| Environmental pollution becomes more and more seriously with the rapid economic development, particularly for the water pollution problem. Common methods of pollutant treatment include:physical adsorption, chemical oxidation, microbial processing, high-temperature incineration and photocatalytic technology. Because of its energy efficiency (utilization of natural light), high efficient and non-toxic, the method of semiconductor photocatalytic has become a focus of research. Zinc oxide is a good photocatalytic material, which can be used for biological degradation, water treatment, and light catalyst such as sterilization.Ce3+, and Pr3+, and Gd3+and Ho3+rare earth single doped and the Ce-Ho and the Pr-Gd co-doped nano-ZnO powder are preparated by polymer network. XRD, TEM, UV-vis spectrophotometer, UV-Vis, and other advanced testing methods are used for characterization of structure and performance of the samples, and the influence of rare earth ion doped nano-ZnO on performance of grain size, morphology and photo catalytic are studied.Orthogonal design of experiment has been used to determine the optimal conditions for the photocatalytic experiment: the inputs samples is0.3g/50ml, initial concentration of MB solution is10mg/L, and pH value is6.5. Photocatalytic activity of Ce-doped sample increases with Ce3+doped content increasing, and the optimal content is0.18mol%with the highest catalytic activity. After fitting-linear, sample C0~C10photocatalytic degradation process are in line with the level of dynamic equations. Samples with high kinetic constants showed better photo-catalytic degradation performance. C6showed the highest photocatalytic activity, with the maximum kinetic constant11.1x10-3min-1. XRD test results showed that Ce-doped samples are hexagonal wurtzite structure, with good crystallization degree at around90%. Distinct red shift, about40nm, is found in Ce-doped samples, and C2had the largest red shift, about47nm. Through the analysis of TEM, Ce-doped samples are hexagonal wurtzite structure, and grain size is approximately about80nm with the stripe width of0.232nm between parallel surfaces. Under ultraviolet light, photocatalytic activity of Ce-doped sample increased as Ce can be part of the ZnO lattice, leading imbalance of electric charge, and can introduce impurities in the sample improving photocatalytic properties of the sample and broadening the absorption spectrum of the sample.Pr3+doped can significantly improve the photo-catalytic of nano-ZnO powder. As Pr3+content increased, photocatalytic activity of nano-ZnO first increased first and then declined slightly, optimal Pr content is0.18mol%. After fitting-linear, photocatalytic degradation process of Pr3+doped sample are in line with the level of dynamic equations. Samples P5showed the best photo-catalytic degradation performance with highest kinetic constants of10.22x10-3min-1. XRD results show that Pr3+doped nano-ZnO powder samples are hexagonal wurtzite structure. The average particle size of P5is44.89nm, and Pr3+doping caused structural change of the ZnO crystal, inducing lattice distortion. TEM results show that the micro-morphology of grain samples P5are the spherical particles with hexagonal wurtzite, grain size is about40-50nm, according with the XRD analysis results. Degrees of red shift nano-ZnO doped vary with rare earth Pr content, causing reduction of band width of Pr doped samples. Under ultraviolet light, photocatalytic activity of Pr-doped sample increased as Pr can be part of the ZnO lattice, leading imbalance of electric charge, and can introduce impurities in the sample improving photocatalytic properties of the sample and broadening the absorption spectrum of the sample.Gd3+rare earth doped can significantly improve photo-catalytic effect of Nano-ZnO powder, as Gd3+mixing volumes increase, photocatalytic activity of nano-ZnO first increase after declining, the best content for Gd3+doped is0.09mol%,4h degradation rate reached92.68%. Degradation of methylene blue by kinetic analysis indicates that the sample procedure substantially complies with kinetic equation, sample level kinetic constants of G4up to10.99x10-3min-1. XRD shows that Gd3+doped Nano-ZnO is hexagonal wurtzite. Structure of powder samples have good crystallinity and lattice distortion induced by rare-earth-doped, and vary the grain size. TEM results show that, micro grain morphology of Gd3+doped Nano-ZnO sample-,G4is hexagonal wurtzite spherical, grain size is approximately50-60nm. Gd doped Nano-ZnO powed have varying degrees of redshift, sample band width are narrow, which absorbs longer wavelength light in photocatalytic. Infrared analysis spectrum displayed, preparation of Gd doping samples has changed Zn-O vibration frequency of features location, makes its moved from490cm-1and415cm-1blue to500cm-1. The mechanism of Gd doping samples in purple light to light catalytic activity is because Gd part in ZnO lattice which in the led to charge does not balance, and samples in the introduced impurities-level in to improve samples of light catalytic performance and widening samples of absorption spectrometry.Ho3+rare earth doped can significantly improve photo-catalytic effect of Nano-ZnO powder, as Ho3+mixing volumes increase, photocatalytic activity of nano-ZnO first increase after declining, the best content for Ho3+doped is0.12mol%,4h degradation rate reached91.22%.After fitting-linear, photocatalytic degradation process of sample H0～H9are in line with the level of dynamic equations, linear correlation than high; H5kinetic constants is maximum, up to9.9×10-3min-1. XRD results show that the doping samples is hexagonal wurtzite.The structure of simples have good crystallinity and particle decrease. UV-Vis show, Ho has moved slightly blue, blue-shift is not obvious, not much band width increases. TEM analysis showed that with Ho doped, samples is hexagonal wurtzite, the grain size is approximately about80nm, stripe width of0.267nm between parallel surface. The mechanism of Ho doping samples in purple light to light catalytic activity is because Gd part in ZnO lattice which in the led to charge does not balance, and samples in the introduced impurities-level in to improve samples of light catalytic performance and widening samples of absorption spectrometry.Rare earth co-doped Nano-ZnO powder can significantly improve photo-catalytic effect, increasely as time increases, dynamic analysis showed that samples broadly in line with the process of degradation of methylene blue by Kinetic equations, sample CH, PG level kinetic constants are10.71×10-3min-1and10.13×10-3min-1, respectively. The results of XRD phase analysis show that rare-earth doped Nano-ZnO crystal structure has not changed, is still hexagonal wurtzite structure, crystallinity is become large, lattice distortion is large, all doping increases crystallinity of the sample. |
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