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The method of isotherm simulation by approximating mathematical expressions that are valid for a small experimental section of the isotherm over the entire range of equilibrium concentrations is an important and useful tool in adsorption practice. Nine adsorption equilibrium systems of activated carbon (AC)–derivatives of aniline and phenol were examined. The adsorbent used was activated carbon obtained from fruit pits. The results of isothermal adsorption of aromatic substances with relatively small molecules on a microporous carbon adsorbent indicate the simultaneous adequacy of the Freundlich and Langmuir models to the experimental data in moderate concentration ranges ((0.1–100)n mg/dm3, where n = 1, 2, 3, 4, 5). Thus, the results of adsorption from the aqueous phase do not demonstrate the energy differences of the AC surface that are incorporated into the theoretical classical model isotherms. The isotherm reflects the adsorption process on both homogeneous and heterogeneous surfaces simultaneously. This may be due to the displacement nature of adsorption from the aqueous phase, where initial surface screening by water molecules occurs during adsorbent wetting, leading to the leveling of its energetic heterogeneity. In the next stage—displacement of some water molecules by the organic adsorbate—the energetic differences of the adsorption sites are not as clearly manifested as in gas-phase adsorption. Therefore, theorizing the nature of the AC surface based on the best model simulation of experimental isotherms using classical equations becomes questionable. Three-parameter equations (Langmuir–Freundlich, Redlich–Peterson) demonstrated a finer simulation of the experiment compared to the classical two-parameter models. The study emphasizes that the mathematical description of the isotherm is a convenient method for the efficient storage and use of information about the adsorption properties of the system. It serves to compare the effectiveness of new materials with commercial analogs and to predict the performance of real purification systems under dynamic conditions. [ABSTRACT FROM AUTHOR]

Doping of metal oxide with other suitable component can enhance its structural and characteristic properties. At the end it improves its overall application performances. This study introduces the novel synthesis of Al2O3@TiFe2O4 nanocomposite via co-precipitation for Cr(VI) removal. Unlike previous studies, this unique material exhibits superior adsorption capacity and efficiency. The comparative analysis with existing adsorbents underscores its potential for industrial effluent treatment. The nanocomposite’s recyclability and minimal efficiency loss over multiple cycles highlight its sustainability for wastewater treatment. Overall, this research fills existing gaps by presenting an advanced, environmentally friendly adsorbent, significantly enhancing the field of wastewater treatment and environmental remediation. The nanocomposite was characterized and used to study Cr(VI) adsorption characteristics. Amount, contact time, pH, and Cr(VI) concentration were found to influence the adsorption characteristics of the nanomaterial. The operating conditions of an adsorbent Al2O3@TiFe2O4 are optimized utilizing the analysis of the adsorption kinetic data. As shown by the R2 responses, which were close to unity, the adsorption behaviour of the nanomaterial is in excellent harmony with the linearized Langmuir isotherm with a maximum capacity of 312.52 mg/g. Additionally, Al2O3@TiFe2O4 active sites were more observed to be favorable for Cr(VI) ions at all experimental temperatures range, according to calculations of monolayer adsorption capacities using the Langmuir equation. The value of n was 0.40, 0.42, and 0.43, respectively 25, 35, and 45 °C. The adsorbent shows an adsorption capacity of 93 % with the RSD less than 2 %.

Powdered rock phosphate may have the potential of soluble phosphate sorption because its particles are small. Phosphorus (P) sorption-desorption behavior and sorption kinetics were studied on four different fine powdered phosphate rocks (PPR), from Esfordi, Chadormalu and Yasuj mines. Sorption isotherms were evaluated by equilibrating 1 g PPR with 20 ml CaCl2- 0.01 M containing 10, 50, 100, 200, 400, 600, 800 and 1000 mg P L-1, as KH2PO4 in duplicates. Consequently, P release was studied by equilibrating the samples with 20 ml 0.01 M CaCl2. FTIR analysis was conducted on the blank samples, and those equilibrated with 1000 mg P L-1. Kinetics of phosphate sorption on PPRs was evaluated with two initial P concentrations (50 and 100 mg P L-1) and contact times of 1, 2, 4, 8, 16, 24, and 48 h with 0.01 M CaCl2 as the background solution in duplicate. Results showed that the least P sorption was around 150, and the maximum P sorption was 12000 mg kg-1 PPRs. The highest P release was around 15% of sorbed P, and releasable P was reduced to 2-3% of sorbrd P with the increase of P sorption. P sorption data showed a good fit with Freundlich and Langmuir equations. The kinetic of P sorption showed a fast reaction that rapidly diminished soluble P. Results of the present study suggest that PPRs could reduce soluble P, which is better to be considered at different usage of PPR such as incorporation with organic wastes and its biosolubilization. [ABSTRACT FROM AUTHOR]

The paper studies the sorption properties of iron(III) hydroxide obtained by precipitation from a solution of iron(II) sulfate in relation to nickel ions. The study was carried out at room temperature on a model solution of sodium sulfate (400 mg/L), which imitated polluted natural and waste water. It is shown that the removal of nickel ions from a model solution by a precipitate of freshly precipitated iron(III) hydroxide at pH 7 and 8 is described with satisfactory accuracy by the classical Freundlich, Langmuir, and Dubinin–Radushkevich adsorption isotherms. The values of free energy of adsorption calculated using this last equation do not exceed 8 kJ/mol, which indicates the physical nature of adsorption and excludes ion-exchange interaction of nickel ions with iron(III) hydroxide. The most complete removal of nickel ions from solution occurs during sorption with iron(III) hydroxide at pH 8. The sorption capacity of iron(III) hydroxide for nickel ions, both at pH 7 and at pH 8, is almost an order of magnitude greater than the similar value for many mineral, carbon, and coal sorbents. A comparison of the efficiency of sorption purification of a model solution using iron(III) hydroxide precipitates obtained by precipitation from solutions of iron(II) sulfate and iron(III) chloride showed that the deepest removal of nickel ions is achieved using iron(III) hydroxide precipitates obtained from a FeCl3 solution. [ABSTRACT FROM AUTHOR]

The permeability coefficient of coal seams is a key parameter that judges the difficulty of gas flow in coal seams. In the current calculation formula for the permeability coefficient of coal seams, the coefficient of the nonlinear partial differential equation with variable pressure is assumed to be a constant, which leads to significant errors in the theoretical derivation results and results in significant deviations in the permeability coefficient measured on site. To solve the inaccurate determination problem of the coal seam permeability coefficient, this paper derived the process of using the radial flow rate method to test the coal seam permeability coefficient, and pointed out the problems of this method during the derivation process. Based on the Langmuir's gas content and Darcy's law, a dimensionless model was established, and the model solution results were inverted and fitted. A new calculation formula for the coal seam permeability coefficient was obtained, which was verified by on-site drilling data. The current testing method for coal seam permeability coefficient was revised, and an accurate and reliable new method for calculating the coal seam permeability coefficient was proposed. The results indicate that using a parabolic equation to represent the coal seam gas content and treating variable p1.5 as a constant to derive the coal seam permeability coefficient calculation formula is equivalent to fitting the gas content into a proportional relationship with the square of pressure. There are theoretical problems and significant errors in actual calculations. Using the Langmuir dimensionless model to calculate Y' for inversion fitting can solve the shortcomings of current calculation methods. When the product of the adsorption constant b and the original gas pressure p0 (the dimensionless original gas pressure) is different, the function curve of the dimensionless gas emission velocity Y' and the dimensionless time Fo' is significantly different. Therefore, the permeability coefficient calculation formula containing the dimensionless original gas pressure was obtained. When the coal seam and drilling conditions are constant, the values of the coal seam permeability coefficient λ calculated from the gas emission volume at different times have a good reproducibility. The new on-site measurement method for the permeability coefficient of coal seams is completely the same as the current method without adding additional workload. However, the new calculating method is more accurate and reliable.

The coal bed pressure (reservoir pressure) is shown to be the pressure of the gas within the sealed borehole cavity within the bed after equilibrium has been established between the desorption of methane from the bed and its resorption on account of the pressure that develops. It is established that the Langmuir equation cannot be used to assess the gas content of the coal bed if the saturation pressure in adsorption is replaced by the bed pressure, since these concepts are fundamentally different. In fact, their physical significance is different: the saturation pressure is created by an external source and drives methane into the bed, whereas the bed pressure is created within the bed as a result of methane desorption within a sealed volume containing gas-bearing coal. The Langmuir equation may be used to describe the methane sorption by coal up to a saturation pressure of 5 MPa, since the influence of the coal's structural transformation and consequent swelling may be disregarded within that range. In addition, it is shown for a specific example that, instead of using the Langmuir equation, whose constants are determined theoretically, the isotherms of methane sorption by coal with moderate methane filling may be described by the Freundlich equation, whose constants are determined empirically. [ABSTRACT FROM AUTHOR]

Fractions of phosphorus (P) and its sorption characteristics are affected by different soil fertility (FM) technologies which ultimately affect crop growth and productivity. However, the response of P fractions and sorption characteristics to soil fertility technologies that integrate diverse amendments is still poorly understood in acidic Nitisols. A randomized complete block design was layout in an acidic Nitisol to determine fractions of P, its sorption characteristics and use efficiencies in acidic Nitisols under various FM technologies in field conditions. The use of minimum tillage + maize residue + inorganic fertilizer + goat manure (MTCrGF) had the highest impact on and significantly increased resin-Pi, NaHCO3-Pi, and maximum P sorption (Smax) by 182, 76, and 52 mg P kg−1. Moreover, NaOH-Pi and Smax concentrations were higher under conventional tillage + maize residue + inorganic fertilizer + goat manure (CTCrGF) by 216 mg P kg−1 and 49 mg P kg−1 than the control. MTCrGF and CTCrGF also had the lowest P bonding energy (0.04 L mg−1). CTCrGF had the highest P partial productivity factor (0.093 and 0.140 kg biomass kg−1 P) and P agronomic efficiency (0.080 and 0.073 kg biomass kg−1 P) during the two cropping seasons. The results demonstrate the positive influence of combining multiple P sources on soil P fractions, sorption characteristics, and use efficiencies. Notably, combining either conventional or minimum tillage with maize straw and applying integrated manure and inorganic fertilizer (MTCrGF or CTCrGF) can increase the labile P concentrations and reduce the potential depletion of the non-renewable rock phosphate and the use of inorganic phosphatic fertilizers for agricultural production.

The sorption of phosphorus by solonchaks of the dry-steppe zone in the Republic of Buryatia from water solution of KN2PO4 in the concentration from 0.25 to 5.0 mM P/L was studied under static conditions. The interaction period was 24 hours, and the soil to solution ratio was 1 : 10. The amount of adsorbed phosphorus was calculated as the difference of its content in the initial solutions and in the filtrates of soil suspensions. Based on the experimental data, we constructed isotherms of phosphorus adsorption by soil and calculated sorption parameters using the Langmuir and Freundlich equations. Typical and quasigley solonchaks were characterized by relatively high phosphorus sorption properties. The maximal adsorption capacity (Amax) varied within 23.04–42.74 mM P/kg in the humus horizons of these soils and within 16.26–30.39 mM P/kg in deeper horizons. In general, the range of Amax was 17.70–42.74 mM P/kg in all soils, except for sor solonchak, where the sorption capacity of phosphorus was low. The Langmuir adsorption constant (KL) varied in the range of 0.3–14.0 L/mM. Dark and typical solonchaks were characterized by the strongest binding of phosphorus. The Freundlich coefficient (KF) in the studied soils varied from 5.34 to 63.43 mM P/kg in the humus horizon and from 1.74 to 22.68 mM P/kg in the underlying mineral horizons. The distribution coefficient (Kd) ranged within 1.95–145.04 L/kg and was high for quasigley solonchaks and low for sor solonchaks. There was a moderate correlation between Kd and Amax (r = 0.51) and high between Kd and KL (r = 0.84, p ≤ 0.05). According to the standardized phosphorus retention (SPR) (the amount of phosphorus that should be sorbed by the soil to maintain concentration of P = 0.2 mg/kg (0.0065 mM/L) in soil solution), the studied soils were assigned to the group with weak phosphorus sorption (SPR was from 0.0723 to 3.4836 mM/kg). According to the phosphorus sorption capacity, the soils were arranged into the following sequence: quasigley solonchak > typical solonchak > dark solonchak > gley solonchak > alluvial light-humus saline soil > sor solonchak. [ABSTRACT FROM AUTHOR]

This article analyzes patterns of potassium sorption from an aqueous solution of KCl by three types of soils (lowland peaty, light chestnut, and alluvial soddy types) formed under conditions of Western Transbaikalia and by their treated analogs. Potassium sorption in soil is measured in laboratory conditions based on an experiment in which soils are balanced using a solution with different initial concentrations of KCl (0.5, 1.0, 3.0, and 5.0 mmol/L) for 24 h. The resulting potassium sorption isotherms are described by the Langmuir and Freundlich equations. Parameters of these equations indicate an inhomogeneity of the bonds of potassium ions with the solid phase of soils. The maximum potassium uptake by the studied soils varies from 53.2 to 87.8% at the initial KCl concentration of 1 mmol/L, while the coefficient of distribution (Kd) of potassium between the solid and liquid phases of the soils used in the study varies from 11.37 to 72.11 L/kg. The highest Kd value has been determined for the lowland peaty soil and the lowest value for the alluvial soddy soil. The patterns of changes in Kd of potassium are correlated with the degree of its absorption by the soil. The maximum sorption capacity of potassium by the soils varies from 54.05 to 98.04 mmol/kg in the upper humus horizons and from 35.71 to 100.0 mmol/kg in the lower horizons. The values of the KL coefficient of the Langmuir equation are slightly lower in humus horizons (0.272‒0.668 L/mmol) than in mineral horizons (0.102–1.511 L/mmol), which indicates that potassium binds more strongly in mineral horizons. The KF coefficient of the Freundlich equation varies from 9.98 to 23.51 mmol/kg in humus horizons and from 6.63 to 26.77 mmol/kg in mineral horizons. It has been established that the studied soils are characterized by different sorption activities with respect to potassium and form the following decreasing series with respect to the level of potassium absorption: lowland peaty > light chestnut > alluvial soddy soils. [ABSTRACT FROM AUTHOR]

Up to the present time, the construction of a general theory of the equilibrium adsorption is a very urgent task. In the present paper, a general phenomenological approach is developed to describe both adsorption and absorption equilibria. It was shown that under certain assumptions, the resulting equation transforms into the well-known classical Henry, Langmuir, Brunauer-Emmett-Teller equations with constants having a clear physical meaning. Thus, the constant in the Henry equation is determined by the temperature, the specific surface of the adsorbent, the size of the adsorbate molecules, the molar mass of the adsorbate and the isosteric heat of adsorption (the energy of interaction of the adsorbate molecules with the surface of the adsorbent). In the derived Brunauer-Emmett-Teller partial equation, in contrast to the classical version, a clear dependence of the equation constant on the specific physical characteristics of the adsorption system is indicated for the first time. It is determined by the concentration of adsorbate molecules in the liquid phase at the temperature under consideration, the concentration of adsorbate molecules during the formation of a dense monolayer on the surface of the adsorbent, the energy of interaction of adsorbate molecules with the surface of the adsorbent and the heat of condensation. The presented approach can serve as a basis for modeling a variety of adsorption and absorption phenomena, including adsorption on microporous adsorbents.

The size of particles determines the adsorption reaction. In this study, three different particle sizes of biochar (0.25-1 mm, 0.075-0.25 mm, <0.075 mm) were produced from rapeseed straw (SBC) and chicken manure (MBC). The biochar was mixed with high phosphorus (P) soil and low P soil and then incubated for 30 days. We conducted isothermal P sorption and desorption experiments to evaluate the effects of biochar particle size on sorption-desorption characteristics of soil P, and analyzed soil properties associated with P sorption. The results showed that P sorption capacity of SBC and MBC in the water system was highest for the smallest particle size (<0.075 mm) (SBC: 43125 mg ⋅ kg-1, MBC: 20083 mg ⋅ kg-1), followed by the intermediate particle size (0.075-0.25 mm) (SBC: 37376 mg ⋅ kg-1, MBC: 13199 mg ⋅ kg-1) and the largest particle size (0.25-1 mm) (SBC: 27749 mg ⋅ kg-1, MBC: 12251 mg ⋅ kg-1). However, there was little difference in soil P sorption between the three particle sizes of the same biochar in the soil system. In comparison with no biochar treatment, the addition of SBC increased the Langmuir P sorption maximum (Smax) by 236.8%-755.7%, and decreased soil P desorption rate. The addition of MBC increased Smax, but the enhancement was less than that of SBC. Soil P desorption rate was increased by 7.2%-295.9%. Both SBC and MBC significantly increased the contents of soil total P, available P, and exchangeable calcium (Ca) and magnesium (Mg). The increases in Ca and Mg contents due to biochar addition was 64.0%-257.1% (SBC) and 39.1%-205.3% (MBC), respectively. The contents of soil exchangeable Ca and Mg were positively correlated with Smax. These results suggested that biochar particle size had little effect on soil P sorption, but the enrichment of Ca and Mg due to biochar addition played a critical role in regulating soil P sorption. The rapeseed straw biochar had a high adsorption capacity for soil P, making it suitable for improving the P fixation capacity of soil rich in P and reducing the loss of excess P. Chicken manure biochar could be used to improve the P availability of low P soils and increase the contents of available P. [ABSTRACT FROM AUTHOR]

[Display omitted] Doping of metal oxide with other suitable component can enhance its structural and characteristic properties. At the end it improves its overall application performances. This study introduces the novel synthesis of Al 2 O 3 @TiFe 2 O 4 nanocomposite via co-precipitation for Cr(VI) removal. Unlike previous studies, this unique material exhibits superior adsorption capacity and efficiency. The comparative analysis with existing adsorbents underscores its potential for industrial effluent treatment. The nanocomposite's recyclability and minimal efficiency loss over multiple cycles highlight its sustainability for wastewater treatment. Overall, this research fills existing gaps by presenting an advanced, environmentally friendly adsorbent, significantly enhancing the field of wastewater treatment and environmental remediation. The nanocomposite was characterized and used to study Cr(VI) adsorption characteristics. Amount, contact time, pH, and Cr(VI) concentration were found to influence the adsorption characteristics of the nanomaterial. The operating conditions of an adsorbent Al 2 O 3 @TiFe 2 O 4 are optimized utilizing the analysis of the adsorption kinetic data. As shown by the R2 responses, which were close to unity, the adsorption behaviour of the nanomaterial is in excellent harmony with the linearized Langmuir isotherm with a maximum capacity of 312.52 mg/g. Additionally, Al 2 O 3 @TiFe 2 O 4 active sites were more observed to be favorable for Cr(VI) ions at all experimental temperatures range, according to calculations of monolayer adsorption capacities using the Langmuir equation. The value of n was 0.40, 0.42, and 0.43, respectively 25, 35, and 45 °C. The adsorbent shows an adsorption capacity of 93 % with the RSD less than 2 %. [ABSTRACT FROM AUTHOR]

Adsorbents are obtained on the basis of coke fines (<8 mm) produced by the slow coking of heavy petroleum residues, by activation. Activation employs water vapor and potassium hydroxide, in various conditions. For all the activated carbon samples and also for AG-3 industrial activated carbon, the iodine number is determined, and experiments are conducted on the adsorption of phenol from aqueous solutions, over a broad concentration range (0.1–500 mg/dm3). The experimental results are used to plot a standardized isotherm of phenol sorption on the activated samples. The parameters of the Arrhenius equation (limiting adsorption, adsorption equilibrium constant) are presented. [ABSTRACT FROM AUTHOR]

The present work demonstrates that the use of iron(III) hydroxide as a sorbent fabricated by precipitation from a solution of iron(III) chloride can purify contaminated solutions from toxic nickel ions. The study was performed at room temperature on a model of solution of sodium sulfate (400 mg/L) simulating polluted natural and wastewater. It has been shown that the removal of nickel ions from the model solution by iron(III) hydroxide precipitate at pH 7 and 8 is described with a satisfactory accuracy by the classical adsorption isotherms of Freundlich, Langmuir, and Dubinin–Radushkevich. Low values of the free energy of adsorption that do not exceed 8 kJ/mol indicate the physical nature of adsorption and exclude ion-exchange interaction of nickel ions with iron(III) hydroxide. The most complete removal of nickel ions from the solution occurs during the sorption with iron(III) hydroxide at pH 8. The sorption capacity of iron(III) hydroxide toward nickel ions at both pH 7 and 8 is almost an order of magnitude higher than the same value for many mineral, carbon, and coal sorbents. During the sorption process at pH 7, the adsorption capacity of iron(III) hydroxide precipitates decreases along with the increase of the initial concentration of iron(III) ions in solution, whereas during sorption at pH 8, on the contrary, it remains constant and does not depend on the initial concentration of iron(III) ions in the solution. The obtained data enable one to select the concentration of iron(III) hydroxide precipitate required to achieve a preset depth of purification of contaminated solutions from nickel ions. [ABSTRACT FROM AUTHOR]

The ODM-2F sorbent based on diatomite with a porosity of ~75% is used as a filter material for effective wastewater treatment at a thermal power plant. At pH 6.0‒8.0, when metals Ni, Zn, Cu are in the form of Me2+ and MeON+ cations, the process of their separation per MM is described by two types of adsorption isotherms – Langmuir and S-shaped. For unmodified MM in the Ca-form, S-shaped isotherms are characteristic. For MM, partially and completely converted to the Na-form, metal adsorption isotherms acquire a Langmuir appearance. An increase in the salt background of the solution (100‒800 mg/dm3 NaCl) does not reduce the sorption capacity for copper (120‒130 mg/g), unlike organic resins. The adsorption of nickel, zinc, and copper cations at a pH of 7‒8 per MM in the Ca-form (11‒46 mg/g) is lower than in the Na-form (17‒75 mg/g), which is due to the high energy costs when replacing Ca2+ with metal counterions compared to Na+. [ABSTRACT FROM AUTHOR]

The kinetics of adsorption phenomena are investigated in terms of local and non-local kinetic equations of the Langmuir type. The sample is assumed in the shape of a slab, limited by two homogeneous planar-parallel surfaces, in such a manner that the problem can be considered one-dimensional. The local kinetic equations in time are analyzed when both saturation and non-saturation regimes are considered. These effects result from an extra dependence of the adsorption coefficient on the density of adsorbed particles, which implies the consideration of nonlinear balance equations. Non-local kinetic equations, arising from the existence of a time delay characterizing a type of reaction occurring between a bulk particle and the surface, are analyzed and show the existence of adsorption effects accompanied by temporal oscillations. [ABSTRACT FROM AUTHOR]

Background: Phosphorus (P) is among the essential elements for plant growth and one of the main elements of fertilizers. Decreased availability of P may limit agricultural production in the coming years. The magnitude of soil aggregation influences phosphorus access to mineral surfaces. Aim: The present study aims to determine phosphorus adsorption processes affected by soil aggregation under different land‐use systems. Methods: The distribution of soil aggregates was determined in representative soil samples in the district Kupwara of Kashmir Valley in India. To predict the phosphorus fertilizer requirement of a particular soil, we used the Freundlich adsorption equation and Langmuir equation and drew a clear comparison between these two models. Results and discussion: Maximum phosphorus (P) adsorption was recorded at the smallest aggregate size, 0.5–0.1 mm. However, soil aggregates >2.0 mm (the largest category) adsorbed the least amount of P. Our results revealed that increasing the addition of P to the soil decreased the percentage of adsorbed P regardless of aggregate size. The maximum P adsorption of different size aggregates varied between 1869–1924, 1872–1900, 1718–1739, and 1800–1890 mg P kg–1 in irrigated agriculture, forest, orchard and rainfed agriculture soils, respectively. The variation in P adsorption parameters across the different land uses was attributed to their mean weight diameter difference. The maximum bonding energy in the forest resulted in higher P adsorption. Langmuir and Freundlich's adsorption equations were fitted to each soil aggregate size and land‐use system. Conclusion: Our results revealed that for all soil aggregate sizes and land use systems, the Freundlich adsorption equation performs better than the Langmuir equation. [ABSTRACT FROM AUTHOR]

The sorption properties of BAU-A activated carbon with respect to nickel ions have been studied. The studies were carried out at room temperature on a model solution in the pH range of 5–8. It is shown that the adsorption isotherms of nickel ions by activated carbon BAU-A at different solution pH can be described with equal accuracy by two classical equations: Freundlich and Langmuir. The absence of a correlation between the parameters of the Freundlich equation and the change in the pH of the solution was found, which indicates the empirical nature of the description of the experimental data by this equation. The parameters of the Langmuir equation naturally change with a change in the pH of the solution. With an increase in the pH of the solution, the adsorption capacity of BAU-A with respect to nickel ions decreases, while the adsorption equilibrium constant, on the contrary, increases. Estimation of the free energy of adsorption according to the Dubinin–Radushkevich equation showed that it does not exceed 1 kJ/mol, which excludes the ion-exchange interaction of nickel ions with BAU-A. Comparison of the parameters of the Langmuir equation for the sorption of nickel ions with similar data for copper(II) ions shows that the adsorption capacity of BAU-A for nickel ions is approximately an order of magnitude higher than for copper(II) ions. This makes it possible to recommend this sorbent for the selective extraction of nickel and copper ions from mixed solutions. [ABSTRACT FROM AUTHOR]

Background: Limited soil nutrients in the soil are threat in crop production in Ethiopian soil. Low availability of phosphorus (P) is one amongst the most important crop yield‐limiting problems among the various reasons limiting P availability in tropical soils, P sorption is that the major one. Aim: Therefore, this study was done to identify P sorption characteristics of andosols, vertisols, and nitisols in Tachegnawgimbicho, Taba, and DelboAtwaro study sites in southern Ethiopia. Methods: Adsorption isotherms experiment was done using Langmuir and Freundlich models to spot the character of soils in their capability on P sorption and causation and to explain P sorption as influenced by the associated soil properties using SAS version 9.00. Results: The P sorption maxima (Xm) of andosols, vertisols, and nitisols were found to be 965, 810, and 706 μg g−1, respectively. Correlation analysis indicated that soil pH was negatively and significantly correlated with Xm (R2 = −0.88). The Langmuir affinity constant "k" was positively and significantly correlated (R2 = 0.981) with maximum phosphorus buffering capacity (MPBC) indicating bonding energy constant is a component of buffering capacity of soils. The Langmuir equation correlated significantly with P sorption maximum "b" and binding energy "k" indicating both parameters can be used for evaluating P sorption characteristics of the soils. Conclusion: In this finding, the path analysis coefficient revealed that clay and pH had direct effects on P sorption parameters. Sorption capacity is high in andosols followed by nitisols and vertisols. Andosols require more P fertilizer to maintain optimum P concentration in soil solution for crop growth as compared with nitisols and vertisols. [ABSTRACT FROM AUTHOR]

In order to obtain the internal correlation of gas content and gas pressure suitable for different mining areas in Guizhou Province, and accurately calculate the measured values of the two indexes in line with the characteristics of coal seams, the W-P optimization model was established by statistical analysis of 107 groups of coal seam gas basic parameter data of 57 pairs of mines in 8 mining areas, based on the Langmuir equation, introducing the failure coefficient X and the initial velocity of gas emission △p, and the W-P classical model and W-P optimization model were compared. This paper makes a comparative study on the applicability in Guizhou mining area. The results show that: the gas content and pressure data calculated by W-P optimization model have high fitting degree with the measured value, and the fitting degree gradually increases with the increase of the sample size of the measured value, and the average relative error is 6.44% and 14.27% respectively. Compared with the classical model, the average relative error of the optimization model is reduced by 17.54% and 83.59% respectively; the critical values of gas content and gas pressure in M16 coal seam are determined to be 8.0 m3/t and 0.74 MPa respectively by using W-P optimization model, which is consistent with the gas content and gas pressure at the actual gas dynamic phenomenon in M16 coal seam.

Optical biosensors provide a platform for qualitatively and quantitatively analyzing various biomolecular interactions. In addition to advantages such as label-free and high-throughput detection, these devices are also capable of measuring real-time binding curves in response to changes in optical properties of biomolecules. These kinetic data may be fitted to models to extract binding affinities such as association rates, dissociation rates, and equilibrium dissociation constants. In these biosensors, one of the binding pair is usually immobilized on a solid substrate for capturing the other. Due to the nature of these surface-based methods, mass transport effects and immobilization heterogenetity may cause problems when fitting the kinetic curves with the simple one-to-one Langmuir model. Here real-time binding curves of various antibody-antigen reactions were obtained by using an ellipsometry-based biosensor, and the results were fitted to the simple one-to-one model as well as a more sophisticated approach. The results show that the one-to-two model fitted much better to the curves than the one-to-one model. The two-site model may be explained by assuming two immobilization configurations on the surface. In summary, in fitting real-time curves obtained from optical biosensors, more sophisticated models are usually required to take surface-related issues, such as immobilization heterogenetity and mass transport effects within targets, into account.

In the article possibility of water solution LiOH tertiary treatment from chlorine anions after electrolysis is viewed. Analyzing the existing purification methods, it is proposed to use the purification of lithium hydroxide in an ion exchange column. A mathematical model and a computational algorithm for ion exchange column having stationary and moving anionite layers AВ-17-08 in ОН-form are given. Relationships of the main parameters such as working cycle period, usage ratio of ionite exchange volume and specific ratio of solution being purified per 1 kg ionite for standard column have been received. The curves of the chlorine anions density in ionite depending on its layer height in the solution being purified in the middle and at the end of the working cycle period are given. In the article recommendations on prevention of ionite granules abrasion during the operation in ion exchange columns are given.

Metals and glyphosate (GPS) herbicides adsorbed on minerals affects their mobility and environmental effects. In this study, using goethite as a model soil mineral, GPS and uranium as contaminants to investigate the effects of GPS on adsorption of uranium. The effects of solution pH, initial concentration and contact time on adsorption were investigated. When the initial pH is 4.0, the highest adsorption capacity of goethite for uranium with the absence GPS and the presence of GPS are 69.39 mg g−1 and 78.84 mg g−1 respectively. The adsorption kinetics can be well described by quasi second-order model, and the adsorption process can be described by Langmuir isotherm. Additional evidence for the uptake mechanism was obtained using FTIR and XPS. The carboxylic acid and phosphonic acid groups of the GPS molecule participated in the reaction with goethite and uranium to form goethite-GPS-U(VI) ternary complex. [ABSTRACT FROM AUTHOR]

During this work, the root of the Gundelia plant, which is one of the types of nuts, was used to prepare activated carbon with phosphoric acid (H³PO4) and zinc chloride (ZnCl²) and used as an adsorbent surface to remove lead ions (Pb+2) and para-phenylene diamine (PPD) dye. It was prepared by using infrared spectroscopy (FT-IR) and showed that it contains many functional groups such as hydroxyl (OH) and carbonyl (C=O). The surface morphology was also diagnosed using scanning electron microscope (SEM) and it was shown that the rough surface contains many From pores and gaps, ash content and moisture were measured, and the outer and inner surface area was determined using methylene blue indicator, iodine indicator, and pH at zero charge point (pH pzc) was determined. The effect of contact time, adsorbent dose, temperature, and initial concentration of the adsorbent materials on the percentage of adsorption was studied. The initial concentration of the adsorbents increases the amount of adsorption (Qe), but the percentage of adsorption decreases with the increase in the initial concentration. The adsorption isotherms (Langmuir and Freundlich) were applied. It was found that the adsorption process fully corresponds to Freundlich's equation and partially with the Langmuir equation. The adsorption kinetics were studied, and it was found that the adsorption follows the equation False second order The thermodynamic functions (ΔG, ΔS and ΔH) were calculated and it was found that the adsorption process is endothermic as the adsorption increases with increasing temperature and that the adsorption process is spontaneous and accompanied by an increase in randomness, meaning that it is less uniform on the adsorbent surface than it is in the solution and an analytical study was conducted Preconcentration methods include Batch method and the column method to remove small concentrations of ions in large quantities of aqueous solutions. [ABSTRACT FROM AUTHOR]

A review of the use of waste from thermal power plants as secondary resources in industry and agriculture has been carried out. The results of a study of the structural-surface and physicochemical properties of ash and slag from a thermal power plant operating in an industrially developed region of the far north (the city of Apatity, Murmansk oblast) are presented. According to the data of chemical analysis, silicon and aluminum oxides predominate in their composition, the content of calcium oxide does not exceed 2.1%. It was established by the BET and BJH methods that the material has a predominantly mesoporous structure and a specific surface area of 17.8 m2/g that corresponds to the maximum observed in European medium-sized TPP plants. The phase composition of ash and slag was identified using the International Diffraction Database JCPDC-ICDD 2002; the dominance of quartz and calcium ferrite is noted in the mineral composition, but a significant part of the material is present in the X-ray amorphous state. It was found that, in terms of the main indicators, ash and slag correspond to the F-type of the international classification ASTM C 618, which makes it possible to recommend them for use as a sorbent in the treatment of domestic wastewater. The predominant extraction of the multicomponent composition of cationic forms from solutions was predicted from the pH value of the isoionic point equal to 7.63. Experimental data were obtained on model solutions in the range of concentrations of ammonium ions typical for municipal wastewaters of the city geographically adjacent to the TPP. Processing of the results obtained using the Langmuir sorption equations was carried out. The sorption capacity of ash and slag is 20.43 mg According to the results of experiments on the study of the kinetics of sorption on model solutions, the degree of extraction of ammonium ions when using ash and slag reaches 90% of the equilibrium concentration within 1 h, the sorption process is limited by external diffusion. An assumption is made about the expediency of using the spent sorbent, which is proposed as an ameliorant with a prolonged fertilizing effect, for the formation of bulk soils during the restoration of anthropogenically disturbed territories. [ABSTRACT FROM AUTHOR]

The kinetics of adsorption phenomena are investigated in terms of local and non-local kinetic equations of the Langmuir type. The sample is assumed in the shape of a slab, limited by two homogeneous planar-parallel surfaces, in such a manner that the problem can be considered one-dimensional. The local kinetic equations in time are analyzed when both saturation and non-saturation regimes are considered. These effects result from an extra dependence of the adsorption coefficient on the density of adsorbed particles, which implies the consideration of nonlinear balance equations. Non-local kinetic equations, arising from the existence of a time delay characterizing a type of reaction occurring between a bulk particle and the surface, are analyzed and show the existence of adsorption effects accompanied by temporal oscillations.

The vertical mass flux profile for wind-blown sand is an important research topic in aeolian physics. It is generally believed that the relationship between sand transport rate and height can be expressed as an exponential function or a power function. However, the accuracy of these models is questionable, and the influence of the focal height on the vertical flux profile is ignored. The Langmuir equation has been widely used to describe the adsorption process of different solid–liquid systems and is one of the most commonly used adsorption isotherm equations. In this study, the Langmuir equation was applied to simulate the vertical flux profile and tested with field observations from the Badain Jaran Desert and the previous three case studies. The simulation effect of the Langmuir equation is better than the exponential function and the power function, and it is applicable for different wind regimes and underlying surfaces. Each coefficient in the proposed equation has an exact physical meaning. This equation can be improved into an extended form (the LangmuirEXT equation) to describe the changing trend of the sand transport rate in the near-bed layer more accurately. The results of this research will provide support for the design of sand control measures and the mitigation of sand disasters. [ABSTRACT FROM AUTHOR]

The physicochemical and sorption properties of MIU-S carbon sorbent have been studied. The studies were carried out on a model solution of nickel(II) sulfate containing an additional 400 mg/L sodium sulfate in the pH range of 5–8. It has been shown that the MIU-S sorbent is capable of removing nickel(II) ions from solution by the mechanism of simple monomolecular adsorption described by the Langmuir equation. The parameters of this equation are determined for different pH values of the model solution. It was found that, with an increase in the pH of the solution from 5 to 8, the efficiency of sorption of nickel(II) ions by the MIU-S sorbent increases. The sorption properties of MIU-S with respect to nickel(II) ions are compared with the properties of other carbon (coal) sorbents described in the literature. [ABSTRACT FROM AUTHOR]

The present review is devoted to the sorption properties of magnetite towards hexavalent chromium ions and the possibility of its use as a sorbent for removing these toxic ions from contaminated aqueous solutions. The behavior of magnetite nanoparticles in aqueous solutions has been also investigated. It has been shown that two processes occur simultaneously during the sorption of chromium(VI) ions by magnetite: ordinary adsorption and chemisorption (redox reaction between hexavalent chromium ions and magnetite). The latter is accompanied by the oxidation of iron(II) in magnetite to iron(III) and the reduction of chromium(VI) ions to chromium(III) with the formation of maghemite and a number of other compounds, including mixed chromium(III) compounds with iron, in the surface layer of magnetite (or onto its surface). It has been demonstrated that the kinetics of the redox process between chromium(VI) and magnetite is described by the first-order reaction equation with respect to the concentration of chromium(VI) ions in a solution. As a result of chemisorption, unlike the case of traditional sorbents, chromium(VI) is irreversibly bound by magnetite, which eliminates the reentry of its ions into the environment. Here, the sorption capacity of magnetite irreversibly decreases in the course of its saturation with chromium. In addition, the sorption capacity of magnetite towards chromium(VI) ions also decreases along with increasing pH of the purified solution, and at pH > 11 it becomes almost zero. [ABSTRACT FROM AUTHOR]

The sorption of copper(II) ions by the mineral filter material MS was studied. The study was carried out on a model solution of copper(II) sulfate containing an additional 400 mg/dm³ of sodium sulfate. It demonstrates that the sorption properties of MS are due to the simultaneous action of two factors. The first is associated with an increase in the pH of the solution being purified when the MS material is introduced into it, which leads to the precipitation of copper(II) ions from the solution in the form of the corresponding hydroxide. The second is the ability of the MS to remove copper(II) ions from the solution by the mechanism of adsorption described by the Langmuir equation. It was found that with an increase in the pH of the solution from 4 to 6.7, the adsorption of copper(II) ions on the surface of the MS increases (ranges of pH<4 and pH>6.7 have not been studied). The found values of the MS monolayer capacity with respect to copper(II) ions turned out to be comparable in magnitude with similar values for some other mineral sorbents. [ABSTRACT FROM AUTHOR]

Ion-exchange modeling is one of the most widely used methods to predict ion adsorption data on clay minerals. The model parameters (e.g. number of adsorption sites and the cation adsorption capacity of each site) are optimized normally by curve fitting experimental data, which does not definitively identify the local environment of the adsorption sites. A new approach for constructing an ion-exchange model was pursued, whereby some of the parameters needed were obtained independently, resulting in fewer parameters being based on data-curve fitting. Specifically, a reversed modeling approach was taken in which the number of types of sites used by the model was based on a previous first-principles Density Functional Theory study, and the relative distribution of these sites was based on the clay's chemical composition. To simplify the ion-exchange reactions involved, montmorillonite was Na-saturated to produce a well-controlled Na-montmorillonite (NaMnt) adsorbent. Ion adsorption data on NaMnt were collected from batch experiments over a wide range of pH, Cs+ concentrations, and in the presence of coexisting cations. Ion-exchange models were developed and optimized to predict these cation adsorption data on NaMnt. The maximum amount of adsorption of monovalent cations on NaMnt was obtained from the plateau of the adsorption envelope data at high pH. The remaining equilibrium constants (pK) were optimized by curve fitting the edges of the adsorption envelope data. The resultant three-site ion-exchange model was able to predict the retention of Li+, Na+, K+, and Cs+ very well as a function of pH. The model was then tested on adsorption envelopes of various combinations of these cations, and on Cs+ adsorption isotherms at three different pH values. The pK values were constant for all assays. The interlayer spacing of NaMnt was also analyzed to investigate its relation with cation adsorption strength. An X-ray diffraction study of the samples showed that the measured d001 values for these cations were consistent with their adsorption pK values. The Cs+ cation showed a strong ability to collapse the interlayer region of montmorillonite. In the presence of multiple competing cations, the broadening and presence of multiple d001 XRD peaks suggested that the cations in the interlayers may be segregated. [ABSTRACT FROM AUTHOR]

The possibility of using the PSTC-3F synthetic organosilicone sorbent for the adsorption removal of mercury from an aqueous solution has been studied. The dependence of mercury adsorption on the pH of the solution, the amount of the adsorbent and the duration of the contact of the solution with the adsorbent is examined. It is shown that the higher the solution acidity is, the higher the adsorption value is. It has been established that the mercury adsorption process on the PSTC-3F sorbent is described by the Freundlich equation. [ABSTRACT FROM AUTHOR]

This account, a hyperbranched dispersant (Es-SAF-DBM-PSS) was assembled with the skeleton of Es-SAF-DBM (the functional modification of hydroquinone-based sulfonated acetone formaldehyde (SAF)) and numbers of linear polystyrene sodium sulfonate (PSS) chains by single electron transfer living radical polymerization (SET-LRP) in the system of PhBr 2 m 4 /Cu wire/PMDETA. The structure of the synthesized Es-SAF-DBM-PSS was detected by FTIR, 1H NMR, XPS, UV and GPC. Series of tests about the polymerization kinetics of Es-SAF-DBM-PSS were executed. Effects of temperatures and initiator concentration on the apparent polymerization rate were investigated, the results showed the low activation energy and higher initiation rate fitted the characteristic of SET-LRP. The rheological behaviors of Es-SAF-DBM-PSS as dispersant applied to coal water slurry (CWS) were tested. The following results were found as expected: the best usage of Es-SAF-DBM-PSS was only 0.3%, maximum coal content reached 63.7%, the viscosity dropped as low as 1000mPa·s. And the penetration ratio of slurry mixed with Es-SAF-DBM-PSS was still 100% even after 35days. Adsorption mechanism and interparticle interactions of coal particles modified with Es-SAF-DBM-PSS were investigated by Langmuir equation, dynamic equations and extended Derjaguin-Landau-Verwey-Overbeek (eDLVO) theory, the results showed the excellent dispersion and stability performance of Es-SAF-DBM-PSS were mainly related to the specific hyperbranched structure. [Display omitted] • A novel hyperbranched dispersant was designed via SET-LRP. • The stability of CWS mixed with Es-SAF-DBM-PSS was 100% even after 35days. • Interparticle interactions of coal particles were studied by eDLVO theory. [ABSTRACT FROM AUTHOR]

The problem of substantiating a pseudo-second order equation in the kinetics of sorption processes is considered. A simple way is presented of transforming the Langmuir kinetic equation written for a process within a limited volume into a polynomial relation in the form of the sum of difference terms of first- and second-order kinetic equations. It is shown that such a relation is reduced to a good approximation of a pseudo-second order equation over a much wider range of conditions determined by the equilibrium and kinetic characteristics of the sorbent and the experimental parameters than was predicted earlier. It is established that the errors of such a theoretical approximation are either negligible or do not exceed the corresponding errors at the initial stage of kinetic experiments within a confined space. It is concluded that the applicability of the pseudo-second order model is independent of the mechanisms determining the rate of sorption and does not require concepts of chemisorption or special equations of kinetics controlled via chemical reactions or diffusion. [ABSTRACT FROM AUTHOR]

The invasive nature of Eichhornia crassipes, Pistia stratiotes, and Nymphaea lotus is worrisome because they tend to dominate the economic and ecological region of the aquatic environment, hence the need for their eco-friendly utilization. This research is aimed at assessing the efficacy of Eichhornia crassipes, Pistia stratiotes and Nymphaea lotus as a low-cost absorbent for the biosorption of Nickel (Ni2+) from refinery wastewater. Refinery wastewater was collected from the effluent point of Kaduna Refining and Petrochemical Company (KRPC). The selected macrophytes were characterized using Fourier transform infrared (FTIR) spectroscopy. Biosorption of Ni2+ from the wastewater and aqueous Ni2+ solution was performed under factors such as contact time, particle size, absorbent dosage, pH and Ni2+ concentration. The Langmuir equation and Freundlich isothermal were used in determining absorption equilibrium while pseudo-first and pseudo-second-order were used to determined adsorption kinetics. The result obtained shows that Ni2+ absorption by the selected macrophytes is greatly influenced by contact time, particle size, absorbent dosage, pH and Ni2+ concentration with high efficiency recorded in the removal of Ni2+ from refinery wastewater. Both Langmuir equation and Freundlich isothermal gives a nearly perfect fitting for adsorption of Ni2+ for all the selected macrophytes signifying favorable Ni2+ absorption. Pseudo-second-order kinetic model gives nearly perfect fitting than the pseudo secondorder kinetic model signifying that adsorption of Ni2+ by the selected macrophytes is due to the physical and chemical reaction. The selected macrophyte can be effectively utilized as low-cost biosorbents for the removal of Ni2+ from Refinery wastewater. [ABSTRACT FROM AUTHOR]

The isosteric heat of adsorption (IHA) is one of the key thermodynamic variables for evaluating the interaction between shale and methane, which is rarely studied especially under high pressure. In this work, we conducted methane adsorption experiments at pressures up to 30 MPa and different temperatures on shale samples collected from Longmaxi formation in Sichuan Basin, China. Based on the definition of IHA and Langmuir adsorption model, we proposed a new method to analyze the IHA of methane on shale under four conditions. The calculated results show that the commonly used Clausius–Clapeyron equation overestimates the true isosteric heat of shale, especially under high pressure. IHA under four conditions yield a fixed order as q st,i-va > q st,r-va > q st,i+va > q st,r+va, indicating both the real gas behavior and the adsorbed-phase volume have a negative influence on it, and the effect of adsorbed-phase volume is dominant. Moreover, IHA at zero coverage ( q st 0 ) in Henry region determined by linear fitting can be regarded as a maximum value in the above four cases, which is independent of pressure and temperature. Therefore, q st 0 can be used as a unique descriptor to evaluate the adsorption affinity of the shale. This work modified the method to obtain the true IHA of supercritical methane on shale more accurately, which lays the foundation for future investigations of the thermodynamics and heat transfer characteristics of the interaction between high pressure methane and shale. [ABSTRACT FROM AUTHOR]

• Malachite green adsorption behavior on four types of commercial activated carbons was studied. • The effect of pore and surface chemical properties for malachite green adsorption is confirmed. • Malachite green adsorption performance on activated carbon depends on the total specific surface area. Malachite green (MG) separation from wastewater has always been a research focus in the field of environment. Removal of MG from aqueous solution using activated carbon has been studied or verified. Because of the different preparation materials and processes, the physicochemical properties of activated carbons differ significantly, and it is not clear which parameter affects on MG adsorption and to what extend it is. Four types of commercial activated carbon were selected to study their MG adsorption performances systematically, such as adsorption contact time, equilibrium adsorption capacities, Langmuir and modified Langmuir equations fitting, adsorption thermodynamics and effect of pH. The study of contact time showed that MG adsorption on four activated carbons fits the pseudo-second-order equation in the initial stage. However, the adsorption kinetics is found to follow pseudo-first-order equation with the increase of adsorption capacities. Consistent with the results reported in the literature, the adsorption mechanism of MG on activated carbon is monolayer physisorption. We associated MG adsorption behavior on four activated carbons with the specific surface area from different pore structures and content of surface chemical groups, respectively. The results showed that the strong acidic groups have the detrimental influence on the MG adsorption, while the total specific surface area has a notable effect, showing a positive linear relationship between the total specific surface area and the adsorption capability. Therefore, the total specific surface area could be used as a key parameter to determine the adsorption performance of MG on activated carbon. [ABSTRACT FROM AUTHOR]

In order to obtain the functional relationship of gas content and gas pressure, and to accurately calculate the two values which fitting the characteristics of coal seam, the destruction coefficient (X) and the index (ΔP) of the initial velocity of gas emission are introduced to establish the new model with higher precision based on Langmuir equation and destruction type of coal. The applicability of classic model (W-P model) and new optimization model in Guizhou mining areas are studied through the statistics of basic parameter data from 107 groups of coal-seam gas in eight mining areas. The results show that the gas content calculated by the classical model is lower than the measured value, while the gas pressure value is larger than that. The average relative error of gas content and pressure data reach 23.98% and 97.86%, respectively. The gas content and pressure data calculated by the optimization model are well fitted with the measured value. The fitting degree gradually rises with the increase of the sample size, and the average relative errors are 6.44% and 14.27%, respectively. Compared with the classical model, the average relative errors of gas content and pressure calculated by the optimization model reduce by 17.54% and 83.59%, respectively. The optimization model controls the tendency of calculated value error which significantly rises as the ΔP increases. For the coals with different destruction types, the average relative error of calculated gas content in optimization model ranges from 4.40% to 11.99%. And the average relative error of calculated pressure value ranges from 9.84% to 25.80%, both of them are far superior to that of classical model. The optimization model is more accurate for calculating the gas content and pressure in Guizhou. [ABSTRACT FROM AUTHOR]

At most coke plants of Ukraine and the world, ammonium sulphate (NH4)2SO4, which is an ammonium fertilizer, get in the department of trapping chemical products of coking. The liquid wastes formed in this department called phenolic wastewater, the main polluting agents of which are tarry substances. When choosing industrial adsorbent for wastewater treatment, the value of specific surface area is a determining factor. The high cost of modern industrial sorbents causes necessity of finding of new, more affordable their analogs, among which of particular interest are natural bentonite clays. Aim: The aim of research is to study the regularities of extraction process of tarry substances of manufacturing sewage of a ammonium sulphate with use of sodium and calcium bentonites, an absorbite and peat, and definition of a specific surface area of the specified adsorbents. Materials and Methods: In this study the absorbite AG-5, valley peat and natural sodium and calcium bentonite clays are used as sorbents. The adsorption of tar substances had been researched during the flotation process of phenolic wastewater in conditions close to industrial: the duration of flotation is 20 min; the wastewater temperature is 323 K; the intensity of air supply – 0.15 dm3/h. The calculations suggested that the adsorption of tarry substances is monomolecular in nature and described by the Langmuir’s theory of monomolecular adsorption. Results: The specific surface area of the adsorbents during the adsorption process of tarry substances from a phenolic industrial wastewater defined for the first time are following (m2/g): sodium bentonite clay – 1847; absorbite AG-5 – 1467; calcium bentonite clay – 728; valley peat – 603. For these adsorbents was also calculated the limit value of adsorption and constant of adsorption equilibria. The obtained values indicate a strong interaction between adsorbent and adsorbate, especially significant for the bentonite clay and absorbite. It was found, that sodium bentonite is more effective on all counts compared with absorbite, and recommended thus for industrial application.

The adsorption and desorption process of the tungstate ion was studied in three soils characteristic of the Mediterranean area, with particularly reference to bioavailability pathways. In the three soils examined, the tungstate adsorption was described by a Langmuir-type equation, while the desorption process showed that not all the adsorbed tungstate was released, probably due to the formation of different bonds with the adsorbing soil surfaces. The pH was found to be the main soil property that regulates the adsorption/desorption: The maximum adsorption occurred in the soil with the acidic pH, and the maximum desorption in the most basic soil. In addition, the organic matter content played a fundamental role in the adsorption of tungstate by soils, being positively correlated with the maximum of adsorption. These results indicate that the lowest bioavailability should be expected in the acidic soil characterized by the highest adsorption capacity. This is confirmed by the trend of the maximum buffer capacity (MBC) of soils which is inversely related to bioavailability, and was the highest in the acidic soil and the lowest in the most basic soil. Our data could contribute in drafting environmental regulations for tungsten that are currently lacking for Mediterranean soils.

Thermal transitions have been determined for different ternary compositions of polylactide and poly-3-hydroxybutyrate with chitosan from their TGA and DSC data. The sorption capacity of the ternary mixtures for FeIII ion has been evaluated using the Langmuir model and found to increase with the chitosan content. [ABSTRACT FROM AUTHOR]

Fractions of phosphorus (P) and its sorption characteristics are affected by different soil fertility (FM) technologies which ultimately affect crop growth and productivity. However, the response of P fractions and sorption characteristics to soil fertility technologies that integrate diverse amendments is still poorly understood in acidic Nitisols. A randomized complete block design was layout in an acidic Nitisol to determine fractions of P, its sorption characteristics and use efficiencies in acidic Nitisols under various FM technologies in field conditions. The use of minimum tillage + maize residue + inorganic fertilizer + goat manure (MTCrGF) had the highest impact on and significantly increased resin-Pi, NaHCO 3 -Pi, and maximum P sorption (S max ) by 182, 76, and 52 mg P kg -1 . Moreover, NaOH-Pi and S max concentrations were higher under conventional tillage + maize residue + inorganic fertilizer + goat manure (CTCrGF) by 216 mg P kg -1 and 49 mg P kg -1 than the control. MTCrGF and CTCrGF also had the lowest P bonding energy (0.04 L mg -1 ). CTCrGF had the highest P partial productivity factor (0.093 and 0.140 kg biomass kg -1 P) and P agronomic efficiency (0.080 and 0.073 kg biomass kg -1 P) during the two cropping seasons. The results demonstrate the positive influence of combining multiple P sources on soil P fractions, sorption characteristics, and use efficiencies. Notably, combining either conventional or minimum tillage with maize straw and applying integrated manure and inorganic fertilizer (MTCrGF or CTCrGF) can increase the labile P concentrations and reduce the potential depletion of the non-renewable rock phosphate and the use of inorganic phosphatic fertilizers for agricultural production., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 The Authors.)

Knowledge of the gas sorption characteristics of a coal not only helps to explain the mechanism of enhanced coalbed methane recovery but also provides an important basis for simultaneous coal and gas extraction. In consequence, the pure and binary gas excess sorption capacity of methane, carbon dioxide, and nitrogen of bituminous coal samples derived from the Xutuan Coal Mine in Huaibei coalfield, in Anhui Province in China, was measured using the volumetric method. The fitting analysis of the pure gas Langmuir adsorption model was carried out. The binary gas excess sorption measurement showed that the final sorption capacity of bituminous samples was the same no matter what the gas adsorption order of competitive adsorption and displacement adsorption. Hence, coal gas adsorption is physical adsorption, i.e. the different adsorption and desorption process of gas molecules does not affect the final adsorption amount of coal to each component of gas. Using the fitting parameters obtained by the Langmuir equation, the extended Langmuir equation was used to predict the adsorption capacity for each component of the binary gas. The comparison between predicted adsorption capacity and measured adsorption capacity showed that the extended Langmuir equation can better describe the trend of the adsorption isotherm curves of a binary gas under different pressures. The separation coefficient and displacement coefficient were defined from Langmuir adsorption theory. The separation coefficient involves the proportion of each component in the free phase and the proportion of each component in the adsorption phase. The displacement coefficient involves the displacement ability of gas molecules at adsorption sites by free gas molecules. [ABSTRACT FROM AUTHOR]

The low-dimensional maghemite γ-Fe2O3 has been synthesized by the precursor method. The basic formate of the composition Fe(OH)(HCOO)2 produced by an original technique was used as a precursor. A study of the magnetic and adsorption properties of the synthesized maghemite showed that it is ferrimagnetic in a wide temperature interval and an effective sorbent for removal of bivalent copper ions from aqueous solutions. The process of adsorption of Cu2+ ions by γ-Fe2O3 powder is described by the Langmuir equation. A comparison of the obtained parameters of the Langmuir equation with available literature data reveals that, allow for the specific surface area, the maghemite powder synthesized in this work surpasses the maghemite samples produced by other methods in the adsorption capacity with respect to copper ions. [ABSTRACT FROM AUTHOR]

Sorption properties of commercial hematite (α-Fe2O3) for divalent copper ions were studied. This was done with a model solution of copper(II) sulfate additionally containing 400 mg L-1 of sodium sulfate. It was shown that the hematite sample under study is a good sorbent for removal of divalent copper ions from aqueous solutions. The process of Cu2+ sorption is described by the Langmuir equation. The parameters of this equation were determined at various pH values of the model solution and compared with similar published parameters for other hematite samples. [ABSTRACT FROM AUTHOR]

• Thermogravimetry was used for vapor pressures estimation of two chromones. • Vapor pressures obtained by isothermal thermogravimetry agree with literature data. • Estimates vapor pressures lead to obtain sublimation enthalpies. • Entropies and Gibbs energies were derived from experimental data. In present work, the estimation of vapor pressures of 3-formylchromone and 3-formyl-6-methylchromone by the isothermal thermogravimetry method is presented. Briefly, this method consists of measuring the rate of mass loss as a function of temperature in a cylindrical cell and with a flow of nitrogen. To derive the vapor pressure, the Langmuir equation was used, from which the vaporization constant was calculated using anthracene as a calibrating compound. Subsequently, the vapor pressures 3-fromylchromone and 3-formyl-6-methylchromone were estimated. From the vapor pressure, the enthalpy of sublimation was calculated using the Clausius-Clapeyron equation for each compound at its mean sublimation temperature. Finally, the enthalpy of sublimation was calculated at T = 298.15 K. The entropy and Gibbs energy of sublimation at the same temperature were determined. In order to test the validity of the method, the vapor pressures of phenanthrene and pyrene were calculated. The values obtained by isothermal thermogravimetry agree with those reported by other techniques. [Display omitted] [ABSTRACT FROM AUTHOR]