Abstract

The problem of removing pollutants from aqueous wastewater is growing with the increase in water pollution owing to enhanced industrial activities. Three earthworm cast soil types were studied. Modified and unmodified types were prepared and used for removal of lead and Chromium ions. At about 298 K, the earthworm cast soil types, modified and unmodified removed lead and Chromium ions from aqueous solution. Both equilibrium and dynamic sorption experiments showed that physically and chemically modified earthworm cast soils removed lead and chromium ions better than the unmodified form. The equilibrium data fitted well into Langmuir and Freundlich isotherms. The unmodified earthworm cast soil with a dynamic equilibrium constant, K_c of 266 performed better in Lead (II) ion removal than chromium (VI) ion with a dynamic equilibrium constant of 4 at 298 K. ΔG°, the standard free energy change of adsorption of Pb²⁺ and Cr⁶⁺ onto unmodified earthworm cast soil is negative which implied spontaneity and feasibility of adsorption process. The cheapness and the local availability of this soil type give it an added advantage for effluent treatment in heavy metals removal in the environment.

Key words: Earthworm cast soil, equilibrium and dynamic adsorptions, heavy metals, effluent, langmuir and freundlich isotherms.