Iridium is mainly used in electrodes for oxygen evolution. The annual production of iridium is only a few tons and is unevenly distributed in South Africa and other countries, making recycling important. However, the recycling requires a strong acid, and the environmental load is very large. Therefore, it is necessary to develop a new recycling method that does not use strong acid. In this study, the solubility of iridium in hydrochloric acid in the oxygen-evolving electrocatalyst was improved by making iridium into a composite oxide.
To evaluate the effects of adding half-burnt dolomite and phosphate compounds as immobilizers for reducing the leaching of heavy metals from Zn leaching residues in Kabwe town, Zambia, batch leaching and immobilization tests were conducted. The results showed that the dolomite significantly reduced Cd, Cu, and Zn leaching. The immobilization was greatly influenced by pH. That is, the leaching concentrations of heavy metals decreased with pH. The Pb concentration in the leachate was significantly reduced by mixing the dolomite with phosphate compound to produce Ca5(PO4)3(OH), which might be further precipitated as Pb5(PO4)3(OH), resulting in a significant decrease in the leaching concentration of Pb. This study implies the effectiveness of half-burnt dolomite and mixing of the dolomite and phosphate compound for immobilizing heavy metals in mine residue.
At the Motokura mine, mine drainage is treated using a constructed wetland. Although the treatment is usually stable, it may not be able to cope with the rapid increase in mine drainage during snowmelt and rainfall, and further water volume reduction measures are needed. In order to effectively and efficiently implement these water volume reduction measures, a tank model runoff analysis was conducted to clarify the main origin of mine drainage. As a result, it was found that while the volume of mine water is relatively stable, the volume of water exuding from the slag dumping site fluctuates greatly due to the effects of rainfall. Therefore, it is necessary to prioritize countermeasures against the exudate from the slag dumping site.
Six-year vegetation survey has been done at four sites of slope covering constructions in the former mine, considering the effects of environmental factors. Spraying of green plants seeds in spring enhanced the establishment of Artemisia indica var. maximowiczii from the beginning, compared with Festuca rubra, which shows the wintery grow pattern. On the contrary, spraying of the seeds before snowing enhanced the establishment of F. rubra, which would be tolerant in the winter time. Additionally, high soil volumetric water content influenced the establishment of high wet-tolerant native plants such as Typha latifolia, Salix species and Pinus densiflora. Low relative effective photon flux density would increase the growth of shade-tolerant plant, Festuca rubra. Our results clarified that differences of seed spraying timing, the soil water content, and the light environment influenced the vegetation of green plants and native plants.
This study involved a mine in Akita Prefecture, Japan, which was closed in the 1970s and from which acid mine drainage (AMD) flows into a nearby river, after pH adjustment. During rainfall events, surface water was flowing in through the adit mouths and sinkholes of excavated areas. Therefore, countermeasure works to reclaim these were carried out by the project company, between 2017 and 2022. In methodology development, this study aims to evaluate the effectiveness of the countermeasures. AMD flow rate increases with rainfall, and water quality of AMD is acidic (pH 3.0–3.8) with higher concentrations of SO42–, soluble Fe, Cu, and Zn than those of river water. The AMD flow rate, normalized using precipitation, decreased over time, with a 55% decrease in 2022 relative to 2016. With progress in countermeasures, pH of the AMD increases, with a range of change of about 0.2, and concentrations of heavy metals in the AMD decreased. Local inhabitants use river water downstream of the mine, at a point-of-use, for agricultural purposes. Since precipitation phenomena such as heavy metals are not recognized in SO42–, an index indicating the degree of impact of AMD on the water quality of the point-of-use was calculated using SO42– as a contribution ratio; CR. The CR of the AMD to water quality at the point-of-use is in the range of 1.3%–11.8% and decreased over time.
In general, the solvent extraction behavior of Pt(IV) and Pd(II) by many amine extractants and solvating extractants is similar, so the separation of Pt(IV) and Pd(II) is not good. Therefore, the separation of Pt(IV) and Pd(II) by extractants other than amine extractants and solvating extractants has been investigated.
The utilization of adhesive bonding has attracted a growing concern in the field of automobile manufacturing, which requires the development of easy disassembly techniques for the reuse and recycling of body materials. In this study, we examined the immersion of adhesive joints in pure water and sodium chloride (NaCl) solution as a pre-treatment of such a separation process. Regardless of the adhesive types, the immersion treatment increased the water content of adhesives, which led to their plasticization and volume expansion, determined by DSC and FT-IR analyses. Along with this, the tensile strength, dielectric strength, and volume resistivity of adhesive were found to greatly decrease, and this decreasing trend was more visible with lower NaCl concentration. Overall, our results suggested that immersion treatment can be a promising pre-treatment for an easy disassembly process with manual dismantling or electric pulse method.
