It is difficult to remove effectively phosphorus from wastewaters by coagulation sedimentation method. Especially it is more difficult to remove dilute phosphorus from wastewaters by the above method. Therefore flotation method has been examined to remove those phosphorus, and to meet the water pollution control legislation.
In dissolved air flotation under conditions of pH 9-10 and [Ca²⁺]/[HPO₄^2-] =3 using such a collector as sodium oleate (NaOI), dodecyl amine hydrochloride (DAC) or sodium dodecyl sulphate (SDS), a phosphorus removal showed over 97%(residual phosphorus concentration of about 1mg/l) by using any collector, nearly 100% removal rate being obtainable with SDS in particular.
The dissolved air flotation of dilute phosphorus solution containing a HPO₄^2-concentration of 1x10^-4 mol/dm³ (P: 3.1 mg/l) was carried out in order to remove phosphorus in sewage or domestic wastewaters. A phosphorus removal rate of 75% was obrained under conditions of 1-10^-5 mol/dm³ of SDS, [Ca²⁺]/[HPO₄^2-] =3 and pH 8, and a residual phosphorus concentration was below 1mg/l. Moreover, thephosphorus removal rate increasing with increase in pH value, at pH 11 a phosphorus removal rate of 95 98%(residual phosphorus concentration of 0.06 0.16mg/l) is obtainable.
It is considered that the dissolved air flotation is more advantageous than the crystallization process known as a process for treating wastewaters of such dilute concentration, because of short flotation time and large treatment capacity.

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Phase relations in the FeO-ZnO-SiO₂ system coexisting with the Fe, which are of considerable practical importance in the extractive metallurgy of zinc, have been studied at 1, 100 K by equilibrating synthetic samples in evacuated sealed quartz tubes. The phases were determined by the X-ray microanalysis and identified using X-ray diffraction. The results indicate that phase relations in the FeO-ZnO-SiO₂ system coexisting with the Fe at 1, 100 K are composed of two-phase fields (FeO s.s. + Fe₂SiO₄ s.s., Fe0 s.s.+ Zn₂SiO₄ s.s., ZnO s.s.+ Zn₂SiO₄ s.s., Fe₂SiO₄ s.s.+ Zn₂SiO₄ s.s.), three-phase fields (FeO s.s.+ Fe₂SiO₄ s.s.+ Zn₂SiO₄ s.s., FeO s.s.+ ZnO s.s.+ Zn₂SiO₄ s.s.) and single phase fields (Fe₂SiO₄ s.s., Zn₂SiO₄ s.s.). The mutual solubilities between FeO and ZnO, between Fe₂SiO₄ and Zn₂SiO₄ were determined.
The activities of FeO and ZnO in the FeO-ZnO-SiO₂ system coexisting with the Fe were estimated by reference to the result of the Fe-Zn-ZnO-FeO system2). The activity of ZnO in the zinc sinter was estimated at unity from the present result and our previous results regarding the binary system ZnO-SiO₂, the ternary systemsl) ZnO-SiO₂ -CaO, ZnO-SiO₂ -Al₂O₃, ZnO-SiO₂ -MgO and the ternary system Fe-Zn-O. The relation between the reaction path of the iron-reduction distillation process and activities of FeO, ZnO in the Fe-Zn-O system at 1, 100 K was shown.

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The pre-drainage of methane gas from coal seams is adopted in cases where high emissions during development of headings and at the longwall result in stoppages at the face, or in seams where outbursts of gas and coal endanger workers and materials. The authors have proposed the approximate calculation method of unsteady gas pressure distribution in coal seams and gas emission into boreholes in cases of pre-drainage of gas. The paper shows some analyses of in-situ data with this C-function method.

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To develop a hydrometallurgical process for the selective recovery of copper and iron from motor scrap. the leaching of copper with Cu (II). ammine solution using a spray-type or an up-stream penetration type reaction tank has been examined, and a closed circuit process has been proposed for the copper recovery. Copper can be leached by either spray leaching or up-stream penetration leaching with large leaching rate, where the resultant Cu (I) is oxidized to Cu (II) with air during the circulation of leachant. The leaching rate is greater in the up-stream penetration leaching than that in the other, since the whole copper sample is submerged in the leachant in the up-stream penetration leaching. Copper is leached efficiently from motor scrap as well as copper wire. Copper can be recovered from motor scrap in the closed circuit process which consists of the Cu (II) ammine leaching, solvent extraction with Lix 84, and electrowinning of copper from the stripping solution.

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The effect of oxidizing agent, concentration of ammonium thiocyanate, pH and the temperature on the dissolution of silver in basic ammonium thiocyanate solution were studied.
The following have been concluded: 1. Cu (II) and oxygen gas are necessary to dissolve silver effectively.
2. Dissolution rate of silver is proportional to the concentration of thiocyanate at lower concentrations of thiocyanate, but it becomes constant independently of the concentration at higher concentrations.
3. When the concentration of thiocyanate is high enough to make the dissolution rate of silver independent of the concentration, the dissolution rate increases almost proportionally to the increase in the concentration of Cu (II).
4. When the rate is proportional to the concentration of thiocyanate, the activation energy obtained is rather high and the rate determining step is assumed to be the chemical reaction of thiocyanate ion with silver on its anodic sites on the surface of silver particles.
5. When the rate dissolution is almost proportional to the concentration of Cu (II), the rate determining step is the diffusion of Cu (II) ions to the surface of silver particles.
6. Overall reactions are considered as follows: Ag+Cu (NH₃) ₄²⁺+6SCN^-=Ag (SCN) ₄^3-+Cu (SCN) ₂^-+4 NH₃ Cu (SCN) ₂^-+4 NH₃+H⁺+1/4 O₂=Cu (NH₃) ₄²⁺+2SCN^-+1/2 H₂0 These phenomena are quite the same as those of the dissolution of silver in acidic thiocyanate solution using Fe (III) as oxidizing agent.

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Rock slopes left after surface mining in limestone quarry grow gradually larger and higher year after year. Recently, the stability evaluation of these large rock slopes has become an important engineering problem.Rock mass contains many discontinuous planes, such as joint, fault, etc, and the failure mode of rock slope is usually influenced by the geometrical conditions of the discontinuous planes.
The block theory is the way to analyze three dimensional stability problems of discontinuous rock masses. In this theory, the critical block is named as the key block, and its character is defined by a topological concept. After the judgement of the key block, it is possible to determine the most suitable way to support these blocks.
This paper describes the valid way of treating trace map including many discontinuous planes in order to find out the key block by vector calculation, and applies to stability evaluation of large rock slopes for three limestone quarries.

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The precipitation reaction of crystalline hydroxyapatite (HAp) was investigated for the removal of orthophosphate in industrial wastewater. Experimental results in the Ca-PO₄-OH system showed that the log [phosphorus residuals] were decreased with increasing pH during pH 7-10 region. Increasing calcium and phosphorus concentration in the initial solution increased phosphorus removal. The initial phosphorus concentration gave greater effect for the phosphate removal than calcium concentration. At pH 8.0, Ca/P=1.6, the phosphorus residuals were 0.48 mmol/l and 0.08mmol/l for 0.7 mmol/l and 7 mmol/l of the initial phosphorus concentration, respectively. Amount of calcium dosage was sufficient at ratio Ca/P=1.6. This phenomena indicates that the precipitated calcium phosphate acts as seed for the crystallization of HAp and it accelerates the crystallization velocity.
The HAp seeded phosphoric acid solution was continuously treated by reaction vessel. The pH was maintained by means of the pH-stat-controlled addition of milky lime. The log [phosphorus residuals] was decreased with increasing pH. From the experimental results, a new process with a two stage addition of lime was proposed. For the first stage, the addition of milky lime was done at pH 8.0-9.0. The second stage, theoretical amount of lime was added to phosphorus residuals under the pH 8.5-9.0. A crystalline HAp of small sludge volume was obtained.

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The creep of rock at low stress level has an important significance on the long term stability of rock structures. But it is impractical to examine the tertiary creep at low stress level because failure time is very long. It is necessary to develop a method to examine the behaviour in tertiary creep region within comparatively short period. In this study, a compression test was conducted beyond the strength failure point, and thereafter stress was maintained to be constant. This creep test in the post-failure region can be conducted within far less time comparing with an usual creep test under the same creep stress.
Uniaxial compression creep test in the post-failure region was conducted with a servo-controlled testing machine using Sanjome-andesite, Akiyoshi-marble and Tako-sandstone as rock samples. In comparison with usual creep test under the same creep stress, the relationship between the strain rate and the time before final failure is the same. And, strain rate in tertiary creep region is inversely proportional to the time before the final failure. It can be said that the creep test in post-failure region is useful to examine especially the performance of tertiary creep
It was also found that the creep strain rate is not affected strongly by the hereditary stress path (hereditary integral), that is, the creep strain rate depends only on stress and strain at that point on stress-strain curve. And also the relation of the creep strain rate and the stress-strain curve was also discussed.

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In the manufacturing process of multi layer ceramic chip capacitor, some unqualified products are produced and discarded as an industrial waste. Such a waste consists of barium titanate dielectrics and contains small amount of palladium as inner electrode. In order to recover and recycle palladium from the waste, liquid-liquid extraction was applied and investigated.
Extraction behaviors of palladium and barium titanate were first examined using n -butanol, iso-octane and kerosene as organic phases at various pH. Palladium was extracted into n-butanol fairly well at the wide pH range of 1.0-10.5. On the contrary, barium titanate was not extracted almost entirely at the same conditions. Therefore, it was estimated that n-butanol was suitable organic phase for the separation of palladium from ceramics. When iso-octane or kerosene was used as an organic phase, large amount of barium titanate transferred into the oil phase at the wide pH range except high acidity, so that successive extraction of palladium from ceramics could not be expected except in high acidic medium. It was also shown that the addition of dodecylammonium acetate (DAA) as a collector was effective to promote the recovery of palladium in n-butanol.
Then, the extraction was conducted for the practical waste of ceramic capacitor using n-butanol as an organic phase under the condition of 200mg·dm^-3 DAA and pH 1.0. As a result, it was found that palladium was effectively separated with the recovery of 96.8% and the yield of about 10%, and that the product was upgraded to 34.4% palladium, about 10 times higher than the feed.

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The extraction and separation of cobalt, nickel and copper from the leach liquor of cobalt crusts with the mixed solution of ammonium carbonate and ammonium sulfite was carried out by solvent extraction. The extraction test was done by using DP-8R, PC-88A, VA-10, LIX54, LIX64N and LIX84 as an organic solvent. Cobalt (II) ion in the leach liquor of cobalt crusts was oxidized to cobalt (III) ion with oxygen gases. In the solvent extraction, nickel and copper were selectively coextracted from the leach liquor with LIX84 as an extractant leaving cobalt (M) in the raffinate. For instance, % extraction of the metal components in one batch extraction of the leach liquor with the 10% LIX84 kerosene solution were 99.8% for Ni, 99.9% for Cu and 0.6% for Co, respectively. In the stripping from the organic phase loaded with nickel and copper, nickel was selectively stripped with the sulfuric acid solution at pH =nearly 1.5. Subsequently, copper was stripped with the sulfuric acid solution at pH<0.5. Concequently, cobalt, nickel and copper in the ammoniacal alkaline leach liquor of cobalt crusts were possible to be separated by solvent extraction.

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