70    TREATMENT OF WASTES CONTAINING ARSENIC,
SELENIUM, THALLIUM, AND MERCURY
COMPOUNDS
Edwin F. Rissmann, Senior Scientist
Stephen M. Schwartz, Senior Environmental Engineer
Versar, Inc.
Springfield, Virginia 22151
INTRODUCTION
Treatment of toxic metal-bearing hazardous wastes and wastewaters is presently well defined in
most cases as is evidenced by discussions in most text books on wastewater treatment. For toxic
substances such as cadmium salts and chromates, a number of well characterized treatment processes
have been extensively described in the literature and experimentally evaluated. Treatment of wastes
containing less common toxic metals, however, has been less extensively studied, particularly for the
following:
• Organomercury compounds (although wastes containing inorganic mercury compounds have
been extensively studied for treatability).
• Arsenic-bearing wastes, particularly those containing organoarsenic and arsine derivatives (there
are fewer than a half dozen producers of organoarsenic compounds, making it difficult to study
these wastes).
• Thallium-bearing wastes, also because of the small number of generators.
• Selenium-bearing wastes, where the waste is not the elemental form (the elemental form is readily
recyclable).
The purpose of this chapter is to discuss viable treatability options for these wastes and to point out
information deficiencies that need to be addressed before such treatment schemes can be viewed as
well established and practical. The chapter is divided into four sections, each of which discusses
treatment of wastes containing one of the four elements of concern.
MERCURY
Production and Use
According to the 1986 Minerals Yearbook, about 46,000 flasks (about 1,750 tons) of mercury were
consumed in the U.S. in 1986.' Table I summarizes the major consumptive uses. With the exception
of the mercury purchased by the paint, batteries, and inorganic chemicals industries, most of the
consumed material was used in metallic form.
Waste Treatment
Mercury wastes basically contain four types of mercury compounds: elemental mercury, monovalent mercurous salts, divalent mercuric salts, and organomercurial compounds. Wastes containing
elemental mercury and inorganic mercury compounds are commonly treated by retorting to recover
elemental mercury and by sulfide precipitation to convert mercury compounds to the highly insoluble
mercuric sulfide. Treatment of these types of mercury compounds has been extensively studied. This
review, accordingly, will focus on waste containing organomercurial compounds.
Aromatic organomercury compounds are not easily treatable by sulfide precipitation because of the
relatively high strength of the bond between mercury and the aromatic ring. To precipitate mercury
from a solution of phenylmercuric acetate, the chief organomercury compound commercially manufactured, the organic portion of the phenylmercury ion must first be removed by chemical reaction.
Hypochlorite oxidation breaks the carbon-mercury bond and converts the organomercurial salt into
44th Purdue Industrial Waste Conference Proceedings, © 1990 Lewis Publishers, Inc., Chelsea, Michigan 48118.
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