Recycling high-purity rare earths from the waste in fluorescent lamps will assist in preserving rare earth resources. However, the present recovery from the waste in fluorescent lamps is very low at around 30%, and most waste fluorescent lamps are reclaimed. In this study we attempted to reduce one cause of difficulty in recycling lamps, namely the identification of rare earths in plastic-covered lamps, which is conventionally executed by human operators. Using the Acoustic Emission (AE) signal of the collision sound between lamps and an AE sensor head, we first carried out waveform analysis, and frequency analysis using the discrete Fourier transform. We extracted six feature values for each analysis and differentiated the plastic-covered lamps using thresholds. The least error rates were 4.85% and 6.67% for the waveform and frequency analyses, respectively. Second, we applied discriminant analysis on the six feature values from each analysis, resulting in error rates of 3.03% and 5.45%, respectively. Third, we extracted six feature values from the time-frequency analysis using the discrete Wavelet transform and Fractal dimensioning, and applied discriminant analysis on the six feature values, resulting in an error rate of 4.24%. Finally, we examined all the results from the three analyses to find the best combination of feature values, applied discriminant analysis to 12 feature values from the time analysis and time-frequency analysis, and succeeded in reducing the error rate to 0%.
The Pb oxide and Ru oxide films with various compositions were prepared by reactive sputtering using mixed gas of Ar and O2, and those anodic polarization properties were investigated in a 150 g L-1 H2SO4 solution at 303–333 K. When O2 amount of the Ar-O2 mixed gas was 25 vol.% or more, the product thin films were identified as mixed phase of α-PbO2 and β-PbO2 for the reactive sputtering of Pb target. On the other hand, the products were single phase of RuO2 for the reactive sputtering of Ru target at the same O2 amount of the mixed gas. The anode potential of the metallic Pb thin film was equal to that of the PbO2 thin film at the current density of 10 mA cm-2 or more. So, it can be judged that the surface of the Pb-based alloy anode was covered with the PbO2 at 60 mA cm-2, which is a typical current density during the operation of zinc electrowinning, and the oxygen evolution overpotential of the PbO2 determined the bath voltage of the electrowinning. Moreover, the anodic polarization measurement showed that the anode potential of the RuO2 at 60 mA cm-2 was about 560 mV lower than that of the PbO2. Therefore, the remarkable decrease of the anode potential for the Pb-based powder rolling anode, in which the RuO2 powders were dispersed in the Pb substrate, was probably due to an extremely low oxygen evolution overpotential of the RuO2 in itself.