Adsorption study of a commonly used antidepressant drug, fluoxetine hydrochloride, onto a crosslinked ß-cyclodextrin-carboxymethylcellulose polymer.

A study was carried out by ultraviolet-visible (UV-vis) and Fourier transform infrared (FTIR) spectroscopies to establish the efficiency of adsorption of fluoxetine hydrochloride (FLU), onto a crosslinked ß-cyclodextrin-carboxymethylcellulose (ß-CD-CMC) polymer. The adsorption was performed in mixtures containing aqueous FLU solution at 20 mg/L and 0.01-0.30 g of the ß-CD-CMC polymer, at 25 °C, and atmospheric pressure under stirring. The results have revealed that the adsorption is a rapid process and the polymer possesses a high affinity for FLU with an adsorption capacity of 5.076 mg of FLU/g of polymer. This adsorption may involve the formation of a stable inclusion compound ß-CD-CMC/FLU through the penetration of the FLU aromatic ring (A and/or B) into the ß-CD cavity, and a physical adsorption with the polymer network. The inclusion compound can be stabilized by the formation of H-bonds between the -CF(3) group of FLU and the 6'-OH group of ß-CD, and van der Waals interactions between the FLU aromatic ring and ß-CD cavity. The data from a kinetic study have also indicated that the adsorption process was well described by the pseudo-second-order kinetic model, in which the initial adsorption rate and constant were estimated at 1.938 mg/g min and 0.075 g/mg min, respectively. Moreover, the results of adsorption equilibrium fitted the Freundlich isotherm, indicating a multilayer coverage and heterogeneous surface. Together, these results suggest that the adsorption of FLU onto the crosslinked ß-CD-CMC polymer could constitute an advantageous technology for removing this commonly used antidepressant drug from wastewater due to the high adsorption capacity of the polymer and non-toxic character of ß-CD to humans and environment.

Synthesis and structure-activity study of quaternary ammonium functionalized beta-cyclodextrin-carboxymethylcellulose polymers.

Carboxymethylcellulose (CMC) and beta-cyclodextrin (beta-CD)-based polymers functionalized with two types of quaternary ammonium compounds (QACs), the alkaquat DMB-451 (N-alkyl (50% C14, 40% C12, 10% C10) dimethylbenzylammonium chloride) (DMD-451) named polymer DMB-451, and FMB 1210-8 (a blend of 32 w% N-alkyl (50% C14, 40% C12, 10% C10) dimethylbenzylammonium chloride and 48 w% of didecyldimethylammonium chloride) named polymer FMB 1210-8, were synthethized and characterized by Fourier transform infrared spectroscopy. The antimicrobial activities of these polymers against Eschericia coli were also evaluated at 25 degrees C in wastewater. The results have indicated that the polymer FMB 1210-8 possesses a high-affinity binding with bacterial cells that induces a rapid disinfection process. Moreover, in the same experimental conditions of disinfection (mixture of 1.0 g of polymer and 100 mL of wastewater), the polymer FMB 1210-8 has a higher antimicrobial efficiency (99.90%) than polymer DMB-451 (92.8%). This phenomenon might be associated to a stronger interaction with bacterial cells due to stronger binding affinity for E. coli cells and greater killing efficiency of the C10 alkyl chains QAC of polymer FMB 1210-8 to disrupt the bacterial cell membrane as compared to N-alkyl (50% C14, 40% C12, 10% C10) dimethylbenzylammonium chloride. Together, these results suggest that the polymer FMB 1210-8 could constitute a good disinfectant against Escherichia coli, which could be advantageously used in wastewater treatments due to the low toxicity of beta-CD and CMC, and moderated toxicity of FMB 1210-8 to human and environment.

Adsorption and recovery of nonylphenol ethoxylate on a crosslinked beta-cyclodextrin-carboxymethylcellulose polymer.

A study of adsorption/recovery of nonylphenol 9 mole ethoxylate (NP9EO) on a crosslinked beta-cyclodextrin-carboxymethylcellulose (beta-CD-CMC) polymer was carried out by ultraviolet-visible (UV-vis) and Fourier transform infrared (FTIR) spectroscopies. The adsorption was performed in mixtures containing 500 mg of the beta-CD-CMC polymer and aqueous NP9EO solutions at concentrations 12-82 mg/L, whereas the recovery of NP9EO was effectuated by shaking the beta-CD-CMC polymer loaded with methanol. The assays were made at 25 degrees C and atmospheric pressure under agitation. The results have shown that the adsorption is a rapid process and the beta-CD-CMC polymer exhibits a high NP9EO adsorption capacity of 83-92 w% (1.1-6.8 mg NP9EO/g beta-CD-CMC polymer) dependent of the initial NP9EO concentration in liquid phase. This adsorption may involve the formation of an inclusion complex beta-CD-NP9EO and a physical adsorption in the polymer network. The adsorption equilibrium measurements, which were analyzed using the Langmuir isotherm, have indicated a monolayer coverage and the homogeneous distribution of active sites at the surface of the beta-CD-CMC polymer. Moreover, the negative value obtained for the free energy change (-13.2 kJ/mol) has indicated that the adsorption process is spontaneous. In parallel, the beta-CD-CMC polymer exhibited a high NP9EO recovery efficiency of 97 w% that may occur through a decrease of binding strength between beta-CD-CMC polymer and NP9EO. Together, these results suggest that the beta-CD-CMC polymer could constitute a good adsorbent for removing nonylphenol ethoxylates from wastewater due to its high adsorption capacity and non-toxic character of beta-CD and CMC to environment.

UV-VIS and FTIR spectroscopic analyses of inclusion complexes of nonylphenol and nonylphenol ethoxylate with beta-cyclodextrin.

A study of inclusion complexation of liquid non-ionic surfactants, nonylphenol (NP) and nonylphenol 9 mole ethoxylate (NP9EO), with beta-cyclodextrin (beta-CD), was carried out by mass spectrometry, surface tension, and ultraviolet-visible (UV-VIS) and Fourier transform infrared (FTIR) spectroscopies. The inclusion complexation was effectuated by heating at 80 degrees C and filtration of aqueous NP+beta-CD and NP9EO+beta-CD suspensions. The mass spectrometry and surface tension measurements revealed that NP and NP9EO form inclusion complexes with beta-CD and beta-CD possesses a higher affinity for NP. These results are supported by the data from UV-VIS spectroscopic analyses that have indicated that a three times greater amount of NP is entrapped into beta-CD than NP9EO. This phenomenon has been associated with the smaller size and a higher degree of hydrophobicity of NP that favours its entrapment into beta-CD as compared to that of NP9EO. At the structural level, the data from FTIR spectroscopic study have indicated that alkyl chains of NP and NP9EO can form van der Waals interactions with the cavity of beta-CD. Moreover, NP and NP9EO seem to cause a reorganization of the intramolecular hydrogen bonds and change of the hydration of beta-CD, but did not appear to strongly interact with C-C, C-O-C, and OH groups of beta-CD. Together these results suggest that the formation of inclusion complexes by NP and NP9EO with beta-CD molecules could constitute an effective and advantageous technique to remove liquid non-ionic surfactants from wastewater due to the non-toxic character of beta-CD to humans and the environment.

Advances in principal factors influencing carbon dioxide adsorption on zeolites.

We report the advances in the principal structural and experimental factors that might influence the carbon dioxide (CO2) adsorption on natural and synthetic zeolites. The CO2 adsorption is principally govern by the inclusion of exchangeable cations (countercations) within the cavities of zeolites, which induce basicity and an electric field, two key parameters for CO2 adsorption. More specifically, these two parameters vary with diverse factors including the nature, distribution and number of exchangeable cations. The structure of framework also determines CO2 adsorption on zeolites by influencing the basicity and electric field in their cavities. In fact, the basicity and electric field usually vary inversely with the Si/Al ratio. Furthermore, the CO2 adsorption might be limited by the size of pores within zeolites and by the carbonates formation during the CO2 chemisorption. The polarity of molecules adsorbed on zeolites represents a very important factor that influences their interaction with the electric field. The adsorbates that have the most great quadrupole moment such as the CO2, might interact strongly with the electric field of zeolites and this favors their adsorption. The pressure, temperature and presence of water seem to be the most important experimental conditions that influence the adsorption of CO2. The CO2 adsorption increases with the gas phase pressure and decreases with the rise of temperature. The presence of water significantly decreases adsorption capacity of cationic zeolites by decreasing strength and heterogeneity of the electric field and by favoring the formation of bicarbonates. The optimization of the zeolites structural characteristics and the experimental conditions might enhance substantially their CO2 adsorption capacity and thereby might give rise to the excellent adsorbents that may be used to capturing the industrial emissions of CO2.

FTIR spectroscopic analyses of the temperature and pH influences on stratum corneum lipid phase behaviors and interactions.

A thermotropic investigation of different lipid dispersions containing ceramide 3 (CER3) or sphingomyelin (SPM), perdeuterated palmitic acid (PA-d(31)) and cholesterol (CH) or cholesterol sulfate (CS) at pH 5.2 and 7.4 used as model membranes, has been carried out by Fourier transform infrared (FTIR) spectroscopy in order to estimate the importance of these lipids and of the temperature and pH for the maintenance of the structural organization of the stratum corneum (SC) lipid lamellae. The results obtained for the CER3 and SPM mixtures at pH 5.2 and 7.4 indicated that the little size of the polar headgroup of CER3 compared with that of SPM could permit a more closely packing in the CER3 acyl chains. Moreover, the CH and CS induced an increase of the order in the CER3 acyl chains over the physiological temperatures while a disordering was seen above 60 degrees C. In addition, the thermal phase behaviors observed for the CER3/PA-d(31) dispersion at pH 5.2 and 7.4, suggested a phase separation between the CER3 and PA-d(31) molecules in this mixture. Nevertheless, the miscibility between the CER3 and PA-d(31) was raised in the presence of CH or CS at pH 5.2. In particular, the incorporation of these sterols into the CER3/PA-d(31) dispersion at pH 5.2 appeared to result in an increase of the order in the acyl chains of CER3 and PA-d(31) at about 37 degrees C. In contrast, a phase separation was observed between the CER3 and PA-d(31) in the CER3/PAd(31)/CH and CER3/PA-d(31)/CS dispersions at pH 7.4. Interestingly, the pH change from 5.2 to 7.4 in these tertiary dispersions was also accompanied by a substantial deprotonation of the PA-d(31) molecules which seemed more pronounced in the presence of CH as compared with CS. Altogether, the results suggested that the ceramides, fatty acids and sterols could play an important structural role in the SC cohesion.