Effect of l-glycine on bioleaching of collophanite by Acidithiobacillus ferrooxidans

Abstract

An acidophilic strain CK was isolated from an acid mine drainage of Yichang phosphorous ore in Hubei province, China. The cell morphology, physiological characteristics, and the 16S rDNA gene sequence analysis of this isolate showed that it could be identified and named as Acidithiobacillus ferrooxidans CK. The effect of amino acid l-glycine on the bioleaching of collophanite ores by A. ferrooxidans CK was investigated. With the addition of a certain amount of l-glycine to the leaching solution of collophanite, the bacterial affinity of strain CK for ferrous ions was improved, the microbial growth was accelerated, the pH value of solution was decreased and the fraction of phosphorous leached was increased by 14.66% compared to the normal process without this biochemical additive. The presence of l-glycine could significantly enhance the bacterial adsorption on the mineral surface.Scanning electron microscopy (SEM) observations of the mineral sample and leached residues showed during the process of bioleaching, brushite crystallites developed within the leached collophanite residues, which were intermixed with jarosite precipitates. These changes of mineral morphological features due to the exposure to bacteria could be also confirmed by X-ray diffraction (XRD) analyses of leached residues. It was shown by XRD and Elemental analyses of leached residues that the enhanced leaching of collophanite ores supplemented with l-glycine coincided with the declined formation of jarosite precipitates as a passivation layer on the mineral surface, due to Lower pH within the leaching culture by adding l-glycine.