Characteristic Study of Physical and Chemical Properties of Limestone Subjected to Adsorption of Fe and Mn in Groundwater

Understanding the characteristic of adsorbent media is important to assess their compositions, particle size, morphology and the functional group. In this study, limestone was selected as adsorbent media in removing iron (Fe) and manganese (Mn) in groundwater. The characteristic of limestone was analysed using XRD, XRF, FTIR, FESEM and surface area analyser. Analysis on minerals composition detected that limestone that has been used in this study contain major portion of CaCO₃ (97.91%) and can be classified as high purity limestone. Based on the FTIR analysis of the raw limestone, it shows that the presence of hydroxyl group with O–H stretching is a favourable group of Fe and Mn adsorption. In addition, some crack between calcites connection and voids were found on the SEM image of raw limestone sample. Comparatively, the surface morphology of limestone after adsorption process presented that more crystal grains (ferrihydrite particle) were completely covered to the surface of limestone. A new manganese oxide (MnO_x) also appeared at 585 cm⁻¹ through Mn stretching, proving the occurrence of Mn adsorption process in groundwater. Therefore, limestone has the capability to remove Fe and Mn for groundwater and provide good filter media for heavy metal groundwater treatment. Due to the superior characteristic of limestone, this media offers a good alternative for Fe and Mn removal in groundwater.