Langmuir Parameters Research Articles

Synthesis of Anionic Hydrogels for Uranyl Ion Adsorption

In this study, the anionic hydrogels were prepared in existence of crosslinker (N, N’-methylenebisacrylamide) by free radical addition reaction in aqueous solutions of neutral acrylamide and 2-hydoxyethyl methacrylate monomers and anionic comonomers such as mesaconic acid with 2 carboxyl groups or aconitic acid with 3 carboxyl groups. Hydrogels were characterized by FT-IR and DSC analysis. The effects of temperature, pH, adsorbent mass and concentration on uranyl ion adsorption onto the anionic hydrogels were investigated. It was determined that adsorption of UO 2 2+ ions to prepared hydrogels did not change with temperature and increased with increasing pH. The adsorption of u ranyl ion from aqueous solutions onto the anionic hydrogels was evaluated by applying Giles, Langmuir and Temkin isotherms to experimental results. According to the Giles adsorption isotherms classification of hydrogels UO 2 2+ ions adsorption prepared from adsorption isotherms formed, L type was determined and Langmuir parameters were calculated. It was determined that adsorption of UO 2 2+ ions to hydrogels prepared from R L values calculated for 1000 mg L -1 UO 2 2+ ion concentration is favorable.

The evolutionary history of methane adsorption capacity with reference to deep Carboniferous-Permian coal seams in the Jiyang Sub-basin: Combined implementation of basin modeling and adsorption isotherm experiments

Carboniferous-Permian (C-P) coal seams experienced multiple burial and uplift events, which result in complex gas adsorption and desorption processes. Therefore, the understanding of the adsorption history and its dominant factors contribute to determining present-day coalbed methane (CBM) storage and enhance the development of deep CBM. In this paper, we first reconstructed the burial history using the basin model and synchronously conducted the isothermal adsorption experiment. Then an adsorption model was achieved from regression analysis about Langmuir parameters, and therefore, the adsorption history was rebuilt, accompanied by temperature, pressure, and maturity. Lastly, incorporated with the hydrocarbon generation history and adsorption history, we divided the actual adsorbed stages and further analyzed the dominant factors controlling the actual adsorption amount. The results indicate that: (1) based on the adsorption model calculated using regression analysis, a real critical depth of adsorption capacity (approximately 2000 m) is obtained; (2) coal-bearing sequences experience three temperature, pressure, and hydrocarbon generation processes, and the Himalayan epoch is the main stage for producing coal-derived gas; (3) the actual adsorption history contains a maximum depth stage (250–208 Ma), reburial stage (208–110 Ma), re-uplift stage (110–50 Ma), and present stage (50 Ma–present); (4) the critical event (208 Ma) represents that generating the amount of gas is equal to the adsorption capacity in the actual adsorbed amount, and before and after the event, the dominant factors controlling the actual adsorbed amount are maturity and temperature, respectively.

The Prediction of Three Key Properties on Coalbed Methane Reservoir Using Artificial Intelligence

This research focuses on creating the prediction tools for the three key properties in coalbed methane (CBM) reservoir; the properties are gas content, Langmuir parameters, and permeability. Basically, their roles are to describe the gas in place and also future dynamic behavior of CBM reservoir. These three key properties are tried to be predicted with open-hole data as the inputs.It uses artificial neural network (ANN) and adaptive neuro fuzzy inference system (ANFIS) to generate the prediction tools. It is started from data preparation and processing, then pattern or function identifications, and finalized by validation and testing. Several training algorithms are applied for ANN such as adaptive gradient descent (ANN_GDX), Levenberg-Marquardt (ANN_LM), resilient backpropagation (ANN_RP), scaled conjugate gradient (ANN_SCG), and Bayesian regularization algorithm (ANN_BR). The first fives employ the early stopping technique for regularization, and the last one does Bayesian regularization. On the other hand, the ANFIS will use only early stopping technique.Based on this research, it is concluded that both ANN and ANFIS are able to identify the patterns or function between open-hole log data and the three key properties (TKP). Furthermore, it can be concluded that ANN_LM, ANFIS, and ANN_BR are the best selected algorithms which resulted the lowest error of TKP’s predictions.

Adsorption Studies of Lead(II) from aqueous solution onto Nanochitosan /Polyurethane /Polypropylene glycol ternary blends

Chitosan is one of the most abundant natural biopolymer after cellulose. Nanochitosan (NCS) was prepared from chitosan by ionic gelation method with sodium tripolyphosphate. Polyurethanes (PU) find wide range of applications as good materials for the concentration and removal of both organic and inorganic pollutants because of their high efficiency for sorption of various ionic and neutral materials. Polypropylene glycol (PPG) is a family of long chain polymers attached to a glycerine backbone. The present project deals with the aims in exploiting the positive behaviour of the three polymers by preparing a ternary blends of NCS/PU/PPG(1:1:1) ratio. Batch adsorption process was carried out using prepared ternary blend of various parameters influencing the Pb(II) adsorption such as initial concentration of the metal solutions, pH, agitation time and adsorbent concentrations have been studied. The characterization of the prepared sample was carried out using FTIR, XRD, TGA, DSC and SEM studies. Langmuir, Freundlich and Tempkin isotherm parameters have been determined. Adsorption kinetic data were tested using pseudo-first order, pseudo-second order and Elovich model. The kinetics of the adsorption was found to fit the pseudo-second order model. The present work proves the suitability of the ternary blend as an effective adsorbent for Pb(II).

Shale gas storage in kerogen nanopores with surface heterogeneities

Recent advances in drilling and well stimulation technologies have led to rapid development of shale formations as an important natural gas resource. However a comprehensive understanding of the source rock geochemistry is currently needed in order to identify key factors in resource shale hydrocarbon assessment and production forecasting. Previous works indicated that significant amount of methane is stored in kerogen in adsorbed state. Adsorption is controlled by surface area and surface properties of the kerogen nanopore walls. In this paper using molecular simulations we investigate the influence of surface chemistry and heterogeneity on methane storage in model kerogen pores. The results show excess amount of methane due to nanopore confinement effect, which is found to be most pronounced under the subsurface conditions when the reservoir pore pressure is in the range of 1000–5000 psi. Among the investigated surface heterogeneities, nitrogen-doped graphene surfaces are the most influential on methane storage. Doping affects strongly the Langmuir parameters related to the adsorption capacity. These results indicate that kerogen maturation and the associated changes in its composition has the potential to impact gas storage in resource shale formations. The work gives new insights into the potential impact of the surface chemistry on natural gas storage in kerogen and emphasizes the significance of source rock geochemistry.

Wood sawdust and sewage sludge pyrolysis chars for CO2 adsorption using a magnetic suspension balance

AbstractIn view of global warming caused by the uncontrolled emissions of CO2 to the environment, there is a great need to develop methods able to eliminate this pollutant. Apart from establishing new techniques, the exploration of new materials with high separation performance and low cost are of importance. This work aims to treat carbon‐metals‐rich chars originated from the fast pyrolysis of sewage sludge and wood sawdust to be used as CO2 adsorbents. The samples were washed with ethanol and dichloromethane before their physical and chemical activation to remove impregnated bio‐oil. For the chemical activation, potassium hydroxide and hydrochloric acid were used as agents. The samples were analyzed via BET, TGA, XRD, and XRF. The results were used to investigate the role played by ethanol or dichloromethane and the effect of the activation on the properties of the materials such as specific surface area, total specific pore volume, and average pore size. CO2 isotherms were obtained experimentally at 25 °C using a magnetic suspension balance and the data was used to estimate Langmuir and Freundlich isotherm parameters. After chemical treatment, the sewage sludge char specific surface area increased 11 times and had an adsorptive capacity of 1.32 × 10−3 mol/g. The wood sawdust char specific surface area increased 90 times and had an adsorptive capacity of 3.73 × 10−3 mol/g. Desorption was carried out from 5 × 105 to 1 × 105 Pa at 37 °C and the efficiencies were 89.0 and 84.4 % for the sewage sludge and wood sawdust, respectively.

Light gases saturation loading dependence on temperature in LTA 4A zeolite

The temperature dependence of saturation loading of H2, CH4, CO2, CO and N2 is evaluated for LTA 4A zeolite. For this purpose, the saturation loading is calculated at each temperature by applying a monovariate regression analysis to a number of experimental adsorption isotherms taken from previous publications in the literature within a wide range of conditions.In performing this investigation, Langmuir and Sips adsorption parameters of H2, CH4, CO2, CO and N2 are also evaluated, obtaining a satisfactorily low degree of uncertainty. This type of data, characterizing the adsorption behaviour of the considered materials are of practical importance and can be directly used by material scientists and general end-users. The role of excess and absolute loading is also discussed, highlighting that an appreciable difference is found at a relative high pressure only.

High-capacity, nanofiber-based ion-exchange membranes for the selective recovery of heavy metals from impaired waters

This contribution describes the development, performance evaluation and modeling of polyelectrolyte-modified nanofiber membranes for heavy metal recovery from impaired water. High-capacity membranes were prepared by grafting poly(acrylic acid) (PAA) and poly(itaconic acid) (PIA) to cellulose nanofiber mats. The success of polymer grafting was confirmed by attenuated total reflectance Fourier-transform infrared spectroscopy. Membrane permeabilities for a series of polymer grafted nanofiber membranes were measured by direct-flow filtration. Single-component ion-exchange isotherms were measured at constant pH for cadmium, nickel, and calcium ions. The higher metal-polymer complex stability of Cd-PIA over Cd-PAA was found to be an impact factor for achieving high Cd binding capacities. Single-component ion-exchange isotherms were well described by the Langmuir model, with maximum capacities of PIA-modified membranes that exceeded 220 mg Cd/g, comparable to traditional resin-based ion-exchange media. Moreover, membranes were selective for Cd over Ni and Ca because of different hydration energies and ionization potentials. Competitive ion-exchange measurements were made using environmentally relevant concentrations of these ions to determine the selectivity of the membranes for cadmium ion. Experimental isotherms for Cd-Ca and Cd-Ni were compared to model predictions from the competitive Langmuir model with Langmuir parameters obtained by fitting single-component isotherms. The competitive Langmuir model well describes the experimental isotherms at low metal ion concentrations. However, at high concentrations, the model underestimates experimental uptake values. This work shows that nanofiber membranes offer a high-capacity and high-productivity platform for selective removal of heavy metals, especially Cd, from impaired waters.

제올라이트 13X에 의한 배가스 성분의 흡착 특성 및 불순물의 영향

산업체에서 많이 사용되는 연소공정은 배가스 성분의 회수나 제거를 필요로 한다. 최근에는 배가스로부터 이산화탄소를 회수하기 위해 제올라이트 13X를 사용하는 MBA(이동상흡착) 공정이 개발되었다. 본 연구에서는 제올라이트 13X에 대한 이산화탄소, 질소, 이산화황 및 수증기의 흡착 실험을 수행하여 흡착평형 및 고체입자 안으로의 흡착속도를 조사하였다. 여러 실험온도에서의 흡착데이터를 Langmuir, Toth, Freundlich 등온흡착식에 적용하여 각 흡착등온식의 파라미터를 구했고, 이론식에 의한 예측값과 실험데이터가 잘 일치함을 확인하였다. 이산화황과 수증기가 불순물로 존재할 경우에 주성분인 이산화탄소의 흡착량을 측정하였다. 이성분 흡착 데이터는 순수 성분에 대해 얻어진 파라미터를 extended Langmuir 등온흡착식에 적용하여 예측한 결과와 잘 일치하였다. 다만, <TEX>$H_2O$</TEX> 불순물이 대략 <TEX>${\sim}10^{-5}H_2O\;mol/g$</TEX> zeolite 13X 이하 존재할 때에는 <TEX>$CO_2$</TEX> 흡착량이 순수 <TEX>$CO_2$</TEX>의 흡착보다 오히려 소량 증가하는 현상이 관찰되었다. 실험으로 측정한 흡착속도를 구형 입자 확산모델에 적용하여 이산화탄소, 이산화황, 질소, 수분의 확산계수와 활성화에너지를 구했다. 미량의 불순물이 흡착되어있을 때는 이산화탄소나 이산화황의 확산계수가 줄어들었다. 본 연구에서 얻어진 파라미터 값들은 실제 흡착공정의 설계에 유용할 것이다. Most of combustion processess used in industries require recovering or removing flue gas components. Recently a new MBA (moving bed adsorption) process for recovering <TEX>$CO_2$</TEX> using zeolite 13X was developed. In this study, adsorption experiments for carbon dioxide, nitrogen, sulfur dioxide, and water vapor on zeolite 13X were carried out. Adsorption equilibrium and adsorption rate into solid particle were investigated. Langmuir, Toth, and Freundlich isotherm parameters were calculated from the experiment data at various temperatures. Experimental results were consistent with the theoretically predicted values. Also <TEX>$CO_2$</TEX> adsorption amount was measured under the conditions with impurities such as <TEX>$SO_2$</TEX> and <TEX>$H_2O$</TEX>. Binary adsorption data were well fitted to the extended Langmuir isotherm using parameters obtained from pure component experiment. However, <TEX>$H_2O$</TEX> impurity less than, roughly, <TEX>${\sim}10^{-5}H_2O\;mol/g$</TEX> zeolite 13X enhanced slightly <TEX>$CO_2$</TEX> adsorption. Spherical particle diffusion model well described experimentally measured adsorption rate. Diffusion coefficients and activation energies of <TEX>$CO_2$</TEX>, <TEX>$SO_2$</TEX>, <TEX>$N_2$</TEX>, <TEX>$H_2O$</TEX> were obtained. Diffusion coefficients of <TEX>$CO_2$</TEX> and <TEX>$SO_2$</TEX> decreased with small amount of preadsorbed impurity. Parameter values from this study will be helpful to design of real commercial adsorption process.

Magnetically separable CoFe2O4/CoxFey/activated carbon composites for Cd(II) removal from wastewater

CoFe2O4 and CoxFey were anchored into activated carbon (AC) to synthesize CoFe2O4/CoxFey/AC composites using the sol–gel method for Cd(II) adsorption from wastewater. The results indicated that CoFe2O4 and CoxFey nanoparticles existed in the pores of AC. The magnetic properties of CoFe2O4/CoxFey/AC indicated it could be separated and retrieved easily using an external magnet after Cd(II) adsorption. The effects of solution pH, temperature and initial Cd(II) concentration on the Cd(II) adsorption of AC and CoFe2O4/CoxFey/AC were investigated. The standard free energy, enthalpy change and entropy change were evaluated. The kinetic parameters of Langmuir and Freundlich isothermal equation were analyzed, and the Freundlich kinetic model was feasible for describing the Cd(II) adsorption process of CoFe2O4/CoxFey/AC composites.

Biosorption of heavy metals ions in real industrial wastewater using peanut husk as efficient and cost effective adsorbent

In this research, the practical feasibility of using a low-cost adsorbent, peanut husk powder (PHP), for the removal of different heavy metals ions, Pb2+, Mn2+, Cd2+, Ni2+ and Co2+ from wastewater has been tested and the goal was achieved. The evaluation of PHP ability for bio-sorption of highly concentrated heavy metal ions (100mg/L) from real industrial wastewater has been performed. The batch treatment process was employed to obtain the optimum parameters conditions such as bio-sorbent dose, pH values, shaking time and metal ions concentrations. The optimal conditions for the removal of metal ions using PHP were approximate pH value of 6, 5g/L adsorbent dose, and 20mg/L metals ions concentration, and 3h shaking time. Thus, it was possible to obtain the highest removal efficiency with the following order Pb2+>Cd2+>Mn2+>Ni2+>Co2+. Both adsorption parameters of Langmuir and Freundlich isotherms were calculated, and better-fitted experimental data to the Langmuir equation were obtained. PHP was employed to treat a metal finishing for processing industrial wastewater, and indicated the removal efficiency of Pb2+, Fe3+, Cr3+, CN−, Cu2+, Cd2+, Mn2+, Zn2+, Co2+ and Ni2+ ions of 100%, 95%, 56%, 51%, 45%, 41%, 38%, 30% and 24%, respectively.

Adsorption of cadmium and copper in representative soils of Eastern Amazonia, Brazil

Studies of heavy metals adsorption in soil play a key role in predicting environmental susceptibility to contamination by toxic elements. The objective of this study was to evaluate cadmium (Cd) and copper (Cu) adsorption in surface and subsurface soil. Samples of six soils: Xanthic Hapludox (XH1 and XH2), Typic Hapludox (TH), Typic Rhodudalf (TR), Typic Fluvaquent (TF), and Amazonian dark earths (ADE) from Eastern Amazonian, Brazil. The soils were selected for chemical, physical and mineralogical characterization and to determine the adsorption by Langmuir and Freundlich isotherms. All soils characterized as kaolinitic, and among them, XH1 and XH2 showed the lowest fertility. The Langmuir and Freundlich isotherms revealed a higher Cu (H curve) than Cd (L curve) adsorption. Parameters of Langmuir and Freundlich isotherms indicate that soils TR, TF and ADE has the greatest capacity and affinity for metal adsorption. Correlation between the curve adsorption parameters and the soil attributes indicates that the pH, CEC, OM and MnO variables had the best influence on metal retention. The Langmuir and Freundlich isotherms satisfactorily described Cu and Cd soil adsorption, where TR, TF and ADE has a lower vulnerability to metal input to the environment. Besides the pH, CEC and OM the MnO had a significant effect on Cu and Cd adsorption in Amazon soils.

Lead biosorption onto coffee grounds: Comparative analysis of several optimization techniques using equilibrium adsorption models and ANN

In this study, coffee ground (CG) was used to remove lead ions from aqueous solution. The physicochemical properties of CG determined were: point of zero charge (pHpcz 4.5), acid and basic group quantity (1.52 and 0.17meg/g, respectively), and specific surface area (<1m2/g). The pH effect (3–5) on lead adsorption was evaluated. An increase of solution pH causes an increment of adsorption capacity and the best adsorption capacity (q=22.9mg/g) was obtained at pH 5. The calculation of the Langmuir and Freundlich isotherm parameters was performed via stochastic optimization methods, such as Genetic Algorithm, Pattern Search and Simulated Annealing, and a gradient-based method. Pattern Search showed the fastest convergence and it generated feasible parameters for both isotherm models. On the other hand, Genetic Algorithm and Simulated Annealing, sometimes generated unfeasible parameters. The Langmuir and Freundlich isotherm models were compared against an Artificial Neural Network, which has the ability to learn unmodeled phenomena not considered by the previous models. Thus, an Artificial Neural Network has the best prediction capabilities, although it lacks the physical interpretation the isotherm models have.

Apparent permeability prediction of organic shale with generalized lattice Boltzmann model considering surface diffusion effect

Gas flow in shale is associated with both organic matter (OM) and inorganic matter (IOM) which contain nano-pores ranging in size from a few to hundreds of nano-meters. In addition to the non-continuum effect which leads to an apparent permeability of gas higher than the intrinsic permeability, the surface diffusion of adsorbed gas in organic pores also can influence the apparent permeability through its own transport mechanism. In this study, a generalized lattice Boltzmann model (GLBM) is employed for gas flow through the reconstructed shale matrix consisting of OM and IOM. The Expectation–Maximization (EM) algorithm is used to assign the pore size distribution to each component, and the dusty gas model (DGM) and generalized Maxwell–Stefan model (GMS) are adopted to calculate the apparent permeability accounting for multiple transport mechanisms including viscous flow, Knudsen diffusion and surface diffusion. Effects of pore radius and pressure on permeability of both IOM and OM as well as effects of Langmuir parameters on OM are investigated. The effect of total organic content and distribution on the apparent permeability of the reconstructed shale matrix at different surface diffusivity is also studied. It is found that the influence of pore size and pressure on the apparent permeability of organic matter is affected by the surface diffusion of adsorbed gas. Moreover, surface diffusion plays a significant role in determining apparent permeability and the velocity distribution of shale matrix.

Removal of Cr (III) Ions from Wastewater using Sawdust and Rice Husk Biochar Pyrolyzed at Low Temperature

Sorption capacity of two different biochar (saw dust and rice straw) was evaluated in the recovery of chromium from wastewater. The optimum pH was 5-7 for recovery of Cr(III). Optimum yield was received after 1 hour contacting time with an adsorbent dose of 1 g/L and initial concentration was ∼20 mg/L. Cr(III) ions were transported to biochar surface through adsorption and intra-particle diffusion process. Langmuir and Freundlich kinetic parameters indicated that the affinity of the sorbent towards the uptake of Cr(III) ions and adsorptions were favorable. According to FTIR analysis of Cr(III) ions bound to active sites either electrostatic attraction or complexation mechanism. These results indicated that carbonyl, hydroxyl, amine and halides are the main adsorption sites in saw dust and rice straw biochar and these functional groups complexes with Cr(III) ions in the aqueous solution and changed the chemical environment of the functional groups in the biochar.

Adsorption of elemental mercury vapors from synthetic exhaust combustion gas onto HGR carbon

ABSTRACTAn activated carbon commercially available named HGR, produced by Calgon-Carbon Group, was used to adsorbe metallic mercury. The work is part of a wider research activity by the same group focused on the removal of metallic and divalent mercury from combustion flue gas. With respect to previously published papers, this one is aimed at studying in depth thermodynamic equilibria of metallic mercury adsorption onto a commercial activated carbon. The innovativeness lies in the wider operative conditions explored (temperature and mercury concentrations) and in the evaluation of kinetic and thermodynamic data for a commercially available adsorbing material. In detail, experimental runs were carried out on a laboratory-scale plant, in which Hg° vapors were supplied in a nitrogen gas stream at different temperature and mercury concentration. The gas phase was flowed through a fixed bed of adsorbent material. Adsorbate loading curves for different Hg° concentrations together with adsorption isotherms were achieved as a function of temperature (120, 150, 200°C) and Hg° concentrations (1.0−7.0 mg/m3). Experimental runs demonstrated satisfying results of the adsorption process, while Langmuir parameters were evaluated with gas–solid equilibrium data. Especially, they confirmed that adsorption capacity is a favored process in case of lower temperature and they showed that the adsorption heat was –20 kJ/mol. Furthermore, a numerical integration of differential equations that model the adsorption process was proposed. Scanning electron microscopy (SEM) investigation was an useful tool to investigate about fresh and saturated carbon areas. The comparison between them allowed identification of surface sites where mercury is adsorbed; these spots correspond to carbon areas where sulfur concentration is greater.Implications: Mercury compounds can cause severe harm to human health and to the ecosystem. There are a lot of sources that emit mercury species to the atmosphere; the main ones are exhaust gases from coal combustion and municipal solid waste incineration. Furthermore, certain CO2 capture processes, particularly oxyfuel combustion in a pulverized fuel coal-fired power station, produce a raw CO2 product containing several contaminants, mainly water vapor, oxygen, and nitrogen but also mercury, that have to be almost completely removed; otherwise these would represent a strong drawback to the success of the process.

Efficient removal of Cr(VI) by magnetically separable CoFe2O4/activated carbon composite

Owing to the unique microporous structure and high specific surface area, activated carbon (AC) could act as a good carrier for functional materials. In this paper, CoFe2O4/AC composite was prepared by a facile hydrothermal method for the adsorption of Cr(VI) in wastewater. The results indicated that CoFe2O4 nanoparticles embedded in the AC pores decreased the carbon surface area. However, The Cr(VI) adsorption capacity of CoFe2O4/AC was more effective than the initial AC. The magnetic properties of CoFe2O4/AC indicated it could be separated and retrieved easily by an outer magnet after Cr(VI) adsorption. The effects of solution pH, temperature and initial Cr (VI) concentration on the Cr(VI) adsorption of AC and CoFe2O4/AC were investigated. The Cr(VI) adsorption was pH dependent and found to be maximum at pH = 2.0. It was effective Cr(VI) adsorption with increasing temperatures. The standard free energy (ΔG), enthalpy change (ΔH) and entropy change (ΔS) were evaluated. The kinetic parameters of Langmuir and Freundlich isothermal equation were analyzed, and the Freundlich kinetic model was feasible to describe the Cr(VI) adsorption process in CoFe2O4/AC composite. According to these results, it was efficient removal of Cr(VI) with CoFe2O4/AC composite and magnetically separable easily by an outer magnet after Cr(VI) adsorption.

A fully coupled multiscale shale deformation-gas transport model for the evaluation of shale gas extraction

Horizontal drilling and hydraulic fracturing are two enabling technologies to create a shale gas reservoir. For the created reservoir scale, we define shale blocks between hydraulic fractures as matrixes. In the matrix scale, flow processes are defined in the components of inorganic minerals and kerogens, respectively. Under this framework, a set of partial differential equations are derived to define various flow and deformation processes: (1) mechanical equilibrium equation that defines the shale deformation; (2) gas flow in the kerogen system of matrix; (3) gas flow in the inorganic system of matrix; and (4) gas flow in the hydraulic fracture system. For each of gas flow systems, a permeability or diffusivity model is derived to define its evolution. All systems are fully coupled through these permeability models and mass exchanges between different systems. The fully couple PDE system was solved by using COMSOL, a popular PDE solver. The model was verified against gas production data from the Marcellus Shale and the Barnett Shale, respectively. The verified model was applied to investigate the impact of adsorption parameters, flow regimes (Knudsen number), initial permeability of the inorganic matrix, and the effective stress variations on the gas production. Model results show that the Langmuir parameters affect both the cumulative gas production and the gas extraction processes; that the impact of flow regimes is closely related to the initial permeability of the inorganic matrix; and that the impact of effective stress variations on the permeability of hydraulic fractures is more significant than that on the matrix system.

Sorption of copper(II) from synthetic oil sands process-affected water (OSPW) by pine sawdust biochars: effects of pyrolysis temperature and steam activation

Remediate metal contamination is a fundamental step prior to reclaim oil sands tailing ponds, and copper (Cu(II)) is the most abundant metal in the tailings water or oil sands process-affected water (OSPW). Biochars produced at four pyrolysis conditions were evaluated for sorption of Cu(II) in synthetic OSPW to explore different biochar potentials in removing Cu(II) from the contaminated water. Pine sawdust biochars pyrolyzed at 300 and 550 °C with and without steam activation were investigated by batch sorption experiments. Isotherm and kinetic studies were conducted to compare the sorption capacities of the four biochars and to examine potential mechanisms involved. For all the biochars, Langmuir and pseudo-second order models were the best-fit for isotherm and kinetic studies, respectively. According to the Langmuir parameters, the maximum adsorption capacities of the biochars produced at 550 °C were around 2.5 mg Cu(II) g−1, which were 30-folds higher than those produced at 300 °C. However, steam activation did not cause any significant difference in the biochars’ sorption performance. The kinetic study suggested that chemisorption involving valence forces was the limiting factor of the sorption. In addition, ion exchange and precipitation were likely the primary mechanisms for Cu(II) sorption which outweigh complexation with functional groups on the biochars’ surface. Pine sawdust biochar produced at 550 °C without steam activation could be utilized as a sustainable and cost-effective material to remove Cu(II) from the OSPW.

Performance of an Industrial Pulsed Disc-and-Doughnut Extraction Column

ABSTRACTAxial-dispersion and plug-flow models have been used to describe the solvent extraction performance of a 18 m high and 4 m diameter industrial pulsed disc-and-doughnut column. Uranium extraction phase-equilibrium data were fitted with the Langmuir model. Using the industrial column dimensions, operational parameters, physical properties, and the Langmuir parameters, the axial-dispersion model was shown to predict the organic-phase outlet concentration and the aqueous-phase outlet concentration, respectively, while the plug-flow model exhibited a poorer predictive ability.,