The low-level radioactive waste generated from research institutions and hospitals etc. is packed into a container and is kept. The volume reduction state by incineration and the compression processing or the unprocessed state because neither landfill sites nor disposal methods have been fixed. Especially, because the bulk density is low, and it is easy to disperse, the low-level radioactive waste incineration ash incinerated for the volume reduction has a big issue problem in security, safety, stability in the inventory location. A safe and appropriate disposal processing method is desired. When the low temperature sintering method in the use of the glass bottle cullet was examined, it was verified that volume reduction and stabilization of low-level radioactive waste incineration ash. The proposed method is useful for the easy treatment of the low-level radioactive waste incineration ash.
Electrokinetic soil remediation can be used a remediation tool to extract dissolved ions and organic compounds from soils. To initiate electrokinetic transport, a DC electric potential field is applied to soils. The magnitude of the transport velocity due to electromigration and electroosmosis is directly related to the electric potential gradient. Most researches have been focused at the remediation of saturated soils. However, many contaminant sources lie within unsaturated soils as a result of leaking chemical storage tanks and landfills. Electrokinetic induced transport of soil water and ions within the water may provide a remediation alternative to unsaturated soils. In this study, hydrogen and cadmium ions transport in unsaturated soils are predicted with a simple numerical method in which electrical flow is coupled with hydraulic flow, and the treatment for unsaturated soils are investigated. The results obtained in this study are summarized as follows: Hydrogen and cadmium ions move downward in unsaturated soils, particularly, move significantly downward in case of upper layer of sandy/clayey soils and lower layer of clayey/silty soils. However, remediation is applied successfully to unsaturated soils by coupled electric-hydraulic gradient.
In electrokinetic soil remediation, contaminants are removed from soil and groundwater by action of an electrical potential applied across electrodes embedded in the contaminated medium. Soluble substances can be removed effectively by electroosmosis and ionic migration. However, contaminants that are adsorbed on the soil or are present as precipitates can not be effectively removed. In particular, the solubility of most heavy metals may be significantly reduced at elevated pH values. When impurities such as oxide and carbonate minerals are present, electrokinetics alone may not be effective in the extraction of heavy metals due to the higher acid / base buffer capacity. Also, acidification of the medium might cause large weight losses by dissolution of part of the solid matrix. It would, therefore, be better if the treatment were performed at neutral pH. In the present study, the effectiveness of introducing ethylenediaminetetraacetic acid (EDTA) as complexing agent to enhance the removal of cadmium from kaolinite by ion migration is examined. The investigation was carried out in a laboratory-scale column containing kaolinite contaminated with cadmium. As results of the study, cadmium migrated toward the anode without accumulation of cadmium and it was found that the effectiveness of EDTA for removing cadmium was significantly affected by the soil pH.
It is necessary to utilize special techniques of separating submicron-size particles from other micron-size particles such as hydrocyclone and liquid-liquid separating. In this experimental work, separation of TiO2 and Al(OH)3 artificial mixture was investigated. Separation of submicron TiO2 particles from micron Al(OH)3 particles was carried out using a column bed filled with plastic fiber tubes or glass balls as matrixes. The Al(OH)3 particles have been mainly captured on the matrixes due to the hetero-coagulation effect. Large particles could be easily attached on matrixes because of strong lift force, and surface interactions between particle and matrix. The submicron TiO2 have been flowed out from the apparatus because of low collision possibility with the matrixes. As a result, submicron TiO2 particles were separated from micron size Al(OH)3 ones. This method could be applied to separate submicron TiO2 particles from Brazilian clay.
Tetra-methyl ammonium hydroxide is used in various electric and electronic parts production processes such as semiconductor, liquid crystal display and printed circuit board. The discharged amount of this chemical reaches about 2,500 ton/year from one factory in Japan. The waste liquor discharged from the liquid crystal display production contains 0.53wt% tetra-methyl ammonium hydroxide, 60 mg/dm3 phenol and ppb level of metal ions. In the cation exchange reaction, tetra-methyl ammonium ion is captured on the cation exchange resin. Other non-ionic organic matter like phenol goes through the resin without being captured on it, the separation being attained in this step. In the elution step, tetra-methyl ammonium ion captured on the resin is released as tetra-methyl ammonium chloride into aqueous solution by the action of dilute hydrochloric acid. Tetra-methyl ammonium chloride is converted to tetra-methyl ammonium hydroxide by the reaction between tetra-methyl ammonium chloride and OH− type anion exchange resin. The process is composed of three steps: cation exchange, elution and conversion. The experiments were carried out using ion exchange resin column of 20 mmφ and 735 mm height, in order to clarify the recovery and purity of tetra-methyl ammonium hydroxide at each step.
Defective aluminum electrolytic capacitors at manufacturing processes are generally shredded to below 3 mm and buried in landfills. Shredded capacitors contain aluminum, nickel and non-metal materials such as rubber, plastics and fibers. Nickel particles are recovered by magnetic separation, but it is difficult to separate aluminum particle from non-metal materials. We have investigated the recovery of aluminum from shredded capacitors with a laboratory-scale dry shaking table that we developed.