Removal of Sb(III) from wastewater by magnesium oxide and the related mechanisms

Pollution and remediation of antimony in aquatic ecosystems have been paid increasing attention. In the present work, environmentally friendly nano-MgO was used for the first time to remove Sb(III) from the water system. The batch experiments indicated that the nano-MgO calcined at 400 °C (named 400-MgO) exhibited superior adsorption capacity for Sb(III). The adsorption isotherm was fitted well with the Freundlich model, and especially when the initial concentration is 15 mg‧L−1, the adsorption capacity is as high as 140.1 mg‧g−1. Researches through X-ray diffraction (XRD), Transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS) showed that the main removal mechanisms lie in the generation of Mg active sites, which is capable of coordinating Sb(III), during the hydration process of MgO, providing a nucleation center for the progressive production of MgSb2O4. As a whole, precipitation is the predominant mechanism for MgO to remove Sb(III). Over time, a part of MgO is hydrated to Mg(OH)2, and consequent chemisorption also helps to remove Sb(III). Our work has demonstrated that nano-MgO is a promising adsorbent for Sb(III) removal from contaminated water and provided new insights into the interaction mechanism between MgO and Sb(III).