Flocculation process polymer solution concentration

Dilution. In many appHcations, dilution of the flocculant solution before it is mixed with the substrate stream can improve performance (12). The mechanism probably involves getting a more uniform distribution of the polymer molecules. Since the dosage needed to form floes is usually well below the adsorption maximum, a high local concentration is effectively removed from the system at that point, leaving no flocculant for the rest of the particles. A portion of the clarified overflow can be used for dilution so no extra water is added to the process. 

Meanwhile, polymer molecular mass (M) decreases and duration of the process (t) as well (Figure 1). We continued flocculant synthesis until the volume of reaction solution stopped decreasing. The further prolongation of synthesis results in gradual increase of that volume due to hydrolysis of amide groups and formation of acrylic acid elements in the polymer. Sulphuric acid concentration also affects solubility and flocculating properties of the product. 

Usually, flocculating agents are received as solids or thick liquids. They are dissolved or diluted to low concentrations because the viscosity of polyelectrolyte solutions can be quite high. This can make it difficult to wet and disperse the material properly. The result of improper dispersion is the formation of lumps that dissolve extremely slowly and that are not effective in the process. A supplier reports that dilute solutions of a flocculant often give superior results and that multiple-point addition of the flocculant can improve its contact with the brine [91]. The polymers are sensitive to shear, and the agitation process must be chosen with care. Turbulence at the addition point(s) should provide good dispersion but not break the floes. 

Furthermore, PFOA can be separated from wastewater streams generated by the coagulation of fluoropolymers by an up-concentration process. After flocculation of residual polymer particles, the wastewater is set to pH 10 followed by a distillation in vacuum. This can be done using one or more distillation procedures. Up-concentration is continued until the emulsifier concentration reaches at least 5% of the aqueous solution. Then the pH is set to 1, and the free emulsifier acid is removed from the water by extraction with a suitable solvent and worked up further [46]. 

Another factor that affects the choice of the polymer concentration is the quantity to be used, compared with the quantity of process liquor. Once the size of the decanter has to be increased to cope with the extra volumetric load of the flocculant solution, then dilution has gone loo far. The flow of flocculant solution should be not more than, say, 10 or 1 5% of the feed rate, on this basis. 

Surfactants are essential for the preparation of solid/liquid dispersions (suspensions). The latter are generally prepared using two main procedures (7) Bmlding up of particles from molecular units. (2) Dispersion of bulk performed powder in a liquid followed by dispersion and wet milling (comminution) to produce smaller particles. An example of the first system is the production of polymer latex dispersions by emulsion or dispersion polymerization. The monomer is emulsified in an aqueous solution containing a surfactant to produce an emulsion of the monomer. An initiator is added to initiate the polymerization process. In some cases, initiation occurs in the micelles that are swollen by the monomer. The number of particles produced and hence their size is determined by the number of micelles in solution. In dispersion polymerization, the monomer is mixed with a solvent in which the resulting polymer is insoluble. A surfactant (protective colloid) and initiator is added. The surfactant prevents flocculation of the polymer particles once formed. Again the size of the particles produced depends on the nature and concentration of the surfactant used. 

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