Ultrafiltration electrocoat paint

FIGURE 31 An ultrafiltration electrocoat paint recovery system. [Warashina et al. (1985, September). Chemtech, pp. 558-561.]... 

Figure 6.5 Ultrafiltration flux as a function of time of an electrocoat paint latex solution. Because of fouling, the flux declines over a period of days. Periodic cleaning is required to maintain high fluxes [14]. Reprinted from R. Walker, Recent Developments in Ultrafiltration of Electrocoat Paint, Electrocoat 82, 16 (1982) with permission from Gardner Publications, Inc., Cincinnati, OH...

Because of the challenging environment in which ultrafiltration membranes are operated and the regular cleaning cycles, membrane lifetime is significantly shorter than that of reverse osmosis membranes. Ultrafiltration module lifetimes are rarely more than 2-3 years, and modules may be replaced annually in cheese whey or electrocoat paint applications. In contrast, reverse osmosis membranes are normally not cleaned more than once or twice per year and can last 4-5 years. 

Figure 6.15 Effect of membrane surface charge on ultrafiltration flux decline. These membranes were used to ultrafilter cathodic electrocoat paint, which has a net negative charge. Electrostatic repulsion made the negatively charged membrane significantly more resistant to fouling than the similar positively charged membrane [13]...

Figure 6.21 Flow schematic of an electrocoat paint ultrafiltration system. The ultra-filtration system removes ionic impurities from the paint tank carried over from the chromate/phosphate cleaning steps and provides clean rinse water for the counter-current rinsing operation...

R. Walker, Recent Developments in Ultrafiltration of Electrocoat Paint, Electrocoat 82, 1 (1982). 

Cross-flow filtration (CFF) also known as tangential flow filtration is not of recent origin. It began with the development of reverse osmosis (RO) more than three decades ago. Industrial RO processes include desalting of sea water and brackish water, and recovery and purification of some fermentation products. The cross-flow membrane filtration technique was next applied to the concentration and fractionation of macromolecules commonly recognized as ultrafiltration (UF) in the late 1960 s. Major UF applications include electrocoat paint recovery, enzyme and protein recovery and pyrogen removal. 

Abcor (now a division of Koch Industries) installed the first industrial ultrafiltration plant to recover electrocoat paint from automobile paint shop rinse water in 1969. Shortly afterwards, systems were installed in the food industry for protein separation from milk whey and for apple juice clarification. The separation of oil emulsions from effluent wastewaters has also become a significant application. The current ultrafiltration market is approximately US 200 million/ year, but because the market is very fragmented no individual end-use segment is more than US 10-30 million/year. In the chemical and refining industries, the principal application of ultrafiltration is the treatment of oily wastewater. 

Fig. 31. Ultrafiltration flux as a function of time of an electrocoat paint latex solution. Because of fouling, the flux declines over a period of days. Periodic cleaning is required to maintain high fluxes.

Spiral-wound membrane modules, with hydrophilic membranes, are suited for water-based paint recovery in spray paint installations, and also for electrocoat paint filtration. Figure 4.32 shows a schematic for an ultrafiltration system for treating spray booth waste. 

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