WO3 photocatalyst decorated with highly dispersed CoWO4 or CuWO4 nanoparticles(CoWO4/WO3 or CuWO4/WO3) was successfully synthesized using an in-situ impregnation method followed by solid-state reaction. The structure,...WO3 photocatalyst decorated with highly dispersed CoWO4 or CuWO4 nanoparticles(CoWO4/WO3 or CuWO4/WO3) was successfully synthesized using an in-situ impregnation method followed by solid-state reaction. The structure, morphology, photophysical property, and photocatalytic degradation mechanism of the CoWO4/WO3 or CuWO4/WO3 samples were investigated by XRD, SEM, TEM, EDS, HR-TEM, UV-vis DRS, SPV, and active trapping techniques. The XRD, SEM, and TEM results have revealed that CoWO4 or CuWO4 are highly dispersed on the WO3 surface, when the loading amount of CoWO4 or CuWO4 is small. However, obvious agglomeration is observed for the CoWO4 or CuWO4 particles, when the loading amount of CoWO4 or CuWO4 was increased. The visible-light photocatalytic degradation of RhB shows that all CoWO4/WO3 or CuWO4/WO3 samples exhibit superior photocatalytic performance as compared to pure WO3. This is mainly attributed to the formation of type II heterojunction between WO3 and CoWO4 or CuWO4, which can promote the photogenerated electrons and holes separation and transfer. Moreover, it is found that 0.2% CoWO4/WO3 or 0.2% CuWO4/WO3, in which MWO4 nanoparticles are uniformly dispersed on the surface of WO3, can achieve the most excellent photocatalytic activity among CoWO4/WO3 or CuWO4/WO3 samples, respectively. As compared with WO3, an enhancement about 9.1 times or 6.8 times in photocatalytic activity is observed on 0.2% CoWO4/WO3 or 0.2% CuWO4/WO3, respectively. Furthermore, the active species trapping experiment demonstrates that ·OH, h+, and ·O-2 generated during the photocatalytic process are all the reactive species in photocatalytic degradation of Rhodamine B(RhB) on CoWO4/WO3 or CuWO4/WO3. This study presents a strategy to design superior photocatalyst for organic compound degradation.展开更多
The mobility and bioavailability of selenium is a major health and environmental issue and a main concern for geological disposal of high-level radioactive waste. Chemically and/or microbially mediated oxidation of in...The mobility and bioavailability of selenium is a major health and environmental issue and a main concern for geological disposal of high-level radioactive waste. Chemically and/or microbially mediated oxidation of insoluble Se-bearing particulate, such as iron selenides, to dissolved and mobile phases controls the transport and distribution of Se in the environment. The oxidation of ferroselite （FeSe2） by ferric iron was investigated in anoxic conditions. The redox reaction can be represented by： FeSe2 ＋ 2Fe3＋ = 2Se^0 ＋ 3Fe2＋. Kinetic studies indicated that the reaction can be described by second-order rate law, with rate constants of 0.49±0.01, 0.85±0.02, 1.84±0.04, and 3.29±0.13 L mol^-1 s^-1 at pH 1.62, 1.87, 2.23, and 2.49, respectively. The positive correlation between reaction rate and pH implies that diffusion of Fe3＋ oxidant to the mineral surface is the rate-determining step. The strong reactivity of FeSe2 towards Fe^3＋ suggests that ferric iron may play a significant role in FeSe2 oxidation process （e.g., by Se^4＋, 02, etc.） and Se^0 should be the first reaction product. Also, it was shown that the reduction rate of Fe^3＋ or Se^4＋ by pyrite （FeS2） can be significantly increased in the presence of FeSe2, suggesting a stronger reactivity of FeSe2 compared with pyrite. The results obtained extend our knowledge about the subtle interaction between Se, pyrite and iron selenides in the environment, and give insight into the transfer of selenium from iron selenides to bio-available selenium （i.e., selenite and selenate） in the Se-rich environment.展开更多
基金supported financially by the National Natural Science Foundation of China(21573101)the Program for Liaoning Excellent Talents in University(LR2017011)+1 种基金the support plan for Distinguished Professor of Liaoning Province([2015]153)the Liaoning BaiQianWan Talents program([2017]96)
文摘WO3 photocatalyst decorated with highly dispersed CoWO4 or CuWO4 nanoparticles(CoWO4/WO3 or CuWO4/WO3) was successfully synthesized using an in-situ impregnation method followed by solid-state reaction. The structure, morphology, photophysical property, and photocatalytic degradation mechanism of the CoWO4/WO3 or CuWO4/WO3 samples were investigated by XRD, SEM, TEM, EDS, HR-TEM, UV-vis DRS, SPV, and active trapping techniques. The XRD, SEM, and TEM results have revealed that CoWO4 or CuWO4 are highly dispersed on the WO3 surface, when the loading amount of CoWO4 or CuWO4 is small. However, obvious agglomeration is observed for the CoWO4 or CuWO4 particles, when the loading amount of CoWO4 or CuWO4 was increased. The visible-light photocatalytic degradation of RhB shows that all CoWO4/WO3 or CuWO4/WO3 samples exhibit superior photocatalytic performance as compared to pure WO3. This is mainly attributed to the formation of type II heterojunction between WO3 and CoWO4 or CuWO4, which can promote the photogenerated electrons and holes separation and transfer. Moreover, it is found that 0.2% CoWO4/WO3 or 0.2% CuWO4/WO3, in which MWO4 nanoparticles are uniformly dispersed on the surface of WO3, can achieve the most excellent photocatalytic activity among CoWO4/WO3 or CuWO4/WO3 samples, respectively. As compared with WO3, an enhancement about 9.1 times or 6.8 times in photocatalytic activity is observed on 0.2% CoWO4/WO3 or 0.2% CuWO4/WO3, respectively. Furthermore, the active species trapping experiment demonstrates that ·OH, h+, and ·O-2 generated during the photocatalytic process are all the reactive species in photocatalytic degradation of Rhodamine B(RhB) on CoWO4/WO3 or CuWO4/WO3. This study presents a strategy to design superior photocatalyst for organic compound degradation.
基金supported by the Special Foundation for High-Level Radioactive Waste Disposal(2007-840,2012-851)the National Natural Science Foundation of China(11075006,91026010)+1 种基金the China Postdoctoral Science Foundation Project(2013M530013)the Collaborative Project from the Key Laboratory of Mineralogy and Metallogeny,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences(KLMM20120203)
文摘The mobility and bioavailability of selenium is a major health and environmental issue and a main concern for geological disposal of high-level radioactive waste. Chemically and/or microbially mediated oxidation of insoluble Se-bearing particulate, such as iron selenides, to dissolved and mobile phases controls the transport and distribution of Se in the environment. The oxidation of ferroselite （FeSe2） by ferric iron was investigated in anoxic conditions. The redox reaction can be represented by： FeSe2 ＋ 2Fe3＋ = 2Se^0 ＋ 3Fe2＋. Kinetic studies indicated that the reaction can be described by second-order rate law, with rate constants of 0.49±0.01, 0.85±0.02, 1.84±0.04, and 3.29±0.13 L mol^-1 s^-1 at pH 1.62, 1.87, 2.23, and 2.49, respectively. The positive correlation between reaction rate and pH implies that diffusion of Fe3＋ oxidant to the mineral surface is the rate-determining step. The strong reactivity of FeSe2 towards Fe^3＋ suggests that ferric iron may play a significant role in FeSe2 oxidation process （e.g., by Se^4＋, 02, etc.） and Se^0 should be the first reaction product. Also, it was shown that the reduction rate of Fe^3＋ or Se^4＋ by pyrite （FeS2） can be significantly increased in the presence of FeSe2, suggesting a stronger reactivity of FeSe2 compared with pyrite. The results obtained extend our knowledge about the subtle interaction between Se, pyrite and iron selenides in the environment, and give insight into the transfer of selenium from iron selenides to bio-available selenium （i.e., selenite and selenate） in the Se-rich environment.
