Heavy metals sorption onto alluvial soil under various operational conditions

The removal of lead Pb⁺², copper Cu⁺² and cadmium Cd⁺² from aqueous solutions by alluvial soil (AL) as adsorbent has been investigated in a series of laboratory scale experiments under various operational conditions (solution pH, adsorbent dose, ions concentration and contact time). Characterization of AL has been carried out using infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The surface of AL beads is irregular with many spaces, channels and holes, which are helpful for mass transfer of metal ions into AL soil. The optimum ions removal can be achieved in alkaline solutions. Ions removal efficiency is directly related to contact time and adsorbant dose and inversely related to the initial ions concentration. Ion selectivity on AL followed the order of Pb⁺² > Cu⁺² > Cd⁺². The results confirm that AL can remove heavy metals from wastewater efficiently, which is a cheap and environmentally friendly adsorbent. Langmuir and Freundlich isotherms fit the experimental data perfectly. The results indicate that the adsorption of pb⁺², Cu⁺² and Cd⁺² ions is well fitted by the pseudo second-order kinetic model.