Reductive melting treatment has been reported to be an effective method to recover lead from funnel glass in used cathode ray tubes, but a small amount of lead, a potential contaminant, remains in the treated glass. This paper applied a combination process of reductive and oxidative melting to the funnel glass to recover and immobilize lead in the glass. The funnel glass was melted in a lab‐scale reactor changing the atmosphere, and the effects of the temperature and the Na2CO3 dosage on the efficiencies of the lead recovery and immobilization were investigated. In the reductive melting, the lead recovery was promoted by increasing the Na2CO3 dosage, however the lead extraction from the glass into water and hydrochloric acid was increased. Although the content of lead in the glass after the reductive melting was low, the lead extraction into water and the acid was larger than 0.01 mg‐Pb/L‐water and 150 mg‐Pb/kg‐glass, respectively (Japanese environmental criteria). The lead extraction was decreased by the oxidative melting with SiO2, Al2O3, MgO, and NaNO3. In the proposed method, metallic lead was recovered from the funnel glass with high lead recovery, and the lead remaining in the glass was immobilized to meet the Japanese environmental criteria.

Mining activities often generate large amounts of sulfide-rich wastes containing arsenopyrite (FeAsS), which when dissolved releases toxic arsenic (As) and generates acid mine drainage (AMD) that are both disastrous to the environment. To suppress arsenopyrite dissolution, a technique that selectively coats sulfide minerals with a protective layer of Al-oxyhydroxide called Al-based carrier-microencapsulation (CME) was developed. Although a previous study of the authors showed that Al-based CME could significantly limit arsenopyrite dissolution, nature of the coating formed on arsenopyrite, including its electrochemical properties, is still not well understood. Moreover, stability of the coating once exposed to weathering conditions remains unclear. Better understanding of these important issues would greatly improve Al-based CME especially in its application to real mine wastes. In this study, nature of the coating formed by Al-based CME was investigated using SEM-EDX, DRIFTS and XPS while the electrochemical properties of the coating were evaluated by cyclic voltammetry and chronoamperometry. Meanwhile, stability of the coating was elucidated using consecutive batch leaching experiments and weathering cell tests.SEM-EDX, DRIFTS and XPS results indicate that the protective coating formed on arsenopyrite by Al-based CME was mainly composed of bayerite (α-Al(OH) 3 ), gibbsite (γ-Al(OH) 3 ), and boehmite (γ-AlO(OH)). These Al-based coatings, which have insulating properties, made arsenopyrite less electrochemically active. The coatings also limited the extent of both the anodic and cathodic half-cell reactions of arsenopyrite oxidation that suppressed As release and acid generation. Weathering cell tests indicated that the oxidation of CME-treated arsenopyrite was effectively limited until about 15 days but after this, it started to gradually progress with time due to the increasing acidity of the system where Al-based coatings became unstable. Nonetheless, CME-treated arsenopyrite was less oxidized based on the released amounts of Fe, As and S suppressed by 80, 60 and 70%, respectively, compared with the one treated with control.

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This paper discusses partial discharge (PD) propagation, degradation and lifetime characteristics of magnet wires for inverter-fed motor under surge voltage application.Experimental results showed the time variation of PD activity, i.e. intermittent PD, successive PD, critical PD and breakdown (BD), under repetitive surge voltage application with a fixed peak value. Critical PD was a drastic change of PD activity and was identified as the partial BD of magnet wires. Since the final BD was confirmed to be always induced at the critical PD location, the critical PD was regarded as an important indicator to determine the lifetime of magnet wires. The experimental results also clarified that the lifetime of magnet wires could be determined by the total number of PD generation from its inception to breakdown. PD activity was interpreted by the time transition of PD generation frequency, and its mechanisms were discussed.

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