Sorption kinetics of organic compounds on biochars is important for understanding the retardation of mobility and bioavailability of organic compounds.Herein,sorption kinetics of 1,3,5-trinitrobenzene on biochars prep...Sorption kinetics of organic compounds on biochars is important for understanding the retardation of mobility and bioavailability of organic compounds.Herein,sorption kinetics of 1,3,5-trinitrobenzene on biochars prepared from 200 to 700℃was investigated to explore the sorption process.Loose partition matrix and condensed partition matrix were formed at relatively low and moderate temperatures,respectively.However,biochars produced at relatively high temperatures formed rich pore structures.Therefore,sorption equilibrium time of 1,3,5-trinitrobenzene increased with increasing preparation temperature from 200 to 350℃due to the slower diffusion rate in the more condensed matrix,and then decreased when preparation temperature was higher than 400℃because of the faster adsorption rate in the greater number of pores.Linear positive relationship between matrix diffusion rates of 1,3,5-trinitrobenzene on biochars prepared at 200,250,300,350℃and H/C ratios of biochars was observed,suggesting that the inhibition of partition process was caused by the condensed matrix in biochars.Linear positive relationships between adsorption rates(i.e.,fast outer diffusion rate and slow pore diffusion rate)of 1,3,5-trinitrobenzene on biochars prepared at 400,450,550,700℃and graphite defects of biochars were observed,because the increase of graphite defects of biochars could promote the adsorption by increasing the quantity of fast diffusion channels and sorption sites.This study reveals the underlying mechanisms of sorption kinetics for organic compounds with relatively large size on biochars,which has potential guidance for the application of biochars and prediction of the environmental risks of organic compounds.展开更多
The sorption and desorption kinetics of dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP) and phenol on water and sediment interface were studied using two compartment model in this paper. ...The sorption and desorption kinetics of dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP) and phenol on water and sediment interface were studied using two compartment model in this paper. The results showed that the sorption coefficients of DMP, DEP, DBP and phenol measured by batch equilibrium method were 16.79, 24.55, 132 and 0.65μg 1-1/n · g -1 · ml -1/n , the sorption and desorption kinetic constants of DMP, DEP, DBP, phenol were 0.0248, 0.0357, 0.0727, 0.014ml·cm -2 ·h -1 and 0.000512, 0.000754, 0.00127, 0 000899h -1 at static condition respectively; and the sorption and desorption kinetics constants of above chemicals were 0 279, 0.382, 0.496, 0.0904ml·cm -2 ·h -1 and 0.0442, 0.0031, 0.00116, 0.00247h -1 at flow water condition respectively.展开更多
Slow release of emerging contaminants limits their accessibility from soil to pore water,constraining the treatment efficiency of physio-chemical treatment sites.DC fields mobilize organic contaminants and influence t...Slow release of emerging contaminants limits their accessibility from soil to pore water,constraining the treatment efficiency of physio-chemical treatment sites.DC fields mobilize organic contaminants and influence their interactions with geo-matrices such as zeolites.Poor knowledge,however,exists on the joint application of heating and electrokinetic approaches on perfluorooctanoic acid(PFOA)transport in porous media.Here,we investigated electrokinetic PFOA transport in zeolite-filled percolation columns at varying temperatures.Variations of pseudo-second-order kinetic constants(kPSO)were correlated to the liquid viscosity variations(η)and elctroosmotic flow velocities(vEOF).Applying DC fields and elevated temperature significantly(>37%)decreased PFOA sorption to zeolite.A good correlation betweenη,vEOF,and kPSO was found and used to develop an approach interlinking the three parameters to predict the joint effects of DC fields and temperature on PFOA sorption kinetics.These findings may give rise to future applications for better tailoring PFOA transport in environmental biotechnology.展开更多
Perfluorooctane sulfonate（PFOS） has attracted increasing concern in recent years due to its world-wide distribution, persistence, bioaccumulation and potential toxicity. The influence of sorbent properties on the ad...Perfluorooctane sulfonate（PFOS） has attracted increasing concern in recent years due to its world-wide distribution, persistence, bioaccumulation and potential toxicity. The influence of sorbent properties on the adsorptive elimination of PFOS from wastewater by activated carbons, polymer adsorbents and anion exchange resins was investigated with regard to their isotherms and kinetics. The batch and column tests were combined with physicochemical characterization methods, e.g., N2 physisorption, mercury porosimetry, infrared spectroscopy, differential scanning calorimetry, titrations, as well as modeling. Sorption kinetics was successfully modelled applying the linear driving force（LDF） approach for surface diffusion after introducing a load dependency of the mass transfer coefficient βs.The big difference in the initial mass transfer coefficient βs,0, when non-functionalized adsorbents and ion-exchange resins are compared, suggests that the presence of functional groups impedes the intraparticle mass transport. The more functional groups a resin possesses and the longer the alkyl moieties are the bigger is the decrease in sorption rate.But the selectivity for PFOS sorption is increasing when the character of the functional groups becomes more hydrophobic. Accordingly, ion exchange and hydrophobic interaction were found to be involved in the sorption processes on resins, while PFOS is only physisorptively bound to activated carbons and polymer adsorbents. In agreement with the different adsorption mechanisms, resins possess higher total sorption capacities than adsorbents. Hence, the latter ones are rendered more effective in PFOS elimination at concentrations in the low μg/L range, due to a less pronounced convex curvature of the sorption isotherm in this concentration range.展开更多
Kapok fibers have been acetylated for oil spill cleanup in the aqueous environment. The structures of raw and acetylated kapok fiber were characterized using Fourier transform infrared （FT-IR） spectroscopy and scann...Kapok fibers have been acetylated for oil spill cleanup in the aqueous environment. The structures of raw and acetylated kapok fiber were characterized using Fourier transform infrared （FT-IR） spectroscopy and scanning electron microscopy （SEM）. Without severe damage to the lumen structures, the kapok fibers were successfully acetylated and the resulting fibers exhibited a better oil sorption capacity than raw fibers for diesel and soybean oil. Compared with high viscosity soybean oil, low viscosity diesel shows a better affinity to the surface of acetylated fibers. Sorption kinetics is fitted well by the pseudo second-order model, and the equilibrium data can be described by the Freundlich isotherm model. The results implied that acetylated kapok fiber can be used as the substitute for non-biodegradable oil sorption materials.展开更多
The present study describes the use of two commercially available lignins,namely,alkali and organosolv lignin,for the removal of2,4-dinitroanisole（DNAN）,a chemical widely used by the military and the dye industry,fr...The present study describes the use of two commercially available lignins,namely,alkali and organosolv lignin,for the removal of2,4-dinitroanisole（DNAN）,a chemical widely used by the military and the dye industry,from water.Sorption of DNAN on bothlignins reached equilibrium within 10 hr and followed pseudo second-order kinetics with sorption being faster with alkali than withorganosolv lignin,i.e.k2 10.3 and 0.3 g/（mg·hr）,respectively.In a separate study we investigated sorption of DNAN between 10 and40 C and found that the removal of DNAN by organosolv lignin increased from 0.8 to 7.5 mg/g but reduced slightly from 8.5 to 7.6mg/g in the case of alkali lignin.Sorption isotherms for either alkali or organosolv lignin best fitted Freundlich equation with enthalpyof formation,H0 equaled to 14 or 80 kJ/mol.To help understand DNAN sorption mechanisms we characterized the two lignins byelemental analysis,BET nitrogen adsorption-desorption and 31P NMR.Variations in elemental compositions between the two ligninsindicated that alkali lignin should have more sites（O-and S-containing functionalities） for H-bonding.The BET surface area andcalculated total pore volume of alkali lignin were almost 10 times greater than that of organosolv lignin suggesting that alkali ligninshould provide more sites for sorption.31P NMR showed that organosolv lignin contains more phenolic-OH groups than alkali lignin,i.e.,70% and 45%,respectively.The variations in the type of OH groups between the two lignins might have affected the strength ofH-bonding between DNAN and the type of lignin used.展开更多
Carbon dots are prepared and immobilized onto spherical SiO_2 through a one-step thermal oxidation and then decorated with metallothionein（MT）, a protein with high affinity towards thiophilic metals. The MT-carbon d...Carbon dots are prepared and immobilized onto spherical SiO_2 through a one-step thermal oxidation and then decorated with metallothionein（MT）, a protein with high affinity towards thiophilic metals. The MT-carbon dots composites are characterized by means of FT-IR, SEM and TGA, giving rise to a MT loading amount of 823 μg g^（-1）. The adsorption of cadmium by the composites is a fast process and follows Langmuir model. In comparison with native SiO_2, a 2- and 2.4-folds improvement on the static and dynamic adsorption capacity of the composites for cadmium are obtained, respectively. Moreover,the adsorption efficiency is not affected by the presence of other metals. Finally, the composites are successfully applied for the removal of cadmium in a series of environmental water samples.展开更多
A soil batch experiment was conducted to investigate both separate and compound effects of three types of surfactants: anionic dodecylbenzene sulfonic acid sodiumsalt (DBSS), cationic cetyltrimethylammonium bromide (C...A soil batch experiment was conducted to investigate both separate and compound effects of three types of surfactants: anionic dodecylbenzene sulfonic acid sodiumsalt (DBSS), cationic cetyltrimethylammonium bromide (CTAB), and non-ionic nonyl phenol polyethyleneoxy ether (TX-100), as well as ethylenediaminetetraacetic acid (EDTA) on cadmium solubility, sorption kinetics, and sorption-desorption behavior in purple soil. The results indicated that both individual application of the three types of surfactants and surfactants combined with EDTA could stimulate Cd extraction from the soil with a general effectiveness ranking of EDTA/TX-100 > EDTA/DBSS > EDTA/CTAB > EDTA > TX-100 > DBSS > CTAB. Further study showed that the compound application of surfactants and EDTA had stronger (P < 0.05) effects on Cd solubility than those added individually. The application of surfactants and EDTA to purple soil (P < 0.05) decreased the proportion of Cd sorbed, while their effectiveness ranking was similar to that of enhanced solubilization. The sorption kinetics of Cd in purple soil was best described by the double-constant equation, while the Freundlich equation gave an excellent fit to the sorption isotherm curves. Therefore, surfactant-enhanced remediation of Cd contaminated soil is feasible and further research should be conducted.展开更多
A numerical investigation of the unsteady motion of a deformed drop released freely in another quiescent liquid contaminated by surfactant is presented in this paper. The finite difference method was used to solve num...A numerical investigation of the unsteady motion of a deformed drop released freely in another quiescent liquid contaminated by surfactant is presented in this paper. The finite difference method was used to solve numerically the coupled time-dependent Navier-Stokes and convective-diffusion equations in a body-fitted orthogonal coordinate system. Numerical simulation was conducted on the experimental cases, in which MIBK drops with the size ranging from 1.24 mm to 1.97 mm rose and accelerated freely in pure water and in dilute sodium dodecyl sulphate (SDS) aqueous solution. The applicability of the numerical scheme was validated by the agreement between the simulation results and the experimental data. Both the numerical and experimental results showed that the velocitytime profile exhibited a maximum rising velocity for drops in SDS solutions, which was close to the terminal velocity in pure water, before it dropped down to a steady-state value. The effect of the sorption kinetics of surfactant on the accelerating motion was also evaluated. It is also suggested that introduction of virtual mass force into the formulation improved obviously the precision of numerical simulation of transient drop motion.展开更多
In order to evaluate the effects of La-involvement on biomass pyrolysis behaviors and properties of produced biochar, oak sawdust（OS） and corn straw（CS） were employed for thermogravimetric-differential thermogravi...In order to evaluate the effects of La-involvement on biomass pyrolysis behaviors and properties of produced biochar, oak sawdust（OS） and corn straw（CS） were employed for thermogravimetric-differential thermogravimetric（TG-DTG） analysis and producing biochar with/without La-involvement. Results indicated the initial and final temperatures were shifted toward lower temperature as LaCl3 was involved in pyrolysis. Mass loss and average mass loss rate during pyrolysis decreased with La-involvement. The kinetics indicated that the first-order reaction kinetic model well matched the pyrolysis process. As La-involved OS and CS were employed, their apparent activation energies（Ea） were reduced, and their pyrolysis characteristic index（I） were higher comparing with the OS and CS without La-involvement. Based on the produced biochar, the yield and ash content were increased by La-involvement, and the O/C ratio and iodine sorption value（ISV） were also enhanced. Obviously, the loaded LaCl3 could facilitate pyrolysis process, and the produced biochar exhibited a great adsorption potential in aqueous solution. According to the results from FT-IR（Fourier transform infrared spectroscopy） analysis, La in pyrolysis functioned as accelerating lignin decomposition via condensing –OH, breaking aliphatic C–H and aromatic rings on lignin, cutting the links of C-O-C among the monomers in lignocellulose. LaCl3 was finally converted to La2O3 in biochar after pyrolysis.展开更多
Recently,high-entropy alloys(HEAs)designed by the concepts of unique entropy-stabilized mechanisms,started to attract widespread interests for their hydrogen storage properties.HEAs with body-centered cubic(BCC)struct...Recently,high-entropy alloys(HEAs)designed by the concepts of unique entropy-stabilized mechanisms,started to attract widespread interests for their hydrogen storage properties.HEAs with body-centered cubic(BCC)structures present a high potential for hydrogen storage due to the high hydrogen-to-metal ratio(up to H/M=2)and vastness of compositions.Although many studies reported rapid absorption kinetics,the investigation of hydrogen desorption is missing,especially in BCC HEAs.We have investigated the crystal structure,microstructure and hydrogen storage performance of a series of HEAs in the Ti-V-Nb-Cr system.Three types of TiVCrNb HEAs(Ti_(4)V_(3)NbCr_(2),Ti_(3)V_(3)Nb2Cr_(2),Ti_(2)V_(3)Nb_(3)Cr_(2))with close atomic radii and different valence electron concentrations(VECs)were designed with single BCC phase by CALPHAD method.The three alloys with fast hydrogen absorption kinetics reach the H/M ratio up to 2.Particularly,Ti_(4)V_(3)NbCr_(2)alloy shows the hydrogen storage capacity of 3.7 wt%,higher than other HEAs ever reported.The dehydrogenation activation energy of HEAs’hydride has been proved to decrease with decreasing VEC,which may be due to the weakening of alloy atom and H atom.Moreover,Ti_(4)V_(3)NbCr_(2)M(M=Mn,Fe,Ni)alloys were also synthesized to destabilize hydrides.The addition of Mn,Fe and Ni lead to precipitation of Laves phase,however,the kinetics did not improve further because of their own excellent hydrogen absorption.With increasing the content of Laves phase,there appear more pathways for hydrogen desorption so that the hydrides are more easily dissociated,which may provide new insights into how to achieve hydrogen desorption in BCC HEAs at room temperature.展开更多
Water-solid interactions play a key role in determining the efficacy of inert dusts. The critical water activity(Awc) for phase transition in amorphous materials is an important characteristic of amorphous inert dusts...Water-solid interactions play a key role in determining the efficacy of inert dusts. The critical water activity(Awc) for phase transition in amorphous materials is an important characteristic of amorphous inert dusts used as grain protectants. As water activity(Aw) rises above Awc, amorphous dusts undergo a transition from glassy or vitreous state to rubbery state. Such a transition induces dramatic changes in material properties, texture and structure, and hence impact their performance as grain protectants. Full Dynamic Dewpoint Isotherms(DDI) of a synthetic amorphous zeolite intended for grain protection were generated using the Vapor Sorption Analyzer(VSA) to determine Awcby investigating the relationship between moisture content and Awat constant temperatures. Sorption experimental data was fitted using three sorption isotherm models: Guggenheim-Anderson-de Boer(GAB), Double Log Polynomial(DLP),and Brunauer-Emmet-Teller(BET). DLP model was the best model to estimate zeolite and wheat sorption isotherms. Full sorption isotherms of zeolite and wheat obtained at 25, 35, and 45 °C clearly showed the hysteresis phenomenon. The hysteresis loops were of type H3 for wheat, and of type H4 for zeolite powder. The intensity of hysteresis remained unchanged for wheat. However, the intensity of hysteresis decreased with increasing temperatures during water adsorption by porous zeolite powder. Monolayer moisture content values for each sorption direction were provided only by GAB and BET models and indicated a decrease in monolayer moisture content with an increase in temperature. The net isosteric heats of sorption and the differential enthalpy of zeolite estimated by the Clausius–Clapeyron equation and determined graphically decreased with increasing moisture content. Conversely, differential entropy of zeolite decreased with increasing zeolite moisture content. The optimal moisture content of inert dust for grain treatment was dependent on wheat moisture content and wheat storage temperature. This is the first time that a synthetic amorphous dust is being investigated for grain protection.Our results recommend the application of inert dusts at the optimal moisture content to mitigate moisture migration within the system "wheat-dust", thus ensuring dust maximal efficacy.展开更多
Titration of pesticides onto sorption sites can determine sorption capacities on soils. Previous studies have tracked the sorption capacities and detailed kinetics of the uptake of atrazine and its decomposition bypro...Titration of pesticides onto sorption sites can determine sorption capacities on soils. Previous studies have tracked the sorption capacities and detailed kinetics of the uptake of atrazine and its decomposition byproduct hydroxyatrazine on different soils, including measurements made using LC-MS/MS. These studies have now been extended to explore sorption-desorption equilibria for a mixture of pesticides from soil using LC-MS/MS. Desorption of sorbed pesticide residues has environmental regulatory implications for pesticide levels in runoff, or for longer term sequestration, partitioning, and transport. The uptake of pesticides by the soil at equilibrium was measured for a number of different concentrations, and sorption capacities were estimated. Pesticide-soil interaction studies were conducted by exposing standard stock solutions of pesticide mixtures to a characterized Nova Scotia soil. The mixture contained atrazine and dicamba. Initial aqueous mixture concentrations ranging from 5 × 10<sup>-9</sup> to 10<sup>-5</sup> M or greater were exposed to 25 mg aliquots of soil and allowed to reach equilibrium. The total uptake of each pesticide was measured indirectly, by measuring the concentration remaining in solution using an IONICS 3Q 120 triple quadrupole mass spectrometer. These sorption capacities have been supplemented by studies examining equilibrium recovery rates from soil aliquots with different initial uptakes. This gives insight into the fraction of easily recoverable (reversibly sorbed) pesticides on the soil. Proper quantification of equilibrium constants and kinetic rate coefficients using high performance LC-MS/MS facilitates the construction of accurate, predictive models. Predictive kinetic models can successfully mimic the experimental results for solution concentration, labile sorption, and intra-particle diffusion, and could be used to guide regulatory practices.展开更多
基金the National Key Research and Development Program of China(2021YFC1809204 and 2017YFA0207001)the National Natural Science Foundation of China(21777138)the Key Research and Development Program of Zhejiang Province,China(2020C03011 and 2021C03167).
文摘Sorption kinetics of organic compounds on biochars is important for understanding the retardation of mobility and bioavailability of organic compounds.Herein,sorption kinetics of 1,3,5-trinitrobenzene on biochars prepared from 200 to 700℃was investigated to explore the sorption process.Loose partition matrix and condensed partition matrix were formed at relatively low and moderate temperatures,respectively.However,biochars produced at relatively high temperatures formed rich pore structures.Therefore,sorption equilibrium time of 1,3,5-trinitrobenzene increased with increasing preparation temperature from 200 to 350℃due to the slower diffusion rate in the more condensed matrix,and then decreased when preparation temperature was higher than 400℃because of the faster adsorption rate in the greater number of pores.Linear positive relationship between matrix diffusion rates of 1,3,5-trinitrobenzene on biochars prepared at 200,250,300,350℃and H/C ratios of biochars was observed,suggesting that the inhibition of partition process was caused by the condensed matrix in biochars.Linear positive relationships between adsorption rates(i.e.,fast outer diffusion rate and slow pore diffusion rate)of 1,3,5-trinitrobenzene on biochars prepared at 400,450,550,700℃and graphite defects of biochars were observed,because the increase of graphite defects of biochars could promote the adsorption by increasing the quantity of fast diffusion channels and sorption sites.This study reveals the underlying mechanisms of sorption kinetics for organic compounds with relatively large size on biochars,which has potential guidance for the application of biochars and prediction of the environmental risks of organic compounds.
文摘The sorption and desorption kinetics of dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP) and phenol on water and sediment interface were studied using two compartment model in this paper. The results showed that the sorption coefficients of DMP, DEP, DBP and phenol measured by batch equilibrium method were 16.79, 24.55, 132 and 0.65μg 1-1/n · g -1 · ml -1/n , the sorption and desorption kinetic constants of DMP, DEP, DBP, phenol were 0.0248, 0.0357, 0.0727, 0.014ml·cm -2 ·h -1 and 0.000512, 0.000754, 0.00127, 0 000899h -1 at static condition respectively; and the sorption and desorption kinetics constants of above chemicals were 0 279, 0.382, 0.496, 0.0904ml·cm -2 ·h -1 and 0.0442, 0.0031, 0.00116, 0.00247h -1 at flow water condition respectively.
基金supported by the National Natural Science Foundation of China(No.42277011)the fellowship of the China Postdoctoral Science Foundation(Nos.2023T160667 and 2022M713300)。
文摘Slow release of emerging contaminants limits their accessibility from soil to pore water,constraining the treatment efficiency of physio-chemical treatment sites.DC fields mobilize organic contaminants and influence their interactions with geo-matrices such as zeolites.Poor knowledge,however,exists on the joint application of heating and electrokinetic approaches on perfluorooctanoic acid(PFOA)transport in porous media.Here,we investigated electrokinetic PFOA transport in zeolite-filled percolation columns at varying temperatures.Variations of pseudo-second-order kinetic constants(kPSO)were correlated to the liquid viscosity variations(η)and elctroosmotic flow velocities(vEOF).Applying DC fields and elevated temperature significantly(>37%)decreased PFOA sorption to zeolite.A good correlation betweenη,vEOF,and kPSO was found and used to develop an approach interlinking the three parameters to predict the joint effects of DC fields and temperature on PFOA sorption kinetics.These findings may give rise to future applications for better tailoring PFOA transport in environmental biotechnology.
基金the funding of the present study by the German Federation of Industrial Research Associations(AiF)(FKZ VP 2470101RH9)
文摘Perfluorooctane sulfonate（PFOS） has attracted increasing concern in recent years due to its world-wide distribution, persistence, bioaccumulation and potential toxicity. The influence of sorbent properties on the adsorptive elimination of PFOS from wastewater by activated carbons, polymer adsorbents and anion exchange resins was investigated with regard to their isotherms and kinetics. The batch and column tests were combined with physicochemical characterization methods, e.g., N2 physisorption, mercury porosimetry, infrared spectroscopy, differential scanning calorimetry, titrations, as well as modeling. Sorption kinetics was successfully modelled applying the linear driving force（LDF） approach for surface diffusion after introducing a load dependency of the mass transfer coefficient βs.The big difference in the initial mass transfer coefficient βs,0, when non-functionalized adsorbents and ion-exchange resins are compared, suggests that the presence of functional groups impedes the intraparticle mass transport. The more functional groups a resin possesses and the longer the alkyl moieties are the bigger is the decrease in sorption rate.But the selectivity for PFOS sorption is increasing when the character of the functional groups becomes more hydrophobic. Accordingly, ion exchange and hydrophobic interaction were found to be involved in the sorption processes on resins, while PFOS is only physisorptively bound to activated carbons and polymer adsorbents. In agreement with the different adsorption mechanisms, resins possess higher total sorption capacities than adsorbents. Hence, the latter ones are rendered more effective in PFOS elimination at concentrations in the low μg/L range, due to a less pronounced convex curvature of the sorption isotherm in this concentration range.
基金supported by the National Natural Science Foundation of China (No.21107116)the Science and Technology Support Project of Jiangsu Provincial Sci.&Tech.Department (No.BY2010012)
文摘Kapok fibers have been acetylated for oil spill cleanup in the aqueous environment. The structures of raw and acetylated kapok fiber were characterized using Fourier transform infrared （FT-IR） spectroscopy and scanning electron microscopy （SEM）. Without severe damage to the lumen structures, the kapok fibers were successfully acetylated and the resulting fibers exhibited a better oil sorption capacity than raw fibers for diesel and soybean oil. Compared with high viscosity soybean oil, low viscosity diesel shows a better affinity to the surface of acetylated fibers. Sorption kinetics is fitted well by the pseudo second-order model, and the equilibrium data can be described by the Freundlich isotherm model. The results implied that acetylated kapok fiber can be used as the substitute for non-biodegradable oil sorption materials.
基金Funding was provided by the Defense Research and Development Canada
文摘The present study describes the use of two commercially available lignins,namely,alkali and organosolv lignin,for the removal of2,4-dinitroanisole（DNAN）,a chemical widely used by the military and the dye industry,from water.Sorption of DNAN on bothlignins reached equilibrium within 10 hr and followed pseudo second-order kinetics with sorption being faster with alkali than withorganosolv lignin,i.e.k2 10.3 and 0.3 g/（mg·hr）,respectively.In a separate study we investigated sorption of DNAN between 10 and40 C and found that the removal of DNAN by organosolv lignin increased from 0.8 to 7.5 mg/g but reduced slightly from 8.5 to 7.6mg/g in the case of alkali lignin.Sorption isotherms for either alkali or organosolv lignin best fitted Freundlich equation with enthalpyof formation,H0 equaled to 14 or 80 kJ/mol.To help understand DNAN sorption mechanisms we characterized the two lignins byelemental analysis,BET nitrogen adsorption-desorption and 31P NMR.Variations in elemental compositions between the two ligninsindicated that alkali lignin should have more sites（O-and S-containing functionalities） for H-bonding.The BET surface area andcalculated total pore volume of alkali lignin were almost 10 times greater than that of organosolv lignin suggesting that alkali ligninshould provide more sites for sorption.31P NMR showed that organosolv lignin contains more phenolic-OH groups than alkali lignin,i.e.,70% and 45%,respectively.The variations in the type of OH groups between the two lignins might have affected the strength ofH-bonding between DNAN and the type of lignin used.
基金Financial support from the National Natural Science Foundation of China(Nos.21375013,21235001,21405010)the Fundamental Research Funds for the Central Universities(Nos.N130105002,N140504003,N140505003,N141008001)are highly appreciated
文摘Carbon dots are prepared and immobilized onto spherical SiO_2 through a one-step thermal oxidation and then decorated with metallothionein（MT）, a protein with high affinity towards thiophilic metals. The MT-carbon dots composites are characterized by means of FT-IR, SEM and TGA, giving rise to a MT loading amount of 823 μg g^（-1）. The adsorption of cadmium by the composites is a fast process and follows Langmuir model. In comparison with native SiO_2, a 2- and 2.4-folds improvement on the static and dynamic adsorption capacity of the composites for cadmium are obtained, respectively. Moreover,the adsorption efficiency is not affected by the presence of other metals. Finally, the composites are successfully applied for the removal of cadmium in a series of environmental water samples.
基金Project supported by the Foundation for University Key Teachers through the Education Committee of Chongqing,China (No. 110758).
文摘A soil batch experiment was conducted to investigate both separate and compound effects of three types of surfactants: anionic dodecylbenzene sulfonic acid sodiumsalt (DBSS), cationic cetyltrimethylammonium bromide (CTAB), and non-ionic nonyl phenol polyethyleneoxy ether (TX-100), as well as ethylenediaminetetraacetic acid (EDTA) on cadmium solubility, sorption kinetics, and sorption-desorption behavior in purple soil. The results indicated that both individual application of the three types of surfactants and surfactants combined with EDTA could stimulate Cd extraction from the soil with a general effectiveness ranking of EDTA/TX-100 > EDTA/DBSS > EDTA/CTAB > EDTA > TX-100 > DBSS > CTAB. Further study showed that the compound application of surfactants and EDTA had stronger (P < 0.05) effects on Cd solubility than those added individually. The application of surfactants and EDTA to purple soil (P < 0.05) decreased the proportion of Cd sorbed, while their effectiveness ranking was similar to that of enhanced solubilization. The sorption kinetics of Cd in purple soil was best described by the double-constant equation, while the Freundlich equation gave an excellent fit to the sorption isotherm curves. Therefore, surfactant-enhanced remediation of Cd contaminated soil is feasible and further research should be conducted.
基金Supported by the National Natural Science Foundation of China(No.20236050)
文摘A numerical investigation of the unsteady motion of a deformed drop released freely in another quiescent liquid contaminated by surfactant is presented in this paper. The finite difference method was used to solve numerically the coupled time-dependent Navier-Stokes and convective-diffusion equations in a body-fitted orthogonal coordinate system. Numerical simulation was conducted on the experimental cases, in which MIBK drops with the size ranging from 1.24 mm to 1.97 mm rose and accelerated freely in pure water and in dilute sodium dodecyl sulphate (SDS) aqueous solution. The applicability of the numerical scheme was validated by the agreement between the simulation results and the experimental data. Both the numerical and experimental results showed that the velocitytime profile exhibited a maximum rising velocity for drops in SDS solutions, which was close to the terminal velocity in pure water, before it dropped down to a steady-state value. The effect of the sorption kinetics of surfactant on the accelerating motion was also evaluated. It is also suggested that introduction of virtual mass force into the formulation improved obviously the precision of numerical simulation of transient drop motion.
基金Project supported by Key R&D Projects of Sichuan Province from the Science&Technology Department of Sichuan Province(2017SZ0028)Program for Changjiang Scholars and Innovative Research Team in University from the Ministry and Education of China(IRT13083)
文摘In order to evaluate the effects of La-involvement on biomass pyrolysis behaviors and properties of produced biochar, oak sawdust（OS） and corn straw（CS） were employed for thermogravimetric-differential thermogravimetric（TG-DTG） analysis and producing biochar with/without La-involvement. Results indicated the initial and final temperatures were shifted toward lower temperature as LaCl3 was involved in pyrolysis. Mass loss and average mass loss rate during pyrolysis decreased with La-involvement. The kinetics indicated that the first-order reaction kinetic model well matched the pyrolysis process. As La-involved OS and CS were employed, their apparent activation energies（Ea） were reduced, and their pyrolysis characteristic index（I） were higher comparing with the OS and CS without La-involvement. Based on the produced biochar, the yield and ash content were increased by La-involvement, and the O/C ratio and iodine sorption value（ISV） were also enhanced. Obviously, the loaded LaCl3 could facilitate pyrolysis process, and the produced biochar exhibited a great adsorption potential in aqueous solution. According to the results from FT-IR（Fourier transform infrared spectroscopy） analysis, La in pyrolysis functioned as accelerating lignin decomposition via condensing –OH, breaking aliphatic C–H and aromatic rings on lignin, cutting the links of C-O-C among the monomers in lignocellulose. LaCl3 was finally converted to La2O3 in biochar after pyrolysis.
基金This work was financially supported by the National Natural Science Foundation of China(No.51701018)the National Key Research and Development Program of China(No.2018YFB0703400).
文摘Recently,high-entropy alloys(HEAs)designed by the concepts of unique entropy-stabilized mechanisms,started to attract widespread interests for their hydrogen storage properties.HEAs with body-centered cubic(BCC)structures present a high potential for hydrogen storage due to the high hydrogen-to-metal ratio(up to H/M=2)and vastness of compositions.Although many studies reported rapid absorption kinetics,the investigation of hydrogen desorption is missing,especially in BCC HEAs.We have investigated the crystal structure,microstructure and hydrogen storage performance of a series of HEAs in the Ti-V-Nb-Cr system.Three types of TiVCrNb HEAs(Ti_(4)V_(3)NbCr_(2),Ti_(3)V_(3)Nb2Cr_(2),Ti_(2)V_(3)Nb_(3)Cr_(2))with close atomic radii and different valence electron concentrations(VECs)were designed with single BCC phase by CALPHAD method.The three alloys with fast hydrogen absorption kinetics reach the H/M ratio up to 2.Particularly,Ti_(4)V_(3)NbCr_(2)alloy shows the hydrogen storage capacity of 3.7 wt%,higher than other HEAs ever reported.The dehydrogenation activation energy of HEAs’hydride has been proved to decrease with decreasing VEC,which may be due to the weakening of alloy atom and H atom.Moreover,Ti_(4)V_(3)NbCr_(2)M(M=Mn,Fe,Ni)alloys were also synthesized to destabilize hydrides.The addition of Mn,Fe and Ni lead to precipitation of Laves phase,however,the kinetics did not improve further because of their own excellent hydrogen absorption.With increasing the content of Laves phase,there appear more pathways for hydrogen desorption so that the hydrides are more easily dissociated,which may provide new insights into how to achieve hydrogen desorption in BCC HEAs at room temperature.
基金funded by the Plant Biosecurity Cooperative Research Center (Department of Industry and Science, Australian Government. Grant No. 63058)。
文摘Water-solid interactions play a key role in determining the efficacy of inert dusts. The critical water activity(Awc) for phase transition in amorphous materials is an important characteristic of amorphous inert dusts used as grain protectants. As water activity(Aw) rises above Awc, amorphous dusts undergo a transition from glassy or vitreous state to rubbery state. Such a transition induces dramatic changes in material properties, texture and structure, and hence impact their performance as grain protectants. Full Dynamic Dewpoint Isotherms(DDI) of a synthetic amorphous zeolite intended for grain protection were generated using the Vapor Sorption Analyzer(VSA) to determine Awcby investigating the relationship between moisture content and Awat constant temperatures. Sorption experimental data was fitted using three sorption isotherm models: Guggenheim-Anderson-de Boer(GAB), Double Log Polynomial(DLP),and Brunauer-Emmet-Teller(BET). DLP model was the best model to estimate zeolite and wheat sorption isotherms. Full sorption isotherms of zeolite and wheat obtained at 25, 35, and 45 °C clearly showed the hysteresis phenomenon. The hysteresis loops were of type H3 for wheat, and of type H4 for zeolite powder. The intensity of hysteresis remained unchanged for wheat. However, the intensity of hysteresis decreased with increasing temperatures during water adsorption by porous zeolite powder. Monolayer moisture content values for each sorption direction were provided only by GAB and BET models and indicated a decrease in monolayer moisture content with an increase in temperature. The net isosteric heats of sorption and the differential enthalpy of zeolite estimated by the Clausius–Clapeyron equation and determined graphically decreased with increasing moisture content. Conversely, differential entropy of zeolite decreased with increasing zeolite moisture content. The optimal moisture content of inert dust for grain treatment was dependent on wheat moisture content and wheat storage temperature. This is the first time that a synthetic amorphous dust is being investigated for grain protection.Our results recommend the application of inert dusts at the optimal moisture content to mitigate moisture migration within the system "wheat-dust", thus ensuring dust maximal efficacy.
文摘Titration of pesticides onto sorption sites can determine sorption capacities on soils. Previous studies have tracked the sorption capacities and detailed kinetics of the uptake of atrazine and its decomposition byproduct hydroxyatrazine on different soils, including measurements made using LC-MS/MS. These studies have now been extended to explore sorption-desorption equilibria for a mixture of pesticides from soil using LC-MS/MS. Desorption of sorbed pesticide residues has environmental regulatory implications for pesticide levels in runoff, or for longer term sequestration, partitioning, and transport. The uptake of pesticides by the soil at equilibrium was measured for a number of different concentrations, and sorption capacities were estimated. Pesticide-soil interaction studies were conducted by exposing standard stock solutions of pesticide mixtures to a characterized Nova Scotia soil. The mixture contained atrazine and dicamba. Initial aqueous mixture concentrations ranging from 5 × 10<sup>-9</sup> to 10<sup>-5</sup> M or greater were exposed to 25 mg aliquots of soil and allowed to reach equilibrium. The total uptake of each pesticide was measured indirectly, by measuring the concentration remaining in solution using an IONICS 3Q 120 triple quadrupole mass spectrometer. These sorption capacities have been supplemented by studies examining equilibrium recovery rates from soil aliquots with different initial uptakes. This gives insight into the fraction of easily recoverable (reversibly sorbed) pesticides on the soil. Proper quantification of equilibrium constants and kinetic rate coefficients using high performance LC-MS/MS facilitates the construction of accurate, predictive models. Predictive kinetic models can successfully mimic the experimental results for solution concentration, labile sorption, and intra-particle diffusion, and could be used to guide regulatory practices.
