NACE-99-118

THE INFLUENCE OF RECIRCULATING WATER IMPURITIES ON THE PERFORMANCE

OF CALCIUM PHOSPHATE INHIBITING POLYMERS

Zahid Amjad, PhD Digen Butala, PhD and Jeff Pugh

Noveon, Inc. (formerly BFGoodrich Performance Materials) 9911 Brecksville Road Cleveland, Ohio 44141

ABSTRACT Many factors, including pH, temperature, make-up water quality, and heat exchanger metallurgy, influence the performance of polymeric inhibitors in treating recirculating cooling water systems. The availability of good quality make-up water and the imposition of stringent wastewater discharge regulations have forced many cooling systems to operate at increasingly higher cycles of concentration. The severity of these operating conditions often results in waters that have higher scale formation potential. Presented here is information regarding the influence of impurities, such as suspended matter and metal ions, on the performance of polymeric inhibitors used in phosphate-based treatment programs. Keywords: calcium phosphate, cooling water, polymers, scale, metal ions

INTRODUCTION Historically, water is one of the most common heat transfer fluids used in industrial processes. The unique combination of high thermal conductivity, heat capacity, and large useable temperature range make water ideally suited as an heat transfer fluid for industrial processes. Governmental regulations and economic considerations often dictate that cooling tower operators increase the cycles of concentration of their cooling water. When this happens, the ionic constituency of the cooling water may increase dramatically and the solubility of certain scale forming salts may be exceeded. As supersaturation is achieved, thermodynamics dictates that precipitates will form. Deposit control polymers (DCPs)

including poly(acrylic acid) and acrylate-based co- and terpolymers are often used in water treatmentapplications to reduce the formation of these scales. These DCPS affect the scale formation kinetics by

extending the precipitation induction time beyond the holding time of the tower”2 which is a propertyknown as threshold inhibition. These DCPS have also been shown to modi~ the crystal structures suchthat the precipitates formed are less adherent and to disperse particles that would otherwise agglomerate.

Phosphates and phosphonates are essential components of stabilized-phosphate and all-organic coolingwater treatment (C WT) programs. However, the performance of multifunctional DCPS is the key to theefficacy of these CWT programs. These high performance DCPS control the thickness of the calcium-phosphate film on metal surfaces and prevent precipitation of the calcium-phosphate and calcium-phosphonate salts in the recirculating water.2’3’4Various polymers are used in these CWT programs tominimize scale formation and for deposit control. The performance of polymers used in recirculatingcooling water has been shown to depend on the quality of the water in the system.

Factors governing the performance of polymers can be divided into two distinct categories: (1) those thataffect the volubility of the scale-forming salts and (2) those that affect the action of the polymer.Solution pH affects the deprotonization of polymers, the affinity of polymers towards ionic species, andthe adsorption of polymers onto growing crystal surfaces. Solution ionic strength also affects polymerperformance.5 Additionally, all open cooling towers using natural waters contain certain level of

contaminants such as transition metal ions and particulate matter can affect deposit control polymerperformance. Transition metal ions are known to significantly effect the performance of thesepolymers. “4’6-8This is a particular concern because metallic materials are typically the materials ofchoice for cooling tower piping and heat transfer surfaces. All open cooling towers using natural waterscontain particulate contaminants (e.g., clay) which adsorb DCPS and thereby reduce the availability ofDCPS for the other desired functions.

Traditionally, CWT program applications consider the adverse impact of iron. However because ofincreasingly stringent CWT program operating conditions, it is important to consider the effect of othermetal ions (i.e., copper, manganese, zinc) and contaminants (i.e., clay, cationic polymers). These metalions effect the morphology and kinetics of calcium carbonate, calcium sulfate, and calcium phosphatescale formation. g-” In a previous publication,6 the effect of a cationic polymer on calcium phosphateinhibition by DCPS was presented. This paper specifically addresses the effect of water contaminants(e.g., metal ions, clay) on calcium phosphate inhibition by DCPS. Quantification of effect of these onDCPS will help facilitate the optimization of CWT programs.

EXPERIMENTAL

The experiments described in this paper were designed to correlate to field situations and to reflectconditions of actual operating systems but to maintain the experimental control of a laboratory study.This investigation examines the influences of common contaminants (e.g., particulate silt and clay, metalions) on calcium phosphate inhibiting polymers. The DCPS used in this study have shown to be effectivein retarding calcium phosphate precipitation.

The chemicals used to makeup the solutions were Fisher Scientific ACS reagent grade and the DCPSwere commercial products. Class A glassware was used for all experiments. Polymer concentrations aregiven on an active polymer basis. Stock solutions of known concentrations of calcium chloride, sodiumphosphate, hydrochloric acid, sodium hydroxide, and various polymers were prepared and used to

makeup test solutions. The dilution water used was double deionized and distilled. A Metrohrn-Brinkrnann pH-stat unit equipped with a combination electrode was used to maintain the experimentalsolution pH. The pH electrode was calibrated before every experiment with standard buffers. The testsolution temperature was maintained to *1 ‘C by passing controlled water through the outer jacket of thejacketed reaction vessel.

The test solution was made by the slow addition of the phosphate stock solution with stirring to thedesired water. The polymer and other ionic constituents were added and the solution pH was adjusted, ifnecessary, after a 30-minute equilibration period. The calcium stock solution was added, making up thetotal volume to 600 mL. For all the experiments the reaction period was fixed at 22 hr. During eachexperiment, the test solution pH was maintained (within +0.01 pH units) at the desired level using thepH-stat unit. Unless specified, the standard test conditions for the calcium phosphate threshold inhibition

were 140 ppm [Ca], 9 ppm [POd], pH 8.5, 50 ‘C, and 22 hr.

The reaction progression was determined by spectrophotometric analysis of filtered (0.45 micron)aliquot of the test solution for the phosphate ion. The efficacy of the polymer was calculated as percentinhibition as given in equation 1.

TI =

where:

TI

D’041,=0

[p04]x,&22

[p04]0,t=22

[P04]X,,=22- [p04]0,t=22

x 100’%0

[po41t=o - [p04]0,t=22

(1)

—— Threshold inhibition, YO

. Phosphate ion concentration at the beginning of the experiment= Phosphate ion concentration in the test solution after 22 hr—— Phosphate ion concentration in the control

RESULTS AND DISCUSSION

Environmental regulations are the key driver for the increase use

experiment after 22 hr

of all-organic (phosphate and

phosphonate based) CWT programs. High performance DCPS are used in all organic CWT programs toinhibit/disperse phosphate and phosphonate based scales.2-4 The DCP concentrations required to inhibit

the formation and precipitation of calcium phosphate is highly dependent on solution saturation, theprecipitating salt form, the system residence time, the water impurities, and the inhibiting polymercharacteristics. The solution saturation is a function of temperature, pH, ionic concentrations, andpressures. The water impurities could be metal ions or suspended solids. DCP characteristics such as,functional groups, molecular weight, and structural modifications affect the ability of DCPS toinhibiting/dispersing calcium phosphate.

As described in the Experimental section, several experiments were conducted with different DCPS inthe presence of different water impurities. The focus of the experimental work herein is the

differentiation of the performance of acrylate co- and terpolymers. However, occasionally includedherein are data for the performance of other polymers. The DCPS used in these tests were commerciallyavailable acrylate homo-, co-, and terpolymers. Table 1lists the DCPS evaluated in this study.

Effect of Polymer Dosage at Standard ConditionsThe ability of polymer to inhibit calcium phosphate formation is very important aspect of phosphate and

phosphonate-based water treatment programs. Figure 1 shows threshold inhibition as fi.mction ofpolymer dosage for polymer A, polymer B, and polymer C. A 10 ppm dosage of polymer A is requiredto inhibit (290°A TI) the formation of calcium phosphate whereas only 7.5 ppm of polymer B is requiredto achieve the same performance. However, even at a 15 ppm dosage, the calcium phosphate inhibitionfor polymer C (polyacrylic acid) is only 10%. Comparison of the three performance curves in Figure 1clearly shows the superior calcium phosphate inhibition of polymer B (terpolymer) as a function ofdosage. The incorporation of co-monomers containing sulfonic acid groups improves the inhibiting

power of the DCPS.

The balance of this paper makes frequent references to the threshold inhibition curves for polymer A and

polymer B in Figure 1 for comparison with the performance of polymers A and B in presence of thevarious water impurities. These comparisons illustrate the effect of water impurities on calciumphosphate inhibition of polymers.

Effect of Metal Ions on Calcium Phosphate InhibitionMetal ions present in cooling water systems may be contributed by corrosion by-products, treatmentprogram components, and water impurities. Metal ions significantly effect the calcium phosphateinhibition performance of polymers. 1’4’G-8Therefore, it is important to quantify the effect of differentmetal ions such as iron, copper, manganese, and zinc on the performance of polymers used in thecooling water treatment programs.

Effect of Iron (111). Soluble iron, the ferrous ion, is often encountered in natural water systems eitherfrom the water itself at low concentrations (usually less than 3 ppm) or as a result of corrosion of theiron piping, well heads, or other vessels in the system. On oxidation, the ferric ion may “tie up” ordeactivate DCPS. Co- and terpolymers are touted as having excellent tolerance to iron (III). It isimportant to evaluate the efficacy of polymers to inhibit calcium phosphate in presence of iron. Severalearlier studies have addressed the effect of iron on efficacy of different polymers.G’8 For this study, iron(III) ranging from Oto 3 ppm was introduced to the test solution as a ferric chloride solution followingtemperature stabilization but prior to pH adjustment and before the introduction of the calcium solution.

Figure 2 shows the effect of iron (III) on the performance of polymer A for calcium phosphate inhibitionas a function of polymer dosage. The effect of iron (III) on calcium phosphate inhibition of polymer B isillustrated in Figure 3. Comparing the threshold inhibition vs. dosages for polymers A and B in Figure 1with Figures 2 and 3 shows that the presence of 3 ppm of iron (III) necessitates higher polymer dosagesto achieve the same performance. Acrylate polymers form a complex with the iron ion (are tied up byiron) unlike the momentary association of the polymer with the scale forming species. The polymerdemand by the “metal ion complexation” is in addition to the amount required for threshold inhibition.In the presence of the iron, 15 ppm polymer A and more than 10 ppm of polymer B are needed tosuccessfully inhibit the calcium phosphate precipitation. It is important to note that typically 33°/0 morepolymer B and 50% more polymer A were required to inhibit calcium phosphate in the presence of 3ppm iron (III). The results clearly show that polymer B is more tolerant of iron (III). Similar results havebeen previously reportedb for calcium phosphate inhibition of polymer A and polymer B in presence ofiron (III) under highly stressed test conditions.

Figure 4 shows a comparison of the iron tolerance of several other DCPS used in CWT applications.

These tests were run under the same conditions as those previously described and with 10 ppm of each

polymer. The calcium phosphate inhibition of polymer A and polymer E in presence of 2.5 ppm iron isreduced to below 20°/0. Where as only slight reductions in calcium phosphate inhibition of polymer Band polymer D were observed in the presence of 2.5 ppm iron. These results clearly show thatterpolymers demonstrate a greater tolerance for the iron (III) ion.

Effect of Manwmese. Manganese is occasionally an impurity of water sources. The presence ofmanganese in cooling water can lead to deposition and associated corrosion problems. Polymers areused in many cooling water treatment programs to control manganese deposition. It is believed thatpolymers solubilize manganese ion and disperse manganese oxide/hydroxide particles.10’12The resultspresented here quanti~ the effect of manganese on calcium phosphate inhibition of various polymers.Manganese was introduced to the test solution after temperature stabilization but before pH adjustmentand the addition of the calcium solution. For all cases the manganese concentration was 5 ppm.

The effect of manganese on calcium phosphate inhibition of polymer A and polymer B is shown inFigures 5 and 6, respectively. Comparison of the threshold inhibition curves for both the polymersindicates almost similar slopes in presence and absence of manganese. This observation leads to believethat a stoichiometrically proportional amount of polymer is required to complex with the manganesebefore free polymer can interact with the calcium to inhibit the scale formation. In both cases, polymerdosages must be increased by 20% or more to achieve >90% calcium phosphate inhibition in presence of5 ppm manganese ion.

Calcium phosphate inhibitions of different polymers in the presence of 5 ppm manganese ion are shownin Figure 7. These tests were run using the standard conditions (previously described) and 10 ppmdosages of each DCP. The results clearly indicate that the performance of polymer A and polymer E isdramatically reduced even in presence of 5 ppm manganese ion. The performance of terpolymers(polymers B and D), is only slightly affected by the presence of 5 ppm manganese. These results againshow the superior efficacy of terpolymers in stabilizing metal ions.

Effect of Zinc. Zinc salts are often added to CWT programs for corrosion control. Zinc ion can alsobe introduced to circulating water by the corrosion of galvanized cooling towers. As with other metalions, it is important to quanti~ and understand the effect of zinc on calcium phosphate inhibition ofpolymers.lq Zinc was introduced to the test solution at 5 ppm concentrations after temperature

stabilization but before pH adjustment and the introduction of the calcium solution.

The effect of zinc on calcium phosphate inhibition of polymer A and polymer B is depicted in Figures 8and 9, respectively. In both cases, zinc by itself does not provide any significant calcium phosphateinhibition (<1 0°/0TI). However, both Figures 8 and 9 indicate that the presence of zinc greatly enhancesthe calcium phosphate inhibition of polymers A and B. The threshold inhibition curves are shiftedtowards reduced polymer dosages in presence of 5 ppm zinc. In case of polymer A, dosage reduction ofmore than 3 ppm is observed, whereas in case of polymer B, dosage reduction of almost 2 ppm isobserved to achieve >90’?40TI. From these results it appears that copolymer, polymer A, containinghigher amount of carboxylic groups provides more synergy than the terpolymer, polymer B. Additionaltesting in our laboratory with the polymers containing different levels of carboxylic groups supports thisobservation. The synergistic effect of zinc on calcium phosphate inhibition of DCPS is very clear inthese tests and agrees with results of the calcium phosphate crystal growth inhibition characteristic of

zinc as reported in the literature. 14A similar effect of zinc on calcium carbonate crystal growth inhibitionhas also been reported in the literature.9

Effect of Copper. A low level of copper is a common impurity in cooling water systems. Normally,copper is picked up by the cooling water from copper tubing or as a corrosion product from coppercontaining metals such as brass. Copper salts may also be used as an algaecide in open cooling basins.Copper ions may tie up polymers similar to iron, thereby reducing the effectiveness of the program. Inthese experiments, quantifying the effect of copper on acrylate polymers was determined by addingcopper as a copper nitrate solution to the test solution and measuring calcium phosphate inhibition asnoted above.

The calcium phosphate inhibition of polymer A and polymer B in presence of 5 ppm copper are given inFigure 10 and Figure 11, respectively. The effect of copper on the performance of DCP as calciumphosphate inhibition is not as detrimental as that of iron (III). However, higher polymer dosages arerequired to achieve 290°/0 TI in the presence of 5 ppm copper such that the threshold calcium phosphateinhibition curves are shifted to the right. Almost 3 ppm (30°/0)more polymer A is required where as only1.5 ppm (20?40)more polymer B is required. Terpolymers appear to be much more efficient in stabilizingthe copper ions than the copolymers.

Figure 12 compares the calcium phosphate inhibition of polymers A, B, and E without metal ion, inpresence of 5 ppm zinc, and in presence of 5 ppm copper, The data show the results for 10 ppm dosagesof polymers A and E in comparison with 7.5 ppm dosages of polymer B. All three polymers performwell in absence of metal ions and in presence of 5 ppm zinc. However, it is important to note that 2.5ppm (25%) less polymer B is required to achieve the same performance.

In the presence of 5 ppm copper ion, 10 ppm of polymer A performs poorly whereas very goodperformance was obtained using 10 of ppm polymer E or 7.5 ppm of polymer B. It is noteworthy thatpolymer B at a 25% lower dosage performs better than polymer E.

Effect of Suspended Solids on Calcium Phosphate InhibitionPolymers are known to adsorb onto particles that may be present in the water. The adsorption of thepolymers onto particles and the resultant interaction between particles is the mechanism of dispersion.However when a polymer is tied up dispersing particles, it is not as available to inhibit the formation ofscale forming salts. In addition, suspended solids could act as nuclei for the formation of calciumphosphate. The magnitude of this effect was tested with Dixie Clay.

Effect of Clay Particles. Dixie clay is a kaolin clay (aluminum silicate hydrate) that has a largesurface area (27 m2/g BET surface area - Micromeritics ASAP 2400). Because of its high surface area, itis reasoned to be more detrimental to the polymer inhibition and was therefore used as a modelsuspended particle. Experiments were run at the standard conditions with varying concentrations of theclay to determine the loss of polymer efficacy. The correct quantity of clay (to give 50 to 250 mg/L clayin the final solution) was added before the calcium chloride solution addition initiates the experiment.This range of particulate concentrations covers more than is usually seen in an operating cooling tower.This range will allow us to model the effect of the clay on the polymer.

Figure 13 shows the results with and without Dixie Clay and either 10 ppm polymer A or 7.5 ppmpolymer B. The presence of 50 mg/L clay slightly reduces the efficacy of polymer A but has no effect on

performance of polymer B. Increasing the particulate concentration to 100 mg/L affects the performanceof both polymers. Increasing to 250 mg/L clay significantly impacts the calcium phosphate thresholdinhibition of both polymers.

Figure 14 illustrates the calcium phosphate inhibition of polymer A (1Oppm), polymer B (7.5 ppm), and

polymer E (1O ppm) in presence of 100 mg/L clay. Polymer A and polymer E at 10 ppm dosage levelprovide almost same (=65VO) calcium phosphate inhibition in presence of 100 mg/L. However,

polymer B, even at a 25’% lower dosage (7.5 ppm), provides excellent (85Yo) calcium phosphateinhibition in presence of 100 mg/L).

Figure 15 show the results for polymers A and B which were previously reportedl’ for a highly stressedsystem. In this case, the calcium, phosphate, and polymer concentrations were increased. The resultsparallel those in Figure 13 wherein polymer B at a lower dosage outperforms polymer A.

SUMMARY

Cooling waters contain a number of contaminants that may be antagonistic to acrylate polymers used inthe water treatment programs. By understanding the effect of these contaminants on the polymerperformance, the CWT program technologists can compensate for the effects of these contaminants. Theexperiments described in this paper suggest several conclusions noted below. Further study is inprogress and will be presented in the future .

1.

2.

3.

4.

5.

1.

The presence of iron (III) in cooling water is detrimental to the calcium phosphate inhibition ofacrylate polymers. Copolymers containing sulfonic acid have a certain tolerance to and can stabilizethe iron (III) ion. The amount of additional polymer that will be required depends on how well thepolymer can stabilize the iron.

Manganese ion and copper ion are antagonistic to the performance of acrylate-based DCPS but theadverse impact is not as great as with iron. Increasing polymer dosages can compensate for thepresence of manganese ion and/or copper and result in acceptable performance (>90’XOTI).

The zinc ion exhibits a synergy with the polymer allowing enhanced calcium phosphate inhibition atlower polymer dosage than would be expected to be necessary.

Suspended particles adversely impact the performance of polymers because of the adsorption ofpolymers on particulate matter thereby reducing the available polymer for threshold inhibition.Terpolymers seem very resilient to the presence of clay in water.

Overall, terpolymers appear to have better performance due to their superior tolerance of metal ionsand excellent calcium phosphate inhibition properties.

REFERENCES

R. W. Zuhl, Z. Amjad, The Role of Polymers in Water Treatment Application and Criteria forComparing Alternatives, Association of Water Technologies 1993, Sixth Annual Convention,Las Vegas, NV, Nov-1993.

2. J.E. Hoots, G.A. Crucil, Role of Polymers in the Mechanisms and Performance of Alkaline Cooling

Water Programs, CORROSION/86, Paper No. 13 (Houston, TX, NACE International, 1986).

3. W.F. Masler, Z. Amjad, Advances in the Control of Calcium Phosphonate with Novel PolymericInhibitors, CORROSION/88, Paper No. 11 (Houston, TX, NACE International, 1988).

4. R.W. Zuhl, Z. Amjad, W.F. Masler, A Novel Polymeric Material for Use in Minimizing Calcium

Phosphate Fouling in Industrial Cooling Water Systems, Paper No. TP 87-7, Cooling TowerInstitute, Houston, TX.

5. Z. Amjad, Seeded Growth of Calcium Containing Scale Forming Mineral in the Presence ofAdditives, CORROSION/88, Paper No. 421 (Houston, TX, NACE International, 1988).

6. Z. Amjad, J. Pugh, J.F. Zibrida, R.W. Zuhl, Polymer Performance in Cooling Water: The Influenceof Process Variables, CORROSION/96, Paper No. 160 (Houston, TX, NACE International,1996).

7. A. Marshall, B. Greeves, The Effect of Water Quality on the Performance of Extended PhosphateTechnology, CORROSION/86, Paper No. 399 (Houston, TX, NACE International, 1986).

8. L. Dubin, K,E. Fulks, The Role of Water Chemistry on Iron Dispersion Performance,CORROSION/84, Paper No. 118 (Houston, TX, NACE International, 1984).

9. P. Coetzee, M. Yacoby, S. Howell, S. Mubenga, Scale Reduction and Scale Modification EffectsInduced by Zn and Other Metal Species in Physical Water Treatment, Water SA, Vol. 24, No. 1,p. 77, 1998.

10. B. Pernot, M. Euvrard, P. Simon, Effects of Iron and Manganese on the Scaling Potentiality ofWater, J Water SRT-Aqua, Vol. 47, No. 1, p. 21-29, 1998.

11. T.J. Young, The Proper use of Modem Polymer Technology in Cooling Water Programs,Association of Water Technologies 1990, Third Annual Convention, Lake Buena Vista, FL,Nov-1 990.

12. K. Fivizzani, L. Dubin, B. Fair, J.E. Hoots, Manganese Stabilization by Polymers for Cooling WaterSystems, CORROSION/89, Paper No. 433 (Houston, TX, NACE International, 1989).

13. H. Ohtaka, T. Kawamura, Y. Furukawa, Zinc and Phosphate Scale Inhibition by a Newly DevelopedPolymer, CORROSION/89, Paper No. 432 (Houston, TX, NACE International, 1989).

14. P. Koutsoukos, Influence of Metal Ions on the Crystal Growth of Calcium Phosphates, CalciumPhosphates in Biological and Industrial Systems, Edited by Z. Amjad, Kluwer AcademicPublishers, p. 145, 1998.

15. J.F. Zibrida, R. Thorgeson, E. Mistretta, Factors Influencing Cooling Water Polymer Selection,Water Soluble Polymers: Solution Properties and Applications Symposium, American ChemicalSociety National Meeting, Las Vegas, NV, 7 to 1l-Sep-1997.

TABLE 1Deposit Control Polymers Evaluated

Polymer Composition

A Acrylic acid : Sulfonic acid copolymer’

B Acrylic acid : Sulfonic acid : Sulfonated styrene terpolymerb

c Acrylic acid homopolymerc

D Acrylic acid : Sulfonic acid : Non-ionicd

E Acrylic acid: Sulfonated styrene copolymer’

a: K-775AcrylateCopolymerb: K-798AcrylateTerpolymerc: K-752Polyacrylated: CompetitiveTerpolymere: CompetitiveCopolymer

FIGURE 1.

+ PolymerA■ PolymerB

● PolymerC

o 2 4 6 6 10 12 14 16

Polymer Dosage (ppm)[Ca] = 140 ppm, [POJ = 9 ppm

PH = 8.5, T= 50 ‘C, t =22 houre

Effect of polymer dosage on calcium phosphate inhibition.

100%. -

90% -r- +~

/ 3 ppm imn

E 30%--1-

20?’0 - -

10% - -

o% ~

O 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15[Ca] = 140 ppm, [PO~ = 9 ppm

@=8.5, T=50”C, t=22hoursPolymer A Dosage

FIGURE 2. Calcium phosphate inhibition of copolymer in the presence of the iron (III) ion.

FIGURE 3. Calcium phosphate inhibition of terpolymer in the presence of the iron (III) ion.

0

1020

304050

6070

8090

100

Polymer A Polymer B Polymer D Polymer E

Th

resh

old

Inh

ibit

ion

(%

)

0 ppm Fe 1 ppm Fe2.5 ppm Fe

[Ca] = 140 ppm, [PO4] = 9 ppm

pH = 8.5, T = 50 oC, t = 22 hours10 ppm Polymer

FIGURE 4. Calcium phosphate inhibition of different polymers in the presence of the iron (III) ion.

100% ~.

s 30% --1-

20% - -

10=%--

o% -

3456769 101112131415[Ca]=140 p~m, [POj = 9 p~m

DH= 8.5, T =50 “C, t =22 houcs Polymer A Dosage

FIGURE 5. Calcium phosphate inhibition of copolymer in the presence of the manganese ion.

100”/6

90%

80% - -6

/5 ppm manganesa

20%

1o% --

o%

o 1 2 3 4 5 6 7 8 9 10

[Ca] = 140 ppm, [PO,]= 9 ppm Polymer B Dosage@l=8.5, T = 50 “C, t =22 hours

FIGURE 6. Calcium phosphate inhibition of terpolymer in the presence of the manganese ion.

.4 nnIUu

90

80

70

60

50

40

30

20

10

0 -1-

Polymer A Polymer B Polymer D

❑Oppm M

❑5ppmlvh

Polymer E

[Ca] = 140 ppm, [PO,]= 9 ppm

pH = 8.5, T = 50 “C, t = 22 hours10 ppm Polymer

FIGURE 7. Calcium phosphate inhibition of different polymers in the presence of the manganeseion.

100%

90% -

80% - 5 ppm zinc ~

0123456 769101 II2I3 1415

[Ca] = 140 ppm, [PO,]= 9 ppm Polymer A Dosage

PI-I=8.5, T = 50 “C, t = 22 houra

FIGURE 8. Calcium phosphate inhibition of copolymer in the presence of the zinc ion.

i 00%

90%

80%

* 70%Lc

g 60%m.-S= 50%

=

o 40%c0alk 30%+

20%

1o%

07’0

5 ppm zinc

o 1 2 3 4 5 6 7 6 Q In[Ca] = 140 ppm, [PO.]= 9 ppm

.“

pH = 8.5, T=50”C, t = 22 houre Polymer B Dosage

FIGURE 9. Calcium phosphate inhibition of terpolymer in the presence of the zinc ion.

100%

9070

8070

%& 70%

co

~ 60%n.-== 50%

~

~ 40%LoalE 30%1-

20%

0% t !

0123456 78910111213 1415

[Ca] = 140 ppm, [PO,]= 9 ppm Polymer A DosagepH=8.5, T=50°C, t=22hourS

FIGURE 10. Calcium phosphate inhibition of copolymer in the presence of the copper ion.

100%

90%

80%

7& 70% - - 5 ppm copper

5:= 60?4 --n.-.c= 50% --

~

~ 40% ‘-walk 30=7’0--1-

20% --

10% --

0 1 2 3 4 5 6 7 8 9 10[Ca]=140 ppm, [P04] = 9 ppm

PH = 8.5, T = 50”C, t = 22 hoursPolymer B Dosage

FIGURE 11. Calcium phosphate inhibition of terpolymer in the presence of the copper ion.

100?40~--

90?40+

80%

70%

60% t

1

50?40

40?J0

30%

20%

1O?AO

0%

O ppm Metal 5 ppm Zn

[Ca] = 140 ppm, [PO~ = 9 ppm

PH = 8.5, T= 50°C, t = 22 houra

5 ppm Cu

❑ 10 ppm Polymer A

■ 7.5 ppm Polymer B

❑ 10 ppm Polymer E

FIGURE 12. Calcium phosphate inhibition of co- and terpolymers in the presence of copper andzinc ion.

—

190

80

70

60 .-

50

40

30

20-

10-

0-

No Clay 50 mg/1Clay

+

100 mg/1Clay 250 mg/1 Clay

[Ca] = 140 mg/1, [POd] = 9 mg/i ❑ 10 ppmPolymer A

pH = 8.5, T= 50”C, t = 22 hours ■7.5 ppm Polymer B

FIGURE 13. Calcium phosphate inhibition of co- and terpolymer in the presenceconcentrations of Dixie Clay.

100% ~

190%

80%

70?40

60%

50%

40!40

30%

20% --

1o%

o%

No Clay

[Ca] = 140 ppm, [POJ = 9 ppm

pH = 8.5, T= 50 “C, t = 22 hours

4100 ppm Clay

❑ 10 ppm Polymer A

■ 7.5 ppm Polymer B

❑ 10 ppm Polymer E

of varying

FIGURE 14. Calcium phosphate inhibition of co- and terpolymers in the presence of 100 ppm ofDixie Clay.

100 I

g 90

; 800.- 70.-Q.-

*I

60sg 50

g 40-

z 30--mg 20-

.s 10..+

o.

100 mg/1Clay

[Ca] = 240 mg/1,

No Clay 50 mg/i Clay

[PO,] = 15 mg/1

250 mg/1Clay

❑ 25 ppm Polymer A

pH = 9.0, T = 50 ‘C, t = 22 hours ❑ 17.5 ppm Polymer B

FIGURE 15. Calcium phosphate inhibition of co- and terpolymer in the presenceconcentrations of Dixie Clay under highly stressed conditions.

of varying