Facile synthesis of novel 3D flower-like magnetic La@Fe/C composites from ilmenite for efficient phosphate removal from aqueous solution

Abstract

In this study, a novel 3D flower-like La@Fe/C magnetic composite was successfully synthesized by carbothermal reduction of ilmenite via microwave radiation. The physico-chemical properties of the composite were investigated. The results showed that La@Fe/C features a 3D flower-like morphology with an S_BET and V_mic of 114 m² g⁻¹ and 0.017 cm³ g⁻¹, respectively. Zerovalent iron and metal oxides were detected by XRD and XPS on the surface of the adsorbent, which formed as a result of carbothermal reduction of ilmenite using coconut shell-based carbon followed by the introduction of lanthanum. This resultant magnetic La@Fe/C exhibited remarkable phosphate selectivity performance even in the presence of a 50-fold excess of competing ions, which is superior to the pristine ilmenite and coconut activated carbon. Adsorption isotherms and adsorption kinetics fitted well with the Langmuir model and pseudo-second-order model, respectively. A thermodynamic study indicated that the adsorption of phosphate was spontaneous and endothermic. The adsorption–regeneration cyclic experiments of the La@Fe/C composite demonstrated a good level of recyclability. These results indicated that carbothermal reduction of ilmenite followed by the introduction of lanthanum could result in highly efficient and recoverable magnetic particles for the removal of phosphate from wastewater.