Effectiveness of native and citric acid-enriched biochar of Chickpea straw in Cd and Pb sorption in an acidic soil

Abstract

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 is frequently used by researchers for removal of some pollutants especially heavy metals is biochar of organic residues. In this research, the effect of the native and citric acid (CA) -enriched biochar of Chickpea on adsorption 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 metal adsorption mechanisms by biochar. Adsorption was mainly due to the exchange of ligands between the hydroxyl functional groups on the adsorbent to form complex with heavy metals. According to the determination coefficient (R2) and standard error (SE) obtained from the kinetic equations, the adsorption data was fitted better by Elovich equation than the first-order and pseudo-second order equations. The results of the adsorption isotherms showed that the soil treated with CA-enriched biochar had a maximum absorption capacity of 2475.7 and 12109.4 mg kg−1 for Cd and Pb, respectively. The adsorption process for Cd and Pb was well described by Langmuir and Freundlich isotherm equations (R2<0.89). The ability of modified biochar in adsorption of metals from soil was significantly more than native one. So using CA-enriched biochar for adsorption of Cd and Pb in soil is suggested.