Mercury removal from coal combustion flue gas remains a significant challenge for environmental protection due to the lack of cost-effective sorbents.In this study,a series of red mud(RM)-based sorbents impregnated wi...Mercury removal from coal combustion flue gas remains a significant challenge for environmental protection due to the lack of cost-effective sorbents.In this study,a series of red mud(RM)-based sorbents impregnated with sodium halides(NaBr and NaI)are presented to capture elemental mercury(Hg^(0))from flue gas.The modified RM underwent comprehensive characterization,including analysis of its textural qualities,crystal structure,chemical composition,and thermal properties.The results indicate that the halide impregnation substantially impacts the surface area and pore size of the RM.Hg^(0) removal performance was evaluated on a fixed-bed reactor in simulated flue gas(consisting of N_(2),O_(2),CO_(2),NO and SO_(2),etc.)on a modified RM.At an optimal adsorption temperature of 160℃,NaI-modified sorbent(RMI5)offers a removal efficiency of 98%in a mixture of gas,including O_(2),NO and HCl.Furthermore,pseudo-second-order model fitting results demonstrate the chemisorption mechanism for the adsorption of Hg^(0) in kinetic investigations.展开更多
Red mud is a solid waste discharged in the process of alumina production,and how to realize the efficient recovery of its iron is an urgent problem to be solved.In this study,the iron extraction test and mechanism stu...Red mud is a solid waste discharged in the process of alumina production,and how to realize the efficient recovery of its iron is an urgent problem to be solved.In this study,the iron extraction test and mechanism study of high iron red mud were carried out under the coupling conditions of multiple physical field(microwave field,gas-solid flow field and temperature field)with biomass as the reducing agent.The test results showed that under the optimal conditions,an iron concentrate with a yield of 78.4%,an iron grade of 59.23%,and a recovery rate of 86.65%was obtained.The analyses of XRD,XPS,TEM,and SEM-EDS showed that during the roasting process,the hematite in the high-iron red mud was completely converted to magnetite,and the biomass produced the reductant that provided the magnetization reaction;A large number of cracks and pores appeared in the surface of the hematite reduction product particles,which helped to induce iron minerals to undergo effective mineral phase transformation.The above study provides ideas for the phase transformation and efficient recovery of iron minerals in red mud.展开更多
红层泥岩水敏性高,作路基填料时可用石灰改良。受季节变化影响,路基基床经历干湿循环,导致服役性能降低。为研究干湿循环下改良填料力学特性劣化规律,开展一系列干湿循环试验、无侧限抗压试验和弯曲元试验测定改良填料无侧限抗压强度和...红层泥岩水敏性高,作路基填料时可用石灰改良。受季节变化影响,路基基床经历干湿循环,导致服役性能降低。为研究干湿循环下改良填料力学特性劣化规律,开展一系列干湿循环试验、无侧限抗压试验和弯曲元试验测定改良填料无侧限抗压强度和小应变刚度。结合连续滴水扫描电镜(scanning electron microscope,简称SEM)试验,揭示干湿循环后填料微观结构劣化特征。结果表明:低幅度循环下试样在干侧和湿侧均产生体胀。高幅度循环下试样在湿侧产生体胀。在干侧先产生体缩,随循环次数增加,即使含水率较低,试样也产生体胀。体胀导致强度和小应变刚度均有不同程度的劣化。当试样产生体缩时,强度有所增长,但小应变刚度由于裂缝衍生而持续衰减。试样强度随损伤体变可用统一劣化方程表示。但高幅度循环下试样干燥后的小应变刚度远低于劣化线,且劣化速率远大于强度。试样滴水后能维持基本形貌,但观察到团聚体松散、微粒剥落和新生裂缝等结构劣化特征,从而导致宏观力学性能衰减。展开更多
基金supported by the National Natural Science Foundation of China(22278066,21776039)the National Key R&D Program of China(2023YFB4103001)The Fundamental Research Funds for the Central Universities(DUT2021TB03).
文摘Mercury removal from coal combustion flue gas remains a significant challenge for environmental protection due to the lack of cost-effective sorbents.In this study,a series of red mud(RM)-based sorbents impregnated with sodium halides(NaBr and NaI)are presented to capture elemental mercury(Hg^(0))from flue gas.The modified RM underwent comprehensive characterization,including analysis of its textural qualities,crystal structure,chemical composition,and thermal properties.The results indicate that the halide impregnation substantially impacts the surface area and pore size of the RM.Hg^(0) removal performance was evaluated on a fixed-bed reactor in simulated flue gas(consisting of N_(2),O_(2),CO_(2),NO and SO_(2),etc.)on a modified RM.At an optimal adsorption temperature of 160℃,NaI-modified sorbent(RMI5)offers a removal efficiency of 98%in a mixture of gas,including O_(2),NO and HCl.Furthermore,pseudo-second-order model fitting results demonstrate the chemisorption mechanism for the adsorption of Hg^(0) in kinetic investigations.
基金Project(MMCS2023OF02)supported by the Open Foundation of State Key Laboratory of Featured Metal Materials and Life-cycle Safety for Composite Structures,ChinaProject(AA23073018)supported by the Guangxi Science and Technology,ChinaProject(2024M751861)supported by the China Postdoctoral Science Foundation。
文摘Red mud is a solid waste discharged in the process of alumina production,and how to realize the efficient recovery of its iron is an urgent problem to be solved.In this study,the iron extraction test and mechanism study of high iron red mud were carried out under the coupling conditions of multiple physical field(microwave field,gas-solid flow field and temperature field)with biomass as the reducing agent.The test results showed that under the optimal conditions,an iron concentrate with a yield of 78.4%,an iron grade of 59.23%,and a recovery rate of 86.65%was obtained.The analyses of XRD,XPS,TEM,and SEM-EDS showed that during the roasting process,the hematite in the high-iron red mud was completely converted to magnetite,and the biomass produced the reductant that provided the magnetization reaction;A large number of cracks and pores appeared in the surface of the hematite reduction product particles,which helped to induce iron minerals to undergo effective mineral phase transformation.The above study provides ideas for the phase transformation and efficient recovery of iron minerals in red mud.
文摘红层泥岩水敏性高,作路基填料时可用石灰改良。受季节变化影响,路基基床经历干湿循环,导致服役性能降低。为研究干湿循环下改良填料力学特性劣化规律,开展一系列干湿循环试验、无侧限抗压试验和弯曲元试验测定改良填料无侧限抗压强度和小应变刚度。结合连续滴水扫描电镜(scanning electron microscope,简称SEM)试验,揭示干湿循环后填料微观结构劣化特征。结果表明:低幅度循环下试样在干侧和湿侧均产生体胀。高幅度循环下试样在湿侧产生体胀。在干侧先产生体缩,随循环次数增加,即使含水率较低,试样也产生体胀。体胀导致强度和小应变刚度均有不同程度的劣化。当试样产生体缩时,强度有所增长,但小应变刚度由于裂缝衍生而持续衰减。试样强度随损伤体变可用统一劣化方程表示。但高幅度循环下试样干燥后的小应变刚度远低于劣化线,且劣化速率远大于强度。试样滴水后能维持基本形貌,但观察到团聚体松散、微粒剥落和新生裂缝等结构劣化特征,从而导致宏观力学性能衰减。
