The removal of Co2+, Ni2+, and Pb2+ from aqueous solutions using a modified zeolite was investigated because of the need to eliminate toxic contaminants from wastewaters. In the present study the ways in which equilibrium, thermodynamics, and kinetics parameters affected the removal of heavy metals were evaluated and compared. An Iranian clinoptilolite with a Si/Al ratio of 6.5 was used as an adsorbent. In order to increase the adsorption capacity of the adsorbent, it was converted to a manganese oxide-coated zeolite (MOCZeo) using various Mn solutions. The initial concentration of metals, pH, contact time, and temperature were the variables studied and optimal conditions were established. The maximum amount of Co2+, Ni2+, and Pb2+ adsorption on MOCZeo was ascertained. A thermodynamics study, using ΔG, ΔH, and ΔS state functions showed that adsorption of Pb2+ was more spontaneous than that of Co2+ and Ni2+ ions. The adsorption of these ions on MOCZeo was an endothermic reaction. Investigation of the adsorption models revealed that the adsorption of Pb2+, Co2+, and Ni2+ on MOCZeo followed both the Langmuir and Freundlich models. Kinetics studies showed that the adsorption of Pb2+, Co2+, and Ni2+ on MOCZeo followed the pseudo-second order kinetics model with a high correlation coefficient.