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CHEMICAL TREATMENT FIGURE 3
mers of acrylic acid, maleic acid, acryl- amide, and acrylic acid-based copolymers containing different functional groups).
Dispersant Performance Using the experimental procedure
outlined above, a series of experiments was conducted to evaluate the perfor- mance of polymers as dispersants for Fe2
O3 . The experiments were designed
\W \M[\ \PM MNÅKIKa WN XWTaUMZ[ I[ I N]VK- tion of dispersion time, polymer dosage, and polymer type (i.e., bio, natural, syn- thetic, etc.).
Biopolymer CMI-20 as Fe2
Figure 2 details the performance of O3
dispersant at varying
polymer dosages and as a function of time. There are two points worth noting: a) %D value increases with increasing time and b) %D value increases with in- creasing polymer dosages. For example, %D values obtained in the presence of 1.0 ppm CMI-20 at 1/2 h and 1 h are 14 and 20%, respectively. It is evident from Figure 2 that increasing the dispersion time by a factor of 3 (i.e., from 1 to 3 h) causes a ~45% increase (from 20 to 29%) in %D value. Thus, it is clear from Figure 2 that dispersion time (i.e., polymer con- tact time with Fe2
O3 important role in dispersing Fe2
particles) plays an O3
par-
ticles in an aqueous solution. It is worth pointing out that similar dispersion time dependence of polymer performance, as observed in the present study, has also been reported for hydroxyapatite.14 The effect of polymer dosage on Fe2
O3
dispersion also was studied. Results pre- sented in Figure 2 show that CMI-20 performance strongly depends on poly- mer dosages. For example, %D values obtained at 3 h in the presence of 0.25 and 0.50 ppm of CMI-20 are 17 and 23%, respectively. It is interesting to note that increasing polymer dosage by two- fold (i.e., from 0.50 to 1.0) leads to only a
NACE International, Vol. 51, No. 3
~30% increase (from 23 to 29%) in %D value. The data presented in Figure 2 clearly show that polymer performance depends on both the dispersion time and the dispersant dosage.
investigated. Results obtained at 3 h in the presence of 1.0 ppm of CMI-15, CMI-20, and CMI-25 are illustrated in Figure 3. It can be seen that polymer performance as an Fe2
O3 dispersant in-
creases with increasing carboxylation. For example, %D values obtained for
CMI-15 and CMI-20 are 20 and 29% compared to 35% obtained for CMI-25. For comparison, %D value for starch is also plotted in Figure 3. It is evident from Figure 3 that the greater the carboxyl content present in inulin, the higher the dispersancy value of the biopolymer.
Natural Additives Natural additives such as starches,
alginates, and lignosulfonates have been used for years to disperse particulate mat- ter in industrial water systems. These polymers function as dispersants, but
March 2012 MATERIALS PERFORMANCE 51 Fe2
carboxylation. FIGURE 4
O3 dispersion in the presence of 1.0 ppm of various CMI of different
Fe2
O3
dispersion in the presence of 1.0 ppm of various natural dispersants.