Abstract

In this investigation the biological leaching of aluminum by isolated fungi from low grade bauxite (<50% Al₂O₃.) was studied. X-ray diffraction investigation indicated that silicate and aluminosillicate minerals were major mineral composition. Wet chemical and electron disperse X-ray analysis showed the presence of aluminum, iron, silica and titanium. Biological leaching tests were carried out using indigenous specimen fungi,Aspergillus niger and Penicillium notatum. Savored dextrose chloram-phenicol agar (SDA) was used as medium for the selected fungi.  All microorganisms were tested for acid-production and leaching capabilities of aluminum from low grad bauxite. Leaching experiments were performed in 250-ml Erlenmeyer flasks at 28°C and at 150 rpm agitation under aseptic conditions. Pry heating of bauxite and its effect on leaching process was studied. Indigenous specimen fungi were the most efficient of the fungal cultures; 7080 mg of Al₂O₃/l was solubilized at 15% pulp density of bauxite. The metal content of leaching solution was determined by using wet chemical and atomic absorption spectrophotometer.

Key words: Bioleaching, low grade bauxite, organic acids, Aspergillus niger, Penicillium