Ⅱ,X型胶原对钙磷酸盐生物矿化动力学的影响

为探讨软骨基质成分Ⅱ,X型胶原在软骨内成骨过程中可能起的作用,研究了在Ⅱ或X型胶原存在下,以骨基质Ⅰ型胶原为晶种时钙磷酸盐晶体生长的动力学过程。用FT-IR方法分析了固相产物羟基磷灰石(HAP)。结果表明:Ⅱ或X型胶原的存在对钙磷酸盐在Ⅰ型胶原表面的生长速率有抑制作用,X型胶原的抑制作用大于Ⅱ型胶原。在Ⅱ型胶原存在下,测得其反应级数为4。说明软骨基质Ⅱ,X型胶原在软骨内成骨这一生物矿化过程中可能起积累钙离子的作用,对结晶生长机理与矿化产物无影响。

Enhancing recovery of uranium column bioleaching by process optimization and kinetic modeling

This research aimed to enhance the column bioleaching recovery of uranium ore by Acidithiobacillus ferrooxidans.Seven factors were examined for their significance on bioleaching using a Plackett-Burman factorial design.Four significant variables([Fe2+]initial,pH,aeration rate and inoculation percent)were selected for the optimization studies.The effect of these variables on uranium bioleaching was studied using a central composite design(CCD).The optimal values of the variables for the maximum uranium bioleaching recovery(90.27±0.98)%were as follows:[Fe2+]initial=2.89g/L,aeration rate420mL/min,pH1.45and inoculation6%(v/v).[Fe2+]initial was found to be the most effective parameter.The maximum uranium recovery from the predicted models was92.01%.This value was in agreement with the actual experimental value.The analysis of bioleaching residue of uranium ore under optimum conditions confirmed the formation of K-jarosite on the surface of minerals.By using optimal conditions,uranium bioleaching recovery is increased at column and jarosite precipitation is minimized.The kinetic model showed that uranium recovery has a direct relation with ferric ion concentration.

Microbial oxidation of refractory gold sulfide concentrate by a native consortium

A defined mesophilic consortium including an iron oxidizing bacterium and a sulfur oxidizing bacterium was constructed to evaluate its ability for bioleaching a flotation concentrate from Andacollo mine in Neuquén,Argentina.Experiments were performed in shake flasks with a pulp density of10%(w/v),using a basal salt medium containing ferrous iron at pH1.8.The leaching solutions were analyzed for pH,redox potential(using specifics electrodes),ferrous iron(by UV-Vis spectrophotometry)and metal concentrations(by atomic absorption spectroscopy).The results showed that the consortium was able to reduce the refractory behavior of the concentrate,allowing91.6%of gold recovery;at the same time,high dissolution of copper and zinc was reached.These dissolutions followed a shrinking core kinetic model.According to this model,the copper solubilization was controlled by diffusion through a product layer(mainly jarosite),while zinc dissolution did not show a defined control step.This designed consortium,composed of bacterial strains with specific physiological abilities,could be useful not only to optimize gold recovery but also to decrease the leachates metallic charge,which would be an environmental advantage.

Effect of As(Ⅲ)on kinetics of Fe^(2+)bio-oxidation

Fe^(2+) bio-oxidation influenced by toxic metal ions released from the dissolution of arsenic-bearing gold ores was investigated.Fe^(2+) bio-oxidation by moderately thermophilic microorganisms was studied under different initial concentrations of Fe^(2+) and As(Ⅲ),and Monod equation was used to fit the Fe^(2+) bio-oxidation under different conditions.Results showed that the Fe^(2+) bio-oxidation rate increased as the initial Fe^(2+) concentration increased until it reached 12 g/L.As(Ⅲ)severely inhibited Fe^(2+) bio-oxidation.When the As(Ⅲ)concentration was 8 g/L,9 g/L Fe^(2+) was more than 200 h.The Monod equation fitted the Fe^(2+) bio-oxidation well.In the absence of As(Ⅲ),the maximum specific growth rate of the culture and the substrate affinity constant were 0.142 h^(−1) and 0.053 g/L,respectively.As(Ⅲ)inhibited Fe^(2+) bio-oxidation via competitive inhibition,and the inhibition constant was 0.0035 g/L.

Biochar:An Emerging Panacea for Remediation of Soil Contaminants from Mining,Industry and Sewage Wastes

Mine tailings, waste rock piles, acid mine drainage, industrial wastewater, and sewage sludge have contaminated a vast area of cultivable and fallow lands, with a consequence of deterioration of soil and water quality and watercourses due to the erosion of contaminated soils for absence of vegetative cover. High concentrations of toxic elements, organic contaminants, acidic soils, and harsh climatic conditions have made it difficult to re-establish vegetation and produce crops there. Recently, a significant body of work has focussed on the suitability and potentiality of biochar as a soil remediation tool that increases seed emergence, soil and crop productivity, above ground biomass, and vegetation cover on mine tailings, waste rock piles, and industrial and sewage waste- contaminated soils by increasing soil nutrients and water-holding capacity, amelioration of soil acidity, and stimulation of microbial diversity and functions. This review addresses： i） the functional properties of biochar, and microbial cycling of nutrients in soil; ii） bioremediation, especially phytoremediation of mine railings, industrial waste, sewage sludge, and contaminated soil using biochar; iii） impact of biochar on reduction of acid production, acid mine drainage treatment, and geochemical dynamics in mine railings; and iv） treatment of metal and organic contaminants in soils using biochar, and restoration of degraded land.