The aim of this study was to investigate the role of MgO on the long-term operation of a mixed media contactor. Specifically, the simultaneous removal of aqueous manganese and the remineralization of soft waters using pure calcite are limited by a remineralization breakthrough after 600 h of operation in the presence of high Mn concentrations (5 mg Mn/L). The introduction of as little as 5 % (m/m) MgO was able to improve the Mn removal kinetic, while maintaining remineralization objectives over 720 h of operation. After treating elevated concentrations of Mn, both media exhibited a Mn-coated layer which contributed to limiting the mass transfer from the media core to the liquid phase. X-ray photoelectron spectroscopy (XPS) identified this superficial layer as 10 % Mn oxides (MnOx) on MgO media compared to 1.4 % MnOx on calcite, suggesting the MgO acts as the preferred reaction surface during Mn removal. Therefore, it is postulated that in the presence of MgO, Mn removal is impacted by high pH conditions (pH = 10.5) which introduces a significant precipitation mechanism as Mn²⁺ is oxidized. For all the examined conditions, the formation of this coating improved Mn removal due to the autocatalytic nature of the adsorption/oxidation of dissolved manganese by MnOx. MgO is therefore thought to contribute to a complex sorption-coprecipitation process in the operation of a mixed media contactor.

本研究的目的是研究 MgO 在混合介质接触器长期运行中的作用。具体来说，使用纯方解石同时去除水锰和软水再矿化受到在高锰浓度（5 mg Mn/L）存在下运行 600 小时后再矿化突破的限制。引入低至 5% (m/m) 的 MgO 能够改善 Mn 去除动力学，同时在 720 小时的运行时间内保持再矿化目标。在处理高浓度的 Mn 后，两种介质都显示出 Mn 涂层，这有助于限制从介质核心到液相的质量传递。X 射线光电子能谱 (XPS) 将此表面层鉴定为 MgO 介质上的 10% Mn 氧化物 (MnOx)，而方解石上的 MnOx 为 1.4%，表明 MgO 在 Mn 去除过程中充当了优选的反应表面。因此，假设在 MgO 存在下，Mn 的去除受到高 pH 条件（pH = 10.5）的影响，这引入了显着的沉淀机制作为 Mn²⁺被氧化。对于所有检查的条件，由于 MnOx 对溶解的锰的吸附/氧化的自催化性质，该涂层的形成改善了 Mn 的去除。因此，MgO 被认为有助于混合介质接触器操作中的复杂吸附-共沉淀过程。