The effects of relative humidity (RH) on a printed circuit board finished with electroless nickel immersion gold (PCB-ENIG) under an adsorbed thin electrolyte layer (ATEL) were investigated in situ via the measurement...The effects of relative humidity (RH) on a printed circuit board finished with electroless nickel immersion gold (PCB-ENIG) under an adsorbed thin electrolyte layer (ATEL) were investigated in situ via the measurement of cathodic polarization curves, electrochemical impedance spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy to clearly elaborate the corrosion behavior of PCB-ENIG in the atmospheric environment. Results indicated that the cathodic process of PCB-ENIG under ATEL was dominated by the reduction of dissolved oxygen, corrosion products, and H2O. The cathodic current density of PCB-ENIG increased progressively with increasing RH. Moreover, its cathodic current density in the solution was greater than that under ATEL. This result demonstrated that the diffusion process was not the controlling step during the limiting reduction of cathodic oxygen. When the polarization potentials were located in a more negative region, the cathodic polarization current density gradually decreased under 75% and 85% RH. Notably, the anodic process became the controlling step in the extremely thin liquid film during the remainder of the experiment.展开更多
Interactions of potassium and calcium ions with four typical variable charge soils in South China were examined by measuring pK-0.5pCa value with a potassium ion-selective electrode and a calcium ion-selective electro...Interactions of potassium and calcium ions with four typical variable charge soils in South China were examined by measuring pK-0.5pCa value with a potassium ion-selective electrode and a calcium ion-selective electrode,and pK value with a potassium ion-selective electrode.The results showed that adsorption of potassium and calcium ions increased with soil suspension pH,and the tendency of the pK-0.5pCa value changing with pH differed with respect to pH range and potassium to calcium ratio.Adsorption of equal amount of calcium and potassium ions led to release of an identical number of protons,suggesting similar adsorption characteristics of these two ions when adsorbed by variable charge soils.Compared with red soil,latosol and lateritic red soil had higher adsorption selectivities for calcium ion.The red soil had a greater affinity for potassium ion than that for calcium ion at low concentration,which seems to result from its possession of 2:1 type minerals,such as vermiculite and mica with a high affinity for potassium ion.The results indicated that adsorption of potassium and calcium ions by the variable charge soils was chiefly caused by the electrostatic attraction between the cations and the soil surfaces.Moreover,it was found that sulfate could affect the adsorption by changing soil surface properties and by forming ion-pair.展开更多
SO 4 2- and Zn 2+ or Cd 2+ were added to three variable charge soils in different sequences. In one sequence sulfate was added first, and in the other, Zn 2+ or Cd 2+ ...SO 4 2- and Zn 2+ or Cd 2+ were added to three variable charge soils in different sequences. In one sequence sulfate was added first, and in the other, Zn 2+ or Cd 2+ first. The addition of sulfate to the system invariably caused an increase in adsorption of the heavy metal added, with the effect more remarkable when the soil reacted with the sulfate prior to the metal. The shift in pH 50 for both Zn and Cd adsorption was also comparatively larger in the first sequence of reactions. It was suggested that the increase in negative charge density and the resultant negative potential of the soil were the primary cause of the pronounced effect of sulfate on adsorption of Zn or Cd, and the formation of the ternary surface complex S SO 4 M might also play a role in the effect.展开更多
The adsorption and mechanism of Re(Ⅶ)on resin D318 were studied using chemical methods and IR spectrometry.At pH 5.2,the static and dynamic saturation adsorption capacities were 351.4 and 366.5 mg·g-1,respective...The adsorption and mechanism of Re(Ⅶ)on resin D318 were studied using chemical methods and IR spectrometry.At pH 5.2,the static and dynamic saturation adsorption capacities were 351.4 and 366.5 mg·g-1,respectively.The adsorption behavior obeyed the Freundlich empirical equation and the adsorption rate constant k298 was 6.37×10-4s-1.The desorption percentage was up to 99.7%when 2.0 mol·L-1KSCN was used for dynamic desorption.展开更多
The zero point of charge (ZPC) and the remaining charge σp at ZPC are two important parameters characterizing surface charge of red soils.Fourteen red soil samples of different soil type and parent material were trea...The zero point of charge (ZPC) and the remaining charge σp at ZPC are two important parameters characterizing surface charge of red soils.Fourteen red soil samples of different soil type and parent material were treated with dithionite-citrate-dicarbonate (DCB) and Na2CO3 respectively.ZPC and σp of the samples in three indifferent electrolytes (NaCl,Na2SO4,and NaH2PO4) were determined.Kaolinite was used as reference.The results showed that ZPC of red soils was affected by the composition of parent materials and clay minerals and in significantly positive correlation with the content of total iron oxide (Fet),free iron oxide (Fed),amorphous iron oxide (Feo),aluminum oxide (Alo) and clay,but it was negatively correlated with the content of total silica (Sit).The σp of red soils was also markedly influenced by mineral components.Organic components were also contributing factor to the value of σp.The surface charges of red soils were evidently affected by the constitution of the electrolytes.Specific adsorption of anions in the electrolytes tended to make the ZPC of red soils shift to a higher pH value and to increase positive surface charges of the soils,thus leading to change of the σp value and decrease of the remaining net negative charges,even to the soils becoming net positive charge carriers.The effect of phosphate anion was greater than that of sulfate ion.展开更多
This paper reports the effect of several competing anions on arsenate adsorption with maghemite nanoparticles. Sulphate (as SO4), nitrate (as NO3-N), phosphate (as PO4-P) ions and silicate-(as SiO2) were-studi...This paper reports the effect of several competing anions on arsenate adsorption with maghemite nanoparticles. Sulphate (as SO4), nitrate (as NO3-N), phosphate (as PO4-P) ions and silicate-(as SiO2) were-studied in dual solution with arsenate. Moreover, the combined effect of ions and other water characteristics were examined with a natural groundwater sample which was spiked with a certain amount of arsenate. Arsenate batch adsorption experiments were carried out with two different kinds of maghemite-a commercially, available one and a homemade one using the sol-gel orocess. Sulohate (≤250 mg.L-1) and nitrate (≤ 12 mg.L-1) had a neglivible effect onthe arsenate (0.5 mg.L-1) adsorption at pH 3. However, both phosphate (42.9 mg·L-1) and silicate (450 mg.L-j) had an adverse impact on arsenate (43 mg.L-1) adsorption at pH 7. Phosphate (41.5 mg.L-1) showed minimal competition with arsenate (0.5 mg.L-1), while silicate (410 mg.L-1) inhibition was insignificant for all studied As(V) concentrations at p.H 3. The removal of arsenate from the groundwater sample was as efficient as from labo-ratory water tor 0.3 mgL -1 AS(V) botll at pH3 and pH7.展开更多
Our previous studies on bovine serum albumin (BSA) adsorption to diethylaminoethyl dextran (DEAE dextran, DexD, grafting-ligand) and DEAE (D, surface-ligand) modified Sepharose FF resins found that all the graft...Our previous studies on bovine serum albumin (BSA) adsorption to diethylaminoethyl dextran (DEAE dextran, DexD, grafting-ligand) and DEAE (D, surface-ligand) modified Sepharose FF resins found that all the grafted resins (FF-DexD and FF-D-DexD) exhibited extremely fast uptake rate (effective diffusivity, De, De/Do 〉 1.4), which was six times greater than the ungrafted resins (De/Do 〈 0.3). In this work, the influence of ionic strength (IS) on 6 typical DEAE dextran-grafted resins was investigated. Bath adsorption equilibria and kinetics, breakthrough, and linear gradient elution experiments were conducted. Commercial DEAE Sepharose FF was used for comparison. It is found that protein adsorption capacities on DEAE dextran-FF resins and the commercial resin decreased with increasing IS, but DEAE dextran-FF resins exhibited much higher capacity sensitivity to salt concentration. Besides, steeper decrease of adsorption capacities could be obtained at higher graftingligand or surface-ligand density. It is worth noting that the facilitating role of surface-ligand to the "chain delivery" effect was weakened after adding salt, leading to the less improvement in uptake rate by increasing surface-ligand density at higher IS. Although the uptake rates of the DEAE dextran-FF resins increased first and then decreased with increasing fS, they kept the extremely high level of De values (De/Do 〉 1.1 ) at the their working/binding IS range. Moreover, the DEAE dextran-FF resin displayed much higher adsorption capacities and De values than commercial ungrafted resin in their working condition. Furthermore, the column results of DEAE dextran-FF resins presented higher dynamic binding capacities than and similar elution ISs with DEAE Sepharose FF to achieve similar (or even higher) recoveries suggest the excellent chromatographic column performance of the DEAE dextran-FF resins. Finally, both high recovery and purity of BSA and γ-globulin could be easily achieved using the typical DEAE dextran-FF column, FF-D60-DexD160, to separate their binary mixtures, by step gradient elution. The research has provided new insights into the practical application of the series of DEAE-dextran grafted resins in protein chromatography and proved their superiority.展开更多
The effect of sodium dodecylbenzenesulfonate (SDBS), an anionic surfactant used widely in household products and industrial processes, on saturated hydraulic conductivities (Ksat) of an Anthrosol saturated with sodium...The effect of sodium dodecylbenzenesulfonate (SDBS), an anionic surfactant used widely in household products and industrial processes, on saturated hydraulic conductivities (Ksat) of an Anthrosol saturated with sodium (Na-soil) or calcium (Ca-soil) was analyzed in a laboratory experiment using the constant head method, and adsorption and dispersion experiments were also conducted to infer the possible mechanisms of Ksat fluctuations. The results showed that SDBS was more intensely adsorbed in the Ca-soil than in the Na-soil. With an increase in the SDBS concentration, the stability of the Na-soil suspensions decreased when the SDBS concentration was less than 1.2 mmol L-1 and then above this concentration, increased markedly, while the stability of the Ca-soil suspensions increased gradually at all SDBS concentrations studied. With an increase in the SDBS concentration, the Ksat of the Na-soil increased, which resulted mainly from the increase of water channels in the soil because of the coagulation of the soil particles, while the Ksat of Ca-soil decreased mainly on account of the clogging of partial water channels by precipitated Ca(DBS)2 and the fine soil particles generated.展开更多
Modified peanut shell (MPS) was prepared by amination reaction with peanut shell (PS) as the starting material The sorption of Cr(VI) oxyanions on MPS in static and column tests were investigated. In addition, t...Modified peanut shell (MPS) was prepared by amination reaction with peanut shell (PS) as the starting material The sorption of Cr(VI) oxyanions on MPS in static and column tests were investigated. In addition, the sorption isotherm and kinetic models were applied to confirm the sorption capacity and the sorption mechanisms. BET surface area anysis showed the physicochemical characterist!cs of the samples. The results of zeta potential,Fourier transform infrared (FT-IR) and Raman spectra analysis illustrated that chemical adsorption and ion exi change are the potential sorption mechanism. The static sorption test showed that the maximum sorption capacity (qm) of MPS for Cr(VI) increased with temperature, which indicated that the Cr(VI) sorption rocess was endothermic. The saturated sorption capacity of Cr(VI) in the colunm sorption test was 138.34 mg.g-1, which accounted for 93.9% of the qmax at 25 ℃. The regeneration capacity of MPS was evaluated using HC1 solution as an eluent. The high regeneration efficiency (82.6%) validated the dominance of the ion exchange mechanism in the Cr(VI) sorption process with C1ions displacing Cr(VI) oxyanion on MPS. The Langmuir isotherm model showed a higher correlation coefficient than the other adsorption isotherm models. And in the kinetic study, a pseudo-second-order model fit the data best.展开更多
The remaining phosphorus (Prem), P concentration that remains in solution after shaking soil with 0.01 mol L-1 CaCl2 containing 60μg mL-1 P, is a very useful index for studies related to the chemistry of variable cha...The remaining phosphorus (Prem), P concentration that remains in solution after shaking soil with 0.01 mol L-1 CaCl2 containing 60μg mL-1 P, is a very useful index for studies related to the chemistry of variable charge soils. Although the Prem determination is a simple procedure, the possibility of estimating accurate values of this index from easily and/or routinely determined soil properties can be very useful for practical purposes. The present research evaluated the Prem estimation through multiple regression analysis in which routinely determined soil chemical data, soil clay content and soil pH measured in 1 mol L-1 NaF (pHNaF) figured as Prem predictor variables. The Prem can be estimated with acceptable accuracy using the above-mentioned approach, and pHNaF not only substitutes for clay content as a predictor variable but also confers more accuracy to the Prem estimates.展开更多
A model was established for anion electric adsorption on variable charge surfaces and an equation to describe the relationship of adsorption amount with equalibrium concentration and suspension pH was derived accordin...A model was established for anion electric adsorption on variable charge surfaces and an equation to describe the relationship of adsorption amount with equalibrium concentration and suspension pH was derived according to the principles of surface reaction between variable charge surface and anions.The adsorption behaviours of nitrate and chloride on variable charge soils were modelled and the results showed that the model could describe the adsorption of nitrate very well.展开更多
Adsorption kinetics in multi-component systems has been a subject of intensive research because it is of both theoretical and practical importance. In this paper, raw date palm seeds (RDPS) were investigated to asse...Adsorption kinetics in multi-component systems has been a subject of intensive research because it is of both theoretical and practical importance. In this paper, raw date palm seeds (RDPS) were investigated to assess the possible use of this raw material as an effective adsorbent for the removal of sulfate from aqueous solution. The influence of various parameters such as sulfate initial concentration, pH, adsorbent dose and stirring time has been studied for the adsorption of sulfate in batch mode. Effects of foreign anions on the adsorption of sulfate onto RDPS have been also investigated. The pseudo-second-order, Elovich and intraparticle diffusion kinetic models have been developed to predict the rate constants of adsorption and equilibrium capacities. The maximum adsorption capacity of sulfate (qe ≈3.2 mg/g) onto RDPS was reached for the initial sulfate concentration = 100 mg/L, pH - 3.5, adsorbent dose = 10 g/L and for a stirring intensity = 200 rpm at 25 ± 2 ℃. The results showed that the adsorption of sulfate onto this raw materials followed pseudo-second-order rate kinetic predicting a chemisorption process.展开更多
The TiO2-densified cellulose composite beads were activated by epichlorohydrin and coupled with diethylamine, to function as an anion exchanger for expanded bed chromatography. The adsorbent exhibited a favorable perf...The TiO2-densified cellulose composite beads were activated by epichlorohydrin and coupled with diethylamine, to function as an anion exchanger for expanded bed chromatography. The adsorbent exhibited a favorable performance of expanded bed adsorption for proteins, and therefore was applied to the expanded bed recovery of D-2-chloropropionic acid dehalogenase directly from the unclarified homogenate of Pseudomonas sp. NT21. The binding capacity of the dehalogenase was found to be 8.54U·ml^-1 adsorbent, and two active peaks were eluted respectively at 0.15mol·L^-1 and 0.3mol·L^-1 (NH4)2SO4. The result indicated that the overall enzyme yield was 68%, with a purification factor of 22. In comparison to other recovery processes, the yield of the expanded bed process rises at least 70%, simultaneously saving a great deal of operation time and costs.展开更多
We applied quantum mechanics/classical mechanics simulations to study excess-electron attachment and ionization of uridine monophosphate anion(d UMP-)in explicit aqueous solutions.We calculated vertical electron affin...We applied quantum mechanics/classical mechanics simulations to study excess-electron attachment and ionization of uridine monophosphate anion(d UMP-)in explicit aqueous solutions.We calculated vertical electron affinities(VEAs),adiabatic electron affinities(AEAs),vertical detachment energies(VDEs),vertical ionization energies(VIEs),and adiabatic ionization energies(AIEs)of the 40 structures obtained from molecular dynamic trajectory.The excess-electron and hole distributions were analyzed in electron attachment and ionization of aqueous d UMP^(-).The converged mean VEA(-0.31 e V)and AEA(2.13 e V)suggest that excess-electron can easily attach to d UMP^(-).The mean vertical(-0.50 e)and adiabatic(-0.62 e)excess-electron on uracil reveal that main excesselectrons are localized on nucleobases at the most snapshots.The distributions at several special snapshots demonstrate the excess-electron delocalization over nucleobases/ribose or ribose/phosphate group after the structural relaxations of d UMP^(2-)dianion.The VDE value(2.78 e V)indicates that d UMP2-dianion could be very stable.Moreover,the mean VIE is 8.13 eV which is in agreement with the previous calculation using solvation model.The hole distributions on uracil suggest that the nucleobases are easily ionized after the irradiation of high-energy rays.In vertical ionizations,the holes would be delocalized over uracil and ribose at several snapshots.Observing the adiabatic hole distributions,it can be found that electrons on phosphate group and holes on nucleobases can be transferred to ribose at the special snapshots in the structural relaxation of neutral species.展开更多
X-ray photoelectron spectroscopy(XPS)was adopted to elucidate sorption mechanism of phenol and p-nitrophenol onto a weakly anion exchanger D301.The distribution of specific forms of tertiary amino group on D301 was ob...X-ray photoelectron spectroscopy(XPS)was adopted to elucidate sorption mechanism of phenol and p-nitrophenol onto a weakly anion exchanger D301.The distribution of specific forms of tertiary amino group on D301 was obtained and effect of free tertiary amino group on phenol sorption onto D301 was discussed. The result indicated that the percent of the protonated tertiary amine group on polymeric matrix was much lower than the reference compound N,N-dimethylbenzylamine at an identical pH value in solution due to the much lower activity degree of hydrogen ion in inner resin phase than in the external solution. Less free amino group on D301 results in less sorption capacity of phenol and p-nitrophenol in an acidic solution. Under the experimental conditions both phenol sorption onto D301 can be explained as solid extraction and the distribution coefficient varies linearly with the content of free amino group on D301.展开更多
Removal of zinc from cyanide barren solution is obligatory for its reuse in leach process. Batch experiments were carried out to evaluate the adsorption capacity of resins under different experimental conditions, incl...Removal of zinc from cyanide barren solution is obligatory for its reuse in leach process. Batch experiments were carried out to evaluate the adsorption capacity of resins under different experimental conditions, including con- centration, resin amount, initial pH, contact time and temperature. More than 99% of adsorption was achieved under the optimal condition. High adsorption rates on the resin were observed at the beginning and plateau values were obtained in 60 rain. The thermodynamic parameters (free energy change AG, enthalpy change AS and entropy change AH) for the adsorption were evaluated, The adsorption kinetic mechanism was studied with four models. The experimental results show that the adsorption follows the Langmuir isotherm and the kinetics follows the pseudo-second-order model.展开更多
The present work aims to study the adsorption, determining the ability of phosphate to remove cationic dyes, MB (methylene blue) and CV (crystal violet) and an anionic dye, the MO (methyl orange). To explain the...The present work aims to study the adsorption, determining the ability of phosphate to remove cationic dyes, MB (methylene blue) and CV (crystal violet) and an anionic dye, the MO (methyl orange). To explain the important reduction of pollution parameters obtained from its use as a filter bed. Natural phosphate is contacted with an aqueous solution having a concentration of 20 mg/L for 90, 45 and 20 min respectively for the MB, CV and MO. Experimental results show that the phosphate totally eliminates the CV and the WB. While, the adsorption of MO is very low. The Langmuir isotherm applies to MB and MO while the adsorption of CV uses the Freundlich isotherm.展开更多
To separate MA (Am, Cm) and some fission product elements (FPs) such as Tc, Pd, Cs and Sr from high level liquid waste (HLLW) systematically, we have been studying an advanced aqueous partitioning process, which...To separate MA (Am, Cm) and some fission product elements (FPs) such as Tc, Pd, Cs and Sr from high level liquid waste (HLLW) systematically, we have been studying an advanced aqueous partitioning process, which uses selective adsorption as the separation method. For this process, we prepared several novel adsorbents which were immobilized in a porous sili- c^polymer composite support (SiO2-P). Adsorption and separation behavior of various elements was studied experimentally in detail. Small scale separation tests using simulated HLLW solutions were carried out. Pd(II) was strongly adsorbed by the AR-01 anion exchanger and effectively eluted off by using thiourea. Successful separation of Pd(ll) from simulated HLLW was achieved. Te(VII) also exhibited strong adsorption on AR-01 and could be eluted off by using U(IV) as a reductive eluent. Am(Ⅲ) presented significantly high adsorbability and selectivity onto R-BTP/SiOz-P adsorbents over various FPs including Ln(Ⅲ). The R-BTP adsorbents were fairly stable in 3 M HNO3, but instable against 7-irradiation-3M HNO3. An advanced par- titioning process consisting of three separation columns for the target elements separation from HLLW was proposed and the obtained experiment results indicated that the proposed process is essentially feasible.展开更多
The activities of neutral, anionic, and cationic Au(111), Au(100), surface towards NO adsorption have been studied by performing and Au(310) surfaces, as well as an Au adatom on Au(111) density functional theo...The activities of neutral, anionic, and cationic Au(111), Au(100), surface towards NO adsorption have been studied by performing and Au(310) surfaces, as well as an Au adatom on Au(111) density functional theory calculations. It was found that the activity of gold increases as the coordination number of the gold atoms decreases, and that the cationic surfaces are generally more active than the neutral and anionic surfaces. The activity of Au surfaces towards NO adsorption is attributable to the presence of low coordinated gold atoms and the concentration of positive charges on the surface. The results may enrich the understanding of NO adsorption on Au surfaces.展开更多
基金Project(51271032)supported by the National Natural Science Foundation of ChinaProject(2014CB643300)supported by the National Basic Research Program of ChinaProject supported by the National Environmental Corrosion Platform,China
文摘The effects of relative humidity (RH) on a printed circuit board finished with electroless nickel immersion gold (PCB-ENIG) under an adsorbed thin electrolyte layer (ATEL) were investigated in situ via the measurement of cathodic polarization curves, electrochemical impedance spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy to clearly elaborate the corrosion behavior of PCB-ENIG in the atmospheric environment. Results indicated that the cathodic process of PCB-ENIG under ATEL was dominated by the reduction of dissolved oxygen, corrosion products, and H2O. The cathodic current density of PCB-ENIG increased progressively with increasing RH. Moreover, its cathodic current density in the solution was greater than that under ATEL. This result demonstrated that the diffusion process was not the controlling step during the limiting reduction of cathodic oxygen. When the polarization potentials were located in a more negative region, the cathodic polarization current density gradually decreased under 75% and 85% RH. Notably, the anodic process became the controlling step in the extremely thin liquid film during the remainder of the experiment.
文摘Interactions of potassium and calcium ions with four typical variable charge soils in South China were examined by measuring pK-0.5pCa value with a potassium ion-selective electrode and a calcium ion-selective electrode,and pK value with a potassium ion-selective electrode.The results showed that adsorption of potassium and calcium ions increased with soil suspension pH,and the tendency of the pK-0.5pCa value changing with pH differed with respect to pH range and potassium to calcium ratio.Adsorption of equal amount of calcium and potassium ions led to release of an identical number of protons,suggesting similar adsorption characteristics of these two ions when adsorbed by variable charge soils.Compared with red soil,latosol and lateritic red soil had higher adsorption selectivities for calcium ion.The red soil had a greater affinity for potassium ion than that for calcium ion at low concentration,which seems to result from its possession of 2:1 type minerals,such as vermiculite and mica with a high affinity for potassium ion.The results indicated that adsorption of potassium and calcium ions by the variable charge soils was chiefly caused by the electrostatic attraction between the cations and the soil surfaces.Moreover,it was found that sulfate could affect the adsorption by changing soil surface properties and by forming ion-pair.
文摘SO 4 2- and Zn 2+ or Cd 2+ were added to three variable charge soils in different sequences. In one sequence sulfate was added first, and in the other, Zn 2+ or Cd 2+ first. The addition of sulfate to the system invariably caused an increase in adsorption of the heavy metal added, with the effect more remarkable when the soil reacted with the sulfate prior to the metal. The shift in pH 50 for both Zn and Cd adsorption was also comparatively larger in the first sequence of reactions. It was suggested that the increase in negative charge density and the resultant negative potential of the soil were the primary cause of the pronounced effect of sulfate on adsorption of Zn or Cd, and the formation of the ternary surface complex S SO 4 M might also play a role in the effect.
基金Supported by the National Natural Science Foundation of China (30972405) and the Natural Science Foundation of Zhejiang Province (Y3090531).
文摘The adsorption and mechanism of Re(Ⅶ)on resin D318 were studied using chemical methods and IR spectrometry.At pH 5.2,the static and dynamic saturation adsorption capacities were 351.4 and 366.5 mg·g-1,respectively.The adsorption behavior obeyed the Freundlich empirical equation and the adsorption rate constant k298 was 6.37×10-4s-1.The desorption percentage was up to 99.7%when 2.0 mol·L-1KSCN was used for dynamic desorption.
基金Project supported by the National Natural Science Fundation of China
文摘The zero point of charge (ZPC) and the remaining charge σp at ZPC are two important parameters characterizing surface charge of red soils.Fourteen red soil samples of different soil type and parent material were treated with dithionite-citrate-dicarbonate (DCB) and Na2CO3 respectively.ZPC and σp of the samples in three indifferent electrolytes (NaCl,Na2SO4,and NaH2PO4) were determined.Kaolinite was used as reference.The results showed that ZPC of red soils was affected by the composition of parent materials and clay minerals and in significantly positive correlation with the content of total iron oxide (Fet),free iron oxide (Fed),amorphous iron oxide (Feo),aluminum oxide (Alo) and clay,but it was negatively correlated with the content of total silica (Sit).The σp of red soils was also markedly influenced by mineral components.Organic components were also contributing factor to the value of σp.The surface charges of red soils were evidently affected by the constitution of the electrolytes.Specific adsorption of anions in the electrolytes tended to make the ZPC of red soils shift to a higher pH value and to increase positive surface charges of the soils,thus leading to change of the σp value and decrease of the remaining net negative charges,even to the soils becoming net positive charge carriers.The effect of phosphate anion was greater than that of sulfate ion.
文摘This paper reports the effect of several competing anions on arsenate adsorption with maghemite nanoparticles. Sulphate (as SO4), nitrate (as NO3-N), phosphate (as PO4-P) ions and silicate-(as SiO2) were-studied in dual solution with arsenate. Moreover, the combined effect of ions and other water characteristics were examined with a natural groundwater sample which was spiked with a certain amount of arsenate. Arsenate batch adsorption experiments were carried out with two different kinds of maghemite-a commercially, available one and a homemade one using the sol-gel orocess. Sulohate (≤250 mg.L-1) and nitrate (≤ 12 mg.L-1) had a neglivible effect onthe arsenate (0.5 mg.L-1) adsorption at pH 3. However, both phosphate (42.9 mg·L-1) and silicate (450 mg.L-j) had an adverse impact on arsenate (43 mg.L-1) adsorption at pH 7. Phosphate (41.5 mg.L-1) showed minimal competition with arsenate (0.5 mg.L-1), while silicate (410 mg.L-1) inhibition was insignificant for all studied As(V) concentrations at p.H 3. The removal of arsenate from the groundwater sample was as efficient as from labo-ratory water tor 0.3 mgL -1 AS(V) botll at pH3 and pH7.
基金Supported by the National Natural Science Foundation of China(21406160,21621004)
文摘Our previous studies on bovine serum albumin (BSA) adsorption to diethylaminoethyl dextran (DEAE dextran, DexD, grafting-ligand) and DEAE (D, surface-ligand) modified Sepharose FF resins found that all the grafted resins (FF-DexD and FF-D-DexD) exhibited extremely fast uptake rate (effective diffusivity, De, De/Do 〉 1.4), which was six times greater than the ungrafted resins (De/Do 〈 0.3). In this work, the influence of ionic strength (IS) on 6 typical DEAE dextran-grafted resins was investigated. Bath adsorption equilibria and kinetics, breakthrough, and linear gradient elution experiments were conducted. Commercial DEAE Sepharose FF was used for comparison. It is found that protein adsorption capacities on DEAE dextran-FF resins and the commercial resin decreased with increasing IS, but DEAE dextran-FF resins exhibited much higher capacity sensitivity to salt concentration. Besides, steeper decrease of adsorption capacities could be obtained at higher graftingligand or surface-ligand density. It is worth noting that the facilitating role of surface-ligand to the "chain delivery" effect was weakened after adding salt, leading to the less improvement in uptake rate by increasing surface-ligand density at higher IS. Although the uptake rates of the DEAE dextran-FF resins increased first and then decreased with increasing fS, they kept the extremely high level of De values (De/Do 〉 1.1 ) at the their working/binding IS range. Moreover, the DEAE dextran-FF resin displayed much higher adsorption capacities and De values than commercial ungrafted resin in their working condition. Furthermore, the column results of DEAE dextran-FF resins presented higher dynamic binding capacities than and similar elution ISs with DEAE Sepharose FF to achieve similar (or even higher) recoveries suggest the excellent chromatographic column performance of the DEAE dextran-FF resins. Finally, both high recovery and purity of BSA and γ-globulin could be easily achieved using the typical DEAE dextran-FF column, FF-D60-DexD160, to separate their binary mixtures, by step gradient elution. The research has provided new insights into the practical application of the series of DEAE-dextran grafted resins in protein chromatography and proved their superiority.
基金Project supported by the Science and Technology Committee, Shanghai Municipality (No.02DJ14046).
文摘The effect of sodium dodecylbenzenesulfonate (SDBS), an anionic surfactant used widely in household products and industrial processes, on saturated hydraulic conductivities (Ksat) of an Anthrosol saturated with sodium (Na-soil) or calcium (Ca-soil) was analyzed in a laboratory experiment using the constant head method, and adsorption and dispersion experiments were also conducted to infer the possible mechanisms of Ksat fluctuations. The results showed that SDBS was more intensely adsorbed in the Ca-soil than in the Na-soil. With an increase in the SDBS concentration, the stability of the Na-soil suspensions decreased when the SDBS concentration was less than 1.2 mmol L-1 and then above this concentration, increased markedly, while the stability of the Ca-soil suspensions increased gradually at all SDBS concentrations studied. With an increase in the SDBS concentration, the Ksat of the Na-soil increased, which resulted mainly from the increase of water channels in the soil because of the coagulation of the soil particles, while the Ksat of Ca-soil decreased mainly on account of the clogging of partial water channels by precipitated Ca(DBS)2 and the fine soil particles generated.
基金Supported by the Independent Innovation Foundation of Shandong University(2012TS036)
文摘Modified peanut shell (MPS) was prepared by amination reaction with peanut shell (PS) as the starting material The sorption of Cr(VI) oxyanions on MPS in static and column tests were investigated. In addition, the sorption isotherm and kinetic models were applied to confirm the sorption capacity and the sorption mechanisms. BET surface area anysis showed the physicochemical characterist!cs of the samples. The results of zeta potential,Fourier transform infrared (FT-IR) and Raman spectra analysis illustrated that chemical adsorption and ion exi change are the potential sorption mechanism. The static sorption test showed that the maximum sorption capacity (qm) of MPS for Cr(VI) increased with temperature, which indicated that the Cr(VI) sorption rocess was endothermic. The saturated sorption capacity of Cr(VI) in the colunm sorption test was 138.34 mg.g-1, which accounted for 93.9% of the qmax at 25 ℃. The regeneration capacity of MPS was evaluated using HC1 solution as an eluent. The high regeneration efficiency (82.6%) validated the dominance of the ion exchange mechanism in the Cr(VI) sorption process with C1ions displacing Cr(VI) oxyanion on MPS. The Langmuir isotherm model showed a higher correlation coefficient than the other adsorption isotherm models. And in the kinetic study, a pseudo-second-order model fit the data best.
基金Project supported by the State of Sao Paulo Research Foundation-FAPESP, Brazil (No. 98/01502-8).
文摘The remaining phosphorus (Prem), P concentration that remains in solution after shaking soil with 0.01 mol L-1 CaCl2 containing 60μg mL-1 P, is a very useful index for studies related to the chemistry of variable charge soils. Although the Prem determination is a simple procedure, the possibility of estimating accurate values of this index from easily and/or routinely determined soil properties can be very useful for practical purposes. The present research evaluated the Prem estimation through multiple regression analysis in which routinely determined soil chemical data, soil clay content and soil pH measured in 1 mol L-1 NaF (pHNaF) figured as Prem predictor variables. The Prem can be estimated with acceptable accuracy using the above-mentioned approach, and pHNaF not only substitutes for clay content as a predictor variable but also confers more accuracy to the Prem estimates.
文摘A model was established for anion electric adsorption on variable charge surfaces and an equation to describe the relationship of adsorption amount with equalibrium concentration and suspension pH was derived according to the principles of surface reaction between variable charge surface and anions.The adsorption behaviours of nitrate and chloride on variable charge soils were modelled and the results showed that the model could describe the adsorption of nitrate very well.
文摘Adsorption kinetics in multi-component systems has been a subject of intensive research because it is of both theoretical and practical importance. In this paper, raw date palm seeds (RDPS) were investigated to assess the possible use of this raw material as an effective adsorbent for the removal of sulfate from aqueous solution. The influence of various parameters such as sulfate initial concentration, pH, adsorbent dose and stirring time has been studied for the adsorption of sulfate in batch mode. Effects of foreign anions on the adsorption of sulfate onto RDPS have been also investigated. The pseudo-second-order, Elovich and intraparticle diffusion kinetic models have been developed to predict the rate constants of adsorption and equilibrium capacities. The maximum adsorption capacity of sulfate (qe ≈3.2 mg/g) onto RDPS was reached for the initial sulfate concentration = 100 mg/L, pH - 3.5, adsorbent dose = 10 g/L and for a stirring intensity = 200 rpm at 25 ± 2 ℃. The results showed that the adsorption of sulfate onto this raw materials followed pseudo-second-order rate kinetic predicting a chemisorption process.
基金the Natural Science Foundation of Ningbo (No.2005A610018).ACKN0WLEDGEMENTS The authors would like to thank Mr. Qi Nan for taking part in this study, and for financial support by the Natural Science Foundation of Ningbo. Discussion with Dr. Lin Dong-Qiang has been helpful and is appreciated.
文摘The TiO2-densified cellulose composite beads were activated by epichlorohydrin and coupled with diethylamine, to function as an anion exchanger for expanded bed chromatography. The adsorbent exhibited a favorable performance of expanded bed adsorption for proteins, and therefore was applied to the expanded bed recovery of D-2-chloropropionic acid dehalogenase directly from the unclarified homogenate of Pseudomonas sp. NT21. The binding capacity of the dehalogenase was found to be 8.54U·ml^-1 adsorbent, and two active peaks were eluted respectively at 0.15mol·L^-1 and 0.3mol·L^-1 (NH4)2SO4. The result indicated that the overall enzyme yield was 68%, with a purification factor of 22. In comparison to other recovery processes, the yield of the expanded bed process rises at least 70%, simultaneously saving a great deal of operation time and costs.
基金supported by the National Natural Science Foundation of China(No.22173014,No.21773226,and No.21873100)Open Fund of the State Key Laboratory of Molecular Reaction Dynamics in Dalian Institute of Chemical Physics,Chinese Academy of Sciences。
文摘We applied quantum mechanics/classical mechanics simulations to study excess-electron attachment and ionization of uridine monophosphate anion(d UMP-)in explicit aqueous solutions.We calculated vertical electron affinities(VEAs),adiabatic electron affinities(AEAs),vertical detachment energies(VDEs),vertical ionization energies(VIEs),and adiabatic ionization energies(AIEs)of the 40 structures obtained from molecular dynamic trajectory.The excess-electron and hole distributions were analyzed in electron attachment and ionization of aqueous d UMP^(-).The converged mean VEA(-0.31 e V)and AEA(2.13 e V)suggest that excess-electron can easily attach to d UMP^(-).The mean vertical(-0.50 e)and adiabatic(-0.62 e)excess-electron on uracil reveal that main excesselectrons are localized on nucleobases at the most snapshots.The distributions at several special snapshots demonstrate the excess-electron delocalization over nucleobases/ribose or ribose/phosphate group after the structural relaxations of d UMP^(2-)dianion.The VDE value(2.78 e V)indicates that d UMP2-dianion could be very stable.Moreover,the mean VIE is 8.13 eV which is in agreement with the previous calculation using solvation model.The hole distributions on uracil suggest that the nucleobases are easily ionized after the irradiation of high-energy rays.In vertical ionizations,the holes would be delocalized over uracil and ribose at several snapshots.Observing the adiabatic hole distributions,it can be found that electrons on phosphate group and holes on nucleobases can be transferred to ribose at the special snapshots in the structural relaxation of neutral species.
基金National Natural Science Funding (20504012) and Natural Science Funding of Jiangsu Province (BK2004415)
文摘X-ray photoelectron spectroscopy(XPS)was adopted to elucidate sorption mechanism of phenol and p-nitrophenol onto a weakly anion exchanger D301.The distribution of specific forms of tertiary amino group on D301 was obtained and effect of free tertiary amino group on phenol sorption onto D301 was discussed. The result indicated that the percent of the protonated tertiary amine group on polymeric matrix was much lower than the reference compound N,N-dimethylbenzylamine at an identical pH value in solution due to the much lower activity degree of hydrogen ion in inner resin phase than in the external solution. Less free amino group on D301 results in less sorption capacity of phenol and p-nitrophenol in an acidic solution. Under the experimental conditions both phenol sorption onto D301 can be explained as solid extraction and the distribution coefficient varies linearly with the content of free amino group on D301.
基金Supported by Shandong provincial Natural Science Foundation,China(ZR2013EEM005)the High Education Science Technology Program of Shandong Province,China(J12LA04)
文摘Removal of zinc from cyanide barren solution is obligatory for its reuse in leach process. Batch experiments were carried out to evaluate the adsorption capacity of resins under different experimental conditions, including con- centration, resin amount, initial pH, contact time and temperature. More than 99% of adsorption was achieved under the optimal condition. High adsorption rates on the resin were observed at the beginning and plateau values were obtained in 60 rain. The thermodynamic parameters (free energy change AG, enthalpy change AS and entropy change AH) for the adsorption were evaluated, The adsorption kinetic mechanism was studied with four models. The experimental results show that the adsorption follows the Langmuir isotherm and the kinetics follows the pseudo-second-order model.
文摘The present work aims to study the adsorption, determining the ability of phosphate to remove cationic dyes, MB (methylene blue) and CV (crystal violet) and an anionic dye, the MO (methyl orange). To explain the important reduction of pollution parameters obtained from its use as a filter bed. Natural phosphate is contacted with an aqueous solution having a concentration of 20 mg/L for 90, 45 and 20 min respectively for the MB, CV and MO. Experimental results show that the phosphate totally eliminates the CV and the WB. While, the adsorption of MO is very low. The Langmuir isotherm applies to MB and MO while the adsorption of CV uses the Freundlich isotherm.
基金supported by the National Natural Science Foundation of China (91026019,91126006)
文摘To separate MA (Am, Cm) and some fission product elements (FPs) such as Tc, Pd, Cs and Sr from high level liquid waste (HLLW) systematically, we have been studying an advanced aqueous partitioning process, which uses selective adsorption as the separation method. For this process, we prepared several novel adsorbents which were immobilized in a porous sili- c^polymer composite support (SiO2-P). Adsorption and separation behavior of various elements was studied experimentally in detail. Small scale separation tests using simulated HLLW solutions were carried out. Pd(II) was strongly adsorbed by the AR-01 anion exchanger and effectively eluted off by using thiourea. Successful separation of Pd(ll) from simulated HLLW was achieved. Te(VII) also exhibited strong adsorption on AR-01 and could be eluted off by using U(IV) as a reductive eluent. Am(Ⅲ) presented significantly high adsorbability and selectivity onto R-BTP/SiOz-P adsorbents over various FPs including Ln(Ⅲ). The R-BTP adsorbents were fairly stable in 3 M HNO3, but instable against 7-irradiation-3M HNO3. An advanced par- titioning process consisting of three separation columns for the target elements separation from HLLW was proposed and the obtained experiment results indicated that the proposed process is essentially feasible.
基金supported by the National Natural Science Foundation of China (20873076 and 20873075)
文摘The activities of neutral, anionic, and cationic Au(111), Au(100), surface towards NO adsorption have been studied by performing and Au(310) surfaces, as well as an Au adatom on Au(111) density functional theory calculations. It was found that the activity of gold increases as the coordination number of the gold atoms decreases, and that the cationic surfaces are generally more active than the neutral and anionic surfaces. The activity of Au surfaces towards NO adsorption is attributable to the presence of low coordinated gold atoms and the concentration of positive charges on the surface. The results may enrich the understanding of NO adsorption on Au surfaces.