Rare earth elements are indispensable raw materials for advanced aero-engines, special optical materials, and high-performance electronic products. With the development of the social economy, the global demand for rar...Rare earth elements are indispensable raw materials for advanced aero-engines, special optical materials, and high-performance electronic products. With the development of the social economy, the global demand for rare earth resources is increasing, and rare earths have become a key metal for the development of new industries and frontier technologies that are highly valued both at home and abroad. Ion-adsorbed rare earth ores are an important source of rare earths, so the efficient green leaching of ion-adsorbed rare earths is important. Researchers found that the selection of an efficient green leaching agent for ion-adsorbed rare earths is based on the zeta potential of tailing clay minerals in addition to leaching efficiency, and both zeta potential and leaching ion concentration are related to mineral acidity and alkalinity, and the pH of tailing water suspension is a direct indicator of environmental water quality requirements. Therefore, the efficiency of the leaching process is closely integrated with the environmental evaluation, and the characteristics and correlation of the changes in zeta potential, pH, conductivity and pollutant concentration of the pulp of clay mineral content during the leaching process of ore leaching and tailings aqueous electrolyte solution leaching are studied by evaluating the leaching system, and a set of correlation leaching efficiency and environmental impact evaluation method is established based on the results of the above analysis, which is of scientific development of ion adsorption rare earth resources. It has important theoretical significance and practical application value.展开更多
The construction and functionalization of lanthanide-organic cages have been a research hotspot in coordination chemistry.Benefiting from the unique luminescent and magnetic properties of lanthanide ions,the potential...The construction and functionalization of lanthanide-organic cages have been a research hotspot in coordination chemistry.Benefiting from the unique luminescent and magnetic properties of lanthanide ions,the potential applications of lanthanide-organic cages in biological imaging applications are promising,but only a few corresponding explorations have been reported.He rein,we introduced a series of lanthanide tetrahedral cages,(Eu_(n)Gd_(4-n)L_(4))(sol)_8(n=0,1,2,3 and 4,where L=(4,4',4"-tris(4,4,4-trifluoro-1,3-dioxobutyl)-triphenylamine,and sol=dimethyl sulfoxide and methanol),with potential applications in biological imaging.Given the good luminescent and magnetic properties of Eu^(3+) and Gd^(3+) ions,Eu_(4)L_(4) and Gd_(4)L_(4) complexes show a high luminescence quantum yield of 29% in DMSO and large longitudinal relaxivity(r_(1)) of 11.4(mmol/L)^(-1)/s at 0.5 T in water containing 1 vol% DMSO,respectively.The heterobimetallic Eu-Gd complexes achieve a dual imaging mode by combining luminescent and magnetic centers in one cage.When the Gd:Eu ratio increases from 1:3 to 3:1,the r_(1) values increases from 5.33 to 8.64(mmoI/L)^(-1)/s,higher than that of commercial contrast agent Gd-DOTA(3.23(mmol/L)^(-1)/s).Owing to their low toxicity and good cell imaging ability toward ECA 109 cells,the selfassembled Eu-Gd heterobimetallic tetrahedral cages could be potential candidates for the multimodal imaging contrast agent.展开更多
The leaching efficiency(LE) of ion adsorption rare earth(IARE) by the sulfate and chloride of ammonium,magnesium and aluminum were comparatively determined using column leaching method. It is found that at equal equiv...The leaching efficiency(LE) of ion adsorption rare earth(IARE) by the sulfate and chloride of ammonium,magnesium and aluminum were comparatively determined using column leaching method. It is found that at equal equivalent concentration of cation, the LE of IARE by aluminum sulfate is the highest, and the zeta potential of clay mineral particles in the tailing is near to zero, which means a lower risk of landslide and pollutant emission. Furthermore, the optimum concentration of aluminum sulfate is determined to be0.02 mol/L, which is much lower than that of ammonium sulfate and magnesium sulfate. To reduce the production cost and environmental impact, we proposed a multi-stage leaching process, which was firstly leaching with ammonium sulfate and then with aluminum sulfate, following by water washing and lime neutralizing. With the ratio of ammonium sulfate to aluminum sulfate varying from 1:0 to 0.5:0.5, the residual ammonium in tailing decreases from 11.2% to 0.6%, however, the LE of RE shows an optimum value at 0.8:0.2. By neutralizing the pH of tailing with lime water to over 6, the ion concentration in water rinsing solution can meet the requirement for water discharge. At the same time, the zeta potential of clay particles is found to be around-5 mV, means a relatively lower risk of landslide. These facts indicate that the LE of IARE can be increased and the danger caused by tailings landslides and pollutant emissions can be reduced by replacing ammonium sulfate with aluminum sulfate as leaching reagent.展开更多
The fractionation of ion adsorption rare earths(IAREs) along the depth in a shaft of a deposit at Dajishan,Jiangxi, China was comparatively evaluated using the partition values(PVs) and relative fractionation values(R...The fractionation of ion adsorption rare earths(IAREs) along the depth in a shaft of a deposit at Dajishan,Jiangxi, China was comparatively evaluated using the partition values(PVs) and relative fractionation values(RFVs) of the leached rare earths(REs). It is found that both PVs and RFVs can objectively reflect the migration and fractionation of REs, but RE content and abrasion pH could not. However, the RFVs can provide more information to quantitatively evaluating the migration and fractionation characteristics of REs along the selected direction and region than PVs could, which is of significance for designing the optimal procedures of in-situ leaching based on the determined flow direction of injecting solution. It is demonstrated that the migration of Ce, Pr, and Nd along the depth direction is inert, and that of REs post Sm and Y is active. Meanwhile, the migration of La shows region characteristics which is active in the upper and inert in lower region. More interesting, the dependence of RFVs on atomic number of REs displays a tetrad group variation trend. However, the fractionation of REs among clay minerals with different particle sizes is not evident, especially for the clay in the bottom region. These results indicate that the migration and fractionation of REs not only are dominated by the adsorption of their hydrated ions, but also rely on their hydrolysis tendency, which provide information for understanding the metallogenic mechanism of IAREs.展开更多
Nanoporous Gd2O3 powders(NGPs) with different specific surface areas were prepared by a nonaqueous sol-gel method and utilized to tune the exothermal decomposition of ammonium perchlorate(AP) for enhanced propellant e...Nanoporous Gd2O3 powders(NGPs) with different specific surface areas were prepared by a nonaqueous sol-gel method and utilized to tune the exothermal decomposition of ammonium perchlorate(AP) for enhanced propellant efficiency and improved safety.It is found that with the increasing dosage of NGPs into AP,the two exothermal peaks of AP merge into one intense exothermal peak,indicating that an "energy stacking" has been achieved.Meanwhile,the unique delay of the first exothermal peak of AP is conducive to the safety of AP in application process.Furthermore,the dependence of decomposition heat of AP on dosage and calcination temperature is more evident than on the surface areas of NGPs,suggesting that the promotion effect of NGPs on the thermal decomposition of AP does not only rely on the surface interaction.Therefore,an electron transfer mechanism is proposed to illustrate the decomposition process of AP tuned by NGPs.展开更多
文摘Rare earth elements are indispensable raw materials for advanced aero-engines, special optical materials, and high-performance electronic products. With the development of the social economy, the global demand for rare earth resources is increasing, and rare earths have become a key metal for the development of new industries and frontier technologies that are highly valued both at home and abroad. Ion-adsorbed rare earth ores are an important source of rare earths, so the efficient green leaching of ion-adsorbed rare earths is important. Researchers found that the selection of an efficient green leaching agent for ion-adsorbed rare earths is based on the zeta potential of tailing clay minerals in addition to leaching efficiency, and both zeta potential and leaching ion concentration are related to mineral acidity and alkalinity, and the pH of tailing water suspension is a direct indicator of environmental water quality requirements. Therefore, the efficiency of the leaching process is closely integrated with the environmental evaluation, and the characteristics and correlation of the changes in zeta potential, pH, conductivity and pollutant concentration of the pulp of clay mineral content during the leaching process of ore leaching and tailings aqueous electrolyte solution leaching are studied by evaluating the leaching system, and a set of correlation leaching efficiency and environmental impact evaluation method is established based on the results of the above analysis, which is of scientific development of ion adsorption rare earth resources. It has important theoretical significance and practical application value.
基金Project supported by the National Natural Science Foundation of China(52062034)the National Key Research and Development Program of China(2019YFC0605002)。
文摘The construction and functionalization of lanthanide-organic cages have been a research hotspot in coordination chemistry.Benefiting from the unique luminescent and magnetic properties of lanthanide ions,the potential applications of lanthanide-organic cages in biological imaging applications are promising,but only a few corresponding explorations have been reported.He rein,we introduced a series of lanthanide tetrahedral cages,(Eu_(n)Gd_(4-n)L_(4))(sol)_8(n=0,1,2,3 and 4,where L=(4,4',4"-tris(4,4,4-trifluoro-1,3-dioxobutyl)-triphenylamine,and sol=dimethyl sulfoxide and methanol),with potential applications in biological imaging.Given the good luminescent and magnetic properties of Eu^(3+) and Gd^(3+) ions,Eu_(4)L_(4) and Gd_(4)L_(4) complexes show a high luminescence quantum yield of 29% in DMSO and large longitudinal relaxivity(r_(1)) of 11.4(mmol/L)^(-1)/s at 0.5 T in water containing 1 vol% DMSO,respectively.The heterobimetallic Eu-Gd complexes achieve a dual imaging mode by combining luminescent and magnetic centers in one cage.When the Gd:Eu ratio increases from 1:3 to 3:1,the r_(1) values increases from 5.33 to 8.64(mmoI/L)^(-1)/s,higher than that of commercial contrast agent Gd-DOTA(3.23(mmol/L)^(-1)/s).Owing to their low toxicity and good cell imaging ability toward ECA 109 cells,the selfassembled Eu-Gd heterobimetallic tetrahedral cages could be potential candidates for the multimodal imaging contrast agent.
基金supported by the National Natural Science Foundation of China(51864033,21161014,51274123)the National Key Basic Research Development Program of China(2012CBA01204)
文摘The leaching efficiency(LE) of ion adsorption rare earth(IARE) by the sulfate and chloride of ammonium,magnesium and aluminum were comparatively determined using column leaching method. It is found that at equal equivalent concentration of cation, the LE of IARE by aluminum sulfate is the highest, and the zeta potential of clay mineral particles in the tailing is near to zero, which means a lower risk of landslide and pollutant emission. Furthermore, the optimum concentration of aluminum sulfate is determined to be0.02 mol/L, which is much lower than that of ammonium sulfate and magnesium sulfate. To reduce the production cost and environmental impact, we proposed a multi-stage leaching process, which was firstly leaching with ammonium sulfate and then with aluminum sulfate, following by water washing and lime neutralizing. With the ratio of ammonium sulfate to aluminum sulfate varying from 1:0 to 0.5:0.5, the residual ammonium in tailing decreases from 11.2% to 0.6%, however, the LE of RE shows an optimum value at 0.8:0.2. By neutralizing the pH of tailing with lime water to over 6, the ion concentration in water rinsing solution can meet the requirement for water discharge. At the same time, the zeta potential of clay particles is found to be around-5 mV, means a relatively lower risk of landslide. These facts indicate that the LE of IARE can be increased and the danger caused by tailings landslides and pollutant emissions can be reduced by replacing ammonium sulfate with aluminum sulfate as leaching reagent.
基金Project supported by National Natural Science Foundation of China(21161014,51274123)National Program on Key Basic Research Project of China(973 Program,2012VBA01204)
文摘The fractionation of ion adsorption rare earths(IAREs) along the depth in a shaft of a deposit at Dajishan,Jiangxi, China was comparatively evaluated using the partition values(PVs) and relative fractionation values(RFVs) of the leached rare earths(REs). It is found that both PVs and RFVs can objectively reflect the migration and fractionation of REs, but RE content and abrasion pH could not. However, the RFVs can provide more information to quantitatively evaluating the migration and fractionation characteristics of REs along the selected direction and region than PVs could, which is of significance for designing the optimal procedures of in-situ leaching based on the determined flow direction of injecting solution. It is demonstrated that the migration of Ce, Pr, and Nd along the depth direction is inert, and that of REs post Sm and Y is active. Meanwhile, the migration of La shows region characteristics which is active in the upper and inert in lower region. More interesting, the dependence of RFVs on atomic number of REs displays a tetrad group variation trend. However, the fractionation of REs among clay minerals with different particle sizes is not evident, especially for the clay in the bottom region. These results indicate that the migration and fractionation of REs not only are dominated by the adsorption of their hydrated ions, but also rely on their hydrolysis tendency, which provide information for understanding the metallogenic mechanism of IAREs.
基金Project supported by the National Natural Science Foundation of China(51864033,51274123,21761020)the National Key Basic Research Program of China(973 Program,2012CBA01204)Jiangxi Provincial Scientific&Technological Support Project of China(20132BBE500041)
文摘Nanoporous Gd2O3 powders(NGPs) with different specific surface areas were prepared by a nonaqueous sol-gel method and utilized to tune the exothermal decomposition of ammonium perchlorate(AP) for enhanced propellant efficiency and improved safety.It is found that with the increasing dosage of NGPs into AP,the two exothermal peaks of AP merge into one intense exothermal peak,indicating that an "energy stacking" has been achieved.Meanwhile,the unique delay of the first exothermal peak of AP is conducive to the safety of AP in application process.Furthermore,the dependence of decomposition heat of AP on dosage and calcination temperature is more evident than on the surface areas of NGPs,suggesting that the promotion effect of NGPs on the thermal decomposition of AP does not only rely on the surface interaction.Therefore,an electron transfer mechanism is proposed to illustrate the decomposition process of AP tuned by NGPs.
