In this study,the removal of monovalent and divalent cations,Nat,Kt,Mg2t,and Ca2t,in a diluted solution from Chott-El Jerid Lake,Tunisia,was investigated with the electrodialysis technique.The process was tested using...In this study,the removal of monovalent and divalent cations,Nat,Kt,Mg2t,and Ca2t,in a diluted solution from Chott-El Jerid Lake,Tunisia,was investigated with the electrodialysis technique.The process was tested using two cation-exchange membranes:sulfonated polyether sulfone cross-linked with 10%hexamethylenediamine(HEXCl)and sulfonated polyether sulfone grafted with octylamine(S-PESOS).The commercially available membrane Nafion®was used for comparison.The results showed that Nafion®and S-PESOS membranes had similar removal behaviors,and the investigated cations were ranked in the following descending order in terms of their demineralization rates:Nat>Ca2t>Mg2t>Kt.Divalent cations were more effectively removed by HEXCl than by monovalent cations.The plots based on the WebereMorris model showed a strong linearity.This reveals that intra-particle diffusion was not the removal rate-determining step,and the removal process was controlled by two or more concurrent mechanisms.The Boyd plots did not pass through their origin,and the sole controlling step was determined by film-diffusion resistance,especially after a long period of electrodialysis.Additionally,a semi-empirical model was established to simulate the temporal variation of the treatment process,and the physical significance and values of model parameters were compared for the three membranes.The findings of this study indicate that HEXCl and S-PESOS membranes can be efficiently utilized for water softening,especially when effluents are highly loaded with calcium and magnesium ions.展开更多
The influences of particle size,shape,and catalyst distribution on the reactivity and hydrocarbon product selectivity of a cobalt-based catalyst for Fischer-Tropsch synthesis were investigated in the present work.A se...The influences of particle size,shape,and catalyst distribution on the reactivity and hydrocarbon product selectivity of a cobalt-based catalyst for Fischer-Tropsch synthesis were investigated in the present work.A self-consistent kinetic model for Fischer-Tropsch reaction proposed here was found to correlate experimental data well and hence was used to describe the consumption rates of reactants and formation rates of hydrocarbon products.The perturbed-chain statistical associating fluid theory equation of state was used to describe vapor-liquid equilibrium behavior associated with Fischer-Tropsch reaction.Local interaction between intraparticle diffusion and Fischer-Tropsch reaction was investigated in detail.Results showed that in order to avoid the adverse influence of intraparticle diffusional limitations on catalyst reactivity and product selectivity,the use of small particles is necessary.Large eggshell spherical particles are shown to keep the original catalyst reactivity and enhance the selectivity of heavy hydrocarbon products.The suitable layer thickness for a spherical particle with a diameter of 2 mm is nearly 0.15 mm.With the same outer diameter of 2 mm,the catalyst reactivity and heavy product selectivity of hollow cylindrical particles with a layer thickness of 0.25 mm are found to be larger than eggshell spherical particles.From the viewpoint of catalytic performance,hollow cylindrical particles are a better choice for industrial applications.展开更多
Over 70%of the treated contaminated water at the Fukushima Daiichi Nuclear Power Station contains radionuclides beyond the regulatory standard for discharge that need to be re-purified.Technetium-99(^(99)Tc),mainly in...Over 70%of the treated contaminated water at the Fukushima Daiichi Nuclear Power Station contains radionuclides beyond the regulatory standard for discharge that need to be re-purified.Technetium-99(^(99)Tc),mainly in the form of pertechnetate Tc(VII)O_(4)^(-),is one of the main sources of long-term radiotoxicity that jeopardizes the environment and human health.Herein,we used a series of dicationic pyridinium(DCP)derivative groups(–Py^(+)C_(n)H_(2n)N^(+)Me_(3),n=2,3,and 5)to modify commercial Reillex 425 resins containing tertiary pyridyl groups to improve the adsorption performance of rhenium(Re,an analog of radioactive Tc)and Tc.As the quaternary pyridinium and ammonium sites in one DCP group can adsorb ReO_(4)^(-) simultaneously,DCP-modified Reillex 425(Reillex-Cn)exhibited high maximum adsorption capacities for Re under neutral conditions.Adsorption capacities reached 344.8,416.7,and 588.2 mg g^(-)1 for Reillex 425-C2,Reillex 425-C3,and Reillex 425-C5,respectively.Intraparticle diffusion of ReO_(4)^(-)/TcO_(4)^(-) in Reillex 425-Cn was verified to be the rate-limiting step of adsorption.However,adsorption can be adjusted by the length of the alkyl spacers between the two positively charged N sites in DCP.–Py^(+)C_(2)H_(4)N^(+)Me_(3) significantly enhanced intraparticle diffusion compared to–Py^(+)C_(5)H_(10)N^(+)Me_(3).The two positive sites in–Py^(+)C_(2)H_(4)N^(+)Me_(3) would be laterally distributed,leading to a smaller steric hindrance for ReO_(4)–/TcO_(4)^(-) transport inside the microporous channels.Meanwhile,the longer alkyl spacers in–Py^(+)C_(5)H_(10)N^(+)Me_(3) formed hydrophobic microphases,repulsing the hydrated ReO_(4)–/TcO_(4)^(-) anions.Thus,the adsorptions of both ReO_(4)^(-) and TcO_(4)^(-) on Reillex 425-C2 were faster than those on Reillex 425-C5.Moreover,Reillex 425-Cn exhibited an exothermic nature,good selectivity,excellent reusability,and strong salinity tolerance.This study provides a simple strategy to enhance the Tc removal performance of adsorbents containing abundant micropores,which implies enormous environmental and economic benefits.展开更多
Control of N-nitrosodimethylamine(NDMA)in drinking water could be achieved by removing its precursors as one practical way.Herein,superfine powdered activated carbons with a diameter of about 1μm(SPACs)were successfu...Control of N-nitrosodimethylamine(NDMA)in drinking water could be achieved by removing its precursors as one practical way.Herein,superfine powdered activated carbons with a diameter of about 1μm(SPACs)were successfully prepared by grinding powdered activated carbon(PAC,D50=24.3μm)and applied to remove model NDMA precursors,i.e.ranitidine(RAN)and nizatidine(NIZ).Results fromgrain diameter experiments demonstrated that the absorption velocity increased dramatically with decreasing particle size,and the maximum increase in k2 was 26.8-folds for RAN and 33.4-folds for NIZ.Moreover,kinetic experiments explained that rapid absorption could be attributed to the acceleration of intraparticle diffusion due to the shortening of the diffusion path.Furthermore,performance comparison experiments suggested that the removal of RAN and NIZ(C_(0)=0.5 mg/L)could reach 61.3%and 60%,respectively,within 5 min,when the dosage of SAPC-1.1(D_(50)=1.1μm)was merely 5 mg/L,while PAC-24.3 could only eliminate 17.5%and 18.6%.The adsorption isotherm was well defined by Langmuir isotherm model,indicating that the adsorption of RAN/NIZ was a monolayer coverage process.The adsorption of RAN or NIZ by SAPC-1.1 and PAC-24.3 was strongly pH dependent,and high adsorption capacity could be observed under the condition of pH>pk_(a)+1.The coexistence of humic acid(HA)had no significant effect on the adsorption performance because RAN/NIZ may be coupled with HA and removed simultaneously.The coexistence of anions had little effect on the adsorption also.This study is expected to provide an alternative strategy for drinking water safety triggered by NDMA.展开更多
Adsorption is one of the most widely applied techniques for environmental remediation. Its kinetics are of great significance to evaluate the performance of a given adsorbent and gain insight into the underlying mecha...Adsorption is one of the most widely applied techniques for environmental remediation. Its kinetics are of great significance to evaluate the performance of a given adsorbent and gain insight into the underlying mechanisms. There are lots of references available concerning adsorption kinetics, and several mathematic models have been developed to describe adsorption reaction and diffusion processes. However, these models were frequently employed to fit the kinetic data in an unsuitable or improper manner. This is mainly because the boundary conditions of the associated models were, to a considerable extent, ignored for data modeling. Here we reviewed several widely-used adsorption kinetic models and paid more attention to their boundary conditions. We believe that the review is of certain significance and improvement for adsorption kinetic modeling.展开更多
文摘In this study,the removal of monovalent and divalent cations,Nat,Kt,Mg2t,and Ca2t,in a diluted solution from Chott-El Jerid Lake,Tunisia,was investigated with the electrodialysis technique.The process was tested using two cation-exchange membranes:sulfonated polyether sulfone cross-linked with 10%hexamethylenediamine(HEXCl)and sulfonated polyether sulfone grafted with octylamine(S-PESOS).The commercially available membrane Nafion®was used for comparison.The results showed that Nafion®and S-PESOS membranes had similar removal behaviors,and the investigated cations were ranked in the following descending order in terms of their demineralization rates:Nat>Ca2t>Mg2t>Kt.Divalent cations were more effectively removed by HEXCl than by monovalent cations.The plots based on the WebereMorris model showed a strong linearity.This reveals that intra-particle diffusion was not the removal rate-determining step,and the removal process was controlled by two or more concurrent mechanisms.The Boyd plots did not pass through their origin,and the sole controlling step was determined by film-diffusion resistance,especially after a long period of electrodialysis.Additionally,a semi-empirical model was established to simulate the temporal variation of the treatment process,and the physical significance and values of model parameters were compared for the three membranes.The findings of this study indicate that HEXCl and S-PESOS membranes can be efficiently utilized for water softening,especially when effluents are highly loaded with calcium and magnesium ions.
基金supported by the National Natural Science Foundation of China(21908234)the National Key Research&Development Program of China(2020YFB0606404)+1 种基金the Inner Mongolia Science and Technology Agency Program(2019CG058)Shanxi Province Natural Science Foundation(202103021223063).
文摘The influences of particle size,shape,and catalyst distribution on the reactivity and hydrocarbon product selectivity of a cobalt-based catalyst for Fischer-Tropsch synthesis were investigated in the present work.A self-consistent kinetic model for Fischer-Tropsch reaction proposed here was found to correlate experimental data well and hence was used to describe the consumption rates of reactants and formation rates of hydrocarbon products.The perturbed-chain statistical associating fluid theory equation of state was used to describe vapor-liquid equilibrium behavior associated with Fischer-Tropsch reaction.Local interaction between intraparticle diffusion and Fischer-Tropsch reaction was investigated in detail.Results showed that in order to avoid the adverse influence of intraparticle diffusional limitations on catalyst reactivity and product selectivity,the use of small particles is necessary.Large eggshell spherical particles are shown to keep the original catalyst reactivity and enhance the selectivity of heavy hydrocarbon products.The suitable layer thickness for a spherical particle with a diameter of 2 mm is nearly 0.15 mm.With the same outer diameter of 2 mm,the catalyst reactivity and heavy product selectivity of hollow cylindrical particles with a layer thickness of 0.25 mm are found to be larger than eggshell spherical particles.From the viewpoint of catalytic performance,hollow cylindrical particles are a better choice for industrial applications.
基金supported by the National Natural Science Foundation of China(Nos.51803205,11775214,and 21790371)China Scholarship Council(No.201906345006).
文摘Over 70%of the treated contaminated water at the Fukushima Daiichi Nuclear Power Station contains radionuclides beyond the regulatory standard for discharge that need to be re-purified.Technetium-99(^(99)Tc),mainly in the form of pertechnetate Tc(VII)O_(4)^(-),is one of the main sources of long-term radiotoxicity that jeopardizes the environment and human health.Herein,we used a series of dicationic pyridinium(DCP)derivative groups(–Py^(+)C_(n)H_(2n)N^(+)Me_(3),n=2,3,and 5)to modify commercial Reillex 425 resins containing tertiary pyridyl groups to improve the adsorption performance of rhenium(Re,an analog of radioactive Tc)and Tc.As the quaternary pyridinium and ammonium sites in one DCP group can adsorb ReO_(4)^(-) simultaneously,DCP-modified Reillex 425(Reillex-Cn)exhibited high maximum adsorption capacities for Re under neutral conditions.Adsorption capacities reached 344.8,416.7,and 588.2 mg g^(-)1 for Reillex 425-C2,Reillex 425-C3,and Reillex 425-C5,respectively.Intraparticle diffusion of ReO_(4)^(-)/TcO_(4)^(-) in Reillex 425-Cn was verified to be the rate-limiting step of adsorption.However,adsorption can be adjusted by the length of the alkyl spacers between the two positively charged N sites in DCP.–Py^(+)C_(2)H_(4)N^(+)Me_(3) significantly enhanced intraparticle diffusion compared to–Py^(+)C_(5)H_(10)N^(+)Me_(3).The two positive sites in–Py^(+)C_(2)H_(4)N^(+)Me_(3) would be laterally distributed,leading to a smaller steric hindrance for ReO_(4)–/TcO_(4)^(-) transport inside the microporous channels.Meanwhile,the longer alkyl spacers in–Py^(+)C_(5)H_(10)N^(+)Me_(3) formed hydrophobic microphases,repulsing the hydrated ReO_(4)–/TcO_(4)^(-) anions.Thus,the adsorptions of both ReO_(4)^(-) and TcO_(4)^(-) on Reillex 425-C2 were faster than those on Reillex 425-C5.Moreover,Reillex 425-Cn exhibited an exothermic nature,good selectivity,excellent reusability,and strong salinity tolerance.This study provides a simple strategy to enhance the Tc removal performance of adsorbents containing abundant micropores,which implies enormous environmental and economic benefits.
基金supported by the Key Technology Research and Development Program of Shandong(No.2020CXGC011406)the National Natural Science Foundation of China(No.22076091)the State Key Joint Laboratory of Environment Simulation and Pollution Control,China(No.21L01ESPC).
文摘Control of N-nitrosodimethylamine(NDMA)in drinking water could be achieved by removing its precursors as one practical way.Herein,superfine powdered activated carbons with a diameter of about 1μm(SPACs)were successfully prepared by grinding powdered activated carbon(PAC,D50=24.3μm)and applied to remove model NDMA precursors,i.e.ranitidine(RAN)and nizatidine(NIZ).Results fromgrain diameter experiments demonstrated that the absorption velocity increased dramatically with decreasing particle size,and the maximum increase in k2 was 26.8-folds for RAN and 33.4-folds for NIZ.Moreover,kinetic experiments explained that rapid absorption could be attributed to the acceleration of intraparticle diffusion due to the shortening of the diffusion path.Furthermore,performance comparison experiments suggested that the removal of RAN and NIZ(C_(0)=0.5 mg/L)could reach 61.3%and 60%,respectively,within 5 min,when the dosage of SAPC-1.1(D_(50)=1.1μm)was merely 5 mg/L,while PAC-24.3 could only eliminate 17.5%and 18.6%.The adsorption isotherm was well defined by Langmuir isotherm model,indicating that the adsorption of RAN/NIZ was a monolayer coverage process.The adsorption of RAN or NIZ by SAPC-1.1 and PAC-24.3 was strongly pH dependent,and high adsorption capacity could be observed under the condition of pH>pk_(a)+1.The coexistence of humic acid(HA)had no significant effect on the adsorption performance because RAN/NIZ may be coupled with HA and removed simultaneously.The coexistence of anions had little effect on the adsorption also.This study is expected to provide an alternative strategy for drinking water safety triggered by NDMA.
基金supported by the National Natural Science Foundation of China (No. 20504012)the New Century Excellent Talents in University of China (No. NCET-07-0421)
文摘Adsorption is one of the most widely applied techniques for environmental remediation. Its kinetics are of great significance to evaluate the performance of a given adsorbent and gain insight into the underlying mechanisms. There are lots of references available concerning adsorption kinetics, and several mathematic models have been developed to describe adsorption reaction and diffusion processes. However, these models were frequently employed to fit the kinetic data in an unsuitable or improper manner. This is mainly because the boundary conditions of the associated models were, to a considerable extent, ignored for data modeling. Here we reviewed several widely-used adsorption kinetic models and paid more attention to their boundary conditions. We believe that the review is of certain significance and improvement for adsorption kinetic modeling.
