Effect of Polymer Dissolution Temperature and Conditioning Time on the Morphological and Physicochemical Characteristics of Poly(Vinylidene Fluoride) Membranes Prepared by Non-Solvent Induced Phase Separation

This work reports on the production of poly(vinylidene fluoride) (PVDF) membranes by non-solvent induced phase separation (NIPS) using N,N-dimethylformamide (DMF) as solvent and water as non-solvent. The influence of the processing conditions in the morphology, surface characteristics, structure, thermal and mechanical properties were evaluated for polymer dissolution temperatures between 25 and 150 °C and conditioning time between 0 and 10 min. Finger-like pore morphology was obtained for all membranes and increasing the polymer dissolution temperature led to an increase in the average pore size (≈0.9 and 2.1 µm), porosity (≈50 to 90%) and water contact angle (up to 80°), in turn decreasing the β PVDF content (≈67 to 20%) with the degree of crystallinity remaining approximately constant (≈56%). The conditioning time did not significantly affect the polymer properties studied. Thus, the control of NIPS parameters proved to be suitable for tailoring PVDF membrane properties.

Extraction of Platinum From Spent Catalyst as pt/Al2O3 in aqua regia

Spent catalyst from Biji Refining contained valuable metals such as platin. This study focus on platinum extraction in aqua regia solution. Three factors effecting on the process were study including dissolution temperature, normality of aqua regia and agitation speed. The ideal conditions for process give 0.22 gm platinum extraction in dissolution temperature 80 C0, normality for aqua regia was 6 and 120 rpm mixing speed for solution

Acetylation of Nata de coco (bacterial cellulose) and membrane formation

Nata de coco (NDC), a bacterial cellulose formed by Acetobacter xylinum, was utilized to fabricate a membrane via acetylation and phase inversion methods. The NDC was activated and dissolved in N,N-Dimethylacetamide (DMAc) with lithium chloride (LiCl) at varying amounts of NDC, LiCl/DMAc ratio, activation temperature, and dissolution temperature. Acetylation was done by adding acetic anhydride (in a mass ratio of 1:12 NDC-anhydride) to NDC-DMAc/LiCl solution at a dissolution temperature of 110 °C for 3 hours. The modified-NDC was recovered via precipitation in methanol. The modified-NDC was washed with deionized water then freeze-dried. Modification was verified by determining the degree of substitution (DS) using titration and FTIR analysis. It was observed that the modification could be carried out at an NDC/DMAc (w/v) ratio of 1:75 at 120 °C for 1 hour, and addition of 8% (w/v) LiCl catalyst at 110 °C for 20 minutes. The DS of the modified-NDC was observed in the range of 2.84 – 3.69, which indicates a successful modification. This was further verified by the FTIR results. Membrane fabrication was carried out using the modified-NDC via immersion-precipitation and solvent evaporation methods. A successful membrane formation was observed using solvent evaporation.

DEVICE FOR CAUTERY OF BLEEDING USING A SALT WITH LOW CRYOHYDRATE DISSOLUTION TEMPERATURE

Objectives The aim of the study is to consider the design of a device for the cautery of bleeding by the method of local freezing of the blood flow zone performed using a salt with a low cryohydrate dissolution temperature, as well as to model heat exchange processes when using this technique.MethodA design for a device for cauterising bleeding using salts having a low dissolution temperature was developed. This ensures a high cooling intensity, shortening the time of formation of a thrombus stopping the blood flow. A model of the device was constructedaccording to the principlesgoverning the solidification of a viscous liquid and heat transfer associated with the dissolution of salts in water. The model was calculated using the finite difference method. A determination of haemostasis duration wasprovided by a numerical experiment.ResultsPlots of the temperature dependence of the salt solution in water over time are obtained, reflecting the duration of the device's output to operating mode, as well as plots of duration of a 3 mm thick formation of solid phase blood against the temperature of the solution for different values of blood flow pressure in the wound area.Conclusion On the basis of the numerical experiment, it was established that ammonium nitrate can be used as a working substance (salt) in the device. When it is dissolved in water, the minimum temperature of the solution is 256 K. The selection of the salt type and its quantity should be guided by medical norms and regulations in order to avoid the process of frostbite of the tissues adjacent to the bleeding zone. It was shown that the duration of blood solidification and the formation of a thrombus of the required thickness depend significantly on the pressure of the blood flow in the wound area, which must be taken into account when designing the device.

Extraction of Keratin from Rabbit Hair by a Deep Eutectic Solvent and Its Characterization

Keratin from a variety of sources is one of the most abundant biopolymers. In livestock and textile industries, a large amount of rabbit hair waste is produced every year, and therefore it is of great significance to extract keratin from waste rabbit hair in terms of the treatment and utilization of wastes. In this study, a novel, eco-friendly and benign choline chloride/oxalic acid deep eutectic solvent at a molar ratio of 1:2 was applied to dissolve waste rabbit hair, and after dissolution keratin was separated by dialysis, filtration, and freeze-drying. The dissolution temperature effect was discussed, and the resulting keratin powder was characterized by X-ray diffraction, scanning electron microscope, Fourier transform infrared spectroscopy, protein electrophoresis, thermogravimetry and differential scanning calorimetry, and amino acid analysis. During the dissolution process, the α-helix structure of rabbit hair was deconstructed, and the disulfide bond linkages were broken. The solubility of rabbit hair was significantly enhanced by increasing dissolution temperature, and reached 88% at 120 °C. The keratin produced by dissolving at 120 °C displayed flaky powders after freeze-drying, and had a molecular weight ranging from 3.8 to 5.8 kDa with a high proportion of serine, glutamic acid, cysteine, leucine, and arginine. Such features of molecular weight and amino acid distribution provide more choices for the diverse applications of keratin materials.