Characteristics of bio-desilication and bio-flotation of Paenibacillus mucilaginosus BM-4 on aluminosilicate minerals

Abstract

World reserves of bauxite include vast quantities of ore which are sub-economic due to high levels of reactive silica. It would lead to the substantial loss of caustic soda during Bayer processing. With the gradual reduction of the economic reserves of high-grade ore, people began to focus on the desiliconization treatment of the low-grade ore at reasonable cost. Biodesilication by silicate bacteria (such as Paenibacillus mucilaginosus) has been known as a potential technology for its characteristics of environmental protection, energy saving and sustainable development. In this paper, one silicate bacterial isolate with high desilication ability was screened, identified, and named as Paenibacillus mucilaginosus BM-4. The optimum cultural pH and temperature of BM-4 were also determined experimentally as 8.0 and 30 °C, respectively. Under these optimum cultural conditions, silicate ores were bioleached by BM-4. It seems that the stratified structures silicate ores, such as kaolinite and chlorite, were more readily to be leached by BM-4.

On the other hand, the float-abilities of BM-4 on kaolinite and bauxite were also investigated. With the experimental results shown that there existed the electrostatic adsorption process between BM-4 and kaolinite, and the Langmuir isotherm adsorption process between BM-4 and bauxite. It was observed that the float-abilities of bauxite were significantly depressed by BM-4, while the those of kaolinite were enhanced. The bioflotation test of the mixture of bauxite and kaolinite (mass ratio 5:1) through BM-4 were carried out by a modified Hallimond tube. With results shown that the Al/Si ratios of this mixed minerals were improved from 3.05 to 8.60 after bacterial conditioning due to bauxite depression. Eventually, 83.0% of Al₂O₃ were recovered from the mixed minerals by BM-4.