Partially hydrolyzed polyacrylamide （HPAM） has been widely used for water shut-off and profile control to enhance oil recovery. Herein, we reported a novel technique by which the crosslinking between HPAM and Cr3＋ ...Partially hydrolyzed polyacrylamide （HPAM） has been widely used for water shut-off and profile control to enhance oil recovery. Herein, we reported a novel technique by which the crosslinking between HPAM and Cr3＋ in aqueous solutions at 60 ℃ can be delayed effectively. Citric acid was selected as an organic complexing agent of Cr3＋ so that the crosslinking between HPAM and Cr3＋ can be prevented completely. Due to the decomposi- tion of the bicarbonate （HCO3-） embedded in solution, CO2 released from solution and the pH value of solution increased gradually. The degree of ionization of HPAM and its ability to complex with Cr3＋ increased accordingly. When the complexation of Cr3＋ with HPAM is stronger than that with citric acid, the viscosity of the HPAM solution increased signif- icantly. Under the closed condition, together with the existence of potassium dihydrogen phosphate （KH2PO4）, the release of CO2 was very slow and the condition was highly con- trolled so that the ionization of HPAM was prevented initially. Furthermore, the hydrogen bonding interactions between HPAM and melamine embedded in solution previously also postponed the ionization of HPAM. As a result, the crosslinking between HPAM and Cr3＋ can be delayed for almost one month, completely meeting the requirements for deep water shut-off and profile control to enhance oil recovery.展开更多
Crosslink polymerization kinetics of poly（acrylic acid-co-2-acrylamido-2-methylpropane sulfonic acid）,AA/AMPS hydrogels,was investigated by using dilatometry in the presence of sodium persulfate as initiator and N,N...Crosslink polymerization kinetics of poly（acrylic acid-co-2-acrylamido-2-methylpropane sulfonic acid）,AA/AMPS hydrogels,was investigated by using dilatometry in the presence of sodium persulfate as initiator and N,N＇-methylene bis（acrylamide） as crosslinker.It was found that the reaction for the crosslink polymerization of AA/AMPS hydrogels had orders of 0.58,1.14,and 0.86 with respect to the initiator,AMPS,and AA,respectively.From the Arrhenius plots,the activation energy of the crosslink polymerization was found to be about 140 and 89 kJ·mol-1 in the presence and absence of the crosslinker,respectively,in the temperature range from 45 to 65 °C.It was noted that the crosslinker had effects on the reaction order of the initiator and the activation energy due to the formation of cross-linked networks,which was verified by Fourier transfer infrared （FTIR） spectrum.To further confirm the influences of the cross-linked network structure on kinetic parameters of the crosslink polymerization,a mechanism was proposed,which highlights the different termination routes between free radical polymerization and crosslink polymerization.These results suggest that dilatometry provides a convenient tool for crosslink polymeri-zation study,and confirm that the cross-linked networks are formed in the crosslink polymerization.展开更多
Superabsorbents such as cross-linked PAM （polyacrylamides） are frequently used to increase water availability to plants. Commercial PAM providers suggest that besides its increasing water availability, PAMs also inc...Superabsorbents such as cross-linked PAM （polyacrylamides） are frequently used to increase water availability to plants. Commercial PAM providers suggest that besides its increasing water availability, PAMs also increase nutrient availability to plants. To test this premise, four application rates （0.0 g·kg^-1, 0.33 g·kg^-1, 1.66 g·kg^-1, 3.33 g·kg^-1 and 6.66 g·kg^-1） ofa PAM were mixed with sandy and loamy soils to evaluate its effect on nutrient leaching and retention in these soils. Miscible displacements of chloride were conducted on columns of PAM-soil mixtures and results were evaluated by an equilibrium CDE （convection dispersion equation） model. Increasing the PAM rates up to 1.66 g·kg^-1 resulted in increased early appearance and dispersive transport of chloride in sand. In addition, increasing the PAM rates gradually caused increased tailing of the breakthrough curves of chloride in both soils. These suggested that PAM increased preferential transport of chloride while it increased retention of chloride in soils. Effect of PAM on preferential transport and retardation of CI was greater in sand than loam.展开更多
The acrylamide level of some commercial bread assortments have been evaluated. The influence of several flour types on the content of acrylamide in 14 samples of bread, purchased from 5 different suppliers from the ma...The acrylamide level of some commercial bread assortments have been evaluated. The influence of several flour types on the content of acrylamide in 14 samples of bread, purchased from 5 different suppliers from the market in Bucharest, Romania was studied. For all bread assortments which have been analyzed for acrylamide, the International Commission of Illumination （CIELab） parameters, L＊, a＊ and b＊ have been also measured in an attempt to correlate the colour of the final product with its acrylamide content. Determination of acrylamide in bread samples was performed by Gas Chromatography coupled with tandem Mass Spectrometry （GC-MS/MS）, using isotope dillution calibration after derivatization （bromination）. The results revealed that the acrylamide level vary between bread assortments of different brands and bread assortments of same brand, but different lots. In the case of commercial bread samples, the use of whole wheat flours lead to formation of higher quantity in acrylamide （165.53 μg/kg）, compared to the use of white wheat flours （28.02μg/kg）.展开更多
MTs （Eiseniafoetida metallothioneins） have been recently reported as biomarkers for environmental metal contamination, however no study regarding Sb （antimony） is available. This study aimed to explore possibility...MTs （Eiseniafoetida metallothioneins） have been recently reported as biomarkers for environmental metal contamination, however no study regarding Sb （antimony） is available. This study aimed to explore possibility of MTs as a biomarker of Sb pollution. A contact method of filter paper was used to investigate Sb inducing MTs in Eiseniafoetida. Spectrophotometrical and SDS-PAGE （sodium dodecyl sulphate-polyacrylamide gel electropheresis） analyses were used to determine the nature of the induced MTs samples. Rabbit liver metallothioneins was used as a standard. The results showed that the molecular weight of induced protein was approximately 6-7 kDa. A characteristic absorption peak at 268 nm was observed, which was consistent with the standard. The amounts of Sb-MTs quantified by cadmium hemoglobin saturation method showed a significant positive relationship with increasing Sb exposure.The experiments prove that Sb can induce Sb-MTs in Eiseniafoetida as a biomarker of antimony pollution.展开更多
基金supported by the National Natural Science Foundation of China(No.51273189)the National Science and Technology Major Project of the Ministry of Science and Technology of China(No.2016ZX05016)the National Science and Technology Major Project of the Ministry of Science and Technology of China(No.2016ZX05046)
文摘Partially hydrolyzed polyacrylamide （HPAM） has been widely used for water shut-off and profile control to enhance oil recovery. Herein, we reported a novel technique by which the crosslinking between HPAM and Cr3＋ in aqueous solutions at 60 ℃ can be delayed effectively. Citric acid was selected as an organic complexing agent of Cr3＋ so that the crosslinking between HPAM and Cr3＋ can be prevented completely. Due to the decomposi- tion of the bicarbonate （HCO3-） embedded in solution, CO2 released from solution and the pH value of solution increased gradually. The degree of ionization of HPAM and its ability to complex with Cr3＋ increased accordingly. When the complexation of Cr3＋ with HPAM is stronger than that with citric acid, the viscosity of the HPAM solution increased signif- icantly. Under the closed condition, together with the existence of potassium dihydrogen phosphate （KH2PO4）, the release of CO2 was very slow and the condition was highly con- trolled so that the ionization of HPAM was prevented initially. Furthermore, the hydrogen bonding interactions between HPAM and melamine embedded in solution previously also postponed the ionization of HPAM. As a result, the crosslinking between HPAM and Cr3＋ can be delayed for almost one month, completely meeting the requirements for deep water shut-off and profile control to enhance oil recovery.
基金Supported by the National Natural Science Foundation of China（20176007 20376087）
文摘Crosslink polymerization kinetics of poly（acrylic acid-co-2-acrylamido-2-methylpropane sulfonic acid）,AA/AMPS hydrogels,was investigated by using dilatometry in the presence of sodium persulfate as initiator and N,N＇-methylene bis（acrylamide） as crosslinker.It was found that the reaction for the crosslink polymerization of AA/AMPS hydrogels had orders of 0.58,1.14,and 0.86 with respect to the initiator,AMPS,and AA,respectively.From the Arrhenius plots,the activation energy of the crosslink polymerization was found to be about 140 and 89 kJ·mol-1 in the presence and absence of the crosslinker,respectively,in the temperature range from 45 to 65 °C.It was noted that the crosslinker had effects on the reaction order of the initiator and the activation energy due to the formation of cross-linked networks,which was verified by Fourier transfer infrared （FTIR） spectrum.To further confirm the influences of the cross-linked network structure on kinetic parameters of the crosslink polymerization,a mechanism was proposed,which highlights the different termination routes between free radical polymerization and crosslink polymerization.These results suggest that dilatometry provides a convenient tool for crosslink polymeri-zation study,and confirm that the cross-linked networks are formed in the crosslink polymerization.
文摘Superabsorbents such as cross-linked PAM （polyacrylamides） are frequently used to increase water availability to plants. Commercial PAM providers suggest that besides its increasing water availability, PAMs also increase nutrient availability to plants. To test this premise, four application rates （0.0 g·kg^-1, 0.33 g·kg^-1, 1.66 g·kg^-1, 3.33 g·kg^-1 and 6.66 g·kg^-1） ofa PAM were mixed with sandy and loamy soils to evaluate its effect on nutrient leaching and retention in these soils. Miscible displacements of chloride were conducted on columns of PAM-soil mixtures and results were evaluated by an equilibrium CDE （convection dispersion equation） model. Increasing the PAM rates up to 1.66 g·kg^-1 resulted in increased early appearance and dispersive transport of chloride in sand. In addition, increasing the PAM rates gradually caused increased tailing of the breakthrough curves of chloride in both soils. These suggested that PAM increased preferential transport of chloride while it increased retention of chloride in soils. Effect of PAM on preferential transport and retardation of CI was greater in sand than loam.
文摘The acrylamide level of some commercial bread assortments have been evaluated. The influence of several flour types on the content of acrylamide in 14 samples of bread, purchased from 5 different suppliers from the market in Bucharest, Romania was studied. For all bread assortments which have been analyzed for acrylamide, the International Commission of Illumination （CIELab） parameters, L＊, a＊ and b＊ have been also measured in an attempt to correlate the colour of the final product with its acrylamide content. Determination of acrylamide in bread samples was performed by Gas Chromatography coupled with tandem Mass Spectrometry （GC-MS/MS）, using isotope dillution calibration after derivatization （bromination）. The results revealed that the acrylamide level vary between bread assortments of different brands and bread assortments of same brand, but different lots. In the case of commercial bread samples, the use of whole wheat flours lead to formation of higher quantity in acrylamide （165.53 μg/kg）, compared to the use of white wheat flours （28.02μg/kg）.
文摘MTs （Eiseniafoetida metallothioneins） have been recently reported as biomarkers for environmental metal contamination, however no study regarding Sb （antimony） is available. This study aimed to explore possibility of MTs as a biomarker of Sb pollution. A contact method of filter paper was used to investigate Sb inducing MTs in Eiseniafoetida. Spectrophotometrical and SDS-PAGE （sodium dodecyl sulphate-polyacrylamide gel electropheresis） analyses were used to determine the nature of the induced MTs samples. Rabbit liver metallothioneins was used as a standard. The results showed that the molecular weight of induced protein was approximately 6-7 kDa. A characteristic absorption peak at 268 nm was observed, which was consistent with the standard. The amounts of Sb-MTs quantified by cadmium hemoglobin saturation method showed a significant positive relationship with increasing Sb exposure.The experiments prove that Sb can induce Sb-MTs in Eiseniafoetida as a biomarker of antimony pollution.
