RELEASE OF ARSENIC DURING THE CARBONISATION OF CCA-TREATED WOOD ON A LABORATORY AND PILOT SCALE

Abstract

The release of arsenic during pyrolysis of CCA(chromated copper arsenate)-treated wood starts at a temperature below 327°C, but up to 600°C only 30-40% of the arsenic initially present in the wood is volatilised. The changes of heating rate, wood moisture, degree of the comminution and methods of pyrolysis (fixed bed or mechanically pushed and loosened bulk of chips) do not substantially change the situation. The release of arsenic can be eliminated or strongly reduced by use of carbonisation catalysts. The ways and means of metals regeneration or practical use of this contaminated charcoal are still to be elucidated. A substantial decrease of the As, Cr and Cu content in charcoal from 2800-5550 ppm, 3700-14300 ppm and 3500-8800 ppm to 61 ppm; 1014 ppm and 282 ppm, respectively, was achieved by carbonisation of the previously leached wood specimens. The leachability of CCA-salts from the wood treated with diluted sulphuric acid is good, and the amount of the leached-out metals exceeds 90-95%. Ultrasound treatment improves the leachability, although the effect is not high enough to achieve the full elimination of metals, especially chromium, to meet the concentration levels in charcoal set by legislation.

Keywords

Dates

  • Submission Date2005-05-25
  • Revision Date2006-06-02
  • Acceptance Date2006-09-15

References

  1. Felton, C.C., De Groot, K.C. The recycling potential of preservative-treated wood. For. Prod. J. 46 (1996) 7/8, 37-46.
  2. Leichter, P. Verfahren zur Verwertung von imprägniertem Holz. Europäische Patentanmeldung 0298951, A1, Anmeldetag:04.07.1998.
  3. Cooper, P.A. Leaching of CCA from treated wood: pH effects. For. Prod. J. 41 (1991) 1, 30-32.
  4. Gasco, F. Process to recover poles or other elements of impregnated wood and the respective impregnation substances in solution form, and to regenerate said solution. European Patent Application EP 0774330. Date of filling: 15.11.1996.
  5. Schmidt, R., Marsch, R., Balatinetz, J.J., Cooper, P.A. Increased wood-cement compatibility of chromate treated wood. For. Prod. J. 44 (1994) 7/8, 44-46.
  6. German Federal Government. Ordinance on the Management of Waste Wood, dated 15 August 2002, Annex 2.
  7. Zandersons, J., Gravitis J., Kokorevics, A., Zhurinsh, A., Bikovens, O., Tardenaka, A., Spince, B. Studies of the Brazilian sugarcane bagasse carbonization process and products properties. Biomass and Bioenergy, 17 (1999) 3, 210-219.
  8. Official methods of analysis of the Association of Official Analytic Chemists. 15th edition. Ed. K.Helvich, Publ. Ass. Offic. Anal. Chem., Arlington, 1990, pp. 50, 243-246.
  9. Van der Broeck, K., Helsen, L., Vandecasteele, C., Van den Bulck, E. Determination and characterisation of copper, chromium and arsenic in chromated copper arsenate (CCA) treated wood and its pyrolysis residues by inductively plasma mass spectrometry. Analyst 122 (1997) 7, 695-700.
  10. Standard methods for the examination of water and wastewater. 19th edition. Ed. A.D.Easton. Am. Publ. Health Assoc., Washington, D.C., 1995, Method 3500-As C.
  11. Someus, E. "3R" Solid fuel preventive pre-treatment cleaning. Clean fuels for cost efficient clean energy. Download: www.terrenum.net/cleancoal, June, 2003.
  12. Helsen, L., Van den Bulck, E. Low-temperature pyrolysis as a possible technique for the disposal of CCA-treated wood waste: metal behaviour, in: Progress in Thermochemical Biomass Conversion, vol. 2. Ed. A.V. Bridgwater. Blackwell Science Ltd., Oxford, London, 2001, pp. 1417-1432.
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