The treatment and disposal of radioactive waste are presently facing great challenges.Spent ion exchange resins have become a focus of attention due to their high production and serious environmental risks.In this pap...The treatment and disposal of radioactive waste are presently facing great challenges.Spent ion exchange resins have become a focus of attention due to their high production and serious environmental risks.In this paper,a simplified model of cationic exchange resin is proposed,and the degradation processes of cationic resin monomer initiated by hydroxyl radicals(·OH)are clarified by combining statistical molecular fragmentation(SMF)model and density functional theory(DFT)calculations.The prediction of active sites indicates that the S-O bonds and the C-S bond of the sulfonic group are more likely to react during the degradation.The meta-position of the sulfonic group on the benzene ring is the most active site,and the benzene ring without the sulfonic group has a certain reactivity.The C11-C14 and C17-C20 bonds,on the carbon skeleton,are the most easily broken.It is also found that dihydroxy addition and elimination reactions play a major role in the process of desulfonation,carbon skeleton cleavage and benzene ring separation.The decomposition mechanisms found through the combination of physical models and chemical calculations,provide theoretical guidance for the treatment of complex polycyclic aromatic hydrocarbons.展开更多
In this study,we reported on the concept and practical use of cation exchange resin(CER)for removing anions in water via pretreating the CER with metal salts.The cation exchange resinsupported iron and magnesium oxide...In this study,we reported on the concept and practical use of cation exchange resin(CER)for removing anions in water via pretreating the CER with metal salts.The cation exchange resinsupported iron and magnesium oxides/hydroxides composite(FeMg/CER)was synthesized and introduced as a new and potential adsorbent for selective removal of nitrate ion in the water environment.Characteristics of FeMg/CER were determined by techniques such as Fouriertransform infrared spectroscopy,scanning electron microscopy,and Xray diffraction.The results showed that FeMg/CER material had a high nitrate adsorption capacity of 200 mg NO_(3)^()·g^(1)with a fast equilibrium adsorption time of 30 min at pH 5.In addition,it had good durability of at least 10 times of regeneration,which could be applied to practical water and wastewater treatment.展开更多
This study describes the kinetics and thermodynamics of the esterification of acidified oil with methanol catalyzed by sulfonated cation exchange resins(SCER). The effects of the mass ratio of methanol to acidified ...This study describes the kinetics and thermodynamics of the esterification of acidified oil with methanol catalyzed by sulfonated cation exchange resins(SCER). The effects of the mass ratio of methanol to acidified oil,reaction temperature,and catalyst loading were studied to optimize the conditions for maximum conversion of free fatty acids(FFAs). The results showed that the optimal conversion rate of FFAs was 91.87% at the mass ratio of methanol to acidified oil of 2.5:1.0,reaction temperature of 65.0 °C,catalyst loading of 5.0 g and reaction time of 8.0 h. The external and internal mass transfer resistances were negligible based on the experimental results and a pseudo-homogeneous kinetic model was proposed for the esterification. The activation energy and thermodynamic parameters including G,S and H were determined. The conversion rates of FFAs obtained from the established model were in good agreement with the experimental data.展开更多
The polystyrene cation exchange resin was exchanged by La 3+ and then were carbonized to make resin carbon material. The electrochemical properties of the resin carbon material as the electrode of the lithium ion...The polystyrene cation exchange resin was exchanged by La 3+ and then were carbonized to make resin carbon material. The electrochemical properties of the resin carbon material as the electrode of the lithium ion cell were investigated. The test results show that comparing with the polystyrene cation exchange resin without adulterating, the contents of hydrogen, oxygen and sulfur are changed obviously for the resin carbon material derived from the La 3+ adulterating polystyrene cation exchange resin. The contents of hydrogen and oxygen are increased, and the one of sulfur is decreased. The test results also indicate that it is more easily to form the stratum graphite minicrystal structure with bigger diameter for the La 3+ adulterating resin. According to the electrochemical test results, the electrode derived from La 3+ adulterating polystyrene cation exchange resin has much better electrochemical property, and the capacity of charge and discharge of the electrode is increased about 30 mAh·g -1 in average.展开更多
Strongly acidic cation exchange resin(1x1,H form)has been successfully used as a catalyst in synthesis of diphenyl N-benzyloxycarbonyl-1-aminobenzylphosphonate, N-benzyloxycarbonyl-1-aminobenzylphenylphosphinic acid a...Strongly acidic cation exchange resin(1x1,H form)has been successfully used as a catalyst in synthesis of diphenyl N-benzyloxycarbonyl-1-aminobenzylphosphonate, N-benzyloxycarbonyl-1-aminobenzylphenylphosphinic acid and N-p-tolylsulfonyl-1-aminobenzyl phenylphosphinic acid in high yields.展开更多
In this work, melamine-formaldehyde resin was cationized by adding modifiers so that the fibers closely bonded to improve their usability and the wet strength of paper was greatly improved. Triethanolamine and dimethy...In this work, melamine-formaldehyde resin was cationized by adding modifiers so that the fibers closely bonded to improve their usability and the wet strength of paper was greatly improved. Triethanolamine and dimethylamine were added to modify the melamine-formaldehyde resin,respectively.The mechanism of the cationized resin was explored and the possible chemical reactions were deduced. It was concluded that,with the use of triethanolamine,the most optimum product was obtained by hydroxymethylation for 30 min with a temperature of 85℃ and p H of 9. 0 where n( melamine) ∶ n( formaldehyde) ∶ n( methanol) ∶ n( triethanolamine) was 100 ∶ 330 ∶ 450 ∶ 15. With the combined use of dimethylamine and methanol,the optimal product was acquired by condensation for 30 min at a temperature of 50℃ and p H of 2. 0 at melamine, formaldehyde, methanol, and dimethylamine molar ratio of100∶ 330∶ 350∶ 20. With the only use of dimethylamine,the optimal product was obtained by condensation at melamine,formaldehyde,dimethylamine molar ratio of 100∶ 330∶ 10. The wet tensile strength of fruit-bagging paper was improved by adding cationized melamine-formaldehyde resin. The zeta potential,charge density,and conductivity of the melamine-formaldehyde resin were also studied.展开更多
2-Acryloxyacetophenone (AAP) was prepared and subjected to suspension polymerization with methyl methacrylate (MMA) using azobisisobutyronitrile (AIBN) as free radical initiator. The differently sulfonated AAP-M...2-Acryloxyacetophenone (AAP) was prepared and subjected to suspension polymerization with methyl methacrylate (MMA) using azobisisobutyronitrile (AIBN) as free radical initiator. The differently sulfonated AAP-MMA cross-linked copolymer cationic exchange resins were prepared by sulfonation with concentrated sulphuric acid at 70 ~C. Several characteristics of the prepared resins were evaluated, i.e. FTIR, the ion-exchange capacity (IEC), thermo gravimetric analysis (TGA), particle size distribution and microscopic morphology. The resin characteristics were altered with degree of sulfonation, providing that differently sulfonated resins could be prepared. The behavior of atenolol (ATL) loading and in vitro release in the USP stimulated gastric and intestinal fluids of the obtained resins were evaluated. The drug loaded in the resin increased with increasing degree of sulfonation and hence the drug binding site in resin employed. The drug release was lower from the resins with higher content of sulfonic group due to the increase in the diffusive path depth. The drug release was a little lower in stimulated gastric fluid (SGF) than in stimulated intestinal fluids (SIF). The basic groups, ionized to a little greater extent in SGF and preferred binding with the resin rather than releasing. Hence, the differently sulfonated resins could be utilized as novel carriers for drug delivery.展开更多
EVAL hollow fiber membrane adsorbents filled with powder D061-type cation exchange resin were prepared through dry-wet spinning process,using hydrophilic copolymer EVAL as the fiber substrate.The microstructures of th...EVAL hollow fiber membrane adsorbents filled with powder D061-type cation exchange resin were prepared through dry-wet spinning process,using hydrophilic copolymer EVAL as the fiber substrate.The microstructures of the membrane adsorbents were observed,and the pure water fluxes,BSA rejection,and static adsorption capacities of membrane adsorbents for BSA were measured.The effect of the resin-filled content on membrane performance has been discussed.The results showed that EVAL hollow fiber membrane adsorbents filled with D061-type cation exchange resins had good adsorption capacity,and the adsorption capacity increased with the quantity of the resin-filled content.The static protein adsorption capacity was 77.14 mg BSA/g membrane adsorbents when D061 resin loading content was 65%at pH 4.5.展开更多
Objective To explore the optimum condition for complex enzyme-assisted extraction of galanthamine from Lycoris aurea by L_9(3~4) orthogonal array design and separation effect of cation exchange resin on galanthamine...Objective To explore the optimum condition for complex enzyme-assisted extraction of galanthamine from Lycoris aurea by L_9(3~4) orthogonal array design and separation effect of cation exchange resin on galanthamine. Methods Cellulase and pectinase solution was used as the extraction solvent. The effects of p H value of enzyme, amount of complex enzyme, dissociation time, and enzymatic hydrolysis temperature on the extraction results were investigated. Results The optimal conditions were obtained as follows: ratio of solid to liquid(g:mL) 1:10, pH value 4.5, amount of complex enzymes 4%, enzymatic hydrolysis temperature 50oC, and reaction time 2.0 h. Under these conditions, the extraction yield of galanthamine was 0.0294%. In addition, D-001 cation exchange resin was selected for separation of galanthamine. The separation conditions were that adsorption flow rate was 3 BV/h with reagent of pH2 and the desorption flow rate was 3 BV/h with 70% ethanol solution containing 1.5 mol/L ammonia. After separation, the content of galanthamine was increased to 12.31%. Conclusion The results provide a reference for industrial production of galanthamine.展开更多
Self-made cation exchange resin supported nanoscale zero-valent iron (R-nZVI) was used to remove phosphorus in rainwater runoff. 80% of phosphorus in rainwater runoff from grassland was removed with an initial conce...Self-made cation exchange resin supported nanoscale zero-valent iron (R-nZVI) was used to remove phosphorus in rainwater runoff. 80% of phosphorus in rainwater runoff from grassland was removed with an initial concentration of 0.72 mg. L-1 phosphorus when the dosage of R-nZVl is 8 g per liter rainwater, while only 26% of phosphorus was removed when using cation exchange resin without supported nanoscale zero-valent iron under the same condition. The adsorption capacity of R-nZVI increased up to 185 times of that of the cation exchange resin at a saturated equilibrium phosphorous concentration of 0.42 mg. L-1. Various techniques were implemented to characterize the R-nZVI and explore the mechanism of its removal of phosphate. Scanning electron microscopy (SEM) indicated that new crystal had been formed on the surface of R-nZVI. The result from inductive coupled plasma (ICP) indicated that 2.1% of nZVI was loaded on the support material. The specific surface area was increased after the load of nanoscale zero-valent iron (nZVI), according to the measurement of BET-N2 method. The result of specific surface area analysis also proved that phosphorus was removed mainly through chemical adsorption process. X-ray photoelectron spectroscopy (XPS) analysis showed that the new product obtained from chemical reaction between phosphate and iron was ferrous phosphate.展开更多
Pyrolysis is a cost-effective and safe method for the disposal of radioactive spent resins.In this work,the catalytic effects of V_(2)O_(5) on the pyrolysis of cation exchange resin are investigated for the first time...Pyrolysis is a cost-effective and safe method for the disposal of radioactive spent resins.In this work,the catalytic effects of V_(2)O_(5) on the pyrolysis of cation exchange resin are investigated for the first time.The results show that it is a better catalyst than others so far studied and achieves a lowering of final pyrolysis temperature and residual rate simultaneously when aided by physical blending.The maximum reductions of the final pyrolysis temperature and the residual rate are 173℃and 11.9%(in weight),respectively.Under the action of V_(2)O_(5),low-temperature(445℃)removal of partial sulfonic acid groups occurs and the pyrolysis of the resin copolymer matrix is promoted.This is demonstrated by the analysis of pyrolysis residues at different temperatures by X-ray photoelectron spectroscopy(XPS)and element analysis.The catalytic activity of V_(2)O_(5) is determined by effects both at acid sites and oxidation-reduction centers via H2-TPR(temperature programmed reduction),V_(2)-TPD(temperature programmed desorption),CV_(2)-TPD,and NH3-TPD.The catalytic effect of oxidation-reduction centers in V_(2)O_(5) is achieved by close contact with the sulfur bond through chemisorption under the effect of acid sites.V_(2)O_(5) is also believed to be the reason for the removal of partial sulfonic acid groups at lower temperatures(445℃).V_(2)O_(5) is an effective catalyst for spent resin pyrolysis and can be further applied in industry.展开更多
N-nitrosodimethylamine(NDMA) precursors consist of a positively charged dimethylamine group and a non-polar moiety, which inspired us to develop a targeted cation exchange technology to remove NDMA precursors. In th...N-nitrosodimethylamine(NDMA) precursors consist of a positively charged dimethylamine group and a non-polar moiety, which inspired us to develop a targeted cation exchange technology to remove NDMA precursors. In this study, we tested the removal of two representative NDMA precursors, dimethylamine(DMA) and ranitidine(RNTD), by strong acidic cation exchange resin. The results showed that pH greatly affected the exchange efficiency, with high removal(DMA 〉 78% and RNTD 〉 94%) observed at pH 〈 pk_a-1 when the molar ratio of exchange capacity to precursor was 4. The exchange order was obtained as follows: Ca^(2+)〉 Mg^(2+)〉 RNTD~+〉 K~+〉 DMA~+〉 NH_4~+〉 Na~+. The partition coefficient of DMA~+to Na~+was 1.41 ± 0.26, while that of RNTD~+to Na~+was 12.1 ± 1.9. The pseudo second-order equation fitted the cation exchange kinetics well. Bivalent inorganic cations such as Ca^(2+)were found to have a notable effect on NA precursor removal in softening column test. Besides DMA and RNTD, cation exchange process also worked well for removing other 7 model NDMA precursors. Overall, NDMA precursor removal can be an added benefit of making use of cation exchange water softening processes.展开更多
基金supported by the National Natural Science Foundation of China (No.22176067).
文摘The treatment and disposal of radioactive waste are presently facing great challenges.Spent ion exchange resins have become a focus of attention due to their high production and serious environmental risks.In this paper,a simplified model of cationic exchange resin is proposed,and the degradation processes of cationic resin monomer initiated by hydroxyl radicals(·OH)are clarified by combining statistical molecular fragmentation(SMF)model and density functional theory(DFT)calculations.The prediction of active sites indicates that the S-O bonds and the C-S bond of the sulfonic group are more likely to react during the degradation.The meta-position of the sulfonic group on the benzene ring is the most active site,and the benzene ring without the sulfonic group has a certain reactivity.The C11-C14 and C17-C20 bonds,on the carbon skeleton,are the most easily broken.It is also found that dihydroxy addition and elimination reactions play a major role in the process of desulfonation,carbon skeleton cleavage and benzene ring separation.The decomposition mechanisms found through the combination of physical models and chemical calculations,provide theoretical guidance for the treatment of complex polycyclic aromatic hydrocarbons.
基金Vietnam National University-Ho Chi Minh City under grant number A2020-16-01.
文摘In this study,we reported on the concept and practical use of cation exchange resin(CER)for removing anions in water via pretreating the CER with metal salts.The cation exchange resinsupported iron and magnesium oxides/hydroxides composite(FeMg/CER)was synthesized and introduced as a new and potential adsorbent for selective removal of nitrate ion in the water environment.Characteristics of FeMg/CER were determined by techniques such as Fouriertransform infrared spectroscopy,scanning electron microscopy,and Xray diffraction.The results showed that FeMg/CER material had a high nitrate adsorption capacity of 200 mg NO_(3)^()·g^(1)with a fast equilibrium adsorption time of 30 min at pH 5.In addition,it had good durability of at least 10 times of regeneration,which could be applied to practical water and wastewater treatment.
基金support from the Natural Science Foundation of Shandong Province (Grant no.ZR2013BL010)the Research Excellence Award of Shandong University of Technology and the Zibo Technology Research and Development Program of China (Grant no.2013GG04110)
文摘This study describes the kinetics and thermodynamics of the esterification of acidified oil with methanol catalyzed by sulfonated cation exchange resins(SCER). The effects of the mass ratio of methanol to acidified oil,reaction temperature,and catalyst loading were studied to optimize the conditions for maximum conversion of free fatty acids(FFAs). The results showed that the optimal conversion rate of FFAs was 91.87% at the mass ratio of methanol to acidified oil of 2.5:1.0,reaction temperature of 65.0 °C,catalyst loading of 5.0 g and reaction time of 8.0 h. The external and internal mass transfer resistances were negligible based on the experimental results and a pseudo-homogeneous kinetic model was proposed for the esterification. The activation energy and thermodynamic parameters including G,S and H were determined. The conversion rates of FFAs obtained from the established model were in good agreement with the experimental data.
文摘The polystyrene cation exchange resin was exchanged by La 3+ and then were carbonized to make resin carbon material. The electrochemical properties of the resin carbon material as the electrode of the lithium ion cell were investigated. The test results show that comparing with the polystyrene cation exchange resin without adulterating, the contents of hydrogen, oxygen and sulfur are changed obviously for the resin carbon material derived from the La 3+ adulterating polystyrene cation exchange resin. The contents of hydrogen and oxygen are increased, and the one of sulfur is decreased. The test results also indicate that it is more easily to form the stratum graphite minicrystal structure with bigger diameter for the La 3+ adulterating resin. According to the electrochemical test results, the electrode derived from La 3+ adulterating polystyrene cation exchange resin has much better electrochemical property, and the capacity of charge and discharge of the electrode is increased about 30 mAh·g -1 in average.
文摘Strongly acidic cation exchange resin(1x1,H form)has been successfully used as a catalyst in synthesis of diphenyl N-benzyloxycarbonyl-1-aminobenzylphosphonate, N-benzyloxycarbonyl-1-aminobenzylphenylphosphinic acid and N-p-tolylsulfonyl-1-aminobenzyl phenylphosphinic acid in high yields.
文摘In this work, melamine-formaldehyde resin was cationized by adding modifiers so that the fibers closely bonded to improve their usability and the wet strength of paper was greatly improved. Triethanolamine and dimethylamine were added to modify the melamine-formaldehyde resin,respectively.The mechanism of the cationized resin was explored and the possible chemical reactions were deduced. It was concluded that,with the use of triethanolamine,the most optimum product was obtained by hydroxymethylation for 30 min with a temperature of 85℃ and p H of 9. 0 where n( melamine) ∶ n( formaldehyde) ∶ n( methanol) ∶ n( triethanolamine) was 100 ∶ 330 ∶ 450 ∶ 15. With the combined use of dimethylamine and methanol,the optimal product was acquired by condensation for 30 min at a temperature of 50℃ and p H of 2. 0 at melamine, formaldehyde, methanol, and dimethylamine molar ratio of100∶ 330∶ 350∶ 20. With the only use of dimethylamine,the optimal product was obtained by condensation at melamine,formaldehyde,dimethylamine molar ratio of 100∶ 330∶ 10. The wet tensile strength of fruit-bagging paper was improved by adding cationized melamine-formaldehyde resin. The zeta potential,charge density,and conductivity of the melamine-formaldehyde resin were also studied.
基金The University Grants Commission,New Delhi for its funding of this workIndian Institute of Science,Bangalore for its instrumental support+2 种基金Department of Physics,Sri Venkateswara University,Tirupathi,for its assistance in the SEM studyUGC,New Delhi for its support under SAPDST,New Delhi for its support under FIST
文摘2-Acryloxyacetophenone (AAP) was prepared and subjected to suspension polymerization with methyl methacrylate (MMA) using azobisisobutyronitrile (AIBN) as free radical initiator. The differently sulfonated AAP-MMA cross-linked copolymer cationic exchange resins were prepared by sulfonation with concentrated sulphuric acid at 70 ~C. Several characteristics of the prepared resins were evaluated, i.e. FTIR, the ion-exchange capacity (IEC), thermo gravimetric analysis (TGA), particle size distribution and microscopic morphology. The resin characteristics were altered with degree of sulfonation, providing that differently sulfonated resins could be prepared. The behavior of atenolol (ATL) loading and in vitro release in the USP stimulated gastric and intestinal fluids of the obtained resins were evaluated. The drug loaded in the resin increased with increasing degree of sulfonation and hence the drug binding site in resin employed. The drug release was lower from the resins with higher content of sulfonic group due to the increase in the diffusive path depth. The drug release was a little lower in stimulated gastric fluid (SGF) than in stimulated intestinal fluids (SIF). The basic groups, ionized to a little greater extent in SGF and preferred binding with the resin rather than releasing. Hence, the differently sulfonated resins could be utilized as novel carriers for drug delivery.
基金sponsored by the project of Key Nature Science Foundation of Tianjin(No.043803911)the National Natural Science Foundation of China(Grant No.50473025)Open project of State Key Lab of Heavy Oil(University of petroleum(East China)No.2008-10).
文摘EVAL hollow fiber membrane adsorbents filled with powder D061-type cation exchange resin were prepared through dry-wet spinning process,using hydrophilic copolymer EVAL as the fiber substrate.The microstructures of the membrane adsorbents were observed,and the pure water fluxes,BSA rejection,and static adsorption capacities of membrane adsorbents for BSA were measured.The effect of the resin-filled content on membrane performance has been discussed.The results showed that EVAL hollow fiber membrane adsorbents filled with D061-type cation exchange resins had good adsorption capacity,and the adsorption capacity increased with the quantity of the resin-filled content.The static protein adsorption capacity was 77.14 mg BSA/g membrane adsorbents when D061 resin loading content was 65%at pH 4.5.
基金Hunan Provincial Science and Technology Department(2012TP4002-3)Zhangjiajie Science and Technology Bureau(2014YB17)
文摘Objective To explore the optimum condition for complex enzyme-assisted extraction of galanthamine from Lycoris aurea by L_9(3~4) orthogonal array design and separation effect of cation exchange resin on galanthamine. Methods Cellulase and pectinase solution was used as the extraction solvent. The effects of p H value of enzyme, amount of complex enzyme, dissociation time, and enzymatic hydrolysis temperature on the extraction results were investigated. Results The optimal conditions were obtained as follows: ratio of solid to liquid(g:mL) 1:10, pH value 4.5, amount of complex enzymes 4%, enzymatic hydrolysis temperature 50oC, and reaction time 2.0 h. Under these conditions, the extraction yield of galanthamine was 0.0294%. In addition, D-001 cation exchange resin was selected for separation of galanthamine. The separation conditions were that adsorption flow rate was 3 BV/h with reagent of pH2 and the desorption flow rate was 3 BV/h with 70% ethanol solution containing 1.5 mol/L ammonia. After separation, the content of galanthamine was increased to 12.31%. Conclusion The results provide a reference for industrial production of galanthamine.
文摘Self-made cation exchange resin supported nanoscale zero-valent iron (R-nZVI) was used to remove phosphorus in rainwater runoff. 80% of phosphorus in rainwater runoff from grassland was removed with an initial concentration of 0.72 mg. L-1 phosphorus when the dosage of R-nZVl is 8 g per liter rainwater, while only 26% of phosphorus was removed when using cation exchange resin without supported nanoscale zero-valent iron under the same condition. The adsorption capacity of R-nZVI increased up to 185 times of that of the cation exchange resin at a saturated equilibrium phosphorous concentration of 0.42 mg. L-1. Various techniques were implemented to characterize the R-nZVI and explore the mechanism of its removal of phosphate. Scanning electron microscopy (SEM) indicated that new crystal had been formed on the surface of R-nZVI. The result from inductive coupled plasma (ICP) indicated that 2.1% of nZVI was loaded on the support material. The specific surface area was increased after the load of nanoscale zero-valent iron (nZVI), according to the measurement of BET-N2 method. The result of specific surface area analysis also proved that phosphorus was removed mainly through chemical adsorption process. X-ray photoelectron spectroscopy (XPS) analysis showed that the new product obtained from chemical reaction between phosphate and iron was ferrous phosphate.
基金Project supported by the National Natural Science Foundation of China(No.U1862203)the National Science Fund for Distinguished Young Scholars(No.21525627)the Science Fund for Creative Research Groups of National Natural Science Foundation of China(No.61621002)。
文摘Pyrolysis is a cost-effective and safe method for the disposal of radioactive spent resins.In this work,the catalytic effects of V_(2)O_(5) on the pyrolysis of cation exchange resin are investigated for the first time.The results show that it is a better catalyst than others so far studied and achieves a lowering of final pyrolysis temperature and residual rate simultaneously when aided by physical blending.The maximum reductions of the final pyrolysis temperature and the residual rate are 173℃and 11.9%(in weight),respectively.Under the action of V_(2)O_(5),low-temperature(445℃)removal of partial sulfonic acid groups occurs and the pyrolysis of the resin copolymer matrix is promoted.This is demonstrated by the analysis of pyrolysis residues at different temperatures by X-ray photoelectron spectroscopy(XPS)and element analysis.The catalytic activity of V_(2)O_(5) is determined by effects both at acid sites and oxidation-reduction centers via H2-TPR(temperature programmed reduction),V_(2)-TPD(temperature programmed desorption),CV_(2)-TPD,and NH3-TPD.The catalytic effect of oxidation-reduction centers in V_(2)O_(5) is achieved by close contact with the sulfur bond through chemisorption under the effect of acid sites.V_(2)O_(5) is also believed to be the reason for the removal of partial sulfonic acid groups at lower temperatures(445℃).V_(2)O_(5) is an effective catalyst for spent resin pyrolysis and can be further applied in industry.
基金supported by the National Natural Science Foundation of China (No.21477059)the National Water Major Project (No.2015ZX07402-002)+2 种基金the Fundamental Research Funds for the Central Universities (No.15CX02016A)the Tsinghua University Initiative Scientific Research Program (No.20131089247)the open project of State Key Joint Laboratory of environmental simulation and pollution control (Tsinghua University)
文摘N-nitrosodimethylamine(NDMA) precursors consist of a positively charged dimethylamine group and a non-polar moiety, which inspired us to develop a targeted cation exchange technology to remove NDMA precursors. In this study, we tested the removal of two representative NDMA precursors, dimethylamine(DMA) and ranitidine(RNTD), by strong acidic cation exchange resin. The results showed that pH greatly affected the exchange efficiency, with high removal(DMA 〉 78% and RNTD 〉 94%) observed at pH 〈 pk_a-1 when the molar ratio of exchange capacity to precursor was 4. The exchange order was obtained as follows: Ca^(2+)〉 Mg^(2+)〉 RNTD~+〉 K~+〉 DMA~+〉 NH_4~+〉 Na~+. The partition coefficient of DMA~+to Na~+was 1.41 ± 0.26, while that of RNTD~+to Na~+was 12.1 ± 1.9. The pseudo second-order equation fitted the cation exchange kinetics well. Bivalent inorganic cations such as Ca^(2+)were found to have a notable effect on NA precursor removal in softening column test. Besides DMA and RNTD, cation exchange process also worked well for removing other 7 model NDMA precursors. Overall, NDMA precursor removal can be an added benefit of making use of cation exchange water softening processes.