Determination of alumina actual dissolution rate in diaspore type bauxite from Sanmenxia area by inductively coupled plasma atomic emission spectrometry with sodium hydroxide dissolution
Dissolution rate is an important index for measuring the quality of diaspore type bauxite.Usual-ly,when calculating Al2O3 actual dissolution rate,since the mother solution used to dissolve Al2O3 in bauxite contains a large amount of Al2O3,it is necessary to first filter,wash and dry the test solution after dissolving Al2O3 to obtain red mud,and then determine the content of Al2O3 in red mud after digestion to obtain the final result after conversion.The operation is more complicated.The high-pressure digestion technology was used to simulate high-temperature Bayer alumina production process.NaOH solution with the same concentration as the production process was used to replace the mother solution in the production process to dissolve Al2O3 in the bauxite.The content of Al2O3 in solution was determined by inductively coupled plasma atomic emission spectrometry(ICP-AES).Therefore,the content of soluble Al2O3 could be directly determined.Then,Al2O3 actual dissolution rate could be calculated through dividing soluble Al2O3 content by the total content of Al2O3.Consequently,a method for determination of Al2O3 actual dissolution rate in diaspore type bauxite from Sanmenxia area was established.Under the selected condi-tions,the mass concentration of Al2O3 in range of 10-100 μg/mL had a linear relationship with its corre-sponding emission intensity.The correlation coefficient of calibration curve linear equation was 0.999 9.The detection limit of this method was 0.04％.The soluble Al2O3 content and Al2O3 actual dissolution rate in diaspore type bauxite samples were determined according to the proposed method.The relative standard deviation(RSD,n=6)of determination results for soluble Al2O3 were between 0.67％and 0.92％.The Al2O3 actual dissolution rates were in range of 68.51％-84.14％.The contents of soluble Al2O3 in diaspore type bauxite samples were determined according to the proposed method and other meth-od(the contents of Al2O3 in red mud were first determined,and the contents of soluble Al2O3 were then calculated by subtraction method),and the Al2O3 actual dissolution rates were calculated.The results of the two above methods were consistent.
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