Complex flocculation

Through a series of solubility experiments, it has been proved that the presence of a water thin layer surrounding the surface particles was required to stabilize the CD/ferrocene inclusion complexes. Flocculation of gold nanoparticles has also been achieved by the same author using dimeric ferrocene guest (Figure 6). ... 

Colloidal behaviour is affected by the type of electrolytes present in the bulk solution, since dispersion occurs in the presence of monovalent cations, while with calcium ions the myo-inositol hexakisphosphate-goethite complexes flocculate (Celi et al., 2001). These findings have important environmental implications, since the charge-... 

Complex flocculation Flocculation by any of the four mechanisms described above can be accomplished by only one flocculant or retention aid. Much more effective flocculation and retention can be achieved by using combinations of retention aids. The most common combinations are between oppositely charged retention aids, which can form complexes of varying strength with each other. It is, however, also possible to use combinations of nonionic retention aids that can form complexes by hydrogen bonding. 

This apparent equivalent weight plays a great part a) in determining the spread of cations in the reversal of charge spectrum ( 21, p. 295) b) in the extent of the antagonism CaCIg — NaCl ( 5 b, p. 314-315) c) in complex flocculation or complex coacervation with positive protein sols (see p. 374 Ch. X 2r). 

By far the largest part of this chapter is devoted to complex coacervates and complex flocculations. Where possible a few words will be said in the appropriate sections on complex sols belonging to the same variant (p. 346, 392, 407, 413). 

In some cases (e.g. positive proteins -f negative phosphatides) complex flocculation is established rapidly at favourable mixing proportions of the colloid components but... 

As regards the influence of salts on complex coacervation or complex flocculation we have presented it as if only the valency of the cations or anions were of importance... 

The flocculations with Th(N03)4 and AICI3 form a separate category of complex flocculation because the flocculations once produced are no longer completely reversible by added indifferent salt. 

The soya bean phosphatide insoluble in alcohol has a very low I. E. P. and also a very low colloid equivalent weight, with which is connected the fact that even in aqueous medium (without addition of auxiliary substances, see note 3, p. 405) complex flocculation occurs with 3 and 2-valent cations. According to the N P ratio = 2 1 one can here expect a considerable admixture of phosphatidic acid. 

On the other hand we find complex flocculation or coacervation rather at relatively low electrolyte concentrations. They are the more pronounced the greater the charge density of the colloid. The effectiveness of the ions is in the main determined by their valency over which lyotropic influences are superposed. We sometimes find here that the sequence of the ions is just the opposite of that in the normal lyotropic series (for example of the monovalent anions, with the positive proteins, compare also p. 299, Fig. 22) and we have in this a clear indication of the complex character of the flocculation. 

In the continuation of the investigation on complex flocculation or complex coacervation a type was found which deviates completely from the types known up to now. ... 

A clear sol of purified egg lecithin (association colloid) does not flocculate immediately with La(N03)3 . Na-arabinate sol also gives no flocculation or coacervation with La(N03)g. The sol mixture of egg lecithin and Na arabinate similarly is clear. If however one adds a solution of La(N03)3 to a suitably chosen mixture of egg lecithin and Na arabinate sol, then flocculation immediately occurs in a definite range of concentrations. This flocculation completely bears the character of a complex flocculation. It becomes quickly suppressed on the addition of indifferent salts, (e.g. Co(NH3)6Cl3, CaClg, NaCl, K2SO4, K3CH(S03)3), in which the double vdency rule occurs ... 

The example given here does not stand alone. One can replace each of the three the egg lecithin, the salt and the acidoid, by suitably chosen others while retaining the typical complex flocculation (which thus only occurs if all three... 

It is already clear from this that the K , Na or NO3 ions can play no part (or on the contrary only a weakening role) in causing complex flocculation. For this there thus remain die constituents underlined each time in each combination. 

It has now further appeared that this colloid anion can also be replaced by suitably chosen micro anions, while retaining the typical complex flocculation. ... 

If a complex relation indicated by dots means that this is weak, a complex relation indicated by dashes that this is strong, then reaction equation of Fig. 51 has at once been adapted to that mode of production of complex flocculations which we have described in 6 a. 

The fact that complex flocculation does occur on mixing isoelectric gelatin, Mn(N03)2 and K-chondroitin sulphate must, according to the above given argument, mean that c + d is considerably greater than a + 6, which in view of the smallness of a and b seems not improbable. 

However, we note that carrageen combined either with isoelectric gelatin, or with egg lecithin, has a greater tendency to tricomplex flocculation than chondroitin sulphate (equivalent weights of the colloid anions nearly the same 271 and 280). This is manifest by the former giving complex flocculation with the divalent cations Mg , Ca, Sr , Ba and the monovalent Li while the latter is no longer able to do so. 

If one chooses a particular colloid amphoion (for example egg lecithin or isoelectric gelatin) and investigates with the aid of a number of cations and anions in what combinations of the latter ions complex flocculation occurs or not, one obtains a collection of data from which it is immediately clear that specific properties of the ions play a very great part. See Table 1 and 2 (p. 422 and 423). 

Or escape observation by the method employed here (sol -f- salt I salt II) if the bonds in the tricomplex system are very weak because the two ions of salt I and salt II, which do not take part in tricomplex formation (NO3 or Cl of salt I and K of salt II) form an indifferent salt which suppresses a very weak complex flocculation. Compare small print on p. 432 from which it appears that such a very weak tricomplex flocculation is possible with phosphatide -h Ca - - I. ... 

The same cation and anion sequences also occur in the suppression of Li tri-complex flocculation. See Fig. 59B and 60B. 

At and above the critical concentration, a sudden change in the arrangement of the particles occurs the previously well-dispersed and well-separated particles form complex networks. We found that dispersion led to a rather complex arrangement of phases, adsorbed layers, and finally even more complex flocculation structures in form of networks. Within the networks (Figure 1.8), the particles can touch and at least contact the next neighbors. The three-dimensional connectivity of the two-dimensional networks is being provided by the further complex three-dimensional arrangements and structures of the dispersion and flocculation layers. 

The addition of cationic surfactant to an anionic polysaccharide solution shows its greatest effect near the surfactant cmc. As the surfactant concentration increases beyond the cmc, the polysaccharide may go back into solution or it may form an insoluble complex, flocculate, and settle out of solution. In general, as the polysaccharide s anionic charge increases, so does its interaction with cationic surfactants. As an example, alginic acid binds more strongly to cationic surfactants than carboxymethylcellulose. 

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