To develop a depth filter based on the electrostatic adsorption principle, positively charged microporous ceramic membrane was prepared from a diatomaceous earth ceramic membrane.The internal surface of the highly por...To develop a depth filter based on the electrostatic adsorption principle, positively charged microporous ceramic membrane was prepared from a diatomaceous earth ceramic membrane.The internal surface of the highly porous ceramic membrane was coated with uniformly distributed electropositive nano-Y2O3 coating. The dye removal performance was evaluated through pressurized filtration tests using Titan Yellow aqueous solution. It showed that positively charged microporous ceramic membrane exhibited a flow rate of 421 L/(m^2·hr) under the trans-membrane pressure of 0.03 bar. Moreover it could effectively remove Titan Yellow with feed concentration of 10 mg/L between pH 3 to 8. The removal rate increased with the enhancement of the surface charge properties with a maximum rejection of 99.6%. This study provides a new and feasible method of removing organic dyes in wastewater. It is convinced that there will be a broad market for the application of charged ceramic membrane in the field of dye removal or recovery from industry wastewater.展开更多
Adsorption of poly(L-lysine) on surface-attached poly(methacrylic acid) monolayers formed through in situ free radical polymerization was investigated. A strong "template effect" was observed for the adsorption ...Adsorption of poly(L-lysine) on surface-attached poly(methacrylic acid) monolayers formed through in situ free radical polymerization was investigated. A strong "template effect" was observed for the adsorption of poly(L-lysine) on poly(methacrylic acid) layers, which were perpendicularly grown from the surface of substrates. The adsorbed amount of poly(amino acid) increases linearly with the increase in initial layer thickness of poly(methacrylic acid) monolayers. In addition, the adsorbed poly(amino acid) is relatively stable in medium concentration of salt solution but can be completely released from the brush in high salt concentration.展开更多
In order to solve the problem of insufficient adsorption rate of droplets on the target back via aerial electrostatic spray,this study proposed a high-voltage electrostatic generator to charge the liquids in two isola...In order to solve the problem of insufficient adsorption rate of droplets on the target back via aerial electrostatic spray,this study proposed a high-voltage electrostatic generator to charge the liquids in two isolated water tanks with positive and negative charges respectively.A charge transfer loop was developed in space between the aerial electrostatic spray system and the ground.This method greatly enhanced the adsorption performance under outdoor conditions that 16.7%droplets density increased on the target front,a nearly fourfold destiny increased on the target back compared with the conventional UAV spray system.The target back-to-front ratio of droplet density was improved from 6.1%to 25.7%,which validated the satisfactory performance of the developed system.展开更多
The adsorption of weak polybase on oppositely charged planar surfaces has been investigated numerically by using the self-consistent field theory(SCFT). Particular attention was paid to the interplay of monomer-surf...The adsorption of weak polybase on oppositely charged planar surfaces has been investigated numerically by using the self-consistent field theory(SCFT). Particular attention was paid to the interplay of monomer-surface electrostatic and non-electrostatic interactions in the adsorption behaviors of weak polybase. In this study, the strength of monomer-surface non-electrostatic interactions was set to be no more than the thermal energy kBT. It was found from the numerical study that in the regime of low surface charge density of the substrate and low p H or high bulk degree of ionization, both the screeningenhanced and screening-reduced salt effects emerge. On the contrary, in the opposite regime, only the screening-reduced salt effect was observed. Moreover, the overall charge neutrality inside the adsorption layer was analyzed. The underlying mechanism governing the adsorption behaviors of weak polybase on oppositely charged surfaces was elucidated.展开更多
A study of nonlinear competitive adsorption equilibria of proteins is of fundamental importance in understanding the behavior of preparative chromatographic separation.This work describes the nonlinear binary protein ...A study of nonlinear competitive adsorption equilibria of proteins is of fundamental importance in understanding the behavior of preparative chromatographic separation.This work describes the nonlinear binary protein adsorption equilibria on ion exchangers by the statistical thermodynamic(ST)model.The single-component and binary protein adsorption isotherms of bovine hemoglobin(Hb)and bovine serum albumin(BSA)on SP Sepharose FF were determined by batch adsorption experiments in 0.05 mol/L sodium acetate buffer at three pH values(4.5,5.0 and 5.5)and three NaCl concentrations(0.05,0.10 and 0.15 mol/L)at pH 5.0.The ST model was found to depict the effects of pH and ionic strength on the single-component equilibria well,with model parameters depending on the pH and ionic strength.Moreover,the ST model gave acceptable fitting to the binary adsorption data with the fitted single-component model parameters,leading to the estimation of the binary ST model parameter.The effects of pH and ionic strength on the model parameters are reasonably interpreted by the electrostatic and thermodynamic theories.Results demonstrate the availability of the ST model for describing nonlinear competitive protein adsorption equilibria in the presence of two proteins.展开更多
The presence of pharmaceuticals in aquatic environments poses potential risks to the ecology and human health. This study investigated the removal of three widely detected and abundant pharmaceuticals, namely, ibupro...The presence of pharmaceuticals in aquatic environments poses potential risks to the ecology and human health. This study investigated the removal of three widely detected and abundant pharmaceuticals, namely, ibuprofen(IBU), diclofenac(DC), and sulfadiazine(SDZ), by two magnetic ion-exchange resins. The adsorption kinetics of the three adsorbates onto both resins was relatively fast and followed pseudo-second-order kinetics. Despite the different pore structures of the two resins, similar adsorption patterns of DC and SDZ were observed, implying the existence of an ion-exchange mechanism. IBU demonstrated a combination of interactions during the adsorption process. These interactions were dependent on the specific surface area and functional groups of the resin. The adsorption isotherm fittings verified the differences in the behavior of the three pharmaceuticals on the two magnetic ion-exchange resins. The presence of Cl-and SO2-4suppressed the adsorption amount, but with different inhibition levels for different adsorbates. This work facilitates the understanding of the adsorption behavior and mechanism of pharmaceuticals on magnetic ion-exchange resins.The results will expand the application of magnetic ion-exchange resins to the removal of pharmaceuticals in waters.展开更多
With the increasingly prominent energy and environmental issues,the supercapacitors,as a highly efficient and clean energy conversion and storage devices,meet the requirements well.However,it is still a challenge to e...With the increasingly prominent energy and environmental issues,the supercapacitors,as a highly efficient and clean energy conversion and storage devices,meet the requirements well.However,it is still a challenge to enhance the capacitance and energy density of supercapacitors.A novel and highly conductive dodecaborate/MXene composites have been designed for high performance supercapacitors.The surface charge property of MXene was modified by a simple ultrasonic treatment with ammonium ion,and the dodecaborate ion can be inserted into the inner surface of MXene by electrostatic adsorption.Due to the unique icosahedral cage conjugate structure formed by the B-B bond and the highly delocalized three-dimensionalπbond structure of the electrons,the negative charge is delocalied on the whole dodecaborate ion,which reduces the ability to bind to cations.Therefore,the cations can move easily,and the dodecaborate can act as a“lubricant”for ion diffusion between the MXene layers,which significantly improves the ion transfer rate of supercapacitors.The dodecaborate/MXene composites can achieve an extremely high specific capacitance of 366 F.g^-1 at a scan rate of 2 mV.s^-1,which is more than eight times higher than that of MXene(43 F1-)at the same scan rate.Our finding provides a novel route on the fabrication of the high performance supercapacitors.展开更多
Electrospun membranes are attracting interest as a drug delivery system because of their material composition flexibility and versatile drug loading.In this study,the electrospun membrane was loaded with doxorubicin(D...Electrospun membranes are attracting interest as a drug delivery system because of their material composition flexibility and versatile drug loading.In this study,the electrospun membrane was loaded with doxorubicin(DOX)via electrostatic adsorption for long-term drug delivery.DOX loading process was optimized by varying temperature,time,drug concentration,pH and ionic strength of solutions.The loading process did not impair the structural properties of the membrane.Next,we investigated the drug release kinetics using spectroscopic techniques.The composite membranes released 22%of the adsorbed DOX over the first 48 h,followed by a slower and sustained release over 4 weeks.The DOX release was sensitive to acidic solutions that the release rate at pH 6.0 was 1.27 times as that at pH 7.4.The DOX-loaded membranes were found to be cytotoxic to U-87 MG cells in vitro that decreased the cell viability from 82.92%to 25.49%from 24 to 72 h of coincubation.These membranes showed strong efficacy in suppressing tumour growth in vivo in glioblastoma-bearing mice that decreased the tumour volume by 77.33%compared with blank membrane-treated group on Day 20.In conclusion,we have developed an effective approach to load DOX within a clinically approved poly(L-lactic acid)/gelatine membrane for local and longterm delivery of DOX for the treatment of glioblastoma.展开更多
Aluminum oxide-hydroxide nanofibers,2 nm in diameter and approximately 250 nm long,are electroadhesively grafted onto glass microfibers,therefore forming a macroscopic assembly of alumina nanofibers on the second soli...Aluminum oxide-hydroxide nanofibers,2 nm in diameter and approximately 250 nm long,are electroadhesively grafted onto glass microfibers,therefore forming a macroscopic assembly of alumina nanofibers on the second solid in highly organized matter.The assembly can be viewed as a straight cylinder with rough surface and charge density of approximately 0.08 C/m^(2).This creates a significant electric field with negligible screening(ka≪1)in the region close to the surface of the assemblies.This field attracts nano-and micron-size particles from as far as 0.3 mm in less than a few seconds,many orders of magnitude greater than the conventional Derjaguin–Landau–Verwey–Overbeek theory that predicts only nanometer-scale effects arising from the presence of the surface.The strong electric field on the surface is then able to retain particles such as micron-size powdered activated carbon as well as much smaller particles such as fumed silica nanoparticles of 10–15 nm in diameter,viruses,atomically thick sheets of graphene oxide,latex spheres,RNA,DNA,proteins,and dyes.展开更多
Aluminum oxide-hydroxide nanolayer with a thickness of approximately 1.2 nm is electroadhesively deposited onto silicious support material with large surface area of about 50 m2/g,forming a highly electropositive comp...Aluminum oxide-hydroxide nanolayer with a thickness of approximately 1.2 nm is electroadhesively deposited onto silicious support material with large surface area of about 50 m2/g,forming a highly electropositive composite of boehmite nanolayer in the form of monocrystalline oxide/hydroxide(α-Al2O3·H2O)on the second electronegative solid.The composite can be viewed as a sphere with a rough surface and charge density of approximately 0.08 C/m2.This creates a significant electric field with negligible screening(ka1)in the region close to the surface of the nanocomposite.This field attracts nano-and micron-sized particles from as far as 200μm in a few seconds,many orders of magnitude greater than conventional Derjaguin–Landau–Verwey–Overbeek(DLVO)theory,which predicts only nanometer-scale effects arising from the presence of the surface.The strong electric field on the surface is then able to retain small particles such as viruses,atomically thin sheets of graphene oxide,RNA,DNA,proteins,dyes as well as heavy metals such as cobalt,arsenic,and lead.Alumina’s nanolayer surface can be further functionalized by adding other submicron or nano-sized particles to target a specific contaminant.An example is shown where alumina nanolayer is coated with nano-sized iron monohydrate to yield an arsenic sorbent that shows high sorption capacity.展开更多
Na-rich birnessite(NRB) was synthesized by a simple synthesis method and used as a high-efficiency adsorbent for the removal of ammonium ion(NH+4) from aqueous solution.In order to demonstrate the adsorption perf...Na-rich birnessite(NRB) was synthesized by a simple synthesis method and used as a high-efficiency adsorbent for the removal of ammonium ion(NH+4) from aqueous solution.In order to demonstrate the adsorption performance of the synthesized material,the effects of contact time,pH,initial ammonium ion concentration,and temperature were investigated.Adsorption kinetics showed that the adsorption behavior followed the pseudo second-order kinetic model.The equilibrium adsorption data were fitted to Langmuir and Freundlich adsorption models and the model parameters were evaluated.The monolayer adsorption capacity of the adsorbent,as obtained from the Langmuir isotherm,was 22.61 mg NH+4-N/g at283 K.Thermodynamic analyses showed that the adsorption was spontaneous and that it was also a physisorption process.Our data revealed that the higher NH+4adsorption capacity could be primarily attributed to the water absorption process and electrostatic interaction.Particularly,the high surface hydroxyl-content of NRB enables strong interactions with ammonium ion.The results obtained in this study illustrate that the NRB is expected to be an effective and economically viable adsorbent for ammonium ion removal from aqueous system.展开更多
Recent experiments indicate that metal intercalation is a very effective method to manipulate the graphene-adatom interaction and control metal nanostructure formation on graphene. A key question is mass transport, i....Recent experiments indicate that metal intercalation is a very effective method to manipulate the graphene-adatom interaction and control metal nanostructure formation on graphene. A key question is mass transport, i.e., how atoms deposited uniformly on graphene populate different areas depending on the local intercalation. Using first-principles calculations, we show that partially intercalated graphene, with a mixture of intercalated and pristine areas, can induce an alternating electric field because of the spatial variations in electron doping, and thus, an oscillatory electrostatic potential. This alternating field can change normal stochastic adatom diffusion to biased diffusion, leading to selective mass transport and consequent nucleation, on either the intercalated or pristine areas, depending on the charge state of the adatoms.展开更多
基金supported by the National Natural Science Foundation of China (No. 51202292)
文摘To develop a depth filter based on the electrostatic adsorption principle, positively charged microporous ceramic membrane was prepared from a diatomaceous earth ceramic membrane.The internal surface of the highly porous ceramic membrane was coated with uniformly distributed electropositive nano-Y2O3 coating. The dye removal performance was evaluated through pressurized filtration tests using Titan Yellow aqueous solution. It showed that positively charged microporous ceramic membrane exhibited a flow rate of 421 L/(m^2·hr) under the trans-membrane pressure of 0.03 bar. Moreover it could effectively remove Titan Yellow with feed concentration of 10 mg/L between pH 3 to 8. The removal rate increased with the enhancement of the surface charge properties with a maximum rejection of 99.6%. This study provides a new and feasible method of removing organic dyes in wastewater. It is convinced that there will be a broad market for the application of charged ceramic membrane in the field of dye removal or recovery from industry wastewater.
基金Funded by the National Natural Science Foundation of China(21576216)
文摘Adsorption of poly(L-lysine) on surface-attached poly(methacrylic acid) monolayers formed through in situ free radical polymerization was investigated. A strong "template effect" was observed for the adsorption of poly(L-lysine) on poly(methacrylic acid) layers, which were perpendicularly grown from the surface of substrates. The adsorbed amount of poly(amino acid) increases linearly with the increase in initial layer thickness of poly(methacrylic acid) monolayers. In addition, the adsorbed poly(amino acid) is relatively stable in medium concentration of salt solution but can be completely released from the brush in high salt concentration.
基金This study was financially supported by the Shandong Province Introduced the Top Talents‘One Case One Discussion’Special Funded Project(2018.01-2021.12)the Central Government Guided Local Science and Technology Development Special Fund‘Precision Agricultural Aviation Technology and Equipment Research and Development’Funded Project(2017.1-2019.12)+1 种基金the Shandong Province Dry Farming Intelligent Agricultural Machinery Equipment Collaborative Innovation Center Funded Project(2017.7-2020.12)the Zibo Science and Technology Development Plan Funding Project(Grant No.2018kj010073).
文摘In order to solve the problem of insufficient adsorption rate of droplets on the target back via aerial electrostatic spray,this study proposed a high-voltage electrostatic generator to charge the liquids in two isolated water tanks with positive and negative charges respectively.A charge transfer loop was developed in space between the aerial electrostatic spray system and the ground.This method greatly enhanced the adsorption performance under outdoor conditions that 16.7%droplets density increased on the target front,a nearly fourfold destiny increased on the target back compared with the conventional UAV spray system.The target back-to-front ratio of droplet density was improved from 6.1%to 25.7%,which validated the satisfactory performance of the developed system.
基金supported by the National Natural Science Foundation of China(Nos.21374052 and 11174163)K.C.Wong Magna Fund in Ningbo University
文摘The adsorption of weak polybase on oppositely charged planar surfaces has been investigated numerically by using the self-consistent field theory(SCFT). Particular attention was paid to the interplay of monomer-surface electrostatic and non-electrostatic interactions in the adsorption behaviors of weak polybase. In this study, the strength of monomer-surface non-electrostatic interactions was set to be no more than the thermal energy kBT. It was found from the numerical study that in the regime of low surface charge density of the substrate and low p H or high bulk degree of ionization, both the screeningenhanced and screening-reduced salt effects emerge. On the contrary, in the opposite regime, only the screening-reduced salt effect was observed. Moreover, the overall charge neutrality inside the adsorption layer was analyzed. The underlying mechanism governing the adsorption behaviors of weak polybase on oppositely charged surfaces was elucidated.
基金supported by the National Natural Science Foundation of China(Grant No.20636040)the Specialized Research Fund for the Doctoral Program of Higher Education(Grant No.20050056001).
文摘A study of nonlinear competitive adsorption equilibria of proteins is of fundamental importance in understanding the behavior of preparative chromatographic separation.This work describes the nonlinear binary protein adsorption equilibria on ion exchangers by the statistical thermodynamic(ST)model.The single-component and binary protein adsorption isotherms of bovine hemoglobin(Hb)and bovine serum albumin(BSA)on SP Sepharose FF were determined by batch adsorption experiments in 0.05 mol/L sodium acetate buffer at three pH values(4.5,5.0 and 5.5)and three NaCl concentrations(0.05,0.10 and 0.15 mol/L)at pH 5.0.The ST model was found to depict the effects of pH and ionic strength on the single-component equilibria well,with model parameters depending on the pH and ionic strength.Moreover,the ST model gave acceptable fitting to the binary adsorption data with the fitted single-component model parameters,leading to the estimation of the binary ST model parameter.The effects of pH and ionic strength on the model parameters are reasonably interpreted by the electrostatic and thermodynamic theories.Results demonstrate the availability of the ST model for describing nonlinear competitive protein adsorption equilibria in the presence of two proteins.
基金supported by the National Science Foundation of China (Grant No. 51278253)the Ministry of Water Resources' Special Funds for Scientific Research on Public Causes (No. 201201018)+1 种基金the Foundation of Jiangsu Collaborative Innovation Center of Biomedical Functional Materialsa project funded by the priority academic program development of Jiangsu Higher Education Institutions
文摘The presence of pharmaceuticals in aquatic environments poses potential risks to the ecology and human health. This study investigated the removal of three widely detected and abundant pharmaceuticals, namely, ibuprofen(IBU), diclofenac(DC), and sulfadiazine(SDZ), by two magnetic ion-exchange resins. The adsorption kinetics of the three adsorbates onto both resins was relatively fast and followed pseudo-second-order kinetics. Despite the different pore structures of the two resins, similar adsorption patterns of DC and SDZ were observed, implying the existence of an ion-exchange mechanism. IBU demonstrated a combination of interactions during the adsorption process. These interactions were dependent on the specific surface area and functional groups of the resin. The adsorption isotherm fittings verified the differences in the behavior of the three pharmaceuticals on the two magnetic ion-exchange resins. The presence of Cl-and SO2-4suppressed the adsorption amount, but with different inhibition levels for different adsorbates. This work facilitates the understanding of the adsorption behavior and mechanism of pharmaceuticals on magnetic ion-exchange resins.The results will expand the application of magnetic ion-exchange resins to the removal of pharmaceuticals in waters.
基金support from the National Natural Science Foundation of China(No.61674109)the National Key R&D Program of China(No.2016YFA0202400)+3 种基金the Natural Science Foundation of Jiangsu Province(No.BK20170059)the Beijing Natural Science Foundation(No.2182061)Science Foundation of China University of Petroleum,Beijing(No.2462019BJRC001)funded by the Collaborative Innovation Center of Suzhou Nano Science and Technology,the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD).
文摘With the increasingly prominent energy and environmental issues,the supercapacitors,as a highly efficient and clean energy conversion and storage devices,meet the requirements well.However,it is still a challenge to enhance the capacitance and energy density of supercapacitors.A novel and highly conductive dodecaborate/MXene composites have been designed for high performance supercapacitors.The surface charge property of MXene was modified by a simple ultrasonic treatment with ammonium ion,and the dodecaborate ion can be inserted into the inner surface of MXene by electrostatic adsorption.Due to the unique icosahedral cage conjugate structure formed by the B-B bond and the highly delocalized three-dimensionalπbond structure of the electrons,the negative charge is delocalied on the whole dodecaborate ion,which reduces the ability to bind to cations.Therefore,the cations can move easily,and the dodecaborate can act as a“lubricant”for ion diffusion between the MXene layers,which significantly improves the ion transfer rate of supercapacitors.The dodecaborate/MXene composites can achieve an extremely high specific capacitance of 366 F.g^-1 at a scan rate of 2 mV.s^-1,which is more than eight times higher than that of MXene(43 F1-)at the same scan rate.Our finding provides a novel route on the fabrication of the high performance supercapacitors.
基金supported by Tsinghua-Berkeley Shenzhen Institute.
文摘Electrospun membranes are attracting interest as a drug delivery system because of their material composition flexibility and versatile drug loading.In this study,the electrospun membrane was loaded with doxorubicin(DOX)via electrostatic adsorption for long-term drug delivery.DOX loading process was optimized by varying temperature,time,drug concentration,pH and ionic strength of solutions.The loading process did not impair the structural properties of the membrane.Next,we investigated the drug release kinetics using spectroscopic techniques.The composite membranes released 22%of the adsorbed DOX over the first 48 h,followed by a slower and sustained release over 4 weeks.The DOX release was sensitive to acidic solutions that the release rate at pH 6.0 was 1.27 times as that at pH 7.4.The DOX-loaded membranes were found to be cytotoxic to U-87 MG cells in vitro that decreased the cell viability from 82.92%to 25.49%from 24 to 72 h of coincubation.These membranes showed strong efficacy in suppressing tumour growth in vivo in glioblastoma-bearing mice that decreased the tumour volume by 77.33%compared with blank membrane-treated group on Day 20.In conclusion,we have developed an effective approach to load DOX within a clinically approved poly(L-lactic acid)/gelatine membrane for local and longterm delivery of DOX for the treatment of glioblastoma.
文摘Aluminum oxide-hydroxide nanofibers,2 nm in diameter and approximately 250 nm long,are electroadhesively grafted onto glass microfibers,therefore forming a macroscopic assembly of alumina nanofibers on the second solid in highly organized matter.The assembly can be viewed as a straight cylinder with rough surface and charge density of approximately 0.08 C/m^(2).This creates a significant electric field with negligible screening(ka≪1)in the region close to the surface of the assemblies.This field attracts nano-and micron-size particles from as far as 0.3 mm in less than a few seconds,many orders of magnitude greater than the conventional Derjaguin–Landau–Verwey–Overbeek theory that predicts only nanometer-scale effects arising from the presence of the surface.The strong electric field on the surface is then able to retain particles such as micron-size powdered activated carbon as well as much smaller particles such as fumed silica nanoparticles of 10–15 nm in diameter,viruses,atomically thick sheets of graphene oxide,latex spheres,RNA,DNA,proteins,and dyes.
文摘Aluminum oxide-hydroxide nanolayer with a thickness of approximately 1.2 nm is electroadhesively deposited onto silicious support material with large surface area of about 50 m2/g,forming a highly electropositive composite of boehmite nanolayer in the form of monocrystalline oxide/hydroxide(α-Al2O3·H2O)on the second electronegative solid.The composite can be viewed as a sphere with a rough surface and charge density of approximately 0.08 C/m2.This creates a significant electric field with negligible screening(ka1)in the region close to the surface of the nanocomposite.This field attracts nano-and micron-sized particles from as far as 200μm in a few seconds,many orders of magnitude greater than conventional Derjaguin–Landau–Verwey–Overbeek(DLVO)theory,which predicts only nanometer-scale effects arising from the presence of the surface.The strong electric field on the surface is then able to retain small particles such as viruses,atomically thin sheets of graphene oxide,RNA,DNA,proteins,dyes as well as heavy metals such as cobalt,arsenic,and lead.Alumina’s nanolayer surface can be further functionalized by adding other submicron or nano-sized particles to target a specific contaminant.An example is shown where alumina nanolayer is coated with nano-sized iron monohydrate to yield an arsenic sorbent that shows high sorption capacity.
基金supported by the National Natural Science Foundation of China(No.51278409)the Education Department of Shaanxi Province(No.15JS046)
文摘Na-rich birnessite(NRB) was synthesized by a simple synthesis method and used as a high-efficiency adsorbent for the removal of ammonium ion(NH+4) from aqueous solution.In order to demonstrate the adsorption performance of the synthesized material,the effects of contact time,pH,initial ammonium ion concentration,and temperature were investigated.Adsorption kinetics showed that the adsorption behavior followed the pseudo second-order kinetic model.The equilibrium adsorption data were fitted to Langmuir and Freundlich adsorption models and the model parameters were evaluated.The monolayer adsorption capacity of the adsorbent,as obtained from the Langmuir isotherm,was 22.61 mg NH+4-N/g at283 K.Thermodynamic analyses showed that the adsorption was spontaneous and that it was also a physisorption process.Our data revealed that the higher NH+4adsorption capacity could be primarily attributed to the water absorption process and electrostatic interaction.Particularly,the high surface hydroxyl-content of NRB enables strong interactions with ammonium ion.The results obtained in this study illustrate that the NRB is expected to be an effective and economically viable adsorbent for ammonium ion removal from aqueous system.
基金Acknowledgements We thank Dr. Jim Evans for many useful discussions. Work at Ames Laboratory was supported by the U.S. Department of Energy, Basic Energy Sciences, Division of Materials Science and Engineering, including a grant of computer time at the National Energy Research Scientific Computing Centre (NERSC) in Berkeley, CA under Contract No. DE-AC02-07CH11358. X. J. L. also acknowledges the support by the National Natural Science Foundation of China (No. 11574044) and Science and Technology Department of Jilin Province (No. 20150520088JH). H. Q. L. acknowledges support from National Natural Science Foundation of China (No. U1530401) and computational resource from the Beijing Computational Science Research Center.
文摘Recent experiments indicate that metal intercalation is a very effective method to manipulate the graphene-adatom interaction and control metal nanostructure formation on graphene. A key question is mass transport, i.e., how atoms deposited uniformly on graphene populate different areas depending on the local intercalation. Using first-principles calculations, we show that partially intercalated graphene, with a mixture of intercalated and pristine areas, can induce an alternating electric field because of the spatial variations in electron doping, and thus, an oscillatory electrostatic potential. This alternating field can change normal stochastic adatom diffusion to biased diffusion, leading to selective mass transport and consequent nucleation, on either the intercalated or pristine areas, depending on the charge state of the adatoms.