Preparation and sorption studies of microsphere copolymers containing β-cyclodextrin and poly(acrylic acid)

Microsphere polymeric materials containing β-cyclodextrin (β-CD) and poly(acrylic acid) (PAA) with tunable morphologies were prepared in order to improve their sorption characteristics in aqueous solution. The microsphere polymeric materials were prepared using a (water/oil) micro-emulsion-evaporation technique to condense β-cyclodextrin (β-CD) with PAA at various comonomer ratios and mixing speeds. The β-CD microsphere copolymers were characterized using FTIR, TGA, DSC, SEM, elemental (C and H) microanalyses, and solid state ¹³C-NMR spectroscopy. The sorption properties of the polymeric materials at 295 K in aqueous solution containing p-nitrophenol (PNP) were studied using a dye-based method with UV–Vis spectrophotometry at pH 4.6 and 10.3. The sorption isotherms of copolymer/PNP systems were evaluated with various isotherm models (e.g., Langmuir, BET, Freundlich, and Sips). The Sips isotherm showed the best overall agreement with the experimental results and the sorption parameters provided estimates of the sorbent surface area (12.0–331 m²/g) and the sorption capacity (Q_m = 0.359–2.20 mmol/g at pH = 4.6; Q_m = 0.070–0.191 mmol/g at pH = 10.3) for the microsphere copolymer/PNP systems in aqueous solution. The nitrogen adsorption properties of the microporous copolymers in the solid state were obtained at 77K with BET surface areas ranging from 0.275 to 4.47 m²/g. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

MODELING WATER SORPTION IN OKARA SOY MILK

ABSTRACT

Moisture sorption isotherms of okara soy milk were determined using the gravimetric method in the range 20 - 50 °C. The sorption isotherms exhibited hysteresis along all the water activity range (0·1 - 0·9). The amount of sorbed water increased as the temperature was decreased. The GAB and Halsey models gave a good fit for okara isotherms over the range of water activity 0·1 - 0·9. As temperature increased, GAB k-values increased towards unity where the GAB equation reduces to the BET equation. The influence of temperature on the constants of GAB and Halsey models was evaluated through Arrhenius-type equations. The Clausius Clapeyron equation was used to estimate the isosteric heats of sorption.     

Sorption of binary gas mixtures in zeolites: I. Sorption of nitrogen and carbon dioxide mixtures in silicalite

The adsorption of pure CO₂ and N₂ gases, and their mixtures have been determined on a very high silica form of the zeolite ZSM-5 using a newly developed isosteric technique. Unlike more traditional methods, this method allows one to measure mixture isotherms at fixed sorbed phase composition. The shape of the mixture isotherms and the isosteric heats of sorption for the mixture have been identified as functions of the equilibrium gas phase composition, which itself is a temperature dependent function of the sorbed phase composition. None of the isotherms approached saturation at the temperatures and pressures used. The ratio of Henry's constants for the two pure gases gives a reasonable estimate of the separation factor measured experimentally. Selective sorption of CO₂ is marked even at 70°C. Binary mixture sorption isotherms predicted from pure gas data using the ideal adsorbed solution (IAS) theory, are shown to be in close agreement with the experimental data.     

Thermodynamics aspect of tannin sorption on polymeric adsorbents

Hypercrosslinked polydivinylbenzene and gel type poly(styrene-co-divinylbenzene) post-crosslinked with isocyanuric acid and macroporous crosslinked poly (N-vinyl acetamide) adsorbent were prepared for adsorbing tannin from aqueous. The sorption isotherms were measured and the isosteric enthalpy was quantitatively correlated with the fractional loading for the tannin sorption onto the three polymeric adsorbents. Surface energetic heterogeneity was observed for the three adsorbents and described with the functions of isosteric enthalpy. The causative factors of the surface heterogeneity of the adsorbents and the mechanism of tannin sorption onto the adsorbents from aqueous were discussed. It was suggested that multiply hydrogen bonding, π-π interaction and hydrophobic interaction were involved in tannin adsorption onto the polymeric adsorbents.     

Adsorption of Carbon Dioxide on High-Silica Zeolites with Different Framework Topology

Adsorption isotherms of carbon dioxide were measured on six high-silica zeolites TNU-9, IM-5, SSZ-74, ferrierite, ZSM-5 and ZSM-11 comprising three-dimensional 10-ring (8-ring for ferrierite) at 273, 293, 313 and 333 K. Based on the known temperature dependence of CO₂ adsorption, isosteric heats of adsorption were calculated. The obtained adsorption capacities and isosteric adsorption heats related to the amount of CO₂ adsorbed have provided detailed insight into the carbon dioxide interaction with zeolites of different framework topology. The zeolites TNU-9 and ferrierite are characterized by pronounced energetic heterogeneity whereas due to the location of Na⁺ cations in the same positions the isosteric adsorption heats of CO₂ adsorption on IM-5, ZSM-5 and ZSM-11 zeolites are rather constant for molecular ratio CO₂/Na⁺ < 1. As IM-5 zeolite has a maximum adsorption capacity, it appears to have optimum properties for carbon dioxide separation.     

Investigation of α‐iron oxide‐coated polymeric nanocomposites capacity for efficient heavy metal removal from aqueous solution

In the present study, PS@α‐Fe₂O₃ nanocomposites were prepared by chemical microemulsion polymerization approach and the ability of magnetic beads to remove Cu(II) ions from aqueous solutions in a batch media was investigated. Various physico‐chemical parameters such as pH, initial metal ion concentration, temperature, and equilibrium contact time were also studied. Adsorption mechanism of Cu²⁺ ions onto magnetic polymeric adsorbents has been investigated using Langmuir, Freundlich, Sips and Redlich–Petersen isotherms. The results demonstrated that the PS@α‐Fe₂O₃ nanocomposite is an effective adsorbent for Cu²⁺ ions removal. The Sips adsorption isotherm model (R² > 0.99) was more in consistence with the adsorption isotherm data of Cu(II) ions compared to other models and the maximum adsorbed amount of copper was 34.25 mg/g. The adsorption kinetics well fitted to a pseudo second‐order kinetic model. The thermodynamic parameters (ΔH°, ΔS°, and ΔG°) were calculated from the temperature dependent sorption isotherms, and the results suggested that copper adsorption was a spontaneous and exothermic process. POLYM. ENG. SCI., 55:2735–2742, 2015. © 2015 Society of Plastics Engineers     

Sorption of N2, CH4 and CO2 in Silicalite-1

An isosteric sorption apparatus has been used to obtain data for the sorption of N₂, CH₄ and CO₂ in Silicalite-1 over the temperature range 0–70°C. Isotherms have also been determined in a high pressure sorption balance at equilibrium pressures up to 20 atm. Isosteric heats of sorption have been calculated from these sorption data. Separation factors calculated from Henry's Law constants determined from the initial slopes of the single-component isotherms have been found to be in good agreement with experimental separation factors. The single-component sorption data have been fitted to various isotherm models and the Ideal Adsorbed Solution theory has been used to predict a binary sorption isotherm from the respective single-component data. The predicted isotherm is in good agreement with the corresponding experimental isotherm.     

Thermodynamic and NMR investigations on the adsorption mechanism of puerarin with oligo‐β‐cyclodextrin‐coupled polystyrene‐based matrix

BACKGROUND: Adsorption of puerarin on native resin polystyrene (PS) and oligo‐β‐cyclodextrin‐coupled matrix (PS‐CDP) was studied for interactions between the adsorbents and the adsorbates. The sorption mechanism on PS‐CDP was investigated using the isosteric heat approach and nuclear magnetic resonance (NMR) spectroscopy. RESULTS: The equilibrium adsorption data of puerarin on the two matrices PS and PS‐CDP (polystyrene‐based matrix before and after coupling by oligo‐β‐cyclodextrin) in the temperature range 288–318 K were well fitted to the Freundlich adsorption isotherm model. The energetic heterogeneity of the media was observed based on the result that the values of isosteric enthalpy were quantitatively correlated with the fractional loading of puerarin adsorption. The more heterogeneous surface of PS‐CDP compared with PS was attributed to the complexation between puerarin and β‐cyclodextrin (β‐CD). NMR studies validated the formation of an inclusion complex puerarin/β‐CD. CONCLUSION: Thermodynamic and NMR studies confirmed that multi‐interaction cooperatively governed the isolation of puerarin from aqueous solution on PS‐CDP matrix. Copyright © 2009 Society of Chemical Industry     

Preparation and sorption properties of tunable polyester copolymers containing β‐cyclodextrin

Polyester copolymers were prepared with β‐cyclodextrin (β‐CD) and sebacoyl (SCl) or terephthaloyl (TCl) chloride cross linker agents using a simple, one‐pot synthesis. Variation of the mole ratios (i.e., 1 : 1, 1 : 2, 1 : 3, 1 : 6, and 1 : 9) of β‐CD to diacid chloride linker units resulted in copolymers with differing solubility and chemical stability in aqueous solution. The sorption properties of copolymers such as 1 : 6 and 1 : 9 SCl, and 1 : 9 TCl materials were investigated because of their relative insolubility and resistance to hydrolysis at pH 4.6. The monolayer sorption capacity (Q_m) of the copolymers varied according to the nature of the cross linker and the relative mole ratio of monomers. Q_m values obtained from the Sips isotherm model range from 2.7 to 5.2 mmol/g for the sorption of p‐nitrophenol at 295 K and approach the value of Q_m for a commercially available granular activated carbon sorbent. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Production of fructooligosaccharides by β‐fructofuranosidase from Aspergillus sp 27H

β‐fructofuranosidase (EC 3.2.1.26) from Aspergillus sp 27H isolated from soil was investigated for production of fructooligosaccharides (FOS) using whole cells. It possesses hydrolytic and transfructosylating activities that can be altered by modifying the reaction conditions. The optimal conditions for the transfructosylating activity occur in the pH range 5.5–6.0 and at 60 °C, while hydrolytic activity was highest at pH 4.0 and 55 °C. At low sucrose concentration (10 g dm^?3) there was rapid conversion of sucrose to glucose and fructose and very low concentrations of FOS were obtained. However, at sucrose concentrations higher than 216 g dm^?3 the concentrations of hydrolysis products were reduced. Under the following conditions: pH 5.5, temperature 40 °C, sucrose concentration 615 g dm^?3 and enzyme concentration 20β‐fructofuranosidase units g^?1 of sucrose, the FOS concentration reached a maximum value of 376 g dm^?3 (234 g dm^?3 1‐kestose and 142 g dm^?3 nystose) and the proportion of FOS in the solids in the reaction mixture was 600–620 g kg^?1 at 6 h. These results suggest that β‐fructofuranosidase from Aspergillus sp 27H could be an appropriate enzyme for the commercial production of FOS. Copyright © 2004 Society of Chemical Industry     

Experimental Determination and Modeling of Sorption Isotherms of Tropical Fruits: Banana,Mango, and Pineapple

Abstract

Sorption isotherms of banana, mango, and pineapple have been experimentally found at 40, 50, and 60°C by use of the salt method for a range of water activities from 0.056 to 0.85. The sorption capacity of these fruits increases with the temperature for a given water activity. The experimental curves have been simulated by the GAB and BET models. The BET model ensures a better representation of the experimental results for water activity lower than 0.35 with maximum deviation of 1.0, 1.5, and 2.0 kgw · kgdm^?1 for respectively banana, mango and pineapple. On the contrary, the GAB model enables the representation of the whole desorption isotherms and the estimation of the water content corresponding to monolayer saturation and of the isosteric heat of sorption. It also takes into account the temperature effect. The isosteric sorption heat of the three studied products are deduced from experimental results and empirical correlations are proposed leading to a satisfactorily representation.     

DETERMINATION OF MOISTURE DESORPTION ENTHALPY OF MESQUITE GUM WITH DIFFERENTIAL SCANNING CALORIMETRY AND THERMOGRAVIMETRIC ANALYSIS

Moisture sorption isotherms were determined for mesquite gum at 25, 35 and 45 ° C. The water desorption enthalpy was calculated from the isotherms with the Clausius-Clapeyron equation, and additionally by both different scanning calorimetry and thermogravimetric analysis. The two calorimetric techniques showed greater degree of water binding al the product surface at the lower moisture contents. There was a decrease in desorption enthalpy when moisture conlenl was increased. Negative enthalpy values suggested an endothermic reaction probably attributed to biopotymer solution. Results indicated that calorimetric and thermogravimetric analyses are suitable physical methods to estimate isosteric heats of mesquite gum.     

Evaluation of the Sorption Equilibrium and Effect of Drying Temperature on the Antioxidant Capacity of the Jaboticaba (Myrciaria cauliflora)

In recent years, interest toward berries has increased (e.g., Myrciaria cauliflora or jaboticaba) because of their high phenolic content (phenolic acids, flavonoids, and anthocyanins) that has been associated with positive effects on consumer health and which play an important role in the antioxidant properties of food. This study analyzed the sorption isotherms, thermodynamic properties of sorption (isosteric heat and Gibbs free energy), and the evolution of the antioxidant capacity during the drying process. The effects of drying temperatures of 40°, 50°C, and 60°C on the antioxidant capacity and thermodynamic properties of sorption were evaluated. The gravimetric static method for sorption isotherm determination over a range of relative humidity levels from 0.10 to 0.90 was used. The sorption isotherms exhibited a Type II behavior, typical for many foods. The Guggenheim, Anderson, and Boer (GAB); Oswin; Peleg; and Lewicki models were used to fit the experimental data, and it was determined that the GAB and Peleg models were most appropriate for describing the sorption curves. The isosteric heat and Gibbs free energy were obtained from the experimental sorption equilibrium. The isosteric heat of adsorption decreased when the moisture content increased, while the Gibbs free energy increased. In addition, the phenolic content and antioxidant capacity increased while drying at 50°C and 60°C, whereas these factors decreased at 40°C. Our results provide the food industry with information concerning the best drying conditions to preserve antioxidant properties.     

A thermodynamic investigation of adsorbate‐adsorbate interactions of carbon dioxide on nanostructured carbons

A thermodynamic study of carbon dioxide adsorption on a zeolite‐templated carbon (ZTC), a superactivated carbon (MSC‐30), and an activated carbon (CNS‐201) was carried out at temperatures from 241 to 478 K and pressures up to 5.5?10⁶ Pa. Excess adsorption isotherms were fitted with generalized Langmuir‐type equations, allowing the isosteric heats of adsorption and adsorbed‐phase heat capacities to be obtained as a function of absolute adsorption. On MSC‐30, a superactivated carbon, the isosteric heat of carbon dioxide adsorption increases with occupancy from 19 to 21 kJ?mol^?1, before decreasing at high loading. This increase is attributed to attractive adsorbate–adsorbate intermolecular interactions as evidenced by the slope and magnitude of the increase in isosteric heat and the adsorbed‐phase heat capacities. An analysis of carbon dioxide adsorption on ZTC indicates a high degree of binding‐site homogeneity. A generalized Law of Corresponding States analysis indicates lower carbon dioxide adsorption than expected. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1026–1033, 2018     

Letter to the Editor

Abstract

The water sorption isotherms of the Erythrina fusca Lour bark at 30 and 40°C were determined over relative humidity ranging from 55 to 85%. The equilibrium moisture content was determined gravimetrically. The moisture sorption isotherms showed that the equilibrium moisture decreases with increase of temperature. Six models were used for to fit the experimental curves of equilibrium humidity. Parameters of each equation were determined by nonlinear regression analysis. The isosteric heat of moisture sorption was calculated using the Claussius-Clapeyron equation.     

Equilibrium,Kinetic, and Thermodynamic Analysis of Cd(II) Sorption from Aqueous Solutions using Polymeric Microcapsules containing an Acidic Organophosphonic Extractant

The equilibrium, kinetics, and thermodynamics of Cd(II) sorption from aqueous solutions onto polymeric microcapsules has been studied. Microcapsules were prepared by immobilizing an acidic organophosphonic extractant in a polymeric matrix prepared from styrene and ethylene glycol dimethacrylate following in situ free-radical suspension polymerization. Scanning electronic microscopy showed that the microcapsules were spherical and exhibited a rough surface with an average BET surface area of 12–20 m² g^?1 and an approximate pore size of 7.0 nm. The microcapsules were contacted with aqueous solutions containing Cd(II) approximately 100 mg L^?1 at an initial pH = 4.0 to study their sorptive behaviour over a temperature range of 293–323 K. The results of equilibrium experiments showed that the results filled the Langmuir isotherm model. The experimental kinetics followed a pseudo-second order model with an activation energy of 47.1±2.2 kJ mol^?1. Thermodynamics measurements showed that sorption is spontaneous and exothermic and that entropy had a negative value.     

MODELING WATER SORPTION IN OKARA SOY MILK

Moisture sorption isotherms of okara soy milk were determined using the gravimetric method in the range 20 - 50 °C. The sorption isotherms exhibited hysteresis along all the water activity range (0·1 - 0·9). The amount of sorbed water increased as the temperature was decreased. The GAB and Halsey models gave a good fit for okara isotherms over the range of water activity 0·1 - 0·9. As temperature increased, GAB k-values increased towards unity where the GAB equation reduces to the BET equation. The influence of temperature on the constants of GAB and Halsey models was evaluated through Arrhenius-type equations. The Clausius Clapeyron equation was used to estimate the isosteric heats of sorption.     

Behaviour and mechanism of enhanced phosphate sorption on loess modified with metals: equilibrium study

BACKGROUND: Phosphate is one of the main contaminants responsible for the eutrophication of surface waters. In developing countries, algae blooming in lakes have threatened the quality of drinking water due to the lack of proper management of phosphate‐containing wastewaters from mining sites and industry. MAJOR RESULTS: The sorption behaviour of phosphate on loess modified by metals (Zn(II), Cu(II) and Pb(II)) was investigated in this paper. Zn(II) and Cu(II) sorption on the loess was attributed to the constituent silicate minerals while the sorption of Pb(II) was assigned to natural carbonate in the loess. The sorption affinity of phosphate towards the modified sorbent was as follows: Pb(II) (221.3–832.2 L g⁻¹) > Cu(II) (20.26 L g⁻¹) > Zn(II) (0.77–1.90 L g⁻¹) > loess (0.11 L g⁻¹) with regard to the partition coefficient. The sorption isotherms were well fitted by an extended Henry's law with multi‐linearity. Several factors including metal loading, pH, sorbent dosage and temperature were investigated and all were found to correlate positively with phosphate sorption. The enthalpy and entropy changes during phosphate sorption on Pb(II) loaded loess were predicted as 14.32 kJ mol⁻¹ and 128.45 J mol⁻¹ K⁻¹, respectively. The sorption mechanism for phosphate on Pb(II) doped loess was investigated by FT‐IR spectra from which the sorption was attributed to chemical bonding with lead carbonate and physisorption with surface adsorbed phosphate as well as diffusion through micropores into the sorbent. CONCLUSIONS: Pb(II) loaded loess shows the best performance for phosphate removal from aqueous solution. The optimum conditions for sorption were pH = 9.5, lead modified loess sorbent dosage = 10 g L⁻¹, temperature = 35 °C and Pb(II) loading 295 mg g⁻¹. Copyright © 2008 Society of Chemical Industry     

Adsorption and drug release based on β‐cyclodextrin‐grafted hydroxyapatite composite

In this study, β‐cyclodextrin (β‐CD) was covalently grafted on hydroxyapatite (HA) using a coupling agent to improve the drug loading capacity and prolong the drug release. The binding of β‐CD on the HA surface was confirmed by Fourier transformation infrared spectroscopy, thermal gravimetric analysis, and X‐ray powder diffraction. The adsorption capacity of ofloxacin on β‐CD‐grafted hydroxyapatite (β‐CD‐g‐HA) composite was found to be 30 mg g^?1 at 37°C and 24 h. The adsorption process is spontaneous, given the negative values of free energy change. Compared with the release of ofloxacin loaded on HA, the release of ofloxacin loaded on β‐CD‐g‐HA was slowed down 28% and 21% in pH 2.0 and pH 7.4 buffer media at 2 h, respectively. Biocompatibility of β‐CD‐g‐HA was assessed by MTT assay, and the result showed that it had no cytotoxicity. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Thermodynamic and sorption behavior of U(VI) and Th(IV) on unsaturated polyester–styrene polymeric beads

The sorption behavior of Th(IV) and U(VI) species on two batch molds of radiation‐induced polymerized unsaturated polyester beads containing 40 wt % styrene was investigated. The distribution coefficients of both ions on the polymeric sorbents were evaluated at 30°C using 10^?4 M solution and found to be 271.9 and 469.8 mL/g on the first mold and 296 and 1189.2 mL/g on the second mold for Th(VI) and U(IV), respectively. Testing the sorption data using different theories provided evidence that the sorption data accurately fit the Langmuir, Freundlich, and D‐R isotherms, indicating chemisorption occurred and that E, the mean sorption energy of thorium and uranium on the different molds of unsaturated polyester–styrene, was between 8.304 and 13.92 kJ/mol, reflecting the nature of the ion exchange. The thermodynamics of sorption were considered in order to evaluate ΔH, ΔS, and ΔG. The data showed that the sorption process was spontaneous and exothermic. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4098–4106, 2006