Insights into efficient removal and mechanism for ammonium from aqueous solution on tricalcium aluminate

Ammonium (NH4+) has been causing severe environmental pollution while the development of material with high capacity for ammonium removal remains a challenge. Herein, the cement-based material tricalcium aluminate (C(3)A) was employed to remove NH4+ from digested piggery wastewater. The conditions influencing the removal capacity were investigated, including contact time, initial ammonium concentration, temperature, dosage and initial co-existing phosphate concentration. The physicochemical structure of C(3)A and the resultant were characterized by X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FT-IR), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and N-2 adsorption-desorption isotherms. The maximum removal capacity of NH4+ by C(3)A was 155.4 mg.g(-1) at 298 K. The characterization revealed that the resultant was CaAl-Cl-LDH. The hydroxyl groups and Al(OH)(4)(-) from the C(3)A hydration played an important role in ammonium removal. High alkalinity could enhance the removal capacity. This work presents an efficient solution for ammonium removal, thus providing new insight into the mechanism of cement-based materials for water pollutant removal.