Removal, silica from water

Immiscible wetting in mixers Sol-gel processes Pellet flocculation <0.3 Low Up to 10 ton/hr Wet processing based on flocculation properties of particulate feed Coal fines, soot and oil removal from water Metal dicarhide, silica hydrogels Waste sludges and slurries... 

Where silica removal from raw water is not practiced, it is commonly managed by raising the alkalinity of the FW. However, high alkalinity water may lead to BW carryover, but simply reducing this high alkalinity without concern for silica removal is a recipe for disaster. Glassy silicate scales undoubtedly will occur. 

As summarized by Cassell et al. (ref. 36), the early work on microflotation described the removal of bacteria and algae from water (ref. 61, 62) thereafter, further studies demonstrated that B. cereus (ref. 63), colloidal constituents of tea (ref. 64), humic acid (ref. 65), colloidal silica (ref. 66), illite (ref. 67), titanium dioxide (ref. 68), and polystyrene latex (ref. 69) could be rapidly and efficiently removed from water by microflotation. The general variety of dispersed materials which have been separated successfully... 

SILICA REMOVAL FROM INDUSTRIAL PLANT WATER 173... 

Silica, both soluble and colloidal, can be removed from water to varying low levels in neutral or slightly alkaline solution by coprecipitation with insoluble metal... 

Several methods have been used to obtain quantitative extraction of conjugated bile acids from silica layers (4, 11, 12). Palmer (50) moistened the silica (removed from the plate with a razor blade) with water and extracted the bile acid by refluxing with chloroform-methanol (redistilled from 2,4-dinitrophenylhydrazine), 1 1, for one hr in a 250-ml round-bottom flask. He then determined the amount of bile acid with a 3a-hydroxysteroid dehydrogenase reaction. The necessity of using large volumes of polar solvent is also evident from the work by Shioda et al. (20) who used 50 ml of methanol-acetic acid, 99 1, and achieved at least 96% recovery of all common conjugated bile acids in human bile labeled in vivo by cholesterol. 

Solid Sorption. A material such as silica gel or activated aluminium through which the moisture-laden gas is passed achieves solid sorption see Fig. 9,18. The mass transfer that takes place depends on the relative conditions of the chemical and the air conditions. As the material becomes saturated, hearing the bed and applying a vacuum to it will reverse the process. Once sufficient water is removed from the material, it can be reused. 

No specific action usually is taken to remove silica (Si02) from MU water sources where the boiler plant operates at below 250 to 300 psig. Nevertheless, particularly undesirable FW line silica deposits may occur, and when this happens, often there is no simple, low-cost, practical way to remove them. 

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