Owing to outstanding hydrophilicity and ionic interaction,layered double hydroxides(LDHs)have emerged as a promising carrier for high performance catalysts.However,the synthesis of new specialized catalytic LDHs for d...Owing to outstanding hydrophilicity and ionic interaction,layered double hydroxides(LDHs)have emerged as a promising carrier for high performance catalysts.However,the synthesis of new specialized catalytic LDHs for degradation of antibiotics still faces some challenges.In this study,a CoFe_(2)O_(4)/MgAl-LDH composite catalyst was synthesized using a hydrothermal coprecipitation method.Comprehensive characterization reveals that the surface of MgAl-LDH is covered with nanometer CoFe_(2)O_(4) particles.The specific surface area of CoFe_(2)O_(4)/MgAl-LDH is 82.84 m^(2)·g^(-)1,which is 2.34 times that of CoFe_(2)O_(4).CoFe_(2)O_(4)/MgAl-LDH has a saturation magnetic strength of 22.24 A·m^(2)·kg^(-1) facilitating efficient solid-liquid separation.The composite catalyst was employed to activate peroxymonosulfate(PMS)for the efficient degradation of tetracycline hydrochloride(TCH).It is found that the catalytic performance of CoFe_(2)O_(4)/MgAl-LDH significantly exceeds that of CoFe_(2)O_(4).The maximum TCH removal reaches 98.2%under the optimal conditions([TCH]=25 mg/L,[PMS]=1.5 mmol/L,CoFe_(2)O_(4)/MgAl-LDH=0.20 g/L,pH 7,and T=25℃).Coexisting ions in the solution,such as SO_(4)^(2-),Cl-,H_(2)PO_(4)^(-),and CO_(3)^(2-),have a negligible effect on catalytic performance.Cyclic tests demonstrate that the catalytic performance of CoFe_(2)O_(4)/MgAl-LDH remains 67.2%after five cycles.Mechanism investigations suggest that O_(2)^(•-)and ^(1)O_(2) produced by CoFe_(2)O_(4)/MgAl-LDH play a critical role in the catalytic degradation.展开更多
To protect carbon/carbon (C/C) composites from oxidation, a SiC coating modified with SiO2 was prepared by a complex technology. The inner SiC coating with thickness varying from 150 to 300 μm was initially coated by...To protect carbon/carbon (C/C) composites from oxidation, a SiC coating modified with SiO2 was prepared by a complex technology. The inner SiC coating with thickness varying from 150 to 300 μm was initially coated by chemical vapor reaction (CVR): a simple and cheap technique to prepare the SiC coating via siliconizing the substrate that was exposed to the mixed vapor (Si and SiO2) at high temperatures (1 923?2 273 K). Then the as-prepared coating was processed by a dipping and drying procedure with tetraethoxysilane as source materials to form SiO2 to fill the cracks and holes. Oxidation tests show that, after oxidation in air at 1 623 K for 10 h and thermal cycling between 1 623 K and room temperature 5 times, the mass loss of the CVR coated sample is up to 18.21%, while the sample coated with modified coating is only 5.96%, exhibiting an obvious improvement of oxidation and thermal shock resistance of the coating. The mass loss of the modified sample is mainly contributed to the reaction of C/C substrate with oxygen diffusing through the penetrating cracks formed in thermal shock tests.展开更多
基金University Synergy Innovation Program of Anhui Province(GXXT-2022-083)Science and Technology Plan Project of Wuhu City,China(2023kx12)Anhui Provincial Department of Education New Era Education Project(2023xscx070)。
文摘Owing to outstanding hydrophilicity and ionic interaction,layered double hydroxides(LDHs)have emerged as a promising carrier for high performance catalysts.However,the synthesis of new specialized catalytic LDHs for degradation of antibiotics still faces some challenges.In this study,a CoFe_(2)O_(4)/MgAl-LDH composite catalyst was synthesized using a hydrothermal coprecipitation method.Comprehensive characterization reveals that the surface of MgAl-LDH is covered with nanometer CoFe_(2)O_(4) particles.The specific surface area of CoFe_(2)O_(4)/MgAl-LDH is 82.84 m^(2)·g^(-)1,which is 2.34 times that of CoFe_(2)O_(4).CoFe_(2)O_(4)/MgAl-LDH has a saturation magnetic strength of 22.24 A·m^(2)·kg^(-1) facilitating efficient solid-liquid separation.The composite catalyst was employed to activate peroxymonosulfate(PMS)for the efficient degradation of tetracycline hydrochloride(TCH).It is found that the catalytic performance of CoFe_(2)O_(4)/MgAl-LDH significantly exceeds that of CoFe_(2)O_(4).The maximum TCH removal reaches 98.2%under the optimal conditions([TCH]=25 mg/L,[PMS]=1.5 mmol/L,CoFe_(2)O_(4)/MgAl-LDH=0.20 g/L,pH 7,and T=25℃).Coexisting ions in the solution,such as SO_(4)^(2-),Cl-,H_(2)PO_(4)^(-),and CO_(3)^(2-),have a negligible effect on catalytic performance.Cyclic tests demonstrate that the catalytic performance of CoFe_(2)O_(4)/MgAl-LDH remains 67.2%after five cycles.Mechanism investigations suggest that O_(2)^(•-)and ^(1)O_(2) produced by CoFe_(2)O_(4)/MgAl-LDH play a critical role in the catalytic degradation.
基金Project(2006CB600901) supported by the National Basic Research Program of ChinaProject(50802115) supported by the National Natural Science Foundation of China
文摘To protect carbon/carbon (C/C) composites from oxidation, a SiC coating modified with SiO2 was prepared by a complex technology. The inner SiC coating with thickness varying from 150 to 300 μm was initially coated by chemical vapor reaction (CVR): a simple and cheap technique to prepare the SiC coating via siliconizing the substrate that was exposed to the mixed vapor (Si and SiO2) at high temperatures (1 923?2 273 K). Then the as-prepared coating was processed by a dipping and drying procedure with tetraethoxysilane as source materials to form SiO2 to fill the cracks and holes. Oxidation tests show that, after oxidation in air at 1 623 K for 10 h and thermal cycling between 1 623 K and room temperature 5 times, the mass loss of the CVR coated sample is up to 18.21%, while the sample coated with modified coating is only 5.96%, exhibiting an obvious improvement of oxidation and thermal shock resistance of the coating. The mass loss of the modified sample is mainly contributed to the reaction of C/C substrate with oxygen diffusing through the penetrating cracks formed in thermal shock tests.
