Considering the low average rainfall in the country and the importance of groundwater as a water supply source for drinking and agricultural water sections, water quality condition of groundwater must be controlled an...Considering the low average rainfall in the country and the importance of groundwater as a water supply source for drinking and agricultural water sections, water quality condition of groundwater must be controlled and prevented from any contamination. Identifying the vulnerable areas to pollution is one way of prevention. Many models have been offered for this purpose. In this study, a numerical rating scheme, called DRASTIC has been used for evaluating potential for groundwater pollution in pelly-mianrudan plain that is located in northern Lalli city in Khuzestan province. Resulted map obtained in GIS environment shows that the study area has DRASTIC index of 71-150 that is divided to five vulnerable zones namely no significance, very low, low, low to moderate, moderate to high. Maximum groundwater vulnerability correspondent low to medium zone that approximately covers 45 percentage of the study area and other parts on the northwest and center of the study area has high vulnerability. The sensitivity analysis showed that correlation DRASTIC index with net Recharge （0.68） and Impact of vadose zone media （0.63） parameters is more than other parameters in the study pelly-mianrudan area. The statistical analysis confirms that parameter soil media and topography are the most sensitive to contamination, followed in importance by parameters aquifer medium, vadose zone, recharge, hydraulic conductivity and depth to water.展开更多
The asymmetric reduction of β-keto esters to their corresponding hydroxy alcohols can be performed by employing homogeneous and heterogeneous chemo- and bio-catalysis. This review covers the scope and limitations of ...The asymmetric reduction of β-keto esters to their corresponding hydroxy alcohols can be performed by employing homogeneous and heterogeneous chemo- and bio-catalysis. This review covers the scope and limitations of different catalysts and methodologies that were employed for the reaction and compare between them on the basis of catalytic performance, product separation and catalyst recycling procedure. In general, heterogeneous catalytic systems are advantageous from industrial point of views as they can be easily separated by filtration and re-used. Nickel modified with tartaric acid and sodium bromide was found to be suitable heterogeneous catalyst for the enantioselective hydrogenation, yet its performance is lower than this of homogeneous chiral metal catalysts such as Ru-BINAP. Heterogenization of the chiral complex via immobilization or entrapment using organic and inorganic supports was thus tested. However, though the resulted heterogeneous analogues were highly enantioselective and could be re-used, the activity of the system is often very low compared to homogeneous system due to mass transfer limitations. Alternatively, performing liquid phase hydrogenation under homogeneous conditions, using Ru-BINAP soluble derivatives, yielded high activit5＇ and enantioselectivity. Product separation and catalysts recycling were facilitated by either extraction of the product with solvent that does not dissolve the complex or by selective filtration of the product. Alternatively, precipitation of the complex at the end of the reaction was also reported.展开更多
文摘Considering the low average rainfall in the country and the importance of groundwater as a water supply source for drinking and agricultural water sections, water quality condition of groundwater must be controlled and prevented from any contamination. Identifying the vulnerable areas to pollution is one way of prevention. Many models have been offered for this purpose. In this study, a numerical rating scheme, called DRASTIC has been used for evaluating potential for groundwater pollution in pelly-mianrudan plain that is located in northern Lalli city in Khuzestan province. Resulted map obtained in GIS environment shows that the study area has DRASTIC index of 71-150 that is divided to five vulnerable zones namely no significance, very low, low, low to moderate, moderate to high. Maximum groundwater vulnerability correspondent low to medium zone that approximately covers 45 percentage of the study area and other parts on the northwest and center of the study area has high vulnerability. The sensitivity analysis showed that correlation DRASTIC index with net Recharge （0.68） and Impact of vadose zone media （0.63） parameters is more than other parameters in the study pelly-mianrudan area. The statistical analysis confirms that parameter soil media and topography are the most sensitive to contamination, followed in importance by parameters aquifer medium, vadose zone, recharge, hydraulic conductivity and depth to water.
文摘The asymmetric reduction of β-keto esters to their corresponding hydroxy alcohols can be performed by employing homogeneous and heterogeneous chemo- and bio-catalysis. This review covers the scope and limitations of different catalysts and methodologies that were employed for the reaction and compare between them on the basis of catalytic performance, product separation and catalyst recycling procedure. In general, heterogeneous catalytic systems are advantageous from industrial point of views as they can be easily separated by filtration and re-used. Nickel modified with tartaric acid and sodium bromide was found to be suitable heterogeneous catalyst for the enantioselective hydrogenation, yet its performance is lower than this of homogeneous chiral metal catalysts such as Ru-BINAP. Heterogenization of the chiral complex via immobilization or entrapment using organic and inorganic supports was thus tested. However, though the resulted heterogeneous analogues were highly enantioselective and could be re-used, the activity of the system is often very low compared to homogeneous system due to mass transfer limitations. Alternatively, performing liquid phase hydrogenation under homogeneous conditions, using Ru-BINAP soluble derivatives, yielded high activit5＇ and enantioselectivity. Product separation and catalysts recycling were facilitated by either extraction of the product with solvent that does not dissolve the complex or by selective filtration of the product. Alternatively, precipitation of the complex at the end of the reaction was also reported.
