Abstract
The binding of the cetylpyridinium chloride surfactant (CPC) to sodium humate was studied by the method of equilibrium dialysis without the use of a background electrolyte, at pH=7, at 30°C. The binding isotherm was obtained in a wide concentration range of the CPC: 6·10-6 to 4.96·10-4 mol/L. By increasing the concentration, the isotherm first tends to a saturation step which is followed by a cooperative type of behaviour. The first step was evaluated by an equation derived from the principles similar to those used in the treatment of complexation equilibria. The calculated value of the binding constant (KX=68 900) and the maximum amount of the bounded CPC (qT=8.36 mmol/g C) are in a good agreement with literature data obtained by different experimental method and a different model equation.
Highlights
Dissolved humic substances (HSs) are widespread macromolecular, polydisperse organic colloids occurring in soils, sediments and water as a product of microbial and chemical decomposition of plant and animal residues
In a contaminated environment this speciation of the organic or inorganic xenobiotics are of considerable importance since they can have a large impact on the transport and toxicity of these pollutants
Calibration curve for the cetylpyridinium chloride surfactant (CPC) was made in the concentration range from 2·10-5 to 7·10-4 mol/L, after appropriate dilution the absorbance was measured at λ=259 nm
Summary
Dissolved humic substances (HSs) are widespread macromolecular, polydisperse organic colloids occurring in soils, sediments and water as a product of microbial and chemical decomposition of plant and animal residues Their genesis, solubility, isolation, elemental composition, the investigations of molecular weight, functional groups, chemical structure (NMR, FTIR, UV-VIS, Fluorescence, MS spectra) [1,2,3,4], the interpretation of their acid-base, complexation and adsorption equilibria by various theoretical models [3], colloidal properties [4,5] as well as their environmental significance [6] are all well documented in the referred reviews and monographs of the field. In a contaminated environment this speciation of the organic or inorganic xenobiotics are of considerable importance since they can have a large impact on the transport and toxicity of these pollutants (colloid facilitated transport)
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