Skin-type membranes

Figure 14 Concentration profiles of the precipitant in the casting solution at various times during the formation of an asymmetric skin type membrane.

Skin Type Membranes With "Sponge"- and "Finger -Like Structures. In... 

Although most aspects of the formation of asymmetric skin type membranes can satisfactorily be rationalized by applying the basic thermodynamic and kinetic laws of phase separation processes, there are other parameters, such as surface tension (16), polymer relaxation (J ), solvent loss by evaporation (Jg), etc., which are not directly related to the phase separation process, but nevertheless will have a strong effect on the membrane structure and properties. 

Skin Type Membranes With "Sponge"- and "Finger"-Like Structures. In skin-type membranes, the two characteristic structures shown in Figure 1.14 are obtained. One is a sponge-like structure and the other is a finger-like substructure underneath the skin. 

Reverse osmosis Symmetric skin-type membrane Hydrostatic pressure, 20 to 100 bar Solution-diffusion mechanism Separation of salt and microsolutes firom solutions... 

In skin-type membranes, like hollow fibre membranes, two characteristic structures can be formed. One structure is sponge-like below the skin, and one has finger-shaped pores below the skin. These finger-shaped pores can be clearly seen in the polyetherketone hollow fibre (see Fig. 11.5)." " " ... 

The monomers, eatalysts or hardeners, or plastieizers ean inelude ehemieals with the potential to irritate the skin, mueous membranes or respiratory traet. Some ean promote skin or respiratory sensitization. The range of ehemieals in use is extremely wide, so that referenee should be made to the Materials Safety Data Sheet for eaeh speeifie formulation or variation of it identifiable by referenee to the supplier s proprietary name and eode number. Some eommon resin types are summarized in Table 5.55. 

The patient is at risk for Stevens-Johnson syndrome when taking the cephalosporins StevensJohnson syndrome is manifested by fever, cough, muscular aches and pains headache, and the appearance of lesions on the skin, mucous membranes and eyes The lesions appear as red wheals or blisters often starting on the face, in the mouth, or on the lips neck, and extremities This syndrome, which also may occur with the administration of other types of drugs can be fatal. The nurse should report any of these symptoms to the primary health care provider immediately. 

Table 10.9 Various types of ulcers along with their underlying cause. An ulcer may simply be described as a break or cut in the skin or membrane lining the digestive tract which fails to heal. The damaged area may then become inflammed...

The principal adverse reaction to warfarin is hemorrhage. Prolonged therapy with the coumarin-type anticoagulants is relatively free of untoward effects. Bleeding may be observable (e.g., skin, mucous membranes) or occult (e.g., gastrointestinal, renal, cerebral, hepatic, uterine, or pulmonary). Rarer untoward effects include diarrhea, small intestine necrosis, urticaria, alopecia, skin necrosis, purple toes, and dermatitis. 

Symmetric membranes and asymmetric membranes are two basic types of membrane based on their structure. Symmetric membranes include non-porous (dense) symmetric membranes and porous symmetric membranes, while asymmetric membranes include integrally skinned asymmetric membranes, coated asymmetric membranes, and composite membranes. A number of different methods are used to prepare these membranes. The most important techniques are sintering, stretching, track-etching, template leaching, phase inversion, and coating (13,33). 

Table XI. Effect of Thermal Annealing upon the Indices of Refraction and Water Contents of Skin and Substructure Layers of Loeb-SourIrajan-type Membranes...

Addition of a Nonsolvent to a Homogeneous Polymer Solution. This technique is widely used today for the preparation of symmetric microfiltration membranes as well as for manufacturing asymmetric "skin-type" ultrafiltration or reverse osmosis membranes (7). The preparation procedure can again be rationalized with the aid of a three-component isothermic phase diagram shown schematically in Figure 3. 

Agent Index A318 Class Index C27 Monkey Pox Type Virus Clinical symptoms closely resemble small pox and include extreme fatigue, fever, muscular and back pain, with evolution of maculas progressing successively to papules, vesicles, pustules, and scabs. Routes Inhalation Abraded Skin Mucous Membranes Secondary Hazards Aerosol Contact Body Fluids Fomites Incubation 7 to 15 days Mortality Rate < 15% Reservoir Monkeys, Squirrels Direct Person-to-Person Transmission is possible. 

Sodium hypochlorite is highly corrosive causing damage to the skin, mucous membranes and eyes. All personnel handling or using hypochlorite should wear chemical type goggles, overalls which are resistant to chemicals, plastic or rubber gloves and rubber boots. 

Immunologic Exposure to latex is associated with three clinical syndromes irritant dermatitis, delayed hypersensitivity reactions, and the most serious, but least common, immediate or type 1 hypersensitivity. Exposure to latex can occur through the skin, mucous membranes, or airways. Gloves used for examination, surgical or household, are often the cause of allergic reactions. 

As pointed out by Nunes and Peinemann [108], inorganic membranes are usually preferred because many processes at the industrial level are carried out at high temperature. However, polymeric membranes can be used for H2/hydrocarbon separation in the platformer off gases from refineries and for CO2 separation in coal plants. Polymeric manbranes for GS can be symmetric or asymmetric, but should have a dense selective layer. Three types of membrane structures can be employed (1) homogeneous dense manbranes (symmetric) (2) integrally skinned asymmetric membranes and (3) composite membranes. 

---