La-based adsorbents are widely used for controlling phosphate concentration in water bodies. In order to explore the effect of different B-site metals regulating La-based perovskites on phosphate adsorption, three La-based perovskites (LaBO3, B = Fe, Al, and Mn) were prepared using the citric acid sol-gel method. Adsorption experiments showed that LaFeO3 exhibited the highest adsorption capacity for phosphate, which was 2.7 and 5 times higher than those of LaAlO3 and LaMnO3, respectively. The characterization results demonstrated that LaFeO3 has dispersed particles exhibiting larger pore size and more pores than LaAlO3 and LaMnO3. Spectroscopy analysis and density functional theory calculation results showed that different B-positions cause a change in the type of perovskite crystals. Among them, the differences between lattice oxygen consumption ratio, zeta potential and adsorption energy are the main reasons for the differences in adsorption capacity. In addition, the adsorption of phosphate by La-based perovskites were well fitted with Langmuir isotherm and pursues the pseudo-second-order kinetic models. The maximum adsorption capacities were 33.51, 12.31 and 6.61 mg/g for LaFeO3, LaAlO3 and LaMnO3, respectively. The adsorption mechanism was mainly based on inner-sphere complexation and electrostatic attraction. This study provides an explanation for the influence of different B sites on phosphate adsorption by perovskite.
Keywords: Adsorption; Density functional theory; Lanthanum based perovskites; Lattice oxygen; Phosphate.
© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.