Adsorption characteristics of Fe(III) and Fe(III)-NTA complex on granular activated carbon

The adsorption of Fe3+ ion on granular activated carbon has been studied in kinetic and equilibrium conditions taking into account the adsorbate concentration, temperature and solution pH as major influential factors. In addition, the effect of nitrilotriacetic acid on adsorption reaction as a complexing agent has been examined. Kinetic studies showed that the adsorption rate was increased as the initial Fe3+ concentration was raised. The adsorption reaction was estimated to be first-order at room temperature. The adsorption rate and equilibrium adsorption of Fe3+ increased as the temperature rose. The activation energy for adsorption was approximately 2.23 kJ mol(-1), which implied that Fe3+ mainly physically adsorbed on activated carbon. Coexistence of nitrilotri acetic acid with Fe3+ resulted in a decrease of equilibrium adsorption and the extent of decrease was proportional to the concentration of nitrilotri acetic acid. In the presence of nitrilotri acetic acid, the adsorbability of Fe3+ decreased with pH. However, the trend was reversed in the absence of nitrilotriacetic acid. When activated carbon was swelled by acetic acid, the specific surface area was increased and maximum swelling was achieved at approximately 48 h of swelling time. Thermodynamic parameters such as DeltaGdegrees, DeltaHdegrees and DeltaSdegrees for adsorption reaction were estimated based on equilibrium data and in connection with these results the thermodynamic aspects of adsorption reaction were discussed. (C) 2003 Elsevier B.V. All rights reserved.