Organic depressants have low selectivity in separating molybdenite and talc because their metal sites lack activity for organics chemisorption.In this study,surface modification by copper sulfate was used to induce th...Organic depressants have low selectivity in separating molybdenite and talc because their metal sites lack activity for organics chemisorption.In this study,surface modification by copper sulfate was used to induce the differential adsorption of pectin onto molybdenite and talc surfaces for enhanced flotation separation.Contact-angle experiments,scanning electron microscopy,adsorption measurements,timeof-flight secondary-ion mass spectrometry,and X-ray photoelectron spectroscopy analyses were conducted to reveal the interaction mechanism.Results illustrated that molybdenite and talc could not be separated using pectin alone,while molybdenite was selectively depressed after surface modification by copper sulfate and this effect was strengthened under alkaline conditions.Metal sites(Mg,Si and Mo)of talc and molybdenite themselves were unable to react with pectin,whereas Cu+would deposit and further function as active site for pectin chemisorption after surface modification.However,the quantity of deposited Cu sites dropped on talc surface and increased on molybdenite surface with increased pH,and the Mo atoms of molybdenite crystal were activated to take part in pectin chemisorption.Therefore,more pectin was adhered on molybdenite surface,which imparted molybdenite stronger wettability.Herein,surface-modification through metal ions can enable the differential adsorption of organic depressants and enhance the flotation separation of minerals.展开更多
Firstly,the relationship between the accuracy of low altitude aerial photogrammetry and the field angle of camera is made by a quantitative analysis from the theory.The conclusion that the low altitude photogrammetry ...Firstly,the relationship between the accuracy of low altitude aerial photogrammetry and the field angle of camera is made by a quantitative analysis from the theory.The conclusion that the low altitude photogrammetry should use wide-angle camera as much as possible is done.Then,the limitation of the single lens camera to expand field angle and the combined wide-angle camera existing on the market not suitable for light load of low altitude UAV(Unmanned Aerial Vehicle)due to excessive weight are pointed out.The characteristics of combined wide-angle low altitude light camera with self-calibration and self-stabilization developed by the author are described,especially the principle of self-calibration for the combination of static error and dynamic error.Based on the practice of large scale mapping,a technical procedure in aerial photography by taking with wide-angle camera and large overlap simultaneously for improving the accuracy of low altitude photogrammetry is proposed.The typical engineering produced data is used to verity the above theoretical analysis.A technical route for increasing accuracy of low altitude photogrammetry with combined wide-angle camera is expounded.展开更多
基金The authors would like to acknowledge the support from the National Natural Science Foundation of China(No.52174272)the Joint Funds of the National Natural Science Foundation of China(No.U1704252)+1 种基金the Fundamental Research Funds for the Central Universities of Central South University(Nos.2021zzts0306 and 2021zzts0896)the Hunan Provincial Natural Science Foundation of China(No.2020JJ5736).
文摘Organic depressants have low selectivity in separating molybdenite and talc because their metal sites lack activity for organics chemisorption.In this study,surface modification by copper sulfate was used to induce the differential adsorption of pectin onto molybdenite and talc surfaces for enhanced flotation separation.Contact-angle experiments,scanning electron microscopy,adsorption measurements,timeof-flight secondary-ion mass spectrometry,and X-ray photoelectron spectroscopy analyses were conducted to reveal the interaction mechanism.Results illustrated that molybdenite and talc could not be separated using pectin alone,while molybdenite was selectively depressed after surface modification by copper sulfate and this effect was strengthened under alkaline conditions.Metal sites(Mg,Si and Mo)of talc and molybdenite themselves were unable to react with pectin,whereas Cu+would deposit and further function as active site for pectin chemisorption after surface modification.However,the quantity of deposited Cu sites dropped on talc surface and increased on molybdenite surface with increased pH,and the Mo atoms of molybdenite crystal were activated to take part in pectin chemisorption.Therefore,more pectin was adhered on molybdenite surface,which imparted molybdenite stronger wettability.Herein,surface-modification through metal ions can enable the differential adsorption of organic depressants and enhance the flotation separation of minerals.
文摘Firstly,the relationship between the accuracy of low altitude aerial photogrammetry and the field angle of camera is made by a quantitative analysis from the theory.The conclusion that the low altitude photogrammetry should use wide-angle camera as much as possible is done.Then,the limitation of the single lens camera to expand field angle and the combined wide-angle camera existing on the market not suitable for light load of low altitude UAV(Unmanned Aerial Vehicle)due to excessive weight are pointed out.The characteristics of combined wide-angle low altitude light camera with self-calibration and self-stabilization developed by the author are described,especially the principle of self-calibration for the combination of static error and dynamic error.Based on the practice of large scale mapping,a technical procedure in aerial photography by taking with wide-angle camera and large overlap simultaneously for improving the accuracy of low altitude photogrammetry is proposed.The typical engineering produced data is used to verity the above theoretical analysis.A technical route for increasing accuracy of low altitude photogrammetry with combined wide-angle camera is expounded.
