Adsorption of inorganic contaminants in ponded effluents from coal-fired power plants
Name
EL_TR_1985_005.pdf
Size
6.46 MB
Format
Adobe PDF
Checksum (MD5)
c040d08d36800fe291c1a737663a19e7
Author(s)
Dzombak, David A.
Morel, Franȯis
Alternative Title
Inorganic contaminants in ponded effluents from coal-fired power plants, Adsorption of.
Coal-fired power plants, Adsorption of inorganic contaminants in ponded effluents from.
Ponded effluents from coal-fired power plants, Adsorption of inorganic contaminants from.
Date Issued
1985
Publisher
Cambridge, Mass. : Massachusetts Institute of Technology, Ralph M. Parsons Laboratory, Department of Civil Engineering, 1985
Series/Report no.
Energy Laboratory report (Massachusetts Institute of Technology. Energy Laboratory) no. MIT-EL 85-005.
Abstract
The objectives of this study were [1] to conduct some experimental tests of the surface precipitation adsorption model, and [2] to work on the development of a simple yet widely applicable approach to modelling adsorption of inorganic ions on oxide surfaces. The latter represents the first portion of our continuing effort to develop a data base for adsorption of inorganic contaminants in oxide suspensions.
An investigation of the kinetics of cadmium adsorption on hydrous ferric oxide at different initial adsorbate/adsorbent ratios was conducted as a partial test of the surface precipitation model. Kibetics of cadmium adsorption were observed to slow considerably as the adsorbate/adsorbent ratio was increased. The results confirm our hypothesis that adsorption kinetics should decrease as the adsorbate/adsorbent ratio is increased because of the shift from surface complexation to surface precipitation as the dominant adsorption mechanism.
A number of constant pH equilibrium adsorption experiments with cadmium and hydrous ferric oxide were conducted in order to verify the isotherm predicted by the surface precipitation model. A recently published, extensive isotherm for zinc adsorption on hydrous ferric oxide was also examined. This investigation revealed that cation adsorption isotherms exhibit adsorptive saturation at high adsorbate concentrations and that the smooth transition from adsorption to precipitation predicted by the surface precipitation model occurs above this saturation. To model these data, a two site-type model with surface precipitation on weak binding sites is needed.
As the first step in our effort to develop a data base for adsorption of inorganics, we reviewed available adsorption data and surface complexation models and identified a modelling approach capable of describing all existing data. The model that we propose is a two site surface complexation model with surface precipitation on weak binding sites, combined with the diffuse layer model for electrostatic corrections. For proton and anion binding, two site-types and surface precipitation will usually not be necessary - these refinements are included for accurate description of cation binding. The basic diffuse layer surface complexation model is thus the nucleus of the proposed universal model.
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