Cellulose Triacetate Matrix Research Articles

Polymer inclusion membranes: The concept of fixed sites membrane revised

The mechanism of facilitated transport of metal ions across polymer inclusion membranes (PIMs) is revised on the basis of transport flux measurements and of new data brought by techniques sensitive to local inter-molecular interactions and molecular diffusion. Cellulose triacetate (CTA) membranes built with two types of inclusion carriers: a liquid one Aliquat 336 and a crystalline one Lasalocid A, both able to carry metal ions across PIMs and supported liquid membranes (SLMs) made of the same components, have been compared. Both PIM systems show similar effects for what concern the need of a carrier threshold concentration for the occurrence of a transport flux across PIM as revealed by flux and fluorescence correlation spectroscopy (FCS) measurements, and the dependence of the chemical nature of plasticizers on the metal ion flux. These systems also present similar Raman and far IR signatures of structural evolution of PIMs with the increase of the carrier concentration within the CTA matrix. All the presented data are interpreted as concern PIMs, according to an evolution of chemical interactions between components of the polymeric membrane able to lead to a phase transition. This phase transition type of the carrier-plasticized polymer system is induced by the increase of carrier concentration in the polymer chains. The PIM progressively organizes itself like a liquid SLM because of the enhancement of preferential solvent interactions between the carrier and the plasticizer. The main conclusion of this study is that the classically adopted “hopping” transport mechanism between fixed carrier sites in a PIM does not apply to such carrier chemically unbound to polymer membrane systems.

Scintillating polymer inclusion membrane for preconcentration and determination of $alpha;-emitting actinides

The scintillating polymer inclusion membrane (S-PIM) was developed for preconcentration and determination of α-emitting actinides from aqueous solution. The preparation of S-PIM involved physical immobilization of an extractant bis(2-ethylhexyl)phosphoric acid, primary scintillator 2,5-diphenyloxazole, and secondary scintillator 1,4-bis(2-methylstyryl)benzene in the plasticized cellulose triacetate matrix. The S-PIM was found to be effective for the quantitative sorption (94–98%) of trivalent lanthanides/actinides ( 147 Pm , 154 Eu and 241 Am ), tetravalent actinides (Pu(IV)) and hexavalent actinides (U(VI)) from the aqueous solutions whose acidity had been adjusted to pH 2.5, 1.0 and 0.25 mol/L, respectively with dilute HNO 3 . The interference of β-emitting lanthanides, in preconcentration and determination of α-emitting actinides using S-PIM, were also studied. The α-scintillation counting efficiency in the S-PIM was found to be 92–95% after discriminating the background noise. However, β-scintillation counting efficiency was found to be in the range of 12–25% depending upon the energy of β-particles. It was observed that β-scintillation pulses from 147 Pm and 154 Eu could be discriminated based on pulse height analysis. Thus, α-activities of the actinides sorbed in the sample of S-PIM could be directly measured in the presence of β-emitters by scintillation counting. However, the α-scintillation counting efficiency was reduced to 38% after discriminating β-scintillation pulses in the S-PIM. The preconcentration ability of S-PIM was examined in tap water and seawater spiked with 241 Am . The total α-activity of 46 Bq (present in 100 mL) could be preconcentrated and measured from tap water using S-PIM.

Chemically selective membrane optode for Cr(VI) determination in aqueous samples

A methodology for simultaneous preconcentration and determination of Cr(VI) from aqueous samples was developed using a membrane optode formed by physical inclusion of a Cr(VI) selective chromophore 1,5-diphenylcarbazide (DPC) into a plasticized cellulose triacetate matrix. The inclusion of an anion exchanger (Aliquat-336) was found to be effective for immobilization of both DPC and Cr(VI)–DPC complex in the optode matrix itself. The proportionality in intensity of the magenta color on the optodes loaded with varying amounts of Cr(VI) suggests its potential applications for screening of Cr(VI) in aqueous samples by visual colorimetry. On loading high amounts of Cr(VI) in the membrane optode, its color changes from magenta to yellow, which indicates the possibility of using it as a threshold detector for Cr(VI). The membrane optode was optimized in terms of obtaining maximum preconcentration efficiency for Cr(VI) and subsequent stable optical response proportional to the amount of Cr(VI) in the membrane optode sample. The membrane optodes were tested for Cr(VI) determination in tap water and seawater samples. Using this optode, Cr(VI) even at levels of 13.6 ppb could be quantitatively detected. The optodes developed in the present work were found to be stable, cost effective, easy to prepare and efficient for direct preconcentration and determination of Cr(VI) in a variety of aqueous samples using spectrophotometry. However, this membrane optode is for one time use only as the reaction of Cr(VI) with DPC is irreversible.

Scintillating polymer inclusion membrane for preconcentration and determination of α-emitting actinides

The scintillating polymer inclusion membrane (S-PIM) was developed for preconcentration and determination of α-emitting actinides from aqueous solution. The preparation of S-PIM involved physical immobilization of an extractant bis(2-ethylhexyl)phosphoric acid, primary scintillator 2,5-diphenyloxazole, and secondary scintillator 1,4-bis(2-methylstyryl)benzene in the plasticized cellulose triacetate matrix. The S-PIM was found to be effective for the quantitative sorption (94–98%) of trivalent lanthanides/actinides ( 147 Pm , 154 Eu and 241 Am ), tetravalent actinides (Pu(IV)) and hexavalent actinides (U(VI)) from the aqueous solutions whose acidity had been adjusted to pH 2.5, 1.0 and 0.25 mol/L, respectively with dilute HNO 3. The interference of β-emitting lanthanides, in preconcentration and determination of α-emitting actinides using S-PIM, were also studied. The α-scintillation counting efficiency in the S-PIM was found to be 92–95% after discriminating the background noise. However, β-scintillation counting efficiency was found to be in the range of 12–25% depending upon the energy of β-particles. It was observed that β-scintillation pulses from 147 Pm and 154 Eu could be discriminated based on pulse height analysis. Thus, α-activities of the actinides sorbed in the sample of S-PIM could be directly measured in the presence of β-emitters by scintillation counting. However, the α-scintillation counting efficiency was reduced to 38% after discriminating β-scintillation pulses in the S-PIM. The preconcentration ability of S-PIM was examined in tap water and seawater spiked with 241 Am . The total α-activity of 46 Bq (present in 100 mL) could be preconcentrated and measured from tap water using S-PIM.

Chemically selective membrane optode for Cr(VI) determination in aqueous samples

A methodology for simultaneous preconcentration and determination of Cr(VI) from aqueous samples was developed using a membrane optode formed by physical inclusion of a Cr(VI) selective chromophore 1,5-diphenylcarbazide (DPC) into a plasticized cellulose triacetate matrix. The inclusion of an anion exchanger (Aliquat-336) was found to be effective for immobilization of both DPC and Cr(VI)–DPC complex in the optode matrix itself. The proportionality in intensity of the magenta color on the optodes loaded with varying amounts of Cr(VI) suggests its potential applications for screening of Cr(VI) in aqueous samples by visual colorimetry. On loading high amounts of Cr(VI) in the membrane optode, its color changes from magenta to yellow, which indicates the possibility of using it as a threshold detector for Cr(VI). The membrane optode was optimized in terms of obtaining maximum preconcentration efficiency for Cr(VI) and subsequent stable optical response proportional to the amount of Cr(VI) in the membrane optode sample. The membrane optodes were tested for Cr(VI) determination in tap water and seawater samples. Using this optode, Cr(VI) even at levels of 13.6 ppb could be quantitatively detected. The optodes developed in the present work were found to be stable, cost effective, easy to prepare and efficient for direct preconcentration and determination of Cr(VI) in a variety of aqueous samples using spectrophotometry. However, this membrane optode is for one time use only as the reaction of Cr(VI) with DPC is irreversible.

Structure and Physical Properties of Poly(butylene succinate). Cellulose Acetate Blends containing Tetraisopropyl Titanate.

The blend films of poly(butylene succinate) (PBS) and cellulose triacetate (CTA) were prepared by using the solvent-cast technique. Chloroform was used as a co-solvent and tetraisopropyl titanate (TP) was used as a compatibilizer. Homogeneous blend films were obtained over a wide range of composition. The effects of the addition of TP on the structure and properties of the blend films have been investigated with FT-IR, DSC, TGA, DMA and so on. As results, we have the following conclusions: (i) the addition of TP inhibits the crystallization of PBS molecules in the CTA matrix, (ii) the addition of TP decreases the thermal decomposition temperatures of blend films, (iii) the addition of TP does not influence the mechanical properties of the blend films, and (iv) the addition of TP accelerates the hydrolysis of blend films.

Structure and physical properties of poly(butylene succinate)/cellulose acetate blends

Polybutylene succinate (Bionolle) and cellulose triacetate (CTA) were solvent-cast blended with chloroform. Homogeneous blend films were obtained over a wide range of composition. The structure and properties of the blend films were investigated using various apparatuses. From Fourier transform infrared spectroscopy, wide-angle X-ray, and thermal measurements, it was found that the miscibility of Bionolle (BN) with CTA is excellent. In other words, in CTA-rich samples, it was found that BN molecules in the CTA matrix do not form a crystalline state, but forms an amorphous state. Therefore, the mechanical properties of the CTA-rich samples do not indicate the singularity before and after the melting point of pure BN. When CTA-rich samples were heated above the glass transition temperature of CTA, the BN molecules were eluted from the CTA matrix.