Facile synthesis of novel tremella-like Mn0@Mn2O3 and its exceptional performance on removal of phosphate

Abstract

Phosphorus is an essential nutrient for biological growth, but its excessive presence in water can lead to eutrophication. Reducing phosphorus concentrations is an important way to prevent eutrophication of surface water bodies. In this study, a novel zero-valent manganese (ZVM) Mn0@Mn2O3 sorbent was synthesized via a facile one-step reduction method at ambient temperature. The morphology and surface properties of the Mn0@Mn2O3 were analyzed by Scanning electron microscopy (SEM), X-ray diffraction (XRD), Zeta potential analyzer, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The obtained amorphous sample consists of many small tremella-like particles. The as-prepared sorbent shows exceptional phosphate removal performance and has a maximum adsorption capacity of 113.7 mg-P/g at pH 7.0, superior to many reported adsorbents. The removal of phosphate is obviously pH-dependent and is favorable under near-neutral and weak-alkaline conditions (pH 6.5–8.5). The kinetics data fit well to the pseudo-second-order model. The coexisting SO42-, CO32- and Cl- have no great influence on phosphate sorption, whereas, the SiO32- shows negative effect at high concentration. The sorbent is effective for phosphate removal from real municipal wastewater. The results of ionic strength effect experiment, SEM, XRD, FTIR and XPS analyses reveal that the phosphate was mainly removed through surface precipitation and formation of inner-sphere surface complexes. The Mn0@Mn2O3 is a promising sorbent for phosphate removal from surface water and wastewater, owning to its exceptional performance, high selectivity, environmental friendliness and easy preparation.