Efficient uptake of phosphorus from water by core@shell bimagnetic nanoadsorbents

Core@shell bimagnetic nanoparticles (CoFe2O4@gamma-Fe2O3) were used as novel nanoadsorbents for phosphorus removal from water. The soft magnetic gamma-Fe2O3 shell confers adsorption capacity and long-term chemical stability while the hard magnetic CoFe2O4 core allows material separation and recovery with magnetic harvesting. Samples of two different mean sizes were elaborated and characterized by XRD, TEM, FAAS, FTIR, BET, zetametry and SQUID magnetometry. Batch adsorption tests were performed to investigate the influence of pH, contact time, initial phosphorus concentration, temperature and presence of coexisting ions on the adsorption performance. The adsorption data were best fitted by Freundlich model suggesting multilayer adsorption. The kinetics of the process followed the pseudo-second-order model with an equilibrium time of 2 h. The maximum adsorption capacity was found to be 71.2 mg g(-1) (smaller size) and 46.9 mg g(-1) (larger size) at pH = 2.0. The process was spontaneous, endothermic and showed increased randomness. Regeneration experiments yielded optimal material reusability. The nanomaterials revealed high selectivity for phosphorus and kept a high adsorption capacity in real wastewater samples. The whole of these findings highlights the promise of the proposed magnetic nanoadsorbents in phosphorus removal from water and provide important information regarding their applicability in large-scale setups.