Composites hybridized with Ca(OH)2 and LaMnO3 synergistically improve phosphate adsorption properties

Phosphate loading is an important factor in the deterioration of freshwater ecosystems. La-based perovskites, a new type of adsorbent material, suffer from low phosphate adsorption performance and are highly affected by pH. Hence, the construction of materials with high phosphate adsorption performance over a wide pH range for phosphate removal is a challenge. In this study, Ca(OH)2-hybridized LaMnO3 perovskite composites (Cax–LMO, x = 0, 0.2, 0.4, 0,7) were prepared by impregnating different ratios of CaO on LaMnO3. Isothermal, kinetic, and influential factor tests showed that the maximum phosphate adsorption capacity of Ca0.4–LMO for phosphate reached 101.1 mg P g−1, which was 1.14 times higher than that of the original Ca0–LMO. The phosphate adsorption capacity of Ca0.4–LMO was minimally affected by pH and only decreased by 17.8% with increasing pH. Therefore, the synergistic effect of Ca(OH)2 and LaMnO3 improved the performance of the material for phosphate adsorption over a wide pH range. In the experiments using three types of real wastewater, the removal rate of Ca0.4–LMO reached 99.6% for high-concentration cattle farm wastewater. Quantitative removal was realized for low-concentration pond wastewater and the effluent of sanitary wastewater, revealing high efficiency in removing phosphate from real water bodies. After eight adsorption–desorption cycles, the phosphate removal rate of Ca0.4–LMO remained up to 96%, proving its reusability. Characterization results showed that the phosphate adsorption process was mainly chemisorption, and the adsorption mechanisms were ligand exchange, inner-layer complexation, and electrostatic attraction. This study provides a new approach for improving the phosphate adsorption performance of La-based perovskites for phosphate removal over a wide pH range.