morphology and phases composition analysis of mixed calcium carbonate and calcium … ·...

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International Journal of Mechanical Engineering and Technology (IJMET) Volume 9, Issue 10, October 2018, pp. 1555–1568, Article ID: IJMET_09_10_159 Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=9&IType=10 ISSN Print: 0976-6340 and ISSN Online: 0976-6359

© IAEME Publication Scopus Indexed

MORPHOLOGY AND PHASES COMPOSITION

ANALYSIS OF MIXED CALCIUM CARBONATE

AND CALCIUM SULPHATE PRECIPITATES IN

FLOWING WATER OF VIBRATED PIPE

W. Mangestiyono*

Department of Industrial Technology, School of Vocation, Diponegoro University, Semarang 50275, Indonesia

S. Muryanto

Department of Chemical Engineering, UNTAG University in Semarang Semarang 50233, Indonesia

J. Jamari and A.P. Bayuseno

Department of Mechanical Engineering, Diponegoro University Semarang 50275, Indonesia

ABSTRACT

The current research was conducted to investigate morphology and phases of

CaCO3/CaSO4 mixed scale in pipes under the influence various fraction of carbonate-

sulphate anions and vibration frequencies. The vibration was simulated mechanically and

powered by an electrical motor which was controlled by computer program.

CaCO3/CaSO4 scale was synthesized by CaCl2; Na2CO3 and Na2SO4 powder. After

running in four hours and temperature in 350C, scale deposited of unvibrated experiment

found as 2.4379; 2.5739; 2.7678; 3.0175; 3.3611 gram for 0.00-1.00; 0.25-0.75; 0.50-

0.50; 075-0.25; 1.00-0.00 wt% of carbonate-sulphate anion fractions. When vibration

was implemented in 6.00 Hz scale deposited increased to be 3.5635; 3.7283; 3.9923;

4.3469; 4.8205 gram for 0.00-1.00; 0.25-0.75; 0.50-0.50; 075-0.25; 1.00-0.00 wt% of

carbonate-sulphate anion fractions. Various anion fractions that implemented in these

experiments resulted new habit vaterite in needle-hexagonal form.

Keywords : CaCO3/CaSO4; mixed scale; carbonate; sulphate; vibration

Cite this Article W. Mangestiyono, S. Muryanto, J. Jamari and A.P. Bayuseno, Morphology and Phases Composition Analysis of Mixed Calcium Carbonate and Calcium Sulphate Precipitates in Flowing Water of Vibrated Pipe, International Journal of Mechanical Engineering and Technology, 9(10), 2018, pp. 1555–1568. http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=9&IType=10

W. Mangestiyono, S. Muryanto, J. Jamari and A.P. Bayuseno


1. INTRODUCTION

Scaling of calcium carbonates and sulphates on the wall of pipes leads to potentially blockages piping system [1], decreasing in overall heat transfer coefficient [2,3] and increasing cost of maintenance [4-7]. These mixed scale formations may be contributed by dissolving the mineral based salts in the water, because of (i) these salts exist in most of all feed industrial water [8] and (ii) the increases in temperature make their solubility decreases [7]. Correspondingly, these salts would be precipitated on the wall of pipes in contact with the water supersaturated [9]. On the other hand, the crystallization of mixed scaling is very complex phenomena found at the phase interfaces where the undesired minerals are deposited [2, 4]. Therefore, understanding of the crystallization mechanism of mixed scale is necessary on the developing program of its preventive maintenance. For a scaling mitigation approach on the surface pipe with a laminar flow water, the prediction data of the scaling tendency of feed water, of which modification and optimization the process, could be obtained accordingly through experimental laboratory works.

Crystallization of mixed calcium carbonate and calcium sulfates has been studied previously [4; 10]. In this way, thermodynamic and kinetic of those minerals precipitated in water at various temperatures was investigated [4,10]. It was shown that the presence of calcium sulfate in water made the reduction in the crystallization of calcium carbonates. However, the interactive effect of co-precipitating salts with or without common ions are not yet considered including solubility effects, rate data, crystal structure and strength, inhibitor effects and also dynamic impacts. Furthermore, the mixed CaCO3/CaSO4 formation has different crystallization mechanism, which could not be based on the single precipitant, especially on thermodynamic and kinetics of each compound. Co-precipitants joining together on the surface of heat transfer could be related to the strength and tenacity of calcium carbonate and sulfate layer [9]. Here the crystal purity of deposit is an important issue to be investigated due to the existence of various impurities might affect the scale strength and tenacity. In this case, the calcium carbonate is considered as bonding cement when it co-precipitates with calcium sulfate leading to the improved strength of calcium sulfate scale deposit. While calcium carbonate was reported previously for the main constituent of aggressive scale. Addressed to such reasons, investigation of the crystal deposits should be emphasized

on phase composition and morphological analysis.

In general, the main performance limitation in the stream of water flowing is mineral deposits existing on the wall surface of pipes. The scaling deposits result from the accumulation of sparingly soluble inorganic compounds which are controlled by the thermodynamic and hydrodynamics of the flowing water. These conditions could be changed through the operating condition assisted by vibration [2]. In this way, the mechanical vibration contributes large hydrodynamic force to the piping system that might function as promoter and affects scaling process. In the industries, vibration occuring in the piping system could be generated by internal and external factors [12]. Fluctuation of fluid velocity in the inner pipe potentially produces vibration as fluid-induced vibration [13]. This such vibration is categorized as an internal factor [12]. Vibration is also caused by the operation many mechanical pieces of equipment such as turbine; mixer; extruder; diesel engine; compressor [14]. The vibration propagates into the floor and wall of the industrial building where the pipes are mounted [15, 16]. This such vibration is categorized as an external factor [12]. These internal and either external factors might simultaneously vibrate the pipe and could influence on the scaling process that takes place on the inner surface.

It has been demonstrated previously that hydrodynamic force generated by Rotating Cylinder Electrode (RCE) resulted larger scale deposited [2]. In the research, RCE was functioned as a mechanical stirrer of which the rotation speed would contributed to some forces which helpfull for mixing. However, there is no report on the influence of reciprocally vibrated pipe on the

Morphology and Phases Composition Analysis of Mixed Calcium Carbonate and Calcium Sulphate Precipitates in Flowing Water of Vibrated Pipe


formation of mixed scale. For the time being, the influence of vibration in piping system on calcium mixed scale formation has been not examined. Therefore, this study was performed on vibration making the pipe vibrated in reciprocally and contributed hydrodynamic force to the solution. This research would gain insight the phenomenon of the influence of various anion fractions and vibration frequencies on CaCO3/CaSO4 mixed scale formation in piping system. Here, two calcium salt was synthesized by reacting two anions molecule i.e. carbonate and sulphate anions. The chemical composition of the solution was set-up as their stoichiometry. In addition, to imitate the real condition in industries that the impurities exist not only in a certain composition, those two anions molecule were set in various fractions. The fractions will be discussed else where. The difference of anion fraction was suspected affect scale formation such as crystal morphology and phases as they have strong difference in solubility. It has been known that carbonate anion is insoluble on the water otherwise sulfate ion is highly soluble and affects solubility in 0.01 and 2.1 kg/m3 for CaCO3 and CaSO4 respectively [11]. This contrast property might give birth any discrepancies on crystals morphology and phases formed on the surface of pipes

2. MATERIALS AND EXPERIMENTAL PROCEDURE

2.1. Design of experiment

Aimed to imitate the vibration implementation in closer to the reality, vibration parameter was defined after simple observation conducted in severe industries. Vibrometer Lutron VT-8204 was used to measure vibration parameter throughout the pipe. After measured in ten position, mean score of vibration frequencies was found 6.00 Hz; displacement 0.004 m and acceleration in 2m.sec-2 RMS. The parameter was then implemented to operate vibration generator which was designed as reciprocal mechanism, consisted of electrical motor; speed controller; connecting rod; vibration table; vibration sensor and computer program. How to operate vibration mechanism will be discussed in experimental rig section.

Scale deposited in vibrating-flowing system occurs in specific mechanism as hydrodynamic force exist in the piping system. This hydrodynamic force contributes energy that needed for nucleation and agglomeration as part of scale formation [2]. In other side, hydrodynamic force also potentially removes the younger crystals that not strong enough adhere on the surface of pipe [16]. When scale deposited is measured, these removal scale must be included to avoid the bias in the assesment of vibration influence. Therefore, a strainer was considered to trap scale deposited that carried over by the solution after passing the pipe.

In this research, scale of surface-integration controlled was adhered on the coupon. Typically, coupon is a pipe made of copper which needed that the scale to adhere on. Furthermore, this such scale be named scale deposited in the coupon (Wcoupon). Scale that collected in the strainer could be scale of diffusion controlled reaction and scale that removed from its adherence or removal scale. In fact, too difficult to distinct each other and better if both of scale named as scale deposited in the strainer (Wstrainer). Subsequently, net scale deposited (Wnet) could be calculated from equation 1. Wnet = Wcoupon + Wstrainer (1)

In these experiments, scale deposited was investigated in constant temperature 350C; in various anion fractions and in elevated vibration frequencies 0.00 Hz; 3.00 Hz and 6.00 Hz.

2.2. Material and solution preparation

CaCO3/CaSO4 scale was synthesized by mixing CaCl2.2H2O; Na2CO3 and Na2SO4 solution through dilute the powder to destilled water according to the reaction in equation (2). All of the powder were purchased from Merck® to guarantee the purity.



CaCl2.(aq) + Na2CO3(aq) + Na2SO4(aq) → CaCO3(s) + CaSO4(s) + 2NaCl(aq) (2)

Calcium concentration in the solution was determined in 0.0238 M. Carbonate and sulphate concentration was set each in its stoichiometry.

Addressed to explore crystals properties, carbonate-sulphate anion fractions were set in variously i.e. 0-100; 25-75; 50-50; 75-25 and 100-0 wt%. To prepare the solution, calcium; carbonate and sulphate powder were diluted separately. Calcium solution was prepared by dilute CaCl2.2H2O powder to six litres distilled water. Carbonate solution was prepared by dilute Na2CO3 to six litres distilled water. Sulphate solution was prepared by diluted Na2SO4 to also six litres distilled water. The solution filtrated by filter paper 0.22 μm micropore. Each solution was then stored in a covered vessel to avoid from dust. To set anion fraction, for example in 25 CO3

-

2-75 SO4-2 wt%, carbonate solution as much as 25% × 6.00 litres was added to sulphate solution

in 75% × 6.00 litres and was then mixed in one vessel.

2.3. Experimental rig

A build in-house experimental rig operated by a computer program control was employed to conduct the experiment as shown schematically in Figure 1. Program control monitor is depicted in left side of graph which allows to choose parameter setting by clicking available button. If the value not available on the button, program allows to set by clicking up-down button untill the parameter match to the value needed.

The rig consisted of two vessels contain calcium solution and anion solutions. To ensure the solution in homogeneously, a stirrer mounted in each vessel and set automatically by clicking the button in program control monitor. Temperature was set by an electrical heater immersed in the solution and controlled by a sensor in deviation ± 0.50C. Solution in each vessel was drained by a dosing pump CHEM FEED Ca-92683 and set in flow rate 25 ml/min. Both solutions were reacted in test pipe section. In test pipe section, four pair of coupons were inserted in which the scale was needed to form. The pipe was mounted at a table and vibrated mechanically by an electrical motor which was set-up by a computer program. In this research vibration was set in 0.00; 3.00 and 6.00 Hz. Vibrometer Lutron VT-8204 was selected to record vibration parameter such as displacement peak to peak (m), acceleration (m/sec2-RMS) and was shown in computer program. A filter paper of 0.22 μm was used to screen the crystals brought by flowing solution. A filtering flask and a vacuum pump were employed to help in seizuring the crystals. Filter paper in the funnel was replaced every ten minutes to avoid blockage. Finally the solution was sent to waste vessel.



Figure 1 Experimental rig

Scale found in the coupon and strainer was dried in an electrical heater at 60oC for six hours. Weighing scale mass was done in Ohaus AR-2140 analytical balance when the scale still adhered in the coupon or strainer. Scale mass of coupon was calculated as the difference of coupon mass between with and without scale. Scale mass of strainer was calculated by the difference of strainer mass between with and without scale. Subsequently, the scale was kept in a dry cup after removed from the coupon or strainer and labeled as experiment parameter.

3. RESULTS AND DISCUSSION

3.1. Influence anion fraction and vibration on scale deposited

Scale deposited of the experiment in various vibration frequencies and in various anion fractions have been investigated and will be the main finding of the research. To reveal relationship among parameter in briefly, the data are depicted in Figure 2 which point out the influence of various anion fractions and vibration frequencies on scale deposited. In Figure 2, horizontal axis is labeled as anion fractions in unit wt%. Numeric 0 in the axis means the fraction is 0% SO4

-2-100% CO3-

2; numeric 50 means the fraction is 50% SO4-2 -50% CO3

-2; numeric 100 means the fraction is 100% SO4

-2 - 0% CO3-2.



Figure 2. Binary diagram of CaCO3/CaSO4 scale deposited in various

anion fractions and vibration frequencies

The influence of anion fractions on scale deposited has depicted in the graph shows that scale deposited increase as sulphate anion decrease. This such influence appear in the same manner for the experiment with and without vibration. The influence of vibration on scale deposited also depicted in the graph for various anions fractions. In the experiment of 100% SO4

-2 - 0% CO3-2

or in sulphate anion only, the scale were found 2.4379 g; 2.9911 g and 3.563 g for vibration frequencies 0.00; 3.00 and 6.00 Hz. For the experiment of 0% SO4

-2 -100% CO3-2 or in carbonate

anion only, the scale were found 3.3611 g; 4.0348 g; 4.8205 g for vibration frequencies 0.00; 3.00; 6.00 Hz. In experiment 50% SO4

-2 -50% CO3-2 the scale were found 2.7678 g; 3.3490 g

and 3.9923 g for vibration frequency 0.00; 3.00 and 6.00 Hz. All the experiments resulted scale deposited increased when the vibration was implemented.

The difference between unvibrated and vibrated experiments is focussed on the arising energy of hydrodynamic force that contributed by the vibration. Energy that has been contributed in vibration frequency 6.00 Hz could be calculated based on the data of vibration sensor. The sensor showed the acceleration a = 2 m/s-2 RMS; displacement in s = 0.004 m or in 0.048 m every second (as vibration frequency in 6.00 Hz). The mass of solution in pipe as much as m = 0.013976 kg or in 0.137 N. The time to produce one Mol CaCO3 or (t) = (Molar weight/mass of reaction product) × time in second, so, t = (100/3.9923) × (4 hours × 3,600 second/hour) = 360,694 sec/mol. To calculate energy (E) that contributed by vibration, a formula from Chang and Overby was adopted as equation 3 [18].

E = m × a × s × t (3)

E = 0.137 N 2 m/sec-2 × 0.048 m/sec × 360,694 sec/mol

E = 4,743 J/mol or 4.743 kJ/mol.

Seems that energy has been generated by the vibration as much as 4.743 kJ/mol affects scale deposited increase in significant. The data was then confirmed to the research of Quddus and Hadhrami and shows the agreement which they revealed that the increase hydrodynamic force by stirring the solution from 100 rpm to 1,000 rpm could increased CaCO3 scale deposited from 1.392 g.m-2.h-1 to 4.262 g.m-2.h-1 [2].



3.2. Morphology investigation

Scanning Electron Microscopy (SEM) FEI Inspect S50 was used to determine morphology of scale precipitated using acceleration voltage 20 kV. Scale of the experiment with anion fractions 25 SO4

-2 – 75 CO3-2; 50 SO4

-2 – 50 CO3-2 and 75 SO4

-2 – 25 CO3-2 wt% for unvibrated and

vibrated 6.00 Hz were analyzed. All samples were

Figure 3. Crystals micrograph of the experiment in various anion fractions and vibration frequencies: a).75% SO4

-2-25% CO3-2, 0.00 Hz; b).75% SO4

-2-25% CO3-2, 6.00 Hz; c).50% SO4

-2 -50% CO3-2, 0.00

Hz; d).50% SO4-2-50%CO3

-2, 6.00 Hz; e).25% SO4-2-75% CO3

-2, 0.00 Hz; f).25% SO4-2-75% CO3

-2, 6.00 Hz

mounted at a circular aluminium holder and sputtered with aurum paladium (AuPd) in Sputter Coater EMITEC SC7620. After circular alumunium holder was inserted to SEM chamber, air molecule in chamber was sucked out to find perfict photo micrograph. All photo micrograph were



then depicted in Figure 3 which the micrograph of unvibrated experiment is presented in adjacent of vibrated experiment in mind to make easier in the assasment.

Figure 3a depicts crystal morphology of the experiment without vibration with anion fraction 75 SO4

-2 – 25 CO3-2 otherwise Figure 3b depicts the morphology of vibrated experiment in 6.00

Hz in the same anion fraction. Crystal morphology resulted from unvibrated experiment was vaterite but in different surface. The surface was covered by protrusion and also found any porous in protrusion surface. The protrusion and the porous emerged due to the presence of sulphate anion in 75 wt%. When the vibration was implemented to the experiment in 6.00 Hz, needles or tendrils appeared rightly in the porous position. This mean that the new crystal habit in porous position could be formed but needed more energy. When the vibration was implemented, mechanical energy as much as 4.743 kJ/mol was contributed to the solution and fullfilled the energy that needed for the formation.

Figure 3c depicts crystal morphology of the experiment with anion fraction 50 SO4-2 – 50

CO3-2 wt% and vibration frequency in 0.00 Hz, otherwise experiment with same anion fraction

and vibration frequency in 6.00 Hz is depicted in Figure 3d. Crystal of 0.00 Hz experiment has morphology as normal vaterite but any needle form emerges in its surface. The needle has cross section in hexagonal form which such polymorph usually is owned by vaterite. When vibration was implemented in 6.00 Hz to the experiment in the same anion fraction, crystals surface was fullfilled by hexagonal stick or needle such as shown in Figure 3d. This polymorph indicates strong discrepancy exist due to the implementation of such anion fraction and vibration frequency.

Figure 3e and 3f depict the morphology of unvibrated and vibrated 6.00 Hz experiment respectively. Both of these experiments were conducted in anion fraction in 25% SO4

-2- 75% CO3

-2. The morphology consisted of much needles or tendrils in hexagonal cross section (Figure 3e). When the vibration was affected in 6.00 Hz, the needles or tendrils became more fertill (Figure 3f). Both of these polymorphies could be distincted into two subjects i.e. (i). The birth of needles or tendrils was affected by anion fraction in 25% SO4

-2 - 75% CO3-2 (Figure 3e). (ii). The

growth of needles or tendrils to be more fertill because was affected by vibration in 6.00 Hz (Figure 3f). Further more, the mechanism of anion fraction in influencing the morphology will be discussed in FTIR section.

3.3. FTIR analysis

FTIR analysis was operated to investigate the dried precipitate of unvibrated and vibrated experiment. Sampel of the experiment with anion fraction 50% CO3

-2 – 50% SO4-2 was choosen

to represent the influence of various anion fractions and vibration frequencies that have been implemented in all experiment. All spectrum were recorded in band from 400 to 4,000 cm-1, using IR Prestige88 FT-IR spectrometer which was scan 200 times with spectral resolution of 2 cm-1. The spectrum were stored using a spectroscopic software and was then graphed such as shown in Figure 4.



Figure 4. FTIR analysis of the sample with anion fraction 50 CO3-50 SO4 wt% of unvibrated and vibrated experiment

In the experiment without vibration, bands of 713.66; 1087.85 and 1136.07 Cm-1 emerged and assigned as vaterite formation [19-21]. Band of 744.52 Cm-1 is assigned as calcite formation [19]. Band of 1444.68 Cm-1 is assigned as stretching vibration of CaSO4 lattice mode [22] otherwise band of 1764.87 Cm-1 is assigned as stretching vibration of CaCO3 lattice mode [21]. Shoulder of 1789.94 and 1834.30 Cm-1 are assigned as C-O stretching vibration of CO3 formation [23]. Band of 2507.46 is assigned as O-H symmetric-assymetric stretching vibration of OH from H2O [21]. Bands of 3311.78; 3329.14; 3361.99 and 3442.94 Cm-1 are assigned as stretching vibration of O-H group [24].

When the experiment was affected by vibration in 6.00 Hz, more bands emerged in around 1400 to 1700 Cm-1 and assigned as the associate of lattice mode or the modification of the lattice [21, 22, 25]. Those bands justify the modification crystals morphology that have been depicted in Fig.3 which CaCO3 crystal surface was covered up by large needles or tendrils. Needle habit is usually belong CaSO4 crystals polymorphy and known as rhombohedral [26]. In this experiment, polymorph of CaCO3 crystals in needle-hexagonal form is unusuall. Previously, FTIR analysis has been briefly informed that band of 1444.68 Cm-1 emerged and assigned as stretching vibration of CaSO4 lattice mode [22]. Thus, CaSO4 lattice was proven that has been formed in this experiment, but in XRD analysis, the quantification shows not found CaSO4 in the crystals etal. Based on those data, could be deduced that CaSO4 lattice was not fullfilled by CaSO4 crystals because the reaction between calcium and sulphate anion was not perform. In these experiments, carbonate anion arrogated calcium cation to react and precipitated as CaCO3, thus, calcium cation did not react with sulphate anion. Then, the association between CaSO4 lattice and CaCO3 precipitant resulted new habit of vaterite in needle-hexagonal form such as shown in Figure 3.

3.4. Phases identification

Phases identification was done using Cu-Kα monochromated radiation in a conventional Bragg-Brentano (BB) parafocusing geometry of Rigaku SmartLab X-Ray Diffractometer. Scan parameters 10-1000(2θ); 0.020/step and 15 sec/step were determined. The x-ray data that have been collected were subsequently transferred into a PC-based search-match program for matching crystalline phases. Peak positions and peak heights were matched by the entry data in the ICDD-



PDF (International Centre for Diffraction Data-Powder Diffraction File). The matched crystalline phases were then evaluated by Rietveld method using FullProf-2k, software version 3.30 [27]. AMCSD (American Mineralogist crystal structure database) was used as crystal structure model for Rietveld refinement [28]. Cell parameters and scale factor were refined for determination of the weight % levels of mineralogical phases. Calculation of the weight levels in the phases was performed automatically by FullProf program.

In this research, ten sample have been analized by XRD and their phases were quantificated. These ten sample were resulted from ten experiments in various anion fraction, with and without the influence of vibration. The results of phases quantification was then listed in Table 1.

Table 1 Crystal phases of the experiment in various anion fraction

Anion Fraction Vibration Freq. Phases (wt%)

CO3-SO4 (wt%)

(Hz) Gypsum Bassanite Aragonite Calcite Vaterite

0-100 0.00 58,25 41,75

25-75 0.00 18,48 81,52 50-50 0.00 21,39 78,61 75-25 0.00 28,54 71,46 100-0 0.00 9,81 31 59,19

0-100 6.00 100 25-75 6.00 8,19 91,81 50-50 6.00 9,5 90,5 75-25 6.00 34,38 65,62

100-0 6.00 32,08 36,79 31,13

Data of phases quantification in Table 1 shows the quantification of the experiment in CO3-SO4 anion fraction of 0-100 wt%. The fraction pointed that the experiment was conducted only in single anion i.e. sulphate. When the experiment was run without vibration, two crystals phases were resulted i.e. gypsum (CaSO4.2H2O) in 58.25 wt% and bassanite (CaSO4.0.5H2O) in 41.75 wt%. Then, the vibration was implemented to the experiment in vibration frequency 6.00 Hz, the phases was identified in bassanite only. It could be ascertained that hydrodynamic force contributed by vibration taken a role in the precipitation. As has been understood that the formation of bassanite needs higher energy than gypsum [11]. Seem that the need of energy has been paid by the vibration as much as 4.743 kJ/mol .

Experiment of anion fraction 100% CO3-2 – 0% SO4

-2 wt% mean in single anion or carbonate only, without vibration, resulted phases in 9.81; 31.00 and 59.19 wt% for aragonite; calcite and vaterite respectively. When the vibration was implemented in 6.00 Hz, the phases altered to 32.08; 36.79 and 31.13 wt%. The increase aragonite phase from 9.81 to 32.08 wt% giving a signal that the reaction undergo in higher dynamic as it has been known that the formation aragonite needs higher energy. Trushina pointed that the formation of aragonite starts in temperature 400C [20] meanwhile Heath pointed in temperature 300C [29]. In this experiment, aragonit phases identified as much as 9.81 wt% in temperature 350C shows accordance to the research of Heath.

In the experiment of fraction 25 - 75; 50 - 50 and 75 - 25 wt% of carbonate-sulphate anions and vibration frequency in 0.00 Hz, the phase was dominated by vaterite. Calcite was only formed in meager phase and CaSO4 family was absence. The absence of CaSO4 family in these experiment such listed in Table 1 has been confirmed to PHREEQC prediction program. When PHREEQC operated as the input data of 50-50 wt% of anion fraction, saturation indices of gypsum found as 0.19; CaSO4 anhydrate 0.00; aragonite 1.26 and calcite 1.39. The ratio of ionic



activity product (IAP) and solubility product (Ksp) has been known as saturation indices (Ω). If the value of saturation indices (Ω) ≤ 1.00 indicates that the reaction has no scaling potential [30]. Thus, the absence of gypsum and CaSO4 anhydrate in these experiments were in accordance to PHREEQC prediction. In other side, the absence of aragonite and the presence of vaterite phases in these experiments seem in contrary to PHREEQC prediction. The discrepancy could be deduced that caused by the presence of sulphate anion. Higher sulphate anion in the fraction resulted higher phase of vaterite either for with and without vibration. The data inform that sulphate anion retards calcite and aragonite formation and rightly vaterite predominates the phases. The phenomenon shows in accordance to the research of Chong and Sheikholeslami which they stated that the presence CaSO4 weakened CaCO3 scale [4]. When the vibration was implemented, vaterite phase has gotten more dominated. The phase increased from 81.52 to 91.81 wt% for the experiment in 0.00 and 6.00 Hz vibration frequency respectively. The phenomenon assigned that retardation by sulphate anion on calcite and aragonite formation underwent in seriously when vibration was implemented.

3.5. Crystallographic investigation

Crystallography investigation was conducted to study the formation morphology discrepancy that has been resulted from the experiment. In morphology investigation the discrepancy has been depicted in Fig.3c; 3d; 3e and 3f which new habit crystal has been identified. Aimed to study the discrepancy in briefly, the morphology that has been depicted in Fig.3d is investigated as all of them performed in the same mechanism. The morphology is owned by vaterite but the surface has been covered up by large needles or tendrils. The needle is in hexagonal form that has been known as crystal system of vaterite [31].

Figure 5 Graph of XRD analysis identified by its phases and Miller indices

In Figure 5, vaterite phase is identified in four peaks and has been assigned by its Miller indices, i.e. : V(1 1 0); V(1 1 3); V(1 1 6) and V(2 2 0) for the experiment in 50-50 wt% anion fraction. Line blue represents the experiment without vibration and line red represents experiment in vibration frequency 6.00 Hz. Correspond to needles or tendrils formation such as shown in Figure 6a, these four Miller indices are graphed in Figure 6b and 6c.

Four crystal planes have been shown and entailed with their Miller indices in Figure 6, i.e. : (1 1 0); (1 1 3); (1 1 6) and (2 2 0). The planes and their Miller indices shows in accordance to SEM data such shown in Figure 6a. These all planes justify the growth of the crystal in corresponding to the discrepancy especially when the vibration was implemented.



Figure 6. Graph of CaCO3 crystals planes and labeled by Miller indices

In the experiment of vibration frequency in 6.00 Hz, relative intensity of plane (1 1 0) increase from 31.27% (without vibration) to 51.43% (vibrated in 6.00 Hz) and plane of (2 2 0) increase from 21.85% to 47.67%. Plane of (1 1 3) increase from 51.89% to 100%, but plane of (1 1 6) remain stable in 100%. Base on the data could be deduced that the growth of the crystal was intensively in x and y axis when the vibration was implemented. In the next sequence, the crystal grew to be fertiller hexagonal needle or not in thin needle. This polymorph shows in accordance to the research of Chong and Sheikholeslami in which the addition CaSO4 on CaCO3 formation also resulted new habit crystal in needle-hexagonal form [4].

4. CONCLUSIONS

The experiment to investigate morphology and phases of CaCO3/CaSO4 mixed scale in pipes under the influence anion fraction and vibration frequency has been successfully conducted. In the experiment in various fraction of carbonate and sulphate anion, scale deposit resulted from the experiment was CaCO3 and not found CaSO4 etal. The increase sulphate fraction resulted more vaterite phase and less calcite phase, this mean that sulphate anion had a function as calcite retarder. In the experiment which vibration was implemented in 6.00 Hz, scale deposited increase for all anion fraction. Various carbonate and sulphate anion fraction in all experiment also affected morphology discrepancy which new habit vaterite in needle-hexagonal was found for either vibrated and unvibrated experiment. The needle appeared in larger when vibration was implemented in the experiment. Morphology discrepancy exist due to the presence CaSO4 lattice that has been identified by FTIR analysis. Crystallography investigation shows plane of (1 1 3) increase from 51.89% to 100%, but plane of (1 1 6) remain stable in 100%. Base on the data could be deduced that the growth of the crystal was intensively in x and y axis when the vibration was implemented. In the next sequence the crystal grew to be fertiller needle.



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