Adsorption isotherm of lead heavy metal from aqueous environment by bioadsorbents

Heavy metals are hazardous pollutants that are usually produced by industrial waste water and enter the aqueous environment. In this experiment, three doses of adsorbent, rice husk and Activated carbon, nine Initial concentrations of lead metal, three different pH and four contact times were used to remove lead ions from the aqueous environment. Investigation of the equilibrium time at different concentrations showed that with decreasing initial concentration of the solution, the time of equilibrium for both adsorbents decreased. The time of equilibrium for both adsorbents was equal and its value was 30 minutes. Investigation of adsorption efficiency at different concentrations showed that by decreasing the initial concentration of the solution, the adsorption efficiency increased for both adsorbents and get close together. The best removal of lead by two adsorbents of rice husk and activated carbon was obtained at 77.4 and 94.4%, respectively, at pH=6 and adsorbent mass=1 g/L. Activated carbon had the higher ability to lead remove from the aqueous environment. The fitting of Langmuir and Freundlich adsorption isotherm models showed that the adsorption process followed both the Freundlich and Langmuir isotherms, but the Freundlich isotherm is fitted better than the Langmuir isotherm.