The application of the response surface methodology and the central composite design（CCD） technique for modeling and optimization of the influence of some operating variables on copper,molybdenum and rhenium recover...The application of the response surface methodology and the central composite design（CCD） technique for modeling and optimization of the influence of some operating variables on copper,molybdenum and rhenium recoveries in a bioleaching process was investigated.Three main bioleaching parameters,namely pH,solid concentration and inoculum percent,were changed during the bioleaching tests based on CCD.The ranges of the bioleaching process variables used in the design were as follows：pH1.46-2.14,solid concentration 0.95%-11.05%,and inoculum percent 1.59%-18.41%.A total of 20 bioleaching tests were carried out by the CCD method according to software-based designed matrix.Empirical model equations were developed according to the copper,molybdenum and rhenium recoveries obtained with these three parameters.Model equations of responses at the base of parameters were achieved by using statistical software.The model equations were then individually optimized by using quadratic programming to maximize copper,molybdenum and rhenium recoveries individually within the experimental range.The optimum conditions for copper recovery were pH 1.68,solid concentration 0.95% and the inoculum 18.41%（v/v）,while molybdenum and rhenium recoveries were 2.18% and 24.41%,respectively.The predicted values for copper,molybdenum and rhenium recoveries were found to be in good agreement with the experimental values.Also jarosite formation during bioleaching tests was also investigated.展开更多
Six strains of moderately thermophilic sulfur-oxidizing bacteria were isolated from several different typical environments in China. The identities of the isolates were confirmed by analyses of their 16S rRNA genes, a...Six strains of moderately thermophilic sulfur-oxidizing bacteria were isolated from several different typical environments in China. The identities of the isolates were confirmed by analyses of their 16S rRNA genes, and some key physiological traits. The isolates are Gram negative, rod-shaped bacteria, their optimal temperature and pH value for growth are 45-50℃ and 2.5-3.5 respectively. They are autotrophic and used elemental sulfur, sodium thiosulfate and potassium tetrathionate as electron donor, while a little glucose stimulated their growth. 16S rDNA sequences analysis reveals that the strains are phylogenetically clustered to Acidithiobacillus caldus.展开更多
A laboratory-scale experiment was carried out to assess the influence of temperature fluctuation on thermophilic anaerobic digestion of municipal organic solid waste （MOSW）. Heating failure was simulated by decreasi...A laboratory-scale experiment was carried out to assess the influence of temperature fluctuation on thermophilic anaerobic digestion of municipal organic solid waste （MOSW）. Heating failure was simulated by decreasing temperature suddenly from 55 ℃ to 20 ℃ suddenly, 2 h time is needed for temperature decrease and recovery. Under the conditions of 8.0 g/（L·d） and 15 d respectively for MOSW load and retention time, following results were noted： （1） biogas production almost stopped and VFA （volatile fatty acid） accumulated rapidly, accompanied by pH decrease; （2） with low temperature （20 ℃） duration of 1, 5, 12 and 24 h, it took 3, 11, 56 and 72 h for the thermophilic anaerobic digestion system to reproduce methane after temperature fluctuation, （3） the longer the low temperature interval lasted, the more the methanogenic bacteria would decay, hydrolysis, acidification and methanogenesis were all influenced by temperature fluctuation： （4） the thermophilic microorganisms were highly resilient to temperature fluctuation.展开更多
基金supported by the National Iranian Copper Industry Co. and Geological Survey of Iran
文摘The application of the response surface methodology and the central composite design（CCD） technique for modeling and optimization of the influence of some operating variables on copper,molybdenum and rhenium recoveries in a bioleaching process was investigated.Three main bioleaching parameters,namely pH,solid concentration and inoculum percent,were changed during the bioleaching tests based on CCD.The ranges of the bioleaching process variables used in the design were as follows：pH1.46-2.14,solid concentration 0.95%-11.05%,and inoculum percent 1.59%-18.41%.A total of 20 bioleaching tests were carried out by the CCD method according to software-based designed matrix.Empirical model equations were developed according to the copper,molybdenum and rhenium recoveries obtained with these three parameters.Model equations of responses at the base of parameters were achieved by using statistical software.The model equations were then individually optimized by using quadratic programming to maximize copper,molybdenum and rhenium recoveries individually within the experimental range.The optimum conditions for copper recovery were pH 1.68,solid concentration 0.95% and the inoculum 18.41%（v/v）,while molybdenum and rhenium recoveries were 2.18% and 24.41%,respectively.The predicted values for copper,molybdenum and rhenium recoveries were found to be in good agreement with the experimental values.Also jarosite formation during bioleaching tests was also investigated.
基金Project (50321402) supported by the National Natural Science Foundation of China Project(2004CB619204) supported by the State Basic Research Development Program of China Project (DY105-02-04-05) supported by the China Ocean Mineral Resources Research and Development Association
文摘Six strains of moderately thermophilic sulfur-oxidizing bacteria were isolated from several different typical environments in China. The identities of the isolates were confirmed by analyses of their 16S rRNA genes, and some key physiological traits. The isolates are Gram negative, rod-shaped bacteria, their optimal temperature and pH value for growth are 45-50℃ and 2.5-3.5 respectively. They are autotrophic and used elemental sulfur, sodium thiosulfate and potassium tetrathionate as electron donor, while a little glucose stimulated their growth. 16S rDNA sequences analysis reveals that the strains are phylogenetically clustered to Acidithiobacillus caldus.
基金Project (No. 2002-548) supported by the National Development andReform Commission of China
文摘A laboratory-scale experiment was carried out to assess the influence of temperature fluctuation on thermophilic anaerobic digestion of municipal organic solid waste （MOSW）. Heating failure was simulated by decreasing temperature suddenly from 55 ℃ to 20 ℃ suddenly, 2 h time is needed for temperature decrease and recovery. Under the conditions of 8.0 g/（L·d） and 15 d respectively for MOSW load and retention time, following results were noted： （1） biogas production almost stopped and VFA （volatile fatty acid） accumulated rapidly, accompanied by pH decrease; （2） with low temperature （20 ℃） duration of 1, 5, 12 and 24 h, it took 3, 11, 56 and 72 h for the thermophilic anaerobic digestion system to reproduce methane after temperature fluctuation, （3） the longer the low temperature interval lasted, the more the methanogenic bacteria would decay, hydrolysis, acidification and methanogenesis were all influenced by temperature fluctuation： （4） the thermophilic microorganisms were highly resilient to temperature fluctuation.
