Analysis of CH_(4) and H_(2) Adsorption on Heterogeneous Shale Surfaces Using aMolecular Dynamics Approach

Determining the adsorption of shale gas on complex surfaces remains a challenge in molecular simulation studies.Difficulties essentially stem from the need to create a realistic shale structure model in terms of mineral heterogeneityand multiplicity.Moreover,precise characterization of the competitive adsorption of hydrogen andmethane in shale generally requires the experimental determination of the related adsorptive capacity.In thisstudy,the adsorption of adsorbates,methane(CH_(4)),and hydrogen(H_(2))on heterogeneous shale surface modelsof Kaolinite,Orthoclase,Muscovite,Mica,C_(60),and Butane has been simulated in the frame of a moleculardynamic’s numerical technique.The results show that these behaviors are influenced by pressure and potentialenergy.On increasing the pressure from 500 to 2000 psi,the sorption effect for CH_(4)significantly increasesbut shows a decline at a certain stage(if compared to H_(2)).The research findings also indicate that raw shalehas a higher capacity to adsorb CH_(4)compared to hydrogen.However,in shale,this difference is negligible.

An analytical transient coal permeability model:Sorption non-equilibrium index-based swelling switch

Long-term permeability experiments have indicated that sorption-induced swelling can switch from internal to bulk depending on the evolutive sorption status.However,this sorption swelling switch mechanism has not been considered in current analytical permeability models.This study introduces a normalized sorption non-equilibrium index(SNEI)to characterize the sorption status,quantify the dynamical variations of matrix swelling accumulation and internal swelling partition,and formulate the sorption swelling switch model.The incorporation of this index into the extended total effective stress concept leads to an analytical transient coal permeability model.Model results show that the sorption swelling switch itself results in the permeability switch under stress-constrained conditions,while the confined bulk swelling suppresses the permeability recovery to the continuous reduction under displacement-constrained conditions.Model verifications show that current experimental observations correspond to the early stages of the transient process,and they could be extended to the whole process with these models.This study demonstrates the importance of the sorption swelling switch in determining permeability evolution using simple boundary conditions.It provides new insights into experimentally revealing the sorption swelling switch in the future,and underscores the requirement of a rigorous model for complex coupled processes in large-scale coal seams.

The Al_(2)O_(3)and Mn/Al_(2)O_(3)sorbents highly utilized in destructive sorption of NF_(3)

NF_(3)is commonly used as an etching and cleaning gas in semiconductor industry,however it is a strongly greenhouse gas.Therefore,the destruction of disposal NF_(3)is an urgent task to migrate the greenhouse effect.Among the technologies for NF_(3)abatement,the destructive sorption of NF_(3)over metal oxides sorbents is an effective way.Thus,the search for a highly reactive and utilized sorbent for NF_(3)destruction is in great demand.In this work,AlOOH supported on carbon-sphere(AlOOH/CS)as precursors were synthesized hydrothermally and heat-treated to prepare the Al_(2)O_(3)sorbents.The influence of AlOOH/CS hydrothermal temperatures on the reactivity of derived Al_(2)O_(3)sorbents for NF_(3)destruction was investigated,and it is shown that the Al2O3 from AlOOH/CS hydro-thermalized at 120℃is superior to others.Subsequently,the optimized Al_(2)O_(3)was covered by Mn(OH)x to prepare Mn/Al_(2)O_(3)sorbents via changing hydrothermal temperatures and Mn loadings.The results show that the Mn/Al_(2)O_(3)sorbents are more utilized than bare Al_(2)O_(3)in NF_(3)destructive sorption due to the promotional effect of Mn_(2)O_(3)as surface layer on the fluorination of Al_(2)O_(3)as substrate,especially the optimal 5%Mn/Al2O3(160℃)exhibits a utilization percentage as high as 90.4%,and remarkably exceeds all the sorbents reported so far.These findings are beneficial to develop more efficient sorbents for the destruction of NF_(3).

SYNTHESIS，REGENERATION AND APPLICATIONOF SORPTION RESINS

By means of the synthetic approach of non－polar or weak polar oil－sorbed polymers，the gel sorption resin（GSR） and the multiporous sorption resin（MSR） were prepared．The structure of the resins，sorption power，sorption speed，desorption，and sorption of organic compounds from sewage，exhaust gas and soil were discussed．Moreover，the resins were used to decrease LOD and BOD5 values of water waste from sewage factory．Theyare a klndof potential materials for environmental control．

Surface and Hydrogen Sorption Characteristics of Various Activated Carbons Developed from Rat Coal Mine （Zonguldak） and Anthracite

Activated carbon samples were developed from coal samples obtained from a coal mine, rat （Zonguldak, Turkey） and anthracite （Siberia, Russia）, applying pyrolysis in a temperature range of 600-900 ℃ under N2 flow, and activation using chemical agents such as KOH, NH4Cl, ZnCl2 at 650 ℃. Nitrogen adsorption at low temperature （77 K） was used to characterize the activated carbon samples, and their pore structure properties including pore volume, pore diameter and pore size distribution were determined by means of the t-plots and DFT methods. The surface area values were higher for rat coal samples than for anthracite one, and for the rat coal samples treated with KOH ＋ NH4Cl ＋ ZnCl2 at 650 °C [Rat650（2）] there are highest surface area and total pore volume, 315.6 m2·g^-1 and 0.156 ml·g^-1, respectively. The highest value of the hydrogen sorption capacity was found as 0.71% （by mass） for the rat coal sample obtained by KOH ＋ ZnCl2 treatment at 650 °C [Rat650（1）].

The Sorption Isosteric Heats of Rough Rice in China

Equilibrium moisture content （EMC） data for rough rice of thirteen Chinese varieties were obtained by static gravimetric method at five different temperatures （10, 20, 25, 30, and 35 ℃） and 11% to 96% equilibrium relative humidity （ERH）. Six models, i.e., Brunauer-Emmett-Teller, Guggenheim-Anderson-deBoer, Modified Chung-Pfost （MCPE）, Modified Henderson, Modified Oswin, and Strohman-Yoerger （STYE） fitted the EMC/ERH data based on the coefficient of determination, residue sum-of-squares, standard error of estimate, and mean relative percent error. The best fitted equations were MCPE and STYE, but MCPE is three-parameter, readily transformed equation and adopted in this study. The isosteric heats for both rough rice desorption and adsorption, and for both the sorption of Japonica and Indica rice, decreased rapidly with an increase in seed moisture content （m.c.） until the m.c. of 20% dry basis （d.b.） reached, and thereafter they decreased smoothly with increasing moisture content. The isosteric heats of rough rice desorption were higher than those of adsorption below the m.c. of 22.5% d.b., but thereafter, there was no significant difference found between desorption and adsorption. The sorption isosteric heats of Indica rice were slightly higher than those of Japonica rice under all moisture contents at a constant temperature. These results provide a sound basis for future work on the drying and storage of rice.

Sorption Properties of a Bentonite Based Material for Removal of Uranium from Alum Shale Leachate

A dynamic sorption experiment was performed for removal of uranium （VI or 6＋） from a leachate from an alum shale landfill with a diatomite-bentonite based sorbent in a laboratory scale. Such material was grounded and treated chemically with H3PO4 （phosphoric acid） and thermally for improving its porosity and resistance to water flow. A specific surface area of 209 m2·g-1 was determined by the BET method. A sorption capacity of 30 μg·gl and 0.6 μg·g-1 was obtained at a pH of 7.5 and 4 respectively by means of Langmuir and Freundlich isotherm models. The flow rate was 3 mL·min-1 was effective for controlling the pH inside of the column. The sorption mechanism was investigated along with desorption of the element of interest for further process design considerations for a treatment unit on the landfill site.

Enhanced and irreversible sorption of pesticide pyrimethanil by soil amended with biochars

Biochar derived from partial combustion of vegetation is ubiquitous and potentially effective in sequestration of environmental contaminants. Biochars were prepared by burning of red gum （Eucalyptus spp.） woodchips at 450 and 850℃ （labeled as BC450 and BC850）. These two biochars were found to possess markedly different properties in terms of surface area and porosity. Short-term equilibration tests （24 hr） were conducted to assess the sorption-desorption behavior of pyrimethanil in the soil amended with various amounts of biochar of each type, with a special focus on the desorption behavior of the sorbed pesticide through four times successive desorption by dilution. Sorption coefficient and isotherm nonlinearity of the amended soils progressively increased with the content of biochar in the soil. Biochar BC850 with higher surface area and microporosity showed a stronger effect on the reversibility of sorption pesticide. The soils amended with 5% BC450 and 1% BC850 had nearly the same sorption capacity for pyrimethanil; however, their desorption processes were very different with 13.65% and 1.49% of the sorbed pesticide being released, respectively. This study suggested that biochar in soil could be an important factor for immobilization of a pesticide and thus affecting its environment fate in soil.

Sorption of Heavy Metal and Organic Pollutants on Modified Soils

Sorption characteristics of both an organic pollutant (phenol) and a heavy metal (cadmium ion) on the clay layer of a Lou soil (Eum-orthic Anthrosol in Chinese Soil Taxonomy) along with the sorption mechanism were investigated using three soil treatments: modification with a cationic surfactant cetyltrimethylammonium bromide added at an amount equivalent to 50% and 100% of the soil CEC (50%CB and 100%CB), modification with an amphoteric surface-modifying agent dodecyldimethylbetaine (commercially known as BS-12) added at an amount equivalent to 50% and 100% of the soil CEC (50% BS and 100%BS), and an unmodified control (CK). Results showed that the BS soil treatments increased sorption of both the heavy metal Cd2+ and the organic pollutant phenol. The equilibrium sorption amount of Cd2+ decreased in the order: 50%BS > 100%BS > CK > 50%CB > 100%CB, with the BS soil treatments being about 1.3 to 1.8 times higher and the CB soil treatments about 23% to 41% lower than CK. Both the single-site and two-site Langmuir models could be applied to describe the sorption of Cd2+ in each soil treatment. The equilibrium sorption amount of phenol on the soil samples decreased in the order: 100%CB > 50%CB > 100%BS > 50%BS > CK, with the CB soil treatments being 41.0 to 79.6 times higher and the BS soil treatments 4.0 to 8.3 times higher than CK. The Freundlich equation could also be used to describe the sorption characteristics of phenol. In the BS soil treatments, both an organophobic long carbon chain and hydrophilic charged groups resulted in a relatively strong sorption ability for both heavy metals and organic pollutants. In addition, the sorption ratio K, the ratio of phenol sorption amount of the modified soil to that of CK, increased initially and decreased later with the amount of phenol added, and the critical sorption ratio KC, the peak value of the sorption ratio curve plotted against the added phenol concentration, was a good index for evaluating the sorption ability of phenol in the soil.

Effect of temperature on the sorption and desorption of perfluorooctane sulfonate on humic acid

Sorption and desorption of perfluorooctane sulfonate （PFOS） on humic acid at different temperatures were studied. It was found that the sorption process could be modeled with power kinetic equation very well, suggesting that diflusion predominated the sorption of PFOS on the humic acid. The sorption capacity was doubled when the temperature increased from 5 to 35°C, and thermodynamics parameters △G0 was calculated to be –7.11 to –5.04 kJ/mol, △H0 was 14.2 kJ/mol, and △S 0 was 69.5 J/（mol·K）, indicating that the sorption was a spontaneous, endothermic, and entropy driven process. Desorption hysteresis occurred at all studied temperatures which suggested that humic acid may be an important sink of PFOS in the environment.

Effect of Dissolved Organic Matter on Chlorotoluron Sorption and Desorption in Soils

A batch equilibrium techniques was used to examine the effect of dissolved organic matter （DOM） extracted from both non-treated sludge （NTS） and heat-expanded sludge （HES） on the sorption and desorption of chlorotoluron （3-（3-chloro-p-tolyl）-1,1-dimethylurea） in two types of soils, a yellow fluvo-aquic and a red soil from China. Without DOM,sorption of chlorotoluron was significantly greater （P 〈 0.05） in the red soil than in the yellow fluvo-aquic soil. However,with DOM the effect was dependent on the soil type and nature of DOM. Chlorotoluron sorption was lower in the yellow fluvo-aquic soil than in the red soil, suggesting that with the same DOM levels the yellow fluvo-aquic soil had a lower sorption capacity for this herbicide. Application of DOM from both NTS and HES led to a general decrease in sorption to the soils and an increase in desorption from the soils. Desorption of chlorotoluron also significantly increased （P 〈 0.05） with an increase in the DOM concentration. Additionally, for sorption and desorption, at each DOM treatment level the NTS treatments were significantly lower （P 〈 0.05） than the HES treatments. This implied that non-treated sludge had a greater effect on the sorption and desorption of chlorotoluron than heat-expanded sludge.

Freeze-thaw Effects on Sorption/Desorption of Dissolved Organic Carbon in Wetland Soils

The effects of freeze-thaw cycles on sorption/desorption of dissolved organic carbon （DOC） in two wetland soils and one reclaimed wetland soil were investigated. DOC concentrations added were 0-600 mg/L. Laboratory incubations of sorption/desorption of DOC had been carried out at -15℃ for 10 h, and then at ＋5℃ for 13 h. Soil samples were refrozen and thawed subsequently for 5 cycles. Initial Mass model was used to describe sorption behavior of DOC. The results indicate that freeze-thaw cycles can significantly increase the sorption capacity of DOC and reduce the desorption capacity of DOC in the three soils. The freeze-thaw effects on desorpfion of DOC in soils increase with the increasing freeze-thaw cycles. The conversion of natural wetlands to soybean farmland can decrease the sorption capacity and increase the desorption capacity of DOC in soils. Global warming and reclamation may increase DOC release, and subsequently increase the loss of carbon and the emission of greenhouse gas.

Batch studies of adsorption of copper and lead on activated carbon from Eucalyptus camaldulensis Dehn. bark

Powdered activated carbon (PAC) prepared from Eucalyptus camaldulensis Dehn. bark was tested for its adsorption capacity for Cu(Ⅱ) and Pb(Ⅱ). The experiment was conducted to investigate the effects of pH, contact time, initial metal concentration, and temperature. The best adsorption of both Cu(Ⅱ) and Pb(Ⅱ) occurred at pH 5, where the adsorption reached equilibrium within 45 min for the whole range of initial heavy metal concentrations (0.1-10 mmol/L). The adsorption kinetics was found to follow the pseudo-...

SORPTION AND DESORPTION CHARACTERISTICS OF CADMIUM BY FOUR DIFFERENT SOILS IN NORTHEAST CHINA

Four soils, phaeozem (PM), saline-alkali soil (SA), meadow albic bleached soil (MA) and dark brown forest soil (DB) from Northeast China were used to examine the sorption and desorption characteristics of Cd and pH influence on it. According to sorption experiment without pH control, the order of amount of absorbed Cd by soils was: SA>PM>DB>MA. The results from non-linear fitting method showed that Langmuir and Freundrich models were more adaptable than Temkin model in describing the sorption data. The maximum sorption amounts from Langmuir model were: PM>SA>MA>DB. Exponential equation for PM and SA and quadratic equation for MA and DB were suitable to fit the desorption data. The order of average desorption percentage was: MA>DB>PM>SA. The amounts of sorption by PM, DB and MA reached the maximum in pH 9.0, while sorption by SA was linearly increased in the experimental range of pH 3.3-11.4. In uniform pH, however, Cd sorption by SA was the minimum among four soils, which indicated that the more amounts of Cd absorbed by SA in isotherm sorption were ascribed to the higher soil pH. The higher sorption of Cd in PM resulted from the higher percentage of organic matter and clay components.

Numerical modeling of radionuclide migration in porous media with nonequilibrium sorption

When radionuclides migrate in porous media with water serving as carrier, the mechanism of sorption and desorption is not negligible. nonequilibrium conditions exist in sorption and desorption. In this paper,a numerical model of radionuclide migration with nonequilibrium sorption was developed.The algorithm of numerical descretizing and direct substituting was adopted in coupling of the convective-dispersive equation and the nonequilibrium sorption isotherm in this model ,and this makes it easier to solve the model numerically.A quantitative analysis is made for the first time that the influence of nonequilibrium sorption, represented by the rate coefficient which shows how quickly the nonequilibrium condition in sorption and desorption reaches equilibrium on the migration of radionuclide,and results show that it affects the migration perceptibly. Finally the model was verified by using the observed data of radionuclide migration test conducted in the field, and which clarified its availability.

Equilibrium and kinetics of copper(Ⅱ) biosorption by Myriophyllum spicatum L.

The potential use of Myriophyllum spicatum L. biomass as a biosorbent for the removal of copper（ Ⅱ ） from aqueous solution was investigated in laboratory condition. The sorption experiments were undertaken to obtain copper（ Ⅱ ） biosorption properties of M. spicatum L., i.e. equilibrium time, the maximum capacity, and rate constants. Copper（ Ⅱ ） biosorption was fast and equilibrium was attained within 35 min at initial copper（ Ⅱ ） concentration of 6 mg/L. Different isotherm models including the Langmuir, Freundlich, Temkin and Redlich-Peterson model, were used to investigate the sorption capacity and isotherm. These models showed an excellent match with the experimental data except for the Freundlich model. According to the Langmuir coefficients, the maximum sorption capacity of copper onto M. spicatum L. was 10.80 mg/g. The kinetics of copper（ Ⅱ ） sorption was also analysed and rate constants were derived. It was found that the overall sorption process was best described by the pseudo second-order equation, and that intraparticle diffusion was not the rate determining step. The results of this study showed that M. spicatum L. can be considered as useful vehicles for the removal and recovery of copper（ Ⅱ ） from aqueous solutions.

Strontium Adsorption from Sulfuric Acid Solution by Dowex 50W-X Resins

In this study,strontium adsorption from sulfuric acid solution by different Dowex 50W-X ion exchange resins was investigated.Among these resins,Dowex 50W-X8 resin showed the maximum sorption of strontium from the aqueous solutions.The effect of pH,contact time,mass of resin,temperature,and concentration of interfering ions on strontium adsorption were evaluated to determine the optimum conditions of strontium sorption process.The kinetic models of sorption were analyzed using pseudo-first and pseudo-second order models.The results indicated that the pseudo-second order kinetic model was more appropriate than the other one.Moreover,the data obtained in this study were fitted into several sorption isotherm models and it was found that the Langmuir sorption isotherm shows the best fitting to the experimental data.

Effect of Initial Concentration on Adsorption-Desorption Characteristics and Desorption Hysteresis of Hexachlorobenzene in Soils

Adsorption and desorption are important processes that influence the transport, transformation, and bioavailability of hexachlorobenzene (HCB) in soils. To examine the adsorption-desorption characteristics of HCB, equilibrium batch experiments were carried out using two soils (red soil and paddy soil) with different initial HCB concentrations (0.25, 0.50, 0.75, 1.00, 1.50, 2.50, 3.50, and 5.00 mg L-1 ) by using 0.01 mol L-1 calcium chloride as the background solution. The successive desorption experiments (48, 96, 144, 192, and 240 h) were conducted after each adsorption equilibrium experiment. The results revealed that adsorption and desorption isotherms of HCB on two soils were nonlinear, which can be best described by the Freundlich equation with the square of the correlation coefficient (r 2 ) ranging from 0.97 to 0.99. Desorption of HCB from the two soils exhibited hysteresis at all HCB concentrations because the Freundlich desorption coefficients were always higher than the Freundlich adsorption coefficients. The hysteretic effect was enhanced with increasing initial HCB concentration, and positive hysteresis was observed at different concentrations.

Effects of Pb^(2+), Cd^(2+) and Cu^(2+) on the Aqueous Zn^(2+) Sorption by Hydroxyapatite

In this paper, the behaviors of aqueous zinc sorption by hydroxyapatite in the co-existence of Pb^2＋, Cd^2＋ and Cu^2＋ are investigated, the effects of Pb^2＋, Cd^2＋ and Cu^2＋ on the sorption of Zn^2＋ are discussed, and the hydroxyapatite sorption capabilities for Pb^2＋, Cd^2＋, Cu^2＋ and Zn^2＋ are compared. The experimental results show that the Zn^2＋ removal efficiency decreases gradually with the increase of the Cd^2＋ concentration of the solution, and there is no sorption preference between Cd^2＋ and Zn^2＋. On the other hand, the Zn^2＋ removal efficiency rapidly decreases rapidly with the increase of the Cu^2＋ concentration of the solution, and there is a clear sorption preference between Cu^2＋ and Zn^2＋. It is noticed that the Zn^2＋ removal efficiency is hardly changed with the variance of Pb^2＋ concentration because the removal mechanisms for these two ions are totally different. It is concluded that the adsorption affinities of the heavy metals for the hydroxyapatite follows this sequence： pb^2＋〉 Cu^2＋〉 Cd^2＋〉 Zn^2＋.

Sorption equilibrium moisture and isosteric heat of Chinese wheat bran products added to rice to increase its dietary fibre content

More and more people concern about supplementing dietary food with wheat bran to increase fibre content,but there has been little study of the sorption isotherms and isosteric heats of wheat bran fibre products,which are important to the quality and storage durability of such commodities.This study collected equilibrium moisture content(EMC)and equilibrium relative humidity(ERH)data on six Chinese wheat bran products via the static gravimetric method and analysed their sorption isosteric heats.Results showed that all six wheat bran products had sigmoidal isotherms.The data were best fitted by polynomial,modified GAB,modified Oswin,and modified Halsey models.The relative safe moisture contents of the six wheat bran products were 12.20%–13.86%wet basis(w.b.).The heat of vaporization of wheat bran products approached the latent heat of pure water at around a moisture content(MC)of 22.5%and approximately 2450 kJ/kg.A process of extrusion and ultrafine grinding reduced the solid surface area and sorption isosteric heats of the monolayer,multilayer and condensed water regions in the wheat bran products.In the temperature range of 10–37℃,the EMC of sorption in monolayer,multilayer and condensed water regions decreased with increasing temperature.The milled rice to which 1%–3%200-mesh wheat bran product was added maintained its texture when made into cooked rice and its thermomechanical properties when made into rice dough.After processing by extrusion and ultrafine grinding,wheat bran products have a lower solid surface area and lower monolayer water content(Mm)and sorption isosteric heat values.Some 3%200-mesh wheat bran product can be added to cooked rice for increasing its fibre content and making it more nutritious.