Effect of Ionic Charge on the Adsorption of Sodium-Palmitate and Sodium-Laurate onto Galena, Hematite and Cassiterite in Aqueous Solution
The effect of ionic charge on the adsorption of sodium-palmitate and sodium-laurate onto galena, hematite and cassiterite surfaces in aqueous media was studied. The adsorption capacities were determined as a function of adsorbate concentration in the presence of various anions and cations at pH 7.31 and 29 °C. Positively charged ions depressed the adsorption capacity in the order: K+ > Ba2+ > Al3+, showing a reverse correlation with the charge to size ratio of these ions indicating a possible expansion of the double layer that results from predominant diffusion effect and electrostatic effect to some extent. The negatively charged ion enhanced adsorption capacity in the order: PO43- > SO42- > NO3-. This is attributed to the compression of the double layer through electrostatic interaction. In all the studies the adsorption capacities for the adsorbents were in the order: galena > hematite > cassiterite corresponding to the trend in the specific surface area of the adsorbents.