C. Uliana

The Performance of a Rotating Module in Oily Emulsions Ultrafiltration

Abstract The rotating ultrafiltration module has been applied to concentrated oily emulsions with the aim of checking its practical features. The ultrafiltration yield has been measured as a function of pressure, tangential speed, temperature, oil concentration, and hydrodynamic conditions. An energy consumption evaluation has been performed and a comparison with tubular modules tried. The importance of turbulence promoters and the influence of the radial geometry of the module has been outlined by means of simulation tests with a transparent model system.

Asymmetric polivinylidenfluoride (pvdf) radiation grafted membranes: preparation and performance in reverse osmosis application

Abstract A new type of reverse osmosis membrane has been synthesized. Membranes were prepared starting from asymmetric PVDF films, obtained by the casting and gelation technique and modified by radiochemical grafting and sulphonation. These membranes were tested in an RO laboratory plant and their performances were determined as a function of preparative parameters. The influences of evaporation time and temperature grafting and solvents were investigated. These membranes exhibit permeabilities as high as 2000 l/m2d and sodium chloride rejections up to 70%.

Influence of the Vorticity at the Membrane Surface on the Performances of the Ultrafiltration Rotating Module

Abstract The performances of a rotating module during the ultrafiltration of oily emulsions have been studied and correlated with the vorticity at the membrane surface. Thus, a fully transparent module has been assembled and the size and shape of the vortices observed as functions of the rotational speed and the clearance of the annular gap around the membrane. The influence of the roughness and profile of the inner wall of the module has also been investigated. Photographs of the vortices have been correlated to the actual performances of a steel module. Evidence has been found relating the permeate flux and the size of the vortices.

The Vibrating Ultrafiltration Module. Performance in the 50–1000 Hz Frequency Range

Abstract The effect of mechanical vibrations on the ultrafiltration of oily emulsions was studied in the 50–1000 Hz range. A cylindrical vibrating module was assembled and coupled with an electrodynamic exciter, controlled by a computerized system. The ultrafiltration experiments were run with a 20% cutting oil/water emulsion at different working conditions. The experimental data demonstrated that both vibration amplitude and frequency are effective in enhancing membrane performance. The influence of the frequency is more marked. Energy consumption was evaluated, and simple equations were proposed in order to predict both performances and energy requirements.

Ultrafiltration membranes obtained by poly(acrylonitrile) grafted onto poly(vinylchloride)

Abstract Acrylonitrile (AN) has been grafted onto Polyvinylchloride (PVC) dissolved in Dimethylformamide (DMF) by means of gamma rays from a Co60 source. The grafting yield has been studied as a function of irradiation dose and initial AN/PVC ratio in the solution. The ratio PAN/PVC has been evaluated both in the grafted copolymer and its fractions by infrared spectroscopy. Ultrafiltration membranes have been prepared from the grafted PVC and its fractions, using the phase inversion technique. The UF performances have been studied as a function of PAN grafted %. The results show that both water flux and rejection increase with the grafting. Electron microscopy has also been employed to investigate the membrane structure.

Poly(vinyl chloride) ultrafiltration membranes modified by glow discharge grafting of poly(acrylic acid)

Abstract The radicals and the “soft” radiations produced by low pressure electrical discharges have been widely applied for modifying the surface properties of many polymers. In this study, we tried to change the transport properties of ultrafiltration membranes. Asymmetric membranes made of poly(vinyl chloride) were submitted to glow discharge in the presence of Ar, then reacted with acrylic acid vapours in order to achieve grafting on the surface. This two-step method allowed us to gain better control of the process and to obtain membranes with enhanced performance. The structure of the membranes so obtained was studied by SEM.

The Vibrating Ultrafiltration Module. Performance in the Low Frequency Region

Abstract The effect of vibrations on oil emulsion ultrafiltration was studied as a function of frequency (in the 0–50 Hz range) and of amplitude (0.0016–0.045 m). The experimental date obtained show that a minimal (“critical”) frequency must be reached in order to achieve effective ultrafiltration of oil from water. This “critical” frequency depends only on vibration amplitude. It was also found that the permeate fiux increases with frequency and reaches a plateau value which depends only on the applied pressure. A mathematical relation is proposed in order to relate these parameters and to predict the behavior of the vibrating module in conditions different from the experimental ones. The energy consumption of such a module was evaluated as a function of the operative variables in order to determine the optimal working conditions.

Suitability of reverse osmosis membranes for energy recovery by submarine osmotic power plants

Abstract A mathematical model has been developed to predict behaviour and preformance of some energy recovery by means of osmotic dilution. Experimental tests have been carried out in order to check the feasibility of the mathematical relations. Commercial of laboratory-made cellulose acetate membranes have been used; salt permeability and osmotic flow have been monitored as functions of time under both osmotic and pressure-retarded osmosis conditions. Some other parameters which are relevant to the practical applications of the above mentioned process have also been measured, in order to draw conclusive evaluations on the suitability of the method.

Polytrimethylsylylpropyne gas separation membranes modified by radiochemical grafting of divinylbenzene

A radiochemical method was employed to obtain poly(1-trimethylsilyl-1-propyne)(PTMSP)-divinylbenzene (DVB) grafted films. DVB monomer vapors were absorbed by the PTMSP, and the grafting reaction was thereafter accomplished by {sup 60}Co {gamma}-irradiation in a nitrogen atmosphere. The films so obtained were tested for nitrogen-oxygen separation. The performances of the membranes were studied as functions of time and percent of grafting. The DVB-grafted membranes show an increased selectivity factor and stability with time. The experimental data and some SEM observations confirm the presence of large voids in the PTMSP matrix. These voids are responsible for permeability changes during operation and disappear after the grafting procedure. 8 refs., 5 figs.

Ultrafiltration Membranes Prepared by Styrene-Grafted Polyvinylpyrrolidone

Abstract The suitability of a new grafted copolymer for preparing ultrafiltration membranes was studied. The copolymer was obtained by radiochemical grafting of styrene onto polyvinylpyrrolidone. The membranes were prepared by the phase-inversion technique from N-methyl-2-pyrrolidone solutions. Influence of grafting degree and solutions concentration on the ultrafiltration performances were studied. It was demonstrated that for polystyrene grafting values close to 85% w/w and a copolymer solution concentration of 15% w/v, the membranes have a high permeate flux (more than 100 L·m−2·h−1) and a good separation factor (more than 95%) for aqueous dextran solutions. The mechanical resistance of the membranes was evaluated and their microscopic structure was examined by SEM.