The technology for removing toxic metals such as lead, cadmium, arsenic and radioactive elements from environment as well as recovering valuable metals such as precious metals from various wastes was developed by effectively using various natural products and biomass wastes. The natural products employed in the present work are pectic and alginic acids contained in fruits like orange and apple and in brown seaweeds, respectively. These acidic polysaccharides behave as natural chelating polymers for cationic metal ions such as lead(II), copper(II) and iron(III). On the other hand, those loaded with high-valence metal ions such as iron(III) selectively adsorb anionic species of arsenic(III and V) according to ligand exchange reactions. On the basis of these adsorption behaviors of pectic acid, adsorption gel was directly prepared from orange waste at cheap cost to prove the effective removal of arsenic from actual acid drainage. Another adsorption gel was prepared from persimmon waste, which exhibited selective adsorption to thorium and uranium over rare earth elements. It is expected to be used for the removal of these radio active elements from environment including tailings of rare earth ores. Lignin contained in wood wastes in large amount was extracted as lignophenol according to the phase separation method developed by Funaoka and new adsorption gel was prepared by crosslinking. The gel exhibited interesting behavior for gold. Elemental gold was directly recovered from gold containing hydrochloric acid solution, which was attributed to the reductive function by phenol groups rich in this gel. Novel adsorption gel was also prepared from waste newspaper paper by immobilizing primary amino groups. This gel exhibited high selectivity to copper(II) and chromium(VI) in pH region and to precious metals, gold(III), palladium(II) and platinum(IV), in the adsorption from hydrochloric acid. All of the adsorption gels developed in the present work exhibited more excellent adsorption behaviors than conventional adsorbents like commercially available ion exchange resins and activated carbon.
By performing experiments in the laboratory, we verified how the measuring accuracy of the Downward Compact Conical-ended Borehole Overcoring (DCCBO) technique is affected by the time dependence of the mechanical characteristics of an adhesive to bond the strain cell together. In order to quantify the mechanical characteristics of the adhesive by the correct evaluation of experimental results, we determined the strain coefficients using numerical model including models of adhesive and strain cell. Consequently, we found that the best evaluation of experimental results measured two hours after affixing the strain cell, was achieved when Young's modulus was 1.45 MPa and Poisson's ratio was 0.00. We also demonstrated that proposed method was capable of highly accurate rock stress evaluation. Performing in-situ tests, we clarified the requirements for the general characteristics of the adhesive and the strain cell (epoxy section). Young's modulus of adhesive and strain cell (epoxy section) should be set to about 100 MPa for moderately hard or hard rocks having a Young's modulus of about 10 GPa or greater and to about 10 MPa for soft rocks having a Young's modulus of about 1.0 GPa.
Characteristics of two types of fiber-reinforced mortar in four-point bending are discussed and compared in this paper. One is steel fiber-reinforced mortar that was introduced to Japan in 1960s. Another is PET (Polyethylene Terephthalate) fiber-reinforced mortar that was recently invented and right now information about its characteristics is still very limited. Two types of fiber-reinforced mortar were tested in a servo-controlled testing machine to obtain a complete load-deflection curve or a curve in pre and post failure regions. Photographs of a sample were taken in the four-point bending test to evaluate the crack length and the crack opening displacement (COD). Testing results indicated that the bending strength of two types of fiber-reinforced mortar was increased considerably compared with that of a plain mortar. Peak and residual strength of PET fiber-reinforced mortar was found to be slightly weaker than that of steel fiber-reinforced mortar, however, PET fiber elongated easily, therefore wider crack width was permissible. It was also shown that the peak strength can be theoretically estimated by the stress-strain curve obtained in uniaxial tensile test as pointed out formerly by Okubo et al. Right now, usage of PET fiber-reinforced mortar is still very limited, however, the results obtained in this study indicate promising future of PET fiber-reinforced mortar. Especially, it is considered to be appropriate for usage under severe environmental conditions and construction in narrow space such as path through forest or winding road.
Pulsed power is a short pulse, high energy generated by an explosive charge or high current which can be utilized for various applications. Explosive is a kind of pulsed power source, but the legal restrictions imposed on the usage of explosives are very severe and also it is necessary to strive for the handling, maintenance and safety of explosives. Rather than using explosive, electric pulsed power can be used to generate shock waves, as the technique is simple and safe. The aim of this study is to effectively use the underwater shock wave generated by the electric pulsed power for the destruction of structure and rocks. In this study, the underwater shock wave generated by gap discharge (GD method) or metal wire explosion (WE method) using the electric pulsed power was evaluated by optical observation using a high-speed camera, pressure measurement, and deformation of aluminum pipe. The energy of an underwater shock wave can be improved by increasing the charge energy of a capacitor. The underwater shock wave generated by GD method showed the existence of many shock waves. The duration of the pressure pulse is long in this phenomenon, but a peak pressure of underwater shock wave by the WE method is higher than the GD method. In the deformation experiments of aluminum pipe, the bulging produced by the WE method has about 2 times that of the GD method.