Green rusts with brucite-like layers of hydroxide intercalated with anions constitute a family of diverse precursors for the synthesis of iron oxides via dehydration,but precise structural control of the resulting oxi...Green rusts with brucite-like layers of hydroxide intercalated with anions constitute a family of diverse precursors for the synthesis of iron oxides via dehydration,but precise structural control of the resulting oxides with respect to the size and shape at the nanometer level remains challenging due to the easy oxidation of the ferrous species.Herein,we report a new synthetic strategy for the facile preparation of fibrous-like green rusts by using appropriate balancing anions(CO_(3)^(2-)and SO_(4)^(2-))in ethylene glycol to regulate the morphology.Depending on the type of the intercalating anion,the green rusts were converted into hematite with fibrous-or plate-like shapes upon thermal activation.When evaluated in the reaction of NO reduction by CO,these iron oxides showed a prominent shape-dependent catalytic behavior.The fibrous-like Fe_(2)O_(3)was much more catalytically active and structurally robust than the plate-like analogue.Combined spectroscopic and microscopic characterizations on the nanostructured iron oxides revealed that the superior performance of the fibrous-like Fe_(2)O_(3)stemmed from a facile Fe_(2)O_(3)/Fe_(3)O_(4)redox cycle and a higher density of active sites for NO activation.展开更多
Over the last ten years, several comprehensive reviews of iron thermodynamics data were published. This work aims to： （i） propose a consistent set of Gibbs free energies （AfG~） of ferrous hydroxide, Fe（OH）2.cr ...Over the last ten years, several comprehensive reviews of iron thermodynamics data were published. This work aims to： （i） propose a consistent set of Gibbs free energies （AfG~） of ferrous hydroxide, Fe（OH）2.cr and of synthetic Green rusts I and II; （ii） check the consistency of the data of these isostructural compounds by means of a correlation obtained with electronegativities of the anions. Experimental data are concentrations in aqueous solutions and pH, and must be processed to obtain ionic activity products （lAP）. The model of Specific Interaction Theory （SIT） was used here. Firstly, some complexes whose existences are doubtful were removed from the SIT database. The new modified database is given here. Secondly, experimental data were processed. Thirdly, the following relation of regression between Gibbs free energies of formation of Green rusts and normalized Allred-Rochow electronegativities of anions was obtained as： △fG0 = -488.354 -353.11 （x/n）, r = -0.994. This relation was then used to assess the Gibbs free energy of formation for GR1-OH, simply written as Fe3（OH）7.展开更多
The layered laurylsulfonate intercalated green rust(lauryl-S GR) was synthesized to evaluate the influence of synthesis parameters and aqueous conditions on the adsorption of CeⅣ.The maximum adsorption capacity of 30...The layered laurylsulfonate intercalated green rust(lauryl-S GR) was synthesized to evaluate the influence of synthesis parameters and aqueous conditions on the adsorption of CeⅣ.The maximum adsorption capacity of 305.58 mg/g by lauryl-S GR was predictably obtained.The pseudo-first-order kinetic model was appropriate in fitting the whole uptake process in a weak acid environment.Three isotherm models including Langmuir, Freundlich, and Tempkin were all reliable in depicting the isotherm adsorption process.The maximum monolayer adsorption capacity of lauryl-S GR towards CeⅣ was 315.46 mg/g.Ce species including CeO and Ce_(2)O_(3) besides CeO_(2) were matched in the XPS distribution, directly indicating the reduction reaction brought by FeⅡ in the GR occurred to hydrated CeⅣ ions during the adsorption.Nano-sized Ce particles attached to the lauryl-S GRs after the adsorption experiments were observed in the morphological characterization.Flocculated materials were formed on the surface of the lauryl-S GR at a pH of 7, which further reduced the active sites and disrupted the continuous uptake of CeⅣ to the lauryl-S GR.This study expands the application of GRs and supplies an ideal iron-based material for the construction of the affiliated recovery pathway to the traditional separation of Ce.展开更多
The re moval efficiency of pollutants in Fe(O) electrocoagulation(EC) has been associated closely with the speciation of generated Fe(Ⅱ)/Fe(Ⅲ) oxides during this process,which is very complicated and can be affected...The re moval efficiency of pollutants in Fe(O) electrocoagulation(EC) has been associated closely with the speciation of generated Fe(Ⅱ)/Fe(Ⅲ) oxides during this process,which is very complicated and can be affected by various factors.In this work,in-situ Raman,X-ray diffraction and some other techniques have been used to study the speciation of Fe under different conditions and to establish a relationship between Fe speciation and Sb(V) removal efficiency.Results indicated that concentration of dissolved oxygen(DO)is a key factor influencing Fe(O) EC.It was found that green rusts(GRs) were formed and were then transformed into magnetite at lower DO concentration,and Sb(V) removal efficiency reached 99.9% after30 min of EC.In contrast,γ-FeOOH was formed at high DO concentration,and the removal efficiency of Sb(V) after 30 min of EC was only 72.8%.In the presence of sulfite and phosphate with low concentrations,GRs can be stabilized and benefit the removal of Sb(V).We believe this work will provide some new insights on the mechanism of Fe(O) EC and the effective removal of other pollutants during Fe(O)EC process.展开更多
基金Zhejiang Normal University for providing the financial support(YS304320035)。
文摘Green rusts with brucite-like layers of hydroxide intercalated with anions constitute a family of diverse precursors for the synthesis of iron oxides via dehydration,but precise structural control of the resulting oxides with respect to the size and shape at the nanometer level remains challenging due to the easy oxidation of the ferrous species.Herein,we report a new synthetic strategy for the facile preparation of fibrous-like green rusts by using appropriate balancing anions(CO_(3)^(2-)and SO_(4)^(2-))in ethylene glycol to regulate the morphology.Depending on the type of the intercalating anion,the green rusts were converted into hematite with fibrous-or plate-like shapes upon thermal activation.When evaluated in the reaction of NO reduction by CO,these iron oxides showed a prominent shape-dependent catalytic behavior.The fibrous-like Fe_(2)O_(3)was much more catalytically active and structurally robust than the plate-like analogue.Combined spectroscopic and microscopic characterizations on the nanostructured iron oxides revealed that the superior performance of the fibrous-like Fe_(2)O_(3)stemmed from a facile Fe_(2)O_(3)/Fe_(3)O_(4)redox cycle and a higher density of active sites for NO activation.
文摘Over the last ten years, several comprehensive reviews of iron thermodynamics data were published. This work aims to： （i） propose a consistent set of Gibbs free energies （AfG~） of ferrous hydroxide, Fe（OH）2.cr and of synthetic Green rusts I and II; （ii） check the consistency of the data of these isostructural compounds by means of a correlation obtained with electronegativities of the anions. Experimental data are concentrations in aqueous solutions and pH, and must be processed to obtain ionic activity products （lAP）. The model of Specific Interaction Theory （SIT） was used here. Firstly, some complexes whose existences are doubtful were removed from the SIT database. The new modified database is given here. Secondly, experimental data were processed. Thirdly, the following relation of regression between Gibbs free energies of formation of Green rusts and normalized Allred-Rochow electronegativities of anions was obtained as： △fG0 = -488.354 -353.11 （x/n）, r = -0.994. This relation was then used to assess the Gibbs free energy of formation for GR1-OH, simply written as Fe3（OH）7.
基金supported by the China Postdoctoral Science Foundation (No.2020M681774)the Natural Science Foundation of the Jiangsu Higher Education institutions of China (No.20KJB490001)the University of South China (No.190XQ073)。
文摘The layered laurylsulfonate intercalated green rust(lauryl-S GR) was synthesized to evaluate the influence of synthesis parameters and aqueous conditions on the adsorption of CeⅣ.The maximum adsorption capacity of 305.58 mg/g by lauryl-S GR was predictably obtained.The pseudo-first-order kinetic model was appropriate in fitting the whole uptake process in a weak acid environment.Three isotherm models including Langmuir, Freundlich, and Tempkin were all reliable in depicting the isotherm adsorption process.The maximum monolayer adsorption capacity of lauryl-S GR towards CeⅣ was 315.46 mg/g.Ce species including CeO and Ce_(2)O_(3) besides CeO_(2) were matched in the XPS distribution, directly indicating the reduction reaction brought by FeⅡ in the GR occurred to hydrated CeⅣ ions during the adsorption.Nano-sized Ce particles attached to the lauryl-S GRs after the adsorption experiments were observed in the morphological characterization.Flocculated materials were formed on the surface of the lauryl-S GR at a pH of 7, which further reduced the active sites and disrupted the continuous uptake of CeⅣ to the lauryl-S GR.This study expands the application of GRs and supplies an ideal iron-based material for the construction of the affiliated recovery pathway to the traditional separation of Ce.
基金the National Key R&D Program of China(No.2016YFC0401405)National Natural Science Foundation of China(No.51808512)。
文摘The re moval efficiency of pollutants in Fe(O) electrocoagulation(EC) has been associated closely with the speciation of generated Fe(Ⅱ)/Fe(Ⅲ) oxides during this process,which is very complicated and can be affected by various factors.In this work,in-situ Raman,X-ray diffraction and some other techniques have been used to study the speciation of Fe under different conditions and to establish a relationship between Fe speciation and Sb(V) removal efficiency.Results indicated that concentration of dissolved oxygen(DO)is a key factor influencing Fe(O) EC.It was found that green rusts(GRs) were formed and were then transformed into magnetite at lower DO concentration,and Sb(V) removal efficiency reached 99.9% after30 min of EC.In contrast,γ-FeOOH was formed at high DO concentration,and the removal efficiency of Sb(V) after 30 min of EC was only 72.8%.In the presence of sulfite and phosphate with low concentrations,GRs can be stabilized and benefit the removal of Sb(V).We believe this work will provide some new insights on the mechanism of Fe(O) EC and the effective removal of other pollutants during Fe(O)EC process.
