Calcium ferrites for phosphate adsorption and recovery from wastewater.

ABSTRACT

In this study, calcium ferrites with different Ca Fe atomic ratios (1 1, 1 2, 1 3 and 2 1) were prepared from Ca and Fe nitrates treated at 300, 700 and 900 °C and evaluated for phosphate adsorption and recovery from wastewater. TG, XRD, Mössbauer spectroscopy, SEM, VSM magnetic measurements, and BET analyses showed the formation of two different calcium ferrite phases, i.e., CaFe2O4 and Ca2Fe2O5 at 700 and 900 °C. The adsorption results indicated that the formation of calcium ferrite structure is critical for phosphate adsorption/recovery. Evaluation of the pH, initial phosphate concentration, contact time, coexisting ions and desorption conditions showed remarkable adsorption capacities of 62-75 mg g-1 for CaFe12-700 and 28-43 mg g-1 for CaFe12-900. The phosphate adsorption on the Ca ferrite surfaces is so strong that the recovery/desorption showed limited efficiencies, e.g., 15-39%.