IMPROVEMENTS IN FOAM FLOTATION FOR LEAD REMOVAL
Michael A. Slapik, Environmental Engineer
IBM Corporation
Burlington, Vermont 05401
Edward L. Thackston, Professor
Department of Civd Engineering
David J. Wilson, Professor
Department of Chemistry
Vanderbdt University
Nashville, Tennessee 37235
A prime concern of the environmental engineer at the present time is the removal
of small concentrations of toxic substances from industrial wastewaters. Lead is one of
these toxic substances, and regulatory agencies are now mandating that effluent lead concentrations be in the less than 0.10-mg/l range.
Lead is widely used as an industrial raw material for battery manufacture, printing,
paint and dyeing processes, photographic material, matches, and explosives manufacturing.
Despite its wide use by industry, and the industry-associated lead-bearing wastes which
result from its use, there is very little specific information in the literature on lead concentrations in wastewaters. Concentrations from 5 mg/1 up to 400 mg/1 have been reported
in wastewaters from some of the above sources. Removal methods are chemical precipitation, ion exchange, carbon adsorption, reverse osmosis, and electrodialysis. All of these
methods have some definite drawbacks. Chemical precipitation alone requires extremely
long settling times, and results in a wet, bulky sludge which is not easdy handled. Ion
exchange and carbon adsorption are both very expensive and may require frequent regenerations for adequate performance. Reverse osmosis and electrodialysis require elaborate
and expensive equipment along with high operating costs [ 1 ].
Adsorbing colloid foam flotation is defined as the removal of dissolved material by
adsorption onto colloidal particles followed by removal of the colloidal particle and its
adsorbed material by flotation with a surfactant [ 1 ]. The advantages of adsorbing colloid
foam flotation are its simplicity, effectiveness, and moderate costs. A concentrated and
easdy handled sludge is obtained, which is a major advantage over the chemical precipitation method. Of paramount importance is the small amount of space needed for a
complete adsorbing colloid foam flotation system. The method of adsorbing colloid foam
flotation has been shown to be extremely effective in removing lead [2,3].
PREVIOUS WORK
Thorough reviews of the literature pertaining to the removal of heavy metals by adsorbing colloid foam flotation and other related techniques have been recently completed. A
report by Wdson and Clarke [4] is most up-to-date and includes a reference list of nearly
300 entries. A previous report written by Wilson [3] contains another extensive review,
as does a paper written by Hanson [ 2).
Previous work more directly related to this paper has been reported in papers by Hanson
[2] and Mdler [5]. Their findings are well summarized and reported in an article by
Thackston et al. [ 1].
The earlier work by Hanson was a continuous flow study using a 10-cm ID by 186-cm
length column to remove Pb(II) from a synthetic wastewater. Effluent lead concentrations
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