Beneficiation of fine Weipa bauxite tailing

Abstract

Two types of Bauxite are mined in Weipa, Northern Queensland, and are designated as Andoom and Weipa ores depending on the deposit. To improve the grade of these ores washing is usually done which results in a lot of the constituent siliceous material being washed away. The resultant bauxite product then achieves a grade of about 60% Alumina with about 5% Silica. In this beneficiation processs, the fine bauxite fraction of the ore is washed away together with the siliceous material as tailing, and this accounts for about 20 to 25 percent of the mined bauxite in any particular period.This study focussed on the recovery of the bauxite tailing with special attention given to the recovery of the fine fraction (plus 10 minus 120 //-m ) of the tailing since the recovery of the coarse fraction has been investigated in previous work.A preliminary study of the beneficiation process involved the determination of the chemical and mineralogical composition of the fine tailing fraction. Rheological characterization was performed on the Andoom fine tailing to explain the behaviour of the flocculated and dispersed state of the pulp. Selective flocculation-desliming tests were considered but not persued beyond preliminary tests. Selective flotation of quartz was undertaken as the most feasible means of upgrading the fine tailing fraction. Two amine collectors were tested, hexylammonium acetate with a short hydrocarbon chain, and dodecylammonium acetate with a medium hydrocarbon chain.Controlled-dispersion froth flotation was given a thorough investigation using sodium hexametaphosphate as the pulp dispersant and dodecylammonium acetate (DAA) as the most promising collector for quartz in this test. Conditions were determined at which quartz concentrate of 81.7% with a recovery of 91.0% .was achieved. The beneficiated fine tailing contained 57.5% AI2O3 with total silica content of about 5%, which was basically in the combined form. A recommended flowsheet for pilot plant trials was established on the basis of these results, and this was an integration of both the treatment of coarse and fine fractions of the bauxite tailing. A recommendation for further investigation involving the recovery of Rutile and Zircon which tend to concentrate in the flotation tailing was given.jec