A comparative study for lead removal by pure calcite and a natural calcitic soil sample
The extent of removing toxic lead ions (Pb2+) from aqueous solutions was investigated using pure calcite and natural calcitic soil, one of the globally available soils, as efective inorganic adsorbents. The rate of adsorption of Pb2+ ions on pure calcite is much faster than that on the soil sample due to the presence of other metal ions on its surface, which block the active sites and retard the adsorption process. The order of adsorption on the soil was a frst-order reaction with respect to Pb2+ ions. The rate constant was calculated to be 0.1 min−1. The half-life time of the adsorption of Pb2+ ions on soil was calculated to be 6.9 min at 25 °C. The adsorption process on both solids fts well with the Langmuir isotherm but does not ft well with the Temkin or Freundlich isotherms. Maximum adsorption capacities were calculated from the Langmuir isotherm as 156 mg/g calcite and 74 mg/g soil at 25 °C.