Permeability Loss in Soil Due to Ferrous Iron Precipitation

In this project, the potential of ferrous iron precipitation as an alternative for ground improvement applications is investigated. This study analyzes the potential of naturally occurring iron oxidation, which uses Fe2+ as an electron donor to produce Fe3+ precipitate. The goal of this study was to stimulate or accelerate the naturally occurring iron oxidation and precipitation process, to form a ferruginous crust in the subsurface, that would reduce hydraulic conductivity or increase soil strength. Iron precipitation can occur through aerobic or anaerobic iron oxidizers. Initial experimental test results in falcon tubes and a literature review showed that to obtain significant oxidation of ferrous iron and consequent precipitation of iron minerals required a buffer to prevent acidification. Experimental studies in which aerobic and anaerobic iron precipitation is stimulated in sand columns under various boundary conditions also leads to an optimization of conditions for mineralization. Mineralized zones are evaluated via permeability loss tests, extent of iron oxidized and characterization tests which show that the crust has the most concentration of precipitated iron, which can be used in targeting pollution mitigation, erosion control, etc. The results show a significant loss of permeability- by a factor of two, in high concentration of iron with a balanced buffer control. In this study, the knowledge on ground stabilization by studying the naturally occurring mechanism of iron precipitation, leading to possible industrially relevant geotechnical applications are successfully investigated.