Phosphate Removal of Expanded Graphite Loaded with Ferric Hydroxide

Abstract:

The expanded graphite loaded with ferric hydroxide (EGFeOH) is prepared successfully. Its most suitable synthesis conditions are 0.26mol/L of ironic concentration and 100min of immersion time, respectively. The Langmuir model and the pseudo secondorder model are more suitable for well elucidation of the experimental data, indicating that the adsorption of phosphate is a monolayer chemisorption process. The positive ΔHΘ and negative ΔGΘ indicate that the process of phosphorus adsorption onto EGFeOH is spontaneous and endothermic. It is favorable for the phosphorus adsorption with the rising of temperature to some extent. EGFeOH performs excellently for phosphate adsorption in low concentration (5 mg?L-1). The ion exchange and lewis acidbase interactions are manifested to be two main mechanisms for phosphate adsorption of EGFeOH revealed by Fourier transform infrared (FTIR) spectroscopy and change of pH values associated with the adsorption process. The EGFeOH after adsorption is also recovered using sodium hydroxide (NaOH).

Key words:expanded graphite; iron hydroxide; phosphorus removal; adsorption; mechanism