Drying kinetics for alcohol-soaked type-A zeolite(pore size 0.5 nm)was determined at 50°C for 12 small-molecule alcohols(from C1 to C10).The second-phase of drying of wet porous materials reports on the mass-tran...Drying kinetics for alcohol-soaked type-A zeolite(pore size 0.5 nm)was determined at 50°C for 12 small-molecule alcohols(from C1 to C10).The second-phase of drying of wet porous materials reports on the mass-transfer characteristics within the solid matrices.This stage follows pseudo first-order kinetics(k1),and the second-order rate constant k2=k1/(fluxional area)was found to correlate with the surface tension of the liquids imbibing the solid matrix(p<0.002).k2 values decrease along the homologous linear alcohols,and branched-chain alcohols diffuse faster than their linear analogues due to their lower surface tensions.No independent contribution was found from the molecular size of the alcohols in the experiment reported here.Characteristic velocity and enthalpy of vaporisation of the liquids were not found to be significant independent variables,either.The find agrees with the notion that liquid movement in pores is governed during the drying processes by the liquid chemical potential gradient between the pore space and gas phase above the porous particle surfaces,this gradient being a function of the molecular cohesion of the moving liquid front(surface tension,g).The results can be expressed by the linear Gibbs-energy relation log(k2/s^(-1)·m^(-2))=(2.5±0.5)-(1.6±0.2)×10^(2)(g/J·m^(-2)).展开更多
The chars in the natural environment can affect the migration of polybrominated diphenyl ethers(PBDEs). However, there is insufficient research relating to the adsorption behavior and mechanisms of PBDEs on biochars. ...The chars in the natural environment can affect the migration of polybrominated diphenyl ethers(PBDEs). However, there is insufficient research relating to the adsorption behavior and mechanisms of PBDEs on biochars. This study examined the adsorption kinetics of 2,2′,4,4′-tetrabromodiphenyl ether(BDE-47) on maize straw-derived biochars(MSBCs) pyrolyzed at four different temperatures via batch experiments. The biochar samples were characterized using Fourier transform infrared(FTIR) spectroscopy,Raman spectra, and elemental analysis. A two-compartment first-order model and pseudo-second-order model exhibited a better fit compared to a pseudo-first-order model in describing the BDE-47 adsorption on biochars, which was dominated by a slow adsorption compartment and chemisorption. The MSBC pyrolyzed at 600 °C had the highest BDE-47 adsorption capacity owing to its relatively large specific surface area and relatively high aromaticity compared with the other three MSBCs pyrolyzed at 300, 400, and 500 ℃.However, there was no significant difference in adsorption capacity among the other three biochars. The organic functional groups coupled with the graphene structures of biochars and the hydrophobic effect of the functional groups promoted the adsorption of BDE-47. Pore diffusion was not the sole rate-limiting step;film diffusion was also involved in the adsorption process of BDE-47 on biochars. The overall results demonstrate the transport and potential treatment of PBDEs using biochars.展开更多
The Three Gorges Reservoir is a good site for the further researches on reservoir induced seismicity due to decades＇ seismic monitoring. After the first water impounding in 2003, seismic activity becomes more frequen...The Three Gorges Reservoir is a good site for the further researches on reservoir induced seismicity due to decades＇ seismic monitoring. After the first water impounding in 2003, seismic activity becomes more frequent than that before water impoundment. In order to quantitatively study, the relationship between the water level fluctuation and earthquakes in TGR, we introduced statistical methods to attain the goal. First of all, we relocated the earthquakes in TGR region with double difference method and divided the earthquakes into 5 clusters with clustering analysis method. Secondly, to examine the impacts of water level fluctuation in different water filling stages on the seismic activity in the 5 clusters, a series of statistical analyses are applied. Pearson correlation results show that only the 175 m water level fluc- tuation has significantly positive impacts on the seismic activity in clusters I, II, III and V with correlation coefficients of 0.44, 0.38, 0.66 and 0.63. Cross-correlation analysis demonstrates that 0, ], 0 and 0 month time delay separately for the clusters I, II, III and V exists. It illustrated the influences of the water loading and pore pressure diffusion on induced earthquakes. Cointegration tests and impulse response analysis denoted that the 175 m water level only had long term and significant effects just on the seismic events in the intersection region of the Fairy Mount Fault and Nine-brook Fault. One standard deviation shock to 175 m water level increased the seismic activity in cluster V for the first 3 months, and then the negative influence was shown. After 7 months, the negative impulse response becomes stable. The long-term effect of the 175 m water impoundment also proved the important role of pore pressure diffusion in RIS with time.展开更多
815 earthquakes recorded by 12 seismic stations of the Zipingpu reservoir seismic network in 2009 were relocated using the double difference algorithm to analyze the seismic activity of the Zipingpu reservoir.Relocati...815 earthquakes recorded by 12 seismic stations of the Zipingpu reservoir seismic network in 2009 were relocated using the double difference algorithm to analyze the seismic activity of the Zipingpu reservoir.Relocation results show that the earthquakes are concentrated relatively in three zones.The distribution characteristics of focal depth are obviously different among different concentration zones.This means earthquakes in different concentration zones may have different causes.Compared to relocation of earthquakes taking place before the Wenchuan earthquake done by other researchers,the seismic concentration zones in the reservoir area shifted obviously after the Wenchuan earthquake.These variations are related to local stress adjustment in the reservoir area and may also be related to the diffusion depth and range of increased pore pressure caused by rock failure in the course of Wenchuan earthquake.展开更多
The study has analyzed the relationship between the water-drainage sluice process of reservoir, stress triggers and shadows of earthquake and porosity variability of fault slip zone. First, the pore pressure, pressure...The study has analyzed the relationship between the water-drainage sluice process of reservoir, stress triggers and shadows of earthquake and porosity variability of fault slip zone. First, the pore pressure, pressure gradient, viscous stress and Reynolds stress to reservoir-earthquake fault slip problem are analyzed, and these are un-negligible factors of the extended coulomb failure stress under ultra-high temperature and pressure condition. Second, the porosity tensor and permeability tensor are studied, the relationship between Zipingpu reservoir and Longmenshan slip has been analyzed, and the extended viscous stress and Reynolds stress as function of time and infiltration process are obtained. Last, some primary conclusions about the flow-solid coupled facture mechanism to the Zipingpu reservoir and Longmenshan slip problem are presented, which can help understand the flow-solid coupled facture mechanism of reservoir-coseismic fault slip problem.展开更多
Pore network,pore connectivity,and the resulting effective adsorbate pore diffusivity within an adsorbent are critical physical considerations in mass transport modeling of aqueous adsorption.Tied to these three adsor...Pore network,pore connectivity,and the resulting effective adsorbate pore diffusivity within an adsorbent are critical physical considerations in mass transport modeling of aqueous adsorption.Tied to these three adsorbent features are the adsorbent tortuosity and tortuosity factor concepts.These concepts encompass the collective hindrance to intra-adsorbent adsorbate transport arising because of a disorderly adsorbent porous topology.It is crucial for materials scientists,chemists,chemical engineers,and water treatment specialists to understand the complex and variable connections among adsorbate chemistry,adsorbent chemistry,adsorbent porosity,pore shape,size,and tortuosity,pore wall effect,adsorbate-adsorbent interactions,and adsorbate-adsorbate interactions in competitively contaminated aqueous environments.Adsorbent tortuosity has been sporadically studied in aqueous adsorption models.Despite the small population of these studies,insightful observations and inferences have been reported.However,as it appears,no review has been published to compile,compare,and contrast these aspects.Hence,this review concisely brings up those observations and interpretations around adsorbent tortuosity for aqueous adsorption systems.The notion of an adsorbent's tortuosity being single-valued is argued to be imprecise.Finally,perspectives are aired on possible research and development directions for elucidating the dynamic attributes of adsorbent tortuosity and applying them in real-scale adsorption-oriented water purification.The data acquired by filling in these research gaps can enable the design of adsorbents more adapted for real-scale water purification.展开更多
A polystyrene-based ion-exchange resin was employed as the precursor for preparation of resin-derived carbon spheres （RCSs） through KOH activation with various impregnation ratios. Pore structure, yield and hardness...A polystyrene-based ion-exchange resin was employed as the precursor for preparation of resin-derived carbon spheres （RCSs） through KOH activation with various impregnation ratios. Pore structure, yield and hardness, surface functional groups of the samples and their adsorption performance towards dibenzothiophene （DBT） were investigated. The RCSs with large surface areas （up to 2696 m2/g） and total pore volumes （up to 1.46 cm3/g） exhibited larger adsorption capacities than a commercial ac- tivated carbon, F400. Polanyi-Dubinin-Mane （PDM） model was applied to fit the adsorption data, which proved that micropore filling was involved during the adsorption process. Moreover, a good linear relationship was observed between the ex- tra-micropore volume and adsorption capacity. Intra-particle diffusion （IPD） model was used to describe the kinetic data of DBT onto the adsorbents. The adsorption processes were divided into three stages according to the different diffusion parame- ter. The selective adsorption towards DBT in the presence of competing compounds was also investigated and the high selec- tivity of the RSCs towards DBT may be attributed to the large quantity of acidic oxygen-containing groups.展开更多
The equilibrium and kinetic characteristics of the adsorption of erythromycin to Sepabeads SP825 were determined.The equilibrium data in a batch system was well described by a Langmuir isotherm.The separation performa...The equilibrium and kinetic characteristics of the adsorption of erythromycin to Sepabeads SP825 were determined.The equilibrium data in a batch system was well described by a Langmuir isotherm.The separation performance was investigated in a fixed-bed system with respect to the adsorption superficial velocity,ionic strength and pH.A mathematical model was used to simulate the mass transfer mechanism,taking film mass transfer,pore diffusion and axial dispersion into account.The model predictions were consistent with the experi-mental data and were consequently used to determine the mass transfer coefficients.展开更多
文摘Drying kinetics for alcohol-soaked type-A zeolite(pore size 0.5 nm)was determined at 50°C for 12 small-molecule alcohols(from C1 to C10).The second-phase of drying of wet porous materials reports on the mass-transfer characteristics within the solid matrices.This stage follows pseudo first-order kinetics(k1),and the second-order rate constant k2=k1/(fluxional area)was found to correlate with the surface tension of the liquids imbibing the solid matrix(p<0.002).k2 values decrease along the homologous linear alcohols,and branched-chain alcohols diffuse faster than their linear analogues due to their lower surface tensions.No independent contribution was found from the molecular size of the alcohols in the experiment reported here.Characteristic velocity and enthalpy of vaporisation of the liquids were not found to be significant independent variables,either.The find agrees with the notion that liquid movement in pores is governed during the drying processes by the liquid chemical potential gradient between the pore space and gas phase above the porous particle surfaces,this gradient being a function of the molecular cohesion of the moving liquid front(surface tension,g).The results can be expressed by the linear Gibbs-energy relation log(k2/s^(-1)·m^(-2))=(2.5±0.5)-(1.6±0.2)×10^(2)(g/J·m^(-2)).
基金financially supported by the Outstanding Youth Fund of the Natural Science Foundation of Jiangsu, China (No. BK20150050)the National Key Research and Development Program, China (No. 2016YFD0800204)+2 种基金the National Natural Science Foundation of China (No. 21677149)the Institute of Soil Science, Chinese Academy of Sciences (No. ISSASIP1616)the Key Program of Frontier Sciences, Chinese Academy of Sciences (No. QYZDJSSW-DQC035)
文摘The chars in the natural environment can affect the migration of polybrominated diphenyl ethers(PBDEs). However, there is insufficient research relating to the adsorption behavior and mechanisms of PBDEs on biochars. This study examined the adsorption kinetics of 2,2′,4,4′-tetrabromodiphenyl ether(BDE-47) on maize straw-derived biochars(MSBCs) pyrolyzed at four different temperatures via batch experiments. The biochar samples were characterized using Fourier transform infrared(FTIR) spectroscopy,Raman spectra, and elemental analysis. A two-compartment first-order model and pseudo-second-order model exhibited a better fit compared to a pseudo-first-order model in describing the BDE-47 adsorption on biochars, which was dominated by a slow adsorption compartment and chemisorption. The MSBC pyrolyzed at 600 °C had the highest BDE-47 adsorption capacity owing to its relatively large specific surface area and relatively high aromaticity compared with the other three MSBCs pyrolyzed at 300, 400, and 500 ℃.However, there was no significant difference in adsorption capacity among the other three biochars. The organic functional groups coupled with the graphene structures of biochars and the hydrophobic effect of the functional groups promoted the adsorption of BDE-47. Pore diffusion was not the sole rate-limiting step;film diffusion was also involved in the adsorption process of BDE-47 on biochars. The overall results demonstrate the transport and potential treatment of PBDEs using biochars.
基金financially supported by the fund of the institute of seismology,China Earthquake Administration(IS201616254)National Natural Science Foundation of China(41572354,41304046)
文摘The Three Gorges Reservoir is a good site for the further researches on reservoir induced seismicity due to decades＇ seismic monitoring. After the first water impounding in 2003, seismic activity becomes more frequent than that before water impoundment. In order to quantitatively study, the relationship between the water level fluctuation and earthquakes in TGR, we introduced statistical methods to attain the goal. First of all, we relocated the earthquakes in TGR region with double difference method and divided the earthquakes into 5 clusters with clustering analysis method. Secondly, to examine the impacts of water level fluctuation in different water filling stages on the seismic activity in the 5 clusters, a series of statistical analyses are applied. Pearson correlation results show that only the 175 m water level fluc- tuation has significantly positive impacts on the seismic activity in clusters I, II, III and V with correlation coefficients of 0.44, 0.38, 0.66 and 0.63. Cross-correlation analysis demonstrates that 0, ], 0 and 0 month time delay separately for the clusters I, II, III and V exists. It illustrated the influences of the water loading and pore pressure diffusion on induced earthquakes. Cointegration tests and impulse response analysis denoted that the 175 m water level only had long term and significant effects just on the seismic events in the intersection region of the Fairy Mount Fault and Nine-brook Fault. One standard deviation shock to 175 m water level increased the seismic activity in cluster V for the first 3 months, and then the negative influence was shown. After 7 months, the negative impulse response becomes stable. The long-term effect of the 175 m water impoundment also proved the important role of pore pressure diffusion in RIS with time.
基金funded jointly by National Science& Technology Pillar Program (Grant No. 2008BAC38B0401)special fund for basic scientific research of Institute of Geology,CEA (DF-IGCEA060828)
文摘815 earthquakes recorded by 12 seismic stations of the Zipingpu reservoir seismic network in 2009 were relocated using the double difference algorithm to analyze the seismic activity of the Zipingpu reservoir.Relocation results show that the earthquakes are concentrated relatively in three zones.The distribution characteristics of focal depth are obviously different among different concentration zones.This means earthquakes in different concentration zones may have different causes.Compared to relocation of earthquakes taking place before the Wenchuan earthquake done by other researchers,the seismic concentration zones in the reservoir area shifted obviously after the Wenchuan earthquake.These variations are related to local stress adjustment in the reservoir area and may also be related to the diffusion depth and range of increased pore pressure caused by rock failure in the course of Wenchuan earthquake.
基金supported by Project SinoProbe-07 of Chinathe National Natural Science Foundation of China (Grant No. D0408/4097409)+1 种基金the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KJCX2-YW-N42)the Key Important Project of the National Natural Science Foundation of China (Grant No. 10734070)
文摘The study has analyzed the relationship between the water-drainage sluice process of reservoir, stress triggers and shadows of earthquake and porosity variability of fault slip zone. First, the pore pressure, pressure gradient, viscous stress and Reynolds stress to reservoir-earthquake fault slip problem are analyzed, and these are un-negligible factors of the extended coulomb failure stress under ultra-high temperature and pressure condition. Second, the porosity tensor and permeability tensor are studied, the relationship between Zipingpu reservoir and Longmenshan slip has been analyzed, and the extended viscous stress and Reynolds stress as function of time and infiltration process are obtained. Last, some primary conclusions about the flow-solid coupled facture mechanism to the Zipingpu reservoir and Longmenshan slip problem are presented, which can help understand the flow-solid coupled facture mechanism of reservoir-coseismic fault slip problem.
文摘Pore network,pore connectivity,and the resulting effective adsorbate pore diffusivity within an adsorbent are critical physical considerations in mass transport modeling of aqueous adsorption.Tied to these three adsorbent features are the adsorbent tortuosity and tortuosity factor concepts.These concepts encompass the collective hindrance to intra-adsorbent adsorbate transport arising because of a disorderly adsorbent porous topology.It is crucial for materials scientists,chemists,chemical engineers,and water treatment specialists to understand the complex and variable connections among adsorbate chemistry,adsorbent chemistry,adsorbent porosity,pore shape,size,and tortuosity,pore wall effect,adsorbate-adsorbent interactions,and adsorbate-adsorbate interactions in competitively contaminated aqueous environments.Adsorbent tortuosity has been sporadically studied in aqueous adsorption models.Despite the small population of these studies,insightful observations and inferences have been reported.However,as it appears,no review has been published to compile,compare,and contrast these aspects.Hence,this review concisely brings up those observations and interpretations around adsorbent tortuosity for aqueous adsorption systems.The notion of an adsorbent's tortuosity being single-valued is argued to be imprecise.Finally,perspectives are aired on possible research and development directions for elucidating the dynamic attributes of adsorbent tortuosity and applying them in real-scale adsorption-oriented water purification.The data acquired by filling in these research gaps can enable the design of adsorbents more adapted for real-scale water purification.
文摘A polystyrene-based ion-exchange resin was employed as the precursor for preparation of resin-derived carbon spheres （RCSs） through KOH activation with various impregnation ratios. Pore structure, yield and hardness, surface functional groups of the samples and their adsorption performance towards dibenzothiophene （DBT） were investigated. The RCSs with large surface areas （up to 2696 m2/g） and total pore volumes （up to 1.46 cm3/g） exhibited larger adsorption capacities than a commercial ac- tivated carbon, F400. Polanyi-Dubinin-Mane （PDM） model was applied to fit the adsorption data, which proved that micropore filling was involved during the adsorption process. Moreover, a good linear relationship was observed between the ex- tra-micropore volume and adsorption capacity. Intra-particle diffusion （IPD） model was used to describe the kinetic data of DBT onto the adsorbents. The adsorption processes were divided into three stages according to the different diffusion parame- ter. The selective adsorption towards DBT in the presence of competing compounds was also investigated and the high selec- tivity of the RSCs towards DBT may be attributed to the large quantity of acidic oxygen-containing groups.
文摘The equilibrium and kinetic characteristics of the adsorption of erythromycin to Sepabeads SP825 were determined.The equilibrium data in a batch system was well described by a Langmuir isotherm.The separation performance was investigated in a fixed-bed system with respect to the adsorption superficial velocity,ionic strength and pH.A mathematical model was used to simulate the mass transfer mechanism,taking film mass transfer,pore diffusion and axial dispersion into account.The model predictions were consistent with the experi-mental data and were consequently used to determine the mass transfer coefficients.
