Chapter 6. Volatilization During Thermal Plasma Processing of Glass Melts Containing Heavy Metals

  1. John B. Wachtman Jr
  1. Jeffrey W. Wood1,
  2. David G. Cahill1,
  3. Rebecca Cortez2,
  4. Larry D. Stephenson2 and
  5. Hany H. Zaghloul2

Published Online: 26 MAR 2008

DOI: 10.1002/9780470314814.ch6

A Collection of Papers Presented at the 56th Conference on Glass Problems: Ceramic Engineering and Science Proceedings, Volume 17, Issue 2

A Collection of Papers Presented at the 56th Conference on Glass Problems: Ceramic Engineering and Science Proceedings, Volume 17, Issue 2

How to Cite

Wood, J. W., Cahill, D. G., Cortez, R., Stephenson, L. D. and Zaghloul, H. H. (1996) Volatilization During Thermal Plasma Processing of Glass Melts Containing Heavy Metals, in A Collection of Papers Presented at the 56th Conference on Glass Problems: Ceramic Engineering and Science Proceedings, Volume 17, Issue 2 (ed J. B. Wachtman), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470314814.ch6

Author Information

  1. 1

    University of Illinois, Urbana, Illinois

  2. 2

    U.S. Army Construction Engineering Research Laboratories, Champaign, Illinois

Publication History

  1. Published Online: 26 MAR 2008
  2. Published Print: 1 JAN 1996

ISBN Information

Print ISBN: 9780470375419

Online ISBN: 9780470314814

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Keywords:

  • thermal plasma technology;
  • heavy metals;
  • waste disposal;
  • furnace;
  • molten glass

Summary

Thermal plasma technology offers promise as an effective tool to treat a variety of hazardous wastes containing heavy metals. The high-temperature treatment results in effective immobilization of heavy metals into nonleachable glass but is complicated by undesirable volatilization of the metals from the molten glass. The goal of the described research is to instrument a plasma furnace for experiment studies that will lead to an increased understanding of the mechanisms responsible for the volatilization of heavy metals from glass melts. The experimental system consists of a 75-kW transferred arc thermal plasma torch, which is capable of operating in either oxidizing or reducing atmospheres. Gas pressure is automatically controlled, and the specimens may be processed at any pressure between 0.4 and 1 atm. The use of water-cooled furnace walls cools gases within the furnace, causing volatilized material to condense as recoverable particulate. This allows for 95--99% recovery of the volatilized mass for analysis, which is impractical in large-scale, hot-wall furnaces. Also, computerized data acquisition and control of processing conditions allow for a more precisely controlled and characterized procedure than that available in industrial-scale plasma furnaces. Model waste specimens consisting of either high-alumina clay or silicate glasses spiked with 10 wt% iron, nickel, or chromium are processed in atmospheres with various oxygen partial pressures. The presence of a 6 kPa oxygen in a 67 kPa argon atmosphere significantly reduces volatilization of both nickel and silicon from nickel-loaded clay specimen melts. Atomic emission spectroscopy is used to monitor volatilization during processing. Spectra are collected from the 240--380 nm ultraviolet range where the presence of metal vapor is readily detected. Particulate generated from precipitation of the volatilized materials is collected following each specimen run and is analyzed by energy dispersive X-ray analysis to determine composition.