Band 18, Heft 4

The role of polypyrrole-cellulose (PPy-Ce) nanocomposite for the removal of Ni(II) from aqueous solution was investigated by batch experiments. The PPy-Ce nanocomposite was prepared by chemical oxidate polymerization of pyrrole monomer with cellulose. Transmission electron micrography (TEM) showed the size of the particles varied from 80 to 95 nm. The characteristic C-O, O-H, C-N and C-C vibrations in the Fourier transform infrared (FTIR) spectra indicate that the cellulose successfully integrated with the pyrrole. Influence of experimental variables such as pH, contact time, adsorbent dose and initial Ni(II) concentration were optimized using the response surface methodology (RSM) based Box-Behnken design (BBD). The optimal conditions for maximum removal of Ni(II) were pH 8, time 65 min, adsorbent dose 0.3 mg/l and Ni(II) concentration 50 mg/l. The maximum removal efficiency under optimized conditions was >94%. The results indicate that BBD could be used to optimize experimental conditions for metal removal from aqueous solution.

In this work, the structural characterization and adsorption behavior of glucose and glucosamine grafted polyacrylamide/graphite composites (denoted as Gu-g-PAM/graphite and GA-g-PAM/graphite) were investigated. The grafted polymers were characterized by using Fourier transform infrared (FT-IR) spectroscopy, 1 H nuclear magnetic resonance (NMR), 13 C NMR and N 2 sorption studies. The adsorption behavior of grafted polymers was compared by varying parameters such as pH, initial dye concentration, agitation time, adsorbent dose and temperature. The results showed that GA-g-PAM/graphite composite was an effective adsorbent for the uptake of acid violet 17 (Av-17) from an aqueous solution. The superior adsorption behavior was attributed to the presence of -NH 2 and -OH groups in GA-g-PAM/graphite. Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherms were used to describe the adsorption isotherm. The adsorption isotherm of the adsorbents fitted well with the Langmuir model with the maximum adsorption capacity (q o ) of 78.13 mg/g for GA-g-PAM/graphite. The efficiency of adsorption with time was described using pseudo first-order, pseudo second-order and intra particle diffusion kinetic models. The kinetic study revealed that the adsorption equilibrium was attained within 50 min. The thermodynamic analysis stated that the adsorption of dye is spontaneous, physical and endothermic in nature. Desorption results revealed that all the adsorbents exhibit excellent stability and remarkable regeneration ability.

In this work the results on the first use of an activated composite membrane (ACM) containing Cyanex 923 for the extraction and transport of phenol are presented. A new dense layer-ACM configuration constituted by piperazine showed better stability than that prepared with 1,3-phenylenediamine. The effects of several parameters on the transport of phenol such as feed phase pH, carrier concentration and stripping phase composition were evaluated. The performance of the membrane was also evaluated during continuous additions of phenol and for a long period of time, observing the same rate of extraction and reextraction. Moreover, phenol transport was evaluated starting from synthetic wastewater of resin production plants type. The results exhibit the potential use of ACMs in the elimination and transport of organic species, even when analyte is initially found in complex solutions.

Erythritol (E)/polyvinyl alcohol (PVA) phase change composite fibers in which PVA acts as supporting material and different contents of erythritol act as phase change materials (PCMs) were prepared by electrospinning. The effects of different nanoparticles on fiber morphology and thermal properties of composites were also studied. The morphology and thermal properties were characterized by using scanning electron microscopy (SEM), differential scanning calorimetery (DSC) and a thermal conductivity test, respectively. The results showed E/PVA composite fibers were cylindrical with a smooth surface. The content of erythritol in composites could reach a high of 80 wt% with good shape stability, and a high enthalpy value of 258.9 J/g after 100 thermal cycles. The effects of nanoparticles on composites were mainly embodied in decreasing average fiber diameters (AFDs), phase change temperatures and enthalpies with the increase of particle concentrations, and improving fiber stability and thermal conductivity. Among them, the smallest AFDs (0.56 μm) and the lowest heat loss rate (1.0%) were obtained from composites with 4% nano C and 4% nano Al 2 O 3 , respectively. The 4% nano SiO 2 composites possessed the best shape stability. In addition, the composites that contains 4% nano carbon could decrease the erythritol’s supercooling of 7.55°C, and showed the highest thermal conductivity of 1.55 W/m·K, which was 167% of E/PVA composites. These results demonstrate that E/PVA composites possess high enthalpy values while they improve shape stability and thermal conductivity.

Very rapid crystallization behaviors of poly(L-lactic acid) (PLLA) are observed at room temperature when it is precipitated from a chloroform solution into a large amount of alcohols (non-solvents). The resulting crystalline phase contains both a highly ordered (α) and less ordered (α′) modifications, and the fraction of these phases depends on the alcohols used as the non-solvents: methanol tends to produce the highly ordered phase. The degree of crystallinity tends to be high for lower alcohols. When the precipitation occurs in n -hexane, almost no crystalline phase is formed, but a mesomorphic phase is formed as a precursor to the crystalline phase. The results suggest that the hydroxyl group of alcohols tends to promote the crystallization of PLLA. However, it is found that the precipitation in methanol at lower temperatures, such as 0°C, does not yield any crystalline phase. It is suggested that the present rapid crystallization during precipitation originates from the enhanced mobility of PLLA molecules in a metastable (non-equilibrium) liquid state.

In this study, we investigated the effects of solution characteristics on electrospinning behavior and nanoweb structure. We prepared a polyvinylidene fluoride (PVDF) solution by varying the ratios of N,N -dimethylformamide (DMF) and acetone in the solvent and fabricated nanowebs by electrospinning. We determined the solution characteristics of the PVDF solution with respect to the acetone ratio in the solvent. The effects of the solution characteristics on the electrospinning behavior were confirmed using a high-speed camera. We found significant differences in the electrospinning behavior. Thus, we investigated the effect of this difference on the morphology and structural properties of the fabricated nanoweb.

Poly(vinyl amine) was utilized as a matrix for the synthesis of polymers bearing short polyamine chains (1–3 amine groups) grafted to the main macromolecular chain with long (eight atoms) spacers. The new polymers were characterized with nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) spectra, size exclusion chromatography and potentiometry. Poly(vinyl amine) was applied in the form of narrow molecular mass fractions and the modification proceeded without destruction of the main chain. Condensation of silicic acid in the presence of the polymeric amines gives rise to composite nanoparticles which are stable in aqueous medium. New polymers and composite nanoparticles effectively complex with DNA and RNA oligonucleotides and were found to display good internalization in cancer cells which indicates their promise towards gene delivery applications.

Conventional pharmaceuticals generally display the inability to transport active ingredients directly to specific regions of the body, amongst some of their main limitations. The distribution of the drugs in the circulatory system may lead to undesired toxicity, and therefore, adverse reactions. To address this situation, a selective transport of drugs is required, that is, releasing drugs specifically to the site of action in appropriate concentrations and in the right time. To achieve this goal, it is necessary to develop delivery systems that respond to several features, such as low toxicity, optimum properties for the transport and release of the drug, as well as a long half-life in the body. This feature paper critically provides an overview of different strategies of controlled drug release for two model antineoplasic drugs, i.e. doxorubicin (DOX) and 5-fluorouracil (5-FU). Any of the presented strategies for drug release possess advantages and disadvantages, and the selection of the strategy used will depend on the targeted tissue and nature of the drug.