Flocculants performance

Addition Point. The flocculant addition point in a continuous system can also have a significant effect on flocculant performance. The turbulence as the flocculant is mixed in and the floes travel toward the point where they enter the thickener or filter causes both the formation and breakup of floes. Usually there is an optimal addition point or points which have to be determined empirically. In cases where the same polymer is being added at two or more points, the relative amounts added at each point may also affect performance. Thus providing multiple addition points in the design of new installations is recommended (56). 

Figure 1. Effect of reaction time on flocculation performance (0) 100 h and (O) 50 h at room temperature.

Figure 2. Effect of purification on flocculation performance (O) unpurified (0) purified by leaching with ethanol (A) purified by ultrafiltration.

An improvement in the flocculation ability of the purified cationic lignin ether due to an increase in the molecular weight is clearly seen in Figure 5. The same figure reveals a moderate gain in the flocculation performance relative to Praestol 41 IK when the cationic lignin ether had 3.4% N instead of 2.9% N as in the jar test shown in Figure 3a. 

Figure 4. Comparison of flocculation performance in stability test (a) against silica dispersion (b) against dredging effluent (O) cationic lignin ether (A) CH20-condensed cationic lignin ether (0) Praestol 411K.

Figure 5. Effect of molecular weight on flocculation performance of cationic lignin derivative (O) Indulin AT, Mw 23000, N 3.3% (A) Indulin AT, Mw 6300, N 3.7% ( ) Praestol 41 IK, Min-U-Sil 5 450 mg/liter.

Addition Point. The flocculant addition point in a continuous system can also have a significant effect on flocculant performance... 

PMBQ represents a special class of polyelectrolytes with hydrophobic functional groups, which tends to form aggregates in solution and exhibits a high affinity to hydrophobic surfaces. The presence of hydrophobic parts in PMBQ enhanced its flocculation performance in different dispersions. We have shown that formation of hydrophobic aggregates of PMBQ was responsible for the considerable broadening of the flocculation window that is extremely important and desirable for industrial application. 

In Suopajarvi s work [38], dicarboxylic acid nanocellulose [DCC] flocculants were produced by nanofibrillation of periodate and chlorite-oxidized celluloses with a homogenizer. The flocculation performance levels of five such anionic nanocelluloses with variable charge densities were examined in the coagulation-flocculation treatment of municipal wastewater and the results compared with the performance of a commercial coagulant and a synthetic... 

Harith ZT, Yusoff FM, Mohamed MS, Shariff M, Din M, Ariff AB. Effect of different flocculants on the flocculation performance of microalgae, Chaetoceros cakilrans cells. Afr J Biotechnol 2009 8 5971. 

Sam S, Kucukasik F.Yenigun O, Nicolaus B.Toksoy Oner E.Yukselen MA. Flocculating performances of exopolysaccharides produced by a halophilic bacterial strain cultivated on agro-industrial waste. Bioresom Technol 2011 102 1788—94. 

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