The dissolution property of high-ferrite gibbsitic bauxite and the effect of ferrite content on the dissolution kinetics of gibbsitic bauxites in sodium hydroxide solution under atmospheric pressure from 50 to 90 ...The dissolution property of high-ferrite gibbsitic bauxite and the effect of ferrite content on the dissolution kinetics of gibbsitic bauxites in sodium hydroxide solution under atmospheric pressure from 50 to 90 °C were systematically investigated.The dissolution property of high-ferrite gibbsitic bauxite is increased by increasing the dissolution temperature and the Na OH concentration or decreasing the particle size of bauxite,which is easy to dissolve under atmospheric pressure.The kinetic equations of gibbsitic bauxites with different ferrite contents during the dissolution process at different temperatures for different times were established,and the corresponding activation energies were calculated.The ferrite in the gibbsitic bauxite reduces the dissolution speed and increases the activation energy of dissolution,the diffusion process of which is the rate-controlling step.展开更多
Effects of tetracarbon additives, 1-butanol, 1,4-dioxane and tetrahydrofurane on gibbsite precipitation from caustic seeded sodium aluminate liquor were investigated. The additive was charged into supersaturated seede...Effects of tetracarbon additives, 1-butanol, 1,4-dioxane and tetrahydrofurane on gibbsite precipitation from caustic seeded sodium aluminate liquor were investigated. The additive was charged into supersaturated seeded sodium aluminate liquor, then the precipitation ratio of aluminate liquor in 10 h was evaluated and compared, and the particle size distribution of product was measured. The Mulliken atomic charge of oxygen in the additive molecule was calculated with DMol3 program. The results show that 1-butanol has little effect on gibbsite crystallization, while the precipitation ratios under the effect of 1,4-dioxane and tetrahydrofurane are 1.7% and 3.6% higher than that of the blank, respectively. The agglomeration efficiency of the product is also enhanced obviously by the addition of 1,4-dioxane and tetrahydrofurane. The precipitation ratio is inversely proportional to Mulliken atomic charge of oxygen atom, which implies that functional group in the additive molecule is involved in the gibbsite precipitation process more fundamentally than carbon chain.展开更多
The controls of soluble Al concentration were examined in three situations of acid sulfate conditions: 1)experimental acid sulfate conditions by addition of varying amounts of Al(OH)3 (gibbsite) into a sequenceof H2SO...The controls of soluble Al concentration were examined in three situations of acid sulfate conditions: 1)experimental acid sulfate conditions by addition of varying amounts of Al(OH)3 (gibbsite) into a sequenceof H2SO4 solutions; 2) experimental acid sulfate conditions by addition of the same sequence of H2SO4solutions into two non-acid sulfate soil samples with known amounts of acid oxalate extractable Al; and3) actual acid sulfate soil conditions. The experiment using gibbsite as an Al-bearing mineral showed thatincrease in the concentration of H2SO4 solution increased the soluble Al concentration, accompanied bya decrease in the solution pH. Increasing amount of gibbsite added to the H2SO4 solutions also increasedsoluble Al concentration, but resulted in an increase in solution pH. Within the H2SO4 concentration rangeof 0.0005～0.5 mol L-1 and the Al(OH)3 range of 0.01～0.5g (in 25 mL of H2SO4 solutions), the input ofH2SO4 had the major control on soluble Al concentration and pH. The availability of Al(OH)3, however, wasresponsible for the spread of the various sample points, with a tendency that the samples containing moregibbsite had a higher soluble Al concentration than those containing less gibbsite at equivalent pH levels.The experimental results from treatment of soil samples with H2SO4 solutions and the analytical results ofacid sulfate soils also showed the similar trend.展开更多
Three possible structures of the favorable growth unit Al6（OH）<sup>18 （H2O）6 of gibbsite are calculated by ab initio at STO-3G, STO-3G*, STO-6G, STO-6G*, 3-21G, 6-31G levels and DFT at RB3LYP/3-21G, B3LYP/6-...Three possible structures of the favorable growth unit Al6（OH）<sup>18 （H2O）6 of gibbsite are calculated by ab initio at STO-3G, STO-3G*, STO-6G, STO-6G*, 3-21G, 6-31G levels and DFT at RB3LYP/3-21G, B3LYP/6-31G levels. The most excellent structure of Al6（OH）<sup>18 （H2O）6 （structure [A]） is confirmed. Based on these calculation results and considering efficiency factor, ab initio at STO-3G level is selected to optimize the structure [A]. The calculation results are compared with the experimental structure parameters of correlative systems. The total energy, orbital population and atomic charge of structure [A] are calculated using Dipole & Sphere solvent model at 6-31G, B3LYP/6-31G, 6-31G*, B3LYP/6-31G*, 6-31G** and B3LYP/6-31G** levels. The bonding orientation of Al6（OH）18（H2O）6 is analyzed.展开更多
基金Projects(51104041,51174054,51374065)supported by the National Natural Science Foundation of ChinaProject(N130402010)supported by the Fundamental Research Funds for the Central Universities of China
文摘The dissolution property of high-ferrite gibbsitic bauxite and the effect of ferrite content on the dissolution kinetics of gibbsitic bauxites in sodium hydroxide solution under atmospheric pressure from 50 to 90 °C were systematically investigated.The dissolution property of high-ferrite gibbsitic bauxite is increased by increasing the dissolution temperature and the Na OH concentration or decreasing the particle size of bauxite,which is easy to dissolve under atmospheric pressure.The kinetic equations of gibbsitic bauxites with different ferrite contents during the dissolution process at different temperatures for different times were established,and the corresponding activation energies were calculated.The ferrite in the gibbsitic bauxite reduces the dissolution speed and increases the activation energy of dissolution,the diffusion process of which is the rate-controlling step.
基金Project(2005CB623702) supported by Major State Basic Research Development Program of China
文摘Effects of tetracarbon additives, 1-butanol, 1,4-dioxane and tetrahydrofurane on gibbsite precipitation from caustic seeded sodium aluminate liquor were investigated. The additive was charged into supersaturated seeded sodium aluminate liquor, then the precipitation ratio of aluminate liquor in 10 h was evaluated and compared, and the particle size distribution of product was measured. The Mulliken atomic charge of oxygen in the additive molecule was calculated with DMol3 program. The results show that 1-butanol has little effect on gibbsite crystallization, while the precipitation ratios under the effect of 1,4-dioxane and tetrahydrofurane are 1.7% and 3.6% higher than that of the blank, respectively. The agglomeration efficiency of the product is also enhanced obviously by the addition of 1,4-dioxane and tetrahydrofurane. The precipitation ratio is inversely proportional to Mulliken atomic charge of oxygen atom, which implies that functional group in the additive molecule is involved in the gibbsite precipitation process more fundamentally than carbon chain.
文摘The controls of soluble Al concentration were examined in three situations of acid sulfate conditions: 1)experimental acid sulfate conditions by addition of varying amounts of Al(OH)3 (gibbsite) into a sequenceof H2SO4 solutions; 2) experimental acid sulfate conditions by addition of the same sequence of H2SO4solutions into two non-acid sulfate soil samples with known amounts of acid oxalate extractable Al; and3) actual acid sulfate soil conditions. The experiment using gibbsite as an Al-bearing mineral showed thatincrease in the concentration of H2SO4 solution increased the soluble Al concentration, accompanied bya decrease in the solution pH. Increasing amount of gibbsite added to the H2SO4 solutions also increasedsoluble Al concentration, but resulted in an increase in solution pH. Within the H2SO4 concentration rangeof 0.0005～0.5 mol L-1 and the Al(OH)3 range of 0.01～0.5g (in 25 mL of H2SO4 solutions), the input ofH2SO4 had the major control on soluble Al concentration and pH. The availability of Al(OH)3, however, wasresponsible for the spread of the various sample points, with a tendency that the samples containing moregibbsite had a higher soluble Al concentration than those containing less gibbsite at equivalent pH levels.The experimental results from treatment of soil samples with H2SO4 solutions and the analytical results ofacid sulfate soils also showed the similar trend.
文摘Three possible structures of the favorable growth unit Al6（OH）<sup>18 （H2O）6 of gibbsite are calculated by ab initio at STO-3G, STO-3G*, STO-6G, STO-6G*, 3-21G, 6-31G levels and DFT at RB3LYP/3-21G, B3LYP/6-31G levels. The most excellent structure of Al6（OH）<sup>18 （H2O）6 （structure [A]） is confirmed. Based on these calculation results and considering efficiency factor, ab initio at STO-3G level is selected to optimize the structure [A]. The calculation results are compared with the experimental structure parameters of correlative systems. The total energy, orbital population and atomic charge of structure [A] are calculated using Dipole & Sphere solvent model at 6-31G, B3LYP/6-31G, 6-31G*, B3LYP/6-31G*, 6-31G** and B3LYP/6-31G** levels. The bonding orientation of Al6（OH）18（H2O）6 is analyzed.
