REMOVAL OF SULFIDES BY CATALYTIC OXYGENATION
IN ALKALINE MEDIA
James L. Martin, Project Engineer
Red Star Yeast and Products Company
Universal Foods Corporation
Belle Chasse, Louisiana 70037
Alan J. Rubin, Professor of Civil Engineering
Water Resources Center
The Ohio State University
Columbus, Ohio 43210
INTRODUCTION
Sulfides are environmental pollutants of considerable importance due to their taste,
odor, toxicity and corrosiveness.   They may be present in objectionable amounts because of the biological reduction of sulfur-bearing organic or inorganic substances or
through their direct introduction from industrial processes.   The latter, in particular,
include effluents from the petrochemical, tanning, textile and paper industries.
The removal of sulfides may be accomplished by a number of methods including
biological oxidation, ion exchange, precipitation with heavy metals, stripping of molecular H2S, and chemical oxidation including oxygenation with air or pure Oj.   Chemical oxidation with chlorine dioxide, potassium dichromate, ozone and similar oxidants
is costly especially for high strength industrial wastes.   In contrast, aeration is a relatively
inexpensive removal method for sulfides; however, under normal conditions the process
is slow and leads to undesirable endproducts.   Previous research has shown that the rate
of reaction is greatly increased in the presence of certain metal salts.
The purpose of the research described in this paper was to investigate the factors
controlling the catalytic oxygenation of sulfide so that a practical process could be
developed.   The goal was to achieve high levels of sulfide removal in a reasonable
time while producing a turbidity-free effluent of moderate pH.   Alkaline solutions were
used so as to prevent the formation of elmental sulfur.   Several metal salts at low
concentrations were examined for their catalytic properties under a variety of experimental conditions using an experimental apparatus designed for the precise control of
gas flow rate.
Aqueous Chemistry of Sulfides
In water, sulfide ion, bisulfide ion and molecular hydrogen sulfide are in equilibrium,
their relative concentrations being controlled by the pH of the solution [1].   These
equilibria may be represented by:
H2S # H+ + HS" (1)
HS" * H+ + S" (2)
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