Fe0 and Fe0 fully covered with Cu0 (Fe0 + Fe/Cu) in a fixed bed reactor for nitrate removal

Abstract

To develop a cost-effective, feasible and robust technology for nitrate removal by chemical degradation, a Fe⁰ and Fe⁰ fully covered with Cu⁰ (i.e., Fe⁰ + Fe/Cu) fixed reactor was set up in this study. The performance and mechanism of the Fe⁰ + Fe/Cu system for nitrate reduction were investigated thoroughly. First, the initial pH of the solution and the mass ratio of Fe⁰ and Fe/Cu (i.e., M(Fe⁰)/M(Fe/Cu) ratio) in the medium materials were optimized, and then two control experiments (Fe⁰ + quartz sand system and Fe⁰ + Cu⁰ system) were set up to confirm the superiority of the Fe⁰ + Fe/Cu system. The results suggest that high NO₃⁻–N removal (>99.0%), K_obs (0.403 min⁻¹) and low NH₄⁺–N generation rate (61.1%) could be obtained by the developed system (Fe⁰ + Fe/Cu) with a short hydraulic retention time (HRT = 16 min). In addition, the operational life of the Fe⁰ + Fe/Cu system and Fe⁰ + quartz sand system were investigated comparatively, which shows that the operational life of the former was much longer than that of the latter. Finally, characteristics of the medium materials in the Fe⁰ + Fe/Cu system and Fe⁰ + quartz sand system were also observed by scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) before and after long-term operation. Therefore, the developed system in this study is a promising technology for nitrate contaminated water treatment.