The increasing consumption of plastics inevitably results in increasing amounts of waste plastics. Because of their long degradation periods, these wastes negatively affect the natural environment. Numerous studies ha...The increasing consumption of plastics inevitably results in increasing amounts of waste plastics. Because of their long degradation periods, these wastes negatively affect the natural environment. Numerous studies have been conducted to recycle and eliminate waste plastics. The potential for recycling waste plastics in the iron and steel industry has been underestimated; the high C and H contents of plastics may make them suitable as alternative reductants in the reduction process of iron ore. This study aims to substitute plastic wastes for coal in reduction melting process and to investigate their performance during reduction at high temperature. We used a common type of waste plastic, polyethylene terephthalate （PET）, because of its high carbon and hydrogen contents. Composite pellets containing PET wastes, coke, and magnetite iron ore were reduced at selected temperatures of 1400 and 1450℃ for reduction time from 2 to 10 min to investigate the reduction melting behavior of these pellets. The results showed that an increased temperature and reduction time increased the reduction ratio of the pellets. The optimum experimental conditions for obtaining metallic iron （iron nuggets） were reduction at 1450℃ for 10 min using composite pellets containing 60% PET and 40% coke.展开更多
Hydrogen peroxide bleaching has been extensivelyused in high-yield pulp bleaching. Unfortunately,hydrogen peroxide can be decomposed underalkaline condition, especially when transition metalions exit. Experiments show...Hydrogen peroxide bleaching has been extensivelyused in high-yield pulp bleaching. Unfortunately,hydrogen peroxide can be decomposed underalkaline condition, especially when transition metalions exit. Experiments show that the valence oftransition metal ion is also responsible for thedecomposition of hydrogen peroxide.Iron ions are present in two oxidation states, Fe2+ andFe3+. They are both catalytically active to hydrogenperoxide decomposition. Because Fe3+ is brown, itcan affect the brightness of pulp directly, it can alsocombine with phenol, forming complexes which notonly are stable structures and are difficult to beremoved from pulp, but also significantly affect thebrightness of pulp because of their color.Sodium silicate and magnesium sulfate, when usedtogether, can greatly decrease hydrogen peroxidedecomposition. The optimum dosage of sodiumsilicate is about 0.1% (on solution) for Fe2~ and0.25% (on solution) for Fe3~. Adding chelants such asDTPA or EDTA with stabilizers simultaneously canobviously improve pulp brightness. For iron ions, thechelate effect of DTPA is better than that of EDTA.Under acidic conditions, sodium hyposulfite andcellulose can reduce Fe3+ to Fez+ effectively, and pulpbrightness is improved greatly. Adding sodiumthiosulfate simultaneously with magnesium sulfate,sodium silicate, and DTPA to alkaline peroxidesolution can result in higher brightness of pulp.pH is a key parameter during hydrogen peroxidebleaching, the optimum pH value should be 10.5-12.展开更多
Recent progress of the preparation and applications of superparamagnetic iron oxide（SPIO） clusters as magnetic resonance imaging（MRI） probes is reviewed with regard to their applications in labeling and tracking c...Recent progress of the preparation and applications of superparamagnetic iron oxide（SPIO） clusters as magnetic resonance imaging（MRI） probes is reviewed with regard to their applications in labeling and tracking cells in vivo, in diagnosis of cardiovascular diseases and tumors, and in drug delivery systems. Magnetic nanoparticles（NPs）, especially SPIO nanoparticles, have long been used as MRI contrast agents and as an advantageous nanoplatform for drug delivery,taking advantage of their unique magnetic properties and ability to function at the molecular and cellular levels. Due to advances in nanotechnology, various means to control SPIO NPs＇ size, composition, magnetization and relaxivity have been developed, as well as ways to usefully modify their surface. Recently, self-assembly of SPIO NP clusters in particulate carriers — such as polymeric micelles, vesicles, liposomes, and layer-by-layer（Lb L） capsules — have been widely studied for application as ultrasensitive MRI probes, owing to their remarkably high spin–spin（T2） relaxivity and convenience for further functionalization.展开更多
基金financially supported by Yildiz Technical University Scientific Research Projects Coordination Department (No. 2011-07-02-KAP02)
文摘The increasing consumption of plastics inevitably results in increasing amounts of waste plastics. Because of their long degradation periods, these wastes negatively affect the natural environment. Numerous studies have been conducted to recycle and eliminate waste plastics. The potential for recycling waste plastics in the iron and steel industry has been underestimated; the high C and H contents of plastics may make them suitable as alternative reductants in the reduction process of iron ore. This study aims to substitute plastic wastes for coal in reduction melting process and to investigate their performance during reduction at high temperature. We used a common type of waste plastic, polyethylene terephthalate （PET）, because of its high carbon and hydrogen contents. Composite pellets containing PET wastes, coke, and magnetite iron ore were reduced at selected temperatures of 1400 and 1450℃ for reduction time from 2 to 10 min to investigate the reduction melting behavior of these pellets. The results showed that an increased temperature and reduction time increased the reduction ratio of the pellets. The optimum experimental conditions for obtaining metallic iron （iron nuggets） were reduction at 1450℃ for 10 min using composite pellets containing 60% PET and 40% coke.
文摘Hydrogen peroxide bleaching has been extensivelyused in high-yield pulp bleaching. Unfortunately,hydrogen peroxide can be decomposed underalkaline condition, especially when transition metalions exit. Experiments show that the valence oftransition metal ion is also responsible for thedecomposition of hydrogen peroxide.Iron ions are present in two oxidation states, Fe2+ andFe3+. They are both catalytically active to hydrogenperoxide decomposition. Because Fe3+ is brown, itcan affect the brightness of pulp directly, it can alsocombine with phenol, forming complexes which notonly are stable structures and are difficult to beremoved from pulp, but also significantly affect thebrightness of pulp because of their color.Sodium silicate and magnesium sulfate, when usedtogether, can greatly decrease hydrogen peroxidedecomposition. The optimum dosage of sodiumsilicate is about 0.1% (on solution) for Fe2~ and0.25% (on solution) for Fe3~. Adding chelants such asDTPA or EDTA with stabilizers simultaneously canobviously improve pulp brightness. For iron ions, thechelate effect of DTPA is better than that of EDTA.Under acidic conditions, sodium hyposulfite andcellulose can reduce Fe3+ to Fez+ effectively, and pulpbrightness is improved greatly. Adding sodiumthiosulfate simultaneously with magnesium sulfate,sodium silicate, and DTPA to alkaline peroxidesolution can result in higher brightness of pulp.pH is a key parameter during hydrogen peroxidebleaching, the optimum pH value should be 10.5-12.
基金Project supported by the National Key Basic Research Program of China(Grant No.2013CB933903)the National Natural Science Foundation of China(Grant Nos.20974065+2 种基金51173117and 50830107)the Scientific Research Start-up Fund of Kunming University of Science and Technology(Grant No.KKSY201305089)
文摘Recent progress of the preparation and applications of superparamagnetic iron oxide（SPIO） clusters as magnetic resonance imaging（MRI） probes is reviewed with regard to their applications in labeling and tracking cells in vivo, in diagnosis of cardiovascular diseases and tumors, and in drug delivery systems. Magnetic nanoparticles（NPs）, especially SPIO nanoparticles, have long been used as MRI contrast agents and as an advantageous nanoplatform for drug delivery,taking advantage of their unique magnetic properties and ability to function at the molecular and cellular levels. Due to advances in nanotechnology, various means to control SPIO NPs＇ size, composition, magnetization and relaxivity have been developed, as well as ways to usefully modify their surface. Recently, self-assembly of SPIO NP clusters in particulate carriers — such as polymeric micelles, vesicles, liposomes, and layer-by-layer（Lb L） capsules — have been widely studied for application as ultrasensitive MRI probes, owing to their remarkably high spin–spin（T2） relaxivity and convenience for further functionalization.
