A novel low-temperature alkaline smelting process is proposed to convert and separate amphoteric metals in crushed metal enrichment originated from waste printed circuit boards. The central composite design was used t...A novel low-temperature alkaline smelting process is proposed to convert and separate amphoteric metals in crushed metal enrichment originated from waste printed circuit boards. The central composite design was used to optimize the operating parameters,in which mass ratio of Na OH-to-CME, smelting temperature and smelting time were chosen as the variables, and the conversions of amphoteric metals tin, lead, aluminum and zinc were response parameters. Second-order polynomial models of high significance and3 D response surface plots were constructed to show the relationship between the responses and the variables. Optimum area of80%-85% Pb conversion and over 95% Sn conversion was obtained by the overlaid contours at mass ratio of Na OH-to-CME of4.5-5.0, smelting temperature of 653-723 K, smelting time of 90-120 min. The models were validated experimentally in the optimum area, and the results demonstrate that these models are reliable and accurate in predicting the smelting process.展开更多
The recycling of waste printed circuit board(WPCBs) is of great significance for saving resources and protecting the environment. In this study, the WPCBs were pyrolyzed by microwave and the contained valuable metals ...The recycling of waste printed circuit board(WPCBs) is of great significance for saving resources and protecting the environment. In this study, the WPCBs were pyrolyzed by microwave and the contained valuable metals Cu, Sn and Pb were recovered from the pyrolyzed WPCBs. The effect of pyrolysis temperature and time on the recovery efficiency of valuable metals was investigated. Additionally, the characterization for morphology and surface elemental distribution of pyrolysis residues was carried out to investigate the pyrolysis mechanism. The plastic fiber boards turned into black carbides, and they can be easily separated from the metals by manual. The results indicate that 91.2%, 96.1% and 94.4% of Cu, Sn and Pb can be recovered after microwave pyrolysis at 700 °C for 60 minutes. After pyrolysis, about 79.8%(mass)solid products, 11.9%(mass) oil and 8.3%(mass) gas were produced. These gas and oil can be used as fuel and raw materials of organic chemicals, respectively. This process provides an efficient and energy-saving technology for recovering valuable metals from WPCBs.展开更多
The effective recycling of waste printed circuit boards(WPCBs)can conserve resources and reduce environmental pollution.This study explores the pyrolysis and combustion characteristics of WPCBs in various atmospheres ...The effective recycling of waste printed circuit boards(WPCBs)can conserve resources and reduce environmental pollution.This study explores the pyrolysis and combustion characteristics of WPCBs in various atmospheres through thermogravimetric and Gaussian fitting analyses.Furthermore,this study analyses the pyrolysis products and combustion processes of WPCBs through thermogravimetric and Fourier transform infrared analyses(TG-FTIR)and thermogravimetry-mass spectrometry(TG-MS).Results show that the pyrolysis and combustion processes of WPCBs do not constitute a single reaction,but rather an overlap of multiple reactions.The pyrolysis and combustion process of WPCBs is divided into multiple reactions by Gaussian peak fitting.The kinetic parameters of each reaction are obtained by the Coats-Redfern method.In an argon atmosphere,pyrolysis consists of the overlap of the preliminary pyrolysis of epoxy resin,pyrolysis of small organic molecules,and pyrolysis of brominated flame retardants.The thermal decomposition process in the O_(2) atmosphere is mainly divided into two reactions:brominated flame retardant combustion and epoxy combustion.This study provided the theoretical basis for pollution control,process optimization,and reactor design of WPCBs pyrolysis.展开更多
Waste printed circuit boards(WPCBs)are generated increasingly recent years with the rapid replacement of electric and electronic products.Pyrolysis is considered to be a potential environmentally-friendly technology f...Waste printed circuit boards(WPCBs)are generated increasingly recent years with the rapid replacement of electric and electronic products.Pyrolysis is considered to be a potential environmentally-friendly technology for recovering organic and metal resources from WPCBs.Thermogravimetric analysis and kinetic analysis of WPCBs were carried out in this study.It showed that the co-existing metals(Cu,Fe,Ni)in WPCBs have positive self-catalytic influence during the pyrolysis process.To illustrate their catalytic effects,the apparent activation energy was calculated by differential model.Contributions of different reactions during catalytic pyrolysis process was studied and the mechanism function was obtained byŠesták-Berggren model.The results showed that Cu,Fe,Ni can promote the reaction progress and reduce the apparent activation energy.Among the three metals,Ni plays better catalytic role than Cu,then Fe.This work provides theoretical base for understanding the three metals’catalytic influence during the pyrolysis of non-metal powders in WPCBs.展开更多
The recycling method and principle of SnO2 from the tin slag of printed circuit boards(PCB) waste were investigated. In this study, pure SnO2 powders were obtained through a multi-step process including ball-milling...The recycling method and principle of SnO2 from the tin slag of printed circuit boards(PCB) waste were investigated. In this study, pure SnO2 powders were obtained through a multi-step process including ball-milling, roasting, dissolving, precipitating, and pickling. The total recovery rate of tin can be up to 91 %. The SnO2 powders obtained is the single phase, and the content of SnO2 is up to 99.9 %. However, the SnO2 particles are easier to agglomerate during the precipitation process. The agglomerate SnO2 particles are about 7.778 lm in mean particle size(D50). This preparation method presents a viable alternative for the tin slag recycling. The tin is not only recycled, but also reused directly to prepare pure SnO2 powders.展开更多
Copper recovery is the core of waste printed circuit boards (WPCBs) treatment. In this study, we proposed a feasible and efficient way to recover copper from WPCBs concentrated metal scraps by direct electrolysis an...Copper recovery is the core of waste printed circuit boards (WPCBs) treatment. In this study, we proposed a feasible and efficient way to recover copper from WPCBs concentrated metal scraps by direct electrolysis and thctors that affect copper recovery rate and purity, mainly CuSO4.5H2O concentration, NaCI concentration, H2SO4 concentration and current density, were discussed in detail. The results indicated that copper recovery rate increased first with the increase ofCuSO4- 5H2O, NaCI, H2SO4 and current density and then decreased with further increasing these conditions. NaCI, H2SO4 and current density also showed a similar impact on copper purity, which also increased first and then decreased. Copper purity increased with the increase of CuSO4.5H2O. When the concentration of CuSO4-5H2O NaCI and H2oSO4 was respectively 90, 40 and 118 g/L and current density was 80 mA/cm-, copper recovery rate and purity was up to 97.32% and 99.86%, respectively. Thus, electrolysis proposes a feasible and prospective approach for waste printed circuit boards recycle, even for e-waste, though more researches are needed for industrial application.展开更多
The method for the recycling of copper from copper chloride solution was developed. This process consists of extraction of copper, purification and particle size reduction. In the first step, reductive metal scraps we...The method for the recycling of copper from copper chloride solution was developed. This process consists of extraction of copper, purification and particle size reduction. In the first step, reductive metal scraps were added to acidic copper chloride waste enchants produced in the PCB industry to obtain copper powder. Composition analysis showed that this powder contained impurities such as Fe, Ni, and water. So, drying and purification were carried out by using microwave and a centrifugal separator. Thereby the copper powder had a purity of higher than 99% and spherical form in morphology. The copper powder size was decreased by ball milling.展开更多
基金Projects(51074190,51234009)supported by the National Natural Science Foundation of ChinaProject(2014DFA90520)supported by International Cooperation Program of Ministry of Science of ChinaProject(20110162110049)supported by the Doctoral Scientific Fund Project of the Ministry of Education of China
文摘A novel low-temperature alkaline smelting process is proposed to convert and separate amphoteric metals in crushed metal enrichment originated from waste printed circuit boards. The central composite design was used to optimize the operating parameters,in which mass ratio of Na OH-to-CME, smelting temperature and smelting time were chosen as the variables, and the conversions of amphoteric metals tin, lead, aluminum and zinc were response parameters. Second-order polynomial models of high significance and3 D response surface plots were constructed to show the relationship between the responses and the variables. Optimum area of80%-85% Pb conversion and over 95% Sn conversion was obtained by the overlaid contours at mass ratio of Na OH-to-CME of4.5-5.0, smelting temperature of 653-723 K, smelting time of 90-120 min. The models were validated experimentally in the optimum area, and the results demonstrate that these models are reliable and accurate in predicting the smelting process.
基金supported by the National Key Research and Development Program of China (2019YFC1908404)the National Natural Science Foundation of China (Nos. 51834008, 51874040,52034002)+1 种基金the Guangxi Innovation-Driven Development Project(AA18242042-1)the Fundamental Research Funds for the Central Universities (FRF-TP-18-020A3)。
文摘The recycling of waste printed circuit board(WPCBs) is of great significance for saving resources and protecting the environment. In this study, the WPCBs were pyrolyzed by microwave and the contained valuable metals Cu, Sn and Pb were recovered from the pyrolyzed WPCBs. The effect of pyrolysis temperature and time on the recovery efficiency of valuable metals was investigated. Additionally, the characterization for morphology and surface elemental distribution of pyrolysis residues was carried out to investigate the pyrolysis mechanism. The plastic fiber boards turned into black carbides, and they can be easily separated from the metals by manual. The results indicate that 91.2%, 96.1% and 94.4% of Cu, Sn and Pb can be recovered after microwave pyrolysis at 700 °C for 60 minutes. After pyrolysis, about 79.8%(mass)solid products, 11.9%(mass) oil and 8.3%(mass) gas were produced. These gas and oil can be used as fuel and raw materials of organic chemicals, respectively. This process provides an efficient and energy-saving technology for recovering valuable metals from WPCBs.
基金financially supported by the National Key R&D Program of China(Nos.2019YFC1908400 and 2019YFC1907405)the National Natural Science Foundation of China(Nos.51904124,51804139,52004111 and 52074136)+2 种基金the Jiangxi Provincial Cultivation Program for Academic and Technical Leaders of Major Subjects(Nos.20212BCJL23052 and 20212BCJ23007)the Distinguished Professor Program of Jinggang Scholars,China Institutions of Higher Learning Jiangxi Province,the Science and Technology Research Project of the Jiangxi Provincial Department of Education(No.gjj170507)the Science Research Foundation of Jiangxi University of Science and Technology(No.jxxjbs 17046)。
文摘The effective recycling of waste printed circuit boards(WPCBs)can conserve resources and reduce environmental pollution.This study explores the pyrolysis and combustion characteristics of WPCBs in various atmospheres through thermogravimetric and Gaussian fitting analyses.Furthermore,this study analyses the pyrolysis products and combustion processes of WPCBs through thermogravimetric and Fourier transform infrared analyses(TG-FTIR)and thermogravimetry-mass spectrometry(TG-MS).Results show that the pyrolysis and combustion processes of WPCBs do not constitute a single reaction,but rather an overlap of multiple reactions.The pyrolysis and combustion process of WPCBs is divided into multiple reactions by Gaussian peak fitting.The kinetic parameters of each reaction are obtained by the Coats-Redfern method.In an argon atmosphere,pyrolysis consists of the overlap of the preliminary pyrolysis of epoxy resin,pyrolysis of small organic molecules,and pyrolysis of brominated flame retardants.The thermal decomposition process in the O_(2) atmosphere is mainly divided into two reactions:brominated flame retardant combustion and epoxy combustion.This study provided the theoretical basis for pollution control,process optimization,and reactor design of WPCBs pyrolysis.
基金supported by the National Natural Science Foundation of China(Nos.U20A20273 and 21677050)。
文摘Waste printed circuit boards(WPCBs)are generated increasingly recent years with the rapid replacement of electric and electronic products.Pyrolysis is considered to be a potential environmentally-friendly technology for recovering organic and metal resources from WPCBs.Thermogravimetric analysis and kinetic analysis of WPCBs were carried out in this study.It showed that the co-existing metals(Cu,Fe,Ni)in WPCBs have positive self-catalytic influence during the pyrolysis process.To illustrate their catalytic effects,the apparent activation energy was calculated by differential model.Contributions of different reactions during catalytic pyrolysis process was studied and the mechanism function was obtained byŠesták-Berggren model.The results showed that Cu,Fe,Ni can promote the reaction progress and reduce the apparent activation energy.Among the three metals,Ni plays better catalytic role than Cu,then Fe.This work provides theoretical base for understanding the three metals’catalytic influence during the pyrolysis of non-metal powders in WPCBs.
基金financially supported by the Beijing Nova Program (No. Z141103001814006)the National Key Technology R&D Program (Nos. 2012BAC12B05 and 2012BAC02B01)+1 种基金the National Natural Science Foundation of China (Nos. 51174247 and U1360202)the National High-Tech Research and the Development Program of China (No. 2012AA063202)
文摘The recycling method and principle of SnO2 from the tin slag of printed circuit boards(PCB) waste were investigated. In this study, pure SnO2 powders were obtained through a multi-step process including ball-milling, roasting, dissolving, precipitating, and pickling. The total recovery rate of tin can be up to 91 %. The SnO2 powders obtained is the single phase, and the content of SnO2 is up to 99.9 %. However, the SnO2 particles are easier to agglomerate during the precipitation process. The agglomerate SnO2 particles are about 7.778 lm in mean particle size(D50). This preparation method presents a viable alternative for the tin slag recycling. The tin is not only recycled, but also reused directly to prepare pure SnO2 powders.
文摘Copper recovery is the core of waste printed circuit boards (WPCBs) treatment. In this study, we proposed a feasible and efficient way to recover copper from WPCBs concentrated metal scraps by direct electrolysis and thctors that affect copper recovery rate and purity, mainly CuSO4.5H2O concentration, NaCI concentration, H2SO4 concentration and current density, were discussed in detail. The results indicated that copper recovery rate increased first with the increase ofCuSO4- 5H2O, NaCI, H2SO4 and current density and then decreased with further increasing these conditions. NaCI, H2SO4 and current density also showed a similar impact on copper purity, which also increased first and then decreased. Copper purity increased with the increase of CuSO4.5H2O. When the concentration of CuSO4-5H2O NaCI and H2oSO4 was respectively 90, 40 and 118 g/L and current density was 80 mA/cm-, copper recovery rate and purity was up to 97.32% and 99.86%, respectively. Thus, electrolysis proposes a feasible and prospective approach for waste printed circuit boards recycle, even for e-waste, though more researches are needed for industrial application.
文摘The method for the recycling of copper from copper chloride solution was developed. This process consists of extraction of copper, purification and particle size reduction. In the first step, reductive metal scraps were added to acidic copper chloride waste enchants produced in the PCB industry to obtain copper powder. Composition analysis showed that this powder contained impurities such as Fe, Ni, and water. So, drying and purification were carried out by using microwave and a centrifugal separator. Thereby the copper powder had a purity of higher than 99% and spherical form in morphology. The copper powder size was decreased by ball milling.