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Elemental analysis of ashes of office papers by EDXRF spectrometry
Nuclear Instruments and Methods in Physics Research B 229 (2005) 117–122 www.elsevier.com/locate/nimb
Elemental analysis of ashes of office papers by EDXRF spectrometry M. Rozˇic´ a
a,*
, M. Rozˇmaric´ Macˇefat b, V. Oresˇcˇanin
b
Faculty of Graphic Arts, Chemistry in Graphic Technology, Getaldic´eva 2, 10000 Zagreb, Croatia b Institute Rud-er Bosˇkovic´, Bijenicˇka cesta 54, Zagreb, Croatia Received 17 September 2004; received in revised form 5 November 2004
Abstract The concentrations of the elements Pb, Rb, Sr, Y, Zr, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn and Co were determined in the ash-samples of writing, copying and computer printing papers by energy dispersive X-ray fluorescence (EDXRF). Non-coloured white papers of various manufactures and grammages were considered. Ashes of copying papers printed with black toner and black ink by laser and ink-jet printers were also analyzed. Most of the elements measured in papers showed the lowest concentrations in the ashes of Navigator and Copier papers (Sorpocel S.A., Portugal). Fabriano paper contains significantly higher amount of lead, strontium and zirconium compared to the papers of other manufactures. The concentrations of the elements Co, Mn, Fe, Cr and Ti in the Navigator paper printed by laser printers are significantly higher compared to the non-printed papers. In Fabriano papers the concentrations of the elements Cr, V and Cu as well as organic content increases with paper grammage from 80 to 160 g/m2, while opposite was found for the amount of Pb, Rb, Sr, Y, Zr, K, Ca, Ti, Fe, Ni and Zn. 2004 Elsevier B.V. All rights reserved. Keywords: EDXRF; Elemental; Analysis; Copying paper; Laser prints; Ink-jet prints
1. Introduction The paper has been and still is the most common information carrier. Talking about paper, it primarily refers to writing paper and printing
*
Corresponding author. Tel.: +385 1 2371080; fax: +385 1 2371077. E-mail address: [email protected] (M. Rozˇic´).
paper, rather than to wrapping and packaging paper. Because of increasing demand for paper and shortage of cellulose fibers from flax and cotton, wood is today a main source of raw material for manufacturing of cellulose fibers [1,2]. For chemical treatment of wood in processing, as well as for different additives in paper manufacturing process, different elements can be introduced into paper.
0168-583X/$ - see front matter 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2004.11.011
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M. Rozˇic´ et al. / Nucl. Instr. and Meth. in Phys. Res. B 229 (2005) 117–122
In the production of paper, pulp is diluted to at least 99% with water and a mineral filler and water soluble substances such as optical brighteners and polyvinyl alcohol are added. Depending on paper application, silicates, sulfates, carbonates, oxides and sulfides are used as mineral fillers [1,2]. Very significant components of paper contents are the polyelectrolytes which improve the fineness and filler retention, make the drainage of the paper suspension more efficient, and also add certain qualities. In the past several years, usage of retention means has increased more than usage of any other means, due to increase of the paper machine speed, increased usage of fillers and increase of paper manufacturing from recycled fibres. Retention substances are soluble cationic, non-ionic or anionic polymers. Most used are polyacrylamide, polyethylenimin and cationic starch [3–5]. For improvement of surface properties of paper, as well as for improvement of picture colour and quality, polymers soluble in water, predominantly starch or soluble cellulose products are added in paper mass in a separate process, or paper mass is coated with these substances. The pigment in coating layer could be clay platelets, calcium carbonate, titanium dioxide, calcium sulfate, talc, or synthetic pigments [1]. Because of few literature data related to elemental composition of paper, in this work, using EDXRF method, concentrations of the following elements were determined Pb, Rb, Sr, Y, Zr, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn and Co, in ash samples of papers for writing, copying and computer printing. Papers for ink-jet, laser and digital printing were analyzed. Non-Impact Process printing techniques are increasingly used, therefore photo-copiers are progressively taking printing jobs from small offset printing shops. For that reason, ashes of copying papers printed by laser and ink-jet printers were also analyzed.
2. Experimental 2.1. Paper samples Samples of non-coloured white papers were analyzed:
• Navigator and Copier, by Soporcel S.A., Portugal; IQ Premium, by Neusiedler, Slovakia; IBM, by IBM Corporation Armonk, NY, USA; Fabriano, by Fabriano, Italy; all 80 g/m2. • Fabriano papers of 120, 160 and 240 g/m2. • Navigator paper of 80 g/m2 printed with black toner by laser printers Hewlett Packard 1100 and Kyocera Mita 1000. • Navigator paper of 80 g/m2 printed with black ink by ink-jet printers Epson Stylus Color 850 and Hewlett Packard 1210 psc.
2.2. Paper treatment Paper samples were combusted at 900 C in a muffle-type ignition furnace. In obtained ashes, Pb, Rb, Sr, Y, Zr, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn and Co were analyzed and losses of ignition were determined (Tables 1–3). 2.3. Ash analysis The ashes remained after ignition were prepared for XRF analysis, as a thick target by pressing 1.5– 2 g of each sample into pellets 2 cm in diameter. 2.3.1. Conditions of exciting emission of characteristic X-rays Excitation of the targets were performed by Cd radioactive source. The sample placed in a polyethylene box was placed 1 cm above the source, and then together with the source onto the detector in order to collect the impulses. Between the sample and the source and between the source and the detector, 2 lm mylar foil was placed. 2.3.2. Registering conditions The characteristic X-rays emitted from the sample were registered by liquid nitrogen cooled Si(Li) detector (Canberra). The detector has an active surface of 30 mm2, active diameter 6.2 mm, thickness 3 mm with a 25 lm thick Be-window and resolution at 5.9 keV (Fe55) was 165 eV. The Si(Li) detector is connected to 500 V voltage. The current impulse resulting from the interaction of X-radiation with the detector material is transferred by the pre-amplifier to the amplifier, which improves
M. Rozˇic´ et al. / Nucl. Instr. and Meth. in Phys. Res. B 229 (2005) 117–122
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Table 1 Concentration of elements and relative errors in ashes of papers of 80 g/m2, of different manufacturers Element (mg/kg)
Ashes of office papers (80 g/m2) Navigator
Copier
IBM
IQ Premium
Fabriano
Pb Rb Sr Y Zr K Ca Ti V Cr Mn Fe Ni Cu Zn Co
8.1 ± 0.4 2.31 ± 0.03 141 ± 1 8.8 ± 0.2 8.73 ± 0.05 4300 ± 200 560,000 ± 60,000 <7.3 39 ± 5 31 ± 4 37.8 ± 0.6 516.5 ± 0.6 50 ± 20 21 ± 2 45.9 ± 0.9 0.74 ± 0.01
9.8 ± 0.1 1.261 ± 0.009 140.5 ± 0.3 9.22 ± 0.04 7.88 ± 0.01 4250 ± 50 510,000 ± 10,000 <3.4 38 ± 1 41 ± 1 30.1 ± 0.2 667.1 ± 0.2 49 ± 3 57 ± 1 18.66 ± 0.09 9.8 ± 0.1
9.6 ± 0.1 1.503 ± 0.009 161.0 ± 0.4 12.22 ± 0.06 10.08 ± 0.02 4330 ± 60 510,000 ± 10,000 <3.3 40 ± 1 33.5 ± 1.0 24.3 ± 0.2 658.9 ± 0.2 55 ± 3.0 18.6 ± 0.4 29.5 ± 0.1
9.9 ± 0.1 0.302 ± 0.009 240.6 ± 0.6 15.05 ± 0.07 59.93 ± 0.08 3930 ± 50 500,000 ± 10,000 <3.8 45 ± 2 29.2 ± 0.9 28.5 ± 0.2 753.4 ± 0.3 19 ± 1 17.8 ± 0.4 33.9 ± 0.2
21.4 ± 0.9 1.6 ± 0.3 228.5 ± 0.8 7.8 ± 0.6 387.5 ± 0.9 4200 ± 200 530,000 ± 10,000 <131.5 40 ± 10 27 ± 6 37 ± 8 736 ± 6 39 ± 5 18 ± 1 25 ± 2
Loss by glowing (%)
89.00
87.25
88.25
89.20
88.50
Table 2 Concentrations of elements and relative errors in ashes of Navigator paper of 80 g/m2 after the black printout by computer laser printers Hewlett Packard 1100 and Kyocera Mita 1000 and after the black ink-jet printout by Epson Stylus Color 850 and Hewlett Packard 1210 psc printers Element (mg/kg)
Ashes of office papers (80 g/m2) after printing on laser and ink-jet printers Navigator
Epson Stylus Color 850 (ink-jet)
Hewlett Packard 1210 psc (ink-jet)
Kyocera Mita 1000 (laser)
Hewlett Packard 1100 (laser)
Pb Rb Sr Y Zr K Ca Ti V Cr Mn Fe Ni Cu Zn Co
8.1 ± 0.4 2.31 ± 0.03 141 ± 1 8.8 ± 0.2 8.73 ± 0.05 4300 ± 200 560,000 ± 60,000 <7.3 39 ± 5 31 ± 4 37.8 ± 0.6 516.5 ± 0.6 50 ± 20 21 ± 2 45.9 ± 0.9 0.74 ± 0.01
10.4 ± 0.6 1.72 ± 0.02 162 ± 2 12.7 ± 0.2 9.45 ± 0.05 4800 ± 300 610,000 ± 70,000 <4.0 45 ± 6 36 ± 5 43.8 ± 0.4 1391 ± 1 40 ± 10 24 ± 2 19.1 ± 0.4 0.5 ± 0.01
8.00 ± 0.10 1.06 ± 0.01 133.2 ± 0.3 10.48 ± 0.05 8.86 ± 0.02 4500 ± 60 500,000 ± 10,000 <6.1 56 ± 2 40 ± 1 29.2 ± 0.4 509.4 ± 0.3 48 ± 3 20.0 ± 0.4 15.16 ± 0.1 8.00 ± 0.10
8.8 ± 1.0 1.8 ± 0.3 115 ± 1 9.3 ± 0.6 7.9 ± 0.4 4300 ± 300 510,000 ± 60,000 1390 ± 50
7.4 ± 0.6 2.1 ± 0.2 154 ± 2 7.2 ± 0.3 7.6 ± 0.2 3900 ± 200 430,000 ± 50,000 <53.8
80 ± 10 255 ± 9 82720 ± 90
100 ± 10 343 ± 5 114100 ± 100
190 ± 20 29 ± 2 23.0 ± 0.5
17 ± 2 18.5 ± 0.9 30.4 ± 0.6
Loss by glowing (%)
89.00
89.60
89.40
86.90
85.60
the ratio of the intensity of characteristic lines to the noise level. Software Genie-2000 made by Canberra was used for spectra collection. Registering time was 20,000 s. The software WinAxil of the
same manufacturer was used for the qualitative and quantitative analyses of the obtained spectra. System calibration was performed by IAEASRM – SL1, prepared as a thick target.
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Table 3 Concentrations of elements and relative errors in ashes of papers by Fabriano of 80, 120, 160 and 240 g/m2 Element (mg/kg)
Ashes of office papers by Fabriano (g/m2) 80
120
160
240
Pb Rb Sr Y Zr K Ca Ti V Cr Mn Fe Ni Cu Zn
21.4 ± 0.9 1.6 ± 0.3 228.5 ± 0.8 7.8 ± 0.6 387.5 ± 0.9 4200 ± 200 530,000 ± 10,000 <131.5 40 ± 10.0 27 ± 6.0 37 ± 8.0 736 ± 6.0 39 ± 5.0 18 ± 1.0 25 ± 2.0
7.54 ± 0.09 4.32 ± 0.01 202 ± 0.5 9.22 ± 0.04 377.2 ± 0.5 5480 ± 70 550,000 ± 10,000 <1.8 41 ± 1.0 34 ± 1.0 27.3 ± 0.1 348.9 ± 0.1 22 ± 1.0 18.3 ± 0.4 21.81 ± 0.10
4.3 ± 0.3 <0.7 218 ± 2 5.2 ± 0.4 306 ± 2 2000 ± 200 520,000 ± 50,000 <103.5 6010 39 ± 7 40 ± 6 330 ± 5 <10.7 36 ± 3 8±1
8±2 3.3 ± 0.6 171 ± 1 9±1 314 ± 1 5000 ± 400 480,000 ± 10,000 <251.7 70.2 50 ± 10 44.3 390 ± 10 39 ± 9 17 ± 2 21 ± 3
Loss by glowing (%)
88.50
91.09
89.38
91.94
3. Results and discussion The concentrations of the elements measured in the 80 g/m2 paper ashes of different manufacturers were presented in Table 1. The concentrations of the elements Sr, K, Ca, V, Cr, Mn, Fe, Ni, Zn in ashes of all examined papers except in Copier paper were higher than 20 mg/kg. Navigator and Copier papers by Soporcel S.A. had similar elemental content, with exception of higher content of iron (667.1 ± 0.2 mg/kg) and copper (571 mg/kg) and lower loss on ignition (87.25%) found in Copier paper. Iron content is the lowest in the Navigator paper (516.5 ± 0.6 mg/kg) and the highest in the IQ Premium paper (753.4 ± 0.3 mg/kg). The amount of iron in ash of Copier paper is 667.1 ± 0.2, IBM paper 658.9 ± 0.2 and Fabriano paper 736 ± 6.0 mg/kg. Fabriano paper contain significantly more lead (21.4 ± 0.9 mg/kg), strontium (228.5 ± 0.8 mg/kg), zirconium (387.5 ± 0.9 mg/kg) and titanium (<131.5 mg/kg) compared to the other analysed papers. In ash of IQ Premium paper, there is somewhat higher content of strontium (240.6 ± 0.6 mg/ kg) and significantly lower content of zirconium, compared to Fabriano paper, but the content is still higher compared to ashes of other papers, 59.93 ± 0.08 mg/kg.
In all papers, rather high concentrations of strontium were obtained ranging from 141 ± 1 mg/kg (in ash of Navigator paper) to 240.6 ± 0.6 mg/kg (in ash of IQ Premium paper). Table 2 presents the concentrations of the analyzed elements in ashes of Navigator paper printed with black toner and black ink, by laser printers Hewlett Packard 1100 and Kyocera Mita 1000, and by ink-jet printers Epson Stylus Color 850 and Hewlett Packard 1210 psc. Concentrations of analyzed elements in ash of Navigator paper and in ash of Navigator paper after ink-jet printing with black ink were similar. In ash of Navigator paper printed by Epson Stylus Color 850 printer, concentration of iron is higher compared to ash of the paper before printing, while in ash of the paper printed by Hewlett Packard 1210 psc printer concentrations of vanadium and chromium are slightly higher. In ash of Navigator paper, concentration of iron was 516.5 ± 0.6 mg, in ash of the paper printed by Epson Stylus Color 850 printer 1391 ± 1 mg, while in ash of the paper printed by Hewlett Packard 1210 psc printer it was 509.4 ± 0.3 mg Fe/kg. Ink-jet printers works by spraying ionised ink at a sheet of paper. Similarly to all liquid typographical inks, ink-jet inks shall have certain properties: flowability, viscosity, stability and adhesion. Surface tension and con-
M. Rozˇic´ et al. / Nucl. Instr. and Meth. in Phys. Res. B 229 (2005) 117–122
ductivity are the most important properties of the ink-jet inks. Surface tension affects forming and distribution of ink drops on the printing background. Water is a good solvent for ink-jet inks as its surface tension and conductivity is high, while organic solvents are used when more rapid drying of prints on poorly absorbing printing backgrounds is required. Aqueous inks are commonly used in home and small-office ink-jet printers such as in the Hewlett Packard DeskJet series and Epson Color Stylus series ink-jet printers [6,7]. In ashes of the papers printed by laser printers, concentrations of Co, Mn, Fe, Cr and Ti are significantly higher compared to concentrations of these elements in ashes of the papers before printing. In ash of the non-printed paper, less than 7.3 mg of Ti was obtained, in ash of the paper printed by Kyocera Mita printer 1390 ± 50 mg, in ash of the paper printed by Hewlett Packard 1100 printer less than 53.8 mg/kg of ash. In ash of the paper before printing 31 ± 4 mg Cr was obtained, in ash of the paper after printing by Kyocera Mita printer 80 ± 10 mg, in ash of the paper after printing on Hewlett Packard 1100 printer 100 ± 10 mg Cr/kg. In ash of the paper before printing concentration of manganese is 37.8 ± 0.6 mg, in ash of the paper printed by Kyocera Mita printer 255 ± 9 mg, in ash of the paper after printing on Hewlett Packard 1100 printer 343 ± 5 mg Mn/kg. In ash of the paper before printing 0.74 ± 0.01 mg Co was obtained, in ash of the paper printed by Kyocera Mita printer 23 ± 0.5 mg, in ash of the paper printed by Hewlett Packard 1100 printer 30.4 ± 0.6 mg Co/kg. The results show that concentration of copper (190 ± 20 mg) in ash of the paper printed by Kyocera Mita printer is significantly higher than concentration of copper in ash of the paper before printing (21 ± 2 mg/kg) and in ash of the paper printed by Hewlett Packard 1100 (17 ± 2 mg Cu/kg). Powder toners which are used in laser printing are made from iron powder, pigment (colorant) and meltable resin (polymer). Sooth is the main pigment of black toners. It is composed mostly of carbon with low content of mineral substances. The pigment is blended into plastic particles, so the toner will melt when it passes through the heat of the fuser. Static electricity is the principle behind laser printers. A revol-
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ving drum or cylinder builds up an electrical charge. A tiny laser beam pointed at the drum discharges the surface in the pattern of the letters and images to be printed creating a surface with positive and negative areas. The surface is then coated with toner, that is positively charged so it clings only to the negatively charged areas, and is then passed onto the paper to form the positive image. The paper then passes through heated rollers fusing the toner to the paper [6,7]. Elements Co, Mn, Cr, Ti and Cu in ashes of papers after printing by laser printers are a part of iron powder or a consequence of the laser printing principle. The concentrations of the elements measured in ashes of 80, 120, 160 and 240 g/m2 Fabriano papers were shown in Table 3. Weight of A4 paper, 80 g/ m2, is 5.04 g, of 120 g/m2 7.47 g, of 160 g/m2 9.72 g and of 240 g/m2 14.76 g. Share of organic components in the paper increases with grammage. With increase of paper grammage from 80 to 160 g/m2, loss of ignition increases from 88.50% to 89.38%, with increase of grammage from 120 to 240 g/m2 loss of ignition increases from 91.09% to 91.94%. With increase of paper grammage from 80 to 160 g/m2 concentrations of V, Cr and Cu also increase, while concentrations of Pb, Rb, Sr, Y, Zr, K, Ca, Ti, Fe, Ni, Zn decrease. With increase of paper grammage from 120 to 240 g/m2 concentrations of Ti, Cr, V, Mn, Ni and Fe increase, while concentrations of Rb, Sr, Y, Zr, K, Ca, Cu and Zn decrease.
4. Conclusion In office papers manufactured by different manufacturers, many elements, whose shares were different, were analyzed. Many chemical additives, having different impacts to final properties of the manufactured paper, shall be added during its manufacturing. As manufacturing of paper is actually a secret which is strictly protected by each manufacturer, it is difficult to say where certain elements come from. Taking into account that used additives are not of high chemical purity, it is possible that some elements are introduced as impurities in calcium carbonate, which is used as filler, and in titanium(IV) oxide, which is used as optical bleach.
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Based on the results, it is to assume that Mn, Cr, Co, V, Cu cations are also added separately with a catalyst function in oxidation and polymerization reactions of the polymers which are used as components of the paper and powder toners for laser printing. Examination of elemental composition of paper is important, as certain cations can cause problems in paper usage or in paper recycling. Metal (Fe, Cu and Mn) hydroxides/oxides in various additives catalyze paper acidification [8–10]. During paper recycling, multivalent metal cations (Fe3+, Al3+, Ba2+, Mg2+, Ca2+) reduce swelling of fiber, due to reduction of electrostatic double fiber layer [11]. Reduced swelling inhibits binding of fibers and therefore paper sheets are weak. Therefore, the obtained results can serve as useful information for examination of properties of the office papers, as well as for investigation of possibilities for recycling of the office papers.
References [1] A.M. Springer, Industrial Environmental Control Pulp and Paper Industry, Tappi Press, Atlanta, 1993.
[2] G. Thompson, J. Swain, M. Kay, C.F. Forster, The treatment of pulp and paper mill effluent: a review, Bioresour. Technol. 77 (2001) 275. [3] C. Ovenden, H. Xiao, Flocculation behaviour and mechanisms of cationic inorganic microparticle/polymer systems, Coll. Surf. A: Physicochem. Eng. Aspects 197 (2002) 225. [4] B. Alince, F. Bednar, T.G.M. van de Ven, Deposition of calcium carbonate particles on fiber surfaces induced by cationic polyelectrolyte and bentonite, Coll. Surf. A: Physicochem. Eng. Aspects 190 (2001) 71. [5] A. Swerin, L. Odberg, Flocculation of cellulosic fibre suspensions by a microparticulate retention aid system consisting of cationic polyacrylamide and anionic montmorillonite, Nord. Pulp Pap. Res. J. 11 (1) (1996) 22. [6] R.M. Romano, F.J. Romano (Eds.), The GATF Encyclopedia of Graphic Communications, GATF Press, Pittsburgh, 1998. [7] N.R. Eldred, T. Scarlett, What the Printer Should Know about Ink, GATF, Pittsburgh, 1990. [8] C.J. Shahani, F.H. Hengemihle, Influence of copper and iron on performance of paper, Advances in Chemistry Series No. 212, 1984, p. 387. [9] J.C. Williams, C.S. Fowler, M.S. Lyon, T.L. Merrill, Metallic catalysts in the oxidative degradation of paper, Advances in Chemistry Series No. 164, 1977, p. 37. [10] C.M. Guttman, K.L. Jewett, Protection of archival materials from pollutants: diffusion of sulfur dioxide through boxboard, J. Am. Inst. Conserv. 32 (1993) 81. [11] S.M. Abubakr, B.F. Hrutfiord, T.W. Reichert, W.T. Mckean, Retention mechanism of metal cations in recycled and never-dried pulps, Tappi J. 80 (1997) 143.
Elemental analysis of ashes of office papers by EDXRF spectrometry M. Rozˇic´ a
a,*
, M. Rozˇmaric´ Macˇefat b, V. Oresˇcˇanin
b
Faculty of Graphic Arts, Chemistry in Graphic Technology, Getaldic´eva 2, 10000 Zagreb, Croatia b Institute Rud-er Bosˇkovic´, Bijenicˇka cesta 54, Zagreb, Croatia Received 17 September 2004; received in revised form 5 November 2004
Abstract The concentrations of the elements Pb, Rb, Sr, Y, Zr, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn and Co were determined in the ash-samples of writing, copying and computer printing papers by energy dispersive X-ray fluorescence (EDXRF). Non-coloured white papers of various manufactures and grammages were considered. Ashes of copying papers printed with black toner and black ink by laser and ink-jet printers were also analyzed. Most of the elements measured in papers showed the lowest concentrations in the ashes of Navigator and Copier papers (Sorpocel S.A., Portugal). Fabriano paper contains significantly higher amount of lead, strontium and zirconium compared to the papers of other manufactures. The concentrations of the elements Co, Mn, Fe, Cr and Ti in the Navigator paper printed by laser printers are significantly higher compared to the non-printed papers. In Fabriano papers the concentrations of the elements Cr, V and Cu as well as organic content increases with paper grammage from 80 to 160 g/m2, while opposite was found for the amount of Pb, Rb, Sr, Y, Zr, K, Ca, Ti, Fe, Ni and Zn. 2004 Elsevier B.V. All rights reserved. Keywords: EDXRF; Elemental; Analysis; Copying paper; Laser prints; Ink-jet prints
1. Introduction The paper has been and still is the most common information carrier. Talking about paper, it primarily refers to writing paper and printing
*
Corresponding author. Tel.: +385 1 2371080; fax: +385 1 2371077. E-mail address: [email protected] (M. Rozˇic´).
paper, rather than to wrapping and packaging paper. Because of increasing demand for paper and shortage of cellulose fibers from flax and cotton, wood is today a main source of raw material for manufacturing of cellulose fibers [1,2]. For chemical treatment of wood in processing, as well as for different additives in paper manufacturing process, different elements can be introduced into paper.
0168-583X/$ - see front matter 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2004.11.011
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M. Rozˇic´ et al. / Nucl. Instr. and Meth. in Phys. Res. B 229 (2005) 117–122
In the production of paper, pulp is diluted to at least 99% with water and a mineral filler and water soluble substances such as optical brighteners and polyvinyl alcohol are added. Depending on paper application, silicates, sulfates, carbonates, oxides and sulfides are used as mineral fillers [1,2]. Very significant components of paper contents are the polyelectrolytes which improve the fineness and filler retention, make the drainage of the paper suspension more efficient, and also add certain qualities. In the past several years, usage of retention means has increased more than usage of any other means, due to increase of the paper machine speed, increased usage of fillers and increase of paper manufacturing from recycled fibres. Retention substances are soluble cationic, non-ionic or anionic polymers. Most used are polyacrylamide, polyethylenimin and cationic starch [3–5]. For improvement of surface properties of paper, as well as for improvement of picture colour and quality, polymers soluble in water, predominantly starch or soluble cellulose products are added in paper mass in a separate process, or paper mass is coated with these substances. The pigment in coating layer could be clay platelets, calcium carbonate, titanium dioxide, calcium sulfate, talc, or synthetic pigments [1]. Because of few literature data related to elemental composition of paper, in this work, using EDXRF method, concentrations of the following elements were determined Pb, Rb, Sr, Y, Zr, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn and Co, in ash samples of papers for writing, copying and computer printing. Papers for ink-jet, laser and digital printing were analyzed. Non-Impact Process printing techniques are increasingly used, therefore photo-copiers are progressively taking printing jobs from small offset printing shops. For that reason, ashes of copying papers printed by laser and ink-jet printers were also analyzed.
2. Experimental 2.1. Paper samples Samples of non-coloured white papers were analyzed:
• Navigator and Copier, by Soporcel S.A., Portugal; IQ Premium, by Neusiedler, Slovakia; IBM, by IBM Corporation Armonk, NY, USA; Fabriano, by Fabriano, Italy; all 80 g/m2. • Fabriano papers of 120, 160 and 240 g/m2. • Navigator paper of 80 g/m2 printed with black toner by laser printers Hewlett Packard 1100 and Kyocera Mita 1000. • Navigator paper of 80 g/m2 printed with black ink by ink-jet printers Epson Stylus Color 850 and Hewlett Packard 1210 psc.
2.2. Paper treatment Paper samples were combusted at 900 C in a muffle-type ignition furnace. In obtained ashes, Pb, Rb, Sr, Y, Zr, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn and Co were analyzed and losses of ignition were determined (Tables 1–3). 2.3. Ash analysis The ashes remained after ignition were prepared for XRF analysis, as a thick target by pressing 1.5– 2 g of each sample into pellets 2 cm in diameter. 2.3.1. Conditions of exciting emission of characteristic X-rays Excitation of the targets were performed by Cd radioactive source. The sample placed in a polyethylene box was placed 1 cm above the source, and then together with the source onto the detector in order to collect the impulses. Between the sample and the source and between the source and the detector, 2 lm mylar foil was placed. 2.3.2. Registering conditions The characteristic X-rays emitted from the sample were registered by liquid nitrogen cooled Si(Li) detector (Canberra). The detector has an active surface of 30 mm2, active diameter 6.2 mm, thickness 3 mm with a 25 lm thick Be-window and resolution at 5.9 keV (Fe55) was 165 eV. The Si(Li) detector is connected to 500 V voltage. The current impulse resulting from the interaction of X-radiation with the detector material is transferred by the pre-amplifier to the amplifier, which improves
M. Rozˇic´ et al. / Nucl. Instr. and Meth. in Phys. Res. B 229 (2005) 117–122
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Table 1 Concentration of elements and relative errors in ashes of papers of 80 g/m2, of different manufacturers Element (mg/kg)
Ashes of office papers (80 g/m2) Navigator
Copier
IBM
IQ Premium
Fabriano
Pb Rb Sr Y Zr K Ca Ti V Cr Mn Fe Ni Cu Zn Co
8.1 ± 0.4 2.31 ± 0.03 141 ± 1 8.8 ± 0.2 8.73 ± 0.05 4300 ± 200 560,000 ± 60,000 <7.3 39 ± 5 31 ± 4 37.8 ± 0.6 516.5 ± 0.6 50 ± 20 21 ± 2 45.9 ± 0.9 0.74 ± 0.01
9.8 ± 0.1 1.261 ± 0.009 140.5 ± 0.3 9.22 ± 0.04 7.88 ± 0.01 4250 ± 50 510,000 ± 10,000 <3.4 38 ± 1 41 ± 1 30.1 ± 0.2 667.1 ± 0.2 49 ± 3 57 ± 1 18.66 ± 0.09 9.8 ± 0.1
9.6 ± 0.1 1.503 ± 0.009 161.0 ± 0.4 12.22 ± 0.06 10.08 ± 0.02 4330 ± 60 510,000 ± 10,000 <3.3 40 ± 1 33.5 ± 1.0 24.3 ± 0.2 658.9 ± 0.2 55 ± 3.0 18.6 ± 0.4 29.5 ± 0.1
9.9 ± 0.1 0.302 ± 0.009 240.6 ± 0.6 15.05 ± 0.07 59.93 ± 0.08 3930 ± 50 500,000 ± 10,000 <3.8 45 ± 2 29.2 ± 0.9 28.5 ± 0.2 753.4 ± 0.3 19 ± 1 17.8 ± 0.4 33.9 ± 0.2
21.4 ± 0.9 1.6 ± 0.3 228.5 ± 0.8 7.8 ± 0.6 387.5 ± 0.9 4200 ± 200 530,000 ± 10,000 <131.5 40 ± 10 27 ± 6 37 ± 8 736 ± 6 39 ± 5 18 ± 1 25 ± 2
Loss by glowing (%)
89.00
87.25
88.25
89.20
88.50
Table 2 Concentrations of elements and relative errors in ashes of Navigator paper of 80 g/m2 after the black printout by computer laser printers Hewlett Packard 1100 and Kyocera Mita 1000 and after the black ink-jet printout by Epson Stylus Color 850 and Hewlett Packard 1210 psc printers Element (mg/kg)
Ashes of office papers (80 g/m2) after printing on laser and ink-jet printers Navigator
Epson Stylus Color 850 (ink-jet)
Hewlett Packard 1210 psc (ink-jet)
Kyocera Mita 1000 (laser)
Hewlett Packard 1100 (laser)
Pb Rb Sr Y Zr K Ca Ti V Cr Mn Fe Ni Cu Zn Co
8.1 ± 0.4 2.31 ± 0.03 141 ± 1 8.8 ± 0.2 8.73 ± 0.05 4300 ± 200 560,000 ± 60,000 <7.3 39 ± 5 31 ± 4 37.8 ± 0.6 516.5 ± 0.6 50 ± 20 21 ± 2 45.9 ± 0.9 0.74 ± 0.01
10.4 ± 0.6 1.72 ± 0.02 162 ± 2 12.7 ± 0.2 9.45 ± 0.05 4800 ± 300 610,000 ± 70,000 <4.0 45 ± 6 36 ± 5 43.8 ± 0.4 1391 ± 1 40 ± 10 24 ± 2 19.1 ± 0.4 0.5 ± 0.01
8.00 ± 0.10 1.06 ± 0.01 133.2 ± 0.3 10.48 ± 0.05 8.86 ± 0.02 4500 ± 60 500,000 ± 10,000 <6.1 56 ± 2 40 ± 1 29.2 ± 0.4 509.4 ± 0.3 48 ± 3 20.0 ± 0.4 15.16 ± 0.1 8.00 ± 0.10
8.8 ± 1.0 1.8 ± 0.3 115 ± 1 9.3 ± 0.6 7.9 ± 0.4 4300 ± 300 510,000 ± 60,000 1390 ± 50
7.4 ± 0.6 2.1 ± 0.2 154 ± 2 7.2 ± 0.3 7.6 ± 0.2 3900 ± 200 430,000 ± 50,000 <53.8
80 ± 10 255 ± 9 82720 ± 90
100 ± 10 343 ± 5 114100 ± 100
190 ± 20 29 ± 2 23.0 ± 0.5
17 ± 2 18.5 ± 0.9 30.4 ± 0.6
Loss by glowing (%)
89.00
89.60
89.40
86.90
85.60
the ratio of the intensity of characteristic lines to the noise level. Software Genie-2000 made by Canberra was used for spectra collection. Registering time was 20,000 s. The software WinAxil of the
same manufacturer was used for the qualitative and quantitative analyses of the obtained spectra. System calibration was performed by IAEASRM – SL1, prepared as a thick target.
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Table 3 Concentrations of elements and relative errors in ashes of papers by Fabriano of 80, 120, 160 and 240 g/m2 Element (mg/kg)
Ashes of office papers by Fabriano (g/m2) 80
120
160
240
Pb Rb Sr Y Zr K Ca Ti V Cr Mn Fe Ni Cu Zn
21.4 ± 0.9 1.6 ± 0.3 228.5 ± 0.8 7.8 ± 0.6 387.5 ± 0.9 4200 ± 200 530,000 ± 10,000 <131.5 40 ± 10.0 27 ± 6.0 37 ± 8.0 736 ± 6.0 39 ± 5.0 18 ± 1.0 25 ± 2.0
7.54 ± 0.09 4.32 ± 0.01 202 ± 0.5 9.22 ± 0.04 377.2 ± 0.5 5480 ± 70 550,000 ± 10,000 <1.8 41 ± 1.0 34 ± 1.0 27.3 ± 0.1 348.9 ± 0.1 22 ± 1.0 18.3 ± 0.4 21.81 ± 0.10
4.3 ± 0.3 <0.7 218 ± 2 5.2 ± 0.4 306 ± 2 2000 ± 200 520,000 ± 50,000 <103.5 6010 39 ± 7 40 ± 6 330 ± 5 <10.7 36 ± 3 8±1
8±2 3.3 ± 0.6 171 ± 1 9±1 314 ± 1 5000 ± 400 480,000 ± 10,000 <251.7 70.2 50 ± 10 44.3 390 ± 10 39 ± 9 17 ± 2 21 ± 3
Loss by glowing (%)
88.50
91.09
89.38
91.94
3. Results and discussion The concentrations of the elements measured in the 80 g/m2 paper ashes of different manufacturers were presented in Table 1. The concentrations of the elements Sr, K, Ca, V, Cr, Mn, Fe, Ni, Zn in ashes of all examined papers except in Copier paper were higher than 20 mg/kg. Navigator and Copier papers by Soporcel S.A. had similar elemental content, with exception of higher content of iron (667.1 ± 0.2 mg/kg) and copper (571 mg/kg) and lower loss on ignition (87.25%) found in Copier paper. Iron content is the lowest in the Navigator paper (516.5 ± 0.6 mg/kg) and the highest in the IQ Premium paper (753.4 ± 0.3 mg/kg). The amount of iron in ash of Copier paper is 667.1 ± 0.2, IBM paper 658.9 ± 0.2 and Fabriano paper 736 ± 6.0 mg/kg. Fabriano paper contain significantly more lead (21.4 ± 0.9 mg/kg), strontium (228.5 ± 0.8 mg/kg), zirconium (387.5 ± 0.9 mg/kg) and titanium (<131.5 mg/kg) compared to the other analysed papers. In ash of IQ Premium paper, there is somewhat higher content of strontium (240.6 ± 0.6 mg/ kg) and significantly lower content of zirconium, compared to Fabriano paper, but the content is still higher compared to ashes of other papers, 59.93 ± 0.08 mg/kg.
In all papers, rather high concentrations of strontium were obtained ranging from 141 ± 1 mg/kg (in ash of Navigator paper) to 240.6 ± 0.6 mg/kg (in ash of IQ Premium paper). Table 2 presents the concentrations of the analyzed elements in ashes of Navigator paper printed with black toner and black ink, by laser printers Hewlett Packard 1100 and Kyocera Mita 1000, and by ink-jet printers Epson Stylus Color 850 and Hewlett Packard 1210 psc. Concentrations of analyzed elements in ash of Navigator paper and in ash of Navigator paper after ink-jet printing with black ink were similar. In ash of Navigator paper printed by Epson Stylus Color 850 printer, concentration of iron is higher compared to ash of the paper before printing, while in ash of the paper printed by Hewlett Packard 1210 psc printer concentrations of vanadium and chromium are slightly higher. In ash of Navigator paper, concentration of iron was 516.5 ± 0.6 mg, in ash of the paper printed by Epson Stylus Color 850 printer 1391 ± 1 mg, while in ash of the paper printed by Hewlett Packard 1210 psc printer it was 509.4 ± 0.3 mg Fe/kg. Ink-jet printers works by spraying ionised ink at a sheet of paper. Similarly to all liquid typographical inks, ink-jet inks shall have certain properties: flowability, viscosity, stability and adhesion. Surface tension and con-
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ductivity are the most important properties of the ink-jet inks. Surface tension affects forming and distribution of ink drops on the printing background. Water is a good solvent for ink-jet inks as its surface tension and conductivity is high, while organic solvents are used when more rapid drying of prints on poorly absorbing printing backgrounds is required. Aqueous inks are commonly used in home and small-office ink-jet printers such as in the Hewlett Packard DeskJet series and Epson Color Stylus series ink-jet printers [6,7]. In ashes of the papers printed by laser printers, concentrations of Co, Mn, Fe, Cr and Ti are significantly higher compared to concentrations of these elements in ashes of the papers before printing. In ash of the non-printed paper, less than 7.3 mg of Ti was obtained, in ash of the paper printed by Kyocera Mita printer 1390 ± 50 mg, in ash of the paper printed by Hewlett Packard 1100 printer less than 53.8 mg/kg of ash. In ash of the paper before printing 31 ± 4 mg Cr was obtained, in ash of the paper after printing by Kyocera Mita printer 80 ± 10 mg, in ash of the paper after printing on Hewlett Packard 1100 printer 100 ± 10 mg Cr/kg. In ash of the paper before printing concentration of manganese is 37.8 ± 0.6 mg, in ash of the paper printed by Kyocera Mita printer 255 ± 9 mg, in ash of the paper after printing on Hewlett Packard 1100 printer 343 ± 5 mg Mn/kg. In ash of the paper before printing 0.74 ± 0.01 mg Co was obtained, in ash of the paper printed by Kyocera Mita printer 23 ± 0.5 mg, in ash of the paper printed by Hewlett Packard 1100 printer 30.4 ± 0.6 mg Co/kg. The results show that concentration of copper (190 ± 20 mg) in ash of the paper printed by Kyocera Mita printer is significantly higher than concentration of copper in ash of the paper before printing (21 ± 2 mg/kg) and in ash of the paper printed by Hewlett Packard 1100 (17 ± 2 mg Cu/kg). Powder toners which are used in laser printing are made from iron powder, pigment (colorant) and meltable resin (polymer). Sooth is the main pigment of black toners. It is composed mostly of carbon with low content of mineral substances. The pigment is blended into plastic particles, so the toner will melt when it passes through the heat of the fuser. Static electricity is the principle behind laser printers. A revol-
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ving drum or cylinder builds up an electrical charge. A tiny laser beam pointed at the drum discharges the surface in the pattern of the letters and images to be printed creating a surface with positive and negative areas. The surface is then coated with toner, that is positively charged so it clings only to the negatively charged areas, and is then passed onto the paper to form the positive image. The paper then passes through heated rollers fusing the toner to the paper [6,7]. Elements Co, Mn, Cr, Ti and Cu in ashes of papers after printing by laser printers are a part of iron powder or a consequence of the laser printing principle. The concentrations of the elements measured in ashes of 80, 120, 160 and 240 g/m2 Fabriano papers were shown in Table 3. Weight of A4 paper, 80 g/ m2, is 5.04 g, of 120 g/m2 7.47 g, of 160 g/m2 9.72 g and of 240 g/m2 14.76 g. Share of organic components in the paper increases with grammage. With increase of paper grammage from 80 to 160 g/m2, loss of ignition increases from 88.50% to 89.38%, with increase of grammage from 120 to 240 g/m2 loss of ignition increases from 91.09% to 91.94%. With increase of paper grammage from 80 to 160 g/m2 concentrations of V, Cr and Cu also increase, while concentrations of Pb, Rb, Sr, Y, Zr, K, Ca, Ti, Fe, Ni, Zn decrease. With increase of paper grammage from 120 to 240 g/m2 concentrations of Ti, Cr, V, Mn, Ni and Fe increase, while concentrations of Rb, Sr, Y, Zr, K, Ca, Cu and Zn decrease.
4. Conclusion In office papers manufactured by different manufacturers, many elements, whose shares were different, were analyzed. Many chemical additives, having different impacts to final properties of the manufactured paper, shall be added during its manufacturing. As manufacturing of paper is actually a secret which is strictly protected by each manufacturer, it is difficult to say where certain elements come from. Taking into account that used additives are not of high chemical purity, it is possible that some elements are introduced as impurities in calcium carbonate, which is used as filler, and in titanium(IV) oxide, which is used as optical bleach.
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Based on the results, it is to assume that Mn, Cr, Co, V, Cu cations are also added separately with a catalyst function in oxidation and polymerization reactions of the polymers which are used as components of the paper and powder toners for laser printing. Examination of elemental composition of paper is important, as certain cations can cause problems in paper usage or in paper recycling. Metal (Fe, Cu and Mn) hydroxides/oxides in various additives catalyze paper acidification [8–10]. During paper recycling, multivalent metal cations (Fe3+, Al3+, Ba2+, Mg2+, Ca2+) reduce swelling of fiber, due to reduction of electrostatic double fiber layer [11]. Reduced swelling inhibits binding of fibers and therefore paper sheets are weak. Therefore, the obtained results can serve as useful information for examination of properties of the office papers, as well as for investigation of possibilities for recycling of the office papers.
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