In this study,a roasting enhanced flotation process was proposed to recover LiMn_(2)O_(4) and grapite from waste lithium-ion batteries(LIBs).The effects of roasting temperature and time on the surface modification was...In this study,a roasting enhanced flotation process was proposed to recover LiMn_(2)O_(4) and grapite from waste lithium-ion batteries(LIBs).The effects of roasting temperature and time on the surface modification was investigated,and a series of analytical technologies were used to reveal process mechanism.The results indicate that LiMn_(2)O_(4) can be effectively separated from graphite via flotation after the roasting.The flotation grade of LiMn_(2)O_(4) was significantly increased from 63.10%to 91.36%after roasting at 550℃for 2 h.The TG-DTG analysis demonstrates that the difficulty in flotation separation of LiMn_(2)O_(4) from graphite is caused by the organic binder and electrolytes coating on their surfaces.The XRD,SEM,XPS,and contact angle analyses confirm that the organic films on the surfaces of those materials can be effectively removed by roasting,after which the wettability of LiMn_(2)O_(4) is regained and thus the surface wettability difference between the cathode and anode materials is increased significantly.The closed-circuit flotation test indicates that a LiMn_(2)O_(4) sample with high grade of 99.81%is obtained,while the recovery of LiMn_(2)O_(4) is as high as 99.40%.This study provides an economical and eco-friendly way to recycling waste LIBs.展开更多
Mn and Li were selectively extracted from the manganese-rich slag by sulfation roasting−water leaching.The extraction mechanisms of Mn and Li were investigated by means of XRD,TG−DSC,and SEM−EDS.73.71%Mn and 73.28%Li ...Mn and Li were selectively extracted from the manganese-rich slag by sulfation roasting−water leaching.The extraction mechanisms of Mn and Li were investigated by means of XRD,TG−DSC,and SEM−EDS.73.71%Mn and 73.28%Li were leached under optimal experimental conditions:acid concentration of 82 wt.%,acid-to-slag mass ratio of 1.5:1,roasting temperature of 800°C,and roasting time of 2 h.During the roasting process,the manganese-rich slag first reacted with concentrated sulfuric acid,producing MnSO_(4),MnSO_(4)·H_(2)O,Li_(2)Mg(SO_(4))_(2),Al_(2)(SO_(4))_(3),and H_(4)SiO_(4).With the roasting temperature increasing,H_(4)SiO_(4) and Al_(2)(SO_(4))_(3) decomposed successively,resulting in generation of mullite and spinel.The mullite formation aided in decreasing the leaching efficiencies of Al and Si,while increasing the Li leaching efficiency.The formation of spinel,however,decreased the leaching efficiencies of Mn and Li.展开更多
Active and passive behaviors of pure gold（Au） and roasted gold ore（RGO） electrodes were investigated at 25 °C in de-aerated agitated cyanide media.Cyclic voltammetry and potentiodynamic polarization with agit...Active and passive behaviors of pure gold（Au） and roasted gold ore（RGO） electrodes were investigated at 25 °C in de-aerated agitated cyanide media.Cyclic voltammetry and potentiodynamic polarization with agitation at 100 r/min in 0.04 mol/L NaCN solution showed different peak positions and current densities.Potentiodynamic tests illustrate that the peak current densities increase greatly with increasing the cyanide concentration.Increasing the pH value from 10 to 11 resultes in a great decrease of current density,while it increases noticeably by decreasing the agitation from 100 to 60 r/min.In the presence of oxygen,Au and RGO electrodes show different characteristics of peak positions and corrosion rates.The potentiostatic studies show that increasing the potential from 1 to 1.4 V at pH value of 11 results in an 80% decrease of current density while decreasing the pH value from 11 to 10 at 1 V gives a 1.7 fold increase of current density,possibly due to more effective passive layer.Following polarization,electrochemical noise measurements（ENM） during decay periods show that Au results in more passive states at high potentials,showing pitting corrosion.The ENM results show that this technique can be a promising tool for a better understanding of gold leaching.The XPS studies prove the presence of passive oxides.展开更多
The CO_2 absorption ability of synthetic calcium-based sorbent modified by peanut husk ash (PHA) was tested by Thermal Gravimetric Analyzer (TGA), and the effects of steam and calcination temperature were investigate...The CO_2 absorption ability of synthetic calcium-based sorbent modified by peanut husk ash (PHA) was tested by Thermal Gravimetric Analyzer (TGA), and the effects of steam and calcination temperature were investigated. The PHA composition was analyzed by X-Ray Fluorescence (XRF), the apparent morphology was characterized by scanning electron microscope (SEM), and the phases of the sorbent before and after calcination were examined by X-ray diffraction (XRD). The addition of PHA effectively improved the cyclic stability of the calcium-based sorbent. The optimal molar ratio of SiO_2 in PHA to CaO was around 0.07. Steam had positive effect on keeping porosity of the sorbent at the chemical reaction stage, and improved its CO_2 absorption ability. Steam also reduced the diffusion resistance of the product layer, and depressed the influence of high temperature calcination. It was also found that the steam hydration after calcination was an effective way to recover the absorption ability of the sorbent, while the hydration duration of 10 min was enough.展开更多
基金Project(2021JJ20062) supported by the Natural Science Foundation of Hunan Province,ChinaProject(2019XK2304) supported by Landmark Innovation Demonstration Project of Hunan Province,China+3 种基金Project(2022GK4058) supported by High-tech Industry Science and Technology Innovation Leading Project of Hunan Province,ChinaProject(2020CX038) supported by the Innovation Driven Project of Central South University,ChinaProject(2019YFC1907301) supported by the National Key R&D Program of ChinaProject(202006375018) supported by the China Scholarship Council。
文摘In this study,a roasting enhanced flotation process was proposed to recover LiMn_(2)O_(4) and grapite from waste lithium-ion batteries(LIBs).The effects of roasting temperature and time on the surface modification was investigated,and a series of analytical technologies were used to reveal process mechanism.The results indicate that LiMn_(2)O_(4) can be effectively separated from graphite via flotation after the roasting.The flotation grade of LiMn_(2)O_(4) was significantly increased from 63.10%to 91.36%after roasting at 550℃for 2 h.The TG-DTG analysis demonstrates that the difficulty in flotation separation of LiMn_(2)O_(4) from graphite is caused by the organic binder and electrolytes coating on their surfaces.The XRD,SEM,XPS,and contact angle analyses confirm that the organic films on the surfaces of those materials can be effectively removed by roasting,after which the wettability of LiMn_(2)O_(4) is regained and thus the surface wettability difference between the cathode and anode materials is increased significantly.The closed-circuit flotation test indicates that a LiMn_(2)O_(4) sample with high grade of 99.81%is obtained,while the recovery of LiMn_(2)O_(4) is as high as 99.40%.This study provides an economical and eco-friendly way to recycling waste LIBs.
基金supported by the National Natural Science Foundation of China (No.51704038)the State-Owned Enterprise Electric Vehicle Industry Alliance,China (No.JS-211)the Changsha Science and Technology Project,China (No.kq1602212)。
文摘Mn and Li were selectively extracted from the manganese-rich slag by sulfation roasting−water leaching.The extraction mechanisms of Mn and Li were investigated by means of XRD,TG−DSC,and SEM−EDS.73.71%Mn and 73.28%Li were leached under optimal experimental conditions:acid concentration of 82 wt.%,acid-to-slag mass ratio of 1.5:1,roasting temperature of 800°C,and roasting time of 2 h.During the roasting process,the manganese-rich slag first reacted with concentrated sulfuric acid,producing MnSO_(4),MnSO_(4)·H_(2)O,Li_(2)Mg(SO_(4))_(2),Al_(2)(SO_(4))_(3),and H_(4)SiO_(4).With the roasting temperature increasing,H_(4)SiO_(4) and Al_(2)(SO_(4))_(3) decomposed successively,resulting in generation of mullite and spinel.The mullite formation aided in decreasing the leaching efficiencies of Al and Si,while increasing the Li leaching efficiency.The formation of spinel,however,decreased the leaching efficiencies of Mn and Li.
文摘Active and passive behaviors of pure gold（Au） and roasted gold ore（RGO） electrodes were investigated at 25 °C in de-aerated agitated cyanide media.Cyclic voltammetry and potentiodynamic polarization with agitation at 100 r/min in 0.04 mol/L NaCN solution showed different peak positions and current densities.Potentiodynamic tests illustrate that the peak current densities increase greatly with increasing the cyanide concentration.Increasing the pH value from 10 to 11 resultes in a great decrease of current density,while it increases noticeably by decreasing the agitation from 100 to 60 r/min.In the presence of oxygen,Au and RGO electrodes show different characteristics of peak positions and corrosion rates.The potentiostatic studies show that increasing the potential from 1 to 1.4 V at pH value of 11 results in an 80% decrease of current density while decreasing the pH value from 11 to 10 at 1 V gives a 1.7 fold increase of current density,possibly due to more effective passive layer.Following polarization,electrochemical noise measurements（ENM） during decay periods show that Au results in more passive states at high potentials,showing pitting corrosion.The ENM results show that this technique can be a promising tool for a better understanding of gold leaching.The XPS studies prove the presence of passive oxides.
基金supported by the National Natural Science Foundation of China (Grant No. 51406198)
文摘The CO_2 absorption ability of synthetic calcium-based sorbent modified by peanut husk ash (PHA) was tested by Thermal Gravimetric Analyzer (TGA), and the effects of steam and calcination temperature were investigated. The PHA composition was analyzed by X-Ray Fluorescence (XRF), the apparent morphology was characterized by scanning electron microscope (SEM), and the phases of the sorbent before and after calcination were examined by X-ray diffraction (XRD). The addition of PHA effectively improved the cyclic stability of the calcium-based sorbent. The optimal molar ratio of SiO_2 in PHA to CaO was around 0.07. Steam had positive effect on keeping porosity of the sorbent at the chemical reaction stage, and improved its CO_2 absorption ability. Steam also reduced the diffusion resistance of the product layer, and depressed the influence of high temperature calcination. It was also found that the steam hydration after calcination was an effective way to recover the absorption ability of the sorbent, while the hydration duration of 10 min was enough.
