Casting parameters

Polysulfone membranes were prepared from 12.5, 13.75, and 15% (wt. %) polysulfone solution in dimethylformamide and formed on the surface of porous, sintered polymethyl methacrylate bars. An effective surface of each membrane was 49.2 cm. The effect of some casting parameters (composition and the temperature of the casting solution, time of solvent evaporation) and the pressure applied on the transport and separation properties of the membranes were analyzed. The experiments were carried out in a 1.2 dm pressure apparatus with continuous circulation of the permeate between feeding tank and the apparatus. It was found that membranes cast from 12.5% polysulfone solution of a temperature of 298 K with no solvent evaporation displayed the best properties. After 160 hours of operation at 0.18 MPa, the membranes in question showed an ability of a 97 to 99% rejection of 781.2 molecular-weight dye. The volume flux of the dye solution varied from 0.6 to 0.8m /m per day. 

In this procedure, five sequences of membranes were prepared. Each of them consisted of two or three membrane series differing in casting parameters (Table 1). 

EFFECT OF CASTING PARAMETERS ON THE TRANSPORT PROPERTIES OF THE MEMBRANES... 

The relationship between dye elimination coefficient and casting parameters is plotted in Figures 3 to 7. The curves given there show that, when the time of solvent evaporation (Fig. 5) and PS concentration in the casting solution (Fig. 7) increase, the separation factor also increases. On the other hand, increasing the temperature of the casting solution accounts for transitory deterioration of the separation properties of the membranes (Fig. 6). 

The relationship between separation properties and casting parameters depends on the membrane structure. According to the Bokhorst - Altena — Smolders theory of phase separation [ 8 ], when PS concentration in the casting solution is increased and the time of solvent evaporation is extended, pore diameter decreases, thus improving the selectivity of the membranes. However, the increase of temperature to a critical value accounts for the increase of pore diameter, which brings about a decrease of the separation factor value. Further increase in temperature brings about a rapid evaporation of the solvent to yield small pore diameter membranes characterized by better separation properties. 

As illustrated in Fig. 6.38, the key component of the tape casting equipment is the doctor blade assembly. It consists of an adjustable doctor blade mounted in a frame with a reservoir to hold the slurry (or slip) before it is metered out under the blade to form the thin layer of slurry on the carrier surface. The flow behavior of the slurry during the casting of the tape has been analyzed theoretically to estimate the influence of the casting parameters on the thickness of the tape (47). 

No. Cast parameters Refinement parameters Macrostructure of ingot... 

Optimization of alloy composition, casting parameters, and subsequent treatment provides the required characteristics. 

The first reported porous NF membrane is made from hydrolysed poly-acronitrile (PAN-H). The pore size and pore size distribution were well controlled via changing the cast parameters. The results indicated that the PAN-H membrane can successfully separate vanadium ions from protons due to their difference in radius, charge density and specific interactions with electrolyte and membranes (Figure 9.14). The PAN-H membranes show very good potential in VFBs where they achieve a CE up to 95% and an EE of 76% at the operating condition of 80 mA cm. ... 

The static casting machines allow more control over casting parameters and are preferred for qnality and prodnctivity reasons [5,7]. Use of advanced computer control technology in the static... 

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