Search

The modified pomelo peel powder was prepared by using chemical modification methods of ZnCl2 soaking and heating.The removal rate of Pb (II) ion in simulation of wastewater by the modified pomelo peel powder was tested. The effects of pH of wastewater, initial concentrations of Pb (II) ion, adsorbent dosage,temperature and time on adsorption of Pb (II) ion was studied. Results show that when Pb (II) ion initial concentration at 100 mgL-1, pH of wastewater at 3.5-5.5, adsorption time at 100min, adsorbent dosage at 15gL-1, temperature at 35°C, the removal rate of Pb (II) ion in simulation of wastewater by the modified pomelo peel powder was more than 95%.

LiFe0.05Mn1.95O4 materials were prepared by molten-salts combustion synthesis and solution combustion synthesis methods, respectively. The phase structure and compositions of the products were determined by X-ray diffraction (XRD). The main phase of the products prepared by the two methods is LiMn2O4, but at 300-600oC, pure products can not be obtained. At the temperatures of 300 and 400oC, the main impurities are MnO and Mn3O4. The impurities decrease with increasing temperatures, and finally disappear at >500oC. At 500 and 600oC, the main impurity is Mn2O3, but the relative content of Mn2O3 is low.

In this paper, LiNixMn2−xO4 materials were prepared by solution combustion synthesis method using acetic salts as raw materials and acetic acid as fuel. The phase structures are characterized by X-ray diffraction (XRD). Electrochemical performances of the materials are investigated by galvanostatic charge/discharge methods. XRD results revealed that the main phase of the products with increasing Ni3+ content is LiMn2O4, and there is a trace amount of Mn3O4 found in the product with Ni3+ content of 0.05. Electrochemical experiments showed that the capacity and the cyclability of the LiNixMn2−xO4 materials decrease with increasing Ni3+ content. Ni3+ doping has no significantly improvement for the capacity and the cyclability of the LiMn2O4 spinel.

LiAl0.1Mn1.9O4 materials were prepared by a solution combustion synthesis method. In order to improve the purity of the products, the effect of further calcination time was investigated. The phase compositions of the as-prepared products were determined by X-ray diffraction (XRD). The electrochemical performance of the products was tested by using a coin-type half battery versus lithium metal foil as anode material. XRD results suggested that the main phase of the products was LiAl0.1Mn1.9O4, and there was a trace amount Mn2O3 impurity in some of the products. The purity, crystallinity and grain size of the LiAl0.1Mn1.9O4 were increased with increasing further calcination time. Electrochemical experiments demonstrate that the initial discharge capacities of the products with further calcination time of 0, 6, 12 and 24h were 93.7, 105.7, 114.0 and 120.6mAh/g, and about 89.8, 89.5, 89.2 and 88.3% of the initial capacities were retained after 25 cycles, respectively. Further calcination time can enhance the initial capacity, but is not favorable for the cycle ability of the products.

Spinel LiMn2O4 have been prepared by the solution combustion synthesis method using acetate salts as raw materials and acetic acid as fuel. The phase compositions of the as-prepared products were determined by X-ray diffraction (XRD). The electrochemical performance of the products was tested by using a coin-type half battery versus lithium metal foil as anode material. XRD results suggested that the purities of the products prepared at 500oC are higher than these of the products prepared at 600oC. For the products prepared at 500oC, the purities of the products increase with increasing acetic acid ratios. But for the products prepared at 600oC, the purities of the products decrease with increasing acetic acid ratios. The performance tests indicated that the electrochemical performances of the products prepared at 500oC are better than these of the products prepared at 600oC. The product prepared at 500oC with the acetic acid ratio of 1.0 gets the best performance. The initial capacity of it reaches to 124.8mAh/g at the current density of 75mA/g, and after 50 cycles, the capacity retention is 93.7%.

Spinel LiMn2O4 was synthesized by a solution combustion synthesis using lithium and manganese acetate as raw materials and acetic acid as fuel. The phase composition and micro morphology of the as-prepared products were determined by X-ray diffraction (XRD) and scanning electric microscope (SEM). The electrochemical performance of the products was tested by using a coin-type half battery versus lithium metal foil as anode material. XRD analysis suggested that the main phase of the products was LiMn2O4, but there was little impurity Mn2O3 in the products. The relative content of Mn2O3 was decreased gradually when the molar ratio of Li:Mn: acetic acid increased from 0.5:1:0.5 to 0.5:1:2, but increased again when the molar ratio of Li:Mn: acetic acid was 0.5:1:2.5. The purest product could be prepared when the molar ratio of Li:Mn: acetic acid=0.5:1:2. SEM investigation indicated that the typical crystal structure could not be investigated from the as-prepared products, and the particles were badly agglomerated. Electrochemical performance tests indicated that the specific capacity of the purest product was 108mAh/g. After 30 cycles, the capacity faded only 22% at the current density of 50mA/g, and the average charge/discharge efficiency was ~96%. At the current density of 75mA/g, the initial specific capacity of the purest product was only 72mAh/g, but after 30 cycles, the capacity retention was >92%, exhibiting a good cycling performance.

Spinel LiMn2O4 have been prepared by a flameless solution combustion synthesis, using nitrate and acetate salts as raw materials without any fuels. The effect of ignition temperature on the phase structure, micro morphology and electrochemical performance has been studied. The results indicate that spinel LiMn2O4 with single phase can be prepared successfully by the present method at the ignition temperatures of 300-800oC and calcination temperature of 600oC for 5h. The crystallinity, dispersity of the gains and electrochemical performance of the products increase with the decreasing ignition temperatures.

To improve the cyclability of spinel LiMn2O4, Al3+ doped LiAlxMn2−xO4 (x=0, 0.01, 0.05 and 0.10) materials are prepared using a solution combustion synthesis method using acetic salts as raw materials and acetic acid as fuel. Their phase structures are characterized by X-ray diffraction (XRD). Electrochemical performances of the materials are investigated by galvanostatic charge/discharge methods. XRD results reveal that the purity of the samples increases with increasing Al3+ content. Electrochemical experiments demonstrate that the charge/discharge cyclability of the LiAlxMn2-xO4 increases with increasing Al3+ content. Compared with the pristine LiMn2O4, the Al-doped LiAlxMn1−xO4 show the obviously improved cyclability, especially for the sample LiAl0.1Mn1.9O4.

In this paper, spinel LiMn2O4 was prepared by the solution combustion synthesis using acetate or nitrate salts as raw materials and acetic acid as fuel. The composition and phase structure are determined by X-ray diffraction (XRD) and the electrochemical performance is tested by using a coin type half-battery versus Li+/Li. The results indicate that the products prepared from acetate salts have higher purities, higher crystallinities and better electrochemical performances than these of the products prepared from nitrate salts. And for the products prepared from acetate salts, the performance becomes worse with increasing acetic acid ratios. Contrarily, for the products prepared from nitrate salts, the performance becomes little better with increasing acetic acid ratios.

In this paper, a low-temperature self-mixing combustion synthesis method was introduced to prepare spinel LiMn2O4. Low-melting raw materials and fuel (acetate salts as starting materials and urea as fuel) were molten to a homogeneous liquid mixture at ~100oC. The mixture was then ignited and calcined at a higher temperature, final products were obtained. The products were determined by X-ray diffraction (XRD) and scanning electric microscope (SEM). XRD analysis indicated that product with higher purity was obtained at 550oC for 5h when the molar ratio of Li:Mn:urea=1:2:4. The impurity Mn2O3 was appeared in the products when the igniting temperature >600oC, and the content of Mn2O3 increased with the increasing igniting temperatures. SEM investigation indicated that the particles of the products were small and agglomerated. The igniting temperature monitoring indicated that the combustion reaction rate increased with increasing igniting temperature, and this did not favor for the formation of LiMn2O4.

A templated carbon has been prepared by using a clinoptilolite-Ca mineral as template and furfuralcohol as carbon source. X-ray diffraction (XRD), nitrogen adsorption, scanning electric microscope (SEM) and cyclic voltammetry (CV) are used to analyze the phase composition, pore structure, micro morphology and electrochemical performance. The specific surface area of the templated carbon is 590m2/g and the mesoporosity is high to 63.4%. In H2SO4 medium, due to its rich mesopores, the carbon exhibits a large capacity and a good rate capability. The capacity of the carbon is 174F/g at a scan rate of 5mV/s. When the scan rate increases from 5 to 300mV/s, the capacity of the carbon decreases only from 174 to 144F/g, exhibiting a good rate capability.

Fe doped LiFexMn2-xO4 materials were prepared by a low-temperature molten-salt combustion synthesis method. The phase structure and compositions of the products were determined by X-ray diffraction (XRD). The investigation on Fe doping content indicated that the main phase of the as-prepared products was LiFexMn2-xO4, and the impurity was Mn2O3. With increasing Fe doping content, the relative content of Mn2O3 and the lattice parameter of the products were decreased, and the crystallinity was increased. The study of the calcination temperature on LiFe0.1Mn1.9O4 suggested that the main phase of the LiFe0.1Mn1.9O4 materials prepared at 300-600oC was LiFe0.1Mn1.9O4. Mn3O4 and MnO impurities could be investigated in the product prepared at 300oC, and single impurity Mn2O3 could be observed in the products prepared at 400-600oC. The relative content of Mn2O3 decreased, and the lattice parameters and grain size of the products were increased with increasing calcination temperatures.

A porous carbon was prepared by template method using a mazzite mineral as a template. X-ray diffraction (XRD), nitrogen adsoption, scanning electric microscope (SEM) and cyclic voltammetry (CV) were used to investigate the phase composition, pore structure, morphology and electrochemical performance of the carbon. The surface area of the carbon is 511m2/g. The pores of the carbon are mcropores and mesopores. In H2SO4 medium, the carbon exhibits a low capacity and a rectangle-like shaped CV curve at low scan rate. When the scan rate increases from 10 to 200mV/s, the capacity decreases only from 47 to 41F/g, and the rectangle-like shape keeps well. The carbon exhibits an excellent rate capability.

Spinel LiMn2O4 were prepared by a molten salt combustion method at 600oC. The phase composition of the products was investigated by X-ray diffraction (XRD), and the electrochemical performance was tested by a coin-type self battery. XRD results presented that the purity and the crystallinity of the products increased with extending calcining time. Single phase LiMn2O4 could be prepared at 600oC for 6 and 12h. The ratio of lithium/manganese also affected the phase compositions of the products. The purity and crystallinity of the product with the molar ratio of Li/Mn=1.1/2 were higher than these of the product with the molar ratio of Li/Mn=1.05/2. The performance tests indicated that the electrochemical performance of the product prepared at 600oC for 6h is the best. The initial discharge capacity was 112.8mAh/g, and after 20 cycles, the capacity retention is 81.8%. The product with Li/Mn=1.1/2 had better electrochemical performance than the product with Li/Mn=1.05/2.