The selective dissolution of V and Fe from spent denitrification catalyst(SDC)with oxalic acid was investigated to minimise their environmental effects.The dissolution kinetics of different elements from SDC by using ...The selective dissolution of V and Fe from spent denitrification catalyst(SDC)with oxalic acid was investigated to minimise their environmental effects.The dissolution kinetics of different elements from SDC by using 0.1–1.5 mol L^(-1) oxalic acid concentration was studied at 60℃–90℃.V and Fe were preferentially released(65%and 81%)compared with Al,Ti and W within 5 min due to the redox reactions of oxalic acid.The dissolved fractions of Fe,V,Al,Wand Ti increased with the increase of oxalic acid concentration and reaction temperature.The dissolution kinetic experiments were analysed and controlled diffusion with n<0.5 according to the Avrami dissolve reaction model(R^(2)>0.92).The Arrhenius parameters of the Ea values of Ti,W,V,Fe and Al from SDC with oxalic acid were 30,26,20,19 and 11 kJ mol^(-1),respectively.The obtained Avrami equation of V and Fe was successfully used to predict their leaching behaviour in oxalic acid.Toxicity characteristic leaching procedure revealed that the toxicity risk of Vand Fe metals from SDC after leaching with oxalic acid decreased to below 5 mg kg^(-1) residua.Overall,the leaching residua by oxalic acid indicated its safety for the environment.展开更多
The hot working behavior especially dynamic recrystallization of low-carbon and medium-carbon vanadium microalloy steels has been studied by performing isothermally compression tests and Avrami analysis.The Avrami plo...The hot working behavior especially dynamic recrystallization of low-carbon and medium-carbon vanadium microalloy steels has been studied by performing isothermally compression tests and Avrami analysis.The Avrami plots of the two experiment steels have been constructed based on flow stress curves following a new approach (Jonas,et al.Acta Mater.,2009,57(2):2748-2756;Wu et al,Acta Metall.Sin.,2010,46(7):838-843).It is experimentally found that the carbon effect on dynamic recrystallization is opposite to each other in lower and higher strain ranges:Carbon causes a softening effect at low strain rates (0.01,0.1,and 1.0 s-1),and a hardening effect at high strain rates (10.0 and 30.0 s-1).Correspondingly,carbon promotes the dynamic recrystallization at low strain rates and retards the dynamic recrystallization at high strain rates in the experimental steels.The phenomenon is then tentatively explained based on the possible mechanisms of dynamic process at different strain rates.展开更多
考察了颗粒粒径、盐酸浓度和浸取温度3个条件对活化煤气化粗渣(简称活化渣)中铝、铁、钙离子浸取率的影响,并对浸取机理进行了研究。实验结果表明,活化渣为钙铝黄长石(2CaO·Al_2O_3·SiO_2)与三氧化二铁(Fe_2O_3)的固溶体,与...考察了颗粒粒径、盐酸浓度和浸取温度3个条件对活化煤气化粗渣(简称活化渣)中铝、铁、钙离子浸取率的影响,并对浸取机理进行了研究。实验结果表明,活化渣为钙铝黄长石(2CaO·Al_2O_3·SiO_2)与三氧化二铁(Fe_2O_3)的固溶体,与盐酸反应后颗粒粒径不断减小,钙离子较铝、铁离子优先浸出,其浸取过程符合化学反应控制的缩芯模型,相应的表观活化能为71.3 k J/mol;钙离子浸出后活化渣颗粒成为疏松多孔材料,铝、铁离子的浸取过程则符合Avrami模型,二者的浸取反应均受内扩散控制,表观活化能分别为24.7 k J/mol和22.5 k J/mol。展开更多
This work deals with isothermal and non-isothermal crystallization kinetics of electrically conductive polyvinylidene fluoride/poly(ethylene terephthalate) (PVDF/PET) based composites. It completes our previous work i...This work deals with isothermal and non-isothermal crystallization kinetics of electrically conductive polyvinylidene fluoride/poly(ethylene terephthalate) (PVDF/PET) based composites. It completes our previous work in which we related the crystallinity of these conductive PVDF/PET based composites to their through-plane resistivity [1]. Isothermal crystallization was described using the logarithmic form of the Avrami equation and it was observed that the crystallization rate of the PVDF phase inside the composite became slower compared to that of neat PVDF. In non-isothermal crystallization, the Avrami exponent of PVDF phase did not show any noticeable variation;however, that of PET phase, which contains the major part of the conductive carbon black (CB) and graphite (GR) additives, showed an evident decrease compared with neat PET. It was also observed that, at the same cooling rate, the crystallization rate of PVDF and PET phases inside the composite was slower than that of neat PVDF and PET.展开更多
基金The authors are grateful for the financial support of the National Natural Science Foundation of China(No.51574214).
文摘The selective dissolution of V and Fe from spent denitrification catalyst(SDC)with oxalic acid was investigated to minimise their environmental effects.The dissolution kinetics of different elements from SDC by using 0.1–1.5 mol L^(-1) oxalic acid concentration was studied at 60℃–90℃.V and Fe were preferentially released(65%and 81%)compared with Al,Ti and W within 5 min due to the redox reactions of oxalic acid.The dissolved fractions of Fe,V,Al,Wand Ti increased with the increase of oxalic acid concentration and reaction temperature.The dissolution kinetic experiments were analysed and controlled diffusion with n<0.5 according to the Avrami dissolve reaction model(R^(2)>0.92).The Arrhenius parameters of the Ea values of Ti,W,V,Fe and Al from SDC with oxalic acid were 30,26,20,19 and 11 kJ mol^(-1),respectively.The obtained Avrami equation of V and Fe was successfully used to predict their leaching behaviour in oxalic acid.Toxicity characteristic leaching procedure revealed that the toxicity risk of Vand Fe metals from SDC after leaching with oxalic acid decreased to below 5 mg kg^(-1) residua.Overall,the leaching residua by oxalic acid indicated its safety for the environment.
基金the National Natural Science Foundation of China (NSFC Project No.51071019)the Vanadium International Technical Committee (VANITEC) for funding this work
文摘The hot working behavior especially dynamic recrystallization of low-carbon and medium-carbon vanadium microalloy steels has been studied by performing isothermally compression tests and Avrami analysis.The Avrami plots of the two experiment steels have been constructed based on flow stress curves following a new approach (Jonas,et al.Acta Mater.,2009,57(2):2748-2756;Wu et al,Acta Metall.Sin.,2010,46(7):838-843).It is experimentally found that the carbon effect on dynamic recrystallization is opposite to each other in lower and higher strain ranges:Carbon causes a softening effect at low strain rates (0.01,0.1,and 1.0 s-1),and a hardening effect at high strain rates (10.0 and 30.0 s-1).Correspondingly,carbon promotes the dynamic recrystallization at low strain rates and retards the dynamic recrystallization at high strain rates in the experimental steels.The phenomenon is then tentatively explained based on the possible mechanisms of dynamic process at different strain rates.
基金the financial support on this research from the Talent Training Program of Yunnan Province, China (No. 202005AC160041)the Major R&D Project of Yunnan Province of China (No. 202002AB0800020102)。
文摘采用湿法冶金从废旧LiFePO_(4)正极粉末中回收有价金属锂和铁,回收产物作为原料制备磷酸铁锂。通过优化浸出工艺参数,在丙酮酸浓度为3.0 mol/L、H_(2)O_(2)体积为2 m L、固液比为0.1 g/m L、反应温度为80℃以及反应时间为20min的条件下,Li的浸出效率达到96.56%。采用XRD、XPS、FE-SEM和EDS对浸出残渣进行表征。结果表明,浸出残渣为FePO_(4),Fe/P摩尔比为0.974。将浸出液的pH值调整到12.0,并在80℃搅拌2 h后,浸出液中的Li通过原位沉淀以Li_(3)PO_(4)形式回收,其纯度为96.5%(质量分数)。丙酮酸/H_(2)O_(2)溶液浸出Li的反应动力学数据符合Avrami模型(R^(2)>0.95)。Li浸出过程的活化能较低,表明扩散限制浸出过程中的反应速率。
文摘考察了颗粒粒径、盐酸浓度和浸取温度3个条件对活化煤气化粗渣(简称活化渣)中铝、铁、钙离子浸取率的影响,并对浸取机理进行了研究。实验结果表明,活化渣为钙铝黄长石(2CaO·Al_2O_3·SiO_2)与三氧化二铁(Fe_2O_3)的固溶体,与盐酸反应后颗粒粒径不断减小,钙离子较铝、铁离子优先浸出,其浸取过程符合化学反应控制的缩芯模型,相应的表观活化能为71.3 k J/mol;钙离子浸出后活化渣颗粒成为疏松多孔材料,铝、铁离子的浸取过程则符合Avrami模型,二者的浸取反应均受内扩散控制,表观活化能分别为24.7 k J/mol和22.5 k J/mol。
文摘This work deals with isothermal and non-isothermal crystallization kinetics of electrically conductive polyvinylidene fluoride/poly(ethylene terephthalate) (PVDF/PET) based composites. It completes our previous work in which we related the crystallinity of these conductive PVDF/PET based composites to their through-plane resistivity [1]. Isothermal crystallization was described using the logarithmic form of the Avrami equation and it was observed that the crystallization rate of the PVDF phase inside the composite became slower compared to that of neat PVDF. In non-isothermal crystallization, the Avrami exponent of PVDF phase did not show any noticeable variation;however, that of PET phase, which contains the major part of the conductive carbon black (CB) and graphite (GR) additives, showed an evident decrease compared with neat PET. It was also observed that, at the same cooling rate, the crystallization rate of PVDF and PET phases inside the composite was slower than that of neat PVDF and PET.
