Electrokinetic soil remediation by electroosmosis and ionic migration is restricted to soluble substances. At a higher pH, the soil particles sorb more heavy metals, such as cadmium, than at a lower pH and the precipitation reactions of heavy metals are promoted. Both mechanisms make heavy metals immobile, rendering cleanup more difficult and electrokinetic extraction inefficient. Therefore, the acidification of soils is very important to increase the cleanup efficiencies of heavy metals, such as cadmium by electrokinetic method from contaminated soils. Meanwhile, hexavalent chromium is more mobile and easily soluble. Hexavalent chromium has high solubility in water and exists as chromate, monochromate or dichromate anions depending on the pH of the solutions. This hexavalent chromium is the chemical form requiring remediation. In this study, cadmium and hexavalent chromium transport are predicted with a simple numerical method in which electrical flow is coupled with hydraulic flow, and the sorption process in the soils is induced in the model. The effects of some factors such as electrode configuration, electric field strength and electrode spacing for saturated soils are investigated using this numerical model. The results obtained this study are summarized as follows: The two-dimensional electrode configurations containing cathode surrounded by three or more anodes rapidly remove cadmium from soils compared with one-dimensional electrode configuration. Meanwhile, in the removal of hexavalent chromium from soils, the two-dimensional electrode configurations containing anode surrounded by three or more cathodes can be effectively utilized compared with one-dimensional electrode configuration. A larger electrode spacing increases the processing time required, and it was also found that a larger electric field strength reduced the processing time required.
Japanese houses have been highly airtight and shut out the fresh air. Therefore, the quality of indoor air becomes inferior. The problems related to the damp of indoor environment have been increased with the change of lifestyles and architectural methods. Humidity control building material using porous soil “allophane” has been developed to control humidity environment in living space. Numerical simulation method based on heat and moisture transfer model was studied to estimate performance of humidity control material in various living space. It was found that building material could decrease humidity changes and inhibit overdry.
Low density poly(ethylene) (LDPE) samples were reprocessed in multiple cycles by a single-screw extruder. The reprocessed heat degraded samples were characterized by gel permeation chromatogram (GPC), dynamic viscoelasticity and stress-strain measurement. The decrease in molecular weight (Mw) obtained from GPC measurement for LDPE with reprocessing was small than that for poly(propylene) (PP) and poly(styrene) (PS) in the region of low degradation time (t<30 min). Degradation time dependence of the molecular weight (Mη) obtained from measurements of viscoelasticity for LDPE was very different from that for PP and PS. In LDPE, not only the scission of polymer chain but the formation of branched and crosslinked chain are caused by heat degradation mainly at the week point on polymer chain, so that Mη was constant regardless of t. Young’s modulus (E) obtained from stress-strain curves did not change for both the virgin and heat degraded samples.