Determination of Available Alumina, Active Alumina and Active Silicon in Gibbsite Bauxite by Inductively Coupled Plasma-Optical Emission Spectrometry with Microwave Digestion

Available alumina and active silicon in gibbsite bauxite are important indicators for the quality of bauxite. These two components are commonly determined by Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES). In this method, available alumina in solution after digestion is determined first and active silicon is then determined after acid dissolution of the residue. However, because the solution is not easy to determine, and the residue cannot be digested completely, the results have poor reproducibility. By heating and acidifying the solution and taking Co as the internal standard, the conventional method can be improved upon. Active alumina and active silicon were simultaneously determined by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS), and available alumina was quantified indirectly by calculation. The method precision (RSD) is greater than 3% (n=13) and the recoveries range from 97.0% to 102.6%. The results of international standard materials are consistent with the certified values. The proposed method solves the issues of the conventional method and improves the influence of the matrix effect and equipment drift on analytical results. This method can determine simultaneously active alumina and active silicon. The concept of active alumina can be used to comprehensively evaluate gibbsite bauxite and the adjustment of the production method of aluminum oxide.