Preparation of industrial alumina from a biotite-rich kaolinite (BRK) ore by Cyanex®272

Abstract

ABSTRACTThe purification of Al(III) to alumina by bis(2,4,4-trimethylpentyl)phosphinic acid commonly called Cyanex®272 in kerosene diluent from aqueous aluminium leach liquor was investigated. The influences of parameters such as equilibrium pH and extractant concentration on the extent of Al(III) extraction were accordingly examined. After appropriate optimisation, an extraction efficiency of 98.6% Al(III) by 0.25 mol/L Cyanex®272 in kerosene diluent at 27 ± 2°C in the equilibrium pH range of 3.0–3.5 was achieved from an initial biotite-rich kaolinite leach liquor containing 1864.7 mg/L Al, 123.4 mg/L Fe, 70 mg/L Mn and 17.6 mg/L Ti as a major constituents. Other metal ion species detected including Ca and Mg was found to occur from low to trace amounts (≤1 mg/L). Total stripping of Al(III) from the loaded organic phase was carried out using 0.1 mol/L H2SO4 solution at an aqueous: organic (A:O) phase ratio 1: 1. The thermodynamic feasibility of extraction process to obtain high-grade alumina (Al2O3: 14-387-9021, melting point = 2056°C) gave the apparent standard enthalpy (ΔH), entropy (ΔS) and Gibb’s energy (ΔG) of 3.87 kJ/mol, 10.57 J/K mol and −3177.6 J/mol respectively at 27 ± 2°C.