[Simultaneous Recovery of Nutrients from Wastewater by Mesoporous MgO-loaded Natural Zeolital]

Using MgO modified natural zeolite (NZ-MgO) as a settling agent, nutrients from synthetic contaminated waters were recovered as a struvite precipitate. Different reaction conditions, including reagent dosage, solution pH, contact time, and coexisting calcium ions, were investigated. In order to understand the recovery mechanism, Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) were utilized to analyze the chemical composition of recovered precipitates, and Brunauer-Emmett-Teller (BET) and field-emission scanning electron microscopy(SEM) were used to detect the surface area and morphology. The results showed that NZ-MgO exhibited a strong removal capacity, with a maximum removal capacity of 119.2 mg·g^-1 for phosphate and 48.5 mg·g^-1 for ammonium nitrogen at a dosage of 0.4 g·L^-1, initial pH of 7, and contact time of 2 h. The kinetics of both phosphate and ammonia nitrogen followed the pseudo-second-order kinetic model (R²>0.99), which revealed that the chemical process occurred at the solid-liquid interface. The mechanisms for nutrient recovery by NZ-MgO were struvite crystallization, physical adsorption, ion exchange, and electrostatic attraction, with struvite crystallization being the main mechanism. Existing calcium ions would hinder the simultaneous recovery of nutrients from wastewater, resulting in a struvite decline and calcium phosphate increase.