A new approach to modification of an agro-based raw material for Pb(II) adsorption

This paper describes a relatively new and effective modification with thiourea of an agro-based raw material, sorghum biomass for adsorption of Pb(II) ions. The modification was done under microwave irradiation. Changes in characteristics of modified material were determined by FT-IR and CHNS analysis. Effect of adsorbent dosage, contact time, solution pH and temperature on equilibrium process was extensively studied. Famous equilibrium models (Langmuir, Freundlich, Temkin, Dubinin-Radushkevich) in non-linear fashion were applied to evaluate the equilibrium data using different initial concentrations of Pb(II) ranging from 20 mg/L to 300mg/L. The adsorption process followed the pseudosecond-order kinetics. This paper also discusses the thermodynamic parameters (free energy, enthalpy and entropy) and reveals that the adsorption process is spontaneous. An appreciable increase in adsorption capacity of the modified adsorbent was observed, depicting the advantages of thiourea modification of sorghum biomass under microwave irradiation.