Colloids and Surfaces B: Biointerfaces 91 (2012) 18–25 Contents lists available at SciVerse ScienceDirect Colloids and Surfaces B: Biointerfaces j our na l ho me p age: www.elsevier.com/locate/colsurfb The inhibitory effects of carboxymethyl inulin on the seeded growth of calcium carbonate Semra Kırboga, Mualla Öner ∗ Yıldız Technical University, Chemical Engineering Department, Davutpasa Campus, 34210 Esenler, Istanbul, Turkey a r t i c l e i n f o Article history: Received 5 July 2011 Received in revised form 13 October 2011 Accepted 13 October 2011 Available online 25 October 2011 Keywords: Crystal growth Calcium carbonate Constant composition Biopolymer Crystallization a b s t r a c t Kinetics of precipitation of calcite (CaCO 3 ) from aqueous solution in the presence of carboxymethyl inulin (CMI) was investigated under strictly controlled temperature, pH, supersaturation ratio (S = 4.8) and ionic strength (I = 0.1 M). The highly reproducible constant composition technique was used to study the influence of biopolymers of crystal growth of CaCO 3 , on CaCO 3 seed crystals at pH 8.5 and 25 ◦ C. The crystal growth of calcium carbonate (CaCO 3 ) was inhibited in the presence of CMI at low concentration (2.5 × 10 -9 to 25 × 10 -9 mol/L). The larger number of negatively charged functional groups exhibited a 95% growth rate inhibition at a concentration of 15 × 10 -9 mol/L. The higher inhibition efficiency is related to the maximum surface charge density due to adsorbed polymer. © 2011 Elsevier B.V. All rights reserved. 1. Introduction The growth of calcium carbonate is of considerable importance since it is frequently encountered both in nature and in industrial processes. Hence its precipitation is of particular interest not only for fundamental research concerning for biomineralization but also their importance in industrial applications [1–8]. The formation of calcium carbonate has been expressed in various circumstances such as gallstones, pancreatic stones in human and cattle, animal phyla, algae in mollusk shells and in human atherosclerotic aorta [9]. The balance organs of the inner ear of the vertebrates were found to contain polymorphs of calcium carbonate crystals, the same type of mineral as in limestone [10]. The occurrence of various types of mineral scales in industrial water systems is undesirable in various processes where water and water treatment are involved, such as desalination (thermal and membrane-based), boilers, filtration, oil and gas production and geothermal systems [11–13]. Calcium carbonate precipitation and crystal growth occur in water treatment and desalination applica- tion because the concentration of calcium carbonate is equal or bigger than the supersaturation level in natural waters [14,15]. Common water-formed scales such as calcium carbonate and cal- cium sulfate form readily on flow surfaces such as heat exchangers, membranes and other process equipment handling supersatu- rated waters [16,17]. These salts form hard and strongly adhering ∗ Corresponding author. Tel.: +90 212 383 47 40; fax: +90 212 383 47 25. E-mail addresses: skirboga@yildiz.edu.tr (S. Kırboga), oner@yildiz.edu.tr (M. Öner). deposits on the metallic surfaces and their formation is favored by the decrease of their solubility with increasing temperature. When deposited on equipment surfaces, the mineral scales coupled with corrosion products, microbiological mass and suspended matter. The formation of these deposits reduces heat transfer causing sig- nificant energy losses with the concomitant danger of overheating, reduces the internal diameter of pipes and increases the operat- ing pressure of pumps. Moreover, scaling is often accompanied with corrosion which leads to damage of the metallic parts of heat exchangers [18,19]. Several investigations have been carried out on the influence of scale inhibitors on both the precipitation and crystal habit modification of calcium carbonate forms [20–22]. Chemical compounds such as benzotriazole [23], polyamino polyether methylenephosphonate [24], aminotrimethylenephosphonic acid [24], humic, tannic and fulvic acids [25,26], salicylic acid [26b], benzene hexacarboxylic acid [26b,27], benzene 1,3,5-tricarboxylic acid [26b,27], acidic protein [28], poly(sodium 4-styrene sulfonate) [29], tetrahydrofurantetracarboxylic [30], cyclopentanetetracar- boxylic acid [30], citric acid [30], tricarballylic acid [30] are known as good crystal growth inhibitors of calcium carbonate. Polyacry- late and polyaspartic acid were shown to retard the spontaneous precipitation of calcium carbonate [26]. Polymers containing carboxylic groups such as, polyaspartate [31], polymaleic acid [31], double-hydrophilic block copolymer [32], polyacrylic acid [24,29] and carboxymethyl inulin [33,34] were found to be effective as calcium carbonate growth inhibitors. The different polymeric inhibitors with respect to their efficiency in the prevention of calcium carbonate crystallization have been investigated by Amjad et al. It has been shown that polyacrylic acid homopolymers were 0927-7765/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.colsurfb.2011.10.031