Vertical distributions of heavy metals of core sample sediments under 150 cm in abandoned mine tailings were examined. Core samples were analyzed by XRD and further examined by ICP-AES measurements after sequential extraction with 1 mol dm^-3 HC1, 10% HF, and conc. HNO₃. The XRD results showed that a-quartz was a main component in the core samples. Further, based on the sequential extraction results, the distributions of trace amounts of minerals, such as chlorite, sericite, rhodochrosite, pyrite and galena in core samples which were undistinguishable by XRD analysis, were estimated. Chlorite and rhodochrosite were relatively reactive and dissolved in HCl-extraction, a-quartz and sericite were dissolved in HF-extraction, and sulfides were dissolved in HNO₃-extraction. Under 40 cm-zone was relatively rich in clay minerals and carbonate where sulfate-reducing bacteria were active. Under 120 cm-zone contained pyrite-rich sediments. At present the function of sulfate-reducing bacteria is not so large to affect to the mineralogy in the sediment.

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This paper describes the separation and recovery of metal values such as nickel, cobalt and rare earths from spent nickel-metal hydride (Ni-MH) secondary batteries. The containing metals (Ni, Co, rare earths, Mn, Zn, Fe) in the batteries were efficiently leached by sulfuric acid solutions. By adjusting a pH of this leach liquor at around 3, rare earths were recovered as a white precipitate. Solvent extraction and supported liquid membranes using PC-88A in kerosene were applied for separation and recovery of Ni and Co from the filtrate. We propose a composite process using the both techniques for the separation and recovery of metal values from spent Ni-MH secondary batteries.

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A new treatment process to remove and decompose dioxins in leachate from a landfill site was developed through experiments using pilot units. This process consists of an reverse osmosis membrane process (RO process) for leachate treatment and a burning decomposition process for both sludge from pre-treatment like coagulation/sedimentation and dried salts from concentrate generated from the RO process.
Based on our experiments, the RO process removed 99% of dioxins in leachate and the burning decomposition process decomposed 99.9% of dioxins in sludge and 99% of that in dried salts from concentrate. These results completely complied with the latest Japanese effluent standards.

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The analyses of the extraction equilibrium formulations for metal ions up to high loading ratios of the extractant were carried out. The extraction equilibrium formulations can be determined by combining the results of the slope analysis method and the stoichiometric compositions of the extract species at the high loading ratios, and these can express the extraction and scrubbing behaviors of metals at all ranges of the loading ratios. The formulations and mass balance equations can be used to construct the separation process with counter-current mixer-settler cascade, leading to the most suitable conditions for the separation and purification of metal ions. The method proposed can be also applied for the design of the extractive separation process in the presence of water-soluble complexing agent.

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