Changes in the State of Organic Matter Present in Sediment by Different Methods of Electrokinetic Treatment

抄録

During sedimentation, organic matter is absorbed on metal ions or clay minerals (soil particles), affording metal complexes that are difficult to use as organic materials. Hence, it is critical to separate the organic matter from metal or clay mineral complexes, possibly leading to the effective use of sediment and agriculture soils. Previously, a solar cell-combined sediment microbial fuel cell, constituting one of electrokinetic treatments, was applied into the sediment. As a result, metal complexes in the sediment were found to be dissociated, leading to changes in the state of organic matter present in the sediment. In this study, a new perspective into the changes in the state of organic matter by different methods of electrokinetic treatment was reported. In laboratory experiments, the sediment was subjected to different methods of electrokinetic treatment. Positive current was conducted for the transfer of electrons from the sediment to water, i.e., electron recovery. On other hand, negative current was conducted for the transfer of electrons into the sediment, i.e., electron supply. Thermogravimetric analysis (TG-DTA) and Fourier infrared (FTIR) spectral analysis of each sediment were carried out at the end of experiments. TG-DTA results revealed that the mass loss on ignition increases compared to the control sediment due to electron recovery, indicative of the release of organic matter. However, a difference was not observed with electron supply. FTIR results suggested that changes in the state of organic matter are the same for electron recovery and electron supply, i.e., release of O-H hydroxyl and C=O carboxylic acid groups were confirmed. Notably, by supplying electrons after electron recovery, the losses of O-H hydroxyl and C=C aromatic groups from the sediment were confirmed. Clearly, different states of organic matter were obtained by changing the method of electrokinetic treatment.