Recovery of phosphate using Zn/La nanoflowers prepared by co-precipitation in water

Abstract

Phosphorus is widely used in industries such as chemical fertilizers, batteries, metal surface treatment, plastics and semiconductors. However, the amount of phosphate rock mining is increasing by 2% every year, and the issue of depletion is continuously raised, and it is predicted that it will be exhausted within the next 100 years. Therefore, interest in resource recovery and reuse is increasing for the continuous use of resources that are about to be exhausted. In this study, zinc oxide/hydroxide(ZnO/Zn(OH)2) with excellent stability and lanthanum hydroxide (La(OH)3) with high adsorption efficiency for phosphorus were synthesized by co-precipitation and low cost and high efficient Zn/La nanoflowers (ZLNFs) were prepared. It was confirmed that the phosphate adsorption efficiency (73.2%) of ZLNFs developed under optimal synthesis conditions was 32.2% better than that of pure ZnO/Zn(OH)2 nanoflowers (41%). The characteristics of ZLNFs according to the Zn/La molar ratio and preparation temperature were investigated. The Zn/La molar ratio affected the specific surface area and adsorption performance of nanoflowers, and the fabrication temperature was related to the morphology of ZLNFs. Field emission scanning electron microscopy/energy dispersive spectroscopy (FESEM/EDS), X-ray diffraction analysis (XRD), BET surface area, zeta potential, Fourier transform infrared spectroscopy (FT -IR) and X-ray photoelectron spectroscopy (XPS) were analyzed to investigate the material properties, adsorption capacity, and adsorption/desorption mechanism of ZLNFs. Phosphate adsorption was highly dependent on the pH of the solution, and the maximum adsorption efficiency was shown at pH 3. The phosphate adsorption characteristics of the developed material were evaluated using an isothermal adsorption model, kinetic and thermodynamic models. As a result, it was confirmed that the Langmuir and pseudo-second-order models were most suitable, and phosphate adsorption on ZLNFs was a monolayer homogeneous adsorption process, and chemical adsorption was dominant. In addition, the Langmuir theoretical maximum adsorption capacity was 178.6 mg P/g, which was excellent compared to other materials in previous studies. The results of this study are expected to be very useful in the field of water quality management.