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This paper describes instrumentation of a spectrophotometric system and its application for in-situ, real-time measurement of adsorption thermodynamics in aqueous solution by use of laboratory-constructed fiber-optic measurements. A measurement vessel was assembled from an adsorption bag, stirring and thermostatic devices, and a fiber-optic dipping probe. A macroporous adsorption resin and rutin were selected as the model adsorbent and adsorbate. In-situ liquid phase adsorption measurement of the system was achieved through monitoring of the absorption by dipping the probe in a broad range of concentrations. In-situ measurement of the AB-8 resin adsorption at temperatures from 303 K to 323 K was systematically carried out, showing that temperature was an influencing factor for the adsorption capacity and initial adsorption rate. The adsorption thermodynamic parameters for AB-8 indicated that the results well fitted the Freundlich model. In addition, a favorable, exothermic, spontaneous, physical process of rutin was demonstrated on AB-8. The obtained results showed that this method was successful at keeping the adsorption temperature constant. The application of fiber-optic sensing to the in-situ measurement of liquid phase adsorption enables automated and real-time monitoring of adsorption thermodynamics. [ABSTRACT FROM AUTHOR]

A series of functional hyper-cross-linked resins were successfully synthesized by incorporating anhydride, sulfoacid and menthanone groups into post-cross-linked polymer. They were evaluated for adsorption of 2-amino-4-methylbenzothiazole (2A4MBT) from aqueous solution. The five resins were efficient for adsorption of 2A4MBT from aqueous solution. The adsorption process includes both physical adsorption and irreversible chemical adsorption. The absolute value of adsorption enthalpy had an order of PRLMR (3.24 kJ mol−1) < IDLMR (7.96 kJ mol−1) < TMAMR (9.72 kJ mol−1) < PAMR (−13.1 kJ mol−1) < SAMR (21.8 kJ mol−1). Phthalic anhydride-modified resin could be regenerated by 10% HCl/methanol solution after adsorption equilibrium. [ABSTRACT FROM AUTHOR]

Abstract: This study reports the synthesis, characterization and applicability of surface-modified biochar, an eco-friendly and economic adsorbent for the removal of highly toxic hexavalent chromium from drinking water at a pH suitable for drinking water. The acid modification of the pristine biochar prepared by the pyrolysis of rice husk substantially enhanced the carbon content percentage by 25.29% and active sites by 10 times in the acid-modified biochar and produced a BET surface area of 142.78 ± 2.57 m2 g−1. Furthermore, the alteration of the surface of pristine biochar resulted in the substantial increase in C=C, C=O, C-O, phenolic and alcoholic -OH bonds on the surface of the biochar which further facilitated the adsorption of Cr. The batch adsorption study was carried out to comprehend the process of adsorption. The Freundlich isotherm model has been found to be describing the adsorption process most precisely. The maximum adsorption capacity has been found to be 4109 μg g−1 at 30 °C and 4536 μg g−1 at 50 °C from the analysis of approximate adsorption site energy distribution function. The analysis of approximate adsorption site energy distribution function further showed the availability of more energetic sites to the adsorbate Cr(VI) oxyanions at higher temperatures. Further, the endothermic nature of the adsorption apart from the experimental outcomes has been evinced from the D-R isotherm model and from the values of ∆G° and ∆H°. The negative values of ∆G° at all the experimental temperatures indicate the spontaneity of the adsorption process. Furthermore, the values of ∆G° more than − 20 kJ mole−1 indicate the physisorption of Cr(VI) oxyanions on the adsorbent surface.Graphical abstract: [ABSTRACT FROM AUTHOR]

Mg-Al, Zn-Al and Mg-Fe magnetic layered double hydroxide (LDH) adsorbents were synthesized. The adsorption effect and influencing factors of these adsorbents were explored, and the adsorption mechanism of phosphorus was studied with advanced instruments. The results showed that the best adsorption performance was observed when the molar ratio of metals was 3 for the magnetic LDH adsorbents, and the maximum adsorption amount for phosphorus was 74.8, 80.8 and 67.8 mg/g for Mg-Al, Zn-Al and Mg-Fe LDHs, respectively. Pseudo-second-order kinetics could be used to describe the adsorption process of phosphorus onto the magnetic LDHs. The adsorption of phosphorus onto the magnetic LDHs was an exothermic process. Lower temperatures were favourable for adsorption, and the adsorption of phosphorus onto the magnetic LDHs was a spontaneous process. When the solid-liquid ratios were 0.10 g/L, 0.10 g/L and 0.05 g/L for Mg-Al, Zn-Al and Mg-Fe magnetic LDHs, respectively, the highest adsorption amount of phosphorus was achieved for each magnetic LDH. The maximum adsorption amount was observed at pH values of 6.0-8.0. The inhibitory effect of HCO3− on the adsorption capacity of phosphorus onto the magnetic LDHs was the strongest at a higher HCO3− concentration level. The relative content of -OH significantly reduced after adsorption of phosphorus by the FTIR analysis, which indicated that the mechanism of phosphorus removal was mainly through the exchange between hydroxyl on the adsorbent surface and phosphorus in water. XPS studies showed that oxygen provided electrons during the adsorption of phosphorus. [ABSTRACT FROM AUTHOR]

Copyright of Food Research & Development is the property of Food Research & Development Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this study, the molecularly imprinted polymers (MIPs) of capsaicin are prepared by bulk polymerization (MIPs1), precipitation polymerization (MIPs2), and surface imprinting technology based on SiO2/Fe3O4 particles (MIPs3), respectively. MIPs are characterized by scanning electron microscopy and fourier transform infrared spectroscopy. The adsorption kinetics and thermodynamics of these composites are also investigated to estimate their capacity to rebind capsaicin. The adsorption kinetics show that the adsorption process of MIPs1 is fitted to pseudo first‐order kinetic model, while the kinetic properties of MIPs2 and MIPs3 are well described by pseudo second‐order kinetic model. Adsorption thermodynamics analysis indicated that there are two kinds of binding sites with different affinity in each MIPs, whereas only one kind of binding site in non‐imprinted polymers. All adsorption isotherms of MIPs are fitted to Freundlich models, illustrated that binding sites are distributed heterogeneously in the surface of the materials, and the adsorption might occur in the multimolecular layers. Comparisons of experimental data of three MIPs are achieved and the results show that MIPs3 has the best affinity and absorption capacity to capsaicin. Moreover, the MIPs3 maintain the magnetic properties of Fe3O4 particles, which will be applied to the rapid separation of capsaicin from chili peppers samples. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 157–164 Capsaicin Molecularly Imprinted Polymers are synthesized based on bulk polymerization, precipitation polymerization, and surface molecular imprinting technique, respectively. The structures and adsorption characteristic of these polymers are investigated. The synthesized polymers based on surface molecular imprinting technique exhibit the best affinity and absorption capacity to capsaicin, which will be applied to the rapid separation of capsaicin from chili peppers samples. [ABSTRACT FROM AUTHOR]

Abstract NaA, NaX and NaZSM-5 zeolites were prepared by using silica extracted from rice hull ash as a raw material, and they were investigated for CO 2 adsorption performance as an adsorbent in order to solve the problem of suppressing the global warming. Three zeolites were synthesized by hydrothermal methods with seed technology, and a series of characterization methods, including XRD, FTIR, nitrogen adsorption-desorption and SEM, were used to demonstrate their advantages compared to traditional hydrothermal methods. The maximum equilibrium adsorption capacity of NaA-RS, NaX-RS and NaZSM-5-RS was 1.46, 3.12 and 2.20 mmol/g at 0 °C and 101.3 kPa, respectively. The CO 2 and N 2 adsorption isotherms recorded at different temperatures were perfectly fitted by the Dual-site Langmuir model. The CO 2 /N 2 selectivity and Henry's law constants were calculated to demonstrate that the samples have a stronger affinity for CO 2 , especially at low pressures. The isosteric heat of CO 2 and N 2 adsorption of the three zeolites was calculated, which was indicated that they were in an excellent potential for adsorption and separation of CO 2 in industrial flue gas. Graphical abstract Image 1 Highlights • NaA, NaX and NaZSM-5 zeolites were prepared by using silica extracted from rice hull ash as a raw material. • XRD, FTIR, nitrogen adsorption-desorption and SEM, were used to characterize the crystal and microstructure of zeolites. • The equilibrium adsorption amount of NaA-RS, NaX-RS and NaZSM-5-RS was 1.46, 3.12 and 2.20 mmol/g, respectively. • The CO 2 /N 2 adsorption selectivity and Henry's law constant were calculated to demonstrate the stronger affinity for CO 2. • The heat of adsorption was calculated, and its effect on the adsorption capacity and reaction was investigated. [ABSTRACT FROM AUTHOR]

In this study, Monascus pigments were separated from the extractive fermentation broth by the combination of reverse micellar extraction and macroporous resins (MACR) adsorption with the alkalizing S-8 MACR (S-8 ALR). A 95.07% pigment adsorption was achieved together with a relative low Triton X-100 co-adsorption that was only 2.53%. The liquid intraparticle diffusion and film diffusion limit the pigment adsorption rate. A 79.48-84.03% of the pigment could be eluted from the resin using the methanol solution containing a 0.5% (w/v) hydrochloric acid. The S-8 ALR could be recovered for cycle use without a deficit of the adsorption or desorption efficiency. Abbreviations: ACR—Acidified resin; ALR—Alkalizing resin; HPLC—High performance liquid chromatography; PSM—pigment- surfactant micelle; TEM—Transmission electron microscopy. [ABSTRACT FROM AUTHOR]

An environmentally friendly and simple homogeneous precipitation method synthesized MgO nanoparticles with highly efficient fluorine removal. The prepared MgO nanoparticles have an average size of 53 nm, the composition and structure of MgO nanoparticles were analyzed by XRD, SEM, TEM, STEM and BET. The high specific surface area (242.6 m2/g) and abundant pores (1.18 cm3/g) of MgO nanoparticles contribute to the increase of adsorption sites. The adsorption properties of MgO nanoparticles for fluorine were investigated by discussing the adsorption kinetics, isotherms and thermodynamics, the outcomes demonstrated that the Pseudo-second-order kinetics, Langmuir isotherm model and Freundlich model could describe the adsorption behavior for fluorine, and the maximum adsorption capacity is 372.65 mg/g. The Gibbs free energy change G°< 0 at different temperatures proves that the adsorption for fluorine by MgO is endothermic and spontaneous. In addition, the findings from FT-IR, XRD, XPS and hydrochemical equilibrium analysis demonstrate that the substances that play an adsorption role in MgO nanoparticles, and analyzed the reason why MgO nanoparticles have better adsorption properties than commercial MgO. Moreover, the environmental factors such as pH (3−10) and coexisting ions (Cl-, NO 3 2-, SO 4 2-, HCO 3 -, CO 3 2-, PO 4 3-) that may affect adsorption property in practical applications are also explored. The separation percentage of the adsorbent from the aqueous solution after adsorption indicates that it can be easily separated from water by filtration. Hence, the MgO nanoparticles in this study can be considered as a fluorine adsorbent with great potential. [Display omitted] • Using a clean and low-energy-consumption precipitation method prepared MgO nanoparticles with an average size of 50.3 nm. • The maximum adsorption capacity of MgO nanoparticles for fluoride reached a new high value of 372.65 mg/g. • It is found that MgO nanoparticles have better adsorption properties than commercial MgO. • The substances that play an adsorption role in MgO nanoparticles are mainly Mg2+ and MgOH+ formed by the reaction of MgO and water. • MgO nanoparticle adsorbents can be easily separated from water by filtration. [ABSTRACT FROM AUTHOR]

The adsorption rate, capacity, affinity of CH 4 and CO 2 in the competitive adsorption system are controlled by their adsorption thermodynamic and kinetic property. In this work, the experimental results of isothermal adsorption and adsorption kinetic experiments at different temperature and pressure are utilized to investigate the thermodynamic and kinetic mechanism of the adsorption difference between CH 4 and CO 2. Ten thermodynamic models and seven kinetic models are employed to fit the experimental data, and the thermodynamic and kinetic parameters obtained from the fitting process are used to characterize the diffusion ability, adsorption rate, adsorption capacity, adsorption strength, spontaneity of adsorption, difficulty of adsorption, and driver of adsorption in the gas adsorption process. Furthermore, their difference between CH 4 and CO 2 , temperature and pressure sensitivity, and the influence of shale property and pore structure are discussed to clarify the thermodynamic and kinetic mechanism of the higher adsorption affinity of CO 2. Results show that (i) the ability of CO 2 entering shale pores and contacting adsorption sites is greater than CH 4 , (ii) the adsorption capacity and adsorption strength of shale to CO 2 is higher, (iii) the adsorption of gas is spontaneous and enthalpy-driven, (iv) the selective coefficient of CO 2 relative to CH 4 decreases with higher experimental pressure and temperature and is caused by the higher pressure and temperature sensitivity of its thermodynamic and kinetic property. Results of this work are of specific reference for research on the adsorption thermodynamic and kinetic behavior of gases and designing schemes of CO 2 injection into shale gas reservoirs. • The adsorption of CH 4 and CO 2 are spontaneous and enthalpy-driven. • The adsorption intensity and spontaneity of CO 2 is greater than CH 4. • Complex pore structure is conducive to gases adsorption in shale reservoirs. • The adsorption thermodynamic and kinetic sensitivity of CO 2 is higher than CH 4. [ABSTRACT FROM AUTHOR]

Adsorption refrigeration has become an attractive technology due to the capability to exploit low-grade thermal energy for cooling power generation and the use of environmentally friendly refrigerants. Traditionally, these systems work with pure fluids such as water, ethanol, methanol, and ammonia. Nevertheless, the operating conditions make their commercialization still unfeasible, especially owing to safety and cost issues as a consequence of the working pressures, which are higher or lower than 1 atm. The present work represents the first thermodynamic insight in the use of mixtures for adsorption refrigeration and aims to assess the performance of a binary system of ammonia and ethanol. According to the Gibbs’ phase rule, the addition of a component introduces an additional degree of freedom, which allows to adjust the pressure of the system varying the composition of the mixture. The refrigeration process was simulated with isothermal- isochoric flash calculations to solve the phase equilibria, described by the Peng-Robinson-Stryjek-Vera (PRSV) equation of state for the vapor and liquid phases and by the ideal adsorbed solution theory (IAST) and the multicomponent potential theory of adsorption (MPTA) for the adsorbed phase. In operating condenser and evaporator, pressure levels around atmospheric pressure can be achieved using an ammonia/ethanol mixture with a mole fraction of ethanol in the range of 0.70−0.75. A good agreement in the predictions of the adsorbed phase composition was also reported using the IAST and the MPTA methods.

Spent coffee grounds are a waste generated in large amounts by the food industry producing instant coffee. While it is used as animal feed, mostly spent coffee grounds are burned. In this study, The spent coffee grounds were modified to be magnetic in order to remove cadmium (II) ion. The magnetic solids are easy to separate from water with a magnet. The biochar was prepared at 400 °C. Several factors that affect the adsorption were studied, such as adsorbent dosage, contact time, initial metal ion concentration and effect of solution pH. At the optimum conditions (the adsorbent dosage 0.1 g l ^−1 , pH 7, time 30 min and the initial concentration 40 mg l ^−1 ), the percentage removal of Cd(II) was ∼96%. The surface morphology of the adsorbent showed iron particles with a cubical shape on the adsorbent, with 3–20 μ m average diameter. The adsorption data was well fit by a pseudo-second order and a Langmuir isotherm, with the maximum adsorption capacity 10.42 mg/g. The adsorption process was spontaneous and endothermic. The main goal of the study is to re-use the spent coffee grounds waste and use low-cost adsorbent for cadmium (II) removal in aqueous solution. The magnetic biochar was easily manipulated by external magnetic fields after treatment. With good adsorbent performance of the magnetic biochar, spent coffee grounds could be used to treat Cd(II) contamination.

The adsorption isotherms and structural evolution of alkyl quaternary ammonium bromide (Cn TAB) on graphite oxide (GO) were measured by means of an elemental analyzer, X-ray diffraction and Fourier transform infrared spectroscopy. In order to interpret the adsorption mechanism of surfactants onto GO, the adsorption kinetics and thermodynamics were further investigated. It was found that GO is a relatively efficient adsorbent within a wide range of temperatures (297–353 K), and the Cn TAB was intercalated and then agglomerated into the interlayer spacing of GO via ionic bonding and hydrophobic bonding. The saturation amount of alkyl ammonium adsorbed on GO was decreased with the rise in temperature, and the experimental data fitted well into the modified Langmuir (Langmuir-Freundlich) equation. In addition, the negative values of ΔG and ΔH showed that the adsorption process of Cn TAB onto the GO was spontaneous and exothermic.

Copyright of Research of Environmental Sciences is the property of Research of Environmental Sciences Editorial Board and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A chelating fiber (CF), containing amine and hydroxyl groups, has been characterized and used as an adsorbent for the removal of U(VI) from aqueous solutions. The effects of pH value, contact time, adsorbent dosage, initial U(VI) concentration, temperature, and stripping agents on the adsorption behavior of U(VI) are studied. The results demonstrated that the maximum adsorption capacity is achieved at pH 3.0 and contact time 20 min. The adsorption behavior can be well described by the pseudo-second order kinetic and the Langmuir isotherm model equations. Additionally, it was found that the adsorbent can be reused for five repeating cycles. [ABSTRACT FROM AUTHOR]

The carbon dioxide adsorption behavior of synthesized chabazite-like M-SAPO-34 and modified with alkali metals (M = Li, Na, K, Cs), processed using volumetric method at different temperatures, was explored. The study allowed to see that the adsorption capacity increases according to the sequence: Na + > Li + > K + > Cs + , and all adsorption isothermal are type I according to Brunauer classification. Thermodynamic studies have been treated by the determination of the adsorption affinity, entropy and isosteric heat of these systems CO 2 -M-SAPO-34 with temperature variation between 273 and 298 K. The adsorption affinity shows the same trend for all the M-SAPO-34 at low coverage at 273 K. However, at high coverage, the isosteric heats of exchanged (H, Na, Li)-SAPO-34 present a homogeneous profile indicating dominance of adsorbate-adsorbate interaction. The differentials entropies were found to increase slightly with the coverage. Furthermore, the entropy of K-SAPO-34 at 273, exhibits values less than other exchanged M-SAPO-34. This Confirms pore blockage effect in the case of K-SAPO-34 and leads to reduction of free volume, while the Li-SAPO-34 shows the highest values of entropies with large free volume due to small size of Li + cation. [ABSTRACT FROM AUTHOR]

Abstract: The present review discusses the theory and application of van't Hoff analysis in chiral chromatography, with main focus on liquid chromatography. The topics considered include the physical meaning of van't Hoff equation's parameters, interpretation of thermodynamic data in terms of retention and enantioseparation mechanisms, abnormal behavior of van't Hoff plots, and best practices to avoid biased results. [ABSTRACT FROM AUTHOR]

Cu-BTC-Si02 was prepared by loading Cu-BTC into the mesoporous silica using in-si-tu synthesis method. The effects of Cu-BTC-Si02 on the adsorption of methylene blue at different temperatures, different methylene blue concentrations and different pH values were studied. At the same time, the adsorption kinetics and adsorption thermodynamics data were analyzed. The results show that the adsorption of methylene blue on the sample is in accordance with Langmuir adsorption isotherm model and quasi-first order kinetic model. The optimum reaction temperature is 25 °C, the dye concentration 5 mg/L, and the optimum pH value 5. The thermodynamic study finds that the adsorption behavior of methylene blue on Cu-BTC-SiO, is a spontaneous and exothermic process at the temperature between 25 - 45 °C. [ABSTRACT FROM AUTHOR]

Adsorption capacity of three antimicrobial terephthaloyl thiourea cross-linked chitosan hydrogels for Congo red dye removal from its aqueous solution has been investigated for the first time in this work. These hydrogels were prepared by reacting chitosan with various amounts of terephthaloyl diisothiocyanate cross-linker. The effect of the hydrogel structural variations and several dye adsorption processing parameters to achieve the best adsorption capacity were investigated. The hydrogels' structural variations were obtained by varying their terephthaloyl thiourea moieties content. The processing variables included initial concentration of the dye solution, temperature and time of exposure to the dye. The adsorption kinetics and isotherms showed that the sorption processes were better fitted by the pseudo-second-order equation and the Langmuir equation, respectively. On the basis of the Langmuir analysis Congo red dye gave the maximum sorption capacity of 44.248 mg/g. The results obtained confirmed that the sorption phenomena are most likely to be controlled by chemisorption process. The adsorption reaction was endothermic and spontaneous according to the calculated results of adsorption thermodynamics. [ABSTRACT FROM AUTHOR]

This study investigated the efficiency of rice husk carbon (RHC) for lead (Pb (II)) adsorption. The developed RHC was characterized by CHNS analyser, FTIR and FESEM. BET surface area, micropore area, micropore volume and average pore diameter of RHC were 58.54 m/g, 14.53 m/g, 0.007209 mL/g, and 45.46 Å, respectively. Batch adsorption experiments were conducted to assess the effect of initial pH, contact time, initial Pb (II) concentration and RHC dose on Pb (II) removal. A contact time of 120 min and a pH value of 5 were found as optimum for Pb (II) adsorption; maximum adsorption occurred at 8 g/L of RHC dose. Artificial neural network (ANN) was applied to model Pb (II) adsorption. For prediction of Pb (II) adsorption from aqueous solution by RHC, the smallest mean square error (MSE) and the largest coefficient of determination (R) values were, respectively, obtained as 6.0053 and 0.988567 with Levenberg-Marquardt algorithm (LMA). Hence, it was selected as the best training algorithm. Traincgf and traincgp functions followed this function with a MSE of 6.1496 and 6.2967, respectively. Adsorption of Pb (II) by RHC followed pseudo-second-order kinetics. The experimental data were described well by both Langmuir and Freundlich isotherm models. Thermodynamics study revealed that Pb (II) adsorption by RHC was spontaneous and endothermic, and the system randomness increased during the whole process. Pb (II) adsorption capacity of RHC was compared with different adsorbents. As evidenced by its high adsorption capacity, RHC can be used as an effective adsorbent for Pb (II) removal from aqueous solutions and wastewaters. [ABSTRACT FROM AUTHOR]

Weizmannia coagulans with high temperature tolerance and stability was selected for the production of exopolysaccharides (EPS) at the fermentation temperature of 52 °C. The weak basic anion exchange resin was employed in the fermentation for the construction of buffer system to neutralize some lactic acid and form intermolecular hydrogen bonds with hydroxyl groups on capsular polysaccharides of bacteria via tertiary amine groups, resulting in the increased growth space for capsular polysaccharides. In addition, the fermentation at relatively high temperature significantly decreased the adsorption of Ca2+ derived from CaO used for pH adjustment to the resin and sustained the ion exchange capability of the resin available for the formation of intermolecular hydrogen bonds with capsular polysaccharides. The concentration of EPS obtained achieved up to 19.8 g/L, which was increased by approximately 20-fold as compared to the concentration of EPS obtained by conventional fermentation. The conversion rate of carbohydrates to EPS reached up to 35.1%. The EPS produced under the optimized fermentation condition included neutral and acidic heteropolysaccharides with a molecular mass of 3.4 × 104–1.5 × 106 Da. The concentration and molecular mass distribution of EPS exhibited good reproducibility. This study provides a novel method for the industrial production of EPS. • It is the first that anion exchange resins were employed for EPS production. • Total ion exchange capacity and pH were the key parameters for EPS production. • The concentration of EPS was dramatically increased up to 19.8 g/L. [ABSTRACT FROM AUTHOR]

[Display omitted] • An H-substituted lithium manganese oxide-sepiolite composite (HMO-SEP) was prepared. • HMO-SEP has a microsphere structure with a specific surface area of 46.49 m2/g. • Sepiolite could improve the microstructure and ion transport channels of HMO-SEP. • HMO-SEP has high adsorption capacity and excellent selective adsorption for Li+. • Li+ sorption by HMO-SEP is a spontaneous endothermic process with increasing entropy. A novel spherical structure, hydrogen-substituted lithium manganese oxide (LMO)-sepiolite (HMO-SEP) composite assembled from nanorods was fabricated via hydrothermal method combined with solid-phase method. The structure and composition of the as-prepared HMO-SEP was analyzed by a series of characterization techniques, and its adsorption behavior and characteristics for Li+ adsorption from aqueous media and recyclability were investigated in detail. The as-prepared HMO-SEP showed a typical IV-type gas adsorption isotherm with H3-type hysteresis loop at high P / P 0 , with a specific surface area of 46.49 m2/g and a pore size of 18.31 nm. The isotherm adsorption data of Li+ adsorption by HMO-SEP conform well to the Langmuir model, and the maximum adsorption capacity of Li+ reached 52.41 mg/g at 298 K. Kinetic studies showed that the adsorption process complies well with the pseudo-second-order model, reaching adsorption equilibrium within 8 h. The adsorption of Li+ by the resulting HMO-SEP is a spontaneous endothermic process with increasing entropy, with an adsorption Δ H of 21.9432 kJ/mol and an adsorption activation energy of 19.8092 kJ/mol. A suitable amount of SEP could improve the microstructure of the HMO-SEP through the interface effect between SEP and LMO. Such effect could enlarge the specific surface area and pore volume and improve the ion transport channels, thus enhancing the adsorption capacity towards Li+, stability, and recycling performance. The resulting HMO-SEP possesses excellent selective adsorption performance for Li+, even under high concentrations of Na+, K+, Ca2+, and Mg2+, stability, and regeneration–recycling performance. It has excellent potential for efficient use in the extraction of Li+ from aqueous media. [ABSTRACT FROM AUTHOR]

• Activated biochar prepared from residues of palm tree Bactris guineensis. • High surface area and pore volume combined with excellent adsorption capacity of the drug propranolol hydrochloride. • The system tends to reach equilibrium in the 250 min and is well represented by the Avrami model. • With the maximum capacity obtained (161.3 mg g−1) at 328 K based on the Liu isotherm model. • Adsorption is favorable, spontaneous, and endothermic (ΔH0 = 7.403 kJ mol1). The production and consequently the consumption of the pulp of the fruit of the palm tree Bactris guineensis occurs extensively in Colombia. The majority of the fruit is formed by waste (peel and core), producing high residual biomass. Thus, it is necessary to find a practical utilization of these peels, making the production and consumption of the fruit of the palm tree Bactris guineensis highly sustainable. This study produced activated biochar chemically activated using ZnCl 2 and utilized it as an effective adsorbent. The high micropollutant uptake is because of the high porosity and good specific surface area (S BET = 625 m2 g−1). Under basic conditions, propranolol adsorption was favored for an adsorbent dosage of 0.7 g/L. The adsorbent showed fast kinetics, with the equilibrium influenced by the concentration. Avrami's model showed a satisfactory fit having a t 0.95 ranging from 47.8 to 179.3 min. Equilibrium data were best adjusted to the Liu isotherm model. The values of Q max increased with the temperature, reaching up to 161.3 mg g−1 (45 °C). The thermodynamic data showed ΔG° < 0 for 298–328 K (adsorption process favorable) ΔH°= + 7.403 kJ mol−1 (endothermic; magnitude compatible with physical adsorption), and ΔS°= +115.2 J K−1 mol−1 (releases of water molecules of the adsorbate before it being adsorbed in the carbon surface). The biochar chemically activated with ZnCl2, produced from the leftover peels of Colombian palm fruits, is therefore inferred to be a promising option as an adsorbent for the treatment of effluents containing the medication propranolol hydrochloride. [ABSTRACT FROM AUTHOR]

Nano-Mg(OH)2, with low biological toxicity, is an ideal nano-carrier for insecticidal protein to improve the bioactivity. In this work, the adsorption features of insecticidal protein by nano-Mg(OH)2 have been studied. The adsorption capacity could reach as high as 136 mg g−1, and the adsorption isotherm had been fitted with Langmuir and Freundlich models. Moreover, the adsorption kinetics followed a pseudo-first or -second order rate model, and the adsorption was spontaneous and an exothermic process. However, high temperatures are not suitable for adsorption, which implies that the temperature would be a critical factor during the adsorption process. In addition, FT-IR confirmed that the protein was adsorbed on the nano-Mg(OH)2, zeta potential analysis suggested that insecticidal protein was loaded onto the nano-Mg(OH)2 not by electrostatic adsorption but maybe by intermolecular forces, and circular dichroism spectroscopy of Cry11Aa protein before and after loading with nano-Mg(OH)2 was changed. The study applied the adsorption information between Cry11Aa and nano-Mg(OH)2, which would be useful in the practical application of nano-Mg(OH)2 as a nano-carrier.

This study presents the kinetic and thermodynamic investigation of the adsorption of crystal violet (CV) on used black tea leaves (UBTL) from aqueous solution to evaluate the feasibility of the process. The effects of concentration, solution pH and temperature on adsorption kinetics were carried out in batch process. Kinetic studies have shown that the adsorption data partially follow simple first order, second order and pseudo second order kinetic equations for different initial concentrations at pH 2.0. The equilibrium amount adsorbed, equilibrium concentration and rate constant were calculated from better fitted pseudo second order kinetic plots for different initial concentrations. The equilibrium amount adsorbed (200 mg/g at 30 oC) increased with the increase of temperature, indicated endothermic nature of the adsorption. The apparent activation energy of adsorption was determined from Arrhenius plot using pseudo second order rate constant and the value, Ea = 83.1 kJ/mol, revealed the process is chemisorption. Thermodynamic parameters: DHo, DGo and DSo, were determined from the equilibrium adsorption constant and the results obtained confirmed that the adsorption process was feasible, less spontaneous and endothermic. The equilibrium amount adsorbed was found to be increased with increase of solution pH from 2.0 to 6.0 indicating electrostatic interaction between cationic CV with anionic surface of UBTL dominated at higher pH due to the low zero point charge of pH of UBTL.

Four slow pyrolyzed biochars produced from wood (WDB), corncobs (CCB), rice husks (RHB) and sawdust (SDB) were evaluated for adsorption, desorption and regeneration of phosphate (PO 4 3− -P) from anaerobically digested liquid swine manure. The PO 4 3− -P adsorption capacity increased followed by initial concentrations increasing. Maximum PO 4 3− -P adsorptions at initial 150 mg/L of PO 4 3− -P (highest load) were average of 7.67, 6.43, 5.73 and 5.41 mg/g for WDB, CCB, RHB and SDB, respectively. Pseudo second order kinetics model could best fit PO 4 3− -P adsorption, which indicated the chemisorption via precipitation was the main mechanism for PO 4 3− -P removal. The sorption process was reversible and the adsorbed PO 4 3− -P could be desorbed in both neutral (57–78%) and acidic solution environments (75–88%) for all biochars. Meanwhile, regenerated biochar could re-adsorb up to 5.62 mg/g at the highest initial PO 4 3− -P of 150 mg/L. The present finding implied biochar could be effectively used to recover PO 4 3− -P from anaerobic digestate. [ABSTRACT FROM AUTHOR]

The rise in mean atmospheric temperature resulting from the emissions of greenhouse gases, especially CO 2 , has become a widespread concern in the recent years. This awareness of increase in greenhouse gas emissions has resulted in the development of new technologies which would lower emissions of CO 2 from flue gases. The purpose of this study is to investigate the performance of bubbling fluidized bed for CO 2 adsorption to mitigate CO 2 from flue gas. Adsorption of CO 2 had been carried out onto zeolite 4A, zeolite 5A, zeolite 13X and activated carbon at a pressure up to 4 bars. The effects of adsorbent mass on breakthrough time, gas velocity, adsorption isotherm, thermodynamics and heat transfer characteristics were also investigated during the continuous operation of the bubbling fluidized bed. As flow rate increased, the breakthrough curves become steeper and reached the breakthrough quickly due to the residence time of the adsorbate in the column, which was long enough for adsorption equilibrium to be reached at high flow rate. The experimental data were fitted with isotherm models like Langmuir and Freundlich isotherm model. It was found that the Langmuir model fit well with the zeolites based adsorbent and Freundlich model fit well with activated carbon. The experimental results permitted the determination of adsorption capacities of the adsorbents and showed that there is an improvement in the adsorption capacity using fluidized bed due to a better gas solid contact as compared to conventional fixed bed. [ABSTRACT FROM AUTHOR]

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Adsorption kinetics and thermodynamics of cadmium onto lignite-derived humic acid and lignite-derived active carbon were investigated by batch experiments under different temperatures. The adsorption thermodynamic isotherms were fitted using Langmuir, Freundlich and Temkin models, the adsorption kinetics were fitted to pseudo-first-order, pseudo-second-order, Elovich, fractional power and intraparticle diffusion models. Thermodynamic studies showed that Temkin model displayed the most suitable model to describe adsorption of cadmium onto raw lignite, extracted humic acid and active carbon. Thermodynamic parameters indicated the adsorption process were spontaneous, favourable, and endothermic physical adsorption in nature. The equilibrium adsorption capacity of cadmium obtained from the Langmiur model for humic acid, lignite and active carbon was 36.14∼44.09, 29.63∼38.20 mg·g-1 and 21.04∼30.34 mg·g-1 respectively in the temperature range of 294.55 ∼313.15 K, adsorption capacity magnitudes increased with a rise of temperature, indicating more feasible adsorption at high temperature. Adsorption kinetics parameters showed that the pseudo-second-order model was better than the pseudofirst-order, Elovich, fractional power and the intraparticle diffusion models, this indicated that cadmium adsorption might be a physisorption associated with chemisorption process. According to the adsorption characteristics of kinetics, thermodynamics parameters such as change in free energy（ΔG）, change in enthalpy（ΔH）, and change in entropy（ΔS）, it was concluded that the adsorption process of cadmium onto these different adsorbents were spontaneous, endothermic, simultaneous physisorption and accompanied by chemisorption or alternatively physicochemical process. Adsorbents of humic acid had the great adsorption capacity and adsorption intensity. Temkin isotherm model and pseudo-second-order model could be the suitable models with good fitting for describing the adsorption properties of cadmium onto these adsorbents. Infrared spectra analysis showed that oxygen containing functional groups and unknown absorbance peaks at approximately 2 360, 2 342 cm-1 had important impact on Cd2+ adsorption. [ABSTRACT FROM AUTHOR]

This work studied the adsorption of chloramphenicol (CAP) on two types of biochars derived from reed straw (RSB) and municipal sewage sludge (SSB), which were prepared by pyrolyzing at 500°C. The biochars were characterized by scanning electron microscope, Fourier transform infrared spectroscopy, energy dispersive spectroscopy and Brunauer-Emmet-Teller. It revealed that RSB had a higher surface area (125.04 m²/g) than SSB (7.14 m²/g) and the adsorption of chloramphenicol on SSB (gm=1.171 mg/g, 308.15K) was much less than that on RSB (gm=6.586 mg/g, 308.15K). Adsorption kinetics of CAP on biochars followed pseudo second order kinetic model, and adsorption isotherm fitted well with Sips model. The adsorption kinetics and thermodynamics demonstrated that the adsorption of CAP on two biochars squinted towards chemical adsorption. The K-K electro-donor-acceptor interaction between nitro group, benzene ring in CAP and K electron on the surface of biochars played an important role in the adsorption of CAP on biochars, while the hydrogen bonding interaction also contributed to the adsorption of CAP on biochars synchro-nously. [ABSTRACT FROM AUTHOR]

Sorption equilibrium and kinetics of CO 2 , N 2 and CH 4 on a newly reported Zn-based metal organic framework (Zn 4 (pydc) 4 (DMF) 2 ·3DMF (1)) were studied to evaluate its efficacy for CO 2 capture under realistic post-combustion conditions. Adsorption and desorption equilibria were measured gravimetrically for temperatures between 308 K and 338 K and pressures up to 5 bar. The Langmuir adsorption model was used to fit sorption data and the Ideal Adsorbed Solution Theory (IAST) was used to calculate selectivity from single-component isotherms suggesting that separation can be enhanced by a decrease in temperature. The MOF exhibited preferential CO 2 adsorption based on the high enthalpy of adsorption and adsorption selectivities of CO 2 over N 2 and CH 4 . Kinetics of adsorption and desorption of CO 2 (308K–338 K, pressures up to 1 bar) were fitted to the linear-driving force (LDF) kinetic model, showing a relatively fast adsorption and a low activation energy for adsorption and desorption. Diffusion inside the pores was found to be the rate-limiting step based on fits to the LDF model and the micropore diffusion model. Desorption kinetics studies at 1 bar indicated that CO 2 has greater average residence times at all temperatures and lower values of activation energy for desorption than N 2 and CH 4 . This suggests the selective adsorption and capture of CO 2 on (1) will be favored. [ABSTRACT FROM AUTHOR]

Coal samples were collected from Huolinhe Coal mine in Inner Mongolia，China，and three kinds of particle size colloids (0-2，2-5，and 5-10 μm) were extracted. The batch experiments have been carried out to study the adsorption isotherm and thermodynamics of mercury on colloid from coal. The results show that the sorption was affected by temperature and particle size. When temperature rose，the sorption capacities of colloids from coal were increased. Sorption capacity was decreased as the increase of particle size. The data of sorption isotherm of mercury on colloid from coal was discussed using two kinds of the Dual Adsorption Partition models. The experimental data fitted the Dual Adsorption Partition model. For the colloids with sizes <5 μm，the adsorption is predominant in the sorption of mercury，which accounts for 64.1%-83.4% of the sorption. When the particle size is 5-10 μm，the accounts of the partition were 49.6-92.5.At the different temperatures，the contribution of adsorption to sorption follows the order “45 ℃”>“35 ℃”>“25 ℃”. The value of Gibbs free energy was negative，which showed that the reaction process was spontaneous. Sorption enthalpy was in a range from 24.5-86.1 kJ/mol，which indicated that the sorption process was endothermic. The change of entropy value was all positive，which showed that the sorption reaction was an increased randomness process. The adsorption of mercury on the colloid (0-2 μm) was mainly a chemical adsorption process，while on the colloids (2-5 μm and 5-10 μm) were mainly a physical adsorption process. [ABSTRACT FROM AUTHOR]

A new approach to constructing adsorption thermodynamics that provides the derivation of rigorous thermodynamic relationships for any adsorption system, particularly for a system with a deformable adsorbent, is proposed. Expressions for the thermodynamic functions of an adsorption system in the form of an arbitrary control volume containing the adsorbent and the adsorbed gas are derived. In the derived expressions, the role of adsorption is played by the total adsorbate content in the system. If the control volume boundaries are set appropriately, this quantity is identical to absolute adsorption. [ABSTRACT FROM AUTHOR]

Purified terephthalic acid (PTA) plant of a petrochemical unit generates wastewater having high pollution load. Acid treatment of this wastewater reduces the chemical oxygen demand (COD) load by more than 50%, still leaving substantial COD load (>1500 mg/L) which should be removed. The present study reports on the use of a bio-waste-adsorbent bagasse fly ash (BFA) for the reduction of COD and other recalcitrant acids from this wastewater. The BFA showed basic character and was mesoporous with a BET specific surface area of 82.4 m/g. Optimum conditions for the adsorptive treatment of acid-pretreated PTA wastewater were found to be as follows: initial pH (pH) = 4, BFA dosage = 15 g/L, and contact time = 3 h. Adsorption treatment resulted in 58.2% removal of COD, 96.3% removal of terephthalic acid (TA), and 99.9% removal of benzoic acid (BA). TA and BA were removed from the pretreated PTA wastewater through precipitation and sedimentation of un-dissociated acid molecules inside the mesopores of the BFA. The results showed that the COD removed by the BFA followed pseudo-second-order kinetics. Equilibrium sorption data were best correlated by the Freundlich isotherm. The process of adsorptive removal of COD was found to be exothermic. The change in the Gibbs free energy was found to be negative, suggesting that the adsorption process is spontaneous and feasible for the treatment of PTA wastewater. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Dalian University of Technology / Dalian Ligong Daxue Xuebao is the property of Journal of Dalian University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Amine-modified bentonite (TEPA-Bn) has been prepared with tetraethylenepentamine (TEPA) as a modifier. The structure of Ca-based bentonite (Ca-Bn), TEPA-Bn and TEPA-Bn after adsorbing Cu2+, Ni2+, Cd2+ had been characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and simultaneous thermal gravimetric/differential thermal gravimetric (TG/DTG) analysis. The TEPA had been intercalated into Ca-Bn interlayer space but had not changed its original crystal structure. The thermal stability of TEPA-Bn was stronger than Ca-Bn while the hydrophilicity of it reduced. The adsorption ability of TEPA-Bn to Cd2+, Ni2+, Cu2+ was much better than Ca-Bn, the saturated adsorption capacity to Cd2+, Ni2+, Cu2+ were 14.88, 8.88 and 13.05 times as much as Ca-Bn, respectively. The adsorption behavior of Cu2+, Ni2+, Cd2+ on to TEPA-Bn were studied by isothermal models, including Freundlich, Langmuir, Dubinin-Radushkevich Florry-Huggins, and Tempkin models. The Freundlich model simulated the experimental data best, the adsorption of Cu2+, Ni2+, Cd2+ onto TEPA-Bn was a multilayer, heterogeneous chemical process. The variety of thermodynamic parameters (ΔH > 0, ΔS > 0, ΔG < 0) under different temperature indicated that the adsorption process of Cu2+, Ni2+, Cd2+ on TEPA-Bn was endothermic and spontaneous. [ABSTRACT FROM AUTHOR]

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

As one of the most produced agricultural wastes, corncob is considered for the removal of metal ions from aqueous solution as a low-cost biosorbent. This study reports the preparation of polyacrylamide grafted corncob and its excellent adsorptivity for Cd(II) ions in aqueous solution compared with crude corncobs. The adsorbents were characterized with scanning electron microscopy, BET, Fourier transform infrared, thermo gravimetric analysis, and swelling study. The higher Cd(II) uptake of polyacrylamide grafted corncob than crude corncob was due to increased surface area and number of functional groups (–NH2) that could complex with metal ions. Higher thermal stability and better swelling property in salt solution were achieved for corncobs after grafting modification. Experimental data greed with the Langmuir isotherm, and maximal adsorption capacities of polyacrylamide grafted and crude corncobs were 18.35 and 4.96 mg g−1, respectively. Kinetics study revealed that adsorption followed pseudo-second-order kinetics, and that chemical sorption was the rate-controlling step. Thermodynamic parameters (free energy ΔG, enthalpy ΔHand entropy ΔS) showed that adsorption was a spontaneous endothermic process. [ABSTRACT FROM AUTHOR]

The adsorption of the anticoagulant warfarin onto unmodified (UMS) and modified (phenyl (PhMS), methyl (MMS), mercaptopropyl (MPMS)) mesoporous silica materials was studied at pH 1.6 and 7.4 and in the temperature range of 293–325 K. The silica materials were prepared by sol-gel method for further characterization by FTIR spectroscopy, N2adsorption/desorption method, transmission electron microscopy and zeta potential measurements. The effects of medium pH, temperature and surface modification of mesoporous silica material on their adsorption characteristics (adsorption capacity, thermodynamic parameters of adsorption) relative to anticoagulant warfarin were investigated. It was found that medium acid–base properties strongly affect the adsorption of warfarin due to the pH-dependent structural diversity of the drug and ionization state of the silica surfaces. The adsorption capacity of the silica materials at pH 1.6 decreases in the order: MMS > MPMS > UMS > PhMS. The influence of various non-covalent interactions on the adsorption capacity of the silica materials and energy of the drug-silica interactions is discussed. These results may be useful for the development of a novel delivery system of warfarin. [ABSTRACT FROM PUBLISHER]

BACKGROUND The performance of newly prepared fibrous boron selective adsorbent was investigated via equilibrium isotherms, kinetics and thermodynamics of boron adsorption from aqueous solutions. The adsorbent was obtained by radiation induced graft copolymerization ( RIGC) of vinyl benzyl chloride ( VBC) onto nylon-6 fibers followed by chemical treatment with N-methyl- D-glucamine ( NMDG). RESULTS The effect of solution pH on the boron adsorption capacity was investigated. The equilibrium adsorption data was fitted to the Langmuir, Freundlich and Redlich-Peterson isotherms, with the experimental data best fitting the Redlich-Peterson model. The kinetic data analyzed using the intra-particle diffusion model indicated that adsorption onto the fibrous chelating adsorbent is governed by a film diffusion mechanism. The thermodynamic adsorption parameters including the Gibb's free energy change (Δ Go), enthalpy change (Δ Ho) and entropy change (Δ So) were determined and the results indicated that adsorption onto the fibrous adsorbent occurs spontaneously. CONCLUSION The high adsorption capacity and rapid kinetics suggest that the newly prepared fibrous adsorbent could have strong potential for boron removal from aqueous solutions. © 2015 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Zero valent iron supported on mesoporous silicanano particles (NZVI/MSNs) was prepared by the aqueous phase borohydride reduction methods. Prior to the reduction, mesoporous silica nanoparticles (MSNs) were prepared through the activation of fumed silica with concentrated HCl by refluxing at 90 °C. FTIR, XRD, FESEM, EDX and BET were used to characterize theadsorbents prepared. BET surface areas of MSNs, NZVI, and NZVI/MSNs were 126, 41, and 72 m²/g for, respectively. The performance of NZVI/MSNs as adsorbent was examined by adsorption of methylene blue (MB), performed in series of batch experiments. In the kinetic studies, pseudo first order and pseudo second order kinetic models were examined. The pseudo second order equation provided the best fit with the experimental data. Thermodynamic studies indicated that the adsorption process is endothermic with ?H° was 90.53 kJ/mol. Positive ?S° (300 J/mol) and negative ?G° (-6.42 kJ/mol) was recorded, indicating the spontaneous of the adsorption process and naturally favorable. [ABSTRACT FROM AUTHOR]