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Chandra Sekhar Gahan,Dong Jin Kim,Chandrika Akilan,Seo-Yun Choi,Byoung Gon Kim 한국화학공학회 2013 Korean Journal of Chemical Engineering Vol.30 No.3
Shake flask studies on microbial desulfurization of three different coal samples (Indonesian lignite, Chinese lignite and Korean anthracite) were performed to optimize the best suitable growth medium. Among the three different growth mediums (basal salt medium, basal salt medium supplemented with 9 g/L Fe and basal salt medium supplemented with 2.5% S0) tested, the basal salt medium was found to be the best, considering process dynamics and economical factors. The extent of pyrite oxidation was highest with 95% in the experiments with Korean anthracite in basal salt medium supplemented with 9 g/L Fe, while the lowest pyrite oxidation of 70-71% was observed in the experiments with Indonesian and Chinese Lignite’s in only basal salt medium. The microbial sulfur removal in the experiments with basal salt medium supplemented with 9 g/L Fe for all the three coal samples was between 94-97%, while the experiments on basal salt medium supplemented with 2.5% S0 for all the coal samples were relatively much lower ranging between 27-48%. However, the overall study resulted with promising directions for further scaling up of microbial desulphurization in a best growth medium devoid of iron and sulfur supplement.
Chandra Sekhar Gahan,Haragobinda Srichandan,김동진,Sradhanjali Singh,Seoung-Won Lee 한국화학공학회 2013 Korean Journal of Chemical Engineering Vol.30 No.5
Microbial leaching of a petroleum spent catalyst was carried out using mixed mesophilic iron and sulfur oxidizing acidophiles. Bench-scale batch stirred tank reactors with a working volume of 1 L were used in this study at 35 oC. The pulp density considered for the study was 10% (w/v), while the particle size of the spent catalyst was varied by 45-106, 106-212 and >212 μm. The leaching percentage of Ni from the spent catalyst was found to be highest (97-98%) with varying particle size. However, the leaching yield for rest of the metals like Al, Fe, V and Mo was 70-74%, 66-85%, 33-43% and 22-45%, respectively. Influence of particle size was predominant on the recovery of all metals except Ni. Assessment of the generation of the bioleach residue after bioleaching showed a weight loss of 54-62% due to the dissolution of the metal values from the spent catalyst. The mineralogical study conducted by X-ray diffraction and scanning electron microscopy supports the dissolution of metals from the spent catalyst. Jarosite mineral phase was the dominant mineral phase in the bioleach residue due to the dissolution of the oxidic and sulfidic mineral phases present in the feed spent catalyst.
( Debabrata Pradhan ),( Dong Jin Kim ),( Jong Gwan Ahn ),( Chandra Sekhar Gahan ),( Hun Saeng Chung ),( Seoung Won Lee ) 대한금속재료학회(구 대한금속학회) 2011 대한금속·재료학회지 Vol.49 No.12
Bioleaching studies of metals from a spent catalyst were conducted using both adapted and unadapted bacterial cultures. The bacterium used in this experiment was Acidithiobacillus ferrooxidans. A comparison of the kinetics of leaching was made between the two cultures by varying the leaching parameters, including the pulp density, particle size and temperature. Both cultures showed similar effects with respect to the above parameters, but the leaching rates of all metals were higher with the adapted compared to the unadapted bacterial cultures. The leaching reactions were continued for 240 h in the case of the unadapted bacterial culture, but only for 40 h in the case of the adapted bacterial culture. The leaching reactions followed first order kinetics. In addition, the kinetics of leaching was concluded to be a diffusion control model; therefore, the product layers were impervious.