Permanganate electromigration in low permeability media / by Daniel James Hodges

2010

A series of laboratory experiments were carried out to transport permanganate through a low permeability media using electrokinetics. During the undertaking of the laboratory experiments it was realised that a critical component of successful permanganate transport was the isolation of H+ and OH- electromigration. Both H+ and OH- were generated, and underwent subsequent electromigration, as a result of applying electrokinetics. The effect of H+ and OH- electromigration was to stall the permanganate electromigration front. To undertake the laboratory experiments, an electrokinetic apparatus was designed, manufactured and implemented. H+ and OH- electromigration were used to determine the adequacy of the designed apparatus for pH isolation. A series of ‗pH-isolated‘ and ‗normal‘ mode (non pH isolated) experiments were undertaken and compared in terms of H+ and OH- electromigration. It was found that pH isolation was achieved when a combination of separating the electrode reservoirs from the inner reservoirs using porous media as well as the purging of the electrode reservoirs with a pH neutral fluid was used. The electromigration retardation factor of H+ and OH- was calculated for the porous media using the observed pH breakthrough times. The retardation factor for H+ was also calculated by considering mass flux data. The retardation factors for H+ and OH- were found to be 28.3 and 95, respectively, when using the breakthrough time. The retardation factor for H+ was calculated to be 36.7 using the mass flux data. The electrokinetic apparatus was then utilised for permanganate electromigration through low permeability porous media.

It was found that by utilising a pH-isolation technique, whereby electrolysis reactions occurring at electrodes were isolated, uniform and repeatable MnO4- electromigration was achieved. This result was compared with ‗normal‘ mode experiments, which allowed H+ and OH- electromigration to occur unmitigated, where it was found that the MnO4- electromigration front would stall part way through the porous media. Investigation into stalling mechanisms, including voltage gradient and formation of Mn2+, were assessed. It was found that the voltage gradient decreased as a result of the stalling, however it was not considered a cause of the stalling. Results from Mn2+ analysis determined that the Mn2+ distribution for 'normal' mode experiments extended partially beyond the extent of MnO4- electromigration; however the analysis suffered interference from other ions present in the porous media. Ultimately, the 'pH-isolated' experiments described through this research provide a simple method for implementing electrokinetic in-situ chemical oxidation as a groundwater remediation technique where low permeability porous media exists.

Thesis (M.Eng.Sc.)--University of Western Australia, 2011

http://repository.uwa.edu.au:80/R/-?func=dbin-jump-full&object_id=30992&silo_library=GEN01