Influence of Ph, Ionic Strength and Temperatureon Adsorption of Lead, Copper and Zinc in Natural Soil

Sorption of Pb, Zn, Cu by natural soils was investigated under conditions of variable pH, ionic strength and temperature. The results obtained from adsorption isotherm indicated that these data can be better fitted with the Freundlich equation than with the Langmuir equation in terms of regression coefficients. The parameters in the adsorption process were influenced greatly by solution pH and ionic strength. The Freundlich parameter K-F increased with increasing pH and decreasing ionic strength, but the Freundlich parameter n changed adversely. Thermodynamic parameters of the process were calculated from sorption studies performed at different temperatures, and enthalpy changes (Delta H degrees) and entropy changes (Delta S degrees) of adsorption were found as - 20.70 kJ/mol and 34.76 J/mol.K for Pb(II), -7.762 kJ/mol and 1.139 J/mol.K for Cu(II), -20.60 kJ/mol and 51.93 J/mol.K for Zn(II) respectively, showing that adsorption of Pb2+, Cu2+, and Zn2+ on natural soil were exothermic and spontaneous at 5-45 degrees C.