Shape Of Isotherms Research Articles

Adsorption properties of an activated carbon for 18 cytokines and HMGB1 from inflammatory model plasma

The ability of an activated carbon (AC) to adsorb 18 different cytokines with molecular weights ranging from 8kDa to 70kDa and high mobility group box-1 (HMGB1) from inflammatory model plasma at 310K and the mechanisms of adsorption were examined. Porosity analysis using N2 gas adsorption at 77K showed that the AC had micropores with diameters of 1–2nm and mesopores with diameters of 5–20nm. All 18 cytokines and HMGB1 were adsorbed on the AC; however, the shapes of the adsorption isotherms changed depending on the molecular weight. The adsorption isotherms for molecules of 8–10kDa, 10–20kDa, 20–30kDa, and higher molecular weights were classified as H-2, L-3, S-3, and S-1 types, respectively. These results suggested that the adsorption mechanism for the cytokines and HMGB1 in the mesopores and on the surface of the AC differed as a function of the molecular weight. On the basis of these results, it can be concluded that AC should be efficient for cytokine adsorption.

Study of interactions organic polluant/clay Anionic for environmental protection

Because of the increaseduse of pesticides in order to satisfy the economic needsin the agriculture production which is more and intensive. Many studies are done on the consequence of these pesticides on the soil and their pollution treatment [1]. The interest of the double lamellar hydroxides (HDL) in this field consist first of all in their exchange properties which offer the caught of the pollutants; on the other hand,in their use as a model of soil to the comprehension the pollution phenomenon . The present work deals with how to catch. The pesticide Methomylwithin the phase Mg 1_x Al 8 (OH 2 )[X n H 2 o]. The isothermmodelisation absorption by Freundlich equation, completed RX and IR analyses permit to precise the interaction mechanism[4]. The isotherm shape varies depending on the intercalary nature. To move from type S to the type L (Giles and al classification) with in the some isotherm is attributed to the interaction first, of the surface then with the whole solid. The type S suggests the interactions between the Methomyl molecules are more important.

Experimental Study and Modelling of Moisture Sorption Isotherms of Salted Largehead Hairtail (<i>Trichiurus lepturus</i>) at 25 and 35°C

The moisture sorption characteristics of salted largehead hairtail (Trichiurus lepturus) were investigated within the limits of water activity (0.11-0.98) at 25 and 35°C using a self-made instrument for the measurement of the equilibrium moisture content according to the static gravimetric method. The shape of the sorption isotherms was sigmoidal. The moisture sorption isotherms exhibited significant hysteresis. The hysteresis of salted fish may be due to the salt permeating into the body of the fish as a result of desorption and adsorption processes. Seventeen mathematical models were fit to the experimental data for the equilibrium moisture content at different water activity levels. The Ferro-Fontan equation provided the best fit for the experimental data of the equilibrium moisture content among the 17 models assessed for the sorption isotherms at 25 and 35°C. The net isosteric heats of sorption decreased gradually with increases in moisture content. The isosteric heats of sorption ranged from 44.59 kJ/mol to 45.61 kJ/mol between the moisture contents of 22.22% and 43.25% for salted largehead hairtail.

Water Adsorption and Desorption of Upgraded Brown Coal. Part 1: Isotherms of Adsorption and Desorption

Isotherms of water adsorption and desorption of upgraded brown coal (UBC) were compared to those of its feedstock coals, dried and not dried. The shape of isotherms showed that UBC was exposed to an irreversible collapse of capillaries by losing its original water, as was dried feedstock coal. By analyzing isotherms from the viewpoint of heat of adsorption and heat of wetting, the affinity of UBC to its adsorbed moisture was found to be smaller than that of its dried feedstock coal. This may be caused by the oil adsorbed onto its surface during slurry dewatering of the UBC process. The heat of wetting of UBC was smaller than those of its feedstock coals, which were dried. As far as UBC has the equilibrium moisture under normal ambient conditions, the risk of hot pile because of heat of wetting seems to be reduced.

Adsorption of pentane isomers on metal-organic frameworks Cu-BTC and Fe-BTC

Adsorption isotherms of n-pentane, isopentane and cyclopentane on Cu-BTC and Fe-BTC metal-organic frameworks, measured in a temperature range from 273 to 333K, have been examined. For correlations, adsorption of nitrogen at 77K and argon at 87K has been studied as well. The analysis of adsorption isotherms was based on the calculation of differential distributions of the amount adsorbed with respect to the adsorption potential. It appears that the filling of Cu-BTC micropores with nitrogen occurs in two steps due to specific interaction of nitrogen molecules with open metal sites. In contrast to nitrogen, the filling of Cu-BTC micropores with argon takes place in one step. The micropores of Fe-BTC are filled with nitrogen and argon gradually in two featureless stages indicating the unordered porous structure. Adsorption isotherms of n-pentane, isopentane and cyclopentane display especially at 273 and 293K a rectangular course with a long vertical part. This shape of C5 hydrocarbon isotherms on Cu-BTC is consistent with the shape of argon isotherms since the interactions with saturated hydrocarbons are nonspecific and thus the pores of Cu-BTC are filled in one step. The isotherms of C5 hydrocarbons on Fe-BTC show one saturation step being less sharp than in the case of Cu-BTC. Calculated isosteric adsorption heats suggest that the energy of lateral interactions between adsorbed molecules dominates the gas–solid energy heterogeneity. This domination is especially pronounced for cyclopentane adsorbed on Cu-BTC. In the case of Fe-BTC, almost constant isosteric adsorption heats show that the variations of the gas–solid interaction energy are compensated by the energy of lateral interactions.

First international inter-laboratory comparison of high-pressure CH4, CO2 and C2H6 sorption isotherms on carbonaceous shales

An inter-laboratory study of high-pressure gas sorption measurements on two carbonaceous shales has been conducted in order to assess the reproducibility of the sorption isotherms and identify possible sources of error. The measurements were carried out by seven international research laboratories using either in-house or commercial sorption equipment (manometric and gravimetric methods). Excess sorption isotherms for methane, carbon dioxide and ethane were measured at 65°C and at pressures up to 25MPa on two organic-rich shales in the dry state. The samples used in this study were taken from immature Posidonia shale (Germany) and over-mature Upper Chokier Formation (Belgium). Their total organic carbon (TOC) contents were 15.1% and 4.4% , respectively, and their vitrinite reflectance (VRr) values 0.5% and 2.0%.The objective of this study was to assess the reproducibility of sorption isotherms among laboratories each following their own measurement and data reduction procedures. All labs were asked to follow a predefined sample drying procedure prior to measurement in order to minimize any effects related to moisture. The reproducibility of the methane excess sorption isotherms was better for the high-maturity shale (within 0.02–0.03mmol/g) than for the low-maturity sample (up to 0.1mmol/g), similar to observations in earlier inter-laboratory studies on coals. The reproducibility for CO2 and C2H6 sorption isotherms was satisfactory at pressures below 5MPa, however, the results deviate considerably at higher pressures. Anomalies in the shape of the excess sorption isotherms were observed for CO2 and C2H6 and these are explained as being due to high sensitivity of gas density to temperature and pressure close to the critical point as well as from a limited measurement accuracy and possibly uncertainty in the equation of state (EoS).The low sorption capacity of carbonaceous shales (as compared to coals and activated carbons) sets very high demands on the accuracy of pressure and temperature measurement and precise temperature control. Furthermore, the sample treatment, measurement and data reduction procedures must be optimized in order to achieve satisfactory inter-laboratory consistency and accuracy. Systematic errors must be minimized first by calibrating the pressure and temperature sensors to high-quality standards. Blank sorption measurements with a non-sorbing sample (e.g. stainless steel) can be used to identify and quantitatively account for measuring artifacts resulting from unknown residual systematic errors or from the limited accuracy of the EoS. The possible sources of error causing the observed discrepancies are discussed.

Modifying Effect of Betulinol on Carbon Sorbents Produced from Betula birch Wood

A lack of high-quality carbon adsorbents (CA) with a uniform microporous structure is the main impediment to the development of new and the improvement of existing adsorption methods for purifying and separating gases. The sorbent structure, i.e., the size, volume, and ratio of principal pore types, is determined by the nature of the precursor and its processing into activated carbon. As a rule, the porosity of carbonized carbons from wood and plant material is known to be disorganized. Structure formation in a particular direction is difficult to regulate accurately. The sizes and distribution of pores in CA could possibly be controlled by modifying the porosity of finished activated carbon with an organic binder and/or a pore-former or by applying a layer of organic polymer or hydrocarbon thermal decomposition products to the carbon substrate [1]. The goal of the present work was to study the effect of modifying the porous structure of previously carbonized Betula birch wood with betulinol and subsequent activation with KOH on the properties of the produced CA. It was found that thermochemical activation (800°C, 1 h) of previously carbonized (300–800°C) B. birch wood in the presence of KOH promoted the formation and development of micropores. The resulting carbon materials were distinctly porous and absorbed a broad spectrum of chemicals (benzene, hexane, CCl4, H2O, etc.). The carbonized (400°C) B. birch wood sample that was activated by KOH (3:1) (CBW-400/KOH) had the highest specific surface area (SBET 1980 m 2/g) and total pore volume (0.83 cm3/g) [2]. As the carbonization temperature was raised from 600 to 800°C, the KOH-activated CA were highly selective for the separation of a model mixture of H2(He) and CH4. Their separation coefficients (Ks) were 3.0–3.8, were used as criteria of the separating capability, and were estimated by chromatography. This represented a high degree of separation for He–CH4 [3]. The possibility of improving the Ks values by regulating the reactivity of the B. birch precursors that were carbonized at 500–800°C was studied. Existing pores were modified by the natural product betulinol (25 mass%) and then activated by KOH. Betulinol (betulin) is the pentacyclic lupane triterpene alcohol C30H50O2 with MW 442.7. It was isolated by extraction from B. birch bark. A coating of pyrolyzed carbon will form on the external surface of the carbon if the organic modifier is used under conditions where it is selectively decomposed (450°C). The carbon composite formed at this point is activated by KOH, which is effective on both components. As a result, modified CA with a controlled capability for selective adsorption and separation of H2(He)–CH4 mixtures were produced at 800°C. The effect of the organic modifier on the CA porous structure was studied using CBW (700°C) activated by KOH (CBW-700/KOH) as an example. Figure 1 shows the N2 adsorption isotherms at 77 K under standardized conditions (Fig. 1). The N2 adsorption isotherms for unmodified CBW-700/KOH (Fig. 1, 3) and for CA from pure betulinol (Fig. 1, 2), which was prepared for comparison under analogous KOH activation conditions, were characteristic of microporous materials. The shape of isotherm 1 was indicative of further pore development throughout the whole volume of CBW-700 because of modification with betulinol and subsequent activation by KOH. The fraction of micropores increased because pieces of pyrolyzed material were located near the entrances to larger pores. This shifted the pore-size distribution to a predominant size up to 1.8 nm (~90%) and gave a more uniform microtexture that was more favorable for He-CH4 separation. The Ks values of the modified CA from B. birch wood (Ks = 3.87–4.11) exceeded those of CA that were prepared analogously but were unmodified (Ks = 3.0–3.8) [3]. Table 1 shows that the modifying action of betulinol and subsequent activation by KOH were manifested best at carbonization temperatures of 600–800°C. Modified sample CBW-700 had the highest Ks value (4.11) for H2(He)–CH4 under controlled KOH activation conditions.

Discrimination of rival isotherm equations for aqueous contaminant removal systems

Two different model selection indices, the Akaike information criterion (AIC) and the coefficient of determination (<TEX>$R^2$</TEX>), are used to discriminate competing isotherm equations for aqueous pollutant removal systems. The former takes into account model accuracy and complexity while the latter considers model accuracy only. The five types of isotherm shape in the Brunauer-Deming-Deming-Teller (BDDT) classification are considered. Sorption equilibrium data taken from the literature were correlated using isotherm equations with fitting parameters ranging from two to five. For the isotherm shapes of types I (favorable) and III (unfavorable), the AIC favors two-parameter equations which can easily track these simple isotherm shapes with high accuracy. The <TEX>$R^2$</TEX> indicator by contrast recommends isotherm equations with more than two parameters which can provide marginally better fits than two-parameter equations. To correlate the more intricate shapes of types II (multilayer), IV (two-plateau) and V (S-shaped) isotherms, both indices favor isotherm equations with more than two parameters.

Measurements of water vapour sorption isotherms for RD silica gel, AQSOA-Z01, AQSOA-Z02, AQSOA-Z05 and CECA zeolite 3A

The water vapour adsorption isotherms of RD silica gel, AQSOA-Z01, AQSOA-Z02, AQSOA-Z05 and CECA zeolite 3A are measured for temperatures between 20°C and 160°C and vapour partial pressures between 1 and 500mbar. The measurements were fit to a theoretical isotherm function and for some materials the RMS deviation was less than 5%. Since others had a poorer theoretical fit, all data was also fit to spline functions for use in numerical simulations. The variation of isosteric heats of adsorption as a function of uptake, calculated using a least squares fitting approach, are compared over a range of uptake values for each adsorbent. The heats of adsorption were between 1 and 1.6 times the heat of vaporisation for uptake values above 10% of the maximum uptake for each adsorbent. The AQSOA adsorbents display Type IV isotherm shapes and the silica gel and 3A zeolite display Type I shapes. The sorption hysteresis is investigated for the AQSOA adsorbents at a selected temperature. These adsorbents displayed a small degree of hysteresis with an H1 type behaviour.

The Effects of Concentrations of Zirconium(IV) Sulphate and Sulphuric Acid on Sorption of Zirconium(IV) and Hafnium(IV) on Purolite S-957 Resin. Adsorption Isotherms of Zirconium(IV) and Hafnium(IV) Ions

The optimal conditions of separation of zirconium(IV) from hafnium(IV) on Purolite S-957 ion-exchange resin in their sulfate aqueous solutions using a static method has been determined to be 0,07 M Zr(SO4)2 (containing 2% Hf) in 0,5 M H2SO4. Higher Zr(IV) concentration causes a lowering of the Zr/Hf separation efficiency due to the oligocondensation of mononuclear Zr(IV) and Hf(IV) ions resulting in the formation of Zr(IV) or mixed Zr(IV)-Hf(IV) oligohydroxo-sulfato ions, which is not prevented by the parallel increase of acidity of the solution. The same effect can be observed when analyzing the shapes of adsorption isotherms, which are similar for both Zr(IV) and Hf(IV).

Adsorption characteristics of water vapor on ferroaluminophosphate for desalination cycle

The adsorption characteristics of microporous ferroaluminophosphate adsorbent (FAM-Z01, Mitsubishi Plastics) are evaluated for possible application in adsorption desalination and cooling (AD) cycles. A particular interest is its water vapor uptake behavior at assorted adsorption temperatures and pressures whilst comparing them to the commercial silica gels of AD plants. The surface characteristics are first carried out using N2 gas adsorption followed by the water vapor uptake analysis for temperature ranging from 20°C to 80°C. We propose a hybrid isotherm model, composing of the Henry and the Sips isotherms, which can be integrated to satisfactorily fit the experimental data of water adsorption on the FAM-Z01. The hybrid model is selected to fit the unusual isotherm shapes, that is, a low adsorption in the initial section and followed by a rapid vapor uptake leading to a likely micropore volume filling by hydrogen bonding and cooperative interaction in micropores. It is shown that the equilibrium adsorption capacity of FAM-Z01 can be up to 5 folds higher than that of conventional silica gels. Owing to the quantum increase in the adsorbate uptake, the FAM-Z01 has the potential to significantly reduce the footprint of an existing AD plant for the same output capacity.

Mechanism of adsorption of different humic acid fractions on mesoporous activated carbons with basic surface characteristics

The effects of the humic acid (HA) nature and the activated carbon (AC) surface chemistry on the effectiveness of HA removal were investigated. Brown (BHA) and gray (GHA) humic acid fractions of different structure and physicochemical properties were tested in the adsorption process using mesoporous ACs. The modification of chemical structure and surface properties of AC was achieved by ammonization (AC/N) and hydrogen treatment (AC/H). Both approaches led to a decrease in the oxygen content followed by an increase in the carbon basicity, maintaining the porous texture of AC nearly unaltered. Over twice higher removal degree of BHA and GHA was observed for the modified ACs. The kinetics of adsorption of HA fractions have been discussed using the pseudo-second-order model and the intraparticle diffusion model. All ACs showed a higher adsorption capacity toward BHA compared to GHA, which is mainly attributed to the lower molecular weight of BHA. The shape of the equilibrium isotherms indicates a strong competition between water and HA molecules for adsorption sites of the carbon surface.

Structural, textural and adsorption characteristics of bentonite-based composite

An application of coatings composed of mixed (hydr)oxides over bentonite particles in aqueous suspension, in narrow range of pH, has been proven as a useful method for obtaining bentonite based composite with a developed, specific surface area and pronounced adsorption features toward cationic pollutants. This paper deals with detailed characterization of structure as well as textural and adsorption properties of bentonite based composite. The structure of the composite was examined by using XRD technique providing results that confirm changes in orientation of layered quasi-crystalline particles of montmorillonite, which is the most common component of bentonite clay. Surface area and pore volumes were determined by N2 adsorption at −196°C using BET, t-plot, αs-plot, Dubinin Radushkevich and Dollimore–Heal method. The results have revealed that the specific surface area for composite is about two times higher than for starting bentonite. Moreover, modification of bentonite leads to significant changes in the meso- and microporosity. Adsorption properties of the composite were studied by analyzing the adsorption of dye methylene blue which was used in this study as a model of cationic pollutant in water. The most prominent role in the mechanism of dye molecules retention on the surface, interlayers and in the pores of the adsorbent is ascribed to establishing of electrostatic, van der Waals and hydrogen bonds. The shape of adsorption isotherm indicates that methylene blue can be adsorbed onto composite in more than one layer.

Shale gas potential of the major marine shale formations in the Upper Yangtze Platform, South China, Part II: Methane sorption capacity

The marine black shale formations on the Upper Yangtze Platform (UYP), South China are exploration targets for shale gas. Here, we report on the methane sorption capacity of thermally overmature samples from the Lower Silurian and Lower Cambrian black shale intervals in the UYP (UYP-samples). Two immature shale samples from the Middle Cambrian formation in the Georgina Basin, North Australia (AU samples) were also tested to investigate the effect of thermal maturity on sorption isotherms. Excess sorption isotherms were performed over a pressure range of 0–25MPa at 46°C. The effects of TOC content, thermal maturity, clay minerals, moisture content, pore properties, particle size, temperature, and pressure on methane sorption capacity were analysed. In addition, thermovaporisation gas chromatography (Tvap-GC) was used to measure the residual gas that is stored in the samples under atmospheric pressure and temperature conditions.The results indicate that the maximum methane excess sorption of the Lower Silurian samples is between 0.045 and 0.064mmol/g rock and that of Lower Cambrian samples is between 0.036 and 0.210mmol/g rock. The Langmuir sorption capacity of the Lower Silurian samples ranges from 0.096 to 0.115mmol/g rock, whereas that of the Lower Cambrian shale ranges from 0.077 to 0.310mmol/g rock. These results are close to the sorption capacities of the Barnett (U.S.), Devonian–Mississippian (Western Canada), and Alum (Southern Scandinavia) shale samples. The shape of the sorption isotherms and methane sorption capacity vary from sample to sample. Under the measured pressure range, the isotherms of the selected immature AU Cambrian samples increase monotonously with pressure, whereas the overmature UYP samples exhibit maxima. The methane sorption capacity of the measured samples positively correlates with TOC content and exhibits a distinct linear relation. The TOC-normalised sorption capacity shows a positive correlation with thermal maturity; however, the corresponding pressure of maximum excess sorption and Langmuir pressure decrease substantially with increasing thermal maturity. The clay minerals show a positive effect on the TOC-normalised sorption capacity. The sorption capacity of clay minerals, however, should have been reduced by the moisture content. The two Lower Cambrian samples that have similar maturities were measured for porosity and pore-size distribution. The sample with a high TOC content shows a high total cumulative pore volume, surface area, total porosity and thus a higher sorption capacity than the sample with less TOC. In addition, larger-sized particles show slightly less sorption capacity than smaller-sized particles. The Tvap-GC results show that the residual gas content of core samples is evidently higher than that of the outcrop samples, which implies a remarkably negative effect of the weathering process.

Hydrostatic pressure and temperature dependence of wood moisture sorption isotherms

By expressing wood moisture content data as a function of adsorption energy, an interesting scaling capability is obtained, wherefrom the general hydrostatic pressure and temperature dependence of wood moisture content is determined. The scaling law is fully consistent with the thermodynamics of swelling. It can be used to transform room condition sorption isotherms to other temperatures and hydrostatic pressures, provided that the wood matrix is not irreversibly modified. A special procedure is suggested for the case of an irreversibly changing wood matrix, as in thermal modification and thermo-hydro-mechanical treatments. Using the present scaling theory, several fundamental aspects of wood moisture sorption are explained, such as the absence of a significant quantity of strongly bound wood moisture, the internal stress generation by sorption hysteresis in the wood cell wall, and the reason for the reversible disappearance of the sigmoid shape of the sorption isotherm at higher temperature. The results of this research may be useful (a) for transformation of known sorption data to other conditions, notably where in situ moisture measurements are difficult to perform and (b) to quantify the effects of internal stresses in the ultrastructure of the cell wall on moisture content.

The water vapor sorption mechanism and its hysteresis in wood: the water/void mixture postulate

A new method of wood moisture sorption analysis is presented using sorption isotherms of a series of mildly heat-treated specimens with varied and known elemental composition. This method allows the determination of the occupancy of accessible sorption sites in wood as a function of relative humidity h, θ(h) ≈ h, found in agreement with the literature data on the non-freezing water occupancy of hydroxyl groups for h < 0.9. Complementary sorption isotherm shape analysis identifies an empirical power law occupancy function, θ(h) = h α , α ≈ 0.73, which is close to the former two determinations in the same humidity range. The validity of widely accepted surface sorption theories for wood with a strongly bound primary layer and loosely bound secondary layers is disproven. To explain the found occupancy function, θ(h) ≈ h, a near-ideal liquid mixture of moisture and polar dynamic microvoids in the cell wall substance is postulated. The power law occupancy function is used to calculate the humidity-dependent number of sorption sites in adsorption/desorption isotherms to show that (1) the number of sorption sites from the adsorption line monotonically increases with increasing humidity—argued to represent the equilibrium number of sorption sites at each humidity, and (2) the number of sorption sites from the desorption line fails to fully return to that of the (equilibrium) adsorption line. Hysteresis is quantitatively explained as the result of non-equilibrium excess sorption sites being occupied according to the occupancy law. The relaxation of non-equilibrium excess sorption sites is satisfactorily modeled by a first-order rate equation. Applying the analysis to study mild thermal modification of moisture sorption isotherms revealed that (1) moisture contents decrease directly linear to the removed amount of sorption sites at all humidity <0.95, and (2) the absolute hysteresis is nearly unaffected as a result of counter-acting effects of the reduced number of sorption sites and reduced amount of relaxation.

Adsorption of polyethyleneimine (PEI) on hematite. Influence of magnetic field on adsorption of PEI on hematite

A research on influence of magnetic field of various inductions on adsorption of polyethyleneimine (PEI) onto hematite is presented. Properties of the adsorbent surface (Magnetic Force Microscopy images and nitrogen adsorption data) and its behaviour in a water solution (particle size distribution) are also studied. Moreover, new analytical approach is proposed to compare the shape of the isotherms (e.g. presence of plateaus) by calculating a reciprocal derivative.A proposal of adsorption mechanism that explains a multilayer character of the adsorption itself as well as shapes of adsorption isotherms is presented. Changes in the before-mentioned mechanism due to exposure to magnetic field are also explained. Study revealed that in most cases presence of magnetic field decreases an amount of PEI adsorbed and this decrease is not a linear function of magnetic field strength – the tendency is reversed for the strongest field investigated (what is consistent with literature data).

The effect of hydroxyl moieties and their oxosubstitution on bile acid association studied in floating monolayers.

Bile salt aggregates are promising candidates for drug delivery vehicles due to their unique fat-solubilizing ability. However, the toxicity of bile salts increases with improving fat-solubilizing capability and so an optimal combination of efficient solubilization and low toxicity is necessary. To improve hydrophilicity (and decrease toxicity), we substituted hydroxyl groups of several natural bile acid (BA) molecules for oxogroups and studied their intrinsic molecular association behavior. Here we present the comparative Langmuir trough study of the two-dimensional (2D) association behavior of eight natural BAs and four oxoderivatives (traditionally called keto-derivatives) floated on an aqueous subphase. The series of BAs and derivatives showed systematic changes in the shape of the compression isotherms. Two types of association could be distinguished: the first transition was assigned to the formation of dimers through H-bonding and the second to the hydrophobic aggregation of BA dimers. Hydrophobic association of BA molecules in the films is linked to the ability of forming H-bonded dimers. Both H-bond formation and hydrophobic association weakened with increasing number of hydroxyl groups, decreasing distance between hydroxyl groups, and increasing oxosubstitution. The results also show that the Langmuir trough method is extremely useful in selecting appropriate BA molecules to design drug delivery systems.

Adsorption features of Cu(II), Pb(II), and Zn(II) by an ordinary chernozem from nitrate, chloride, acetate, and sulfate solutions

The effect of Cl−,SO42−, CH3COO−, and NO3− anions on the adsorption of copper, lead, and zinc by an ordinary chernozem has been studied. The effect of the anions on the adsorption of Cu2+, Pb2+, Zn2+ ions is significant but uncertain. It has been shown that the attendant anions affect the shape of the adsorption isotherms, which are described by the Langmuir, Freundlich, or Henri equations. The constants of the adsorption from a nitrate solution calculated from the Langmuir equation (KL) decrease in the following order: Cu2+ > Pb2+ >> Zn2+. The values of the maximum adsorption (Cmax) decrease in the following order: Cu2+ ≥ Zn2+ > Pb2+ for acetate solutions and in the series Pb2+ > Zn2+ ≥ Cu2+ for nitrate solutions. The values of the Henry constants (KH) calculated for the adsorption of the same cations from chloride solutions decrease in the same order as the values of KL. The CH3COO− anion has the highest effect on the constant values. The NO3− and Cl− anions “switch their places” depending on the attendant cation, but their effect is always lower than that of the acetate anion. The values of Cmax for copper and zinc are most affected by the CH3COO− anion, and the adsorption of zinc is most affected by the Cl− and NO3− anions. The assessment of the mobility of the adsorbed cations from the extraction with ammonium acetate (pH 4.8) has shown that the content of the desorbed metals is always lower than the content of the adsorbed cations and varies from 0.025 to 83%. According to their mobility, the adsorbed metals form the following order: Zn2+ > Pb2+ > Cu2+. The effect of the attendant anions on the extractability of the adsorbed cations decreases in the following order: chlorides > sulfates > acetates > nitrates.

CO2-ECBM and CO2 Sequestration in Polish Coal Seam – Experimental Study

ABSTRACT Purpose Methane recovery is interesting not only because of its clean combustion; it is also beneficial for the environment because of the reduction of the amount of methane emitted into the atmosphere, which is important because of methane’s significant impact on the greenhouse effect. However, desorption of methane is a slow process, significantly dependent on the coalification of coal, its porosity and petrographic composition. Injection of carbon dioxide into the coal bed under sufficient pressure might be a factor in stimulating the efficiency of this process, as – because of preferential sorption – carbon dioxide displaces methane molecules previously absorbed in the coal matrix. Methods The measurements were made for Polish low-rank coal used for the analysis of methane recovery from Polish coal mines. Coal samples were collected from sites used for geological, sorption and petrographic research, as well as for the assessment of the reservoir’s genetic origin CH4 content. Experimental studies of sorption were performed with the use of the volumetric method at a lower and higher gas pressure. Results The methane isothermes show more than double the reduction of adsorption along with increasing temperature. The most significant changes of sorption capacity due to temperature variations can be seen when observing the difference in the course of the hysteresis of sorption/desorption of the gas as a function of temperature. In cases where there is a temperature of 323 K, a temperature hysteresis loop might indicate larger quantities of methane trapped in the porous structure of coal. In cases of carbon dioxide as sorbate, a similar shape of sorption isotherms occurred at both temperatures, while the temperature increase caused approximately double the reduction of sorption capacity. Also the isotherm’s shape is similar for both temperatures of measurement, indicating no effect of temperature on the amount of gas within the structure of the tested coal. High-pressure isotherms of CO2 and CH4 are confirmed in the literature, proving that carbon dioxide is the gas that allows the best penetration of the internal structure of bituminous coal. The critical temperature of CO2 (304.5 K) is so high, that sorption measurements can be performed at room temperatures (293, 298 K), where activated diffusion is relatively fast. Practical implications Understanding the sorption of gases is the primary issue, related to the exploitation of coal seams, when explaining the mechanism of gas deposition in coal seams and its relationship with outbursts of rocks and gases in mines. Originality/value The results indicate successful sorption of carbon dioxide in each experiment. This provides the rationale to study the application of the coal tested to obtain methane genetic origin genetic methane with the use of the CO2 injection.