Study On Deep Processing Of Chromite-the Synthetic Section Of Sprayed Chromium Oxide?Cr₂O₃?

Chromite,an important strategic resource,has less resource reserves of per capita in our country.It belongs to the scope of scarce resources.The different qualities of chromite would be obtained after mining and screening.This is the upstream process of the whole chromite to chromium?III?oxide process.The chromite is treated by the chrome salt process,then a variety of chromium salts can be obtained.This is the midstream process of the whole chromite to chromium?III?oxide process.The chromium?III?oxide can be obtained after processing the chrome salt.This is the downstream process of the whole chromite to chromium?III?oxide process.Chromium,an indispensable strategic resource,has an irreplaceable application in the economy.So how to make full use of the existing chromite resourous to create higher added value has become a research focus.At present,some reserach had been made to get high value-added aprayed chromium?III?oxide in the chromite downstream section.Based on the previous literature reports and the previous research results of ourself group,new processes to prepare aprayed chromium?III?oxide had been studied via using the other chromium salts as the chrome source instead of potassium dichromate via hydrometallurgy method in this paper.The process has the advantages of cost saving,easy to operate,environment friendly and so on.The research that uses a variety of different chromium salts to prepare sprayed chromium?III?oxide can get rid of the unchangeable raw material.It has important significance for reducing the manufacturing cost and improving production flexibility.Based on the preliminary work of our group,the new synthetic section that high value-added products —— sprayed chromium???oxide?Cr₂O₃?had been studied in this paper.The main progress and innovation of this paper are listed as follows:1.The process conditions to prepare large-sized sprayed chromium?III?oxide via hydrometallurgical process?hydrothermal process?had been studied under the system of sodium dichromate.The anhydrous ethanol is used as the reductant and the citric acid is used as the surfactant.The morphologies and compositions of the results are investigated via XRD and SEM.The effects of the influencing factors such as citric acid,ethanol,reaction temperature,sodium dichromate and reaction substrate on the morphologies had been studied.The results show that when the sodium dichromate is0.5 g,the citric acid is 0.1 g and the ethanol is 3 ml,the best results would be obtained after reacting at 180 oC for 1 hour.The morphologies of the obtained products are the best.The results are consisted of three-dimensional sphered-like particles without any agglomerates and nanoparticles.The surface of the particle is clean and smooth.The particle sizes range from 25 to 130 ?m with an average size of 61?m.The particle sizes of the 80% of the particles are between 40 to 90 ?m.It can be indicated that the particle sizes are uniform and the particles have a narrower particle sizes distribution.The particle sizes distribution can meet the standard of the spraying chromium?III?oxide particle size;2.The process conditions to prepare large-sized sprayed chromium?III?oxide via hydrometallurgical process?hydrothermal process?had been studied under the system of sodium chromate.The anhydrous ethanol is used as the reductant and the citric acid is used as the surfactant.The large-sized sprayed chromium?III?oxide had been successfully obtained with the chromate the first time.The morphologies and compositions of the results obtained under the sodium chromate system are investigated via XRD and SEM.The effects of the influencing factors such as citric acid,ethanol,reaction temperature,sodium chromate and reaction substrate on the morphologies had been studied.The results show that when the sodium dichromate is 0.5 g,the citric acid is 0.24 g and the ethanol is 3 ml,the best results had been obtained after reaction at220 oC for 1 hour.The morphologies of the obtained products are the best.The particles are all three-dimensional sphered-like.And the surface of the particle is clean and smooth without any fissures.The particle sizes range from 30 to 130 ?m with an average size of 70 ?m.The particle sizes of the 85% of the particles are between 40 to100 ?m.It can be indicated that the particle sizes are uniform and the particles have a narrower particle size distribution.The particle sizes distribution can meet the standard of the spraying chromium?III?oxide particle size;3.The process conditions to prepare large-sized sprayed chromium?III?oxide via hydrometallurgical process?hydrothermal process?had been studied under the system of potassium chromate.The anhydrous ethanol is used as the reductant and the citric acid is used as the surfactant.The morphologies and compositions of the results are investigated via XRD and SEM.The effects of the influencing factors such as citric acid,ethanol,reaction temperature,potassium chromate and reaction substrate on the morphologies had been studied.The results show that when the potassium chromate is0.5 g,the citric acid is 0.21 g and the ethanol is 3 ml,the best results had been obtainedafter reaction at 220 oC for 1 hour.The morphologies of the obtained products are the best.The results are all three-dimensional sphered-like large-sized particles.The particle sizes range from 30 to 190 ?m with an average size of 85 ?m.The particle sizes of the80% of the particles are between 30 to 120 ?m.It can be indicated that the particle sizes are relatively uniform and the particles have a narrow particle size distribution.The particle sizes distribution also can meet the standard of the spraying chromium?III?oxide particle size;The suitable conditions to prepare large-sized sprayed chromium?III?oxide are obtained after the research on three different chrome salt systems.This provides a varity of options for the synthetic raw materials of high value-added sprayed chromium?III?oxide in the downstream section.The sources of raw materials are more extensive.The suitable chromium salt can be selected to prepare large-sized sprayed chromium?III?oxide according to the cost and the required product specifications.This greatly enhances the competitiveness of the product.