Ozone resistant membrane

Topics in Appiication Technoiogy Ozone-Resistant Membrane and Ozone Microfiitration Systems... 

Sugimoto, K., and Ogasawara, H. (2005). Development of a sewage reuse process using ozone-resistant membranes. In Proceedings International Forum on Water Industry Qingado 2005, Qingado, China, pp. 271-279. 

Although the material most used for single-ply membranes is EPDM, in competition with it are several other materials— Du Pont s Hypalon (a chlorosulfonated polyethylene), its Neoprene products, and modified PVC. It is believed that future growth in the roofing market will depend on products, such as Hypalon, that are easy to handle and have good ozone resistance, and on PVCs modified with polymeric plasticizers. 

Silicone is used in membrane-ozonizers because of its high ozone resistance [699]. 

The sulfonation of polyethylene membranes was examined under various experimental conditions and the results showed that sulfonation greatly enhanced the water permeability of the resultant membranes. A lower concentration of chlorosulfonic acid at low temperature was preferable, so that only the surface and inner walls of the polymer were sulfonated and the mechanical properties of the membrane were not damaged. The electromicroscopy of polythene is facilitated by staining the polymer by immersing pieces of the polymer in chlorosulfonic acid at 60 °C for several hours. Chlorosulfonated polyethylene rubbers are useful for specific purposes, e.g. as ozone-resistant hoses. ... 

However, we have succeeded in the development of ozone-resistant filtration modules by developing PVDF hollow-fiber membranes and potting materials having a high resistance to ozone, and assembling technology (Mori et al., 1998). 

In addition, we have designed a new filtration system using our new ozone-resistant MF module in conjunction with ozone (Hashino et al., 2000). In this system, filtration was carried out at low pressure and low linear velocity and with air scrubbing to remove cake layer on the membrane. This system can provide a high permeate flux consistently for various types of water, especially as in the case of highly turbid raw water and secondary treated municipal wastewater. 

Module Structure Figure 5.5 shows an ozone-resistant module. FUtrafion takes place from outside to inside of the hoUow-fiber membrane. The module is designed to feed raw water under high Unear velocity, and air can be fed for the air scmbbing. This module is constructed by hoUow-fiber membranes, potting material, and housing, and ozone resistance is required for aU of these materials. 

More than 800 million pounds of EPM and EPDM polymers were produced in the United States in 2001. Their volume ranks these materials fourth behind styrene-1,3-butadiene copolymers, poly( 1,4-butadiene), and butyl rubber as synthetic rubbers. EPM and EPDM polymers have good chemical resistance, especially toward ozone. They are very cost-effective products since physical properties are retained when blended with large amounts of fillers and oil. Applications include automobile radiator hose, weather stripping, and roofing membrane. 

Additional curing is often achieved with sulfur, peroxide, or maleimide formulations. Chloro-sulfonated polyethylene has improved resistance to oil, ozone, and heat compared to many other elastomers. Applications include harrier membranes and liners, surface coatings on fabrics, automobile air-conditioner hose, electrical cable insulation, and spark-plug boots [Andrews and Dawson, 1986],... 

Plant susceptibility to ozone as determined by visible injury may be very closely related to quantities of o-diphenols associated with the chloroplasts and specific requirements for activation of polyphenol oxidase enzymes. There is a significant correlation between ozone injury and concentrations of total phenols expressed as percent caffeic acid equivalents in peanut cultivars. This concept is not intended to underestimate the importance of membranes that separate phenols and enzymes. Perhaps future research will demonstrate that membranes of resistant alfalfa, green bean and other species differ both qualitatively and quantitatively from those of susceptible plants of these species. 

Contacting ozone gas with water can be achieved with every kind of gas diffuser, which is made of a material resistant to ozone. Ring pipes, porous diffusers and porous membranes, injector nozzles as well as static mixers can be employed. The different types of diffusers are mainly characterized by the diameter of the bubbles produced, e. g. micro (dB = 0.01 — 0.2 mm), small (dB 1.0 mm) or big (dB - 2.5 mm) bubbles (Calderbank, 1970 Hughmark, 1967). 

When using an amperometric electrode as the measuring technique, interference from the solutes and solvent can occur. The solutes and solvent can adsorb to the semipermeable membrane of the electrode, therefore giving an additional resistance to the diffusion of ozone through this membrane to the electrolyte chamber. The use of an amperometric electrode is not recommended for water containing particles. In these cases the ozone consumption can only be calculated from the ozone gas balance. 

The respiratory alveolar epithelial response to toxic injury can be rapid, resulting in necrosis and subsequently sloughing of the sensitive type I cells. This type of response is seen with exposure to such toxicants as ozone, nitrogen dioxide, and butylated hydroxy toluene. This injury stimulates the proliferation of the more resistant type II cells. This proliferative response typically peaks at 48h after onset of the initial injury to the type I cells. The increase in number of type II cells can be expected to alter the diffusion capacity of the pulmonary region through populating this membrane with these thicker cells. 

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