Oya Şanlı

Characteristics of Permeation and Separation for Acetic Acid–Water Mixtures Through Poly(Vinyl Alcohol) Membranes Modified with Poly(Acrylic Acid)

The pervaporation separation of acetic acid–water mixtures was carried out over the full range of compositions at temperatures varying from 30° to 55°C using poly(vinyl alcohol) (PVA) membranes modified with poly(acrylic acid) (PAA). The best condition for the preparation of the membranes was found as PVA/PAA ratio as 75/25 (v/v). Effects of membrane thickness, operation temperature, feed composition on the permeation flux, and separation factor were investigated. PVA/PAA membranes gave separation factors of 34 to 3548 permeation rates of 0.03 to 0.60 kg/m2 h, depending on the operation temperature and feed mixture composition. The temperature dependence of permeation rate for binary mixtures was expressed by the Arrhenius type relation and activation energy of 17.62 kcal/mol was calculated for the permeation.

Separation Characteristics of Dimethylformamide/Water Mixtures through Alginate Membranes by Pervaporation, Vapor Permeation and Vapor Permeation with Temperature Difference Methods

Abstract In this study permeation and separation characteristics of dimethylformamide (DMF)/water mixtures were investigated by pervaporation (PV), vapor permeation (VP), and vapor permeation with temperature difference (TDVP) methods using alginate membranes crosslinked with calcium chloride. The effects of membrane thickness (30–90 µm), feed composition (0–100 wt%), operating temperature (30–50°C) on the permeation rates and separation factors were investigated. The permeation rate was found to be inversely proportional to the membrane thickness whereas separation factor increased as the membrane thickness was increased. It was observed that the permeation rates in VP and TDVP were lower than in PV however the highest separation factors were obtained with TDVP method. Alginate membranes gave permeation rates of 0.97–1.2 kg/m2 h and separation factors of 17–63 depending on the operation conditions and the method. In addition, sorption‐diffusion properties of the alginate membranes were investigated at the operating temperature and the feed composition. It was found that the sorption selectivity was dominant factor for the separating of DMF/water mixtures.

Synthesis of poly(dihalophenylene oxide)s by solid state thermal decomposition of bis(4-chloro-2,6-dibromo phenoxo) ethylenediamine copper (II) complex

Abstract In this study the synthesis of poly(dihalophenylene oxides) by the solid state thermal decomposition of a bis (4-chloro-2,6-dibromo phenoxo) ethylenediamine copper (II) complex was achieved. Yields, structures and intrinsic viscosities of the polymers were compared with those of electroinitiated and solution decomposition methods. The characterization of the polymers was carried out using FTIR and 1H-NMR spectroscopies, differential scanning calorimetry and viscosity measurements. Optimum yield was obtained at 140 °C for a decomposition time of 24 hr. Polymerization proceeded through 1,2 and 1,4 additions taking place at the same time leading to a branched structure.

Homogeneous hydrolysis of polyacrylonitrile by potassium hydroxide

Abstract Homogeneous hydrolysis of polyacrylonitrile in the presence of potassium hydroxide was studied. The gradual change in the chemical structure of the polymeric substrate during the process was followed by i.r. spectroscopy. The extent of hydrolysis was found to depend on the time of treatment, the concentration of potassium hydroxide in solution and the temperature. The presence of a second component in the structure of the polymer, the nature of the reaction medium, and the molecular weight of the polymer also affected the rate of hydrolysis.

Graft copolymerization of n-vinyl-2-pyrrolidone on dimethyl sulfoxide pretreated poly(ethylene terephthalate) films using azobisisobutyronitrile initiator

Poly(ethylene terephthalate) (PET) films were grafted with n-vinyl-2-pyrrolidone (n-VP) using an azobisisobutyronitrile (AIBN) initiator. Films were pre-treated in dimethyl sulfoxide (DMSO) for 1 h at 140°C before the polymerization reaction was carried out. Variations of graft yield with time, temperature, initiator, and monomer concentrations were investigated. The optimum temperature and polymerization time was found to be 70°C and 4 h, respectively. Increasing monomer concentration from 0.28 to 1.22M and initiator concentration from 1.77 × 10−3 to 4.20 × 10−3M enhanced the percent grafting. The effects of monomer and initiator diffusion on PET films were also studied. The overall activation energy for grafting was calculated as 11.5 kcal/mol. Further changes in properties of PET films such as water-absorption capacity and intrinsic viscosity were determined. The grafted films were characterized with FTIR and scanning electron microscopy (SEM).

Separation of Acetic Acid‐Water Mixtures through Poly(Vinyl Alcohol)/Poly(Acrylic Acid) Alloy Membranes by Using Evapomeation and Temperature Difference Evapomeation Methods

Abstract Separation of acetic acid‐water mixtures by using evapomeation (EV) method were carried out over the full range of compositions at temperatures varying from 30 to 55°C using poly(vinyl alcohol)/poly(acrylic acid) (PVA/PAA) (75/25) (v/v) alloy membranes. PVA/PAA membranes gave separation factors of 110–5711 and permeation rates of 2.3×10−4–1.53×10−1 kg/m2h, depending on the operation temperature and feed mixture composition. The temperature dependence of the permeation in EV was expressed by the Arrhenius type expression and the activation energy was calculated as 9.15 kcal/mol. More efficient EV technique, which is called temperature difference evapomeation method (TDEV) was also applied to PVA/PAA membranes to separate acetic acid‐water mixtures; high permeation rates (1.7×10−3–3.0×10−1 kg/m2h) and separation factors (1335–8924) were obtained for each of the studied feed compositions. Azeotropic mixture of acetic acid and water was also separated by TDEV method with a separation factor of 297 and permeation rate of 1.50×10−1 kg/m2h.

Use of Sodium Alginate-Poly(vinyl pyrrolidone) Membranes for Pervaporation Separation of Acetone/Water Mixtures

Pervaporative separation of acetone from water at a concentration range of 0–100 wt% were studied using sodium alginate (NaAlg)/Poly vinyl pyrrolidone (PVP) membranes. Membranes were prepared in different ratios (w/w) (100/0, 95/5, 90/10, 85/15, 80/20, 75/25) of NaAlg/PVP by crosslinking with CaCl2. Experimental studies were carried out to investigate the effects of the operating temperature, feed composition, and membrane thickness on the pervaporation performance. The optimum operating temperature, membrane thickness, NaAlg/PVP ratio, and feed composition were determined as 40°C, 70 µm, 75/25 (w/w), and 20 wt% acetone, respectively. The effect of PVP content in the membranes was investigated on pervaporation performance. The permeation rate was increased with increasing the PVP content; however, there was no appreciable change about the separation factor. The permeation rate and separation factor values were found to be in the range of 0.304–1.023 kg/m2 h and 16–57, respectively. In addition, the sorption-diffusion properties of the alginate membranes were investigated at the operating temperature and the feed composition. It was found that the sorption selectivity was the dominant factor for the separation of acetone/water mixtures.

Permeation and Separation Characteristics of Acetic Acid‐Water Mixtures by Pervaporation through Acrylonitrile and Hydroxy Ethyl Methacrylate Grafted Poly(vinyl alcohol) Membrane

Abstract In this study, acrylonitrile (AN) and hydroxyl ethyl methacrylate (HEMA) were grafted onto poly(vinyl alcohol) (PVA) using cerium (IV) ammonium nitrate as initiator at 30°C. The graft copolymer was characterized using the Fourier transform infrared spectroscopy (FTIR) and elemental analysis. The grafted PVA membranes (PVA‐g‐AN/HEMA) were prepared by a casting method, and used in the separation of acetic acid‐water mixtures by pervaporation. The effects of the membrane thickness, operating temperature, and feed composition on the permeation rate and separation factor for acetic acid‐water mixtures were studied. Depending on the membrane thickness, the temperature and feed composition PVA‐g‐AN/HEMA membranes gave separation factors 2.26–14.60 and permeation rates of 0.18–2.07 kg/m2h. It was also determined that grafted membranes gave lower permeation rates and greater separation factors than PVA membranes. Diffusion coefficients of acetic acid‐water mixtures were calculated from permeation rate values. The Arrhenius activation parameters were calculated for the 20 wt.% acetic acid content in the feed using the permeation rate and the diffusion data obtained at between 25–50°C.

Permeation and Separation Characteristics of Acetic Acid‐Water Mixtures Through Poly(Vinyl Alcohol)/Malic Acid Membranes by Evapomeation and Temperature Difference Controlled Evapomeation

Abstract The characteristics of permeation and separation of acetic acid‐water mixtures through 85/15 (v/v) poly(vinyl alcohol)/malic acid (PVA/MA) membranes were investigated by evapomeation (EV) and temperature difference controlled evapomeation (TDEV) methods. The effects of permeation temperature, membrane surrounding temperature, and feed composition on the permeation rate and the separation factor were studied. The permeation rates increased but separation factors decreased with an increase in permeation temperature in EV method. Permeation activation energy of acetic acid and water in the evapomeation were calculated as 107.4 kJ/mol and 36.5 kJ/mol, respectively, using an Arrhenius type relationship. When the temperature of feed solution was kept constant and the temperature in the membrane surrounding was dropped, it was observed that the permeation rate and separation factor were significantly influenced by the temperature of membrane surroundings. The increase in the acetic acid concentration in the feed vapor mixture decreased the permeation rate and increased the separation factor except 40 wt.% acetic acid content. The best separation factor was found at a composition of 90 wt.% acetic acid as 800 in the EV and 860 in the TDEV. Separation index in both methods were also calculated, the separation index of TDEV method was found to be higher than that of EV method for azeotropic composition of acetic acid‐water. TDEV method for separation of acetic acid‐water mixtures through the PVA/MA membranes was found to be more effective than evapomeation method. The authors are grateful for the financial support from Gazi University Research Fund for the support of this study.

Swelling-assisted graft copolymerization of 4-vinyl pyridine on poly(ethylene terephthalate) films using a benzoyl peroxide initiator

Graft copolymerization of 4-vinyl pyridine (4-VP) on poly(ethylene terephthalate) (PET) films using a benzoyl peroxide (Bz2O2) initiator was investigated under different conditions including polymerization time, temperature, monomer concentration, and initiator concentration. Dimethyl sulfoxide (DMSO) was used as swelling agent to promote the incorporation and the subsequent polymerization of 4-VP to PET films. Maximum percent grafting was obtained when the polymerization was carried for a period of two hours at 65°C. Increasing the monomer concentration from 0.2M to 0.8M and Bz2O2 concentration from 1.0×10−3M to 2.5×10−3M was accompanied by a significant enhancement in percent grafting. Monomer diffusion on PET films and its effect on the grafting yield were studied and intrinsic viscosities of grafted films were also measured.