Recovery of waste rare earth fluorescent powders by two steps acid leaching

The effects of the acid leaching and alkali fusion on the leaching efficiency of Y,Eu,Ce,and Tb from the waste rare earth fluorescent powders were investigated in this paper.The results show that hydrochloric acid is better than sulfuric acid in the first acid leaching,and NaOH is better than Na2CO3in the alkali fusion.In the first acid leaching,the Wloss is 20.94%when the waste rare earth fluorescent powders are acid leached in H?concentration 3 mol L-1and S/L ratio 1:3 for 4 h due to red powders dissolved.The better results of the alkali fusion can be got at 800℃ for 2 h when the NaOH is used.The blue powders and the green powders can be dissolved into NaAlO2and oxides such as rare earth oxide(REO).The REO can be dissolved in H?concentration 5 mol L-1,S/L1:10 for 3 h in the second acid leaching.The leaching rates of the Y,Eu,Ce,and Tb are 99.06%,97.38%,98.22%,and 98.15%,respectively.The leaching rate of the total rare earth is 98.60%.

Synthesis and Luminescence of Nano Fluorescent Powder of Y_4Al_2O_9:Eu^(3+)

Nano fluorescent powder of Y 4Al 2O 9:Eu 3+ was synthesized by sol gel method.The XRD shows that the product prepared at 900℃ is pure phase Y 4Al 2O 9:Eu 3+ .The Y 4Al 2O 9 powder is nano size crystal testified by BF and ED analysis of TEM.The grain diameter of Y 4Al 2O 9 is in the range between 20 and 50nm,and its average is 30nm.The luminescent spectra show that Eu 3+ ious occupy two kinds of sites in Y 4Al 2O 9 crystal lattice.One is in the strict inversion center,and the other is in off lying inversion center.When excited with UV light (λ=254nm),Y 4Al 2O 9:Eu 3+ exhibits an orange emission band at λ=590nm due to the 5D 0→ 7F 1 transition and a red emission band at λ=610nm due to 5D 0→ 7F 2 transition.

Simulated Microbe Removal around Finger Rings Using Different Hand Sanitation Methods

Aim It is our opinion that the CDC and the WHO have underestimated cross-contamination under examination gloves in dental clinics while wearing jewelry, such as finger rings. These agencies only ＂recommend＂ removing jewelry, and only washing hands for 15 seconds with soap and warm water before donning gloves. This study examined several washing procedures and finger rings using simulated microbes. Methodology A gloved robber hand manikin was made and fitted with a flesh disposable vinyl glove. Four fingers were fitted with rings or no ring, dusted with simulated microbes, and washed with a scrub brush for 5, 15, and 25 seconds under 20℃ and 40℃ water alone, or with liquid hand soap. Light levels （in lux） of fluorescent powder before and after washing were measured and delta scores calculated for changes in light levels, equivalent to effectiveness of hand washing procedures. A full-factorial, 3-factor analysis of variance （ANOVA） was used to test for differences among levels of the three study factors-time, temperature, and soap use. Tukey＇s post hoc honestly significant difference （HSD） test was applied to significant factors to examine pair-wise differences between factor levels. Results It was found that the longer the hands with rings were washed with a scrub brush under flowing water, the more simulated microbes were removed. By 25 seconds, all methods were essentially the same. Simulated microbes were more difficult to remove from the palm compared to the back of the hand. The liquid hand soap used in this study was more effective with warm water than cold. When given a choice of washing with cold water up to 15 seconds, it would be preferable not to use soap to remove simulated microbes. Qualitatively, the outer surface of finger rings were more effectively cleaned than the crevice below the ring, and the ring with a stone setting appeared to accumulate and retain simulated microbes more than other rings. Conclusion The most effective treatment was washing with warm water and liquid soap. Longer times were more effective. Rings should not be worn under examination gloves due to difficulty cleaning in the crevice under the ring, and the well-known consequences of cross-contamination between the patient and the health care worker.

Movement Patterns of the Eastern Chipmunk (<i>Tamias striatus</i>) in Four Fragmented Landscapes of Prince Edward Island, Canada

The analysis of animal movement patterns can provide important information on animals’ responses to habitat features. In this study, the movement paths of eastern chipmunks (Tamias striatus) were examined in four landscapes, with different levels of habitat fragmentation, using either fluorescent powdering or spool-and-line tracking. Descriptions of the tree and ground vegetation communities were performed in the vicinity of the trail to obtain information on habitat use and habitat selection. Several key movement variables were calculated, including the total path length, net distance, fractal dimension, and radius of gyration. Despite statistically significant differences in some of the movement metrics between the four landscapes, the overall movement patterns were generically the same for all of chipmunk paths examined in this study. The data were compared to trends expected based on random or correlated random walks, as well as Lévy-walk models. The mean squared net displacement did not support the correlated random walk predictions, except at smaller spatial scales, but overall demonstrated Lévy-like super diffusive behaviour. Lévy-like patterns were also confirmed from the move-length distributions that demonstrated truncated-tail power-law behaviour. Although this would suggest invariance of the movement patterns at all spatial scales studied, fractal analysis revealed at least two transitions in movement patterns at scales of around 2 and 5 m. The transition point at 2 m was negatively correlated with the density of small trees, while the transition at ~5 m was positively correlated with the spatial distribution of large trees. As the habitat-preference data showed that small trees are among the least preferred habitat component, while large trees were among the most preferred habitat, chipmunks are likely to alter their movement behaviour to avoid small trees, and attracted towards large trees possibly to avoid predators. Overall, we determined three principal domains of movement: at smaller spatio-temporal scales, foraging activities dominate and the movement is highly correlated but also random;at intermediate spatial scales, chipmunks may be moving to avoid predators, using different environmental cues, and the movement is more directed (but still influenced by vegetation patterns at intermediate scales);at larger spatio-temporal scales, the movement is dominated by long-range/long-term memory and homing to burrows and other key habitat features, such as food caches, drives more directed movement. The fact that scale-dependent movement mechanisms could give rise to LW patterns is consistent with recent studies.

Selective extraction and recovery of rare earth metals from waste fluorescent powder using alkaline roasting-leaching process

Waste management of rare earth metals（REMs） containing materials and recycling of rare earth metals（REM） from waste materials are becoming more and more important due to high demand and resource exhaustion. However, extraction of REM from waste fluorescent powder materials is difficult because of their special aluminate structure. A novel ＂alkaline roasting-acid leaching＂ process was developed in this study. The alkaline roasting process mechanism was examined using differential thermal analysis（DTA）-thermogravimetric（TG） measurements, and the roasting product was characterized by XRD analysis. In this process, Al_2O_3 was converted into water soluble NaAlO_2 via alkaline roasting, and NaAlO_ 2 in the roasting product could be easily dissolved in water, while the rare earth oxide（REOs） remained as solid. After filtration, REOs cake was leached using hydrochloric acid to achieve 99.8% of REM recovery. It was concluded that the alkaline roasting-acid leaching process could effectively separate Al_2O_3 and REOs with high REM recovery.

Luminescence properties of Cd Te QDs embedded in Zn_5(CO_3)_2(OH)_6 matrix

CdTe@Zn5（CO3）2（OH）G composites were synthesized by a hydrothermal method. CdTe@Zn5（CO3）2（OH）6 composite nanospheres were characterized via X-ray diffraction, scanning electron microscopy, energy- dispersive X-ray spectroscopy, and photoluminescence （PL）. The hydrothermal reaction time and the mole ratios of Zn/Te played important roles in the growth and fluorescence intensity of CdTe@Zn5（CO3）2（OH）6 composites. The composite powders showed peak PL at 578 nm at 1.6 times the intensity of powdered CdTe QDs. CdTe@Zn5（CO3）2（OH）6 exhibited a strong yellow fluorescence emission, and its preparation method was easy and economical. Therefore, CdTe@Zn5（CO3）2（OH）6 offers potential applications in biological markers and light-emitting diodes.