Struvite crystallization combined adsorption of phosphate and ammonium from aqueous solutions by mesoporous MgO-loaded diatomite

Mesoporous magnesium oxide modified diatomite (MgO-D) was developed through a simple precipitation method, and applied for simultaneous removal of nutrients from contaminated waters. Different adsorption conditions including adsorbent dosage, solution pH, contact time and coexisting substances were investigated. MgO-D exhibited a high removal capacity in a wide pH range of 3-9 with the maximum removal capacity of 160.94 mg g(-1) for phosphate and 77.05 mg g(-1) for ammonium at initial pH of 7, adsorbent dosage of 0.3 g(-1). The adsorption kinetics followed the pseudo-second-order kinetic model corresponding to a chemisorption process. Characterization of adsorbents by X-ray diffraction (XRD), field-emssion scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) before and after adsorption revealed that struvite crystallization, physical adsorption, and electrostatic attraction contributed to the removal process. The results illustrated that MgO-D could be used as an efficient and environmental adsorbent for simultaneous nutrients removal. (C) 2016 Elsevier B.V. All rights reserved.