Proteins flocculation/coagulation

Wastewater Treatment Removal of metal ions, flocculant/coagulant, protein, dye, amino acids... 

The nature of chemical coagulants are such that the macrofloc may possess certain charges for example lime (CaO), alum (A1203) and flocculating polyvalent cations cany positive charges, which interact with proteins. The interactions are simply illustrated in Figure 7.6. 

Non-sulfonated lignins find utility as emulsifiers and stabilizers in water-based asphalt emulsions, as coreactants in phenolic binder applications, as negative plate expanders in lead acid storage batteries, as protein coagulants in fat rendering, and as flocculants in waste water systems. 

Tphe kinetics of the protease-triggered clotting of blood and milk has been formulated in a number of recent publications from this laboratory (1,2,3). In milk clotting, the coagulation is initiated through the limited proteolysis of -casein, the milk protein component which normally protects the casein micelles from flocculation by calcium ions (4). Kappa-casein is a single polypeptide chain of 169 residues, the sequence... 

In a previous paper Bancroft and Richter3 have confirmed the hypothesis of Claude Bernard that anesthesia is due to the reversible coagulation of the colloids of the sensory nerves. It appeared that the proteins were the important factors rather than the lipoid materials. If we have different proteins in different parts of the body we shall expect them to be flocculated reversibly to different extents by different drugs. Claude Bernard pointed out that the anesthetics affect the brain first but the sensory nerves very soon after, while the narcotics affect the brain much more readily than the sensory nerves. Morphine will, therefore, tend to drive chloroform from the brain to the sensory nerves, thereby increasing the anesthetic effect of the chloroform. 

Contrary to "association" the terms "aggregation", "coagulation", and "flocculation" refer to unspecified protein-protein interactions and the formation of complexes with higher molecular weights. 

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. 

The tendency for proteins to form thick membranes, as a result of interfacial coagulation, needs to be taken into account, especially in emulsions since it occurs more easily at oil/water than at air/water interfaces. These thick films can present a steric barrier simply by preventing the dispersed phase in the droplets from coming into contact. On the other hand, because of their gelatinous and cohesive nature, they are likely to produce flocculation. 

For proteins, related topic is flocculation and coagulation. Section 9.3. 

Bovine albumin was adsorbed on quartz and amorphous silica powders at a maximum around pH 6 and was in equilibrium with that adsorbed (252). However, Her (253) found that the pH, below which enough albumin was adsorbed to cause flocculation of colloidal silica, depended on the salt concentration. With no NaCl present it was pH 4.4, but in 0.1 N solution was 6.2. It was also noted that when the surface of the silica was only 5% covered with aluminosilicate anions, no coagulation occurred in 0.1 N NaCl solution above pH 5.5. Thus colloidal aluminosilicates (clays) which bear a higher anionic charge than pure silica does in neutral solution, are less reactive with some proteins... . ... 

Tannery High COD and SS, Contains oils and fats, proteins, sulphide chrome, salts Screening, coagulation and flocculation, settlement or flotation prior to biological filter Aluminium or ferric sulphate followed by anionic polyacrylamide... 

Slaughterhouse High dissolved and colloidal COD and SS. Contains fats and protein (blood), dirt and manure Grit chamber, screen, coagulation and flocculation, DAF Aluminium or ferric sulphate or PAC followed by cationic or anionic polyacrylamide... 

Heat-CoaguUUion.— Albumins and globulins differ from all the other proteins in being coagulated when heated in aqueous solution. The change is preceded by heat-denaturation, which is favoured by an acid reaction then the insoluble protein particles flocculate or coagulate, a change which takes place best in presence of neutral electrolytes, such as NaCl, about pH 5-7-pH 5-9. 

The combination of lime and heat forms a flocculent-type precipitate with various components in the juice, which consist mostly of insoluble lime salts, coagulated protein, and entrapped colloidal and suspended matter. The precipitate is removed by sedimentation or settling in continuous closed-tray clarifiers (i.e., Rapi-Dorr, Graver, BMA, and Bach Poly-Cell). The juice leaving the clarifier is a clear brownish liquid. 

In the present work, three aggregation mechanisms have been considered to explain the experimental results at short aggregation times (1) coagulation, where bonds are formed between two uncovered surface patches of the colliding particles (2) weak flocculation, that is, two covered patches and (3) pure bridging flocculation, where the collision of an uncovered part of one particle with the covered part of another particle occurs. In this configuration, a protein bridge will form between the particles. 

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