Magnetic lanthanum-modified ball-milled steel slag encapsulated alginate composite hydrogel beads for low-level...

In this study, a designed lanthanum-modified ball-milled steel slag encapsulated alginate composite hydrogel beads (La@BS-SA) was prepared as a novel phosphate scavenger by a facile cross-linking method. The synthesized La@BS-SA beads exhibit robust phosphate adsorption performance in wide pH range of 3.0 to 9.0. Additionally, the composite hydrogel beads demonstrate efficient regeneration across five adsorption-desorption cycles and in practical wastewater treatment applications. The optimal conditions for achieving near-complete phosphate removal were identified as a pH level of 3.0, an adsorbent dosage of 1.0 g/L, a temperature of 298 K, a contact time of 360 min, and an initial phosphate concentration of less than 10.0 mg/L. The adsorption process was found to conform to the pseudo-second-order kinetic model and the Freundlich isotherm model, while thermodynamic analysis indicated that the process was spontaneous and endothermic in nature. Furthermore, the maximum adsorption capacity of La@BS-SA for phosphate has been determined to be 58.36 mg P/g. Moreover, the results obtained from scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectra, and X-ray photoelectron spectroscopy (XPS) analyses suggest that the enhanced phosphate removal efficiency of La@BS-SA can be primarily attributed to mechanisms such as electrostatic attraction, ligand exchange, and inner-sphere complexation.