Determination of aluminum oxide in copper concentrates by base melting and precipitation separation-EDTA titration

A basic melting and precipitation separation-EDTA titration method for the determination of aluminum oxide in copper concentrates was established.The samples were melted by sodium hydroxide and sodium peroxide,and most of the interfering elements were separated through precipitation.At certain pH,the elements including aluminum,zinc and tin ions reacted with excessive EDTA,and then pyrogallic acid was added to eliminate the interference of tin.By replacing Al-EDTA with fluoride salt,the obtained free EDTA were titrated with standard solution Zn(Ac)2.The content of aluminum oxide was thus calculated according to the consumption of standard solution Zn(Ac)2.The influencing factors were investigated,including selection and dosage of fluxes,melting time,water amount for leaching,dosage of buffer solution,precipitates absorption effect and impurities interferences.The optimal determination conditions were finally obtained.The method was applied to the analysis of sample,and it was found that the relative standard deviation(RSD) was in the range of 0.37%-0.85 % and the standard addition recovery was between 98.8%-99.0%.