Trivalent chromium(Cr(Ⅲ))can form stable soluble complexes with organic components,altering its adsorption properties in the water-soil environment.This increases the risk of Cr(Ⅲ)migrating to deeper soils and trans...Trivalent chromium(Cr(Ⅲ))can form stable soluble complexes with organic components,altering its adsorption properties in the water-soil environment.This increases the risk of Cr(Ⅲ)migrating to deeper soils and transforming into toxic Cr(VI)due to the presence of manganese oxides in sediments.In this study,Citric Acid(CA)was selected as a representative organic ligand to prepare and characterize Cr(III)-CA complexes.The characteristics,mechanisms and environmental factors influencing the adsorption of Cr(Ⅲ)-CA on porous media(silts and fine sands)were investigated in the study.The results show that Cr(Ⅲ)coordinates with CA at a 1:1 molar ratio,forming stable and soluble Cr(Ⅲ)-CA complexes.Compared to Cr(III)ions,the equilibrium adsorption capacity of Cr(Ⅲ)-CA is an order of magnitude lower in silts and fine sands.The adsorption of Cr(Ⅲ)-CA in silts and fine sands is dominated by chemical adsorption of monolayers,following the pseudo-second-order kinetic equation and the Langmuir isotherm adsorption model.Varying contents of clay minerals and iron-aluminum oxides prove to be the main causes of differences in adsorption capacity of Cr(Ⅲ)-CA in silts and fine sands.Changes in solution pH affect the adsorption rate and capacity of Cr(Ⅲ)-CA by altering its ionic form.The adsorption process is irreversible and only minimally influenced by ionic strength,suggesting that inner-sphere complexation serves as the dominant Cr(Ⅲ)-CA adsorption mechanism.展开更多
Co（Ⅱ）-salen was encapsulated in MIL- 100（Cr） metal organic framework by ＂ship in a bottle＂ to synthesize a new electrocatalyst, Cosalen@MIL- 100（Cr）. The material was characterized by XRD, FT-IR, UV-Vis and N...Co（Ⅱ）-salen was encapsulated in MIL- 100（Cr） metal organic framework by ＂ship in a bottle＂ to synthesize a new electrocatalyst, Cosalen@MIL- 100（Cr）. The material was characterized by XRD, FT-IR, UV-Vis and N2-adsorption. The Cosalen@MIL-100（Cr） modified glassy carbon electrode exhibits a well-defined reduction peak at the potential of -0.21 V toward the oxygen reduction reaction （ORR） by cyclic voltam- metry （CV） in pH = 6.84 phosphate buffer. Almost 400 mV positive shift of potential at Cosalen@MIL-100（Cr） modified electrode for ORR compared with that at bare glassy carbon, indicates that Cosalen@MIL-100（Cr） possesses excellent electrocatalytic activity. The transferred number of electrons for ORR was determined by chronocoulometry. The result suggests that the introduction of Co（II）-salen complex into MOF increases the electrocatalytic activity via a four-electron reduction pathway. Furthermore, this electrocatalyst exhibits good stability and reproducibility.展开更多
We perform a detailed investigation of the new ＇breathing＇ pyrochlore compound LiInCr4O8 through Rh substi- tution with measurements of magnetic susceptibility, specific heat, and x-ray powder diffraction. The antif...We perform a detailed investigation of the new ＇breathing＇ pyrochlore compound LiInCr4O8 through Rh substi- tution with measurements of magnetic susceptibility, specific heat, and x-ray powder diffraction. The antiferro- magnetic phase of LiInCr4O8 is found to be slowly suppressed with increasing Rh, up to the critical concentration of x = 0.1 where the antiferromagnetic phase is still observed with the peak in specific heat Tp = 12.5 K, slightly lower than Tp =14.3 K for the x = 0 compound. From tile measurements of magnetization we also uncover evidence that substitution increases the amount of frustration. Comparisons are made with the LiGayIn1-yCr4O8 system as well as other frustrated pyrochlore-related materials and comparable amounts of frustration are found. The results of this work show that the engineered breathing pyrochlores present an important method to further understand the complex magnetism in frustrated systems.展开更多
基金financially supported jointly by Natural Science Foundation of Fujian Province of China(NO.2023J01227)Natural Science Foundation of Hebei Province(NO.D2020504003)Key Laboratory of Groundwater Remediation of Hebei Province and China Geological Survey(NO.SK202303).
文摘Trivalent chromium(Cr(Ⅲ))can form stable soluble complexes with organic components,altering its adsorption properties in the water-soil environment.This increases the risk of Cr(Ⅲ)migrating to deeper soils and transforming into toxic Cr(VI)due to the presence of manganese oxides in sediments.In this study,Citric Acid(CA)was selected as a representative organic ligand to prepare and characterize Cr(III)-CA complexes.The characteristics,mechanisms and environmental factors influencing the adsorption of Cr(Ⅲ)-CA on porous media(silts and fine sands)were investigated in the study.The results show that Cr(Ⅲ)coordinates with CA at a 1:1 molar ratio,forming stable and soluble Cr(Ⅲ)-CA complexes.Compared to Cr(III)ions,the equilibrium adsorption capacity of Cr(Ⅲ)-CA is an order of magnitude lower in silts and fine sands.The adsorption of Cr(Ⅲ)-CA in silts and fine sands is dominated by chemical adsorption of monolayers,following the pseudo-second-order kinetic equation and the Langmuir isotherm adsorption model.Varying contents of clay minerals and iron-aluminum oxides prove to be the main causes of differences in adsorption capacity of Cr(Ⅲ)-CA in silts and fine sands.Changes in solution pH affect the adsorption rate and capacity of Cr(Ⅲ)-CA by altering its ionic form.The adsorption process is irreversible and only minimally influenced by ionic strength,suggesting that inner-sphere complexation serves as the dominant Cr(Ⅲ)-CA adsorption mechanism.
基金supported by the Program for New Century Excellent Talents in University(NCET-04-0270)the National Basic Research Program of China(2011CB201301)
文摘Co（Ⅱ）-salen was encapsulated in MIL- 100（Cr） metal organic framework by ＂ship in a bottle＂ to synthesize a new electrocatalyst, Cosalen@MIL- 100（Cr）. The material was characterized by XRD, FT-IR, UV-Vis and N2-adsorption. The Cosalen@MIL-100（Cr） modified glassy carbon electrode exhibits a well-defined reduction peak at the potential of -0.21 V toward the oxygen reduction reaction （ORR） by cyclic voltam- metry （CV） in pH = 6.84 phosphate buffer. Almost 400 mV positive shift of potential at Cosalen@MIL-100（Cr） modified electrode for ORR compared with that at bare glassy carbon, indicates that Cosalen@MIL-100（Cr） possesses excellent electrocatalytic activity. The transferred number of electrons for ORR was determined by chronocoulometry. The result suggests that the introduction of Co（II）-salen complex into MOF increases the electrocatalytic activity via a four-electron reduction pathway. Furthermore, this electrocatalyst exhibits good stability and reproducibility.
基金Supported by the Ministry of Science and Technology under Grant No 2016YFA0300503
文摘We perform a detailed investigation of the new ＇breathing＇ pyrochlore compound LiInCr4O8 through Rh substi- tution with measurements of magnetic susceptibility, specific heat, and x-ray powder diffraction. The antiferro- magnetic phase of LiInCr4O8 is found to be slowly suppressed with increasing Rh, up to the critical concentration of x = 0.1 where the antiferromagnetic phase is still observed with the peak in specific heat Tp = 12.5 K, slightly lower than Tp =14.3 K for the x = 0 compound. From tile measurements of magnetization we also uncover evidence that substitution increases the amount of frustration. Comparisons are made with the LiGayIn1-yCr4O8 system as well as other frustrated pyrochlore-related materials and comparable amounts of frustration are found. The results of this work show that the engineered breathing pyrochlores present an important method to further understand the complex magnetism in frustrated systems.
