CHEMICAL MODIFICATION OF THERMALLY TREATED PEAT FOR REMOVAL OF HEAVY METALS IN EFFLUENTS

抄録

The extent of removal of Cd(II) by natural peat available in Muthurajawela, Sri Lanka, is very low, suggesting the need for its modification to enhance the interaction ability towards this metal ion. However, thermal modification does not lead to a significant improvement of Cd(II) removal, indicating that the organic matter and other surface functionalities present in peat do not contribute to the removal of Cd(II). Interestingly, chemical modification of peat (fired at 200 °C) performed by treatment with nitric acid is able to improve the transfer of Cd(II) from the solution phase to the solid peat phase. During acid treatment, it is expected that protonation of surface functional groups of the adsorbate, such as carboxyl (COOH) and hydroxyl (OH), and solubilisation of metal complexes and metal oxides occur, promoting the extent of interaction. The optimum values of stirring time, settling time, firing temperature and the strength of the acid for Cd(II) - peat interaction are 5 min, 75 min, 200 °C and 2.0 mol dm^-3, respectively.