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CHEMICAL TREATMENT FIGURE 1
increase the negative surface charge and keep particles in suspension. Cationic poly- mers can be used as dispersants, but this requires relatively high polymer concentra- tions to neutralize the negative surface charges and then transfer cationic charges to particles for effective dispersions. An increasingly important area of
study with high technological relevance is the suspension of clays, metal oxides, pigments, ceramic materials, and other insoluble particulate solids in aqueous systems through the use of small quanti- ties of synthetic polymers, polyphos- phates, and other polyelectrolytes. Amjad,1
in his study on the evaluation of
a variety of polymeric dispersants, re- ported that polymer architecture plays an important role in dispersing suspended matter in aqueous systems. A study by Dubin2
shows that acrylic and maleic
acid-based polymers performed better than polyphosphates and phosphonates as iron oxide dispersants. Several investigations have been car-
ried out on natural additives and bio- degradable and synthetic polymers as scale inhibitors and dispersants for water
TABLE 1
Additives tested as Fe2 Inhibitor
Starch
Alginic acid (Na) Tannic acid Fulvic acid
Lignosulfonate Poly(acrylic acid) Poly(maleic acid) Poly(acrylamide)
Poly(acrylic acid:2-acryalamido-2- methylpropane sulfonic acid)
Poly(acrylic acid:2-acryalamido-2-
methylpropane sulfonic acid:sulfonated styrene) Carboxymethyl inulin
Poly(diallyldimethyl ammonium chloride) NACE International, Vol. 51, No. 3
O3 dispersants
Functional Group Hydroxyl Carboxyl
Carboxyl, phenol Carboxyl, phenol
Sulfonic acid, phenol Carboxyl Carboxyl Amide
Carboxyl, sulfonic acid Carboxyl, sulfonic acid Carboxyl Quaternary ammonium
Ionic Charge Neutral
Negative Negative Negative Negative Negative Negative Neutral
Negative Negative
Negative, neutral Positive
Acronym ST
ALG TA FA LS
P-AA P-MA P-AM
P-AA:SA P-AA:SA:SS
CMI-15,-20-,-25 PDAC
March 2012 MATERIALS PERFORMANCE 49
treatment applications.3-5
Results of these
studies reveal that homopolymers of acrylic, maleic, and aspartic acids are effective scale inhibitors; however, these additives exhibit poor performance as iron oxide dispersants. Acrylic acid and maleic acid-based copolymers, on the other hand, are excellent inhibitors for calcium phosphate and calcium phospho- nate scales6
but show mediocre perfor-
mance as inhibitors for calcium carbon- ate (CaCO3
gypsum (CaSO4•2H2
KITKQ]U Æ]WZQLM +I.2 O) scales.7-9
), and There is increasing interest in the
development and application of biode- gradable, environmentally friendly bio- polymers. Carboxymethyl inulin (CMI) is a chemical derivative produced by carboxymethylation of inulin, a polysac- charide-based polymer present in the roots of the chicory plant. The perfor- mance of CMI as an inhibitor for CaCO3
, calcium oxalate (CaC2
barium sulfate (BaSO4 ported.10-12
O4 ), and ) has been re- Results of these studies reveal
that CMI is an effective inhibitor for various scales. In another study, Zeiher13 evaluated the performance of polysac-
Structure of CMI. Original source: K.D. Demadis, I. Léonard, "Green Polymeric Additives for Calcium Oxalate Control in Industrial Water and Process Applica- tions,"
50, 10 (2011): p. 41.
charide-based hybrid polymers for scale inhibition and dispersion. The results show that the biopolymers perform well vs. currently used polymeric scale in- hibitors and dispersants. The present work is concerned with the evaluation of CMI as an iron oxide (rust) dispersant. .WZ XMZNWZUIVKM KWUXIZQ[WV ZM[]T\[ IZM also presented on natural additives and synthetic polymers commonly used in water treatment formulations.
MP