Bacteria play an important role in various transportation, concentration and crystallization processes of elements in the earth environmental system.Microbial mineralization is a key role for the concentration of toxic elements and spoiled water systems.Electron microscopic studies have disclosed crystallization of turquoise and jarosite in the early stage of the remediation experiment, conducted at room temperature, by using activated sludge.Amorphous materials concentrated on cell walls at incipient stage, are finally transformed into well-defined crystal structure of biominerals.Various minerals such as carbonate, silicates, iron oxide, hydrate phosphates, sulphides and radioactive materials are produced through bacterial biomineralization and microbial remediation processes.In addition to biomineralization, biodegradation of a variety of hazardous and toxic chemicals in the abandoned mining sites, concrete erosion and river-water ecosystem etc., has also been found.

抄録全体を表示

In this experimental study we attempted to clarify the mechanisms of dissolution of Au in low temperature oxidized acid hydrothermal solutions. The results of experiments on the reactions of Au in the HC1 aqueous solutions at 150°C and 5 atm are as follows: Au was dissolved up to 1, 000-1, 500 ppm in the 1 mol/l, 3 mol/land 6 mol/lof HCl aqueous solutions. There were observable changes in the concentration of Au in the three systems. Furthermore, in the 3 mol/land 6 mol/lHCl aqueous solution systems, the concentration of Au had decreased as low as several ppm to several 10 s ppm by the end of the experiment. On the other hand, in the 9 mol/land 12 mol/lHCl aqueous solution systems the concentration of Au showed only insignificant changes of several ppm. In all experimental systems, the dissolved state of Au at room temperature was Au³⁺.
The above results are interpreted as follows:(1) The chloro-complexes of Au are stable with high solubility and transportability in aqeous solutions of low pH, high Cl^-concentration and high fo₂.(2) Solubility of Au in the HCl aqueous solutions remarkably increases with diffusive H2 gas formed by the reaction from the system. Terefore, in natural environments there is a possibility that the solubility of Au metal is controlled by the amounts of diffused H₂gas changeable depending on the geological environments such as the porosities of rocks.(3) In the current study it has been found that differences in crystallinity of the Au strongly influences its solubility. In natural settings as well, it is thought that difference in crystallinity of the Au metal determined by its origin have a remarkable influence on its solubility.

抄録全体を表示

It is considered that accumulation of data concerned with falling behavior of rocks along a slope is insufficient. Observational study for falling behavior of rocks was carried out at an open-shoot slope of a quarry by using video cameras. Linear velocity, rolling velocity, the ratio of the velocity after impact to the velocity before impact of a rock against a slope, and jumping height were analyzed from the video pictures, by using a personal computer with image processing board. From these video analyses, following points were clarified. 1) Falling velocity of the tabular rock is unexpectedly higher than the value considered generally. This shows the rock of tabular shape is not always safety. 2) Rolling velocity at optional distance from the top of a slope could be estimated reasonably by the equation(10)described in this text.3) There are cases that velocity ratios before and after the impact exceed 1.0. This means technical terms restitution coefficient and attainuation coefficient should not be used in the rock fall problem. 4) The value of 2m measured as jumping height is considered to be available when the height of protection fence is planned.

抄録全体を表示

露天掘り鉱山において斜面の安定性を評価することは必要かつ重要である。多くの場合, 複雑で非線形の問題である。本論文では, ニューラルネットワークを応用して, 岩盤斜面の円形崩壊とくさび崩壊の安全率を直接評価する自己学習型適応モデルを構築する新手法について述べる。斜面安定の最適外挿評価を得るため, まず, 改良された誤差逆伝播法, いわゆる外挿評価アルゴリズムを作製し, ついで, それを非線形モデルを得るため階層型ニューラルネットワークを訓練するのに用いた。円形崩壊とくさび崩壊のモデル化手法と外挿予測について紹介した。結果は極限平衡理論による解とよく一致した。

抄録全体を表示

For the excavation and the supporting of large rock slope, the observational construction method is becoming increasingly important in order to carry out the support decision immediately, by taking discontinuity distribution into account, because of the difficulty of supporting after some benches have already cut.
It is well known that slope stability is strongly controlled by discontinuity distribution in the case of the hard rock masses. Goodman and Shi (1982) proposed “Block Theory” for the estimation of slope stability considering discontinuity distribution. Key block, however, can be found out after all the discontinuity traces of the block appeare on the slope surface. In that moment, the key block is unstable and can move out of the slope.
Considering the above, the authors developed “Stochastic Block Theory” for the prediction of the key block before all the discontinuity traces of the block have not appeared on the slope, in other word, in the moment some of the discontinuity traces of the key block have appeared.
Using Stochastic Block Theory, the probability of becoming a key block can be estimated concerning the block surrounding some discontinuity traces and bench.

抄録全体を表示

The relation between the phase relations and the equilibrium partial pressures of oxygen in the Ti-Fe-O ternary system has been determined at 1, 273 K using a thermogravimetric method in CO-CO₂ gas mixtures and also X-ray diffraction technique for quenched samples after the equilibrium. The possibility of upgrading natural ilmenite ore to a rutile substitute has been discussed and confirmed thermodynamically. The standard Gibbs energy of the reactions at 1, 273 K were also obtained as follows:
Fe (s) +FeTiO₃ (s) +1/2O₂ (g) =Fe₂TiO₄ (s), -190.9kJ·mol^-1,
Fe (s) +TiO₂ (s) + 1/2O₂ (g) =FeTiO₃ (s), -202.3kJ·mol^-1.
Activities of magnetite show negative deviations from Raoult's law in the Fe₃O₄-Fe₂TiO₄ solid solutions coexisting with metallic iron at 1, 173-1, 373 K.

抄録全体を表示

Heavier rare earth which is contained in a small amount in ores such as bastna site and monazite has been accumulated as heavier rare earth residue without doing separation and purification due to its small demand. The heavier rare earth residue includes seven rare earth elements such as Tb, Dy, Ho, Y, Er, Tm and Yb.The separation and recovery process of Dy, Y, Tm and Yb from leached solution of the heavier rare earth residue was investigated by using a column method with a solvent impregnated resin.The solvent impregnated resin was prepared by impregnation of organophosphorous extractant whose trade name is PC-88A into a macro porous resin, Amberlite XAD-7.
It was almost impossible to separate them in simple adosorption and elution steps.However, we attained to individually separate Dy, Y, Tm and Yb from the leached solution first by changing eluent concentration from pH 2 to 2N HCl in the elution step, and secondly by using a development column and changing eluent concentration in the elution step.The separation process flow was proposed for raw materials containing rare earth by using the conventional solvent extraction method and solvent impregnated resin method.

抄録全体を表示

In the hydrometallurgical processes for treatment of zinc leach residues, the residues were dissolved in high sulfuric acid solutions at about 100°C.In the hematite process, the dissolution of zinc leach residues is carried out under the reducing conditions.Accordingly, the hematite process starts from oxidation of ferrous sulfate solution.In order to explain the mechanism of the hematite process, it is necessary to know the solubility of ferrous sulfate in aqueous solutions at high temperatures.The solubility of ferrous sulfate in pure water and sulfuric acid solutions has been clarified up to 100°C.Above 100°C, only the solubility of ferrous sulfate in pure water from 120 to 180°C was reported.
We have determined experimentally the solubility of ferrous sulfate in pure water and sulfuric acid solutions from 130 to 220°C and the effect of coexisting zinc or magnesium sulfate on the solubility of ferrous sulfate in aqueous solutions has been made clear at 200°C. The experimental result shows that the solubility of ferrous sulfate steeply decreases with an increase in temperature and increases with an increase in sulfuric acid concentration.The solubility of ferrous sulfate in pure water and sulfuric acid solutions decreases with an addition of zinc or magnesium sulfate at 200°C.

抄録全体を表示

The dissolution behavior of electrodeposited Zn was studied in the electrowinning solution containing an impurity such as Ag, Al, As, Cd, Co, Cu, Fe, Ge, Ni, Pb or Sb. The dissolution occurs when the operating current density becomes substantially lower than the critical current density for Zn deposition onto Zn electrode. The simulation experiments revealed that the decrease in the operating current density should be resulted from such two factors that the practical current density decreased due to the increased cathode surface area and that the critical current density increased in the presence of impurity in the solution. The impurities were classified into four groups according to their effects, previously reported by the present autnors, on tne cnticai current density. The time-dependence of Al cathode potential was measured at three levels of current densities in the solutions containing three different amounts of each impurity. The effects of each group of impurities on the electrodeposition and dissolution behaviors of Zn were discussed by considering above two factors. Further the dissolution behavior during the commercial electrowinning operation, in which the impurity concentration was usually time-dependent, was briefly referred.

抄録全体を表示

Solubilities of oxygen in liquid and solid cerium were determined by metal-oxide equilibrium method: Solubility in liquid cerium
log (C_o/mass %) _{liquid Ce}=-4600 (±500)/_T+6.3 (±0.4)(1, 123-1, 573 K)
Solubility in solid cerium log (C_o/mass %) _{solid Ce} (γ) =-3200 (±600)/T+5.9 (±0.7)(923-1, 023 K)
Ce₂O₃ was identified by the X-ray diffraction analysis as the oxide phase in equilibria with cerium from 923 to 1, 573 K.
Based on the results, the partial phase diagram of Ce-O system was determined.

抄録全体を表示