In this work,the reflux classifier with closely spaced inclined channels is used as the pre-concentration facility to improve the separation efficiency before the shaking table separation.Three operating parameters of...In this work,the reflux classifier with closely spaced inclined channels is used as the pre-concentration facility to improve the separation efficiency before the shaking table separation.Three operating parameters of reflux classifier(RC)to pre-concentrate fine(0.023−0.15 mm)tailings of antimony oxide were optimized by response surface methodology(RSM)using a three-level Box-Behnken design(BBD).The parameters studied for the optimization were feeding speed,underflow,and ascending water speed.Second-order response functions were produced for the Sb grade and recovery rate of the concentrate.Taking advantage of the quadratic programming,when the factors of feeding,underflow and ascending water are respectively 225,30 and 133 cm^3/min,a better result can be achieved for the concentrate grade of 2.31% and recovery rate of 83.17%.At the same time,70.48% of the tailings with the grade of 0.20% were discarded out of the feeding.The results indicated that the reflux classifier has a good performance in dealing with fine tailings of antimony oxide.Moreover,second-order polynomial equations,ANOVA,and three-dimensional surface plots were developed to evaluate the effects of each parameter on Sb grade and recovery rate of the concentrate.展开更多
The main objective of this paper was to characterize the voltammetric profiles of the Pt/C,Pt/C-ATO,Pd/C and Pd/CATO electrocatalysts and study their catalytic activities for methane oxidation in an acidic electrolyte...The main objective of this paper was to characterize the voltammetric profiles of the Pt/C,Pt/C-ATO,Pd/C and Pd/CATO electrocatalysts and study their catalytic activities for methane oxidation in an acidic electrolyte at 25 ℃ and in a direct methane proton exchange membrane fuel cell at 80 ℃. The electrocatalysts prepared also were characterized by X-ray diffraction( XRD) and transmission electron microscopy( TEM). The diffractograms of the Pt/C and Pt/C-ATO electrocatalysts show four peaks associated with Pt face-centered cubic( fcc) structure,and the diffractograms of Pd/C and Pd/C-ATO show four peaks associated with Pd face-centered cubic( fcc) structure. For Pt/C-ATO and Pd/C-ATO,characteristic peaks of cassiterite( SnO_2) phase are observed,which are associated with Sb-doped SnO_2( ATO) used as supports for electrocatalysts. Cyclic voltammograms( CV) of all electrocatalysts after adsorption of methane show that there is a current increase during the anodic scan. However,this effect is more pronounced for Pt/C-ATO and Pd/C-ATO. This process is related to the oxidation of the adsorbed species through the bifunctional mechanism,where ATO provides oxygenated species for the oxidation of CO or HCO intermediates adsorbed in Pt or Pd sites. From in situ ATR-FTIR( Attenuated Total Reflectance-Fourier Transform Infrared) experiments for all electrocatalysts prepared the formation of HCO or CO intermediates are observed,which indicates the production of carbon dioxide. Polarization curves at 80 ℃in a direct methane fuel cell( DMEFC) show that Pd/C and Pt/C electroacatalysts have superior performance to Pd/C-ATO and Pt/C-ATO in methane oxidation.展开更多
基金Project(2015SK20792)supported by Key Province Key Technology Research and Development Program of the Ministry of Science and Technology of Hunan,ChinaProjects(2019zzts703,2020zzts740,2020zzts202)supported by the Fundamental Research Funds for the Central Universities of ChinaProject(2020P4FZG03A)supported by State Key Laboratory of Vanadium and Titanium Resources Comprehensive Utilization,China。
文摘In this work,the reflux classifier with closely spaced inclined channels is used as the pre-concentration facility to improve the separation efficiency before the shaking table separation.Three operating parameters of reflux classifier(RC)to pre-concentrate fine(0.023−0.15 mm)tailings of antimony oxide were optimized by response surface methodology(RSM)using a three-level Box-Behnken design(BBD).The parameters studied for the optimization were feeding speed,underflow,and ascending water speed.Second-order response functions were produced for the Sb grade and recovery rate of the concentrate.Taking advantage of the quadratic programming,when the factors of feeding,underflow and ascending water are respectively 225,30 and 133 cm^3/min,a better result can be achieved for the concentrate grade of 2.31% and recovery rate of 83.17%.At the same time,70.48% of the tailings with the grade of 0.20% were discarded out of the feeding.The results indicated that the reflux classifier has a good performance in dealing with fine tailings of antimony oxide.Moreover,second-order polynomial equations,ANOVA,and three-dimensional surface plots were developed to evaluate the effects of each parameter on Sb grade and recovery rate of the concentrate.
基金The project was supported by the FAPESP(2014/09087-4,2014/50279-4).
文摘The main objective of this paper was to characterize the voltammetric profiles of the Pt/C,Pt/C-ATO,Pd/C and Pd/CATO electrocatalysts and study their catalytic activities for methane oxidation in an acidic electrolyte at 25 ℃ and in a direct methane proton exchange membrane fuel cell at 80 ℃. The electrocatalysts prepared also were characterized by X-ray diffraction( XRD) and transmission electron microscopy( TEM). The diffractograms of the Pt/C and Pt/C-ATO electrocatalysts show four peaks associated with Pt face-centered cubic( fcc) structure,and the diffractograms of Pd/C and Pd/C-ATO show four peaks associated with Pd face-centered cubic( fcc) structure. For Pt/C-ATO and Pd/C-ATO,characteristic peaks of cassiterite( SnO_2) phase are observed,which are associated with Sb-doped SnO_2( ATO) used as supports for electrocatalysts. Cyclic voltammograms( CV) of all electrocatalysts after adsorption of methane show that there is a current increase during the anodic scan. However,this effect is more pronounced for Pt/C-ATO and Pd/C-ATO. This process is related to the oxidation of the adsorbed species through the bifunctional mechanism,where ATO provides oxygenated species for the oxidation of CO or HCO intermediates adsorbed in Pt or Pd sites. From in situ ATR-FTIR( Attenuated Total Reflectance-Fourier Transform Infrared) experiments for all electrocatalysts prepared the formation of HCO or CO intermediates are observed,which indicates the production of carbon dioxide. Polarization curves at 80 ℃in a direct methane fuel cell( DMEFC) show that Pd/C and Pt/C electroacatalysts have superior performance to Pd/C-ATO and Pt/C-ATO in methane oxidation.
