Removal of Heavy Metals (Cd and Pb) from Contaminated Soil by Amorphous Al and Fe Hydroxides

Ahmed Marzoog; Rana R. Al-Ani; Abdul Hameed Mohammaed Jawad Al-Obaidy; Dhuha Jawad Mahdi; Mohammed Muayad TA

Ahmed Marzoog Department of Soil and Water Sciences, College of Agriculture, University of Anbar, Al-Anbar-31001, Iraq
Rana R. Al-Ani Environment Research Centre, University of Technology-Iraq, Baghdad-10001, Iraq
Abdul Hameed Mohammaed Jawad Al-Obaidy Civil Engineering Department, University of Technology-Iraq, Baghdad-10001, Iraq
Dhuha Jawad Mahdi Studies and Planning Department, University of Technology-Iraq, Baghdad-10001, Iraq
Mohammed Muayad TA Environment Research Centre, University of Technology-Iraq, Baghdad-10001, Iraq and also Studies and Planning Department, University of Technology-Iraq, Baghdad-10001, Iraq

Keywords: soil contamination, heavy metals, chemical remediation, immobilization, metal oxides, organic ligands

Abstract

The sorption/desorption properties of heavy metals (Cd and Pb) on synthetically prepared amorphous Al and Fe hydroxide in the absence and presence of low (citrate) and high (tannate) molecular weight organic ligands from heavy metal-polluted soils were investigated in this work. The sorption kinetics and desorption of Cd and Pb have also been investigated. Four soil samples were collected from contaminated locations in Egypt: Abo-Rawash and El-Gabal El-Asfer, Mostorod and Shubra. The depth of collected samples is (0-30) cm. According to the results, all of the immobilizing agents tested have a cation exchange capacity of 31.3 to 67.8 C mol(c)Kg. In addition, the prepared amorphous hydroxides demonstrated Cd and Pb adsorption capability and retention of the adsorbed metal. The tested immobilizing agents (Fe-citrate and Al-tannate) show a high adsorption capability for Cd. The highest adsorption capacities of Al-tan and Fe-cit were 2.269 and 5.665 g/Kg, respectively. The tested immobilizing agents might be grouped in descending order based on their maximum adsorption capacity: Fe-cit. > Al-tin. The adsorption affinity (binding energy) between immobilizing agents and Cd ranged from 0.062 to 0.063. Fe-cit received the highest value (0.063), while Al-tan received the lowest one (0.062). Immobilizing agents (Fe-cit. and Al-tan.) have maximal adsorption capacity for Pb ranging from 2.5 to 5.0 g/Kg. Fe-Cit., like Cd, had the highest maximal adsorption capabilities, whereas Al-tan had the lowest. The tested immobilizing agents could be grouped in the following order, descending in Pb maximum adsorption capacity: Fe-cit. > Al-tan.