Different procedures have been used to decrease the pollution of soil and water bodies. Among these methods,the application of adsorption technique has been studied worldwide. In recent years, a novel adsorbent which isfrequently used by researchers for removal of some pollutants especially heavy metals is biochar of organicresidues. In this research, the effect of the native and citric acid (CA) -enriched biochar of Chickpea on ad-sorption of heavy metals, cadmium (Cd) and lead (Pb) in soil was investigated. Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM) techniques were used to identify the heavy metaladsorption mechanisms by biochar. Adsorption was mainly due to the exchange of ligands between the hydroxylfunctional groups on the adsorbent to form complex with heavy metals. According to the determination coef-ficient (R2) and standard error (SE) obtained from the kinetic equations, the adsorption data was fitted better byElovich equation than the first-order and pseudo-second order equations. The results of the adsorption isothermsshowed that the soil treated with CA-enriched biochar had a maximum absorption capacity of 2475.7 and12109.4 mg kg−1for Cd and Pb, respectively. The adsorption process for Cd and Pb was well described byLangmuir and Freundlich isotherm equations (R2< 0.89). The ability of modified biochar in adsorption ofmetals from soil was significantly more than native one. So using CA-enriched biochar for adsorption of Cd andPb in soil is suggested.
