Studies of lead retention from aqueous solutions using iron-oxide-coated sorbents

In this research, experiments were conducted to study Pb2+ sorption onto engineered iron-oxide-coated sand (IOCS) and iron-oxide-coated crushed brick (IOCB), as well as onto naturally iron-oxide-coated sand (NIOCS). Optical and scanning electron microscopy (SEM) analyses were realised to investigate the surface properties and morphology of the coated sorbents. Infrared spectroscopy and X-ray diffraction techniques were also used to characterise the sorbent structures. Adsorption of lead from synthetic aqueous solutions was investigated by batch experiments. Results show that adsorption is slightly dependent on pH. The maximum adsorption capacity obtained at pH 6 was 5, 5.5 and 2.9 mg g-1 for IOCS, IOCB and NIOCS, respectively. Both Freundlich and Langmuir isotherms can describe experimental data. The influence of temperature on the adsorption process was also evaluated. Results indicated that adsorption of Pb2+ on the three sorbents is endothermic. The thermodynamic parameters (G, H and S) for Pb2+ sorption on all considered sorbents were also determined from the temperature dependence. All considered sorbents could be an alternative emerging technology for water treatment without any side effects or treatment process alterations. However, IOCB has the best performances due to its greater capacity for the retention of lead.