Green synthesis of CaxLa1-xMnO3 with modulation of mesoporous and vacancies for efficient low concentration phosphate adsorption

Abstract

Phosphate concentrations in eutrophic surface waters are usually low, and efficient removal of low concentration phosphate remains a challenge. In this study, Ca-doped LaMnO₃ synthesized at doping ratios, designated as Ca_xLa_1-xMnO₃ (x = 0, 0.2, 0.4, 0.7), were compared. It was found that, the adsorption capacity of Ca_0.4La_0.6MnO₃ material reached 63.01 mg/g at pH = 5, increased by 63.6% over the undoped LaMnO₃ perovskite. For long-term adsorption, Ca_0.4La_0.6MnO₃ could constantly adsorb phosphate to avoid phosphate accumulation (<0.05 mg/L). This proves that Ca_0.4La_0.6MnO₃ has the ability to control dynamic water eutrophication. Characterization and density functional theory results confirmed that Ca_xLa_1-xMnO₃ can increase the content of mesopores and oxygen vacancies, providing additional active sites. This reduces the adsorption energy of the La site, promotes electron transfer, and increases its affinity. It provides a new method for removing low-concentration phosphates.

Keywords: A-site doping; Density functional theory; Low concentration phosphate removal; Perovskite; Wastewater.