Adsorption Isotherm Test Research Articles

Effect of Various Silica Nanofluids: Reduction of Fines Migrations and Surface Modification of Berea Sandstone

This work is aimed at addressing surface modification of berea sandstone by silica nanofluids (NFs). Three types of nanofluids were used: silica/deionized water (DIW), silica in DIW with a stabilizer fluid (3-Mercaptopropyl Trimethoxysilane) and sulfonate-functionalized silica in DIW. Core flood studies showed that application of silica nanoparticles (NPs) improved water injectivity in sandstone. The change in the measured zeta potential indicated surface modification of sandstone by application of NPs. Computation of the surface forces showed that the modified berea sandstone has net attractive potential with fines (obtained from water/rock interaction) leading to reduction of fines migration, hence improvement of water injectivity. It was also observed that the silica NPs have greater affinity to adhere/adsorb on quartz surfaces than kaolinite in berea core. This was confirmed by scanning electron microscope imaging and isothermal static adsorption tests. Although the stabilizing of NFs almost did not reduce the fine migration, as was qualitatively indicated by the pressure drop, it enhanced the NPs adsorption on the minerals as obtained by isothermal static adsorption tests. The reduction of fines migration due surface modification by silica NP suggests that NPs can be utilized to overcome the problem of formation damage induced during low salinity flooding in sandstones.

Study of adsorption behavior in shale reservoirs under high pressure

Understanding adsorption behavior is of critical importance for the development of shale reservoirs. However, most extant adsorption models cannot properly describe isothermal adsorption when the pressure exceeds a specific value at which the Langmuir volume is obtained. In this study, a modified bi-adsorbent simplified local density/Peng-Robinson model (SLD-PR) was developed in which adsorption in both organic and inorganic components of shale was considered at the same time, and a new modification was imposed on the covolume parameter in equation of state. The model was demonstrated on high pressure methane isothermal adsorption tests of terrestrial shale samples and the high pressure methane adsorption data for marine shales available in the literature samples. It is found that the proposed model can fit isothermal adsorption well for both terrestrial and marine shales with different shapes of adsorption curves, especially in the high pressure range. With the application of the model, it was determined that the methane adsorption capacity of Yanchang Formation terrestrial shale exhibits a positive correlation with its TOC content. Other factors, such as specific surface area, clay content and temperature, also significantly affect adsorption capacity. Furthermore, in the calculation of in-situ gas storage in shale reservoirs, the proposed model produces more reliable results generally when compared with the original SLD-PR model and the Langmuir model.

Shale hydration inhibition characteristics and mechanism of a new amine-based additive in water-based drilling fluids

In this work, shale hydration Inhibition performance of tallow amine ethoxylate as a shale stabilizer in water based drilling fluid, was investigated through these tests: bentonite hydration inhibition test, bentonite sedimentation test, drill cutting recovery test, dynamic linear swelling test, wettability test, isothermal water adsorption test, and zeta potential test. The results showed that bentonite particles are not capable of being hydrated or dispersed in the mediums containing tallow amine ethoxylate; tallow amine ethoxylate had shown a comparable and competitive inhibition performance with potassium chloride as a common shale stabilizer in drilling industry. Some amine functional groups exist in tallow amine ethoxylate structure which are capable of forming hydrogen bonding with surfaces of bentonite particles. This phenomenon decreased the water adsorption on bentonite particles' surfaces which results in reduction of swelling. Tallow amine ethoxylate is also compatible with other common drilling fluid additives.

Synthesis of Pt/K2CO3/MgAlOx\u2013reduced graphene oxide hybrids as promising NOx storage\u2013reduction catalysts with superior catalytic performance

Pt/K2CO3/MgAlOx–reduced graphene oxide (Pt/K/MgAlOx–rGO) hybrids were synthesized, characterized and tested as a promising NOx storage and reduction (NSR) catalyst. Mg–Al layered double hydroxides (LDHs) were grown on rGO via in situ hydrothermal crystallization. The structure and morphology of samples were thoroughly characterized using various techniques. Isothermal NOx adsorption tests indicated that MgAlOx–rGO hybrid exhibited better NOx trapping performance than MgAlOx, from 0.44 to 0.61 mmol · g−1, which can be attributed to the enhanced particle dispersion and stabilization. In addition, a series of MgAlOx–rGO loaded with 2 wt% Pt and different loadings (5, 10, 15, and 20 wt%) of K2CO3 (denoted as Pt/K/MgAlOx–rGO) were obtained by sequential impregnation. The influence of 5% H2O on the NOx storage capacity of MgAlOx–rGO loaded with 2 wt% Pt and 10% K2CO3 (2Pt/10 K/MgAlOx–rGO) catalyst was also evaluated. In all, the 2Pt/10 K/MgAlOx–rGO catalyst not only exhibited high thermal stability and NOx storage capacity of 1.12 mmol · g−1, but also possessed excellent H2O resistance and lean–rich cycling performance, with an overall 78.4% of NOx removal. This work provided a new scheme for the preparation of highly dispersed MgAlOx–rGO hybrid based NSR catalysts.

Coalbed methane adsorption behavior and its energy variation features under supercritical pressure and temperature conditions

A majority of coalbed methane (CBM) in coal reservoirs is in an adsorbed state. Under geological pressure and temperature conditions (beyond the critical region of methane), supercritical adsorption occurs between methane (CH4) molecules and coal surface. In order to better characterize CBM supercritical adsorption behaviors, isothermal adsorption tests were conducted to simulate the adsorption under different reservoir pressures and temperatures. It is observed that the temperature influences adsorption behaviors little under low-pressure conditions but weakens the sorption capacity of coals under high-pressure conditions. Since the adsorption volume obtained from isothermal adsorption tests is Gibbs excess adsorption volume, it was transformed to the absolute adsorption volume which is essential for reliable gas-in-place estimates. A hypothesis was proposed that a maximum adsorption volume for a certain adsorbent exist in the limiting case of supercritical conditions. Based on this, the limiting adsorption model was built in reference to the Dubinin-Astakhov (DA) adsorption model and Henry dissolution law. Additionally, different energy varying trends (adsorption potential, adsorption space, reduction of surface free energy and isosteric heat of adsorption) over pressure and temperature indicate that the adsorption of CH4 by coals is actually the attraction between CH4 molecules and coal molecules and also a spontaneous process to reduce surface free energy of the system. The pressure and temperature exert an impact on sorption behaviors by controlling attraction forces or kinetic energy of adsorbate and adsorbent molecules.

Performance of activated carbon-impregnated cellulose filters for indoor VOCs and dust control

An activated carbon-impregnated cellulose filter was fabricated, and the capacity to remove dust and volatile organic compounds was evaluated in a laboratory. The adsorption capacities for benzene, toluene, ethyl benzene and m-xylene gases were compared by an adsorption isotherm test conducted as a preliminary test, showing that m-xylene and benzene were the most and least favorable for adsorption onto activated carbon, respectively. Cellulose filters were made with four levels of activated carbon contents, and dust removal was performed with all of the filters showing 99 % and higher efficiencies stable with a small variation during the experiment. Activated carbon content of 5 g in the unit filter area (125 g/m2) was found optimum for benzene, toluene, ethylbenzene and m-xylene removal, as it appeared that higher than 5 g activated carbon content was unnecessary for the improvement of its capacity. With increasing benzene, toluene, ethylbenzene and m-xylene loading, the highest removal rates were determined as 0.33–0.37 mg/cm2 s for as short as 0.0046 s of air filter residence time. The rapid removal was possible because of the high surface area of the activated carbon-impregnated cellulose filter provided by powdered activated carbon, which is distinguished from the granular form in conventional activated carbon towers. As fixed within a cellulose scaffolding structure, the powdered activated carbon performed excellent benzene, toluene, ethylbenzene, and m-xylene adsorption (98.9–100 %), and at the same time, particular matters were removed in average 99.7 % efficiency after being filtered through the cellulose filter sheet.

Preparation and characterization of novel thermosensitive magnetic molecularly imprinted polymers for selective recognition of norfloxacin

Novel norfloxacin (NOR) thermosensitive magnetic molecularly imprinted polymers (T-MMIPs) were prepared with functional monomer methacrylic acid (MAA), temperature-response monomer N-isopropylacrylamide (NIPAM) and cross-linking agent N,N′-methylenebisacrylamide (MBA) by the surface imprinting technique. The silica layer and imprinted polymers layer coated on the surface of Fe3O4 nanoparticles, forming double-shell structure. The morphology and composition of the thermosensitive magnetic molecularly imprinted polymers were investigated by transmission electronmicroscope (TEM), Fourier transform infrared spectrometry (FT-IR), thermogravimetic (TGA), vibrating sample magnetometer (VSM), powder X-ray diffraction (XRD) and nitrogen adsorption analysis. The phase behavior and thermosensitivity of T-MMIPs were studied by swelling experiments and adsorption tests at different temperatures. And the adsorption performance of T-MMIPs at 35 °C were evaluated by adsorption experiments, including kinetic, isotherm and selectivity tests. The maximum capacity of T-MMIPs at 35 °C was 52.85 mg g−1. In selective recognition tests, the T-MMIPs showed the highest selectivity for NOR among four components while the T-MNIPs showed similarly adsorption for all components. The prepared T-MMIPs have great potential in the detection and separation of norfloxacin due to the good temperature response, adsorption capacity, selectivity and reusability.

Column filled with Fe-GAC and GAC to remove both As(V) and Fe(III)

First of all, Fe or/and Mn immobilized granular activated carbons (Fe-GAC, Mn-GAC, (Fe, Mn)-GAC) were synthesized and tested to remove arsenate (As(V)). The results in batch test indicated that Fe-GAC removed As(V) effectively, even though the surface area of Fe-GAC was reduced largely. Moreover, adsorption isotherm test indicated that the experimental data fit well with Langmuir model and the maximum adsorption capacity () of Fe-GAC for As(V) was , which was higher than GAC (). In column test, the simulated water, which consisted of As(V), Fe(III), Mn(II) and Ca(II) in tap water, was used. Fe-GAC column with 1 hr of pre-washing time treated As(V) effectively while GAC column removed Fe(III) better than Fe-GAC column. Moreover, the increasing pre-washing time from 1 to 9 hour in Fe-GAC column enhanced Fe(III) removal with little negative impact of As(V) removal. Mostly, the column filled with Fe-GAC and GAC (i.e. the mass ratio of Fe-GAC:GAC

Critical geological characteristics and gas-bearing controlling factors in Longmaxi shales in southeastern Chongqing, China

The southeastern Chongqing area, one of the highest potential shale gas accumulation areas in China, experienced strong tectonic movements. Due to the tectonic uplift in Himalayan period, the target shale formation is characterized by shallow burial depth and abundant fractures. The Lower Silurian Longmaxi shale was deposited under deep and shallow continental shelf environments with abundant pyrites and graptolite fossils. The lithology of the formation includes black carbonaceous shale, calcareous shale, and siliceous shale. The thickness of the shale varies greatly from 40 to 200 m from southeast to northwest with obvious zonation. Total organic carbon (TOC) content ranges from 1.0 to 4.0% and decreases upward in the formation owing to the change of sedimentary facies. The organic matter reaches dry gas zone. Porosity ranges from 0.5 to 7.9%, and the permeability is measured in the microdarcy to nanodarcy range. Abundant fragile minerals exist in the shales which benefit the hydraulic stimulation. Isothermal adsorption tests show that the sorption gas content in place of the Longmaxi shale ranges from 1.0 to 4.5 m3/t and the gas content in place reaches the standard of commercial exploitation. Factors impacting gas-bearing characteristics were analyzed using a mathematical statistic method, which demonstrates that TOC is the most important factor, especially to the sorption gas content. Meanwhile, clay content, thermal maturity, porosity, and mineral components are also significant factors regarding shale gas-bearing characteristics.

Isothermal adsorption kinetics properties of carbon dioxide in crushed coal

Understanding the dynamic response of coal to carbon dioxide sorption is crucial for optimizing carbon dioxide sequestration in unmineable coal seams and enhanced coalbed methane recovery. In order to explore the adsorption kinetics of carbon dioxide in coal, 15 isothermal adsorption tests were conducted on bituminous and sub-bituminous coals at 50°C for increasing equilibrium pressures (up to 4 MPa). The pseudo-second order (PSO) model is introduced to approximate the carbon dioxide sorption kinetics in coal, and the kinetics properties are then investigated via the PSO model. The linear relationship between (t/q) and (t) is validated and confirmed with a high correlation coefficient (>99%). The kinetics parameter, k2, decreases with both increasing equilibrium sorption pressure and increasing pressure difference. The sorption equilibrium content, Qe, in each sorption stage depends on both the final equilibrium pressure and the pressure difference. Based on the relationship between sorption content and time, the sorption content for different pressure ranges is predicted using different time intervals. The analysis indicates that the adsorption process for carbon dioxide in coal is a combination of both bulk diffusion-controlled and surface interaction-controlled processes; the former dominates the initial stage while the latter controls the majority of the overall process. © 2015 Society of Chemical Industry and John Wiley & Sons, Ltd

Physical Simulation of Temperature Influence on Methane Sorption and Kinetics in Coal (II): Temperature Evolvement during Methane Adsorption in Coal Measurement and Modeling

The dynamic thermal process for methane sorption in coal has not been quantitatively studied, and the temperature change induced by the heat of adsorption on the sorption equilibrium state has not been confirmed by tests. In order to probe the temperature evolvement and its effect on methane adsorption in coal, the temperature of the coal sample is measured using a digital temperature gauge during methane isothermal adsorption in coal. Isothermal adsorption tests for methane in coal under six different temperatures (50, 40, 30, −10, −20, and −30 °C) are conducted. Blind experiments show that the temperature increase of the tested coal sample induced by external energy brought via the filled methane and the possible Joule–Thomson effect is within 0.5 °C in this test and thus will not be considered during methane adsorption in coal. Both real test and modeling results show that the temperature of the coal sample induced by the heat of adsorption can go up to 13.79 °C during the methane adsorption process in...

Molecular dynamics simulations of molecularly imprinted polymer approaches to the preparation of selective materials to remove norfloxacin

ABSTRACTA novel molecularly imprinted polymer (MIP) designed by molecular dynamics (MD) simulations was successfully prepared with norfloxacin as a template molecule, methyl acrylic acid as a functional monomer, and ethylene glycol dimethacrylate as a crosslinker. According to the theoretical prediction and experimental preparation methods, three kinds of molecular imprinting materials were designed and synthesized with MD simulations and molecular imprinting technology. The best ratio of the template to the functional monomer to the crosslinker was 1:8:40 in these studies. The experimental results illustrate that the MD simulations were credible in compounding the components of the MIPs. The structure of the prepared polymers were characterized with various methods. To analyze the adsorption performances, many kinds of static adsorption tests, including kinetic, isotherm, and selectivity tests, were used. The results indicate that the novel adsorbents conformed to the pseudo–second‐order kinetic equation and followed the Langmuir isotherm model. The adsorption amounts of MIP2 at a ratio of 1:8:40 were about 29.35 mg/g at 298 K. The selective adsorption and reusable performance of norfloxacin were excellent. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 132, 42817.

Water-adsorption properties of Xiazijie montmorillonite intercalated with polyamine

AbstractPolyamine is a novel inhibitor applied to water-based drilling fluids in order to reduce hydration of clays, especiallymontmorillonite (MT). In the present study, thewater-adsorption properties of montmorillonite intercalated with polyamine were characterized by X-ray diffraction (XRD), diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) and adsorption isotherm tests using water, benzene and heptane. According to the XRD, DRIFT and water-adsorption test results, polyamine (PA)- intercalated montmorillonite (PA-MT) adsorbs less water than either K+- or NH+4-intercalated montmorillonite (K-MT, NH4-MT). The surface energy of MT was analysed using the van Oss- Chaudhury-Good (VCG) approach based on thewater, benzene and heptane adsorption results. The surface energy between PA-MTand water was less than that of NH4-MT and K-MT. Compared with K-MT and NH4-MT, the surface energy of the Lewis acid portion of PA-MT underwent a more significant decrease, suggesting that the hydration of unexchanged Na+ did not make a discernible contribution. The experimental water-adsorption data were fitted using Langmuir, Brunauer-Emmett-Teller (BET), and Freundlich adsorption models. The Langmuir adsorption models can be used to fit the data for water adsorption on PA-MTacross the entire p/p0 range. After plotting the experimental data in the linear format of the Freundlichmodel, only one linear region for PA-MTwas observed, indicating a singlewater-adsorption mechanism for PA-MT. When compared with PA in the absence of clay, DRIFT spectroscopy showed that the NH2 bending mode for PA-MT shifted from 1571 cm–1 to 1619.7 cm–1. This suggested an increase in hydrogen bonding (H bonding) between the ammonium group and the interlayer water. Across the entire p/p0 range, water is suggested to have adsorbed onto PA-MT through H-bonding interactions between the ammonium group and the interlayer water.

Damage mechanism and protection measures of a coalbed methane reservoir in the Zhengzhuang block

The Zhengzhuang block is an important development area in Qinshui basin in Shanxi Province, China. In this block, the amount of gas produced in many wells is not consistent with that predicted according to data concerning reservoir properties, even after fracturing (i.e., with clean fracturing fluid) or the implementation of horizontal boreholes through the reservoir. To investigate the damage mechanism, mineral composition and microstructures were analyzed using X-ray diffraction, scanning electron microscopy and thin section analysis; pore parameters were determined by a mercury intrusion test; hydration properties were tested by a dispersion and expansion experiment; the contact angle of water on reservoir cores was measured to analyze the wettability; and the sensitivities of NO. 3 coal cores were analyzed according to core flow experiments and an isothermal adsorption test. Based on the test results, the factors causing damage to the coalbed methane (CBM) reservoir in the NO. 3 coal seam included serious water blocking and stress sensitivity, followed by velocity sensitivity, water sensitivity, alkali sensitivity and acid sensitivity. To eliminate water blocking, an agent to adjust core wettability was chosen. Moreover, a new cheap inhibitor was provided to reduce core water sensitivity. Using the selected wettability adjustment agent, the inhibitor and other necessary additives, drilling fluid and fracturing liquid systems were optimized, causing considerably less damage to CBM reservoir cores, both in the wet and dry states, according to the results of core permeability tests. Compared with surface water and drilling mud applied during drilling in the gas field of the Zhengzhuang block, the optimized drilling fluid and fracturing liquid can promote methane desorption by reducing the Langmuir volume and increasing the Langmuir pressure of coal, thereby increasing gas production and recoverability of the CBM reservoir.

Adsorption Affinity of Different Types of Coal: Mean Isosteric Heat of Adsorption

Understanding the sorption behavior of gas in organic-rich sedimentary rocks and, more specifically, recognizing the adsorption properties of methane in coal and crucial steps for evaluating the coalbed methane (CBM) gas-in-place content, gas quality, and CBM recovery potential. However, the adsorption affinity of coal on methane has not been previously considered. This paper introduces the isosteric heat of adsorption in Henry’s region, renamed the mean isosteric heat of adsorption, as means to evaluate the adsorption affinity of coal on methane. 18 group isothermal adsorption tests for methane in three different coals were conducted from 243.15 to 303.15 K. The mean isosteric heat of adsorption for anthracite, lean coal, and gas-fat coal is −23.31, −20.47, and −11.14 kJ/mol, respectively. The minus signs indicate that the adsorption is an exothermal process. The mean isosteric heat of adsorption is independent of the temperature from 243.15 to 303.15 K and shows the overall heterogeneous property of dif...

Physical simulation of temperature influence on methane sorption and kinetics in coal: Benefits of temperature under 273.15K

Abstract To decrease the lost gas content in the core sampling process and make the lost gas content estimation more accurate in CBM (coalbed methane) gas-in-place estimation, the freezing core sampling technique (FCST) is proposed for coal core sampling and physical simulation of the technique is conducted. The low temperature influence on methane adsorption capacity and kinetic properties in crushed coal are investigated. Isothermal adsorption tests under low temperatures (from 243.15 K to 303.15 K) were conducted. Test results support that the low temperature (under 273.15 K) greatly inhibits methane transport in coal while enhancing methane adsorption capacity in coal. Due to its unique temperature independence the mean isosteric heat of adsorption is used to evaluate adsorptivity of coal, and the mean isosteric heat of adsorption of the tested anthracite is 23.31 kJ/mol. The low temperature (under 273.15 K) decreases kinetic parameters, such as diffusion content and the diffusion coefficient, in the isothermal diffusion process. The diffusion content is controlled by both temperature and pressure, and high pressure weakens the temperature effect on diffusion content in coal. Diffusion coefficients decrease from 5.13 × 10−12 cm2/s to 3.34 × 10−12 cm2/s when temperature decreases from 303.15 K to 233.15 K. Therefore, this study suggests that using the freezing core sampling technique can be implemented in future underground coal core sampling.

Well type and pattern optimization method based on fine numerical simulation in coal-bed methane reservoir

Coal-bed methane (CBM) is a precious clean energy. A reasonable well type and pattern design is the premise and the key to effective development of coal-bed methane. In this paper, a set of optimization method is presented which includes a fine CBM numerical model with the combina tion of the isothermal adsorption test results. Different Langmuir curves and adsorption–desorption time are corresponding to different grids in the model. The model has advantages over previous models in terms of the CBM reservoir structural characteristics and permeability anisotropy. As in most of CBM mining area, the structural characteristics are so complex that a combination of vertical and U-shaped wells is the best choice to achieve optimum production of gas. To optimize the pattern and spacing between vertical wells, different types of coal-bed cleats pressure drop rules are in consideration. Based on the CBM content in the reservoir, the distribution of different well types can be determined. The optimization method above has been applied in one pilot area in QinDuan Block, China. The result shows that combination of U-shaped and vertical wells in a diamond well pattern will provide the best CBM production scenario. In this diamond well pattern, the optimum well spacing along the long and short diagonals is 350 and 300 m, respectively. The degree of reserve recovery was predicted to up to 56.63 % after 30 years of production.

A simple method for correcting for the presence of minor gases when determining the adsorbed methane content in shale

This paper demonstrates a novel approach for correcting for the presence of minor gases when determining the adsorbed methane content in shale. Based on the widely used Langmuir isotherm in calculating the adsorbed gas, an equation is derived that converts the adsorption equilibrium partition coefficient (Kd) and maximal amount of adsorbed gas (N) at low pressure to Langmuir pressure (pL). Headspace gas chromatography (HS-GC) is used to determine the Kd and N of the minor gas species present in the shale. The results indicate that the method satisfactorily accounts for the presence of minor gases when estimating the amount of adsorbed methane. This HS-GC method is much more efficient than the isothermal adsorption test currently used for the measurement of adsorption parameters of minor gas species in shale. Therefore, this new approach will improve the speed and accuracy of estimating the amount of adsorbed methane in shale deposits.

Direct Adsorption Isotherms of AEAs and Fly Ash: α-Olefin Sulfonate and Combination Admixtures

The direct adsorption isotherm test provides a direct measurement of the air entraining admixtures (AEAs) adsorption by fly ash in concrete. This method was developed and tested using a popular Vin...

Removal of Cadmium and Lead from Aqueous Solution by Hydroxyapatite/Chitosan Hybrid Fibrous Sorbent: Kinetics and Equilibrium Studies

Hydroxyapatite (HAp)/chitosan composites were prepared by a coprecipitation method, dropping a mixture of chitosan solution and phosphoric acid solution into a calcium hydroxide solution. Using the HAp/chitosan composites prepared, HAp/chitosan hybrid fibers with various HAp contents were prepared by a wet spinning method. X-ray diffraction and scanning electron microscopy analyses revealed that HAp particles were coated onto the surface of the fiber, and the surface roughness increased with increasing the HAp contents in the fiber. In order to evaluate the heavy metal removal characteristics of the HAp/chitosan hybrid fiber, adsorption tests were conducted and the results were compared with those of bare chitosan fibers. The results showed better performance in heavy metal ion removal for the HAp/chitosan hybrid fiber than the chitosan fiber. As the HAp content in the hybrid fiber increased, the removal efficiency of heavy metal ions also increased due to the increase of the specific surface area of the HAp/chitosan hybrid fiber. Adsorption kinetic and isotherm tests revealed that Pb2+and Cd2+adsorption to the hybrid fiber follows pseudo-second-order kinetic and Langmuir-type adsorption, respectively.