Valorisation of romanian peat for the removal of some heavy metals from aqueous media

Abstract

In this study, the sorption of some potential toxic heavy metal ions (Pb(II), Hg(II) and Cd(II), respectively) onto Romanian peat was investigated as a function of initial solution pH, sorbent dose, initial metal ions concentration and contact time, at room temperature (20 ± 0.5°C), in batch system. The uptake capacity of tested heavy metals decreased by decreasing the initial solution pH, suggesting that competition exists between hydrogen ions, present in high concentration in strong acid media and metal ions. The experimental data were evaluated using Langmuir and Freundlich isotherm models. The isotherm data followed the Langmuir model, and the maximum sorption capacity increases in the order Cd(II) < Pb(II) < Hg(II). The kinetics of metal ions sorption was rather rapid, with at least 68% of sorption occurring in 30 min. The experimental data were satisfactory correlated with pseudo-second-order kinetic model, which means that in the sorption mechanism the chemical interaction between positively charged metal ions and negatively charged functional groups from peat surface is the rate-controlling step. The results presented in this study showed that the Romanian peat could be used as a potential cost-effective sorbent for the treatment of complex aqueous media containing heavy metals.

Keywords:

• Sorption
• Heavy metals
• Romanian peat
• Isotherm
• Kinetics

Acknowledgements

This paper is part of the project PNCDI II No. 51045/2007 supported by Romanian Education and Research Ministry.