Double-Hydrophilic Block Copolymers as Precipitation Inhibitors for

Aug 27, 2010 - and maleic anhydride (MA)rammonium allylpolyethoxy sulfate (APES), were specially designed and synthesized from allyloxy polyethoxy eth...
0 downloads 0 Views 2MB Size
Download PDF
8920

Ind. Eng. Chem. Res. 2010, 49, 8920–8926

Double-Hydrophilic Block Copolymers as Precipitation Inhibitors for Calcium Phosphate and Iron(III)† Fu Change,‡,§ Zhou Yuming,*,‡ Xie Hongtao,‡ Sun Wei,| and Wu Wendao| School of Chemistry and Chemical Engineering, Southeast UniVersity, Nanjing 211189, P. R. China, Nanjing College of Chemical Technology, Nanjing, 210048, P. R. China, and Jiangsu Jianghai Chemical Co., Ltd., Changzhou 213116, Jiangsu, P. R. China

Novel double-hydrophilic block copolymers, maleic anhydride (MA)-allylpolyethoxy carboxylate (APEC) and maleic anhydride (MA)-ammonium allylpolyethoxy sulfate (APES), were specially designed and synthesized from allyloxy polyethoxy ether (APEO) to inhibit the precipitation of calcium phosphate and iron (III). Structures of APEO, APEC, MA-APEC, APES, and MA-APES were characterized by FT-IR. The study shows that both MA-APEC and MA-APES have significant ability to inhibit the precipitation of calcium phosphate at the dosage of 6 mg/L, approximately showing 99 and 90% inhibition, respectively. The data of the light transmittance of ferrous solutions show that, compared to MA-APES, MA-APEC has superior ability to stabilize iron (III) in solutions. The light transmittance of ferrous solutions is about 23% in the presence of MA-APEC when the dosage is 6 mg/L, whereas in the presence of MA-APES, it is about 31% at a dosage of 12 mg/L. Scanning electron microscopy (SEM) shows that the copolymers influence the morphology of calcium phosphate crystallites. Transmission electron microscopy (TEM) indicates the excellent inhibition results from the formation of core-shell structure. Double-hydrophilic block copolymers of MA-APEC and MA-APES have also been proven to be effective inhibitors of calcium phosphate and iron (III) even at elevated solution temperature, pH, and Ca2+ and Fe2+ concentration. 1. Introduction Calcium phosphate is frequently encountered as precipitation and deposition onto the most critical equipment surfaces within industrial recycling water systems which greatly diminishes effective heat transfer, interferes with fluid flow, facilitates corrosion processes, can worsen microbiological fouling, and in some cases can even cause catastrophic operational failures in cooling-water applications.1-3 The inhibition or prevention of calcium-phosphate formation by the addition of trace amounts of inhibitors is therefore of considerable interest.4,5 Polycarboxylate- and polyphosphonatetype inhibitors are effective inhibitors of calcium phosphate growth.6-9 These inhibitors are primarily designed for their ability to form a sufficient number of coordinative bonds with inorganic metal ions and achieve scale inhibition through adsorption at active crystallite growth sites on the surfaces of crystallites.10-12 This adsorption prevents further crystallite growth and agglomeration into larger aggregates. However, inhibition or dissolution of such calcium-phosphate deposition by the current inhibitors is unsatisfactory. Polyphosphonate inhibitors easily lead to the formation of orthophosphate because of their own hydrolysis or decomposition, and orthophosphate itself can react with calcium ions to form relatively insoluble calcium-phosphate scale.4,5,8 Furthermore, polyphosphonate, when reverted to orthophosphate, is a potential nutrient for algae.13 Another type of the current inhibitors is polycarboxylate, which has low calcium tolerance, and those inhibitors will react with calcium ions to form insoluble calcium† National Nature Science Foundation of China (50873026); Science and Technology Support Program, Jiangsu Province of China (BE2008129); Science and Technology Projects on Production, Teaching and Research, Changzhou, Jiangsu Province of China (CV20090002). * To whom correspondence should be addressed. E-mail: changeby@ 163.com. Tel.:86-25-52090617. ‡ Southeast University, Nanjing. § Nanjing College of Chemical Technology. | Jiangsu Jianghai Chemical Co., Ltd.

polymer salts.8,9,14 Thus, novel inhibitors should be further developed to offer high calcium tolerance and environmentally acceptable water additives. On the other hand, the design or optimization of the recycling-water process on an industrial scale demands a thorough understanding of all the fundamental parameters that govern the various operations involved. Therefore, the inhibition varying with the solution temperature, pH, and Ca2+ and Fe2+ concentration should be tested. Iron can originate from the feedwater or can develop within the system through the corrosion of pipes and metal equipment. Ferrous ion, which is soluble in an aqueous medium, is oxidized to the ferric ion. At a low pH of up to about 3-4, the ferric ion is also soluble in an aqueous medium, but at a pH of about 5 and above, it precipitates out in the form of iron hydroxide, that is, Fe(OH)3, or iron oxide, that is, Fe2O3, and other iron compounds where the iron has an oxidation state of three, hereinafter referred to as iron (III). It is known that trace amounts of iron (III) on the order of 1-5 mg/L, when present in a circulation system, can adversely affect the performance of scale-control agents such as copolymers of acrylic acid. Fouling by iron compounds such as iron oxide, iron silicates, and the like is a constant threat to the efficient operation of industrial recycling water systems.15 Therefore, excellent precipitation inhibitors are not only effective against scale but also effective in stabilize iron in solution; that is to say, they are effective precipitation inhibitors both for calcium-phosphate precipitation and for iron (III) precipitation. In the present work, we try to discover and explore the effectiveness of structurally well-defined calcium-phosphate and iron (III) inhibitors which are phosphor free and have a superior calcium tolerance. Inhibitors employed in this paper are doublehydrophilic block copolymers, which are depicted in Table 1; one is copolymer of maleic anhydride (MA)-ammonium allylpolyethoxy sulfate (APES), and the other is copolymer of maleic anhydride (MA)-allylpolyethoxy carboxylate (APEC).

10.1021/ie100395z  2010 American Chemical Society Published on Web 08/27/2010

Ind. Eng. Chem. Res., Vol. 49, No. 19, 2010

8921

Table 1. Data of the FT-IR Spectra of APEO, APEC, MA-APEC, APES,and MA-APES compounds

IR(cm-1), KBr pellet

abbreviation

Allyloxy polyethoxy ether Allylpolyethoxy carboxylate

APEO APEC

Maleic anhydride-allylpolyethoxy carboxylate Ammonium allylpolyethoxy sulfate

MA-APEC

Maleic anhydride-ammonium allylpolyethoxy sulfate

MA-APES

APES

3446(γO-H), 2875(γC-H), 1646(γCdC), 1468(δC-H), 1100(γC-O), 3446(γO-H), 2875(γC-H), 1646(γCdC), 1468(δC-H), 1723(γCdO), 1100(γC-O), 3446(γO-H), 2875(γC-H), 1468(δC-H), 1723(γCdO), 1100(γC-O), 3446(γO-H), 3225(γN-H), 2875(γC-H), 1646(γCdC), 1468(δC-H), 1349(γSdO), 1100(γC-O) 3446(γO-H), 3225(γN-H), 2875(γC-H), 1723(γCdO), 1468(δC-H), 1349(γSdO), 1100(γC-O)

Scheme 1. Synthesis of MA-APEC (Top) and MA-APES (Bottom)

MA is one hydrophilic block, and the other hydrophilic block is APES or APEC. 2. Materials and methods 2.1. Materials. APEC and APES were synthesized from allyloxy polyethoxy ether (APEO) in our laboratory according to K. Du.16,17 MA and ammonium persulfate were analytically pure grade and were supplied by Zhongdong Chemical Reagent Co. (Nanjing, Jiangsu, China). Distilled water was used for all the studies. Fourier-transform infrared (FT-IR) spectra were taken on a Bruker FT-IR analyzer (VECTOR-22, Bruker Co., Germany) by using the KBr-pellet method (compressed powder). The shape of calcium-phosphate scale was observed with a scanning electron microscope (S-3400N, HITECH, Japan). The light transmittance of ferrous solutions was measured with spectrophotometric measurements on a UV3100-PC ultraviolet and visible spectrometer (Mapada, China) at 420 nm. The formation of core-shell structure was determined with transmission electron microscope (JEM-2100SX, Japan). 2.2. Synthesis of MA-APEC and MA-APES. A 5-neck round bottom flask, equipped with a thermometer and a magnetic stirrer, was charged with 90 mL distilled water and 0.1 mol APEC and heated to 70 °C with stirring under nitrogen atmosphere. After that, 0.1 mol MA in 18 mL distilled water (the mole ratio of APEC and MA was 1:1) and the initiator solution (3.0 g ammonium persulfate in 18 mL distilled water) were added separately at constant flow rates over a period of 1.0 h. The reaction was then heated to 80 °C and maintained at this temperature for an additional 1.5 h, ultimately affording an aqueous polymer solution containing approximately 35% solid. The product was dumped and stirred in ten times volume of acetone. The insoluble product was filtered, collected, and extracted in a Soxhlet extractor for 16.0 h to remove the remaining MA and APEC. The crude product was dried in vacuum oven until constant weight to attain the desired MA-APEC as a reddish stringy liquid. Only 0.1 mol APEC was changed to 0.05 mol APES, and the rest was invariable. The product of MA-APES as a yellowish stringy liquid was

attained. The synthesis of MA-APEC and MA-APES is given in Scheme 1. 2.3. Precipitation Conditions. All inhibitors were tested under the same precipitation conditions. The inhibitor dosages given are on dry-inhibitor basis. Analytical reagent grade chemicals and grade A glassware were used. Phosphate stock solutions were prepared from potassium dihydrogen phosphate and were standardized potentiometrically by titration with potassium hydroxide. Calcium stock solutions were prepared from calcium chloride dihydrate and were standardized by atomic absorption spectroscopy. Iron(II) stock solutions were prepared from iron(II) sulfate heptahydrate and were standardized by atomic absorption spectroscopy. Supersaturated solutions of calcium phosphate for the precipitation experiment were prepared by adding a known volume of phosphate (the final PO43- concentration would be 5 mg/L) stock solution to a glass bottle (250 mL) thermostatted at constant temperature according to the national standard of P. R. China concerning the code for the design of industrial recirculating cooling-water treatment (GB 50050-95), containing a known volume of water. After temperature equilibration, the inhibitors were added before the calcium stock solution was added in such amount that the final calcium concentration would be 250 mg/L or the required values. Precipitation in these solutions was monitored after these solutions were heated 10 h at a temperature of 80 °C by analyzing aliquots of the filtered (0.22 µm) solution for phosphate concentration by using the standard colorimetric method according to the international standard ISO 6878:2004. The pH of the calcium phosphate supersaturated solution was adjusted to the required values by using dilute solutions of sodium hydroxide and/or hydrochloric acid and kept constant with borax buffer solution. Polymer efficacy as a calcium phosphate inhibitor was calculated by using the following equation: Inhibition(%) )

[phosphate]final - [phosphate]blank × 100% [phosphate]initial - [phosphate]blank

where [phosphate]final ) concentration of phosphate in the filtrate in the presence of inhibitor at 10 h, [phosphate]blank )

8922

Ind. Eng. Chem. Res., Vol. 49, No. 19, 2010

Figure 1. FT-IR spectra of APEO (a), APEC (b), MA-APEC (c), APES (d), and MA-APES (e). Table 2. Calcium-Phosphate and Iron (III) Inhibition of MA-APEC and MA-APES dosage of MA-APEC or MA-APES (mg/L)

calcium-phosphate inhibition of MA-APEC (%)

calcium-phosphate inhibition of MA-APES (%)

transmittance of ferrous solution in the presence of MA-APEC (%)

transmittance of ferrous solution in the presence of MA-APES (%)

0 2 4 6 8 10 12 14 16

0 26.61 89.94 99.27 99.13 98.87 99.32 98.87 99.29

0 16.23 84.67 90.84 89.91 89.98 91.32 90.87 90.50

100.0 100.0 97.02 22.55 23.87 23.64 24.37 23.12 22.97

100.0 99.73 99.66 99.44 100.0 97.42 29.55 30.87 30.64

concentration of phosphate in the filtrate in the absence of inhibitor at 10 h, and [phosphate]initial ) concentration of phosphate at the beginning of the experiment. Ferrous compounds for precipitation experiments were prepared by adding a known volume of calcium stock solution to a beaker (1000 mL) at room temperature under violent stirring, with a known volume of water. After temperature equilibration, the inhibitors were added before the iron(II) (normally 5-10 mL) stock solution was added in such amount that the final iron(II) concentration would be 10 mg/L or the required values. Precipitation in these solutions was monitored by analyzing solutions for the light transmittance by using UV spectrophotometer after these solutions were heated 5 h at a temperature of 50 °C. The pH 9.0 of ferrous solutions was adjusted by using dilute solutions of borax. Polymer efficacy as a iron (III) inhibitor was evaluated by using the light transmittance of ferrous solutions, which is 100% after being heated 5 h at a temperature of 50 °C in the absence of inhibitor. The lower the light transmittance is, the better the polymer efficacy is as an iron (III) inhibitor. 3. Results and Discussion 3.1. Characterization of Inhibitor. The FT-IR spectra of APEO, APEC, MA-APEC, APES, and MA-APES are exhibited in Figure 1. The data of the FT-IR spectra of APEO, APEC, MA-APEC, APES, and MA-APES are reported in Table 1. The 1723 cm-1 strong intensity absorption peak (-CdO) in curve b reveals clearly that APEC has been synthesized

successfully. The fact that the (-CdC-) stretching vibration at 1646 cm-1 appears in curve b but disappears completely in curve c reveals that free radical polymerization between APEC and MA has happened. The 1349 cm-1 strong intensity absorption peak (-SdO) in curve d clearly reveals that APES has been synthesized successfully. The fact that the (-CdC-) stretching vibration at 1646 cm-1 appears in curve d but disappears completely in curve e and the 1723 cm-1 strong intensity absorption peak (-CdO) exists in curve e clearly reveals that free-radical polymerization between APES and MA has happened. 3.2. Effect of Inhibitor Dosage. The dosage of the inhibitors has a deep effect on the formation of calcium-phosphate precipitation and iron (III) precipitation. The results of this investigation are shown in Table 2. The data of calciumphosphate inhibition in Table 2 reveal that the inhibitory value obtained for MA-APEC is about 99%, and it is about 90% for MA-APES under the same experimental conditions of 250 mg/L Ca2+, 5 mg/L PO43-, pH 9.0, 80 °C, and 6 mg/L inhibitors. That is to say, both MA-APEC and MA-APES are extremely effective in preventing the precipitation of calcium phosphate from aqueous solutions. Compared to the copolymer of MA-APES, the copolymer of MA-APEC outperforms against calcium-phosphate scale. The light transmittance of ferrous solutions in the presence of MA-APEC or MA-APES in Table 2 shows that both MA-APEC and MA-APES have excellent dispersancy activity toward iron (III), and it also indicates that MA-APEC have superior ability to stabilize iron (III) in aqueous solutions.

Ind. Eng. Chem. Res., Vol. 49, No. 19, 2010

8923

Figure 2. SEM images of calcium-phosphate crystals (250 mg/L Ca2+, 5 mg/L PO43-, PH 9.0, 80 °C), (a) in the absence of inhibitor and (b) in the presence of MA-APEC and (c) in the presence of MA-APES.

Figure 3. Schematic of the formation of core-shell structure; the core origin from PIC and the shell come from PEG.

It is apparent that the copolymer dosage strongly affects the ability of the inhibitors to control the precipitation of calcium phosphate and iron (III). For example, at 2 mg/L dosage, the polymers show poor calcium phosphate inhibition (16.23 and 26.61% for MA-APES and MA-APEC, respectively). However, at 6 mg/L, the performance of the polymers is substantially improved, and maximum inhibitory power is obtained. Similar results are also obtained from the data on the ability to stabilize iron. When the dosage is 6 mg/L, the transmittance of the ferrous solution is 22.55% in the presence of MA-APEC, and it is 99.44% in the presence of MA-APES. The data show that MA-APES is not able to stabilize iron until its dosage exceeds 12 mg/L. It should be noted that the similar tendency of the dosage on the performance behavior has been reported in earlier studies by polymeric threshold inhibitors.18,19 The presence of scale inhibitors influences not only the growth rate but also the morphology of the crystal. Figure 2 shows the SEM images of calcium-phosphate crystals grown in the absence and in the presence of 3 mg/L MA-APEC or MA-APES copolymers. In the absence of inhibitors, irregular-shaped tight particles were obtained (Figure 2a), and in the presence of MA-APEC (Figure 2b) or MA-APES (Figure 2c), calcium-phosphate aggregate particles of regular squama-shaped were produced. Figure 2b,c also indicates that both MA-APEC and MA-APES changed distinctly the calcium-phosphate crystal morphology and size, whereas only a slight difference existed in the calcium

-phosphate crystal morphology and size between MA-APEC and MA-APES. This is due to the functional groups of inhibitors in terminal moieties of the side chains containing -SO3NH4 or -COONa, and it may be explained in terms of the formation of polyion complex (PIC) micelles from anionic copolymers and calcium-phosphate crystallites.20-23 3.3. Effect of the Inhibitor Functional Groups. The inhibitor functional groups exhibit a significant impact on the inhibitory power in terms of controlling the scale precipitation.2-5,10-14 The inhibitors employed in this work belong to the doublehydrophilic block copolymers which have been applied as new water additives to effectively control the calcium-carbonate precipitation.20,21 They consist of one hydrophilic block designed to interact strongly with the appropriate inorganic minerals and another hydrophilic block that does not interact (or only weakly) with inorganic minerals and mainly promotes solubilization in water.24-27 Both MA-APEC and MA-APES have excellent inhibition for calcium phosphate or iron (III). This is illustrated in Figure 3. Positively charged calcium ions on the surface of inorganic minerals, such as calcium phosphate, iron (III), and the like, can recognize and react with the oxygen atom of the carboxyl groups24 (Figure 3a). Interactions between calcium ions or iron ions and carboxyl groups, coming from the functional groups of inhibitors MA-APEC or MA-APES, lead to the spontaneous formation of PIC micelles and water-compatible

8924

Ind. Eng. Chem. Res., Vol. 49, No. 19, 2010

Figure 4. TEM images of calcium-phosphate crystals (250 mg/L Ca2+, 5 mg/L PO43-, PH 9.0, 80 °C), (a) in the absence of inhibitor, (b) in the presence of MA-APES, and (c,d) in the presence of MA-APEC.

poly(ethylene glycol) (PEG) segments surrounding the core of PIC. The core of PIC and the shell of PEG corona form the core-shell structure (Figure 3b), where the micelle aggregation is blocked through steric and electrostatic repulsion of PEG corona. The determinant during this core-shell structure formation process is the phase separation between the PEG corona and the PIC core domain, requiring a regular array of the molecular junctions between the PIC and the PEG segments at the interface of the core. The requirement for charge stoichiometry (neutralization) in the core is another essential factor during this PIC micelle formation process.28-31 This eventually determines the ratio of participating anions and cations in the core and restricts the spatial arrangement of segments in the core. For instance, the molar ratio is 0.5 in the PIC micelles for calcium ions and -COO- which come from MA-APEC or MA-APES as a result of carboxyl deprotonation. Thus, the core is neutral, whereas the PEG corona is negatively charge because of -COO- or -SO3 in the terminal moieties of the copolymer side chains. The presence in the corona of the terminal groups -COO- or -SO3- can significantly increase the charge density and electrostatic repulsion. There is an electrostatic attraction in the core and an electrostatic repulsion or steric resistance in the corona; the PIC micelles with water-compatible PEG segments surrounding the core of PIC are formed stably and have excellent solubility in water. The observed superior performance exhibited by the highly charged copolymer for inhibiting calcium-phosphate precipitation is consistent with the results of a study about inhibitors for calcium-carbonate precipitation.32 Amjad14 also reported similar observations in seeded growth studies of the effect of carboxylic acid polymers as crystallite growth inhibitors for calcium phosphate from aqueous solutions. Figure 4 shows transmission electron microscope (TEM) images of calcium-phosphate crystals grown in the absence and in the presence of MA-APEC or MA-APES. TEM images indicate that MA-APEC or MA-APES result in the formation

of core-shell structure, and they also show that the inhibitors of MA-APEC or MA-APES highly change the morphology and size of the calcium-phosphate crystals. In the absence of inhibitor, needle-shaped particles of a size of about 200 nm were obtained (Figure 4a), and in the presence of MA-APEC or MA-APES, regular ball-shaped calcium-phosphate particles are produced. When compared with calcium phosphate crystallites of a size of 5-40 nm (Figure 4b) in the presence of 3 mg/L MA-APES, the crystallites, the size of which is about 3-25 nm, are much smaller in the presence of 3 mg/L MA-APEC (Figure 4c,d). The results of the TEM study are consistent with those of Antonia et al.,33 which reported that cationic polymers exhibit higher inhibitory performance resulting from the interactions between polycation (polymer) and polyanion (silica). The study of Achilles et al. showed that the role of polycarboxylic acids as inhibitors of calcium-phosphate crystal growth was to bind calcium ions with polycarboxylates.34 Compared to the copolymer of MA-APES containing terminal sulfate groups -SO3NH4, MA-APEC, which contains carboxyl terminal groups -COONa, exhibits superior inhibition performance, suggesting that carboxyl terminal groups in the polymer have a certain role. Perhaps carboxyl terminal groups -COONa also can weakly interact or have a small quantity of chelation ability with calcium ions or iron ions, whereas -SO3NH4 cannot play such role. 3.4. Influence of Solution Property. Solution properties have a great influence on the inhibiting precipitation. In order to optimize the parameters of the recycling water process on an industrial scale, we investigated the effect of the solution parameters on the inhibitory power of MA-APEC and MA-APES. The results are shown in Figure 5. In Figure 5a, the inhibition efficiency of the inhibitors is demonstrated under conditions of water with a much higher hardness. Both MA-APEC and MA-APES polymers provide unexceptionable inhibition, and the MA-APEC polymer has substantially greater efficiency than the MA-APES polymer.

Ind. Eng. Chem. Res., Vol. 49, No. 19, 2010

8925

Figure 5. Copolymers inhibition at a level of 6 mg/L as a function of solution Ca2+ concentration (a), temperature (b), pH (c), and Fe2+ concentration (d).

Data in Figure 5b clearly demonstrate the superior thermal stability of the MA-APEC and MA-APES polymers. When increasing the solution temperature from 80 to 95 °C, both MA-APEC and MA-APES polymers retain most of their activity, only 15 and 8% loss in activity, respectively. As illustrated in Figure 5c, increasing the solution pH from 3 to 12.5 results in 20-25% drop of the inhibitory power. The reason is probably that the solubility of calcium phosphate decreases when increasing the pH. At a pH of 8.8-9.2, the usual pH values of the industry recycling water, both the MA-APEC and MA-APES polymers show superior inhibition, whereas the MA-APEC polymer provides a little higher inhibitory power than MA-APES does, by 9%. Thus, the incorporation of the high-performance polymer MA-APEC into cycling water ensures a better overall system performance. In consideration of the favorable reaction with iron ions, some antiscalants, such as poly(acrylic acid), would lose most of their effectiveness against calcium-phosphate scale in the presence of trace amounts of iron in solution.15 The results in Figure 5d show that both MA-APEC and MA-APES still have excellent calcium-phosphate inhibition at levels of 0-6 mg/L iron ions in supersaturated solutions of calcium phosphate. At levels of 6-12 mg/L, the inhibition power of MA-APES decreases dramatically, whereas the effectiveness of MA-APEC is mostly maintained. Both MA-APEC and MA-APES are totally ineffective against calcium-phosphate scale when the concentrations of iron ions in solutions are above 15 mg/L. Usually, trace amounts of iron are in the order of 1-5 mg/L in industrial recycling water systems; hence, copolymers of MA-APEC and MA-APES are still excellent inhibitors for calcium phosphate, even in the presence of iron ions in aqueous solutions. 4. Conclusions (1) Both MA-APEC and MA-APES possess excellent calcium-phosphate inhibition, approximately 99 and 90% at a level of 6 mg/L, respectively. (2) Both MA-APEC and MA-APES have a superior ability to stabilize iron (III) in solution. The light transmittance of

ferrous solutions is about 23% in the presence of MA-APEC when the dosage is 6 mg/L, whereas in the presence of 12 mg/L MA-APES, it is about 31%. (3) Compared to MA-APES, which has two -COONa and one -SO3NH4 functional groups within a repeat unit, MA-APEC, which contains three -COONa functional groups within a repeat unit, shows a superior inhibitory efficiency which indicates that -COONa plays an important role. (4) The presence of additional groups PEG in the inhibitor molecules improves the solution capacity and results in their excellent inhibition in high-hardness water. (5) The copolymers maintain most of their activity under conditions of a solution with a pH of 3.5-12.5, a temperature of 80-95 °C, a calcium hardness of 250-2000 mg/L, and at levels of 0-6 mg/L iron ions in aqueous solutions. Literature Cited (1) Antonia, K.; Aggeliki, S.; Konstantinos, D. D. Being “green” in chemical water treatment technologies: issues, challenges and developments. Desalination 2008, 223, 487–493. (2) Choi, D.; You, S.; Kim, J. Development of an environmentally safe corrosion, scale, and microorganism inhibitor for open recirculating cooling systems. Mater. Sci. Eng. A 2002, 335, 228–236. (3) Demadis, K. D.; Katarachia, S. D.; Koutmos, M. Crystallite growth and characterization of zinc- (amino-tris-(methylenephosphonate)) organicinorganic hybrid networks and their inhibiting effect on metallic corrosion. Inorg. Chem. Commun. 2005, 8, 254–258. (4) Zieba, A. G.; Sethuraman, F. P.; Nancollas, G. H.; Cameron. D. Influence of organic phosphonates on hydroxyapatite crystallite growth kinetics. Langmuir 1996, 12, 2853–2858. (5) Demadis, K. D.; Peter, B. Chemistry of organophosphonate scale growth inhibitors: two-dimensional, layered polymeric networks in the structure of tetrasodium 2-hydroxyethyl-amino-bis(methylenephosphonate). J. Solid State Chem. 2004, 177, 768–4776. (6) Tomson, M. B.; Nancollas, G. H. Mineralization kinetics: A constant composition approach. Science 1978, 200, 1059–1060. (7) Cabeza, A.; Ouyang, X.; Sharma, C. V. K.; Aranda, M. A. G.; Bruque, S.; Clearfield, A. Complexes formed between nitrilotris(methylenephosphonic acid) and M2+ transition metals: isostructural organicinorganic hybrids. Inorg. Chem. 2002, 41, 2325–2333.

8926

Ind. Eng. Chem. Res., Vol. 49, No. 19, 2010

(8) Sarah, G. R.; Diana, T.; Hughes, W.; Shellis, R. P.; Graham, E. Effect of serum albumin on glycosaminoglycan inhibition of hydroxyapatite formation. Biomaterials 2004, 25, 971–977. (9) Amjad, Z. Constant-composition study of dicalcium phosphatedihydrate crystallite growth in the presence of poly(acrylic acids). Langmuir 1989, 5, 1222–1225. (10) Amjad, Z. Influence of polyelectrolytes on the precipitation of amorphous calcium phosphate. Colloids Surf. 1990, 48, 95–106. (11) Marina, P.; Emilia, O.; Amedeo, L.; Dino, M. Gypsum scale control by nitrilotrimethylenephosphonic acid. Ind. Eng. Chem. Res. 2009, 48, 10877–10883. (12) Daniel, B.; Samuel, I. S. Adsorption of ionizable polymers on ionic surfaces: poly(acry1ic acid). Macromolecules 1983, 16, 1143–1150. (13) Koelmans, A. A.; Vander, H. A.; Knijff, L. M. Integrated modelling of eutrophication and organic contaminant fate & effects in aquatic ecosystems. Water Res. 2001, 35, 3517–3536. (14) Amjad, Z. Constant composition study of crystallite growth of calcium fluoride. Influence of poly(carboxylic acids), polyphosphates, phosphonates, and phytate. Langmuir 1991, 7, 600–603. (15) Amjad, Z.; Lake, A.; Masler, W. F.; Hinckley, O. O. Stabilization of metal ions with terpolymers containing styrene sulfonic acid. U.S. Patent 4,885,097, 1989. (16) Du, K.; Zhou, Y. M.; Wang, Y. Y. Fluorescent-tagged no phosphate and nitrogen free calcium phosphate scale inhibitor for cooling water systems. J. Appl. Polym. Sci. 2009, 113, 1966–1974. (17) Du, K.; Zhou, Y. M.; Da, L. y. Preparation and properties of polyether scale inhibitor containing fluorescent groups. Int. J. Polymer. Mate. 2008, 57, 785–796. (18) Sharma, V. K.; Johnsson, M.; Sallis, J. D.; Nancollas, G. H. Influence of citrate and phosphocitrate on the crystallitelization of octacalcium phosphate. Langmuir 1992, 8, 676–679. (19) Pecheva, E.; Lilyana, P.; George, A. Hydroxyapatite grown on a native extracellular matrix: Initialinteractions with human fibroblasts. Langmuir 2007, 23, 9386–9392. (20) Colfen, H.; Qi, L. The mechanism of the morphogensis of CaCO3 in the presence of poly(ethylene glycol)-b-poly(methacrylic acid). Progr. Colloid Polym. Sci. 2001, 117, 200–203. (21) Yu, S. H.; Colfen, H.; Antonietti, M. Polymer-controlled morphosynthesis and mineralization of metal carbonate superstructures. J. Phys. Chem. B 2003, 107, 7396–7405. (22) Kataoka, K.; Ishihara, A.; Harada, A.; Miyazaki, H. Effect of the secondary structure of poly(L-lysine) segments on the micellization in aqueous milieu of poly(ethylene glycol)-poly(L-lysine) block copolymer partially substituted with a hydrocinnamoyl group at the N-position. Macromolecules 1998, 31, 6071–6076.

(23) Harada, A.; Kataoka, K. On-off control of enzymatic activity synchronizing with reversible formation of supramolecular assembly from enzyme and charged block copolymers. J. Am. Chem. Soc. 1999, 121, 9241– 9242. (24) Tatiana, K. B.; Alexander, V. K. Soluble complexes from poly(ethylene oxide)-block-polymethacrylate anions and N-alkylpyridinium cations. Macromolecules 1997, 30, 3519–3525. (25) Colfen, H.; Antonietti, M. Crystallite design of calcium carbonate microparticles using double-hydrophilic block copolymers. Langmuir 1998, 14, 582–589. (26) Yu, L.; Glen, S. K. Micelle-like structures of poly(ethylene oxide)block-poly(2-hydroxyethyl spartamide)-methotrexate conjugates. Colloids Surf., B 1999, 16, 217–226. (27) Harada, A.; Kataoka, K. Novel polyion complex micelles entrapping enzyme molecules in the core: preparation of narrowly-distributed micelles from lysozyme and poly(ethylene glycol)-poly(aspartic acid) block copolymer in aqueous medium. Macromolecules 1998, 31, 288–294. (28) Harada, A.; Kataoka, K. Novel polyion complex micelles entrapping enzyme molecules in the core. 2. Characterization of the micelles prepared at nonstoichiometric mixing ratios. Langmuir 1999, 15, 4208–4212. (29) Bouyer, F.; Gerardin, C.; Fajula, F. Role of double-hydrophilic block copolymers in the synthesis of lanthanum-based nanoparticles. Colloids Surf., A. 2003, 217, 179–184. (30) Harada, A.; Kataoka, K. Formation of polyion complex micelles in an aqueous milieu from a pair of oppositely-charged block copolymers with poly(ethylene glycol) segments. Macromolecules 1995, 28, 5294– 5298. (31) Jong, O. K.; Alexander, V. K.; Tatiana, K. Bronich polymer micelles with cross-linked polyanion core for delivery of a cationic drug doxorubicin. J. Controlled Release 2009, 138, 197–204. (32) Rudloff, J.; Colfen, H. Superstructures of temporarily stabilized nanocrystalline CaCO3 particles: morphological control via water surface tension variation. Langmuir 2004, 20, 991–996. (33) Antonia, K.; Aggeliki, S.; Konstantinos, D. D. Being “green” in chemical water treatment technologies: issues, challenges and developments. Desalination 2008, 223, 487–493. (34) Achilles, T.; George, H. N. The Role of polycarboxylic acids in calcium phosphate mineralization. J. Colloid Interface Sci. 2002, 250, 159– 167.

ReceiVed for reView February 25, 2010 ReVised manuscript receiVed August 16, 2010 Accepted August 16, 2010 IE100395Z