Works on exploring an environmentally clean method for producing an Mg,Al-hydrotalcite(Mg6Al2(OH) 16CO3·4H2O) layer and/or calcium carbonate(CaCO3) layer on Mg alloy in a carbonic acid solution system(aqueous HCO...Works on exploring an environmentally clean method for producing an Mg,Al-hydrotalcite(Mg6Al2(OH) 16CO3·4H2O) layer and/or calcium carbonate(CaCO3) layer on Mg alloy in a carbonic acid solution system(aqueous HCO3-/CO3 2-or Ca 2+ /HCO3-) at 50℃ were reviewed.Conversion treatment for the Mg,Al-hydrotalcite conversion coating was as follows.Mg alloy was treated first in acidic HCO3-/CO3 2-aqueous for precursor layer formation on Mg alloy surface and then in alkaline HCO3-/CO3 2-aqueous to form a crystallized Mg,Al-hydrotalcite coating.Duration of an Mg,Al-hydrotalcite coating on Mg alloy surface was reduced from 12 h to 4 h by the conversion treatment.On the other hand,for reducing the formation time of CaCO3 coating on Mg alloy,the aqueous Ca 2+ /HCO3-with a saturated Ca 2+ content was employed for developing a CaCO3 coating on Mg alloy.A dense CaCO3 coating could yield on Mg alloy surface in 2 h.Corrosion rate(corrosion current density,Jcorr) of the Mg,Al-hydrotalcite-coated sample and CaCO3-coated AZ91D sample was 7-10μA/cm 2,roughly two orders less than the Jcorr of the as-diecast sample(about 200μA/cm 2) . No corrosion spot on the Mg,Al-hydrotalcite-coated sample and CaCO3-coated sample was observed after 72 h and 192 h salt spray test,respectively.展开更多
The reaction between carbonic acid and montmorillonite minerals was studied in order to provide a theoretical basis for analyzing changes in the physical properties of coal seams after CO_(2)injection and for optimizi...The reaction between carbonic acid and montmorillonite minerals was studied in order to provide a theoretical basis for analyzing changes in the physical properties of coal seams after CO_(2)injection and for optimizing CO_(2) pumping parameters.A single montmorillonite mineral of purity[90%was selected and subjected to reactions at 25,35,and 45℃in carbonic acid solutions of varying acidity.The Si and Al concentrations in the solutions and the structure and elemental compositions of the montmorillonite before and after the reactions were analyzed using a spectrophotometer,an X-ray diffractometer,and an energy-dispersive X-ray spectrometer;kinetic reaction models were established for the dissolution of Si and Al in carbonic acid solutions in order to estimate the apparent activation energy of Si dissolution under different acidity conditions.The results indicate that Al dissolved rapidly and soon reached solubility equilibrium.On the other hand,Si concentration in the solutions increased rapidly and then gradually declined with vibrations,with maximum values at 25,35,and 45℃,which were observed at approximately 96,72,and 48 h,respectively.In addition,Si dissolution fitted the diffusion-controlled reaction model well;as the pH value decreased,the apparent activation energy of Si dissolution decreased,and Si became easier to dissolve.Furthermore,it was concluded that as a weak acid,carbonic acid causes little damage to the mineral structure of montmorillonite.展开更多
A carbon solid acid catalyst was prepared by the sulfonation of partially carbonized peanut shell with concentrated H2SO4. The structure and acidity of the catalyst were characterized by Fourier transform infrared spe...A carbon solid acid catalyst was prepared by the sulfonation of partially carbonized peanut shell with concentrated H2SO4. The structure and acidity of the catalyst were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X‐ray diffraction, thermogravimetric analysis, X‐ray photoelectron spectroscopy, and elemental analysis, which showed that it was an amorphous carbon material composed of aromatic carbon sheets in random orientations. Sulfonic acid groups were present on the surface at a density of 0.81 mmol/g. The carbon solid acid catalyst showed better performance than HZSM‐5 for the esterification of cyclohexene with formic acid. At a3：1 molar ratio of formic acid to cyclohexene, catalyst loading of 0.07 g/mL of cyclohexene, and reaction time of 1 h at 413 K, the cyclohexene conversion was 88.4% with 97.3% selectivity to cyclohexyl formate. The carbon solid acid catalyst showed better reusability than HZSM‐5 because its large pores were minimally affected by the accumulation of oligomerized cyclohexene, which deactivated HZSM‐5. The activity of the carbon solid acid catalyst decreased somewhat in the first two recycles due to the leaching of polycyclic aromatic hydrocarbon containing –SO3H groups and then it remained constant in the following reuse.展开更多
Two kinds of mesoporous carbon solid acids(LDMCE-SO3H and LDMCS-SO3H)were successfully prepared using masson pine alkali lignin as carbon source by evaporation-induced self-assembly(EISA)and salt-induced selfassembly(...Two kinds of mesoporous carbon solid acids(LDMCE-SO3H and LDMCS-SO3H)were successfully prepared using masson pine alkali lignin as carbon source by evaporation-induced self-assembly(EISA)and salt-induced selfassembly(SISA)followed by sulfonation,respectively.In terms of preparation process,SISA(self-assembly in water and preparation time of 2 days)is greener and simpler than EISA(self-assembly in ethanol and preparation time of 7 days).The prepared LDMCE-SO3H and LDMCS-SO3H exhibit obvious differences in structural characteristics such as pore channel structure,specific surface area,mesopore volume and the density of-SO3H groups.Furthermore,the catalytic performances of LDMCE-SO3H and LDMCS-SO3H were investigated in the hydrolysis of microcrystalline cellulose in water,and the glucose yields of 48.99%and 54.42%were obtained under the corresponding optimal reaction conditions.More importantly,the glucose yields still reached 28.85%and 30.35%after five runs,and restored to 39.02%and 45.98%through catalysts regeneration,respectively,demonstrating that LDMCE-SO3H and LDMCS-SO3H have excellent recyclability and regenerability.展开更多
The synthesis of 2, 4-diisopropyl-5,5-dimethy1- 1.3-dioxane through the acetalization of isobutyraldehyde with 2, 2, 4-trimethy1-1,3-pentanediol （TMPD） catalyzed by the novel carbon based acid was first carried out....The synthesis of 2, 4-diisopropyl-5,5-dimethy1- 1.3-dioxane through the acetalization of isobutyraldehyde with 2, 2, 4-trimethy1-1,3-pentanediol （TMPD） catalyzed by the novel carbon based acid was first carried out. High conversion （≥98%） and specific selectivity were obtained using the novel carbon based acid, which kept high activity after it was reused 5 times. Moreover. the catalyst could be used to catalyze the acetalization and ketalization of different aldehydes and ketones with superior yield. The yield of several products was over 90%. The novel heterogeneous catalyst has the distinct advantages of high activity, strikingly simple workup procedure, non-pollution, and reusability, which will contribute to the success of the green process greatly.展开更多
This work mainly studies the effect of fluid phase momentum transfer mechanisms on the acidizing results,including the retardation effect of the porous structure and the interaction between the fluid phase,such as vis...This work mainly studies the effect of fluid phase momentum transfer mechanisms on the acidizing results,including the retardation effect of the porous structure and the interaction between the fluid phase,such as viscous dissipation and inertial effect.The results show that the acid fluid momentum transfer is influenced by the complex porous structure and fluid viscous dissipation.Eventually,the Stokes-Darcy equation is recommended to be adopted to describe the fluid phase momentum transfer in the following numerical simulation studies of the carbonate acidizing process.Based on this model,a parametric research is carried out to investigate the impact of acid on rock physical characteristics in the stimulation process.Increasing the acid concentration appears to minimize the quantity of acid consumed for the breakthrough.The acid surface reaction rate has a considerable impact on the pore volume to breakthrough and the optimum acid injection rate.The influence of permeability on the acidizing results basically shows a negative correlation with the injection rate.The difference between the acidizing curves of different permeability gradually becomes insignificant with the decrease in injection rate.The existence of isolated fracture and vug significantly reduces acid consumption for the breakthrough.展开更多
The dissolution of carbon steel in 5% HCl in the temperature range of 30~90℃ was inhibited by two organic compounds having the general formula: ClR NH2(CH2)n NH2 RCl where R is a benzyl group. The behaviour of these ...The dissolution of carbon steel in 5% HCl in the temperature range of 30~90℃ was inhibited by two organic compounds having the general formula: ClR NH2(CH2)n NH2 RCl where R is a benzyl group. The behaviour of these inhibitors in acidic medium were investigated using weight loss method, open circuit potential and linear polarization technique. These inhibitors provided satisfactory corrosion inhibition for carbon steel in hydrochloric acid solutions even at higher temperature and acid concentration (10%). The electrochemical results showed that the polarization resistance (Rp) values increased with increasing inhibitor concentration, also the corrosion current decreased and a higher inhibition efficiency was obtained. The protective properties of these two organic inhibitors were attributed to the chemisorption mechanism展开更多
A carbon paste electrode（CPE） chemically modified with multiwall carbon nanotubes and ferrocene（FC） was used as a selective electrochemical sensor for the simultaneous determination of trace amounts of cysteamine...A carbon paste electrode（CPE） chemically modified with multiwall carbon nanotubes and ferrocene（FC） was used as a selective electrochemical sensor for the simultaneous determination of trace amounts of cysteamine（CA） and folic acid（FA）.This modified electrode showed very efficient electrocatalytic activity for the anodic oxidation of CA.The peak current of differential pulse voltammograms of CA and FA increased linearly with their concentration in the ranges of 0.7-200μmol/L CA and 5.0- 700μmol/L FA.The detection limits for CA and FA were 0.3μmol/L and 2.0μmoI/L,respectively.The diffusion coefficient（D） and transfer coefficient（α） of CA were also determined.These conditions are sufficient to allow determination of CA and FA both individually and simultaneously.展开更多
Humic acid(HA)was carbonized at 300,400 and 500℃ and then functionalized with 1 wt%–12 wt%Fe(Ⅲ)respectively[CHA300/400/500-Fe(Ⅲ)].Adsorption of such Fe(III)-functionalized carbonized HA as adsorbents to aqueous te...Humic acid(HA)was carbonized at 300,400 and 500℃ and then functionalized with 1 wt%–12 wt%Fe(Ⅲ)respectively[CHA300/400/500-Fe(Ⅲ)].Adsorption of such Fe(III)-functionalized carbonized HA as adsorbents to aqueous tetracycline(TC:25 mg·L^-1)was studied.The adsorption equilibrium time for CHA400-Fe(Ⅲ)to TC was 6 h faster and the adsorption removal efficiency(Re)was two times higher than that of HA/CHA.The adsorption Reof CHA400-Fe(Ⅲ)loaded 10%iron[CHA400-(10%)Fe(Ⅲ)]to TC could reach 99.8%at 8 h and still kept80.6%after 8 cycles.The adsorption kinetics were well fitted to the pseudo-second-order equation and the adsorption isotherms could be well delineated via Langmuir equations(R^2N 0.99),indicating that the homogeneous chemical adsorption of TC occurred on the adsorbents.The main adsorption mechanisms of TC were complexation Fe(III)and hydrophobic distribution.Electropositive and electronegative repulsion between TC and CHA400-(10%)Fe(Ⅲ)at lowly p H(2)and highly p H(8–10)respectively,leaded to the relatively low adsorption capacity and more notable influence of ion concentration.When the p H was between 4 and 8,TC mainly existed in neutral molecules(TCH2),so the influence of ion concentration was not obvious.The dynamic adsorption results showed that the CHA400-(10%)Fe(Ⅲ)could continuously treat about 2.4 L TC(27 mg·L^-1)wastewater with the effluent concentration as low as 0.068 mg·L^-1.Our study suggested a broad application prospect of a new,effective,lowcost and environment-friendly adsorbent CHA400-(10%)Fe(Ⅲ)for treatment of low-concentration TC polluted wastewater.展开更多
A batch experiment was conducted to investigate the adsorption of an acid dye(Acid Orange 51) and a basic dye(Safranine) from aqueous solutions by the sludge-based activated carbon(SBAC). The results show that the ads...A batch experiment was conducted to investigate the adsorption of an acid dye(Acid Orange 51) and a basic dye(Safranine) from aqueous solutions by the sludge-based activated carbon(SBAC). The results show that the adsorption of Acid Orange 51 decreases at high p H values, whereas the uptake of Safranine is higher in neutral and alkaline solutions than that in acidic conditions. The adsorption time needed for Safranine to reach equilibrium is shorter than that for Acid Orange 51. The uptakes of the dyes both increase with temperature increasing, indicating that the adsorption process of the dyes onto SBAC is endothermic. The equilibrium data of the dyes are both best represented by the Redlich-Peterson model. At 25 °C, the maximum adsorption capacities of SBAC for Acid Orange 51 and Safranine are 248.70 mg/g and 525.84 mg/g, respectively. The Elovich model is found to best describe the adsorption process of both dyes, indicating that the rate-limiting step involves the chemisorption. It can be concluded that SBAC is a promising material for the removal of Acid Orange 51 and Safranine from aqueous solutions.展开更多
In the present work, the behavior of folic acid （FA） molecule adsorbed onto single-walled carbon nanotube （SWCNT） was examined using the DFT-B3LYP/6-31G＊ level. In order to obtain information about the binding fe...In the present work, the behavior of folic acid （FA） molecule adsorbed onto single-walled carbon nanotube （SWCNT） was examined using the DFT-B3LYP/6-31G＊ level. In order to obtain information about the binding features of SWCNT as adsorbent with FA molecule, several studies, including the structural and electronic parameters and also the Atoms in Molecules （AIM） analysis, were performed. It was observed that the FA molecule via hydrogen bond prefers to adsorb on SWCNT with adsorption energy of about -18.70 kcal/mol. The molecular orbitals （HOMO and LUMO）, natural bond orbital （NBO）,analysis, and density of states （DOS） plot indicated that a charge about 0.032 [ e [ is transferred from the FA molecule to the nanotube. After solvation energy calculations, it was found that the presence of a polar solvent causes an increase in FA adsorption on the single-walled carbon nanotube. Topological features such as electron energy density （Hc） and Laplacian of the electron density （V2p~） demonstrate partial covalent nature for H（ll6）...O（10） interaction in the FA/SWCNT complex. According to the calculated results, the single-walled carbon nanotubes are expected to be a potential efficient adsorbent for the adsorption of folic acid drug and also can be used as a suitable drug delivery vehicle within biological systems.展开更多
Nowadays, modified electrodes with metal nanoparticles have appeared as an alternative for the electroanalysis of various compounds. In this study, gold nanoparticles（GNPs） were chosen as interesting metal nanoparti...Nowadays, modified electrodes with metal nanoparticles have appeared as an alternative for the electroanalysis of various compounds. In this study, gold nanoparticles（GNPs） were chosen as interesting metal nanoparticles for modifying carbon paste electrode（CPE）. GNPs and the gold nanoparticles-modified carbon paste electrode（GNPs/CPE） were characterized by UV–Vis spectroscopy, transmission electron microscopy（TEM） and scanning electron microscopy（SEM）. GNPs/CPE as a simple and sensitive electrode was used to study three important biological molecules： folic acid（FA）, uric acid（UA） and ascorbic acid（AA）. Square wave voltammetry（SWV） was used as an accurate technique for quantitative measurements. A good linear relation was observed between anodic peak current（ipa） and FA（5.2 × 10（-6）– 2.5 × 10（-5）M）, UA（1.2 × 10（-6）– 2.1 × 10（-5）M） and AA（1.2 × 10（-6）– 2.5 × 10（-5）M） concentrations in simultaneous determination of these molecules.展开更多
The adsorption behavior of folic acid onto（5,0） zigzag and（5,5） armchair carbon nanotube（SWCNT） has been investigated using B3 LYP density functional at the 6-31G＊ level. The adsorption energies,molecular orbit...The adsorption behavior of folic acid onto（5,0） zigzag and（5,5） armchair carbon nanotube（SWCNT） has been investigated using B3 LYP density functional at the 6-31G＊ level. The adsorption energies,molecular orbital analysis and structural changes at the adsorption site are indicative of covalent adsorption on the zigzag SWCNT surface,while the adsorption is physical on the armchair SWCNT surface. The density of states（DOS） Plot and the quantum molecular descriptors（QMD） are witness to the significant changes in the electronic properties of SWCNT systems after the attachment of adsorbed species to the tube surface. According to the calculated results,the single-walled carbon nanotubes are expected to be a potential efficient adsorbent for the adsorption of folic acid drug and also can be used as a suitable drug delivery vehicle within biological systems.展开更多
In this study,Au nanoparticles/poly 5-[（2-hydroxynaphthalen-l-yl）diazenyl]isophthalic acid film modified glassy carbon electrode（AuNPs/poly（NDI）/GCE） has shown excellent electrocatalytic activity toward the oxid...In this study,Au nanoparticles/poly 5-[（2-hydroxynaphthalen-l-yl）diazenyl]isophthalic acid film modified glassy carbon electrode（AuNPs/poly（NDI）/GCE） has shown excellent electrocatalytic activity toward the oxidation of adrenaline（ADR）,paracetamol（PAC）,and tryptophan（Trp）.The bare glassy carbon electrode（GCE） fails to separate the oxidation peak potentials of these molecules,while the poly（NDI） film modified electrode can resolve them.Electrochemical impedance spectroscopy（EIS）indicates that the charge transfer resistance of the bare electrode decreases as 5-[（2-hydroxynaphthalen-l-yl）diazenyl]isophthalic acid is electropolymerized on the bare electrode.Furthermore,EIS exhibits enhancement of electron transfer kinetics between analytes and the electrode after electrodeposition of Au nanoparticles.Differential pulse voltammetry results show that the electrocatalytic current increases linearly in the ranges of 0.01-680.0 μmol L^-1 for ADR,0.05-498.0 μmol L^-1 for PAC,and 3.0-632.0 μmol L^-1 for Trp;with detection limits（S/N = 3） of 0.009 μmol L^-1,0.005 μmol L^-1,and 0.09 μmol L^-1 for ADR,PAC,and Trp,respectively.The proposed method has been successfully applied for simultaneous determination of ADR,PAC,and Trp in biological samples.展开更多
In this work, a new sample pretreatment method prior to HPLC separations was developed for the determination of auxins in plant samples, Owing to its large surface area and high adsorption capacity, multi-walled carbo...In this work, a new sample pretreatment method prior to HPLC separations was developed for the determination of auxins in plant samples, Owing to its large surface area and high adsorption capacity, multi-walled carbon nanotube （MWCNT） was chosen as the adsorbent for the extraction of auxins from plant samples. In this study, two important auxins were selected as model analytes, namely indole-3- butyric acid （IBA） and 1-naphthylacetic acid （NAA）. They could be extracted and concentrated due to their π-π stacking interactions with MWCNT. Then HPLC-UV was introduced to detect IBA and NAA after sample pretreatment. Factors that may affect the enrichment efficiency were investigated and optimized. Comparative studies showed that MWCNT was superior to CI 8 for the extraction of the two analytes. Validation experiments showed that the optimized method had good linearity （0.9998 and 0.9960）, high recovery （81.4%-85.4%）, and low detection limits （0.0030 mg/L and 0.0012 mg/L）. The results indicated that the novel method had advantages of convenience, good sensitivity, high efficiency, and it was feasible for the determination of auxins in plant samples.展开更多
Polymers play an important role in hybrid enhanced oil recovery (EOR), which involves both a polymer and low-salinity water. Because the polymer commonly used for low-salinity polymer flooding (LSPF) is strongly sensi...Polymers play an important role in hybrid enhanced oil recovery (EOR), which involves both a polymer and low-salinity water. Because the polymer commonly used for low-salinity polymer flooding (LSPF) is strongly sensitive to brine pH, its efficiency can deteriorate in carbonate reservoirs containing highly acidic formation water. In this study, polymer efficiency in an acidic carbonate reservoir was investigated experimentally for different salinity levels and SO42− concentrations. Results indicated that lowering salinity improved polymer stability, resulting in less polymer adsorption, greater wettability alteration, and ultimately, higher oil recovery. However, low salinity may not be desirable for LSPF if the injected fluid does not contain a sufficient number of sulfate (SO42−) ions. Analysis of polymer efficiency showed that more oil can be produced with the same polymer concentration by adjusting the SO42− content. Therefore, when river water, which is relatively easily available in onshore fields, is designed to be injected into an acidic carbonate reservoir, the LSPF method proposed in this study can be a reliable and environmentally friendly method with addition of a sufficient number of SO42− ions to river water.展开更多
Replacing platinum for catalyzing hydrogen evolution reaction （HER） in acidic medium remains great chal- lenges. Herein, we prepared few-layered MoS2 by ball milling as an efficient catalyst for HER in acidic medium...Replacing platinum for catalyzing hydrogen evolution reaction （HER） in acidic medium remains great chal- lenges. Herein, we prepared few-layered MoS2 by ball milling as an efficient catalyst for HER in acidic medium, The activity of as-prepared MoS2 had a strong dependence on the ball milling time, Furthermore, Ketjen Black EC 300J was added into the ball-milled MoS2 followed by a second ball milling, and the resultant MoS2/carbon black hybrid material showed a much higher HER activity than MoS2 and carbon black alone. The enhanced activity of the MoS2/carbon black hybrid material was attributed to the increased abundance of catalytic edge sites of MoS） and excellent electrical coupling to the underlving carbon network.展开更多
A sensitive and selective method for the determination of ascorbic acid（AA） using [Cu（phen）2]2＋/multiwalled carbon nanotubes modified glassy carbon electrode was developed. Electrochemical behavior and surface ch...A sensitive and selective method for the determination of ascorbic acid（AA） using [Cu（phen）2]2＋/multiwalled carbon nanotubes modified glassy carbon electrode was developed. Electrochemical behavior and surface characteristics of the modified electrode were studied using scanning electrode microscopy（SEM）, electrochemical impedance spectroscopy（EIS） and cyclic voltammetry（CV）. The experimental results showed that the modified electrode enhanced the electrochemical response of AA and exhibited good analytical performance for AA determination from 10 to 1 042 ？mol/L with a low detection limit of 9.67μmol/L（S/N=3）. The modified electrode was also applied to the determination of AA in the Vitamin tablets and showed good recovery.展开更多
The aggregation of multi-walled carbon nanotubes （MWCNTs） in the aqueous phase not only inhibits their extensive utilization in various aspects but also dominates their environmental fate and transport.The role of s...The aggregation of multi-walled carbon nanotubes （MWCNTs） in the aqueous phase not only inhibits their extensive utilization in various aspects but also dominates their environmental fate and transport.The role of surfactants at low concentration in the aggregation of MWCNTs has been studied,however the effect of perfluorinated surfactants at low concentration is uncertain.To understand this interfacial phenomenon,the influences of perfluorooctanoic acid （PFOA）,and sodium dodecyl sulfate （SDS） as a control,on MWCNT aggregation in the aqueous phase were examined by the UV absorbency method.Influences of pH and cationic species on the critical coagulation concentration （CCC） value were evaluated.The CCC values were dependent on the concentration of PFOA,however a pronounced effect of SDS concentration on the CCC values was not observed.The CCC values of the MWCNTs were 51.6 mmol/L in NaCl and 0.28 mmol/L in CaCl 2 solutions,which suggested pronounced differences in the effects of Na＋ and Ca2＋ ions on the aggregation of the MWCNTs.The presence of both PFOA and SDS significantly decreased the CCC values of the MWCNTs in NaCl solution.The aggregation of the MWCNTs took place under acidic conditions and was not notably altered under neutral and alkaline conditions due to the electrostatic repulsion of deprotonated functional groups on the surface of the MWCNTs.展开更多
A new ascorbic acid sensor constituted of carbon paste and Fe(Ⅲ)Y zeolite was studied.The characters of the sensor such as linear range. potential window、apparen Michaelis constant、response time、stability and accu...A new ascorbic acid sensor constituted of carbon paste and Fe(Ⅲ)Y zeolite was studied.The characters of the sensor such as linear range. potential window、apparen Michaelis constant、response time、stability and accuracy wee investigated. The experimental results indicate that the analytical performance of the sensor is satisfactory.展开更多
基金Project supported by the Ministry of Education Under the ATU Plan
文摘Works on exploring an environmentally clean method for producing an Mg,Al-hydrotalcite(Mg6Al2(OH) 16CO3·4H2O) layer and/or calcium carbonate(CaCO3) layer on Mg alloy in a carbonic acid solution system(aqueous HCO3-/CO3 2-or Ca 2+ /HCO3-) at 50℃ were reviewed.Conversion treatment for the Mg,Al-hydrotalcite conversion coating was as follows.Mg alloy was treated first in acidic HCO3-/CO3 2-aqueous for precursor layer formation on Mg alloy surface and then in alkaline HCO3-/CO3 2-aqueous to form a crystallized Mg,Al-hydrotalcite coating.Duration of an Mg,Al-hydrotalcite coating on Mg alloy surface was reduced from 12 h to 4 h by the conversion treatment.On the other hand,for reducing the formation time of CaCO3 coating on Mg alloy,the aqueous Ca 2+ /HCO3-with a saturated Ca 2+ content was employed for developing a CaCO3 coating on Mg alloy.A dense CaCO3 coating could yield on Mg alloy surface in 2 h.Corrosion rate(corrosion current density,Jcorr) of the Mg,Al-hydrotalcite-coated sample and CaCO3-coated AZ91D sample was 7-10μA/cm 2,roughly two orders less than the Jcorr of the as-diecast sample(about 200μA/cm 2) . No corrosion spot on the Mg,Al-hydrotalcite-coated sample and CaCO3-coated sample was observed after 72 h and 192 h salt spray test,respectively.
基金This research was supported by the National Science and Technology Special Foundation for Major Large Oil and Gas Fields and Coal Bed Methane Development(2011ZX05042-003)the Provincial Ministry of State Key Laboratory Breeding Base of Open Projects Henan Gas Geology and Gas Control Laboratory(WS2013B06).
文摘The reaction between carbonic acid and montmorillonite minerals was studied in order to provide a theoretical basis for analyzing changes in the physical properties of coal seams after CO_(2)injection and for optimizing CO_(2) pumping parameters.A single montmorillonite mineral of purity[90%was selected and subjected to reactions at 25,35,and 45℃in carbonic acid solutions of varying acidity.The Si and Al concentrations in the solutions and the structure and elemental compositions of the montmorillonite before and after the reactions were analyzed using a spectrophotometer,an X-ray diffractometer,and an energy-dispersive X-ray spectrometer;kinetic reaction models were established for the dissolution of Si and Al in carbonic acid solutions in order to estimate the apparent activation energy of Si dissolution under different acidity conditions.The results indicate that Al dissolved rapidly and soon reached solubility equilibrium.On the other hand,Si concentration in the solutions increased rapidly and then gradually declined with vibrations,with maximum values at 25,35,and 45℃,which were observed at approximately 96,72,and 48 h,respectively.In addition,Si dissolution fitted the diffusion-controlled reaction model well;as the pH value decreased,the apparent activation energy of Si dissolution decreased,and Si became easier to dissolve.Furthermore,it was concluded that as a weak acid,carbonic acid causes little damage to the mineral structure of montmorillonite.
基金supported by the National Natural Science Foundation of China(2123600121176056)+1 种基金the Programme for 100 Excellent Talents in Universities of Hebei Province(II)(BR2-208)the Natural Science Foundation of Hebei Province(B2015202228)~~
文摘A carbon solid acid catalyst was prepared by the sulfonation of partially carbonized peanut shell with concentrated H2SO4. The structure and acidity of the catalyst were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X‐ray diffraction, thermogravimetric analysis, X‐ray photoelectron spectroscopy, and elemental analysis, which showed that it was an amorphous carbon material composed of aromatic carbon sheets in random orientations. Sulfonic acid groups were present on the surface at a density of 0.81 mmol/g. The carbon solid acid catalyst showed better performance than HZSM‐5 for the esterification of cyclohexene with formic acid. At a3：1 molar ratio of formic acid to cyclohexene, catalyst loading of 0.07 g/mL of cyclohexene, and reaction time of 1 h at 413 K, the cyclohexene conversion was 88.4% with 97.3% selectivity to cyclohexyl formate. The carbon solid acid catalyst showed better reusability than HZSM‐5 because its large pores were minimally affected by the accumulation of oligomerized cyclohexene, which deactivated HZSM‐5. The activity of the carbon solid acid catalyst decreased somewhat in the first two recycles due to the leaching of polycyclic aromatic hydrocarbon containing –SO3H groups and then it remained constant in the following reuse.
基金financial support from the National Natural Science Foundation of China(grant No.21706085)Subsidized Project for Postgraduates’Innovative Fund in Scientific Research of Huaqiao Universitythe Foundation of Key Laboratory of Pulp and Paper Science and Technology of Ministry of Education/Shandong Province of China(grant No.KF201804)。
文摘Two kinds of mesoporous carbon solid acids(LDMCE-SO3H and LDMCS-SO3H)were successfully prepared using masson pine alkali lignin as carbon source by evaporation-induced self-assembly(EISA)and salt-induced selfassembly(SISA)followed by sulfonation,respectively.In terms of preparation process,SISA(self-assembly in water and preparation time of 2 days)is greener and simpler than EISA(self-assembly in ethanol and preparation time of 7 days).The prepared LDMCE-SO3H and LDMCS-SO3H exhibit obvious differences in structural characteristics such as pore channel structure,specific surface area,mesopore volume and the density of-SO3H groups.Furthermore,the catalytic performances of LDMCE-SO3H and LDMCS-SO3H were investigated in the hydrolysis of microcrystalline cellulose in water,and the glucose yields of 48.99%and 54.42%were obtained under the corresponding optimal reaction conditions.More importantly,the glucose yields still reached 28.85%and 30.35%after five runs,and restored to 39.02%and 45.98%through catalysts regeneration,respectively,demonstrating that LDMCE-SO3H and LDMCS-SO3H have excellent recyclability and regenerability.
基金the National Key Project ofScientific and Technical SupportingPrograms Funded by the Ministry of Science & Technology of China (No.2006BAE03B06)the Shanghai International Cooperation of Science and Technology Project (No.06SR07101).
文摘The synthesis of 2, 4-diisopropyl-5,5-dimethy1- 1.3-dioxane through the acetalization of isobutyraldehyde with 2, 2, 4-trimethy1-1,3-pentanediol （TMPD） catalyzed by the novel carbon based acid was first carried out. High conversion （≥98%） and specific selectivity were obtained using the novel carbon based acid, which kept high activity after it was reused 5 times. Moreover. the catalyst could be used to catalyze the acetalization and ketalization of different aldehydes and ketones with superior yield. The yield of several products was over 90%. The novel heterogeneous catalyst has the distinct advantages of high activity, strikingly simple workup procedure, non-pollution, and reusability, which will contribute to the success of the green process greatly.
基金financial support from the Key Project of the National Natural Science Foundation of China(No.52034010)the China Scholarship Council(201906450038)
文摘This work mainly studies the effect of fluid phase momentum transfer mechanisms on the acidizing results,including the retardation effect of the porous structure and the interaction between the fluid phase,such as viscous dissipation and inertial effect.The results show that the acid fluid momentum transfer is influenced by the complex porous structure and fluid viscous dissipation.Eventually,the Stokes-Darcy equation is recommended to be adopted to describe the fluid phase momentum transfer in the following numerical simulation studies of the carbonate acidizing process.Based on this model,a parametric research is carried out to investigate the impact of acid on rock physical characteristics in the stimulation process.Increasing the acid concentration appears to minimize the quantity of acid consumed for the breakthrough.The acid surface reaction rate has a considerable impact on the pore volume to breakthrough and the optimum acid injection rate.The influence of permeability on the acidizing results basically shows a negative correlation with the injection rate.The difference between the acidizing curves of different permeability gradually becomes insignificant with the decrease in injection rate.The existence of isolated fracture and vug significantly reduces acid consumption for the breakthrough.
文摘The dissolution of carbon steel in 5% HCl in the temperature range of 30~90℃ was inhibited by two organic compounds having the general formula: ClR NH2(CH2)n NH2 RCl where R is a benzyl group. The behaviour of these inhibitors in acidic medium were investigated using weight loss method, open circuit potential and linear polarization technique. These inhibitors provided satisfactory corrosion inhibition for carbon steel in hydrochloric acid solutions even at higher temperature and acid concentration (10%). The electrochemical results showed that the polarization resistance (Rp) values increased with increasing inhibitor concentration, also the corrosion current decreased and a higher inhibition efficiency was obtained. The protective properties of these two organic inhibitors were attributed to the chemisorption mechanism
文摘A carbon paste electrode（CPE） chemically modified with multiwall carbon nanotubes and ferrocene（FC） was used as a selective electrochemical sensor for the simultaneous determination of trace amounts of cysteamine（CA） and folic acid（FA）.This modified electrode showed very efficient electrocatalytic activity for the anodic oxidation of CA.The peak current of differential pulse voltammograms of CA and FA increased linearly with their concentration in the ranges of 0.7-200μmol/L CA and 5.0- 700μmol/L FA.The detection limits for CA and FA were 0.3μmol/L and 2.0μmoI/L,respectively.The diffusion coefficient（D） and transfer coefficient（α） of CA were also determined.These conditions are sufficient to allow determination of CA and FA both individually and simultaneously.
基金financially supported by the National Natural Science Foundation of China(No.51641209)。
文摘Humic acid(HA)was carbonized at 300,400 and 500℃ and then functionalized with 1 wt%–12 wt%Fe(Ⅲ)respectively[CHA300/400/500-Fe(Ⅲ)].Adsorption of such Fe(III)-functionalized carbonized HA as adsorbents to aqueous tetracycline(TC:25 mg·L^-1)was studied.The adsorption equilibrium time for CHA400-Fe(Ⅲ)to TC was 6 h faster and the adsorption removal efficiency(Re)was two times higher than that of HA/CHA.The adsorption Reof CHA400-Fe(Ⅲ)loaded 10%iron[CHA400-(10%)Fe(Ⅲ)]to TC could reach 99.8%at 8 h and still kept80.6%after 8 cycles.The adsorption kinetics were well fitted to the pseudo-second-order equation and the adsorption isotherms could be well delineated via Langmuir equations(R^2N 0.99),indicating that the homogeneous chemical adsorption of TC occurred on the adsorbents.The main adsorption mechanisms of TC were complexation Fe(III)and hydrophobic distribution.Electropositive and electronegative repulsion between TC and CHA400-(10%)Fe(Ⅲ)at lowly p H(2)and highly p H(8–10)respectively,leaded to the relatively low adsorption capacity and more notable influence of ion concentration.When the p H was between 4 and 8,TC mainly existed in neutral molecules(TCH2),so the influence of ion concentration was not obvious.The dynamic adsorption results showed that the CHA400-(10%)Fe(Ⅲ)could continuously treat about 2.4 L TC(27 mg·L^-1)wastewater with the effluent concentration as low as 0.068 mg·L^-1.Our study suggested a broad application prospect of a new,effective,lowcost and environment-friendly adsorbent CHA400-(10%)Fe(Ⅲ)for treatment of low-concentration TC polluted wastewater.
基金Project(51008106)supported by the National Natural Science Foundation of China
文摘A batch experiment was conducted to investigate the adsorption of an acid dye(Acid Orange 51) and a basic dye(Safranine) from aqueous solutions by the sludge-based activated carbon(SBAC). The results show that the adsorption of Acid Orange 51 decreases at high p H values, whereas the uptake of Safranine is higher in neutral and alkaline solutions than that in acidic conditions. The adsorption time needed for Safranine to reach equilibrium is shorter than that for Acid Orange 51. The uptakes of the dyes both increase with temperature increasing, indicating that the adsorption process of the dyes onto SBAC is endothermic. The equilibrium data of the dyes are both best represented by the Redlich-Peterson model. At 25 °C, the maximum adsorption capacities of SBAC for Acid Orange 51 and Safranine are 248.70 mg/g and 525.84 mg/g, respectively. The Elovich model is found to best describe the adsorption process of both dyes, indicating that the rate-limiting step involves the chemisorption. It can be concluded that SBAC is a promising material for the removal of Acid Orange 51 and Safranine from aqueous solutions.
文摘In the present work, the behavior of folic acid （FA） molecule adsorbed onto single-walled carbon nanotube （SWCNT） was examined using the DFT-B3LYP/6-31G＊ level. In order to obtain information about the binding features of SWCNT as adsorbent with FA molecule, several studies, including the structural and electronic parameters and also the Atoms in Molecules （AIM） analysis, were performed. It was observed that the FA molecule via hydrogen bond prefers to adsorb on SWCNT with adsorption energy of about -18.70 kcal/mol. The molecular orbitals （HOMO and LUMO）, natural bond orbital （NBO）,analysis, and density of states （DOS） plot indicated that a charge about 0.032 [ e [ is transferred from the FA molecule to the nanotube. After solvation energy calculations, it was found that the presence of a polar solvent causes an increase in FA adsorption on the single-walled carbon nanotube. Topological features such as electron energy density （Hc） and Laplacian of the electron density （V2p~） demonstrate partial covalent nature for H（ll6）...O（10） interaction in the FA/SWCNT complex. According to the calculated results, the single-walled carbon nanotubes are expected to be a potential efficient adsorbent for the adsorption of folic acid drug and also can be used as a suitable drug delivery vehicle within biological systems.
基金the Post-graduate Office of Guilan University(A-384579)for supporting
文摘Nowadays, modified electrodes with metal nanoparticles have appeared as an alternative for the electroanalysis of various compounds. In this study, gold nanoparticles（GNPs） were chosen as interesting metal nanoparticles for modifying carbon paste electrode（CPE）. GNPs and the gold nanoparticles-modified carbon paste electrode（GNPs/CPE） were characterized by UV–Vis spectroscopy, transmission electron microscopy（TEM） and scanning electron microscopy（SEM）. GNPs/CPE as a simple and sensitive electrode was used to study three important biological molecules： folic acid（FA）, uric acid（UA） and ascorbic acid（AA）. Square wave voltammetry（SWV） was used as an accurate technique for quantitative measurements. A good linear relation was observed between anodic peak current（ipa） and FA（5.2 × 10（-6）– 2.5 × 10（-5）M）, UA（1.2 × 10（-6）– 2.1 × 10（-5）M） and AA（1.2 × 10（-6）– 2.5 × 10（-5）M） concentrations in simultaneous determination of these molecules.
文摘The adsorption behavior of folic acid onto（5,0） zigzag and（5,5） armchair carbon nanotube（SWCNT） has been investigated using B3 LYP density functional at the 6-31G＊ level. The adsorption energies,molecular orbital analysis and structural changes at the adsorption site are indicative of covalent adsorption on the zigzag SWCNT surface,while the adsorption is physical on the armchair SWCNT surface. The density of states（DOS） Plot and the quantum molecular descriptors（QMD） are witness to the significant changes in the electronic properties of SWCNT systems after the attachment of adsorbed species to the tube surface. According to the calculated results,the single-walled carbon nanotubes are expected to be a potential efficient adsorbent for the adsorption of folic acid drug and also can be used as a suitable drug delivery vehicle within biological systems.
文摘In this study,Au nanoparticles/poly 5-[（2-hydroxynaphthalen-l-yl）diazenyl]isophthalic acid film modified glassy carbon electrode（AuNPs/poly（NDI）/GCE） has shown excellent electrocatalytic activity toward the oxidation of adrenaline（ADR）,paracetamol（PAC）,and tryptophan（Trp）.The bare glassy carbon electrode（GCE） fails to separate the oxidation peak potentials of these molecules,while the poly（NDI） film modified electrode can resolve them.Electrochemical impedance spectroscopy（EIS）indicates that the charge transfer resistance of the bare electrode decreases as 5-[（2-hydroxynaphthalen-l-yl）diazenyl]isophthalic acid is electropolymerized on the bare electrode.Furthermore,EIS exhibits enhancement of electron transfer kinetics between analytes and the electrode after electrodeposition of Au nanoparticles.Differential pulse voltammetry results show that the electrocatalytic current increases linearly in the ranges of 0.01-680.0 μmol L^-1 for ADR,0.05-498.0 μmol L^-1 for PAC,and 3.0-632.0 μmol L^-1 for Trp;with detection limits（S/N = 3） of 0.009 μmol L^-1,0.005 μmol L^-1,and 0.09 μmol L^-1 for ADR,PAC,and Trp,respectively.The proposed method has been successfully applied for simultaneous determination of ADR,PAC,and Trp in biological samples.
基金supported by National Natural Science Foundation of China(Nos.20975056,21275082 and 81102411)Natural Science Foundation of Shandong(Nos. ZR2011BZ004,ZR2011BQ005)+2 种基金JSPS and NSFC under the Japan-China Scientific Cooperation Program(No.21111140014)State Key Laboratory of Analytical Chemistry for Life Science(No. SKLACLS1110)the National Key Basic Research Development Program of China(973 Special Preliminary Study Plan,No. 2012CB722705)
文摘In this work, a new sample pretreatment method prior to HPLC separations was developed for the determination of auxins in plant samples, Owing to its large surface area and high adsorption capacity, multi-walled carbon nanotube （MWCNT） was chosen as the adsorbent for the extraction of auxins from plant samples. In this study, two important auxins were selected as model analytes, namely indole-3- butyric acid （IBA） and 1-naphthylacetic acid （NAA）. They could be extracted and concentrated due to their π-π stacking interactions with MWCNT. Then HPLC-UV was introduced to detect IBA and NAA after sample pretreatment. Factors that may affect the enrichment efficiency were investigated and optimized. Comparative studies showed that MWCNT was superior to CI 8 for the extraction of the two analytes. Validation experiments showed that the optimized method had good linearity （0.9998 and 0.9960）, high recovery （81.4%-85.4%）, and low detection limits （0.0030 mg/L and 0.0012 mg/L）. The results indicated that the novel method had advantages of convenience, good sensitivity, high efficiency, and it was feasible for the determination of auxins in plant samples.
基金supported by the Energy Efficiency&Resources(No.20212010200010)the“Development of Intelligential Diagnosis,Abandonment Process and Management Technology for Decrepit Oil and Gas Wells”(No.20216110100010)of the Korea Institute of Energy Technology EvaluationPlanning(KETEP)grant funded by the Korean Government Ministry of Trade,Industry&Energy.
文摘Polymers play an important role in hybrid enhanced oil recovery (EOR), which involves both a polymer and low-salinity water. Because the polymer commonly used for low-salinity polymer flooding (LSPF) is strongly sensitive to brine pH, its efficiency can deteriorate in carbonate reservoirs containing highly acidic formation water. In this study, polymer efficiency in an acidic carbonate reservoir was investigated experimentally for different salinity levels and SO42− concentrations. Results indicated that lowering salinity improved polymer stability, resulting in less polymer adsorption, greater wettability alteration, and ultimately, higher oil recovery. However, low salinity may not be desirable for LSPF if the injected fluid does not contain a sufficient number of sulfate (SO42−) ions. Analysis of polymer efficiency showed that more oil can be produced with the same polymer concentration by adjusting the SO42− content. Therefore, when river water, which is relatively easily available in onshore fields, is designed to be injected into an acidic carbonate reservoir, the LSPF method proposed in this study can be a reliable and environmentally friendly method with addition of a sufficient number of SO42− ions to river water.
基金the financial support from the Ministry of Science and Technology of China (grants 2012CB215500 and 2013CB933100)the National Natural Science Foundation of China (grants 21573222 and 21103178)
文摘Replacing platinum for catalyzing hydrogen evolution reaction （HER） in acidic medium remains great chal- lenges. Herein, we prepared few-layered MoS2 by ball milling as an efficient catalyst for HER in acidic medium, The activity of as-prepared MoS2 had a strong dependence on the ball milling time, Furthermore, Ketjen Black EC 300J was added into the ball-milled MoS2 followed by a second ball milling, and the resultant MoS2/carbon black hybrid material showed a much higher HER activity than MoS2 and carbon black alone. The enhanced activity of the MoS2/carbon black hybrid material was attributed to the increased abundance of catalytic edge sites of MoS） and excellent electrical coupling to the underlving carbon network.
基金Funded by the National Natural Science Foundation of China(No.51273155)the Fundamental Research Funds for the Central Universities(No.2012-Ia-022)
文摘A sensitive and selective method for the determination of ascorbic acid（AA） using [Cu（phen）2]2＋/multiwalled carbon nanotubes modified glassy carbon electrode was developed. Electrochemical behavior and surface characteristics of the modified electrode were studied using scanning electrode microscopy（SEM）, electrochemical impedance spectroscopy（EIS） and cyclic voltammetry（CV）. The experimental results showed that the modified electrode enhanced the electrochemical response of AA and exhibited good analytical performance for AA determination from 10 to 1 042 ？mol/L with a low detection limit of 9.67μmol/L（S/N=3）. The modified electrode was also applied to the determination of AA in the Vitamin tablets and showed good recovery.
基金supported by the National Natural Science Foundation of China(No.20977043,20777033)the Opening Funding of State Key Laboratory of Pollution Control and Resource Reuse(No.PCRRF12012)
文摘The aggregation of multi-walled carbon nanotubes （MWCNTs） in the aqueous phase not only inhibits their extensive utilization in various aspects but also dominates their environmental fate and transport.The role of surfactants at low concentration in the aggregation of MWCNTs has been studied,however the effect of perfluorinated surfactants at low concentration is uncertain.To understand this interfacial phenomenon,the influences of perfluorooctanoic acid （PFOA）,and sodium dodecyl sulfate （SDS） as a control,on MWCNT aggregation in the aqueous phase were examined by the UV absorbency method.Influences of pH and cationic species on the critical coagulation concentration （CCC） value were evaluated.The CCC values were dependent on the concentration of PFOA,however a pronounced effect of SDS concentration on the CCC values was not observed.The CCC values of the MWCNTs were 51.6 mmol/L in NaCl and 0.28 mmol/L in CaCl 2 solutions,which suggested pronounced differences in the effects of Na＋ and Ca2＋ ions on the aggregation of the MWCNTs.The presence of both PFOA and SDS significantly decreased the CCC values of the MWCNTs in NaCl solution.The aggregation of the MWCNTs took place under acidic conditions and was not notably altered under neutral and alkaline conditions due to the electrostatic repulsion of deprotonated functional groups on the surface of the MWCNTs.
文摘A new ascorbic acid sensor constituted of carbon paste and Fe(Ⅲ)Y zeolite was studied.The characters of the sensor such as linear range. potential window、apparen Michaelis constant、response time、stability and accuracy wee investigated. The experimental results indicate that the analytical performance of the sensor is satisfactory.
