ABSTRACT
Manganese dioxide-loaded mesoporous SBA-15 silica (MnO2/SBA-15) composites with short pore length were aprepared for the first time by simply immersing SBA-15 into a KMnO4 and MnCl2 mixed solution. Adsorption of Sr2+ from aqueous solution by using the MnO2/SBA-15 was investigated by varying the pH, contact time, initial Sr2+ concentration, MnO2 content and temperature. The adsorption process was rapid during the first 40 min and reached equilibrium in 120 min. The Sr2+ adsorption capacity increased with increasing pH, MnO2 content and temperature, and the adsorption capacity of SBA-15 was significantly improved by the loading of MnO2. Moreover, the experimental adsorption data were analyzed using different equilibrium isotherm, kinetic and thermodynamic models. The results showed that the isotherm data were well-described by the Langmuir model. The maximum Sr2+ adsorption capacity was determined to be 75.1 mg g-1 at 283 K based on the Langmuir model. The analyzed kinetic data indicated that the Sr2+ adsorption process was well fitted by the pseudo-second order model. Furthermore, the thermodynamic parameters of adsorption were also determined from the equilibrium constant values obtained at different temperatures. The results suggested that the adsorption process was spontaneous and endothermic, and the overall mechanism of Sr2+ adsorption was a combination of physical and chemical processes.
Subject(s)
Manganese Compounds , Water Pollutants, Chemical , Adsorption , Hydrogen-Ion Concentration , Kinetics , Oxides , Silicon Dioxide , Strontium , Thermodynamics , Water Pollutants, Chemical/analysisABSTRACT
As a promising candidate for CO2 electroreduction, metal chalcogenides suffer from limited carrier density, which hampers the electron transport of electrocatalysts and activation of CO2. Herein, we have modified In2S3 nanosheets by in situ forming metallic In nanoparticles for enhanced CO2 electroreduction. The In-In2S3 hybrid nanosheets exhibited a remarkable geometrical current density of 70.3 mA cm-2 at -1.1 V vs. RHE, with 62.1 mA cm-2 for the carbonaceous product. The faradaic efficiency of the In-In2S3 hybrid nanosheets for the carbonaceous product reached 90% at -1.0 V vs. RHE, including 76% for formate production and 14% for CO production. The mechanistic study revealed that the improved performance by forming In nanoparticles on In2S3 nanosheets originated from the increased carrier density of the electrocatalysts and the decreased work function, which benefited the CO2 activation.
ABSTRACT
The Bi-Bi2O3-TiO2-C composites were prepared by a sol-gel method and investigated for capturing iodine-129 (129I) in off-gas producing from spent fuel reprocessing. Firstly, the optimal process conditions were operated through the orthogonal experiments, showing that the capturing capacity of the optimal composite was calculated about 504.0 ± 19.5 mg/g, which is approximately 2.0-fold higher than that of the commercial silver-exchanged zeolites (AgX). Secondly, the structure and morphology of the Bi-Bi2O3-TiO2-C composite were characterized, suggesting that the Bi is regularly spherical in the shape, coating by the Bi2O3, TiO2 and amorphous carbon. Finally, the mechanism for the iodine adsorption in the Bi-Bi2O3-TiO2-C system was revealed, demonstrating that the iodine was captured by physisorption and chemisorption.
