Adsorption of Neutral Red (NR) onto peanut husk in aqueous solutions was investigated at 295 K. Experiments were carried out as function of pH, adsorbent dosage, contact time, and initial concentration. The equilibriu...Adsorption of Neutral Red (NR) onto peanut husk in aqueous solutions was investigated at 295 K. Experiments were carried out as function of pH, adsorbent dosage, contact time, and initial concentration. The equilibrium adsorption data were analyzed by Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, and Toth isotherm models. The results indicated that the Toth and Langmuir models provided the best correlation of the experimental data. The adsorption capacity of peanut husk for the removal of NR was deter...展开更多
Since the capacity of CO2 adsorption of coal is a key factor in coal and CO2 outbursts,an experimental study was carried out on CO2 isothermal adsorption with high-pressure volumetry with dry coal samples from the No....Since the capacity of CO2 adsorption of coal is a key factor in coal and CO2 outbursts,an experimental study was carried out on CO2 isothermal adsorption with high-pressure volumetry with dry coal samples from the No.2 coal seam in the Haishiwan Coalfield.Four different equations(Langmuir,BET,D-R and D-A) were used to fit the experimental data.We discuss adsorption mechanisms.The results show that the amount of CO2 adsorption increases rapidly under low relative pressure,i.e.,the ratio of equilibrium pressure and saturated vapor pressure,which indicates that molecular layer adsorption or micropore filling may occur in coal.No clear equilibrium state was observed on the isothermal adsorption curves under relative pressure(P /P0 ) ranging from 0 to 0.8.The fitted results show that the accuracy of the D-A equation is highest with n=1.Micropores are more developed in coal by comparing the BET equation with a pressure mercury injection method on the surface area.The D-A equation(n=1) provides the best fit.By comparing the calculated specific surface area of the BET equation and the mercury intrusion method,it is found that micropore adsorption of CO2 occupies a dominant position.展开更多
Four coal samples of different ranks are selected to perform the adsorption measurement of high-pressure methane(CH4).The highest equilibrium pressure of the measurement exceeds 20 MPa. Combined with the measuring r...Four coal samples of different ranks are selected to perform the adsorption measurement of high-pressure methane(CH4).The highest equilibrium pressure of the measurement exceeds 20 MPa. Combined with the measuring results and theoretical analyses,the reasons for the peak or the maximum adsorption capacity appearing in the excess adsorption isotherms are explained.The rules of the peak occurrence are summarized.And then,based on the features of coal pore structure,the adsorption features of high-pressure gas,the microcosmic interaction relationship of coal surface and CH4 molecule,and the coalbed methane reservoir conditions,three theoretical assumptions on the coal adsorption high-pressure CH_4 are suggested.Thereafter,on the basis of these theoretical assumptions,the Ono-Kondo lattice model is processed for simplification and deformation. Subsequently,the equations modeling the excess adsorption isotherm of high-pressure CH_4 adsorption on coal are obtained.Through the verification on the measurement data,the fitting results indicate that it is feasible to use the Ono-Kondo lattice mode to model the excess adsorption isotherm of high-pressure CH_4 adsorption on coal.展开更多
It is important to quantitatively understand the methane adsorption and transport mechanism in coal for an evaluation of the reserves and for its production forecast. In this work, a block coal sample was chosen to pe...It is important to quantitatively understand the methane adsorption and transport mechanism in coal for an evaluation of the reserves and for its production forecast. In this work, a block coal sample was chosen to perform the CH_4 adsorption experiments using the gravimetric method at temperatures of 293.60 K, 311.26 K, 332.98 K and 352.55 K and pressures up to 19 MPa. The excess adsorption capacity of CH_4 in dry block anthracite increased, followed by a sequence decrease with the increasing pressure. High temperature restrained the growth of the excess adsorption due to that the adsorption is an intrinsically physical and exothermic process. The excess adsorption peak decreased slowly with the increase of temperature and intersected at a pressure of more than 18 MPa; meanwhile, the pressure at the excess adsorption peak increased. The existing correlations were exanfined in terms of density rather than pressure. The DR+k correlation, with an average relative deviation of 4-0.51%, fitted our data better than the others, with an average relative deviation of up to 2.29%. The transportation characteristics of CH_4 adsorption was also investigated in this study, including the adsorption rate and diffusion in block coal. The kinetic data could be described by a modified unipore model. The adsorption rates were found to exhibit dependence on pressure and temperature at low pressures, while the calculated diffusivities exhibited little temperature dependence. In addition, the kinetic characteristics were compared between CH_4 and CO_2 adsorption on the block coal. The excess adsorption ratios of CO_2 to CH_4 obtained from the DR+k model decreased with the increasing pressure.展开更多
This study investigated <i>Bacillus subtilis</i> ATCC13952 as an adsorbent for arsenic in groundwater. Batch experiments were used to determine the effect of contact time, adsorbent dose, arsenic (III) con...This study investigated <i>Bacillus subtilis</i> ATCC13952 as an adsorbent for arsenic in groundwater. Batch experiments were used to determine the effect of contact time, adsorbent dose, arsenic (III) concentration, pH, and temperature on the process. The percentage of arsenic (III) removed was high at a contact time of four days, 3.0 mL of <i>Bacillus subtilis</i> ATCC13952, pH 8 and temperature of 35°C. The kinetics of the process showed the Elovich kinetics model as the best fit for the process. This indicates that arsenic removal was by chemisorption. The analysis of the nonlinear equilibrium isotherms and the error functions showed the Langmuir isotherm as best fit for the process. Mechanistic study of the process indicated bulk diffusion to be the rate-determining step. Thermodynamically, the process was favourable, spontaneous and feasible. When the community water samples were treated with the <i>Bacillus subtilis</i> ATCC13952 at the optimum contact time, adsorbent dose, pH and temperature, 99.96% - 99.97% of arsenic was removed across all sampling points within the studied communities. Hence, the results show that <i>Bacillus subtilis</i> ATCC13952 is an efficient adsorbent for arsenic in aqueous systems and the organism appears to hold the key to purging the environment of arsenic contamination.展开更多
A comparison of the adsorption isotherms of caffeine, theophylline and theobromine and the competitive adsorption of the three compounds on a C18 column were investigated. The experimental parameters of the equilibriu...A comparison of the adsorption isotherms of caffeine, theophylline and theobromine and the competitive adsorption of the three compounds on a C18 column were investigated. The experimental parameters of the equilibrium isotherms were estimated by linear and nonlinear regression analyses. The linear equation as a function of the adsorption concentration of the single compound in its solution and the competitive adsorption of a single compound in a mixed solution were then determined. The adsorption equilibrium data were then correlated to the linear, Langmuir, Freundlich, Langmuir-Freundlich and stoichiometric displacement theory for adsorption(SDT-A) isotherm models. The mixed compounds of the three compounds were competitively adsorbed on the C18 particles. The expression of stoichiometric displacement theory for adsorption was found to be more suitable for adsorption of methylxanthines on a C18 column.展开更多
A molecular imprinted polymer(MIP) was prepared with quereetin as the template and methaerylie acid(MAA) as the functional monomer. Aeetonitrile and methanol were used as the porogen with ethylene glycol dimethaer...A molecular imprinted polymer(MIP) was prepared with quereetin as the template and methaerylie acid(MAA) as the functional monomer. Aeetonitrile and methanol were used as the porogen with ethylene glycol dimethaerylate (EGDMA) as the erosslinker and 2,2'-azobis ( isobutyronitrile ) ( AIBN ) as the initiator. The experimental parameters of the equilibrium isotherms were estimated via linear and nonlinear regression analyses. The linear equadon as the functions of the adsorption concentration of the single compound in its solution and the competitive adsorption of the single compound in its mixed compounds solution was then expressed, and the adsorption equilibrium data were correlated to Langmuir and Freundlich isotherm models. The mixture compounds show competitive adsorption on the specific binding sites of quereetin-MIP. Furthermore, the competitive Langmnir isotherms were applied to the mixture compounds. The adsorption concentrations of quercetin, (+)eatechin(+C), and (-)epieateehin(EC) on the quercetin molecular imprinted polymer were compared. The quercetin-imprinted polymer shows extraordinarily higher adsorption ability for quercetin than for the two eateehin compounds that were also assessed.展开更多
Water sorption isotherms are unique for individual food materials and can be used directly to predict shelf life and determine proper storage conditions. In this context, the aim of this study was to determine the moi...Water sorption isotherms are unique for individual food materials and can be used directly to predict shelf life and determine proper storage conditions. In this context, the aim of this study was to determine the moisture adsorption isotherms of amaranth flour at 15℃, 25℃ and 35℃ in a range of water activity from 0.1 to 0.9. Experimental data were modeled using five equations commonly applied in the foods field. The goodness of the fit for each isotherm model was evaluated through the coefficient of determination, the variance due to error and the confidence interval of the estimated parameters. All models can predict the adsorption isotherms of amaranth flour, but the GAB equation gives a better understanding of the observed sorption behavior. Estimated adsorption monolayer water contents ranged from 6.4 g to 7.2 g of water per 100 g of dry material. It was observed by a weak dependence of water activity with temperature. For ensuring microbiological stability, water content in amaranth flour should not be higher than 13 g of water per 100 g of dry material.展开更多
A series of chitosan-g-poly (acrylic acid)/vermiculite hydrogel composites were synthesized and used as adsorbents for the investigation of the effect of process parameters such as vermiculite content, pH of dye sol...A series of chitosan-g-poly (acrylic acid)/vermiculite hydrogel composites were synthesized and used as adsorbents for the investigation of the effect of process parameters such as vermiculite content, pH of dye solution, contact time, initial concentration of dye solution, temperature, ionic strength and concentration of surfactant sodium dodecyl sulfate on the removal of Methylene Blue (MB) from aqueous solution. The results showed that the adsorption capacity for dye increased with increasing pH, contact time and initial dye concentration, but decreased with increasing temperature, ionic strength and sodium dodecyl sulfate concentration in the present of the surfactant. The adsorption kinetics of MB onto the hydrogel composite followed pseudo second-order kinetics and the adsorption equilibrium data obeyed Langmuir isotherm. By introducing 10 wt.% vermiculite into chitosan-g-poly (acrylic acid) polymeric network, the obtaining hydrogel composite showed the highest adsorption capacity for MB, and then could be regarded as a potential adsorbent for cationic dye removal in a wastewater treatment process.展开更多
Batch adsorption from aqueous solutions in a slightly basic medium of Methylene Blue, up to 2500 mg/L, onto synthetic magnesium silicate (Florisil) of three particle size ranges (mean diameters of 112, 200 and 425 ...Batch adsorption from aqueous solutions in a slightly basic medium of Methylene Blue, up to 2500 mg/L, onto synthetic magnesium silicate (Florisil) of three particle size ranges (mean diameters of 112, 200 and 425 μm) was compared to the corresponding adsorption onto activated carbon and Amberlite XAD-2. The best fit of the kinetic results was achieved by a pseudo second-order equation. The equilibrium data were found to be well represented by the Langmuir isotherm equation. Amberlite XAD-2, an unspecific adsorbent capable of adsorbing exclusively through a surface effect, exhibited a poor dye uptake, confirming that the adsorption mechanism on Florisil was due to electrostatic attraction and ion exchange. Moreover, the comparison between Florisil and the other adsorbents was performed on the basis of the evaluation of the surface area and pore volume occupied by the adsorbed dye.展开更多
The adsorption potential of titanium dioxide (TiO2) nanoparticles for removing arsenic from drinking water was evaluated. Pure and iron-doped TiO2 particles are synthesized via sol-gel method. The synthesized TiO2 n...The adsorption potential of titanium dioxide (TiO2) nanoparticles for removing arsenic from drinking water was evaluated. Pure and iron-doped TiO2 particles are synthesized via sol-gel method. The synthesized TiO2 nanoparticles were then immobilized on ordinary sand for adsorption studies. Adsorption isotherms were conducted on the synthesized nanoparticles as well as the sand coated with TiO2 nanoparticles under varying conditions of air and light, namely, the air-sunlight (A-SL), air-light (AL), air-dark (AD) and nitrogen-dark (ND). X-ray diffraction (XRD) analysis showed that the pure and iron-doped TiO2 nanoparticles were in 100% anatase crystalline phase with crystai sizes of 108 and 65 nm, respectively. Adsorption of arsenic on the three adsorbents was non-linear that could be described by the Freundlich and Langmuir adsorption models. Iron doping enhanced the adsorption capacity of TiO2 nanoparticles by arresting the grain growth and making it visible light responsive resulting in a higher affinity for arsenic. Similarly, the arsenic removal by adsorption on the sand coated with TiO2 nanoparticles was the highest among the three types of sand used. In all cases, As(V) was adsorbed more compared with As(Ⅲ). The solution pH appeared to be the most important factor in controlling the amount of arsenic adsorbed.展开更多
The present study has been undertaken to evaluate the adsorption in batch mode of a disperse dye (Disperse Blue SBL) by poorly crystalline hydroxyapatite synthesized by coprecipitation between Ca(NO3)2and (NH4)2HPO4 r...The present study has been undertaken to evaluate the adsorption in batch mode of a disperse dye (Disperse Blue SBL) by poorly crystalline hydroxyapatite synthesized by coprecipitation between Ca(NO3)2and (NH4)2HPO4 reagents in aqueous solution at room temperature. The adsorption experiments were carried out to investigate the factors that influence the dye uptake by the adsorbent, such as the contact time under agitation, adsorbent dosage, initial dye concentration, solution temperature, and pH. The experimental results show that the percentage of dye removal increases with increasing the amount of adsorbent, until the total discoloration. The adsorption isotherms follow the model of Langmuir with a high adsorption capacity. The adsorption was pH and temperature dependent.展开更多
Azo dyes have received considerable attention because of their association with various human health problems. The aim of the investigation is to determine the adsorption behavior ofazo dyes in aqueous solution on DG0...Azo dyes have received considerable attention because of their association with various human health problems. The aim of the investigation is to determine the adsorption behavior ofazo dyes in aqueous solution on DG06, GSE17200, and GSE17201 soils using C. I. Acid Red 14 (AR14) as example. The experimental results indicate that the Freundlich model expresses the adsorption isotherm better than the Langmuir model and the pseudo-second-order model achieves adsorption of AR14 on the three soils well. Based on the pseudo-second-order model, the adsorption thermodynamic of AR14 on DG06 soil have been studied and the thermodynamics parameter of AGO is determined and AGO value shows the adsorption process of AR14 on DG06 is mainly physical in nature. Furthermore, the effects of temperature, pH and salinity (NaC1) on adsorption have been investigated. The decrease in pH or the increase in salinity enhances the adsorption of AR14 by DG06, GSE17200, and GSE17201.展开更多
The adsorption capacity and absorption rate for electrolyte onto activated carbon are important parameters used to characterize activated carbon electric double-layer capacitor electrodes. In this paper the pore struc...The adsorption capacity and absorption rate for electrolyte onto activated carbon are important parameters used to characterize activated carbon electric double-layer capacitor electrodes. In this paper the pore structure of typical commercial activated carbons, and various Mn-doped activated carbons prepared on a laboratory scale, are described. The pore structure was character-ized by N2 adsorption/desorption isotherms. Isotherms for K+ adsorption onto these activated carbons from the aqueous phase were also obtained. The experimental, equilibrium K+ adsorption data were fitted to the Langmuir, Freundlich or Temkin equations. Adsorption of K+ onto the activated carbons was measured and plotted as a function of time. The adsorption kinetic data were modeled by either pseudo-first or pseudo-second order equations. The Elvoich equation, a liquid film diffusion and an intra-particle diffusion model were used to fit the kinetic data. The results indicate that the adsorption of K+ onto activated carbon is influenced by many factors including pore size distribution, specific surface area and the surface chemistry of the activated carbons. The Temkin equation best describes the equilibrium adsorption data. The pseudo-second order model exactly describes the whole adsorption process, which is controlled by both liquid film and intra-particle diffusion.展开更多
Adsorption of 2, 4, 6-trichlorophenol(TCP) onto the calcined Mg/Al-CO_3 layered double hydroxide(CLDH) was investigated. The prepared Mg/Al-CO_3 layered double hydroxide(LDH) and CLDH were characterized by powde...Adsorption of 2, 4, 6-trichlorophenol(TCP) onto the calcined Mg/Al-CO_3 layered double hydroxide(CLDH) was investigated. The prepared Mg/Al-CO_3 layered double hydroxide(LDH) and CLDH were characterized by powder X-ray diffraction(XRD) and thermo gravimetric analyzer-differential scanning calorimeters(TG-DSC). Moreover, 2,4,6-trichlorophenol(TCP) was removed effectively(94.7% of removal percentage in 9h) under the optimized experimental conditions. The adsorption kinetics data fitted the pseudosecond-order model well. The Freundlich, Langmuir, and Tempkin adsorption models were applied to the experimental equilibrium adsorption data at different temperatures of solution. The adsorption data fitted the Freundlieh adsorption isotherm with good values of the correlation coefficient. A mechanism of the adsorption process is proposed according to the intraparticle diffusion model, which indicates that the overall rate of adsorption can be described as three steps.展开更多
Activated carbons,RS-1,RS-2,and RS-3,prepared from rice straw with(NH4)2HPO4 activation were used as adsorbents for removing phenols from aqueous solutions.The maximum adsorption capacities of phenol for RS-1,RS-2,and...Activated carbons,RS-1,RS-2,and RS-3,prepared from rice straw with(NH4)2HPO4 activation were used as adsorbents for removing phenols from aqueous solutions.The maximum adsorption capacities of phenol for RS-1,RS-2,and RS-3 were 163.9,172.9,and 200.0 mg/g,respectively.The equilibrium data were analyzed by the Langmuir,Freundlich,and Temkin models.It displayed that Langmuir isotherm fitted to the results best.The dimensionless parameter RL indicated the favorable nature of the adsorption of phenol.Otherwise,the kinetic rates were well explained by pseudo-second-order model.According to the results,activated carbon derived from waste rice straw can be a high-performance adsorbent for wastewater treatment.展开更多
The frontier orbital energies of montmorillonite molecule and[Me(H_(2)O)_(6)]^(2+)(Me=Cu^(2+),Zn^(2+),Co^(2+)and Ni^(2+))were calculated by INDO method.Results showed that the chemical interaction between montmorillon...The frontier orbital energies of montmorillonite molecule and[Me(H_(2)O)_(6)]^(2+)(Me=Cu^(2+),Zn^(2+),Co^(2+)and Ni^(2+))were calculated by INDO method.Results showed that the chemical interaction between montmorillonite molecule and[Cu(H_(2)O)_(6)]^(2+)or[Zn(H_(2)O)_(6)]^(2+)was possible.The experimental results of powder X-ray diffraction and isothermal adsorption supported the above-mentioned calculation results.展开更多
The adsorption characteristics of Pb on sediments of the Dianshan Lake in Shanghai was studied. The results show that (1) the relationship between the amount q of apparent equilibrium adsorption and the equilibrium co...The adsorption characteristics of Pb on sediments of the Dianshan Lake in Shanghai was studied. The results show that (1) the relationship between the amount q of apparent equilibrium adsorption and the equilibrium concentration C conforms to the Freundlich isothermal adsorption equation; (2) the adsorption and desorption of Pb on sediments are not reversible, that is, adsorption/desorption of Pb exhibits hysteresis; (3) Pb adsorption behavior is initially fast, followed by a slow reaction, and the slow reaction conforms to a reversible first-order reaction; (4) by deducing the Pb adsorption kinetics, four kinetics parameters n,k 1,k 2,q (max) independent of C could be worked out; (5) the equilibrium parameter (K) and the free energy change (ΔG) could also be determined, and the negative values of free energy change (ΔG) indicate the spontaneous nature of the adsorption.展开更多
Two hypercrosslinked resins with similar physical characters but different surface chemistry were synthesized and used to remove phenol from aqueous solutions. The FTIR spectra, elemental analysis and the Boehm titrat...Two hypercrosslinked resins with similar physical characters but different surface chemistry were synthesized and used to remove phenol from aqueous solutions. The FTIR spectra, elemental analysis and the Boehm titration were used to characterize the chemical properties of the resins. The adsorption experiments were carried out using the bottle-point technique, and the effects of the surface chemistry on the adsorption were discussed. The adsorption data fit well with the Freundlich model, indicating the heterogeneity of the resins surface. It could be seen from the experimental results that the adsorption capacity increased with the increase in the total surface concentration of oxygen-containing groups. The pH dependence and the effects of ionic strength were also discussed. The kinetic adsorption data fit well with the pseudo-second order model, and the results showed that the surface oxygen-containing groups have little effect on the adsorption rate.展开更多
A geometrical definition, fractal dimension, was introduced in this study to evaluate copper adsorption in wood treated with copper-containing preservatives. It is based on the assumption that some copper would compet...A geometrical definition, fractal dimension, was introduced in this study to evaluate copper adsorption in wood treated with copper-containing preservatives. It is based on the assumption that some copper would compete the hydroxyl groups in wood cell wall with water molecules, and therefore influence the fractal dimension of internal wood surfaces revealed by the moisture adsorption in wood. Southern yellow pine (Pinus spp.) specimens were treated with different concentrations of copper ethanolamine (Cu-EA) solution to obtain different copper retention levels. Then the adsorption isotherms of untreated and Cu-EA treated specimens were determined at 4, 15, 30, and 40 ℃ to provide the source data for fractal dimension calculation. The results showed that, at all temperatures, the fractal dimension of the internal wood surfaces had a decreasing trend with increasing copper retention. That is, the internal spaces in wood become 搕hinner?due to the copper adsorption on some hydroxyl groups in wood cell wall. The correlation between the fractal dimension and adsorbed copper ions makes it possible to evaluate the copper adsorption in wood cell wall.展开更多
基金the China PostdoctoralScience Foundation (No. 20070420811)the Edu-cation Department of Henan Province in China (No.200510459016)
文摘Adsorption of Neutral Red (NR) onto peanut husk in aqueous solutions was investigated at 295 K. Experiments were carried out as function of pH, adsorbent dosage, contact time, and initial concentration. The equilibrium adsorption data were analyzed by Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, and Toth isotherm models. The results indicated that the Toth and Langmuir models provided the best correlation of the experimental data. The adsorption capacity of peanut husk for the removal of NR was deter...
基金the National Basic Research Program of China (No.2005CB221503)the Major Program of the National Natural Science Foundation (Nos.70533050 and 50674089) for their support of this project
文摘Since the capacity of CO2 adsorption of coal is a key factor in coal and CO2 outbursts,an experimental study was carried out on CO2 isothermal adsorption with high-pressure volumetry with dry coal samples from the No.2 coal seam in the Haishiwan Coalfield.Four different equations(Langmuir,BET,D-R and D-A) were used to fit the experimental data.We discuss adsorption mechanisms.The results show that the amount of CO2 adsorption increases rapidly under low relative pressure,i.e.,the ratio of equilibrium pressure and saturated vapor pressure,which indicates that molecular layer adsorption or micropore filling may occur in coal.No clear equilibrium state was observed on the isothermal adsorption curves under relative pressure(P /P0 ) ranging from 0 to 0.8.The fitted results show that the accuracy of the D-A equation is highest with n=1.Micropores are more developed in coal by comparing the BET equation with a pressure mercury injection method on the surface area.The D-A equation(n=1) provides the best fit.By comparing the calculated specific surface area of the BET equation and the mercury intrusion method,it is found that micropore adsorption of CO2 occupies a dominant position.
基金supported by the project of China National 973 Program"Basic Research on Enrichment Mechanism and Improving the Exploitation Efficiency of Coalbed Methane Reservoir"(Grant No. 2009CB219600)the National Natural Science Foundation of China(Grant No.40672100)
文摘Four coal samples of different ranks are selected to perform the adsorption measurement of high-pressure methane(CH4).The highest equilibrium pressure of the measurement exceeds 20 MPa. Combined with the measuring results and theoretical analyses,the reasons for the peak or the maximum adsorption capacity appearing in the excess adsorption isotherms are explained.The rules of the peak occurrence are summarized.And then,based on the features of coal pore structure,the adsorption features of high-pressure gas,the microcosmic interaction relationship of coal surface and CH4 molecule,and the coalbed methane reservoir conditions,three theoretical assumptions on the coal adsorption high-pressure CH_4 are suggested.Thereafter,on the basis of these theoretical assumptions,the Ono-Kondo lattice model is processed for simplification and deformation. Subsequently,the equations modeling the excess adsorption isotherm of high-pressure CH_4 adsorption on coal are obtained.Through the verification on the measurement data,the fitting results indicate that it is feasible to use the Ono-Kondo lattice mode to model the excess adsorption isotherm of high-pressure CH_4 adsorption on coal.
基金supported by Liaoning Provincial Natural Science Foundation of China(201202028)the National Program on the Key Basic Research Project(No.2011CB707304)+1 种基金the National Natural Science Foundation of China(No.51006016)the China Scholarship Council
文摘It is important to quantitatively understand the methane adsorption and transport mechanism in coal for an evaluation of the reserves and for its production forecast. In this work, a block coal sample was chosen to perform the CH_4 adsorption experiments using the gravimetric method at temperatures of 293.60 K, 311.26 K, 332.98 K and 352.55 K and pressures up to 19 MPa. The excess adsorption capacity of CH_4 in dry block anthracite increased, followed by a sequence decrease with the increasing pressure. High temperature restrained the growth of the excess adsorption due to that the adsorption is an intrinsically physical and exothermic process. The excess adsorption peak decreased slowly with the increase of temperature and intersected at a pressure of more than 18 MPa; meanwhile, the pressure at the excess adsorption peak increased. The existing correlations were exanfined in terms of density rather than pressure. The DR+k correlation, with an average relative deviation of 4-0.51%, fitted our data better than the others, with an average relative deviation of up to 2.29%. The transportation characteristics of CH_4 adsorption was also investigated in this study, including the adsorption rate and diffusion in block coal. The kinetic data could be described by a modified unipore model. The adsorption rates were found to exhibit dependence on pressure and temperature at low pressures, while the calculated diffusivities exhibited little temperature dependence. In addition, the kinetic characteristics were compared between CH_4 and CO_2 adsorption on the block coal. The excess adsorption ratios of CO_2 to CH_4 obtained from the DR+k model decreased with the increasing pressure.
文摘This study investigated <i>Bacillus subtilis</i> ATCC13952 as an adsorbent for arsenic in groundwater. Batch experiments were used to determine the effect of contact time, adsorbent dose, arsenic (III) concentration, pH, and temperature on the process. The percentage of arsenic (III) removed was high at a contact time of four days, 3.0 mL of <i>Bacillus subtilis</i> ATCC13952, pH 8 and temperature of 35°C. The kinetics of the process showed the Elovich kinetics model as the best fit for the process. This indicates that arsenic removal was by chemisorption. The analysis of the nonlinear equilibrium isotherms and the error functions showed the Langmuir isotherm as best fit for the process. Mechanistic study of the process indicated bulk diffusion to be the rate-determining step. Thermodynamically, the process was favourable, spontaneous and feasible. When the community water samples were treated with the <i>Bacillus subtilis</i> ATCC13952 at the optimum contact time, adsorbent dose, pH and temperature, 99.96% - 99.97% of arsenic was removed across all sampling points within the studied communities. Hence, the results show that <i>Bacillus subtilis</i> ATCC13952 is an efficient adsorbent for arsenic in aqueous systems and the organism appears to hold the key to purging the environment of arsenic contamination.
基金Supported by the Basic Science Research Program Through the National Research Foundation(NRF) of Korea funded by the Ministry of Education, Science and Technology(No.2010-0015731)
文摘A comparison of the adsorption isotherms of caffeine, theophylline and theobromine and the competitive adsorption of the three compounds on a C18 column were investigated. The experimental parameters of the equilibrium isotherms were estimated by linear and nonlinear regression analyses. The linear equation as a function of the adsorption concentration of the single compound in its solution and the competitive adsorption of a single compound in a mixed solution were then determined. The adsorption equilibrium data were then correlated to the linear, Langmuir, Freundlich, Langmuir-Freundlich and stoichiometric displacement theory for adsorption(SDT-A) isotherm models. The mixed compounds of the three compounds were competitively adsorbed on the C18 particles. The expression of stoichiometric displacement theory for adsorption was found to be more suitable for adsorption of methylxanthines on a C18 column.
基金Supported by the Center for Advanced Bioseparation Technology and the Postdoctoral Program of Inha University.
文摘A molecular imprinted polymer(MIP) was prepared with quereetin as the template and methaerylie acid(MAA) as the functional monomer. Aeetonitrile and methanol were used as the porogen with ethylene glycol dimethaerylate (EGDMA) as the erosslinker and 2,2'-azobis ( isobutyronitrile ) ( AIBN ) as the initiator. The experimental parameters of the equilibrium isotherms were estimated via linear and nonlinear regression analyses. The linear equadon as the functions of the adsorption concentration of the single compound in its solution and the competitive adsorption of the single compound in its mixed compounds solution was then expressed, and the adsorption equilibrium data were correlated to Langmuir and Freundlich isotherm models. The mixture compounds show competitive adsorption on the specific binding sites of quereetin-MIP. Furthermore, the competitive Langmnir isotherms were applied to the mixture compounds. The adsorption concentrations of quercetin, (+)eatechin(+C), and (-)epieateehin(EC) on the quercetin molecular imprinted polymer were compared. The quercetin-imprinted polymer shows extraordinarily higher adsorption ability for quercetin than for the two eateehin compounds that were also assessed.
基金support of the Swedish International Development Agency(Sida).
文摘Water sorption isotherms are unique for individual food materials and can be used directly to predict shelf life and determine proper storage conditions. In this context, the aim of this study was to determine the moisture adsorption isotherms of amaranth flour at 15℃, 25℃ and 35℃ in a range of water activity from 0.1 to 0.9. Experimental data were modeled using five equations commonly applied in the foods field. The goodness of the fit for each isotherm model was evaluated through the coefficient of determination, the variance due to error and the confidence interval of the estimated parameters. All models can predict the adsorption isotherms of amaranth flour, but the GAB equation gives a better understanding of the observed sorption behavior. Estimated adsorption monolayer water contents ranged from 6.4 g to 7.2 g of water per 100 g of dry material. It was observed by a weak dependence of water activity with temperature. For ensuring microbiological stability, water content in amaranth flour should not be higher than 13 g of water per 100 g of dry material.
基金supported by the National Natural Science Foundation of China (No.20877077)the Project of Jiangsu Provincial Science and Technology Office (No.BE2008087)
文摘A series of chitosan-g-poly (acrylic acid)/vermiculite hydrogel composites were synthesized and used as adsorbents for the investigation of the effect of process parameters such as vermiculite content, pH of dye solution, contact time, initial concentration of dye solution, temperature, ionic strength and concentration of surfactant sodium dodecyl sulfate on the removal of Methylene Blue (MB) from aqueous solution. The results showed that the adsorption capacity for dye increased with increasing pH, contact time and initial dye concentration, but decreased with increasing temperature, ionic strength and sodium dodecyl sulfate concentration in the present of the surfactant. The adsorption kinetics of MB onto the hydrogel composite followed pseudo second-order kinetics and the adsorption equilibrium data obeyed Langmuir isotherm. By introducing 10 wt.% vermiculite into chitosan-g-poly (acrylic acid) polymeric network, the obtaining hydrogel composite showed the highest adsorption capacity for MB, and then could be regarded as a potential adsorbent for cationic dye removal in a wastewater treatment process.
文摘Batch adsorption from aqueous solutions in a slightly basic medium of Methylene Blue, up to 2500 mg/L, onto synthetic magnesium silicate (Florisil) of three particle size ranges (mean diameters of 112, 200 and 425 μm) was compared to the corresponding adsorption onto activated carbon and Amberlite XAD-2. The best fit of the kinetic results was achieved by a pseudo second-order equation. The equilibrium data were found to be well represented by the Langmuir isotherm equation. Amberlite XAD-2, an unspecific adsorbent capable of adsorbing exclusively through a surface effect, exhibited a poor dye uptake, confirming that the adsorption mechanism on Florisil was due to electrostatic attraction and ion exchange. Moreover, the comparison between Florisil and the other adsorbents was performed on the basis of the evaluation of the surface area and pore volume occupied by the adsorbed dye.
文摘The adsorption potential of titanium dioxide (TiO2) nanoparticles for removing arsenic from drinking water was evaluated. Pure and iron-doped TiO2 particles are synthesized via sol-gel method. The synthesized TiO2 nanoparticles were then immobilized on ordinary sand for adsorption studies. Adsorption isotherms were conducted on the synthesized nanoparticles as well as the sand coated with TiO2 nanoparticles under varying conditions of air and light, namely, the air-sunlight (A-SL), air-light (AL), air-dark (AD) and nitrogen-dark (ND). X-ray diffraction (XRD) analysis showed that the pure and iron-doped TiO2 nanoparticles were in 100% anatase crystalline phase with crystai sizes of 108 and 65 nm, respectively. Adsorption of arsenic on the three adsorbents was non-linear that could be described by the Freundlich and Langmuir adsorption models. Iron doping enhanced the adsorption capacity of TiO2 nanoparticles by arresting the grain growth and making it visible light responsive resulting in a higher affinity for arsenic. Similarly, the arsenic removal by adsorption on the sand coated with TiO2 nanoparticles was the highest among the three types of sand used. In all cases, As(V) was adsorbed more compared with As(Ⅲ). The solution pH appeared to be the most important factor in controlling the amount of arsenic adsorbed.
文摘The present study has been undertaken to evaluate the adsorption in batch mode of a disperse dye (Disperse Blue SBL) by poorly crystalline hydroxyapatite synthesized by coprecipitation between Ca(NO3)2and (NH4)2HPO4 reagents in aqueous solution at room temperature. The adsorption experiments were carried out to investigate the factors that influence the dye uptake by the adsorbent, such as the contact time under agitation, adsorbent dosage, initial dye concentration, solution temperature, and pH. The experimental results show that the percentage of dye removal increases with increasing the amount of adsorbent, until the total discoloration. The adsorption isotherms follow the model of Langmuir with a high adsorption capacity. The adsorption was pH and temperature dependent.
文摘Azo dyes have received considerable attention because of their association with various human health problems. The aim of the investigation is to determine the adsorption behavior ofazo dyes in aqueous solution on DG06, GSE17200, and GSE17201 soils using C. I. Acid Red 14 (AR14) as example. The experimental results indicate that the Freundlich model expresses the adsorption isotherm better than the Langmuir model and the pseudo-second-order model achieves adsorption of AR14 on the three soils well. Based on the pseudo-second-order model, the adsorption thermodynamic of AR14 on DG06 soil have been studied and the thermodynamics parameter of AGO is determined and AGO value shows the adsorption process of AR14 on DG06 is mainly physical in nature. Furthermore, the effects of temperature, pH and salinity (NaC1) on adsorption have been investigated. The decrease in pH or the increase in salinity enhances the adsorption of AR14 by DG06, GSE17200, and GSE17201.
基金the financial support from the Research Fund for the Doctoral Program of Higher Education of China (No.2006 0290006)
文摘The adsorption capacity and absorption rate for electrolyte onto activated carbon are important parameters used to characterize activated carbon electric double-layer capacitor electrodes. In this paper the pore structure of typical commercial activated carbons, and various Mn-doped activated carbons prepared on a laboratory scale, are described. The pore structure was character-ized by N2 adsorption/desorption isotherms. Isotherms for K+ adsorption onto these activated carbons from the aqueous phase were also obtained. The experimental, equilibrium K+ adsorption data were fitted to the Langmuir, Freundlich or Temkin equations. Adsorption of K+ onto the activated carbons was measured and plotted as a function of time. The adsorption kinetic data were modeled by either pseudo-first or pseudo-second order equations. The Elvoich equation, a liquid film diffusion and an intra-particle diffusion model were used to fit the kinetic data. The results indicate that the adsorption of K+ onto activated carbon is influenced by many factors including pore size distribution, specific surface area and the surface chemistry of the activated carbons. The Temkin equation best describes the equilibrium adsorption data. The pseudo-second order model exactly describes the whole adsorption process, which is controlled by both liquid film and intra-particle diffusion.
基金Funded by the National Natural Science Foundation of China(No.21476269)
文摘Adsorption of 2, 4, 6-trichlorophenol(TCP) onto the calcined Mg/Al-CO_3 layered double hydroxide(CLDH) was investigated. The prepared Mg/Al-CO_3 layered double hydroxide(LDH) and CLDH were characterized by powder X-ray diffraction(XRD) and thermo gravimetric analyzer-differential scanning calorimeters(TG-DSC). Moreover, 2,4,6-trichlorophenol(TCP) was removed effectively(94.7% of removal percentage in 9h) under the optimized experimental conditions. The adsorption kinetics data fitted the pseudosecond-order model well. The Freundlich, Langmuir, and Tempkin adsorption models were applied to the experimental equilibrium adsorption data at different temperatures of solution. The adsorption data fitted the Freundlieh adsorption isotherm with good values of the correlation coefficient. A mechanism of the adsorption process is proposed according to the intraparticle diffusion model, which indicates that the overall rate of adsorption can be described as three steps.
基金Key Project of Shanghai Basic Research,China (No. 08JC1400500)Program for New Century Excellent Talents in University,China (No. NECT-07-0175)+1 种基金Key Project of Chinese Ministry of Education,China (No. 107046)Shanghai Leading Academic Discipline Project,China (No. B604)
文摘Activated carbons,RS-1,RS-2,and RS-3,prepared from rice straw with(NH4)2HPO4 activation were used as adsorbents for removing phenols from aqueous solutions.The maximum adsorption capacities of phenol for RS-1,RS-2,and RS-3 were 163.9,172.9,and 200.0 mg/g,respectively.The equilibrium data were analyzed by the Langmuir,Freundlich,and Temkin models.It displayed that Langmuir isotherm fitted to the results best.The dimensionless parameter RL indicated the favorable nature of the adsorption of phenol.Otherwise,the kinetic rates were well explained by pseudo-second-order model.According to the results,activated carbon derived from waste rice straw can be a high-performance adsorbent for wastewater treatment.
文摘The frontier orbital energies of montmorillonite molecule and[Me(H_(2)O)_(6)]^(2+)(Me=Cu^(2+),Zn^(2+),Co^(2+)and Ni^(2+))were calculated by INDO method.Results showed that the chemical interaction between montmorillonite molecule and[Cu(H_(2)O)_(6)]^(2+)or[Zn(H_(2)O)_(6)]^(2+)was possible.The experimental results of powder X-ray diffraction and isothermal adsorption supported the above-mentioned calculation results.
文摘The adsorption characteristics of Pb on sediments of the Dianshan Lake in Shanghai was studied. The results show that (1) the relationship between the amount q of apparent equilibrium adsorption and the equilibrium concentration C conforms to the Freundlich isothermal adsorption equation; (2) the adsorption and desorption of Pb on sediments are not reversible, that is, adsorption/desorption of Pb exhibits hysteresis; (3) Pb adsorption behavior is initially fast, followed by a slow reaction, and the slow reaction conforms to a reversible first-order reaction; (4) by deducing the Pb adsorption kinetics, four kinetics parameters n,k 1,k 2,q (max) independent of C could be worked out; (5) the equilibrium parameter (K) and the free energy change (ΔG) could also be determined, and the negative values of free energy change (ΔG) indicate the spontaneous nature of the adsorption.
基金This work was supported by the Jiangsu Province Hi-Tech Fund (GB2003030)Jiangsu Province Natural Science Fund (No. 2004088).
文摘Two hypercrosslinked resins with similar physical characters but different surface chemistry were synthesized and used to remove phenol from aqueous solutions. The FTIR spectra, elemental analysis and the Boehm titration were used to characterize the chemical properties of the resins. The adsorption experiments were carried out using the bottle-point technique, and the effects of the surface chemistry on the adsorption were discussed. The adsorption data fit well with the Freundlich model, indicating the heterogeneity of the resins surface. It could be seen from the experimental results that the adsorption capacity increased with the increase in the total surface concentration of oxygen-containing groups. The pH dependence and the effects of ionic strength were also discussed. The kinetic adsorption data fit well with the pseudo-second order model, and the results showed that the surface oxygen-containing groups have little effect on the adsorption rate.
文摘A geometrical definition, fractal dimension, was introduced in this study to evaluate copper adsorption in wood treated with copper-containing preservatives. It is based on the assumption that some copper would compete the hydroxyl groups in wood cell wall with water molecules, and therefore influence the fractal dimension of internal wood surfaces revealed by the moisture adsorption in wood. Southern yellow pine (Pinus spp.) specimens were treated with different concentrations of copper ethanolamine (Cu-EA) solution to obtain different copper retention levels. Then the adsorption isotherms of untreated and Cu-EA treated specimens were determined at 4, 15, 30, and 40 ℃ to provide the source data for fractal dimension calculation. The results showed that, at all temperatures, the fractal dimension of the internal wood surfaces had a decreasing trend with increasing copper retention. That is, the internal spaces in wood become 搕hinner?due to the copper adsorption on some hydroxyl groups in wood cell wall. The correlation between the fractal dimension and adsorbed copper ions makes it possible to evaluate the copper adsorption in wood cell wall.