Study on the removal of iron and manganese in groundwater by granular activated carbon

One of the problems related to groundwater is the reddish colour caused by the presence of ferrous and manganese. Initially, this colour cannot be seen but after it has been exposed to the air, the oxidation of groundwater will promote the precipitation of ferrous and manganese. Eventually, the groundwater turns into reddish in colour. Batch test had been carried out to determine the potential and the effectiveness of granular activated carbon (GAC) in removal of ferrous and manganese from water. The test was conducted by mixing certain amount of GAC with 200 mL sample solution and shook for 6 h in room temperature to achieve an equilibrium. The two most common adsorption equations, Freundlich and Langmuir adsorption isotherms, were used in the study to verify the adsorption performance. From interpretation of the equations, the Langmuir adsorption isotherm was found to fit the experimental data better than that of the Freundlich adsorption isotherm. This shows that the relatively high ambient temperature allowed only monolayer adsorption to occur between the adsorbate and adsorbent. According to Langmuir adsorption isotherm's assumption, the bonding that was established between the adsorbent and adsorbate are chemically bonded which known as chemisorption. In this study, the adsorption capacity of Fe(II) and Mn(II) were 3.6010 and 2.5451 mg/g, respectively. Therefore, the adsorption capacity for Fe(II) was higher than Mn(II). The main factors that contribute to difference adsorption capacity of Fe(II) and Mn(II) onto GAC are due to ionic radius and electronegativity of metal ions.