Studies have been made, by 15N-tracer technique on nitrogen loss resulting from adding amorphous manganese oxide to NH4+-N medium under anaerobic conditions. The fact that the total nitrogen recovery was decreased and...Studies have been made, by 15N-tracer technique on nitrogen loss resulting from adding amorphous manganese oxide to NH4+-N medium under anaerobic conditions. The fact that the total nitrogen recovery was decreased and that 15NO2, 15N2O, 15N14NO, 15NO, 15N2and 15N14N were emitted has proved that, like amorphous iron oxide, amorphous manganese oxide can also act as an electron acceptor in the oxidation of NH4+-N under anaerobic conditions and give rise to nitrogen loss. This once again illustrates another mechanism by which the loss of ammonium nitrogen in paddy soils is brought about by amorphous iron and manganese oxides. The quantity of nitrogen loss by amorphous manganese oxide increased with an increase in the amount of amorphous manganese oxide added and lessened with time of its aging. The nitrogen loss resulting from amorphous manganese oxide was less than that from amorphous iron oxide. And the nitrogen loss by cooperation of amorphous manganese oxide and microorganisms (soil suspension ) was larger than that by amorphous manganese oxide alone. In the system, nitrogen loss was associated with the specific surface area and oxidation-reduction of amorphous manganese oxide. However, their quantitative relationship and the exact reaction processes of nitrogen loss induced by amorphous manganese oxide remain to be further studied.展开更多
The relationship between iron oxides and surface charge characteristics in variable charge soils ( latosol and red earth ) was studied in following three ways. ( 1 ) Remove free iron oxides ( Fed ) and amorphous iron ...The relationship between iron oxides and surface charge characteristics in variable charge soils ( latosol and red earth ) was studied in following three ways. ( 1 ) Remove free iron oxides ( Fed ) and amorphous iron oxides ( Feo ) from the soils with sodium dithionite and acid ammonium oxalate solution respectively. ( 2 ) Add 2% glucose ( on the basis of air-dry soil weight ) to soils and incubate under submerged condition to activate iron oxides, and then the mixtures are dehydrated and air-dried to age iron oxides. ( 3 ) Precipitate various crystalline forms of iron oxides onto kaolinite. The results showed that free iron oxides ( Fed ) were the chief carrier of variable positive charges. Of which crystalline iron oxides ( Fed-Feo ) presented mainly as discrete particles in the soils and could only play a role of the carrier of positive charges, and did little influence on negative charges. Whereas the amorphous iron oxides ( Feo ) , which presented mainly as a coating with a large specific surface area, not only had positive charges, but also blocked the negative charge sites in soils. Submerged incubation activated iron oxides in the soils, and increased the amount of amorphous iron oxides and the degree of activation of iron oxide, which resulted in the increase of positive and negative charges of soils. Dehydration and air-dry aged iron oxides in soils and decreased the amount of amorphous iron oxides and the degree of activation of iron oxide, and also led to the decrease of positive and negative charges. Both the submerged incubation and the dehydration and air-dry had no significant influence on net charges. Precipitation of iron oxides onto kaolinite markedly increased positive charges and decreased negative charges. Amorphous iron oxide having a larger surface area contributed more positive charge sites and blocked more negative charge sites in kaolinite than crystalline goethite.展开更多
The main drawbacks of vanadium oxide as a cathode material are its low conductivity, low practical capacity and poor cycling stability. Adding Cr can improve its conductivity and a metastable amorphous state may provi...The main drawbacks of vanadium oxide as a cathode material are its low conductivity, low practical capacity and poor cycling stability. Adding Cr can improve its conductivity and a metastable amorphous state may provide higher capacity and stability. In this work, metastable amorphous Cr-V-O nano- particles have been successfully prepared through a facile co-precipitation reaction followed by annealing treatment. As a cathode material for lithium batteries, the metastable amorphous Cr-V-O nanoparticles exhibit high capacity （260 mAh/g at 100 mA/g between 1.5-4 V）, low capacity loss （more than 80% was retained after 200 cycles at 100 mA/g） and high rate capability （up to 3 A/g）.展开更多
文摘Studies have been made, by 15N-tracer technique on nitrogen loss resulting from adding amorphous manganese oxide to NH4+-N medium under anaerobic conditions. The fact that the total nitrogen recovery was decreased and that 15NO2, 15N2O, 15N14NO, 15NO, 15N2and 15N14N were emitted has proved that, like amorphous iron oxide, amorphous manganese oxide can also act as an electron acceptor in the oxidation of NH4+-N under anaerobic conditions and give rise to nitrogen loss. This once again illustrates another mechanism by which the loss of ammonium nitrogen in paddy soils is brought about by amorphous iron and manganese oxides. The quantity of nitrogen loss by amorphous manganese oxide increased with an increase in the amount of amorphous manganese oxide added and lessened with time of its aging. The nitrogen loss resulting from amorphous manganese oxide was less than that from amorphous iron oxide. And the nitrogen loss by cooperation of amorphous manganese oxide and microorganisms (soil suspension ) was larger than that by amorphous manganese oxide alone. In the system, nitrogen loss was associated with the specific surface area and oxidation-reduction of amorphous manganese oxide. However, their quantitative relationship and the exact reaction processes of nitrogen loss induced by amorphous manganese oxide remain to be further studied.
文摘The relationship between iron oxides and surface charge characteristics in variable charge soils ( latosol and red earth ) was studied in following three ways. ( 1 ) Remove free iron oxides ( Fed ) and amorphous iron oxides ( Feo ) from the soils with sodium dithionite and acid ammonium oxalate solution respectively. ( 2 ) Add 2% glucose ( on the basis of air-dry soil weight ) to soils and incubate under submerged condition to activate iron oxides, and then the mixtures are dehydrated and air-dried to age iron oxides. ( 3 ) Precipitate various crystalline forms of iron oxides onto kaolinite. The results showed that free iron oxides ( Fed ) were the chief carrier of variable positive charges. Of which crystalline iron oxides ( Fed-Feo ) presented mainly as discrete particles in the soils and could only play a role of the carrier of positive charges, and did little influence on negative charges. Whereas the amorphous iron oxides ( Feo ) , which presented mainly as a coating with a large specific surface area, not only had positive charges, but also blocked the negative charge sites in soils. Submerged incubation activated iron oxides in the soils, and increased the amount of amorphous iron oxides and the degree of activation of iron oxide, which resulted in the increase of positive and negative charges of soils. Dehydration and air-dry aged iron oxides in soils and decreased the amount of amorphous iron oxides and the degree of activation of iron oxide, and also led to the decrease of positive and negative charges. Both the submerged incubation and the dehydration and air-dry had no significant influence on net charges. Precipitation of iron oxides onto kaolinite markedly increased positive charges and decreased negative charges. Amorphous iron oxide having a larger surface area contributed more positive charge sites and blocked more negative charge sites in kaolinite than crystalline goethite.
文摘The main drawbacks of vanadium oxide as a cathode material are its low conductivity, low practical capacity and poor cycling stability. Adding Cr can improve its conductivity and a metastable amorphous state may provide higher capacity and stability. In this work, metastable amorphous Cr-V-O nano- particles have been successfully prepared through a facile co-precipitation reaction followed by annealing treatment. As a cathode material for lithium batteries, the metastable amorphous Cr-V-O nanoparticles exhibit high capacity （260 mAh/g at 100 mA/g between 1.5-4 V）, low capacity loss （more than 80% was retained after 200 cycles at 100 mA/g） and high rate capability （up to 3 A/g）.
