distilled water (all Metrohm, Her-isau, Switzerland). Anions determination was achieved by meansof a Metrosep Anion Dual 2 column (4.6 � 75 mm; 6.0 lm) and aMetrosep RP guard column, both packed with quaternary ammo-nium polymethacrylate (both Metrohm). Isocratic elution was car-ried out using a solution of Na2CO3 (1.3 mmol)/NaHCO3 (2 mmol).Run time was 13 min, flow rate 0.80 mL/min and pressure 4.1 MPa.Samples were injected using a 20 ll loop injector, and determinedeither undiluted, or diluted on a 1:2 ratio in bi-distilled water. Cal-ibrations were based on linear working curves using seven stan-dard solutions of the analytes of interest.

Experimental procedure described above is presented in theform of a flow sheet in Fig. 1.

3. Results and discussion

A variety of problems occurred during plastics size reduction.Due to warming of the mill, plastics grains clogged it, interruptingthe milling procedure. Regarding particularly ABS, its grains stuckto the mill walls and distributed all over of its inner parts, leadingto increased sample losses (up to 17% of its mass prior to ground-ing), owing probably to electrostatic charging of particles. Lastly,although the last sieve used in the cutting mill had nominal open-ings of 2 mm in diameter, it was observed during sieving that eachsample comprised to a large extent of grains larger than that, inproportions varying between about 1% and 68% w/w (by and largeit was greater than 25% w/w). This phenomenon could be ex-plained by either the grains geometry, allowing for their passingthrough the milling sieve, or to fusion of warm grains after passingit through.

HXRF analyses focused on RoHS restricted substances, namelyelements Cd, Pb, Hg, Cr and Br. In addition, elements with toxico-logical relevance or expected in high frequency were examined,such as As, Sn, Sb, Ti, V, etc. The large number of plastics samplesanalyzed (161) in this work would provide a representative over-

view of the range and concentration of additives in sWEEE plastics.Figs. 2 and 3 give the range of established concentrations, first forthe ‘RoHS elements’ and subsequently for all the others,respectively.

Results reveal that a very small percentage of samples (2 and 1of 161) contained Cd and Pb in concentrations greater than the per-mitted limit (0.01% and 0.1% w/w, respectively). Total Br or Cr con-centration also exceeds the limit of 0.1% w/w in 11 and 2 samples,respectively. However, results show total bromine and chromiumcontent, they cannot be therefore used for drawing conclusionsas regards PBBs, PBDEs or Cr(VI). They may provide though consid-erable indications for the presence of these restricted compoundsin concentrations greater than the limits set. In addition, overtwo thirds of samples contain Cd, Pb and Cr. Half of them containsHg, without exceeding the limit set for its presence in homoge-neous materials. Results for bromine and antimony also demon-strate that about half of the plastics contained brominated flameretardants (BFRs), while in the majority of cases Sb2O3 was usedas synergist. Results for Ti and Zn suggest that a great part of whiteplastics contained Ti (presumably pigment TiO2), and zinc as stabi-lizer or pigment. Organotin compounds are also detected, thoughnot very frequent. Presence of Se, As, V, Ni and Bi was found, andvaried between 18.63% and 68.32% of samples. Au, Cu and Fe arecontained, depicting the range of applications of their compounds.Results also reveal that the mass fraction of a single additive insWEEE plastics can vary over a broad range. Elements like Cd, Pb,Hg, Cr, As, V, Sn, Bi, Se and Au were found in concentrations belowor in very few cases above 1% w/w, whereas concentrations of Br,Sb, Zn, Cu, Fe and Ti may exceed 10% w/w. Bromine concentrationsof up to 11.12% w/w are encountered. The mean Br content over-weighs all other elements and amounts to 0.53% w/w of all sam-ples, while the mean CHg is by far the smallest of them all. Wehave not investigated the cumulative mass content of additivesbut (Fink et al., 2000) reported it may exceed 50%.

It is lastly worth mentioning that XRF calibration standards arecurrently limited to metals doped in homogenous matrices such aspolyethylene and that no suitable standards exist for use on EEEplastics or complex electr(on)ic components. Calibration of XRFfor other elements in different electronic product matrices maylead to more accurate results when applying this technique. Liter-ature highlights the importance of routine calibration of the HXRFanalyzer, as in some cases factory installed elemental rates are sig-nificantly different from calibration standards. It might be advis-able to confirm the results obtained by using more reliablelaboratory analyses methods, and consider HXRF as a very usefulscreening test for elemental concentration (Shrivastava et al.,2005).

Analyses with AAS were focused on RoHS restricted heavy met-als. Samples for AAS analysis were selected from the bulk of sam-ples tested with HXRF, based on results showing largerconcentrations of the analytes of interest in them. Three readingswere carried out for each sample, in order to gain more accurateresults. Category 3 is the most contaminated with Cr, followedby toys and small household appliances. Regarding Pb and Cd, plas-tics of consumer equipment, small household appliances and ICTcontain them to a greater extend. Thus, most additives were ap-plied in plastics of categories 4 and 2, followed by ICT productsand toys (Table 5). Nevertheless, AAS found no element in concen-trations above the RoHS threshold values for homogeneous mate-rials in any of the plastics samples analyzed. Since more than80% of samples originated from appliances 1–5 years old, that isthey were produced before restrictions of the RoHS Directive wereset into force, it appears that its enactment has led producers to ad-just to its demands before they were rendered compulsory, prefer-ring a smooth transition to the new status (Dimitrakakis et al.,2009).

Page 5: Determination of heavy metals and halogens in plastics from electric and electronic waste

Fig. 2. Concentration range for Cd, Pb, Br, Hg, and Cr found in the sWEEE plastic samples.

Fig. 3. Concentration range for As, Sb, Sn, Bi, Se, Au, Zn, Cu, Ni, Fe, V and Ti found in the sWEEE plastic samples.

2704 E. Dimitrakakis et al. / Waste Management 29 (2009) 2700–2706

Page 6: Determination of heavy metals and halogens in plastics from electric and electronic waste

Table 5AAS analyses results for Pb, Cd, Cr per EEE category (mean ± standard deviation, concentrations in mg/kg).

Element EEE category

2 3 4 6 7

Pb 19.87 ± 14.90 15.38 ± 10.29 21.31 ± 12.35 10.27 ± 1.14 9.15 ± 3.87Cd 6.85 ± 19.06 1.16 ± 1.86 19.61 ± 34.86 0.71 ± 0.81 0.49 ± 0.51Cr 6.65 ± 4.20 14.85 ± 16.18 4.91 ± 3.83 1.47 ± 0.23 6.99 ± 9.81

Table 6Comparison between own results and literature data (concentrations in mg/kg, n.d.: not detected).

Element RoHS limit (ppm) Literature data

Literature analyses date 2001 1992–1994 1993–1994 Not mentioned 2004–2005 Not mentionedOwn results(Dimitrakakis et al., 2009)

Morf et al. (2007) Vehlow andMark 1997

APME andVKE (1997)

Fink et al.(2000)

Rotter et al.(2006)

Nnorom andOsibanjo (2009)

HXRF AAS

Pb 1000 34 17.41 1900 100–2100 127–165 500–1000 40–196 5.0–340Cd 100 38 5.71 160 30–240 115–186 200–2000 2.3–56 4.6–1005Hg 1000 5.3 – 0.31 – 0.3–1.4 – 0.29–15 –Cl – – – 8600 1900–11,000 6300–6400 – n.d. –Br 1000 (as PBB or PBDE) 5300 – – 4300–41,000 4200–6800 150–250,000 n.d. –Ni – 480 – 1300 90–800 299–703 – 19–30 5.0–11,000Zn – 360 – 2300 620–5100 361–520 120–5000 187–269 –Cu – 570 – 18,000 80–105,000 – – 391–406 –Cr 1000 (as Cr(VI)) 100 8.38 900 60–380 34–71 – – –Sb – 2000 – 3500 2000–13,000 – 1000–80,000 – –Fe – 780 – 11,000 440–3300 1483–1673 – – –Sn – 140 – 2300 60–2100 139–267 500–3000 – –V – 430 – – 35–900 – – – –Ti – 8000 – – 1500–18,400 4187–4767 300–90,000 – –As – 21 – – 9–46 Up to 10 – – –

E. Dimitrakakis et al. / Waste Management 29 (2009) 2700–2706 2705

Table 6 shows a comparison of the results obtained by thiswork, also quoted in Dimitrakakis et al. (2009), with literature datafor various environmental contaminants in WEEE plastics. As vari-ations are up to 4000%, it is difficult to draw conclusions about theexact content of WEEE plastics in various elements. On the otherhand, most literature studies refer to analyses performed beforeor in 2001. Besides, own results are in the lower region of the con-centrations spectrum, showing a tendency to reduce hazardousadditives in EEE plastics, thus implying that their composition de-pends significantly on their age, which is altered as the years go by,mirroring new production trends. Note lastly that values refer todifferent methodological approaches and samples taken under di-verse conditions. Studies by Vehlow and Mark (1997), APME andVKE (1997), Fink et al. (2000), and Morf et al. (2007) display valuesfor samples coming from the exit streams of WEEE recycling unitsbased on analyses performed on samples of a different origin andnature than that of this study. Nnorom and Osibanjo (2009) onthe other hand deal with obsolete mobile phone plastics. It wouldbe therefore wise that values are dealt with caution. A furtherobservation is that YXRF constantly overestimates the concentra-tion of RoHS elements present in the samples, namely Pb, Cd andCr, when compared with laboratory test results. This is probablydue to the methods inherent limitations, as reported by Shrivastav-a et al. (2005). Thus, it is important to acknowledge the limitationsof this method and results should be reviewed carefully when ana-lyzing with HXRF, in particular near RoHS threshold levels.

Note that as claimed by Dimitrakakis et al. (2009), sWEEE (plas-tics) contribution to the residual MSW pollutant load enteringlandfill in calculated as quite significant for elements Cd, Br andNi, though batteries found in the sWEEE, as well as other materialfractions like PWBs were not included in calculations. This claimraises considerable questions as regards sWEEE contribution tothe MSW pollutant load and subsequently the metals’ fraction

potentially entering landfills reflecting a significant probable risk(Rotter et al., 2006; Morf et al., 2007; Dimitrakakis et al., 2009).

4. Conclusions

Precise deductions as regards sWEEE plastics content in hazard-ous substances and preparations cannot be made. The mass frac-tion of a single additive in sWEEE plastics can vary over a verywide range, whereas results show a tendency for their reductionin EEE plastics. A systematic investigation concerning their contentin hazardous substances should be therefore sought after, leadingto coverage of the existing knowledge gap. Data shall serve to dis-cuss amongst others different recycling or disposal scenarios andrisk assessment of potential hazardousness. Additional researchwould be expedient regarding the influence of hazardous sub-stances to recycling processes, in particular regarding the contam-ination of clean fractions in the exit streams of a WEEE treatmentplant. Future work shall aim at these targets.

It is lastly important to note that no suitable standards exist forcalibrating (H)XRF for use on EEE plastics or complex electr(on)iccomponents. EEE products and applications diversity and the widerange of additives in their plastics render essential the develop-ment of reliable analytical procedures for a big variety of sub-stances. Norm DIN EN 62321 although is still in draft form isanticipated to aid to this aim.

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