Since the discovery of carbon dots(CDs)in 2004,the unique photoluminescence phenomenon of CDs has attracted widespread attention.However,the molecular weight of CDs has not been adequately quantified at present,due to...Since the discovery of carbon dots(CDs)in 2004,the unique photoluminescence phenomenon of CDs has attracted widespread attention.However,the molecular weight of CDs has not been adequately quantified at present,due to CDs are atomically imprecise and their molecular weight distribution is broad.In this paper,a series of Pluronic-modified CDs were prepared and the structure of the CDs was briefly analyzed.Subsequently,a molecular weight measurement method based on colligative properties was developed,and the correction coefficient in the algorithm was briefly analyzed.The calculated molecular weight was applied to the determination of surface adsorption capacity.This work provided a method for averaging the molecular weight of atomically imprecise particulate materials,which is expected to provide new opportunities in related fields.展开更多
Organic matter(OM)is the primary gas occurrence carrier in shale reservoirs due to their abundant nanopores.To reveal the OM pore structure,adsorption capacity and evolution during thermal maturation,this study collec...Organic matter(OM)is the primary gas occurrence carrier in shale reservoirs due to their abundant nanopores.To reveal the OM pore structure,adsorption capacity and evolution during thermal maturation,this study collected data from samples spanning the entire evolution stage,from immature to over-mature.Scanning Electron Microscope(SEM)observation and low temperature gases adsorption experiments were used to qualitatively-semi-quantitatively and quantitatively analyze OM pore structure evolution,and CH_(4) isothermal adsorption experiments were used to reveal the adsorption capacity evolution.Then,the influence and mechanism of matu rity and hydrocarbon generation on pore development and adsorption capacity were quantitatively reviewed based on the experimental data.The results show that OM pores are poorly developed in the immature stage due to weak hydrocarbon generation,although micro-fractures are occasionally found at the edges of OM particles.In the low maturity stage,OM pores are partially developed due to liquid hydrocarbon generation,with liquid hydrocarbons also filling some OM pores.The contribution of total organic carbon content(TOC)to adsorption extent is not significant in these two stages.From high to high-over maturity stages,massive gaseous hydrocarbons are generated,significantly improving the surface porosity of OM.Clear positive linear correlations are observed between TOC and adsorption amount.However,the development of OM pores significantly declines when thermal maturity(R_(o))exceeds 3.5%due to excessive aromatization.The accuracy of research on the evolution of pore structure and adsorption capacity is limited by several factors:(ⅰ)errors caused by sample specification,calculation processes,parameter settings,and kerogen models in isothermal adsorption experiments and molecular simulations;(ⅱ)difficulty in achieving control variables due to the strong heterogeneity of natural maturation shale samples;and(ⅲ)the need to enhance compatibility between thermal simulation experiments and natural thermal evolution.Therefore,isothermal adsorption experiments on bulk shale and molecular simulations of intact shale model are necessary,taking into account the dynamic temperature and pressure of in-situ reservoirs.Moreover,shale samples with varying maturity,influenced by their distance from the paleo-thermal source,may provide significant verification for thermal simulation experiments.展开更多
Due to the existence of water content in shale reservoir,it is quite meaningful to clarify the effect of water content on the methane adsorption capacity(MAC)of shale.However,the role of spatial configuration relation...Due to the existence of water content in shale reservoir,it is quite meaningful to clarify the effect of water content on the methane adsorption capacity(MAC)of shale.However,the role of spatial configuration relationship between organic matter(OM)and clay minerals in the MAC reduction process is still unclear.The Silurian Longmaxi Formation shale samples from the Southern Sichuan Basin in China were prepared at five relative humidity(RH)conditions(0%,16%,41%,76%,99%)and the methane adsorption experiments were conducted on these water-bearing shale samples to clarify the MAC reduction process considering the spatial configuration relationship between clay minerals and OM and establish the empirical model to fit the stages.Total organic carbon(TOC)content and mineral compositions were analyzed and the pore structures of these shale samples were characterized by field-emission scanning electron microscopy(FE-SEM),N2 adsorption and high-pressure mercury intrusion porosimetry(HPMIP).The results showed that the MAC reduction of clay minerals in OM occurred at different RH conditions from that of clay minerals outside OM.Furthermore,the amount of MAC reduction of shale samples prepared at the same RH condition was negatively related with clay content,which indicated the protection role of clay minerals for the MAC of water-bearing shale samples.The MAC reduction process was generally divided into three stages for siliceous and clayey shale samples.And the MAC of OM started to decline during stage(1)for calcareous shale sample mainly because water could enter OM pores more smoothly through hydrophobic pathway provided by carbonate minerals than through hydrophilic clay mineral pores.Overall,this study will contribute to improving the evaluation method of shale gas reserve.展开更多
The variations of strain and permeability of coal were systematically studied through the physical simulation of N2 and water injection.The effects of fluid adsorption capacity and initial permeability on strain,perme...The variations of strain and permeability of coal were systematically studied through the physical simulation of N2 and water injection.The effects of fluid adsorption capacity and initial permeability on strain,permeability and the dominant effect of pore pressure were discussed.The adsorption strain and strain rate of coal during water injection are significantly higher than those during N2 injection.An edge of free adsorption exists in the early phase of N2 and water injection,which is related to fluid saturation.Within this boundary,the strain rate and pore pressure are independent.Moreover,the injec-tion time of initial stage accounts for about 20%of the total injection time,but the strain accounts for 70%of the total strain.For water injection,this boundary is about half of water saturation of coal.Besides,the influence of pore pressure on permeability is complex,which is controlled by adsorption capacity and initial permeability of coal.When the initial permeability is large enough,the effect of adsorption strain on permeability is relatively weak,and the promoting effect of pore pressure on fluid migration is dominant.Therefore,the permeability increases with increasing pore pressure.When the initial permeability is relatively low,the pore pressure may have a dominant role in promoting fluid migration for the fluid with weak adsorption capacity.However,for the fluid with strong adsorption capacity,the adsorption strain caused by pore pressure may play a leading role,and the permeability reduces first and then ascends with increasing pore pressure.展开更多
Coal fly ash （CFA） generated by coal-based thermal power plants is mainly composed of some oxides having high crystallinity, including quartz and mullite. In this study, the effect of CFA crystallinity toward its ca...Coal fly ash （CFA） generated by coal-based thermal power plants is mainly composed of some oxides having high crystallinity, including quartz and mullite. In this study, the effect of CFA crystallinity toward its capacity on Pb（Ⅱ） adsorption was investigated. CFA with various crystaUinity was obtanied by refluxing it with sodium hydroxide （NaOH） solution having various concentrations （1-7 M） at various temperature and reflux time. To evaluate the effect of crystallinity of treated CFA on the adsorption capacity, adsorption of Pb（Ⅱ） solution with treated CFA was carried out. The research shows that the reflux of CFA with NaOH solution leads to the crystallinity of quartz and mullite in CFA decreased. The decrease is proportional with the concentration increasing, the temperature elevation, and the longer time. The reflux using NaOH solution with high concentration （〉 3 M） in addition causes a decrease in the crystallinity of quartz and mullite, also results in the formation of hydroxysodalite. The decrease of the CFA crystalllinity gives an increase in CFA adsorption capacity toward Pb（Ⅱ） solution.展开更多
The static adsorption performances of a series of active carbon fiber(ACF)for xenon at 201 K were measured with a model ASAP2010M specific surface area and aperture distribution instrument by changing the working gas ...The static adsorption performances of a series of active carbon fiber(ACF)for xenon at 201 K were measured with a model ASAP2010M specific surface area and aperture distribution instrument by changing the working gas of instrument from N 2 to Xenon. Compared with grain active carbon(GAC): (1) the adsorption performance of Viscose based ACF(VACF) adsorbents is better than that of GAC; (2) owing to the difference of aperture distribution, the adsorption performance of ACF with different radicales is different under the same experiment conditions though the specific surface area is similar; (3) there is no definite relationship between adsorption performance and specific surface area; (4) the VACF A2 is the superior xenon adsorbent at the experimental temperature.展开更多
Residue biochar can be utilized as an adsorbent for ammonium nitrogen(NH_(4)^(+)-N)to prevent non-point source pollution.However,the limited adsorption capacity has restricted its extensive application.In this study,b...Residue biochar can be utilized as an adsorbent for ammonium nitrogen(NH_(4)^(+)-N)to prevent non-point source pollution.However,the limited adsorption capacity has restricted its extensive application.In this study,biochar was modified with hydrogen peroxide(H_(2)O_(2)),potassium permanganate(KMnO_(4)),and sodium hydroxide(NaOH)to enhance its adsorption performance.A comparative analysis of the biochar surface characteristics was used to investigate the adsorption systems.The results indicated that the adsorption capacities of the modified biochar(MB)were significantly enhanced compared with the raw biochar(RB).At the highest NH_(4)^(+)-N concentration of 150 mg L^(−1),the adsorption capacities of RB-H_(2)O_(2),RB-NaOH,and RB-KMnO_(4)increased to 3.0,3.2,and 4.0 times that of RB,respectively.As predicted by the Langmuir isotherm model,the maximum adsorption capacities of these three MB were 13.93,41.00,and 68.15 mg g^(−1),respectively.Ammonium adsorption on the MB surfaces was affected by surface adsorption,liquid membrane diffusion,and intra-particle diffusion.The specific surface area and pore volume of RBKMnO_(4)were significantly enhanced,with an increase in active sites on the pore surfaces,thereby strengthening its adsorption capacity for NH_(4)^(+)-N.In contrast,the adsorption of NH_(4)^(+)-N by RB-H_(2)O_(2)and RB-NaOH primarily relied on the substantial increase in-C-O functional groups,with additional contributions from other oxygen-containing functional(e.g.-OH,-COOH,and Fe-O).In conclusion,RB-KMnO_(4)exhibited the highest adsorption efficiency,with pore-based adsorption playing a dominant role over functional group-based adsorption.These findings highlight the critical role of pore structure optimization in enhancing the biochar adsorption capacity for NH_(4)^(+)-N.展开更多
A novel adsorbent was prepared by modifying orange peel with sodium hydroxide and calcium chloride. The morphological and characteristics of the adsorbent were evaluated by infrared spectroscopy （IR）, scanning elect...A novel adsorbent was prepared by modifying orange peel with sodium hydroxide and calcium chloride. The morphological and characteristics of the adsorbent were evaluated by infrared spectroscopy （IR）, scanning electron microscopy （SEM） and N2-adsorption techniques. The adsorption behavior of Cu^2＋, Pb^2＋ and Zn^2＋ on modified orange peel （SCOP） was studied by varying parameters like pH, initial concentration of metal ions. Equilibrium was well described by Langmuir equation with the maximum adsorption capacities for Cu^2＋, Pb^2＋ and Zn^2＋ of 70.73, 209.8 and 56.18 mg/g, respectively. Based on the results obtained in batch experiments, breakthrough profiles were examined using a column packed with SCOP for the separation of small concentration of Pb^2＋ from an excess of Zn^2＋ followed by elution tests. Ion exchange with Ca^2＋ neutralizing the carboxyl groups of the pectin was found to be the predominant mechanism.展开更多
CCUS (carbon capture, utilization, and storage) technology is regarded as a bottom method to achieve carbon neutrality globally. CO_(2) storage in deep coal reservoirs serves as a feasible selection for CCUS, and its ...CCUS (carbon capture, utilization, and storage) technology is regarded as a bottom method to achieve carbon neutrality globally. CO_(2) storage in deep coal reservoirs serves as a feasible selection for CCUS, and its storage potential can be attributed to the CO_(2) adsorption capacity of the coal. In this paper, a series of CO_(2) adsorption isotherm experiments were performed at different pressures and temperatures in sub-bituminous coal from the southern Junggar Basin (reservoir temperature ∼25.9°C and pressure ∼3.91 MPa). In addition, the high-pressure CO_(2) adsorption characteristics of the southern Junggar Basin coal were characterized using a supercritical D-R adsorption model. Finally, the CO_(2) storage capacities in sub-bituminous coal under the in situ reservoir temperature and pressure were analyzed. Results indicated that the excess adsorption capacities increase gradually with increasing injection pressure before reaching an asymptotic maximum magnitude of ∼34.55 cm3/g. The supercritical D-R adsorption model is suitable for characterizing the excess/absolute CO_(2) adsorption capacity, as shown by the high correlation coefficients > 0.99. The CO_(2) adsorption capacity increases with declining temperature, indicating a negative effect of temperature on CO_(2) geological sequestration. By analyzing the statistical relationships of the D-R adsorption fitting parameters with the reservoir temperature, a CO_(2) adsorption capacity evolution model was established, which can be further used for predicting CO_(2) sequestration potential at in situ reservoir conditions. CO_(2) adsorption capacity slowly increases before reaching the critical CO_(2) density, following a rapid decrease at depths greater than ∼800 m in the southern Junngar Basin. The research results presented in this paper can provide guidance for evaluating CO_(2) storage potential in deep coal seams.展开更多
Determination of gas adsorption capacity under geological conditions is essential in evaluating shale gas resource potential.A quantitative determination of gas adsorption capacity was proposed through 1)investigating...Determination of gas adsorption capacity under geological conditions is essential in evaluating shale gas resource potential.A quantitative determination of gas adsorption capacity was proposed through 1)investigating controlling geological factors(including both internal ones and external ones)of gas adsorption capacity in organic-rich marine shale with geochemical analysis,XRD diffraction,field-emission scanning electron microscopy,and methane sorption isotherms;2)defining the relationship between gas adsorption capacity and single controlling factor;3)establishing a comprehensive determination model with the consideration of all these controlling factors.The primary controlling factors of the sorption capacity for the studied O3wLower S1l shale are TOC,illite and quartz,temperature,pressure,Ro,and moisture(water saturation).Specifically,TOC,thermal maturity,illite,and pressure are positively correlated with sorption capacity,whereas,quartz and temperature contribute negatively to the sorption capacity.We present the quantitative model along with application examples from the Wufeng-Lower Longmaxi Shale in the southeast Sichuan Basin,west China,to demonstrate the approach in shale gas evaluation.The result shows that the comprehensive determination model provides a good and unbiased estimate of gas adsorption capacities with a high correlation coefficient(0.96)and bell-shaped residues centered at zero.展开更多
The purpose of this research work is to determine the removal efficiency of Cu^(2+)and Pb^(2+)ions using polyvinyl alcohol/neem leaf extract/chitosan(PVA/NLE/CS)composite films as adsorbent materials from an aqueous m...The purpose of this research work is to determine the removal efficiency of Cu^(2+)and Pb^(2+)ions using polyvinyl alcohol/neem leaf extract/chitosan(PVA/NLE/CS)composite films as adsorbent materials from an aqueous medium,with respect to pH,contact time,and adsorbent dosage.The synthesized composite material was characterized using Fourier Transform Infrared(FTIR)spectroscopy,thermogravimetric analysis-Derivative Thermogravimetry(TGA-DTG),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),and scanning electron microscopy-Energy Dispersive X-ray Spectroscopy(SEM-EDX).The antibacterial activity and swelling response of the material were studied using suitable methodologies.The FTIR study confirmed the interactions among PVA,chitosan,and neem leaf extract.The TGA data reveal the excellent thermal stability of the developed composite films.The SEM micrograph indicates a homogeneous phase morphology with good compatibility among chitosan,the monomer,and the leaf extract.The antibacterial study revealed that the prepared PVA/NLE/CS films exhibit improved antibacterial activity against bacterial growth.It was found that at pH 6.0,the adsorption capacity for both toxic metal ions is maximum,and decreases with a further rise in pH.At this pH,the adsorption capacity of PVA/NLE/CS films increases with a gradual increase in adsorbent dosage,and at a specific pH,the adsorption capacity for Cu^(2+)is greater than that for Pb^(2+).The adsorption efficiency is a function of contact time and was found to be maximal at 180 min.Hence,the developed composite material is effective for the removal of metal ions from wastewater.展开更多
In order to improve the calculation method of the isosteric adsorption heat,clarify thermodynamic characteristics of CH4 adsorption by continental shale and reveal the adsorption mechanism,this paper selected shale sa...In order to improve the calculation method of the isosteric adsorption heat,clarify thermodynamic characteristics of CH4 adsorption by continental shale and reveal the adsorption mechanism,this paper selected shale samples from the seventh Member of Yanchang Formation of Upper Triassic in the Yanchang Gasfield of the Ordos Basin as the research object.The isothermal adsorption experiment was carried out on the CH4 adsorption by continental shale and the excess adsorption curves were plotted.Then,the characteristics of the isosteric adsorption heat of the shale with different types of adsorption capacity were illustrated by analyzing and comparing the difference between excess and absolute adsorption capacity.And the following research results were obtained.First,under the same temperature and pressure,absolute adsorption capacity is higher than the excess values.The difference between them is higher under low temperature and high pressure and it is in the relationship of exponential function with the equilibrium pressure.If excess adsorption capacity is used to evaluate the adsorptive property of shale reservoirs,the evaluation result will be underestimated.Second,for CH4 adsorption by Yanchang Formation shale,the absolute and excess isosteric adsorption heat values have a linear positive correlation with absolute and excess adsorption capacity respectively,and the intermo-lecular force of adsorbate has a dominant effect on isosteric adsorption heat values.Third,absolute isosteric adsorption heat value is less than the excess heat.The relative error is in the range of 18.18e49.79%,and it is higher in the stage with low adsorption capacity.If excess adsorption capacity is taken as the basic data to calculate initial isosteric adsorption heat values,the calculation result will be overvalued,and consequently,the evaluation of the intermolecular force of adsorbent and adsorbate is overestimated.展开更多
Constructed wetlands （CWs） are engineered systems that utilize natural systems including wetland vegetations, soils, and their associated microbial assemblages to assist in treating wastewater. The kinetic adsorptio...Constructed wetlands （CWs） are engineered systems that utilize natural systems including wetland vegetations, soils, and their associated microbial assemblages to assist in treating wastewater. The kinetic adsorption of ammonium nitrogen （NH＋-N） by CW substrate materials such as blast furnace slag （BFS）, zeolite, ceramsite, vermiculite, gravel, paddy soil, red soil, and turf, was investigated using batch experiments and kinetic adsorption isotherms. Both Freundlich and Lang- muir isotherms could adequately predict the NH＋-N adsorption process. The maximum adsorption capacities of NH＋-N, estimated from the Langmuir isotherm, ranked as： zeolite （33 333.33 mg kg^-1） 〉 turf （29274.01 mg kg^-1） 〉 BFS （5000 mg kg^-1） 〉 vermiculite （3333.33 mg kg^-1） 〉 gravel （769.23 mg kg^-1） 〉 paddy soil （588.24 mg kg^-1） 〉 red soil （555.56 mg kg^-1） 〉 ceramsite （107.53 mg kg^-1）. Some properties of the substrate materials, including bulk density, specific gravity, hydraulic conductivity, uniformity coefficient （K60）, curvature coefficient （Co）, organic matter, pH, exchangeable （or active） Cu, Fe, Zn and Mn, total Cu, and Fe, Mn, Zn, Cd, Pb and Ca, had negative correlations with NH＋-N adsorption. Other properties of the substrate materials like particle diameter values of D10, 030 and 060 （the diameters of particle sizes of a substrate material at which 10%, 30% and 60%, respectively, of the particles pass through the sieve based on the accumulative frequency）, cation exchange capacity （CEC）, exchangeable （or active） Ca and Mg, and total K and Mg had positive correlations with NH＋-N adsorption. In addition, active K and Na as well as the total Na had significant positive correlations with NH＋-N adsorption. This information would be useful for selection of suitable substrate materials for CWs.展开更多
In this paper, the methane adsorption behaviours in slit-like chlorite nanopores were investigated using the grand canonical Monte Carlo simulation method, and the influences of the pore sizes, temperatures, water, an...In this paper, the methane adsorption behaviours in slit-like chlorite nanopores were investigated using the grand canonical Monte Carlo simulation method, and the influences of the pore sizes, temperatures, water, and compositions on methane adsorption on chlorite were discussed. Our investigation revealed that the isosteric heat of adsorption of methane in slit-like chlorite nanopores decreased with an increase in pore size and was less than 42 kJ/mol, suggesting that methane adsorbed on chlorite through physical adsorption. The methane excess adsorp- tion capacity increased with the increase in the pore size in micropores and decreased with the increase in the pore size in mesopores. The methane excess adsorption capacity in chlorite pores increased with an increase in pressure or decrease in pore size. With an increase in temperature, the isosteric heats of adsorption of methane decreased and the methane adsorption sites on chlorite changed from lower- energy adsorption sites to higher-energy sites, leading to the reduction in the methane excess adsorption capacity. Water molecules in chlorite pores occupied the pore wall in a directional manner, which may be related to the van der Waals and Coulomb force interactions and the hydrogen bonding interaction. It was also found that water molecules existed as aggregates. With increasing water content, the water molecules occupied the adsorption sites and adsorption space of the methane, leading to a reduction in the methane excess adsorption capacity. The excess adsorption capacity of gas on chlorite decreased in the following order： carbon dioxide 〉 methane 〉 nitrogen. If the mole fraction of nitrogen or carbon dioxide in the binary gas mixture increased, the mole fraction of methane decreased, methane adsorption sites changed, and methane adsorption space was reduced, resulting in the decrease in the methane excess adsorption capacity.展开更多
A semi-empirical adsorption kinetic model was proposed with the time compensation method to describe the chemisorption of SO2 in flue gas by carbon adsorbents for flue gas purification.The change in adsorption capacit...A semi-empirical adsorption kinetic model was proposed with the time compensation method to describe the chemisorption of SO2 in flue gas by carbon adsorbents for flue gas purification.The change in adsorption capacity and adsorption rate with time at different water vapor concentrations and different SO2 concentrations was studied.The model was in good agreement with experimental data.The surface reaction was probably the rate controlling step in the early stage for SO2 adsorption by ZL50 activated carbon.The parameters m and n in the nth order adsorption kinetic model were related to the magnitude of the time compensation and adsorption driving force,respectively.The change of parameter n with water vapor concentrations and sulfur dioxide concentrations was studied and some physical implications were given.The sum of square errors was less than 1.0 and the average absolute percentage deviations ranged from 0.5 to 3.2.The kinetic model was compared with other models in the literature.展开更多
Safe application of chromium （Cr）-containing organic industrial wastes to soil requires considering the ability of the soil to adsorb Cr. In this study, the maximum Cr adsorption capacity was assessed for the bulk s...Safe application of chromium （Cr）-containing organic industrial wastes to soil requires considering the ability of the soil to adsorb Cr. In this study, the maximum Cr adsorption capacity was assessed for the bulk samples and their clay and iron-free clay fractions of four subtropical soils differing in mineralogy. To this end, the samples were supplied with Cr（Ⅲ） nitrate solutions at pH 4.5 or 5.5. The results of Cr（Ⅲ） adsorption fitted to a Freundlich equation and the adsorption capacity was positively correlated with soil organic matter and iron oxide contents. The clay fractions adsorbed more Cr per unit mass than the bulk soils and the iron-free clay fractions. The Cr（Ⅲ） adsorption capacity increased with increasing soil pH due to more charges on adsorbing surfaces. Our results suggest that the soils rich in organic matter and iron oxides and having a pH above 4.5 are suitable for application of Cr（Ⅲ）-loaded industrial wastes.展开更多
Extensive use of chemical fertilizers in agriculture can induce high concentration of ammonium nitrogen(NH4^(+)_(-)N) in soil. Desorption and leaching of NH4^(+)_(-)N has led to pollution of natural waters. The adsorp...Extensive use of chemical fertilizers in agriculture can induce high concentration of ammonium nitrogen(NH4^(+)_(-)N) in soil. Desorption and leaching of NH4^(+)_(-)N has led to pollution of natural waters. The adsorption of NH4^(+)_(-)N in soil plays an important role in the fate of the NH4^(+)_(-)N. Understanding the adsorption characteristics of NH4^(+)_(-)N is necessary to ascertain and predict its fate in the soil-water environment, and pedotransfer functions(PTFs) could be a convenient method for quantification of the adsorption parameters. Ammonium nitrogen adsorption capacity, isotherms, and their influencing factors were investigated for various soils in an irrigation district of the North China Plain. Fourteen agricultural soils with three types of texture(silt, silty loam, and sandy loam) were collected from topsoil to perform batch experiments. Silt and silty loam soils had higher NH4^(+)_(-)N adsorption capacity than sandy loam soils.Clay and silt contents significantly affected the adsorption capacity of NH4^(+)_(-)N in the different soils. The adsorption isotherms of NH4^(+)_(-)N in the 14 soils fit well using the Freundlich, Langmuir, and Temkin models. The models’ adsorption parameters were significantly related to soil properties including clay,silt, and organic carbon contents and Fe^(2+) and Fe^(3+) ion concentrations in the groundwater. The PTFs that relate soil and groundwater properties to soil NH4^(+)_(-)N adsorption isotherms were derived using multiple regressions where the coefficients were predicted using the Bayesian method. The PTFs of the three adsorption isotherm models were successfully verified and could be useful tools to help predict NH4^(+)_(-)N adsorption at a regional scale in irrigation districts.展开更多
The chars in the natural environment can affect the migration of polybrominated diphenyl ethers(PBDEs). However, there is insufficient research relating to the adsorption behavior and mechanisms of PBDEs on biochars. ...The chars in the natural environment can affect the migration of polybrominated diphenyl ethers(PBDEs). However, there is insufficient research relating to the adsorption behavior and mechanisms of PBDEs on biochars. This study examined the adsorption kinetics of 2,2′,4,4′-tetrabromodiphenyl ether(BDE-47) on maize straw-derived biochars(MSBCs) pyrolyzed at four different temperatures via batch experiments. The biochar samples were characterized using Fourier transform infrared(FTIR) spectroscopy,Raman spectra, and elemental analysis. A two-compartment first-order model and pseudo-second-order model exhibited a better fit compared to a pseudo-first-order model in describing the BDE-47 adsorption on biochars, which was dominated by a slow adsorption compartment and chemisorption. The MSBC pyrolyzed at 600 °C had the highest BDE-47 adsorption capacity owing to its relatively large specific surface area and relatively high aromaticity compared with the other three MSBCs pyrolyzed at 300, 400, and 500 ℃.However, there was no significant difference in adsorption capacity among the other three biochars. The organic functional groups coupled with the graphene structures of biochars and the hydrophobic effect of the functional groups promoted the adsorption of BDE-47. Pore diffusion was not the sole rate-limiting step;film diffusion was also involved in the adsorption process of BDE-47 on biochars. The overall results demonstrate the transport and potential treatment of PBDEs using biochars.展开更多
The adsorption capacity of landfill liners containing granular activated carbon (GAC), or bentonite activated by acid, for Cr(VI) was investigated by batch testing. The results show that both GAC and activated bentoni...The adsorption capacity of landfill liners containing granular activated carbon (GAC), or bentonite activated by acid, for Cr(VI) was investigated by batch testing. The results show that both GAC and activated bentonite could be used as sorptive amendments for trapping Cr(VI) in landfill liners. The Cr(VI) sorption to GAC and activated bentonite is much greater than Cr(VI) sorption to natural clay. The adsorption capacity of Cr(VI) onto all the soils increases with increasing temperature; adsorption capacity is also significantly influenced by soil-solid concentration. As the soil-solid concentration increases the adsorption capacity first decreases logarithmically, but then stabilizes when the soil-solid concentration exceeds a critical value (e.g. 400 g/L). Permeability tests were conducted in the laboratory. The results indicate that the hydraulic conductivity of landfill liners containing GAC or activated bentonite can meet the engineering requirement of 1 nm/s. One-dimensional transport simulations for Cr(VI) were performed to evaluate the effect of GAC and activated bentonite on landfill liners. The results of the simulations indicate that landfill liners containing GAC, or activated bentonite, significantly retard the transport of Cr(VI) relative to a conventional clay liner.展开更多
The adsorption capacities of new humic acids isolated from Yakouren forest （YHA） and Sahara （Tamenrasset： THA） soils （Algeria） and commercial humic acid （PFHA） on polyaniline emeraldine base （PEB） were stud...The adsorption capacities of new humic acids isolated from Yakouren forest （YHA） and Sahara （Tamenrasset： THA） soils （Algeria） and commercial humic acid （PFHA） on polyaniline emeraldine base （PEB） were studied at pH 6.6. Also the adsorption of heavy metals such as Cd 2＋ , Zn 2＋ and Ni 2＋ on humic acid-polyaniline systems （HA-PEB） was investigated at the same conditions. HA-PEB compounds were characterized by scanning electron microscopy （SEM）, infrared spectrometry and cavity microelectrode. In addition, batch adsorption and cavity microelectrode were used in the adsorption study of Cd 2＋ , Zn 2＋ and Ni 2＋ on HA-PEB. To develop biocaptors of polluting metals using a cavity microelectrode modified by HA-PEB systems, the adsorption kinetic and adsorption capacity were investigated. The SEM analysis showed that the presence of humic acid affected the PEB surface and caused the formation of a granular morphology. The maximum adsorption capacities （q max ） of PFHA, THA and YHA determined by adsorption isotherms were 91.31, 132.1 and 151.0 mg/g, respectively. Batch adsorption results showed that q max of Cd 2＋ , Zn 2＋ and Ni 2＋ on HA-PEB followed the order： THA-PEB YHA-PEB PFHA-PEB. The voltammograms obtained with HA-PEB modified cavity microelectrode showed the appearance of new redox couples reflecting the adsorption of HA on PEB. Metal-humic acid-polyaniline voltammograms were characterized by appearance of oxidation-reduction couples or reduction wave corresponding to metal. Finally, the result may be exploited to develop a biocaptor based on the cavity microelectrode amended by THA-PEB and YHA-PEB.展开更多
文摘Since the discovery of carbon dots(CDs)in 2004,the unique photoluminescence phenomenon of CDs has attracted widespread attention.However,the molecular weight of CDs has not been adequately quantified at present,due to CDs are atomically imprecise and their molecular weight distribution is broad.In this paper,a series of Pluronic-modified CDs were prepared and the structure of the CDs was briefly analyzed.Subsequently,a molecular weight measurement method based on colligative properties was developed,and the correction coefficient in the algorithm was briefly analyzed.The calculated molecular weight was applied to the determination of surface adsorption capacity.This work provided a method for averaging the molecular weight of atomically imprecise particulate materials,which is expected to provide new opportunities in related fields.
基金the supports of the Na-tional Natural Science Foundation of China(No.U19B2007,42072202)the China Postdoctoral Science Foundation(No.2025MD774057)。
文摘Organic matter(OM)is the primary gas occurrence carrier in shale reservoirs due to their abundant nanopores.To reveal the OM pore structure,adsorption capacity and evolution during thermal maturation,this study collected data from samples spanning the entire evolution stage,from immature to over-mature.Scanning Electron Microscope(SEM)observation and low temperature gases adsorption experiments were used to qualitatively-semi-quantitatively and quantitatively analyze OM pore structure evolution,and CH_(4) isothermal adsorption experiments were used to reveal the adsorption capacity evolution.Then,the influence and mechanism of matu rity and hydrocarbon generation on pore development and adsorption capacity were quantitatively reviewed based on the experimental data.The results show that OM pores are poorly developed in the immature stage due to weak hydrocarbon generation,although micro-fractures are occasionally found at the edges of OM particles.In the low maturity stage,OM pores are partially developed due to liquid hydrocarbon generation,with liquid hydrocarbons also filling some OM pores.The contribution of total organic carbon content(TOC)to adsorption extent is not significant in these two stages.From high to high-over maturity stages,massive gaseous hydrocarbons are generated,significantly improving the surface porosity of OM.Clear positive linear correlations are observed between TOC and adsorption amount.However,the development of OM pores significantly declines when thermal maturity(R_(o))exceeds 3.5%due to excessive aromatization.The accuracy of research on the evolution of pore structure and adsorption capacity is limited by several factors:(ⅰ)errors caused by sample specification,calculation processes,parameter settings,and kerogen models in isothermal adsorption experiments and molecular simulations;(ⅱ)difficulty in achieving control variables due to the strong heterogeneity of natural maturation shale samples;and(ⅲ)the need to enhance compatibility between thermal simulation experiments and natural thermal evolution.Therefore,isothermal adsorption experiments on bulk shale and molecular simulations of intact shale model are necessary,taking into account the dynamic temperature and pressure of in-situ reservoirs.Moreover,shale samples with varying maturity,influenced by their distance from the paleo-thermal source,may provide significant verification for thermal simulation experiments.
基金supported by the National Science and Technology Major Project of China(No.2017ZX05035-002)the National Natural Science Foundation of China(No.41972145)the Foundation of State Key Laboratory of Petroleum Resources and Prospecting from China University of Petroleum in Beijing(Nos.PRP/indep-3-1707,PRP/indep-3-1615)。
文摘Due to the existence of water content in shale reservoir,it is quite meaningful to clarify the effect of water content on the methane adsorption capacity(MAC)of shale.However,the role of spatial configuration relationship between organic matter(OM)and clay minerals in the MAC reduction process is still unclear.The Silurian Longmaxi Formation shale samples from the Southern Sichuan Basin in China were prepared at five relative humidity(RH)conditions(0%,16%,41%,76%,99%)and the methane adsorption experiments were conducted on these water-bearing shale samples to clarify the MAC reduction process considering the spatial configuration relationship between clay minerals and OM and establish the empirical model to fit the stages.Total organic carbon(TOC)content and mineral compositions were analyzed and the pore structures of these shale samples were characterized by field-emission scanning electron microscopy(FE-SEM),N2 adsorption and high-pressure mercury intrusion porosimetry(HPMIP).The results showed that the MAC reduction of clay minerals in OM occurred at different RH conditions from that of clay minerals outside OM.Furthermore,the amount of MAC reduction of shale samples prepared at the same RH condition was negatively related with clay content,which indicated the protection role of clay minerals for the MAC of water-bearing shale samples.The MAC reduction process was generally divided into three stages for siliceous and clayey shale samples.And the MAC of OM started to decline during stage(1)for calcareous shale sample mainly because water could enter OM pores more smoothly through hydrophobic pathway provided by carbonate minerals than through hydrophilic clay mineral pores.Overall,this study will contribute to improving the evaluation method of shale gas reserve.
基金supported by the National Natural Science Foundation of China(41872170,42072189)China Postdoctoral Science Foundation(2021M690916)+3 种基金Key Science and Technology Program of Henan Province(222102320154)State Key Laboratory Cultivation Base for Gas Geology and Gas Control(Henan Polytechnic University)(WS2020B10)Key Scientific Research Projects of Colleges and Universities in Henan Province(21A440006)Doctor foundation of Henan Polytechnic University(B2020-6,B2021-5).
文摘The variations of strain and permeability of coal were systematically studied through the physical simulation of N2 and water injection.The effects of fluid adsorption capacity and initial permeability on strain,permeability and the dominant effect of pore pressure were discussed.The adsorption strain and strain rate of coal during water injection are significantly higher than those during N2 injection.An edge of free adsorption exists in the early phase of N2 and water injection,which is related to fluid saturation.Within this boundary,the strain rate and pore pressure are independent.Moreover,the injec-tion time of initial stage accounts for about 20%of the total injection time,but the strain accounts for 70%of the total strain.For water injection,this boundary is about half of water saturation of coal.Besides,the influence of pore pressure on permeability is complex,which is controlled by adsorption capacity and initial permeability of coal.When the initial permeability is large enough,the effect of adsorption strain on permeability is relatively weak,and the promoting effect of pore pressure on fluid migration is dominant.Therefore,the permeability increases with increasing pore pressure.When the initial permeability is relatively low,the pore pressure may have a dominant role in promoting fluid migration for the fluid with weak adsorption capacity.However,for the fluid with strong adsorption capacity,the adsorption strain caused by pore pressure may play a leading role,and the permeability reduces first and then ascends with increasing pore pressure.
文摘Coal fly ash （CFA） generated by coal-based thermal power plants is mainly composed of some oxides having high crystallinity, including quartz and mullite. In this study, the effect of CFA crystallinity toward its capacity on Pb（Ⅱ） adsorption was investigated. CFA with various crystaUinity was obtanied by refluxing it with sodium hydroxide （NaOH） solution having various concentrations （1-7 M） at various temperature and reflux time. To evaluate the effect of crystallinity of treated CFA on the adsorption capacity, adsorption of Pb（Ⅱ） solution with treated CFA was carried out. The research shows that the reflux of CFA with NaOH solution leads to the crystallinity of quartz and mullite in CFA decreased. The decrease is proportional with the concentration increasing, the temperature elevation, and the longer time. The reflux using NaOH solution with high concentration （〉 3 M） in addition causes a decrease in the crystallinity of quartz and mullite, also results in the formation of hydroxysodalite. The decrease of the CFA crystalllinity gives an increase in CFA adsorption capacity toward Pb（Ⅱ） solution.
文摘The static adsorption performances of a series of active carbon fiber(ACF)for xenon at 201 K were measured with a model ASAP2010M specific surface area and aperture distribution instrument by changing the working gas of instrument from N 2 to Xenon. Compared with grain active carbon(GAC): (1) the adsorption performance of Viscose based ACF(VACF) adsorbents is better than that of GAC; (2) owing to the difference of aperture distribution, the adsorption performance of ACF with different radicales is different under the same experiment conditions though the specific surface area is similar; (3) there is no definite relationship between adsorption performance and specific surface area; (4) the VACF A2 is the superior xenon adsorbent at the experimental temperature.
基金supported by the National Natural Science Foundation of China(3230196931901195)+2 种基金Shandong Provincial Natural Science Foundation(ZR2024MC159)the Agricultural Science and Technology Innovation Program of the Chinese Academy of Agricultural Sciences(ASTIP-TRIC03)Yunnan Branch of China National Tobacco Corporation(2024530000241031).
文摘Residue biochar can be utilized as an adsorbent for ammonium nitrogen(NH_(4)^(+)-N)to prevent non-point source pollution.However,the limited adsorption capacity has restricted its extensive application.In this study,biochar was modified with hydrogen peroxide(H_(2)O_(2)),potassium permanganate(KMnO_(4)),and sodium hydroxide(NaOH)to enhance its adsorption performance.A comparative analysis of the biochar surface characteristics was used to investigate the adsorption systems.The results indicated that the adsorption capacities of the modified biochar(MB)were significantly enhanced compared with the raw biochar(RB).At the highest NH_(4)^(+)-N concentration of 150 mg L^(−1),the adsorption capacities of RB-H_(2)O_(2),RB-NaOH,and RB-KMnO_(4)increased to 3.0,3.2,and 4.0 times that of RB,respectively.As predicted by the Langmuir isotherm model,the maximum adsorption capacities of these three MB were 13.93,41.00,and 68.15 mg g^(−1),respectively.Ammonium adsorption on the MB surfaces was affected by surface adsorption,liquid membrane diffusion,and intra-particle diffusion.The specific surface area and pore volume of RBKMnO_(4)were significantly enhanced,with an increase in active sites on the pore surfaces,thereby strengthening its adsorption capacity for NH_(4)^(+)-N.In contrast,the adsorption of NH_(4)^(+)-N by RB-H_(2)O_(2)and RB-NaOH primarily relied on the substantial increase in-C-O functional groups,with additional contributions from other oxygen-containing functional(e.g.-OH,-COOH,and Fe-O).In conclusion,RB-KMnO_(4)exhibited the highest adsorption efficiency,with pore-based adsorption playing a dominant role over functional group-based adsorption.These findings highlight the critical role of pore structure optimization in enhancing the biochar adsorption capacity for NH_(4)^(+)-N.
基金Project (50774100) supported by the National Natural Science Foundation of China
文摘A novel adsorbent was prepared by modifying orange peel with sodium hydroxide and calcium chloride. The morphological and characteristics of the adsorbent were evaluated by infrared spectroscopy （IR）, scanning electron microscopy （SEM） and N2-adsorption techniques. The adsorption behavior of Cu^2＋, Pb^2＋ and Zn^2＋ on modified orange peel （SCOP） was studied by varying parameters like pH, initial concentration of metal ions. Equilibrium was well described by Langmuir equation with the maximum adsorption capacities for Cu^2＋, Pb^2＋ and Zn^2＋ of 70.73, 209.8 and 56.18 mg/g, respectively. Based on the results obtained in batch experiments, breakthrough profiles were examined using a column packed with SCOP for the separation of small concentration of Pb^2＋ from an excess of Zn^2＋ followed by elution tests. Ion exchange with Ca^2＋ neutralizing the carboxyl groups of the pectin was found to be the predominant mechanism.
基金the National Natural Science Foundation of China(Grant Nos.42141012,41972168,and 42030810)the Peng Cheng Shang Xue Education Fund of CUMT Education Development Foundation(No.PCSX202204)+1 种基金the Fundamental Research Funds for the Central Universities(No.2020ZDPYZD01)aa project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘CCUS (carbon capture, utilization, and storage) technology is regarded as a bottom method to achieve carbon neutrality globally. CO_(2) storage in deep coal reservoirs serves as a feasible selection for CCUS, and its storage potential can be attributed to the CO_(2) adsorption capacity of the coal. In this paper, a series of CO_(2) adsorption isotherm experiments were performed at different pressures and temperatures in sub-bituminous coal from the southern Junggar Basin (reservoir temperature ∼25.9°C and pressure ∼3.91 MPa). In addition, the high-pressure CO_(2) adsorption characteristics of the southern Junggar Basin coal were characterized using a supercritical D-R adsorption model. Finally, the CO_(2) storage capacities in sub-bituminous coal under the in situ reservoir temperature and pressure were analyzed. Results indicated that the excess adsorption capacities increase gradually with increasing injection pressure before reaching an asymptotic maximum magnitude of ∼34.55 cm3/g. The supercritical D-R adsorption model is suitable for characterizing the excess/absolute CO_(2) adsorption capacity, as shown by the high correlation coefficients > 0.99. The CO_(2) adsorption capacity increases with declining temperature, indicating a negative effect of temperature on CO_(2) geological sequestration. By analyzing the statistical relationships of the D-R adsorption fitting parameters with the reservoir temperature, a CO_(2) adsorption capacity evolution model was established, which can be further used for predicting CO_(2) sequestration potential at in situ reservoir conditions. CO_(2) adsorption capacity slowly increases before reaching the critical CO_(2) density, following a rapid decrease at depths greater than ∼800 m in the southern Junngar Basin. The research results presented in this paper can provide guidance for evaluating CO_(2) storage potential in deep coal seams.
基金supported by the National Natural Science Foundation of China(Grant No.41972160)Open fund of Key Laboratory of oil and gas resources research,Chinese Academy of Sciences(KLOR2018-7).
文摘Determination of gas adsorption capacity under geological conditions is essential in evaluating shale gas resource potential.A quantitative determination of gas adsorption capacity was proposed through 1)investigating controlling geological factors(including both internal ones and external ones)of gas adsorption capacity in organic-rich marine shale with geochemical analysis,XRD diffraction,field-emission scanning electron microscopy,and methane sorption isotherms;2)defining the relationship between gas adsorption capacity and single controlling factor;3)establishing a comprehensive determination model with the consideration of all these controlling factors.The primary controlling factors of the sorption capacity for the studied O3wLower S1l shale are TOC,illite and quartz,temperature,pressure,Ro,and moisture(water saturation).Specifically,TOC,thermal maturity,illite,and pressure are positively correlated with sorption capacity,whereas,quartz and temperature contribute negatively to the sorption capacity.We present the quantitative model along with application examples from the Wufeng-Lower Longmaxi Shale in the southeast Sichuan Basin,west China,to demonstrate the approach in shale gas evaluation.The result shows that the comprehensive determination model provides a good and unbiased estimate of gas adsorption capacities with a high correlation coefficient(0.96)and bell-shaped residues centered at zero.
文摘The purpose of this research work is to determine the removal efficiency of Cu^(2+)and Pb^(2+)ions using polyvinyl alcohol/neem leaf extract/chitosan(PVA/NLE/CS)composite films as adsorbent materials from an aqueous medium,with respect to pH,contact time,and adsorbent dosage.The synthesized composite material was characterized using Fourier Transform Infrared(FTIR)spectroscopy,thermogravimetric analysis-Derivative Thermogravimetry(TGA-DTG),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),and scanning electron microscopy-Energy Dispersive X-ray Spectroscopy(SEM-EDX).The antibacterial activity and swelling response of the material were studied using suitable methodologies.The FTIR study confirmed the interactions among PVA,chitosan,and neem leaf extract.The TGA data reveal the excellent thermal stability of the developed composite films.The SEM micrograph indicates a homogeneous phase morphology with good compatibility among chitosan,the monomer,and the leaf extract.The antibacterial study revealed that the prepared PVA/NLE/CS films exhibit improved antibacterial activity against bacterial growth.It was found that at pH 6.0,the adsorption capacity for both toxic metal ions is maximum,and decreases with a further rise in pH.At this pH,the adsorption capacity of PVA/NLE/CS films increases with a gradual increase in adsorbent dosage,and at a specific pH,the adsorption capacity for Cu^(2+)is greater than that for Pb^(2+).The adsorption efficiency is a function of contact time and was found to be maximal at 180 min.Hence,the developed composite material is effective for the removal of metal ions from wastewater.
基金supported by the National Major Science and Technology Project"Key Technologies for Exploration and Development of Continental Shale Gas in Yan'an"(No.2017ZX05039001005).
文摘In order to improve the calculation method of the isosteric adsorption heat,clarify thermodynamic characteristics of CH4 adsorption by continental shale and reveal the adsorption mechanism,this paper selected shale samples from the seventh Member of Yanchang Formation of Upper Triassic in the Yanchang Gasfield of the Ordos Basin as the research object.The isothermal adsorption experiment was carried out on the CH4 adsorption by continental shale and the excess adsorption curves were plotted.Then,the characteristics of the isosteric adsorption heat of the shale with different types of adsorption capacity were illustrated by analyzing and comparing the difference between excess and absolute adsorption capacity.And the following research results were obtained.First,under the same temperature and pressure,absolute adsorption capacity is higher than the excess values.The difference between them is higher under low temperature and high pressure and it is in the relationship of exponential function with the equilibrium pressure.If excess adsorption capacity is used to evaluate the adsorptive property of shale reservoirs,the evaluation result will be underestimated.Second,for CH4 adsorption by Yanchang Formation shale,the absolute and excess isosteric adsorption heat values have a linear positive correlation with absolute and excess adsorption capacity respectively,and the intermo-lecular force of adsorbate has a dominant effect on isosteric adsorption heat values.Third,absolute isosteric adsorption heat value is less than the excess heat.The relative error is in the range of 18.18e49.79%,and it is higher in the stage with low adsorption capacity.If excess adsorption capacity is taken as the basic data to calculate initial isosteric adsorption heat values,the calculation result will be overvalued,and consequently,the evaluation of the intermolecular force of adsorbent and adsorbate is overestimated.
基金Supported by the National Natural Science Foundation of China (Nos. 40871110 and 30828005)the National Water Pollution Control and Management Special Project of China (No. 2009ZX07102-003)+1 种基金the Special Project of Science and Technology of Guangdong Province,China (No. 2008A080800028)the Supporting Project of Science and Technology of Guangzhou City,China (No. 2008Z1-E621)
文摘Constructed wetlands （CWs） are engineered systems that utilize natural systems including wetland vegetations, soils, and their associated microbial assemblages to assist in treating wastewater. The kinetic adsorption of ammonium nitrogen （NH＋-N） by CW substrate materials such as blast furnace slag （BFS）, zeolite, ceramsite, vermiculite, gravel, paddy soil, red soil, and turf, was investigated using batch experiments and kinetic adsorption isotherms. Both Freundlich and Lang- muir isotherms could adequately predict the NH＋-N adsorption process. The maximum adsorption capacities of NH＋-N, estimated from the Langmuir isotherm, ranked as： zeolite （33 333.33 mg kg^-1） 〉 turf （29274.01 mg kg^-1） 〉 BFS （5000 mg kg^-1） 〉 vermiculite （3333.33 mg kg^-1） 〉 gravel （769.23 mg kg^-1） 〉 paddy soil （588.24 mg kg^-1） 〉 red soil （555.56 mg kg^-1） 〉 ceramsite （107.53 mg kg^-1）. Some properties of the substrate materials, including bulk density, specific gravity, hydraulic conductivity, uniformity coefficient （K60）, curvature coefficient （Co）, organic matter, pH, exchangeable （or active） Cu, Fe, Zn and Mn, total Cu, and Fe, Mn, Zn, Cd, Pb and Ca, had negative correlations with NH＋-N adsorption. Other properties of the substrate materials like particle diameter values of D10, 030 and 060 （the diameters of particle sizes of a substrate material at which 10%, 30% and 60%, respectively, of the particles pass through the sieve based on the accumulative frequency）, cation exchange capacity （CEC）, exchangeable （or active） Ca and Mg, and total K and Mg had positive correlations with NH＋-N adsorption. In addition, active K and Na as well as the total Na had significant positive correlations with NH＋-N adsorption. This information would be useful for selection of suitable substrate materials for CWs.
基金supported by the United Fund Project of National Natural Science Foundation of China (Grant No. U1262209)the National Natural Science Foundation of China (Grant No. 41602155)the Young Scholars Development Fund of SWPU (No. 201599010137)
文摘In this paper, the methane adsorption behaviours in slit-like chlorite nanopores were investigated using the grand canonical Monte Carlo simulation method, and the influences of the pore sizes, temperatures, water, and compositions on methane adsorption on chlorite were discussed. Our investigation revealed that the isosteric heat of adsorption of methane in slit-like chlorite nanopores decreased with an increase in pore size and was less than 42 kJ/mol, suggesting that methane adsorbed on chlorite through physical adsorption. The methane excess adsorp- tion capacity increased with the increase in the pore size in micropores and decreased with the increase in the pore size in mesopores. The methane excess adsorption capacity in chlorite pores increased with an increase in pressure or decrease in pore size. With an increase in temperature, the isosteric heats of adsorption of methane decreased and the methane adsorption sites on chlorite changed from lower- energy adsorption sites to higher-energy sites, leading to the reduction in the methane excess adsorption capacity. Water molecules in chlorite pores occupied the pore wall in a directional manner, which may be related to the van der Waals and Coulomb force interactions and the hydrogen bonding interaction. It was also found that water molecules existed as aggregates. With increasing water content, the water molecules occupied the adsorption sites and adsorption space of the methane, leading to a reduction in the methane excess adsorption capacity. The excess adsorption capacity of gas on chlorite decreased in the following order： carbon dioxide 〉 methane 〉 nitrogen. If the mole fraction of nitrogen or carbon dioxide in the binary gas mixture increased, the mole fraction of methane decreased, methane adsorption sites changed, and methane adsorption space was reduced, resulting in the decrease in the methane excess adsorption capacity.
文摘A semi-empirical adsorption kinetic model was proposed with the time compensation method to describe the chemisorption of SO2 in flue gas by carbon adsorbents for flue gas purification.The change in adsorption capacity and adsorption rate with time at different water vapor concentrations and different SO2 concentrations was studied.The model was in good agreement with experimental data.The surface reaction was probably the rate controlling step in the early stage for SO2 adsorption by ZL50 activated carbon.The parameters m and n in the nth order adsorption kinetic model were related to the magnitude of the time compensation and adsorption driving force,respectively.The change of parameter n with water vapor concentrations and sulfur dioxide concentrations was studied and some physical implications were given.The sum of square errors was less than 1.0 and the average absolute percentage deviations ranged from 0.5 to 3.2.The kinetic model was compared with other models in the literature.
文摘Safe application of chromium （Cr）-containing organic industrial wastes to soil requires considering the ability of the soil to adsorb Cr. In this study, the maximum Cr adsorption capacity was assessed for the bulk samples and their clay and iron-free clay fractions of four subtropical soils differing in mineralogy. To this end, the samples were supplied with Cr（Ⅲ） nitrate solutions at pH 4.5 or 5.5. The results of Cr（Ⅲ） adsorption fitted to a Freundlich equation and the adsorption capacity was positively correlated with soil organic matter and iron oxide contents. The clay fractions adsorbed more Cr per unit mass than the bulk soils and the iron-free clay fractions. The Cr（Ⅲ） adsorption capacity increased with increasing soil pH due to more charges on adsorbing surfaces. Our results suggest that the soils rich in organic matter and iron oxides and having a pH above 4.5 are suitable for application of Cr（Ⅲ）-loaded industrial wastes.
基金supported by the Open Fund of State Key Laboratory of Eco-hydraulics in Northwest Arid Region of China (No. 2019 KFKT-8)the National Natural Science Foundation of China (Nos. 51609084, 51679089, and 41807161)the “948” Program of the Ministry of Water Resources of China (No. 201328)。
文摘Extensive use of chemical fertilizers in agriculture can induce high concentration of ammonium nitrogen(NH4^(+)_(-)N) in soil. Desorption and leaching of NH4^(+)_(-)N has led to pollution of natural waters. The adsorption of NH4^(+)_(-)N in soil plays an important role in the fate of the NH4^(+)_(-)N. Understanding the adsorption characteristics of NH4^(+)_(-)N is necessary to ascertain and predict its fate in the soil-water environment, and pedotransfer functions(PTFs) could be a convenient method for quantification of the adsorption parameters. Ammonium nitrogen adsorption capacity, isotherms, and their influencing factors were investigated for various soils in an irrigation district of the North China Plain. Fourteen agricultural soils with three types of texture(silt, silty loam, and sandy loam) were collected from topsoil to perform batch experiments. Silt and silty loam soils had higher NH4^(+)_(-)N adsorption capacity than sandy loam soils.Clay and silt contents significantly affected the adsorption capacity of NH4^(+)_(-)N in the different soils. The adsorption isotherms of NH4^(+)_(-)N in the 14 soils fit well using the Freundlich, Langmuir, and Temkin models. The models’ adsorption parameters were significantly related to soil properties including clay,silt, and organic carbon contents and Fe^(2+) and Fe^(3+) ion concentrations in the groundwater. The PTFs that relate soil and groundwater properties to soil NH4^(+)_(-)N adsorption isotherms were derived using multiple regressions where the coefficients were predicted using the Bayesian method. The PTFs of the three adsorption isotherm models were successfully verified and could be useful tools to help predict NH4^(+)_(-)N adsorption at a regional scale in irrigation districts.
基金financially supported by the Outstanding Youth Fund of the Natural Science Foundation of Jiangsu, China (No. BK20150050)the National Key Research and Development Program, China (No. 2016YFD0800204)+2 种基金the National Natural Science Foundation of China (No. 21677149)the Institute of Soil Science, Chinese Academy of Sciences (No. ISSASIP1616)the Key Program of Frontier Sciences, Chinese Academy of Sciences (No. QYZDJSSW-DQC035)
文摘The chars in the natural environment can affect the migration of polybrominated diphenyl ethers(PBDEs). However, there is insufficient research relating to the adsorption behavior and mechanisms of PBDEs on biochars. This study examined the adsorption kinetics of 2,2′,4,4′-tetrabromodiphenyl ether(BDE-47) on maize straw-derived biochars(MSBCs) pyrolyzed at four different temperatures via batch experiments. The biochar samples were characterized using Fourier transform infrared(FTIR) spectroscopy,Raman spectra, and elemental analysis. A two-compartment first-order model and pseudo-second-order model exhibited a better fit compared to a pseudo-first-order model in describing the BDE-47 adsorption on biochars, which was dominated by a slow adsorption compartment and chemisorption. The MSBC pyrolyzed at 600 °C had the highest BDE-47 adsorption capacity owing to its relatively large specific surface area and relatively high aromaticity compared with the other three MSBCs pyrolyzed at 300, 400, and 500 ℃.However, there was no significant difference in adsorption capacity among the other three biochars. The organic functional groups coupled with the graphene structures of biochars and the hydrophobic effect of the functional groups promoted the adsorption of BDE-47. Pore diffusion was not the sole rate-limiting step;film diffusion was also involved in the adsorption process of BDE-47 on biochars. The overall results demonstrate the transport and potential treatment of PBDEs using biochars.
基金Project 50639010 and 50678032 supported by the National Natural Science Foundation of China
文摘The adsorption capacity of landfill liners containing granular activated carbon (GAC), or bentonite activated by acid, for Cr(VI) was investigated by batch testing. The results show that both GAC and activated bentonite could be used as sorptive amendments for trapping Cr(VI) in landfill liners. The Cr(VI) sorption to GAC and activated bentonite is much greater than Cr(VI) sorption to natural clay. The adsorption capacity of Cr(VI) onto all the soils increases with increasing temperature; adsorption capacity is also significantly influenced by soil-solid concentration. As the soil-solid concentration increases the adsorption capacity first decreases logarithmically, but then stabilizes when the soil-solid concentration exceeds a critical value (e.g. 400 g/L). Permeability tests were conducted in the laboratory. The results indicate that the hydraulic conductivity of landfill liners containing GAC or activated bentonite can meet the engineering requirement of 1 nm/s. One-dimensional transport simulations for Cr(VI) were performed to evaluate the effect of GAC and activated bentonite on landfill liners. The results of the simulations indicate that landfill liners containing GAC, or activated bentonite, significantly retard the transport of Cr(VI) relative to a conventional clay liner.
文摘The adsorption capacities of new humic acids isolated from Yakouren forest （YHA） and Sahara （Tamenrasset： THA） soils （Algeria） and commercial humic acid （PFHA） on polyaniline emeraldine base （PEB） were studied at pH 6.6. Also the adsorption of heavy metals such as Cd 2＋ , Zn 2＋ and Ni 2＋ on humic acid-polyaniline systems （HA-PEB） was investigated at the same conditions. HA-PEB compounds were characterized by scanning electron microscopy （SEM）, infrared spectrometry and cavity microelectrode. In addition, batch adsorption and cavity microelectrode were used in the adsorption study of Cd 2＋ , Zn 2＋ and Ni 2＋ on HA-PEB. To develop biocaptors of polluting metals using a cavity microelectrode modified by HA-PEB systems, the adsorption kinetic and adsorption capacity were investigated. The SEM analysis showed that the presence of humic acid affected the PEB surface and caused the formation of a granular morphology. The maximum adsorption capacities （q max ） of PFHA, THA and YHA determined by adsorption isotherms were 91.31, 132.1 and 151.0 mg/g, respectively. Batch adsorption results showed that q max of Cd 2＋ , Zn 2＋ and Ni 2＋ on HA-PEB followed the order： THA-PEB YHA-PEB PFHA-PEB. The voltammograms obtained with HA-PEB modified cavity microelectrode showed the appearance of new redox couples reflecting the adsorption of HA on PEB. Metal-humic acid-polyaniline voltammograms were characterized by appearance of oxidation-reduction couples or reduction wave corresponding to metal. Finally, the result may be exploited to develop a biocaptor based on the cavity microelectrode amended by THA-PEB and YHA-PEB.
