Sedum alfredii Hance has been identified as a new Zn-hyperaccumulator native to China. In this study, responses and metal accumulation of S alfredii were examined under Zn/Cd complex polluted conditions. The results s...Sedum alfredii Hance has been identified as a new Zn-hyperaccumulator native to China. In this study, responses and metal accumulation of S alfredii were examined under Zn/Cd complex polluted conditions. The results showed that optimal growth of S alfredii in terms of the maximum dry matter yield was observed at Zn/Cd complex level of 500/100 mumol/L. Plant cadmium (Cd) or zinc (Zn) concentrations increased with increasing Cd or Zn supply. During the 20 d treatment, the highest Cd concentration in the leaves reached 12.1 g/kg at Zn/Cd level of 50/400 mumol/L and that of Zn in the stems was 23.2 g/kg at Zn/Cd level of 1000/50 mumol/L. The distribution of Cd in different plant parts decreased in the order: leaf > stem greater than or equal to root, whereas that of Zn was: stem > leaf greater than or equal to root. The accumulation of Cd and Zn in the shoots and roots of S. alfredii increased with the increasing of Zn/Cd supply levels, peaked at Zn/Cd levels of 250/400 and 500/100 mumol/L, respectively. The highest Cd and Zn uptake by the shoots was approximately 5 and 11 mg/plant, and was over 20 and 10 times higher than those in the roots, respectively. Zn supply at levels less than or equal to 500 mumol/L increased plant Cd concentrations, whereas high Zn supply decreased root Cd but did not affect leaf Cd concentrations in S alfredii Low Cd supply increased Zn concentration in the leaves, but Cd supply higher than 50 mumol/L considerably reduced root Zn concentrations, especially at low Zn level. These results indicate that S. alfredii can tolerate high Zn/Cd complex levels and has an extraordinary ability to hyperaccumulate not only Zn but also Cd. It could provide a new valuable plant material for understanding the mechanisms responsible for co-hyperaccumulation of Zn and Cd as well as for phytoremediation of the Cd/Zn complex polluted soils.展开更多
It is important to remove the impurities, such as copper and cadmium, from leaching solution in zinc hydrometallurgy. To improve purification efficiency, a replacement-column purification device was proposed and its m...It is important to remove the impurities, such as copper and cadmium, from leaching solution in zinc hydrometallurgy. To improve purification efficiency, a replacement-column purification device was proposed and its mass transfer characteristics and purification efficiency were experimentally studied. The results show that purification efficiency increases with the decrease of the zinc powder diameter and decreases with the increase of solution velocity. If appropriate structure and operation parameters are used, it is possible to make purification efficiency more than 99%, but the diameter of zinc powder should be larger than 0.45 mm. For the velocity of 0.05-0.7 cm/s, mass transfer coefficient kc is in the range of 3.94×10-7-2.76×10-6 m/s, and increases with the decrease of zinc powder diameter and the increase of solution velocity. Moreover, it can be derived by mass transfer correlations of Sherwood number:Sh=0.1069Re0.5Sc0.33, for 0.3<Re<6.展开更多
This research has focused on the treatment of zinc flue dust by an acid leach process, combining an environmentally suitable impurity removal process to recover cadmium. Optimum conditions were found as follows： H2SO...This research has focused on the treatment of zinc flue dust by an acid leach process, combining an environmentally suitable impurity removal process to recover cadmium. Optimum conditions were found as follows： H2SO4 concentration 90 g/L, liquid/solid ratio 6：1, leaching temperature 60 ℃ and leaching time 1.0 h. Under these conditions, 95.8% cadmium was recovered. FeAsO4 and Fe（OH）3 precipitates with FeCI3 are found to be highly effective to obtain a high degree of separation of heavy metals and the oxyanions of arsenic from the leachate. The overall separation of arsenic and other heavy metals and precipitate settling rates are optimum at n（Fe）/n（As） ratio of 3：l and pH 6. The removal rates ofFe, Pb and Cu from the solution were greater than 98.9%, and As removal rate was 99.6%. A solvent extraction with P204 was used for the separation of zinc and cadmium. Optimum conditions are obtained as follows： 20% P204 （volume fraction） diluted with kerosene at room temperature, pH 3.0, and varying organic/aqueous （O/A） phase ratio 1：1. The extraction rate of zinc is 99.2% under these conditions. Spherical cadmium particles showing nearly uniform size were produced by hydrogen reduction at 310 ℃ and the crystal structure was cubic. In addition, the purity of the recovered cadmium powder is more than 99.99%.展开更多
In this work,a novel plasmon-assisted UV-vis-NIR-driven W_(18)O_(49)/Cd_(0.5)Zn_(0.5)S heterostructure photocatalyst was obtained by a facile ultrasonic-assisted electrostatic self-assembly strategy.The hybrid exhibit...In this work,a novel plasmon-assisted UV-vis-NIR-driven W_(18)O_(49)/Cd_(0.5)Zn_(0.5)S heterostructure photocatalyst was obtained by a facile ultrasonic-assisted electrostatic self-assembly strategy.The hybrid exhibits extraordinary H2 evolution activity of 147.7 mmol·g^(-1)·h^(-1) at room temperature due to the efficient charge separation and expanded light absorption.Our investigation shows that the unique Step-scheme(S-scheme)charge transfer and the‘hot electron’injection are both responsible for the extraordinary H2 evolution process,depending on the wavelength of the incident light.Moreover,by accelerating the surface reaction kinetics,the activity can be further elevated to 306.1 mmol·g^(-1)·h^(-1),accompanied by a high apparent quantum yield of 45.3% at 365±7.5 nm.This work provides us a potential strategy for the highly efficient conversion of the solar energy by elaborately combining a nonstoichiometric ratio plasmonic material with an appropriate active photocatalyst.展开更多
H2 is an important energy carrier for replacing fossil fuel in the future due to its high energy density and environmental friendliness.As a sustainable H2-generation method,photocatalytic H2 production by water split...H2 is an important energy carrier for replacing fossil fuel in the future due to its high energy density and environmental friendliness.As a sustainable H2-generation method,photocatalytic H2 production by water splitting has attracted much interest.Here,oil-soluble ZnxCd1-xS quantum dot(ZCS QD)with a uniform particle size distribution were prepared by a hot-injection method.However,no photocatalytic H2-production activity was observed for the oil-soluble ZCS QD due to its hydrophobicity.Thus,the oil-soluble ZCS QD was converted into a water-soluble ZCS QD by a ligand-exchange method.The water-soluble ZCS QD exhibited excellent photocatalytic H2-production performance in the presence of glycerin and Ni^2+,with an apparent quantum efficiency of 15.9%under irradiation of 420 nm light.Further,the photocatalytic H2-generation activity of the ZCS QD was~10.7 times higher than that of the ZnxCd1-xS relative samples prepared by the conventional co-precipitation method.This work will inspire the design and fabrication of other semiconductor QD photocatalysts because QD exhibits excellent separation efficiency for photogenerated electron-hole pairs due to its small crystallite size.展开更多
Iin this paper an isosbestic dual--wavelength spectrophotometric method for the simultaneous determination of zinc and cadmium using meso--tetrakis [4-(trimethylammonium) phenyl] porphine has been developed. The inter...Iin this paper an isosbestic dual--wavelength spectrophotometric method for the simultaneous determination of zinc and cadmium using meso--tetrakis [4-(trimethylammonium) phenyl] porphine has been developed. The interference from excess of reagent was masked by adding lead ions solution.The molar absorptivities (Ae) for zinc and cadmium were 6. 54 × 105 and 4. 27 × 105 L. mol-1. cm-1,respectively. The method could be used to determine zinc and cadmium in synthetic mixtures, and the satisfied results were obtained.展开更多
Photocatalytic water splitting is an economical and sustainable pathway to use solar energy for large‐scale H2production.We report a highly efficient noble‐metal‐free photocatalyst formed by integrating amorphous N...Photocatalytic water splitting is an economical and sustainable pathway to use solar energy for large‐scale H2production.We report a highly efficient noble‐metal‐free photocatalyst formed by integrating amorphous NiS with a CdS nanorods(NRs)/ZnS heterojunction material for photocatalytic H2production in water under visible light irradiation(?>420nm).The results show that the photocatalytic H2production rate reaches an optimal value of up to574μmol·h–1after the loading of NiS,which is more than38times higher than the catalytic activity of pure CdS NRs.The average apparent quantum yield is^43.2%during5h of irradiation by monochromatic420nm light.The present study demonstrates the advantage of integration strategies to form not only semiconductor heterojunctions but also photocatalyst‐cocatalyst interfaces to enhance the catalytic activity for photocatalytic H2production.展开更多
文摘Sedum alfredii Hance has been identified as a new Zn-hyperaccumulator native to China. In this study, responses and metal accumulation of S alfredii were examined under Zn/Cd complex polluted conditions. The results showed that optimal growth of S alfredii in terms of the maximum dry matter yield was observed at Zn/Cd complex level of 500/100 mumol/L. Plant cadmium (Cd) or zinc (Zn) concentrations increased with increasing Cd or Zn supply. During the 20 d treatment, the highest Cd concentration in the leaves reached 12.1 g/kg at Zn/Cd level of 50/400 mumol/L and that of Zn in the stems was 23.2 g/kg at Zn/Cd level of 1000/50 mumol/L. The distribution of Cd in different plant parts decreased in the order: leaf > stem greater than or equal to root, whereas that of Zn was: stem > leaf greater than or equal to root. The accumulation of Cd and Zn in the shoots and roots of S. alfredii increased with the increasing of Zn/Cd supply levels, peaked at Zn/Cd levels of 250/400 and 500/100 mumol/L, respectively. The highest Cd and Zn uptake by the shoots was approximately 5 and 11 mg/plant, and was over 20 and 10 times higher than those in the roots, respectively. Zn supply at levels less than or equal to 500 mumol/L increased plant Cd concentrations, whereas high Zn supply decreased root Cd but did not affect leaf Cd concentrations in S alfredii Low Cd supply increased Zn concentration in the leaves, but Cd supply higher than 50 mumol/L considerably reduced root Zn concentrations, especially at low Zn level. These results indicate that S. alfredii can tolerate high Zn/Cd complex levels and has an extraordinary ability to hyperaccumulate not only Zn but also Cd. It could provide a new valuable plant material for understanding the mechanisms responsible for co-hyperaccumulation of Zn and Cd as well as for phytoremediation of the Cd/Zn complex polluted soils.
基金Project(Y2010-1-005)supported by the Collaborative Fund of Hunan Nonferrous Metals Holding Group-Central South University,China
文摘It is important to remove the impurities, such as copper and cadmium, from leaching solution in zinc hydrometallurgy. To improve purification efficiency, a replacement-column purification device was proposed and its mass transfer characteristics and purification efficiency were experimentally studied. The results show that purification efficiency increases with the decrease of the zinc powder diameter and decreases with the increase of solution velocity. If appropriate structure and operation parameters are used, it is possible to make purification efficiency more than 99%, but the diameter of zinc powder should be larger than 0.45 mm. For the velocity of 0.05-0.7 cm/s, mass transfer coefficient kc is in the range of 3.94×10-7-2.76×10-6 m/s, and increases with the decrease of zinc powder diameter and the increase of solution velocity. Moreover, it can be derived by mass transfer correlations of Sherwood number:Sh=0.1069Re0.5Sc0.33, for 0.3<Re<6.
文摘This research has focused on the treatment of zinc flue dust by an acid leach process, combining an environmentally suitable impurity removal process to recover cadmium. Optimum conditions were found as follows： H2SO4 concentration 90 g/L, liquid/solid ratio 6：1, leaching temperature 60 ℃ and leaching time 1.0 h. Under these conditions, 95.8% cadmium was recovered. FeAsO4 and Fe（OH）3 precipitates with FeCI3 are found to be highly effective to obtain a high degree of separation of heavy metals and the oxyanions of arsenic from the leachate. The overall separation of arsenic and other heavy metals and precipitate settling rates are optimum at n（Fe）/n（As） ratio of 3：l and pH 6. The removal rates ofFe, Pb and Cu from the solution were greater than 98.9%, and As removal rate was 99.6%. A solvent extraction with P204 was used for the separation of zinc and cadmium. Optimum conditions are obtained as follows： 20% P204 （volume fraction） diluted with kerosene at room temperature, pH 3.0, and varying organic/aqueous （O/A） phase ratio 1：1. The extraction rate of zinc is 99.2% under these conditions. Spherical cadmium particles showing nearly uniform size were produced by hydrogen reduction at 310 ℃ and the crystal structure was cubic. In addition, the purity of the recovered cadmium powder is more than 99.99%.
文摘In this work,a novel plasmon-assisted UV-vis-NIR-driven W_(18)O_(49)/Cd_(0.5)Zn_(0.5)S heterostructure photocatalyst was obtained by a facile ultrasonic-assisted electrostatic self-assembly strategy.The hybrid exhibits extraordinary H2 evolution activity of 147.7 mmol·g^(-1)·h^(-1) at room temperature due to the efficient charge separation and expanded light absorption.Our investigation shows that the unique Step-scheme(S-scheme)charge transfer and the‘hot electron’injection are both responsible for the extraordinary H2 evolution process,depending on the wavelength of the incident light.Moreover,by accelerating the surface reaction kinetics,the activity can be further elevated to 306.1 mmol·g^(-1)·h^(-1),accompanied by a high apparent quantum yield of 45.3% at 365±7.5 nm.This work provides us a potential strategy for the highly efficient conversion of the solar energy by elaborately combining a nonstoichiometric ratio plasmonic material with an appropriate active photocatalyst.
文摘H2 is an important energy carrier for replacing fossil fuel in the future due to its high energy density and environmental friendliness.As a sustainable H2-generation method,photocatalytic H2 production by water splitting has attracted much interest.Here,oil-soluble ZnxCd1-xS quantum dot(ZCS QD)with a uniform particle size distribution were prepared by a hot-injection method.However,no photocatalytic H2-production activity was observed for the oil-soluble ZCS QD due to its hydrophobicity.Thus,the oil-soluble ZCS QD was converted into a water-soluble ZCS QD by a ligand-exchange method.The water-soluble ZCS QD exhibited excellent photocatalytic H2-production performance in the presence of glycerin and Ni^2+,with an apparent quantum efficiency of 15.9%under irradiation of 420 nm light.Further,the photocatalytic H2-generation activity of the ZCS QD was~10.7 times higher than that of the ZnxCd1-xS relative samples prepared by the conventional co-precipitation method.This work will inspire the design and fabrication of other semiconductor QD photocatalysts because QD exhibits excellent separation efficiency for photogenerated electron-hole pairs due to its small crystallite size.
文摘Iin this paper an isosbestic dual--wavelength spectrophotometric method for the simultaneous determination of zinc and cadmium using meso--tetrakis [4-(trimethylammonium) phenyl] porphine has been developed. The interference from excess of reagent was masked by adding lead ions solution.The molar absorptivities (Ae) for zinc and cadmium were 6. 54 × 105 and 4. 27 × 105 L. mol-1. cm-1,respectively. The method could be used to determine zinc and cadmium in synthetic mixtures, and the satisfied results were obtained.
基金supported by the National Key Research and Development Program of China(2017YFA0402800)the National Natural Science Foundation of China(51772285,21473170)~~
文摘Photocatalytic water splitting is an economical and sustainable pathway to use solar energy for large‐scale H2production.We report a highly efficient noble‐metal‐free photocatalyst formed by integrating amorphous NiS with a CdS nanorods(NRs)/ZnS heterojunction material for photocatalytic H2production in water under visible light irradiation(?>420nm).The results show that the photocatalytic H2production rate reaches an optimal value of up to574μmol·h–1after the loading of NiS,which is more than38times higher than the catalytic activity of pure CdS NRs.The average apparent quantum yield is^43.2%during5h of irradiation by monochromatic420nm light.The present study demonstrates the advantage of integration strategies to form not only semiconductor heterojunctions but also photocatalyst‐cocatalyst interfaces to enhance the catalytic activity for photocatalytic H2production.
