The rock slope of mined-out quarry is very bad condition for revegetation because it is steep and disturbed. However, in order to recover an ecosystem of mined-out quarry, it is necessary to create a plant growth base on the rock slope and allowing trees to grow. We carried out some fundamental studies on the plant growth base creation on the rock slope ,using forest top-soil. First, we researched the thickness of plant growth base and base soil properties at the site of the rock slope in the forest area. Then we carried out the stability of plant growth base soil on the rock slope by using plane slide stability analysis formula. The main results obtained in this study are as follows: 1) The thickness of 10-15cm plant growth base soil is required in order for tree growth. 2) In the conventional plane slide stability analysis, the thickness of base soil expressed by perpendicular thickness was changed into the method of expressing by actual thickness. 3) The thickness of plant growth base which can be created on the base rock slope inclination of 60 degrees is 20cm. 4) The cohesion of soil is indispensable for the plant growth base;if cohesion of the base soil is zero, we cannot create the plant growth base on the rock slope using this soil.
The theory and a probe of the pilot hole wall deformation method, which is a 3-dimensional stress measurement method based on the stress relief principle, were developed. A pilot hole is drilled from the bottom of a borehole and the stress measurement probe is inserted into the pilot hole. The borehole is advanced as the overcoring and the changes in the radius of the pilot hole in three directions and in the axial lengths between the borehole bottom and the pilot hole wall along four axial lines are measured by cantilever type-displacement sensors. The differences between the displacements by the elastic stress analysis and those measured by using the probe were within 3% in the uniaxial compression test of an acrylic resin plate having a hole. The stress components which were applied to a cubic Kimachi sandstone specimen with an inclined borehole were evaluated by using the probe within the error of 6% the applied maximum principal stress in a biaxial loading test.
In order to recover Ti and Cr compounds from the incinerated bottom ash, the wet high gradient magnetic separation (HGMS) was investigated by using a superconducting magnet. To separate Ti and Cr from Fe particles, it is necessary to weaken the magnetic force, which is acting on Ti and Cr particles. At first, basic tests using a pure sample of Ti or Cr compound were performed in order to minimize the amount of captured fraction of Ti and Cr compounds. As a result, the minimum amount of captured fraction of each compound was obtained by varying the magnetic susceptibility of the fluid. As for Ti compound (TiO2, CaTiO3), iron tri-chloride and manganese sulfate were used to change the magnetic susceptibility. Likewise, as for Cr compound (Cr2O3), water based magnetic fluid was used. By applying the condition, which gives the minimum captured fraction, to a mixture sample of Ti (or Cr) and Fe compounds, Ti and Cr compounds were efficiently recovered as nonmagnetic products. Furthermore, the conditions obtained from basic tests were applied to the bottom ash from an industrial waste incinerator, which has a high content of TiO2. As a result of wet HGMS after leaching ash with HCl, the TiO2 grade was increased from 10wt% to 28wt%, whereas the TiO2 recovery reached 64 wt%.
The effect of polyethylene glycol (PEG) on the dissolution behavior of Zn electrodeposited from the electrowinning solutions containing impurities has been investigated by measuring the time-dependence of cathode potential during electrolysis and the partial polarization curves for Zn and impurity deposition. The impurities are classified into four groups ; group I (Ag, Cu, Cd) which changes inherent hydrogen overpotential ηOH by depositing at limiting current density; group II (Ni, Co, Fe) which reduces ηOH by partially depositing at lower current densities than limiting one ; group III (As, Sb, Ge) which catalytically reduces ηOH; and group IV (Al, Pb) which causes no change in ηOH. The PEG affected to the dissolution of deposited Zn in a different way depending on the kind of impurity. In the solution containing Cu of group I as impurity, deposited Zn was more likely to dissolve with PEG than without. Although PEG suppressed Zn deposition, it had no effect on Cu deposition at its limiting current density. Therefore, PEG increased the content of Cu in deposited Zn. Since hydrogen overpotential is lower on Cu than on Zn, codeposited Cu promoted the dissolution of Zn. In the solution containing Ni or Co of group II, PEG suppressed the dissolution of deposited Zn because the evolution of hydrogen was inhibited. Although Sb of group III depolarized the cathodic potential and decreased the current efficiency for Zn deposition, PEG polarized the cathodic potential and increased the cathodic current efficiency. The harmful effects of impurities of group II and III on the dissolution of Zn and the depolarization of cathode potential were decreased with an increase in the molecular weight and the amount of PEG added.
Removal of cadmium in guts of scallop is one of serious problems in the northern part of Japan. The guts cannot be discarded as well as used as food, feed, and fertilizer unless the cadmium is removed from them. We have developed a swirling jet mixing method having high mixing efficiency and simple structure for wastewater treatment and snow melting. In this study, we applied this mixing method to cadmium extraction from the guts of scallop. HCl aqueous solution of pH=1.0∼2.0was used for the cadmium extraction. Small-scale and medium-scale tests were carried out using boiled no-cut guts by the swirling bubbling jet mixing method. More than 98% of the cadmium contained in the guts was extracted. The extraction rate was higher than that in the shaking test. The cadmium concentration in the treated guts cleared the acceptable cadmium level in food in Japan.