Phosphorus removal from wastewater using nano-particulates of hydrated ferric oxide doped activated carbon fiber prepared by Sol–Gel method

Abstract

Sol–Gel method is used to immobilize nano-particulates of hydrated ferric oxide (HFO) within macroporous activated carbon fibers (ACFs), and the phosphate removal behavior and its mechanisms of the new hybrid phosphate adsorbent named as ACF-NanoHFO are studied. The surface structure of ACF-NanoHFO is characterized by scanning electron microscopy (SEM), showing Sol–Gel method to be a reliable method for improving performances of depositing iron nano-particles on the ACF. The Freundlich and Langmuir models are used to simulate the sorption equilibrium, indicating that the Langmuir model is more suitable than the Freundlich model for well elucidation of the experimental data. The maximum adsorption capacity is calculated to be 12.86mg/g. The kinetic data from the adsorption of phosphate are discussed in a framework of the pseudo second-order model, indicating that the adsorption of phosphate is a chemisorption process. The phosphate adsorption is highly pH dependent. The coexistence of other anions in solutions has an adverse effect on phosphate adsorption. A decrease in adsorption capacity follows the order of exogenous anions, i.e., F->NO3->Cl->SO42-. The ligands exchange and electrostatic interactions are manifested to be two main mechanisms for phosphate adsorption of ACF-NanoHFO revealed by Fourier transform infrared (FT-IR) spectroscopy and change of pH values associated with the adsorption process. All the results indicate that the ACF-NanoHFO has a considerable potential for the phosphate removal from contaminated waters.