Comprehensive Utilization Of High Iron Bauxite

China has large reserves of high iron bauxite,the mass ratio of aluminum and iron is greater than 1:1,and the mass ratio of is less than 3:1,which is not suitable as the raw material to produce alumina.In present,the processes of high iron bauxite are mainly alkali methods,existing the disadvantages of lower comprehensive utilization of aluminum and iron,long technical process route and high energy consumption.Ammonium sulfate roasting-water leaching has shown great advantages in treating such bauxite.Researches on the efficient separation and utilization of aluminum and iron in high iron bauxite is of great significance to alleviate the dependence of China's aluminum and iron ore on imports.In this paper,the clean and comprehensive utilization of high iron bauxite using the process of ammonium sulfate roasting-water leaching.The technical process route of ammonium sulfate roasting-water leaching was designed;Single factor experiment and orthogonal experiment method were used to investigate the transformation of valuable metals in roasting process,and the effect of each factor on the extractions of metals,and the parameters were optimized;The structure and properties of sodium aluminate were investigated;The separation of aluminum,iron and silicon was designed,and the high value-added corresponding product were prepared;The technical prototype and theoretical basis of the extractions of valuable metals were obtained,which could provide the theoretical basis and technical support to industrial manufacture.(1)The optimized conditions for the ammonium sulfate roasting to high-iron bauxite process are:roasting temperature of 450?,roasting time of 120 min,the ratio of ammonium sulfate to ore of 2.5:1,particle size of ore less than 80 ?m.Under the optimized process conditions,the extractions of aluminum and iron are all above 98%.(2)The optimized conditions for the leaching of aluminum and iron in the leaching process are:leaching temperature of 60?,leaching time of 60 min,stirring rate of 400 r·min-1,ratio of liquid-solid of 3:1.Under these conditions and the leaching rate of aluminum and iron are over 99%.(3)The sulfating reactions of aluminum and iron in the roasting process are controlled by internal diffusion,the apparent activation energies of there are 19.44 kJ·mol-1?20.43 kJ·mol-1,the kinetics equations of them are as follows:1+2(1-x)-3(1-x)2/3=0.05608exp(-19437/RT)t 1+2(1-x)-3(1-x)2/3=0.05635exp(-20426/RT)tThe leaching of aluminum and iron are controlled by external diffusion,the apparent activation energies are 6.28 kJ·mol-1?6.02 kJ·mol-1,the kinetics equations of them are as follows:1-(1-x)2/3=0.1441 exp(-6280/RT)t 1-(1-x)2/3=0.1366exp(-6020/RT)t(4)In a sodium aluminate solution(ak=1.50,alumina concentration of less than 100 g·L-1),aluminum mainly exists as Al(OH)4 form;but when the concentration of sodium aluminate is higher than 100 g·L-1,alumina not only exists as Al(OH)4,but also exists as a dimerization ions of Al-O-Al.When sodium aluminate solution having a molar ratio of 1.50 and an alumina concentration of 170 g·L-1,it has the largest concentration of aluminate ions in the form of Al(OH)4.With the increasing of alumina,the concentration of Al(OH)4 is decreased,and the dimer or polyaluminate ion concentration is increased.In the sodium aluminate solution,the alumina concentration and molar ratio determine the presence of the aluminate ion.When the molar ratio is 1.50 and the alumina concentration is from 0 to 41 g·L-1,the Tydal phenomenon of sodium aluminate solution is from weak to obvious;With the concentration of alumina continues to increase,and the Tyndall phenomenon of sodium aluminate solution become gradually not obvious.It is indicated that nanometer-scale particles exist in the dilute sodium aluminate solution,which is composed of Keggin ions.The sodium aluminate solution is an inorganic polymer solution.(5)The mechanism function in the roasting process calculated by Popescu method is g(a)=[1-(1-a)1/3]2(D3 model),its apparent activation energy is 175.123 kJ·mol-1,the pre-exponential factor is A=1.877×109?1.711×1010;But the apparent activation energy is 167.677 kJ·mol-1.(6)The hydrothermal extraction of hollow spherical aluminum hydroxide in the dehydration and diffusion process during calcination requires much lower activation energy than industrial aluminum hydroxide with aluminum hydroxide and lanthanum oxalate as raw materials,using high temperature solid phase reaction for synthesis of aluminum.The samples were characterized by SEM and XRD.Adding 2%AlCl3 or add 3%AlF3,solid phase grinding and mixing,calcination at 1200? constant temperature 3 h,it can obtain pure phase lanthanum aluminate powder.The addition of additives reduces the synthesis temperature of lanthanum aluminate.