Papers by Author: Sheng Mu Xiao

Abstract: Bacterial preoxidation of refractory gold ore has showed many advantages, such as lower operation cost and environmental friendly. In this paper, biooxidation of refractory gold ore by mixed moderate thermophiles culture in airlift bioreactor has been well studied. Firstly, a laboratory scale airlift bioreactor unit has been designed for bacterial preoxidation of refractory gold ore, a mixed moderate thermophilic culture was incubated. The orthogonal experiment was performed to investigate the effects of particle size, pulp density, aeration rate and initial pH. The results showed that when particle size 37micrometer，pulp density 5%，aeration rate 4 dm3•s-1 and initial pH 1.2, the arsenic leaching rate achieved to 93.5%. On the base of the airlift bioreactor unit, a continuous airlift bioreactor was designed. The preoxidation of refractory gold ore by a mixed culture of moderately thermophilic bacteria also was investigated in this equipment. The results showed that, under the conditions of pulp density 8% and stay time 60h, it can deal with 0.256 kg refractory gold ore per day, and the arsenic leaching rate can reach to 95.25%. During the experiment, some leaching liquor has been sampled from the second sect the fourth column of the continuous airlift bioreactor. The composition of microbial communities in this sample has been investigated using culture-independent 16S rDNA based cloning approach- restriction fragment length polymorphism. The phylogenetic analysis revealed that Leptospirillum ferriphilum and Acidithiobacillus caldus are the main organisms in this system. Both of them are moderate thermphilic bacteria and can resist relatively high concentration of arsenic ion.

Abstract: The composition of microbial communities in five acid mine water samples were studied, using culture-independent 16S rDNA based cloning and restriction fragment length polymorphism (RFLP) analysis. Phylogenetic analysis revealed that the bacteria in these five samples fell into 4 major groups: Proteobacteria, Nitrospira, Firmicutes and Bacteroidetes. Proteobacteria organisms such as A. ferrooxidans appeared in samples SX3, K1 and K2, but was scarce in samples SX1 and SX2; Nitrospira organisms Leptospirillum ferrooxidans, Leptospirillum ferriphilum and Leptospirillum group III, were prevalent in samples SX1, K1 and K2, but with fewer in samples SX2 and SX3. Archaea were only detected in samples K1 and K2 from the Tong shankou copper mine. Thermoplasma and Ferroplasma lineages were detected abundantly in these two samples. Meanwhile, the results of Principal Component Analysis (PCA) based on the percentages of OTUs and data of biogeochemical parameters, revealed that biogeochemical properties affected the diversity of microbial communities in mine water. The pH, temperature and different concentrations of elements such as S, Ni, Co and Cu seemed to be key factors resulting in the diverse distribution of microbes.