The present investigation is a preliminary study of metallic niobium purification process from ferroniobium, by thermal decomposition of niobium pentachloride in reductive atmosphere. Niobium pentachlorides was produced from the chloride separation and distillation of ferroniobium chlorination process. The study aims to provide some basic data related with the experimental condition of niobium pentachloride reduction. The thermal treatment process was conducted at 1373-1523 K for about 6 hours. The gas utilized in the process was 40% H2 balanced with Ar or commercial quality (CQ) H2 which was flowed at 0.3 l/min. The optimum experimental condition was found at the temperature of 1473-1523 K by using CQ H2. The products of thermal decomposition consist of chips, black, gray and yellow/white powders. In this condition, chips were recovered as the highest content of niobium product, that reach at about 98 mass% niobium. The chip product is composed of a mixture phase of Nb and NbO with the average of mass fraction of about 0.85 and 0.15, respectively. NbO seems to be formed mainly due to dechlorination of niobium oxychloride compound, as an impurity of the raw material.
Generally waste products contain many kinds of materials and crushing or comminuting for the recycling must liberate them. The process involves the use of impact and shear types of equipments. In the former type high rotating reversible blow bars pound the products toward the grading impact plates. But it is difficult to crush tender materials such as plastic films or clothes. In the latter type, the defacement of cutting blades increases more when hard materials such as metals or glasses are fed. On the other hand, the media agitating type of equipments used for the liberation of mineral ore is considered unsuitable for the liberation of thermoplastic resins. However, they have some advantages such as easy going in operation and scale up. In this study, comminution of a media agitating mill (Tower Mill) was considered for the automobile shredder residues (ASR), which contain urethane, plastics, metals, glasses and so on. When ASR was directly comminuted, no significant variation could be observed in the weight percentage distribution. However in case of ASR frozen by liquid nitrogen and hot pressed by molding machine it was well comminuted. Especially it was found that the hot pressed light and heavy ASR could be easily comminuted to less than 1 mm at the ratio of 66.0% and 20.7%, respectively.
Japanese modern houses become highly airtight and thermally insulated, because of saving energy. As a result, problems related to humidity of indoor air have been increased, for example, excessive dew formation etc. To solve these problems, we have developed a new humidity controlling material. It was found that allophane,sepiolite and diatomite have good performance for raw material of humidity controlling material by measuring adsorption isotherm for moisture. By evaluating humidity controlling characteristics of samples made from these raw materials, it was cleared that humidity controlling characteristics is influenced by pore size distribution. Especially, the equilibrium of moisture adsorption is influenced by micro pore less than 10 nm, and the speed of moisture adsorption is influenced by macro pore.
Electrokinetic soil remediation by electroosmosis and ionic migration is restricted to soluble substances. At a higher pH, the soil particles sorb more heavy metals 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 by electrokinetic method from contaminated soils. In the present study, acidification of soils are predicted with a numerical method in which electrical flow is coupled with hydraulic flow, and the effects of some factors such as electrode configuration, electric field strength and electrode spacing for the saturated soils are investigated. The results obtained this study are summarized as follows: The two-dimensional electrode configurations containing cathode surrounded by three or more anodes rapidly acidify the soils compared with one-dimensional electrode configuration. However, two-dimensional electrode configurations develop spots of inactive electric field between cathodes. A larger electrode spacing increases the processing time required. Meanwhile, a larger electric field strength reduces the processing time required.
Many contaminated lands and drainage with arsenic are caused by human activity in the world. In mine industry tailing dumps and old mined sites are main origin to generate acid mine drainage (AMD) containing arsenic. This review describes natural processes of the AMD generation and remediation based on the published 41 papers and reports.