Zinc sorption by some Alabama soils

Zinc (Zn) sorption by six Alabama soils, virgin and cultivated was studied. Sorption data was collected at 10° and 30°C and plotted according to the Langmuir, Freundlich, and BET equations. The differential isosteric heats of sorption, AH, were used to aid in the interpretation of the data. The high pH soils sorbed more Zn compared to acid soils. Zinc sorption increased with an increase in temperature indicating that the sorption process was an endothermic reaction. All of the soils gave curvilinear lines when plotted according to the Freundlich equation. The same was true for the Langmuir equation except for the two high pH soils which gave one straight line. Deviation from the ideal Langmuir model was interpreted to be due to the variation in heat of sorption, AH, due to surface heterogeneity. However, the BET equation gave the best fit for the data, yielding one straight line for all soils. The Langmuir sorption maximum, b, was correlated with some selected soil properties. The results indicate that the CEC, organic matter, pH, and clay content were the main contributors to the variation in Zn sorption in these soils.