Flocculation aids

Coagulation involves neutralizing charged particles to destabilize suspended soflds. In most clarification processes, a flocculation step then follows. Flocculation starts when neutralized or entrapped particles begin to colUde and fuse to form larger particles. This process can occur naturally or can be enhanced by the addition of polymeric flocculant aids. 

Used industrially in the manufacture of pharmaceuticals, textile chemicals, adhesives, binders, petroleum refining chemicals, fuels, lubricants, coating resins, varnishes, polymerizations, lacquers, agricultural chemicals, cosmetics, ion exchange resins, photographic chemicals, surfactants used in the paper industry and as a flocculation aid. 

Alum dosages between 200 and 500 mg/1 were not significantly different. Table II also Illustrates that sedimentation Is effective In lowering the concentration of the pesticides to the solubility limit. Metrlbuzln Is soluble In water to a concentration of about 1200 mg/1 and the sedimentation step reduced the concentration from 2000 and 3000 mg/1 to about 1000 mg/1. At lower concentrations sedimentation was not effective. Other coagulants and flocculant aids such as hydroxide and ferric chloride, were tested but alum with an anionic polymer (Watcon 1255) was the most effective. 

Uses. Organic syntheses production of poly-ethyleneimines used in the paper industry and as flocculation aids in the clarification of effluents... 

Polymers of N, N, N, A-diallyldimethylammonium chloride (DADMAC) (and its copolymers with acrylamide) are allyl resins in terms of the monomers used but are very different in properties since they are not crosslinked. Cyclopolymerization is the mode of reaction (Sec. 6-6b) and the polymers are water-soluble. Applications include potable and wastewater treatment (flocculation aid) and paper and textile industries (antistatic coating, reinforcement, color removal). 

Eliminates the need for clarifiers, polymers, or flocculation aids. 

The treatment of ADUF by reverse osmosis [13] was found to be useful in concentrating activity in small volume while making a larger volume of the decontaminated effluent for direct disposal after required dilution. Porous cellulose acetate membranes were used in plate module configurations. The concentration of ammonium nitrate in the permeate stream is not very different from that of the contaminated retentate. With the addition of flocculating aids, the decontamination factors in the range of 1000 with VRFs in the range of 100 were achieved. 

The optimum pH for flocculation is about 6.5 to 7.5 for aluminum salts and about 8.5 for iron salts. If the natural alkali content of the untreated water is insufficient to neutralize the acid formed, alkali has to be added (e.g. calcium hydroxide or sodium hydroxide). In addition flocculation aids such as poly(acrylamide) or starch derivatives may be added (not in the case of potable water production). When aluminum sulfate Al2(S04)3 I8H2O is used 10 to 30 g/m- is added. The very fine hydroxide flakes which precipitate are positively charged and adsorb the negatively charged colloidal organic materials and clay particles. 

After the enzymatic treatment the juice can be clarified. Flocculation aids and fining aids (gelatine, silica sol, etc.) help to coagulate the cloudy substances and facilitate their separation by settling and filtration. Bentonites can be used to eliminate proteins and other cloudy substances. Filtration (Kieselgur precoat filtration with plate and frame filters, rotating vacuum filters, and sheet filters as police filters ) is used to produce a crystal clear juice. 

Preliminary studies using water-soluble CDACs as a biopolymeric flocculation agent indicate that they have a high potential for use as new, environment-friendly flocculation aids. Further studies on the use of CDAC as a flocculation agent are currently under way [39]. 

Toxicology Irritant TSCA listed Uses Flocculating aid paper sizes ion exchange resins antistatic finishing hydrophilic glass fibers superabsorbents toner polymers thickeners cement additives anticorrosives adhesives cosmetics prod, of acrylamide copolymers Manuf./Distrib. Aldrich http //www.sigma-aldrich.com... 

Plant Application of Precipitation Technology. This section begins with a discussion of the sources of the major treating chemicals. It then turns to process operating parameters, the design of the reaction tanks, the use of polymeric flocculation aids to improve particle characteristics, and some of the specific considerations necessary when using carbon dioxide gas as the source of the carbonate ion. 

Polymers normally used as coagulant aids or flocculation aids , where the main purpose is to strengthen and increase the size of floes and improve particle capture after coagulation has taken place, are the polyacrylamides of non-ionic, or low to medium cationic or anionic charge. The latter type of polymer also finds application in the dewatering of the sludges produced from clarification treatment of potable water [50]. 

In some applieations, where the solid particles are too fine to separate on their own, it is necessary to use a flocculating aid. The Hocculant can be added upstream of the decanter, but there are many circumstances where, for best efficiency, it is admitted in the bowl. On these occasions there will be an extra chamber, the floe zone", built into the hub of the conveyor. Where necessary this floe chamber can be used as a rinse chamber instead, to admit rinse liquor onto the scrolling cake,... 

The principle of the experimental arrangement of the FOFS is shown schematically in Fig. 2. The medium to be flocculated is turbulendy mixed with the solution of the flocculation aid in a mixing chamber, which achieves rapid homogeneous distribution of both the components. Flocculation takes place slowly under defined shear conditions in a region of laminar flow. The length of the laminar-flow tube can be matched to the applicable practical conditions. 

Screening method for assessing the effectiveness of flocculation aids for waste water treatment... 

The time of day, the actual flocculation aid concentration, the change in the flocculation value in comparison with the previous concentration step (dF), and the absolute flocculation value (F) are given the bar chart corresponds to the flocculation curve shown before. The optimal flocculant concentration is defined as that at which increasing of the Sedipur concentration twice no longer increases the flocculation value by more than 20%. On the basis of this Sedipur concentration, which is transmit-... 

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