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
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.
