Characterizing the impact of MnO2 on the efficiency of Fe0-based filtration systems

Significant research has been conducted on the design of filtration systems containing metallic iron for environmental remediation (Fe-0 walls) over the past 20 years. However, limited information exists on the rationale for sustainable Fe-0 walls. Additionally, very limited research has been conducted on the modification of the efficiency of the system by the addition of solid phases. This research aimed at characterizing the impact of reactive natural manganese oxides (MnO2) in influencing the extent of methylene blue (MB) discoloration by a Fe-0/sand system in gravity driven column experiments. A total of seven columns were used in parallel experiments. Investigated systems are: pure Fe-0, pure sand, Fe-0/sand mixture and four different Fe-0/MnO2/sand mixtures. The volumetric ratio of Fe-0 in hybrid systems was 30%. In three-components-systems, the volumetric ratio of each additive was 35%. Each system was characterized by the time-dependent evolution of the pH value, the iron and MB breakthrough, and the evolution of the hydraulic conductivity (permeability). Results showed enhanced MB discoloration in all Fe-0/ MnO2/sand systems relative to the Fe-0/sand system. The impact of MnO2 on system's permeability could not be accessed because of the poor mechanic properties of tested minerals. However, the Feasibility of sustaining the efficiency of Fe-0 walls by admixing granular MnO2 is demonstrated. This tool will help in the development of more sustainable Fe-0 walls. Such systems could also lead to substantial improvement of drinking water supply and wastewater treatment in the developing world. (C) 2014 Elsevier B.V. All rights reserved.