cellulose increases and has a maximum at a molar ratio of negative to positive charges
(nÀ/n+) of about 0.55–0.6.
Clay particles whose surfaces have been modified by the PC PDADMAC and the
sodium salt of the weak PA poly(maleic acid-co-α-methylstyrene), P(MS-α-MeSty),
were used as sorbents for removal of surfactants from aqueous solutions [46].
2.7 Dual Systems with Thermosensitive Polymers
A novel strategy for faster and better flocculation in solid–liquid separation processes
has been reported. The natural polyelectrolyte chitosan was used in combination with a
biocompatible thermosensitive polymer [poly(N-vinylcaprolactam); PNVCL]. The
flocculation of silica dispersions (Aerosil OX50) was evaluated using laser diffraction
and turbidimetry studies. The sedimentation velocity, which was determined with an
analytical centrifuge, was doubled by addition of PNVCL. Furthermore, at 45
C the
density of the sediment was 33% higher than when chitosan was used. This results
from the temperature-sensitive behavior of PNVCL, which phase-separates expelling
water at temperatures higher than its lower critical solution temperature (LCST;
32–34
C). By using this strategy, the sediment is more compact, contains less water,
and contains a very small amount of biodegradable chitosan and biocompatible
PNVCL.
The flocculation of clay using mixtures of chitosan and a thermosensitive polymer
was investigated as a function of the polymer concentrations and the temperature at
different pH values [47].
The compaction of TiO 2 suspensions [48] as well as the dewatering of inorganic
drinking water treatment sludge using dual ionic thermosensitive polymers was
described by Sakhohara [48, 49]. By using both cationic and anionic modified
PNIPAAm, the anionic thermosensitive polymer poly(NIPAM-co-AAC) in combination with cationic poly(NIPAM-co-AAC), the dewatering rate was remarkably
increased at relatively low temperatures. This increase was attributed to the formation
of a polymer complex that decreased the LCST of the polymer molecules adsorbed on
the sludge.
3 “Direct” Interaction Between the Flocculant (PC)
and an Anionically Charged Suspension
In contrast to the situation shown in Fig. 1 and described in Sect. 2, where different
interactions between two oppositely charged PEL on one side and the solid material
(fibers or particles) on the other side can occur, in this section we describe the
“direct” interaction between a flocculant (PC) and a charged suspension, which acts
like a PA. But, as shown in Fig. 1, the suspension can contain particles as well as
“soluble” anionically charged material.
40
G. Petzold and S. Schwarz
(nÀ/n+) of about 0.55–0.6.
Clay particles whose surfaces have been modified by the PC PDADMAC and the
sodium salt of the weak PA poly(maleic acid-co-α-methylstyrene), P(MS-α-MeSty),
were used as sorbents for removal of surfactants from aqueous solutions [46].
2.7 Dual Systems with Thermosensitive Polymers
A novel strategy for faster and better flocculation in solid–liquid separation processes
has been reported. The natural polyelectrolyte chitosan was used in combination with a
biocompatible thermosensitive polymer [poly(N-vinylcaprolactam); PNVCL]. The
flocculation of silica dispersions (Aerosil OX50) was evaluated using laser diffraction
and turbidimetry studies. The sedimentation velocity, which was determined with an
analytical centrifuge, was doubled by addition of PNVCL. Furthermore, at 45
C the
density of the sediment was 33% higher than when chitosan was used. This results
from the temperature-sensitive behavior of PNVCL, which phase-separates expelling
water at temperatures higher than its lower critical solution temperature (LCST;
32–34
C). By using this strategy, the sediment is more compact, contains less water,
and contains a very small amount of biodegradable chitosan and biocompatible
PNVCL.
The flocculation of clay using mixtures of chitosan and a thermosensitive polymer
was investigated as a function of the polymer concentrations and the temperature at
different pH values [47].
The compaction of TiO 2 suspensions [48] as well as the dewatering of inorganic
drinking water treatment sludge using dual ionic thermosensitive polymers was
described by Sakhohara [48, 49]. By using both cationic and anionic modified
PNIPAAm, the anionic thermosensitive polymer poly(NIPAM-co-AAC) in combination with cationic poly(NIPAM-co-AAC), the dewatering rate was remarkably
increased at relatively low temperatures. This increase was attributed to the formation
of a polymer complex that decreased the LCST of the polymer molecules adsorbed on
the sludge.
3 “Direct” Interaction Between the Flocculant (PC)
and an Anionically Charged Suspension
In contrast to the situation shown in Fig. 1 and described in Sect. 2, where different
interactions between two oppositely charged PEL on one side and the solid material
(fibers or particles) on the other side can occur, in this section we describe the
“direct” interaction between a flocculant (PC) and a charged suspension, which acts
like a PA. But, as shown in Fig. 1, the suspension can contain particles as well as
“soluble” anionically charged material.
40
G. Petzold and S. Schwarz