But, these aspects of complex application in medicine are not addressed in this
review and therefore they are not referred to in detail here.
6 Summary and Outlook
Polyelectrolytes and their complexes play a central role in solid–liquid separation
processes such as paper making or waste water treatment.
A lot of different products are available – synthetic as well as natural polymers.
Worldwide, the use of PECs is a fast growing market for treating water in different
spheres of life, such as the supply of drinking water, the purification of wash water,
or the dewatering of sludge.
The main message of this review is that many different ideas based on an
understanding of colloid–polymer interactions have been developed for solving
different problems, at first in the paper industry, but also for other technologies such
as the separation of metals (like alumina) or minerals, the dewatering of sludge, or
the removal of dyes.
The direct interactions between a flocculant (PC) and a charged particle suspension
have been investigated for many years and are not the topic of this review. But, it is
important to know (also for dual flocculation) that polymers with low molar mass can
flocculate via neutralization or patch flocculation mechanism, whereas polymers with
higher molar mass can flocculate via bridging. Decreasing the charge density of
polymers makes the flocculation range broader and the flocs bigger.
Because the separation problems have become more and more complex, new
principles of flocculation must be used to meet all requirements, such as the removal
of heavy metals, dyes, or natural colloids. Instead of monoflocculation with one
polycation, pre-mixed PECs (made from PC and PA), which are effective flocculants
due to their size and structure, are used. Because hydrophobic interactions are of
growing importance for the removal of hydrophobic substances such as oil, it is
necessary to introduce hydrophobic parts into the flocculants or, alternatively, to use
pre-mixed PSCs.
Last but not least, the flocculation efficiency of synthetic polymers should be
compared with natural polymers like chitosan, or with polysaccharides such as
modified starch, pectin, or alginate.
Acknowledgements We are indebted to many long-term collaborators and colleagues, especially
to Dr. Stela Dragan and her group (Institute Petru Poni, Iasi, Romania) and to Dr. Svetlana Bratskaya
(Far East Department of Russian Academy of Sciences, Institute of Chemistry, Vladivostok,
Russia). The investigations with tailored polymers, especially hydrophobic PCs, were undertaken
in collaboration with Prof. Laschewsky and his group (Fraunhofer IAP Golm, Germany). Above all,
we would like to thank our unforgettable colleague and friend Dr. Werner Jaeger.
Financial support from the BMBF and AiF is gratefully acknowledged.
Polyelectrolyte Complexes in Flocculation Applications
59
review and therefore they are not referred to in detail here.
6 Summary and Outlook
Polyelectrolytes and their complexes play a central role in solid–liquid separation
processes such as paper making or waste water treatment.
A lot of different products are available – synthetic as well as natural polymers.
Worldwide, the use of PECs is a fast growing market for treating water in different
spheres of life, such as the supply of drinking water, the purification of wash water,
or the dewatering of sludge.
The main message of this review is that many different ideas based on an
understanding of colloid–polymer interactions have been developed for solving
different problems, at first in the paper industry, but also for other technologies such
as the separation of metals (like alumina) or minerals, the dewatering of sludge, or
the removal of dyes.
The direct interactions between a flocculant (PC) and a charged particle suspension
have been investigated for many years and are not the topic of this review. But, it is
important to know (also for dual flocculation) that polymers with low molar mass can
flocculate via neutralization or patch flocculation mechanism, whereas polymers with
higher molar mass can flocculate via bridging. Decreasing the charge density of
polymers makes the flocculation range broader and the flocs bigger.
Because the separation problems have become more and more complex, new
principles of flocculation must be used to meet all requirements, such as the removal
of heavy metals, dyes, or natural colloids. Instead of monoflocculation with one
polycation, pre-mixed PECs (made from PC and PA), which are effective flocculants
due to their size and structure, are used. Because hydrophobic interactions are of
growing importance for the removal of hydrophobic substances such as oil, it is
necessary to introduce hydrophobic parts into the flocculants or, alternatively, to use
pre-mixed PSCs.
Last but not least, the flocculation efficiency of synthetic polymers should be
compared with natural polymers like chitosan, or with polysaccharides such as
modified starch, pectin, or alginate.
Acknowledgements We are indebted to many long-term collaborators and colleagues, especially
to Dr. Stela Dragan and her group (Institute Petru Poni, Iasi, Romania) and to Dr. Svetlana Bratskaya
(Far East Department of Russian Academy of Sciences, Institute of Chemistry, Vladivostok,
Russia). The investigations with tailored polymers, especially hydrophobic PCs, were undertaken
in collaboration with Prof. Laschewsky and his group (Fraunhofer IAP Golm, Germany). Above all,
we would like to thank our unforgettable colleague and friend Dr. Werner Jaeger.
Financial support from the BMBF and AiF is gratefully acknowledged.
Polyelectrolyte Complexes in Flocculation Applications
59