Adsorption; lead (II); coal; temperature effect

Adsorption behavior of lead (II) ions on oxidative altered bituminous and subbituminous coals was investigated at temperatures 30 and 60°C. The adsorption isotherms as well as the adsorption kinetics were studied using batch adsorption experiments. SETARAM C80 calorimeter equipped with mixing vessel was then applied to determine enthalpy of adsorption. The shape of the adsorption isotherms indicated that the adsorption data could be fitted by the Langmuir adsorption model of monolayer coverage. For both coal types, practically no change in adsorption capacity of the coals to Pb(II) ions was ascertained with increasing temperature. On the other hand, practically doublefold increase in the values of adsorption rate constant k was found when temperature rises from 30 to 60°C. The interaction of lead (II) ions with the coals was then found to be slightly exothermic as confirmed direct calorimetric investigations.