Dilatometric study of the adsorption of heavy-metal cations on goethite.
The specific volumes of adsorption of Cd, Co, Cu, Ni, Pb, and Zn on goethite determined by means of the dilatometric method are 21, 32, 32, 31, 31, and 42 cm3/mol, respectively, and are independent of pH. The effect of NaCl (up to 0.5 mol dm(-3)) on the specific volume of adsorption is rather insignificant. The specific volume of precipitation of corresponding hydroxides (determined experimentally and calculated) is about 60 cm3/mol. Apparently, the adsorbed heavy-metal cations lose half of their hydration water. The adsorption constant decreases as the pressure increases, and the effect becomes significant at pressures of > 10(7) Pa, i.e., more than 1 km of water column.
Kosmulski
Marek
M
Department of Electrochemistry, Lublin University of Technology, Lublin, Poland. mkosmuls@abo.fi
Maczka
Edward
E