Separation and Purification Technology 136 (2014) 66–73

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Separation and Purification Technology

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Use of the ionic liquid-tricaprylmethyl ammonium salicylate (TOMAS)as a flotation collector of quartz

http://dx.doi.org/10.1016/j.seppur.2014.08.0341383-5866/� 2014 Elsevier B.V. All rights reserved.

⇑ Corresponding author. Tel.: +91 674 2379334; fax: +91 674 2567160.E-mail address: bdas@immt.res.in (B. Das).

Hrushikesh Sahoo a,b, Swagat S. Rath b, Bisweswar Das b,⇑a Academic of Scientific and Innovative Research, Bhubaneswar, Indiab CSIR-Institute of Minerals and Materials Technology, Bhubaneswar, India

a r t i c l e i n f o a b s t r a c t

Article history:Received 24 June 2014Received in revised form 26 August 2014Accepted 31 August 2014Available online 10 September 2014

Keywords:Tricaprylmethyl ammonium salicylateQuartzBHQ oreXPSMolecular modeling

Tricaprylmethyl ammonium salicylate (TOMAS), an ionic liquid has been employed as a collector for theflotation of quartz. The sign reversal of zeta potential of quartz from negative to positive values andincrease in contact angle from 80 to 700 by the addition of TOMAS have substantiated the interactionof TOMAS with the quartz surface. The change in morphology as indicated in SEM and two peaks at2933 and 2857 cm�1 owing to the vibrations of CH2 and CH3 as seen in FTIR spectra support the adsorp-tion of the reagent on quartz. The N(1s) peak as observed in the XPS spectra of the quartz treated withTOMAS, and the curve fitting data of C(1s) corroborate the reagent-mineral interaction. A comparativestudy of adsorption of DDA and TOMAS using classical molecular mechanics also suggests strongeradsorption of the latter on the hydroxylated quartz surface. Flotation studies of quartz at natural pH indi-cate �100% quartz recovery at a TOMAS concentration of 8 � 10�5 M. Flotation of the natural occurringBHQ iron ore containing 38.7% Fe and 43.8% SiO2 concludes that a TOMAS concentration of3.71 � 10�5 M is sufficient to achieve 67.3% Fe with 66.6% iron recovery. TOMAS stands out as a betterquartz collector, when compared with DDA.

� 2014 Elsevier B.V. All rights reserved.

1. Introduction

Ionic liquids are salts having poorly coordinated ions, andessentially liquid below 100 �C, or even at room temperature. Theyare made up of ions of typical shapes and sizes. Owing to this, theformation of a stable crystal lattice is prevented, and it remainsliquid at room temperature and does not form vapors. Day byday, the popularity of ionic liquids is increasing due to their easierhandling properties compared to that of salts which melt at ele-vated temperatures. Ionic liquids are also called designer solventsas they can be fine tuned by different combinations of anions andcations according to the requirements [1–5]. They are environmentfriendly and possess typical properties like low-vapor pressure,high viscosity, dual natural polarity, good thermal stability and awide range of miscibility with water and other organic solvents,and avoid many environmental and safety problems [6–11]. Someof the ionic liquids based on ammonium, phosphinium, imidazoli-um, pyridinium are used as phase-transfer catalysts, solvents,lubricants, gas capture agents, coating materials, or chemicalsensors [12–17].

Tricaprylmethyl ammonium salicylate (TOMAS) is anammonium based ionic liquid derived from the aliquat cation. Itis prepared by the anion exchange of the chloride anion of Aliquat�

336 (a mixture of tri-octyl/decylammonium chloride) with a salic-ylate anion [18,19]. TOMAS is generally used as a metal extractingsolvent for Fe, Cu, Mn, Zn and Ni [20]. However, TOMAS or anyother ionic liquids have not seen their application in mineralflotation till date.

It is well known that dodecylamine or its chloride or acetatesalts are used as the flotation collector of quartz and silicates fromdifferent ores. Several amines like dodecylamine, coco amine, tal-low-amine and ether amines are used to separate silica from ironores [21–23]. It is often reported that monoamines containing10–12 carbon atoms are generally used in reverse flotation of ironores effectively [24,25]. Earlier it was suggested that ammoniumions of the monoamines are attached to the quartz surface throughelectrostatic forces [26,27]. However, XPS and infrared spectros-copy evidenced the formation of hydrogen bonds between theammonium head and the quartz surface [28]. Very recently, DFTcalculations have confirmed the geometry of H-bonds that formbetween different amines and quartz [29]. The flotation of ironore for the recovery of iron values is dependent on its characteris-tics, liberation of mineral values and the association of silica/silicates with the iron oxide minerals. The increase in flotation

H. Sahoo et al. / Separation and Purification Technology 136 (2014) 66–73 67

recovery also depends on the choice of collectors and their adsorp-tion behavior. Besides that, the collector dosages should be mini-mized for the economic and environmental point of view insubsequent downstream processing.

The development of collectors for economic flotation of mineralvalues has been attempted by many investigators. Yuhua and Jian-wei [30] developed a low cost quaternary ammonium salt namedCS-22, which displayed better collecting capacity and selectivityin comparison to dodecylamine. The literature study indicatesthe application of many such low cost collectors with quaternaryammonium nitrogen for the successful flotation of quartz[31–33]. The reagents such as N-dodecyl-b-amino-propylamide,dodecyl-ammonium ion, and medium-chain ether-amine acetateshave been successfully used for the flotation of quartz from ironore [34]. Huang et al. [35] used a gemini surfactant (a dimer ofmonomer surfactants linked by a spacer) in the flotation of ironore and the flotation response was compared with the dodecylam-moniumchloride. In this study, they suggested electrostaticinteraction of gemini surfactant with the quartz surface.

In the present study, TOMAS, an ionic liquid which containsquaternary ammonium group has encouraged us to implement itin the flotation of quartz from iron ore in particular. Flotation ofpure quartz as well as a low grade banded hematite quartzite ironore containing silica as the major impurity was attempted withTOMAS. Different analytical studies such as zeta potential, FTIR,CMC and XPS were carried out to validate the interaction of thereagent with quartz. Besides that, molecular mechanics calcula-tions were done to evaluate the comparative adsorption behaviorof DDA and TOMAS on quartz surface.

2. Materials and methods

2.1. Experimental

Quartz sample containing 99.2% of SiO2 was collected from oneof the quartz mines of Odisha, India. The sample was subjected tocrushing followed by grinding in a laboratory ball mill in order toobtain the �100 lm sample for flotation studies. High purity silicawas obtained by leaching with dilute hydrochloric acid to removesome contaminated iron oxides. The dissolved iron oxide and otherimpurities were separated by sedimentation followed by washingwith distilled water. The sample was ground to below 10 lm in apulverizer for FTIR, contact angle and zeta-potential studies.Banded hematite quartzite (BHQ) was collected from one of theiron ore mines of India. The samples are very hard, laminated, mas-sive, and reflect the band structures of hematite and quartz. Thebands are unevenly spaced ranging from few microns to few cen-timeters. The rock samples were ground to below 100 lm sizefor the flotation studies.

TOMAS was supplied by Cognis Inc., USA, and was used as suchwithout any further purification. It was used in flotation after dis-solving a known amount of the reagent in ethanol. Soluble starch,supplied by Merck, India was used as depressant for hematiteparticles.

The zeta potential studies of the quartz samples were carriedout by a zeta probe analyzer with inbuilt titration method. In theseexperiments, 2% solid slurry was taken with finely ground quartzparticles. Experiments were carried out with various concentra-tions of TOMAS applied to the slurry in a pH range from 2.5 to10.5. Phoneix 300 (Surface Electrooptics) instrument was used tomeasure the contact angles using the free sessile drop method.Pellets were made out of finely ground quartz particle and thesame fine particles are conditioned in different concentrations ofTOMAS for half an hour, dried and then pelletized in a hydraulicpress with 10 ton pressure. The water drop falls on the smooth

surface of the pellet and measurements were made. The FTIR stud-ies of the samples were carried out in a Shimadzu FTIR in the rangeof 400–4000 cm�1 over KBr disc pellets. Determination of criticalmicelle concentration (CMC) by conductance measurement wascarried out using a conductivity meter. Scanning electronmicroscopy was studied using a Hitachi 3400N scanning electronmicroscope. The X-ray photoelectron spectroscopy (XPS) of thesample was carried out using the equipment S/N: 10001, Prevac,Poland. The binding energies were determined from the spectrataken with Al Ka (ht = 1486.6 eV) radiation and a hemisphericalenergy analyzer. An instrument base pressure of 6 � 10�10 mbarswas maintained during the data acquisition. All the treated quartzsamples were prepared by adding a known concentration ofTOMAS and then conditioned in a laboratory stirrer for 30 min.At the end, the particles were separated by filtration, thoroughlyrinsed with distilled water and dried at room temperature. Polyvinyl alcohol (PVA) was applied as a binder during the preparationof the pellet.

Flotation experiments of quartz and naturally occurring BHQore were carried out using a Denver D-12 sub-aeration flotationmachine having 1 L capacity cell. The solid concentration wasmaintained at 10% and the suspension was agitated for 3 min at1500 rpm. The pH of the suspension was adjusted to the desiredvalue by the addition of small amount of acid or alkali. Then starchand collector were added into the cell orderly with one minuteinterval of conditioning time. The concentrate and tailings werecollected separately, dried, weighed, and analyzed for grade andrecovery. Flotation studies of pure quartz mineral system were car-ried out using distilled water while laboratory tap water was usedfor BHQ ore.

2.2. Computational methodology

Other than pure experimental methods, the comparative per-formance of TOMAS and DDA as collectors for quartz was studiedvia molecular modeling. The adsorption behavior of both thereagents on quartz surface was modeled using force field methods.Here the consistent-valence force field (cvff) [36,37] as imple-mented in the Forcite module in Materials studio 6.1 [38] was usedfor the geometric optimization of the structures. The force field cvffhas been successfully employed for organic-silica interface earlier[39,40]. Smart minimizer was used for the geometric optimization.The convergence criteria for the energy, force and displacementwere set at 2 � 10�5 kcal/mol, 0.001 kcal/mol/Å and 1 � 10�5 Årespectively. Ewald summation method was used for calculatingthe non-bonded electrostatic as well as Van der Waals interactions[41].

3. Results and discussion

3.1. Zeta potential

The zeta potential study of quartz and quartz treated withTOMAS was carried out at different pH values by varying the con-centration of TOMAS and shown in Fig. 1. The zeta potential ofquartz is found to be negative in all the pH values under study. Itwas observed that the addition of TOMAS into the quartz suspen-sion has changed the potential values from negative to completepositive values indicating strong interaction of quartz and TOMASat all pH values. The zeta potential values increase upon increasingthe TOMAS concentration from 0.2 � 10�5 M to 0.8 � 10�5 M. It hasbeen observed that after a certain concentration, the change in thepotential values is negligible. This may be attributed to the micelleformation of TOMAS.

-80

-100

-60

-40

-20

0

20

40

60

80

2 4 6 8 10

Zeta

pot

entia

l, m

v

pHQuartz0.2*10E-5 M0.4*10E-5 M0.6*10E-5 M

Fig. 1. Zeta potential of quartz and quartz treated with different concentrations ofTOMAS. Fig. 3. FTIR spectra of quartz and quartz treated with TOMAS.

68 H. Sahoo et al. / Separation and Purification Technology 136 (2014) 66–73

3.2. Measurement of contact angle

Hydrophobicity of the treated quartz with TOMAS was evalu-ated to compile the efficiency of TOMAS in quartz flotation andshown in Fig. 2. All experiments were carried out at natural pHof water. The concentration of TOMAS was varied from0.5 � 10�5 M to 2.5 � 10�5 M. It is observed that the bare quartzsample shows a contact angle of 8�. The value of contact anglegradually increases with an increase in TOMAS concentration. At2.5 � 10�5 M concentration, the contact angle is as high as 70�.The gradual increase in contact angle reveals the increase of hydro-phobicity, which is likely to enhance the flotation recovery ofquartz.

3.3. FTIR

Quartz and quartz treated with TOMAS were subjected to infra-red spectroscopic study in order to understand the interaction pat-tern and the spectra are shown in Fig. 3. In both the samples, thebroad peak around 3385 cm�1 corresponds to hydroxyl group.The peaks ranging from 400 to 1200 cm�1 in both the samples indi-cate the characteristic peaks of quartz and impassive peaks ofquartz confirming no chemical bonding between quartz andTOMAS [42,43]. Si–O stretching vibration peaks appear at around1156 cm�1. The sharp peak around 1036 cm�1 corresponds toSi–O–Si asymmetric stretching. The two additional peaks appear-ing at 2933 and 2857 cm�1 refer to the CH3 and CH2 stretching fre-quency indicating the adsorption of TOMAS with quartz particles.

0

10

20

30

40

50

60

70

80

0 0.5 1 1.5 2 2.5

Con

tact

ang

le,

TOMAS conc*10-5M

Fig. 2. Contact angle of quartz treated with TOMAS.

3.4. SEM studies

The SEM studies of pure quartz and quartz treated with TOMASwere carried out in order to visualize any change in the morphol-ogy. Fig. 4(a) representing the morphology of quartz shows theangular grains dispersed throughout the sample. The morphologyof the sample after treatment with TOMAS is given in Fig. 4(b),which shows the coagulated and aggregated species instead ofdispersed angular quartz grains. In this sample no free quartz par-ticles are observed, which evidence the interaction of TOMAS withquartz finding its way towards flotation.

3.5. CMC study

Critical micelle concentration (CMC) is the concentration abovewhich monomer surfactant molecule aggregates abruptly to formmicelles. Hence it is an indication to use the collector below thatconcentration. The CMC calculated using Fig. 5 was found to be0.28 � 10�3 M, which is less when compared with the CMC ofdodecylamine i.e. 1.3 � 10�2 M [44]. The Gibbs free energy ðDGÞof micellization was calculated from the equation as written below.

DG ¼ RTLnðCMCÞ

The Gibbs free energy values were evaluated to be �20.3 kJ/mol and�10.83 kJ/mol for the reagent TOMAS and DDA respectively. Again,more negative the free energy more is the ease of formation of amicelle. These results indicate that required concentration ofTOMAS should be less than that of DDA for achieving the same flo-atability. Similar investigations on CMC measurement with respectto carbon chain length suggested the decrease in CMC with anincrease in carbon chain length [44].

3.6. XPS study

The XPS spectra of quartz and quartz treated with TOMAS wereanalyzed and shown in Fig. 6. A value of 285.0 eV was adopted asthe standard C(1s) binding energy. In quartz spectra, the peaksaround 102.6 and 150.5 eV energy correspond to the presence ofSi(O) and Si(2s) respectively. In both the spectra, the unchangedpeaks of Si(O) and Si(2s) indicate null chemical bonding betweenquartz and TOMAS. The peak of 531.8 eV in both the spectra corre-sponds to O(1s). But spectra of quartz treated with TOMAS has asmall peak at 398.4 eV that corresponds to N(1s), which is absentin the quartz spectra. The new peak of nitrogen in the spectra ofTOMAS treated quartz shows the presence of nitrogen from TOMASand confirms the adsorption onto the quartz surface.

C(1s) peak of each spectra was subjected to curve fitting (Fig. 7)and the data available is summarized in Table 1. In each spectrum,

Fig. 4. SEM image of (a) quartz and (b) quartz treated with TOMAS.

20

22

24

26

28

30

0 0.5 1 1.5 2 2.5

Con

duct

ance

, µs

TOMAS conc* 10-3M

Fig. 5. Conductance of TOMAS in water.

0 200 400 600 800 1000 1200

N(1s)

Si(0)

Inte

nsit

y (a

.u)

Binding Energy (eV)

Si(2s)

Si(0) Si(2s)

C(1s)

O(1s)

O(1s)

C(1s)385 390 395 400 405 410

N(1s)

Quartz treated with TOMAS

Quartz

Fig. 6. XPS spectra of quartz and quartz treated with TOMAS.

285.7

286.6

280 283 286 289 292

Binding Energy (eV)

Inte

nsit

y (a

.u)

C1s

285.7

286.6

280 283 286 289 292

Binding Energy (eV)

Inte

nsit

y (a

.u)

C1s

(a)

(b)

Fig. 7. Curve fitting of C(1s) from both the spectra.

H. Sahoo et al. / Separation and Purification Technology 136 (2014) 66–73 69

it shows the presence of two split peaks of C–H (285.7 eV) and C–O(286.6 eV) bond [45]. The presence of two different peaks indicatesthe adsorption of TOMAS and PVA together, or adsorption of onlyPVA. In both the spectra, area under the curves reveals the adsorp-tion of TOMAS onto quartz surface. Area under the peak of quartztreated with TOMAS is more compared to that of the untreatedquartz, which indicates the adsorption of TOMAS onto the quartzsurface.

3.7. Molecular modeling calculations

The quartz surface cell was created by cleaving the bulk unitcell of quartz at the plane (101) using 3 layers of Si3O6 units. Liter-ature suggests the use of the quartz (101) surface for molecularmodeling of adsorption of an ester containing ammonium collector[29,31]. Considering the importance of the surface hydroxyl groupsof quartz in an aqueous system of flotation, the surface oxygenatoms were hydrogenated. The nonhydroxylated quartz (101) sur-face has two Si–O dangling bonds and upon hydrogenation; thesurface was terminated with two vicinal hydroxyl groups. Thebottom of the surface cell was hydrogenated in order to avoidany spurious interactions. A vacuum of 30 Å was introduced alongthe c-axis and a super cell (6 � 6) containing 324 Si, 648 O atomsand 144 H atoms was built up with this. Only the top layer wasallowed to relax during all structural optimizations while the frac-tional coordinates of the rest of the atoms were fixed. Cationic partof both the reagents i.e dodecyl ammonium ion and tri caprylmethyl ammonium ion were created in periodic cells of30 � 30 � 30 Å. The reagent molecules and ions were allowed to

Table 1Curve fitting details.

Sample C–H peak area C–H center C–O peak area C–O center

(a) Quartz with PVA 9053 285.7 4992 286.6(b) Quartz adsorbed with TOMAS with PVA 40,840 285.7 23,590 286.6

70 H. Sahoo et al. / Separation and Purification Technology 136 (2014) 66–73

relax completely during the optimization steps. The mineral sur-face and both the reagent ions were optimized with the calculationsettings as given above. The input structure of the reagent-mineralcomplex was created by docking the optimized reagent ion on theoptimized mineral surface taking into consideration the possibleinteractions. Around 25 initial conformations were optimized andthe minimum energy conformation was considered as the opti-mized mineral-reagent complex.

The total adsorption energy (DEads) for the reagent-quartz inter-action was calculated using the following expression:

DEads ¼ Ecomplex � ðEreagent þ EquartzÞ

where Ecomplex refers to the energy of the optimized adsorption con-figuration of the reagent and quartz, whereas Ereagent and Equartz

refer to the total energy of the reagent and the hydroxylated quartzsurface, respectively. More the negative adsorption energy more isthe exothermic adsorption and stronger is the interaction of thereagent on the quartz surface.

The most stable complexes of dodecylammonium and tricap-rylmethyl ammonium ions on the hydroxylated quartz (101)

113.46°, 2

150.33°, 1.95

O

O

(a)

(b)

Fig. 8. Interaction of hydroxylated quartz (101) with (a) dodec

surface are shown in Fig. 8. Over the lattice, the H atoms of thedodecyl ammonium ion form four hydrogen bonds with the sur-face oxygen atoms, which are displayed by dotted lines in the fig-ure. The respective N–H–O bond angle and H–O bond length arepresented in the figure. In contrast, the TOMAS ion doesn’t formany H-bond with quartz surface. This is due to the unavailabilityof H atom with the quaternary N. The corresponding adsorptionenergies were calculated as �226 kJ/mol for the interaction ofDDA with quartz (101) and �262 kJ/mol for the TOMAS-quartz(101) interaction. The presence of long alkyl chain with TOMASgreatly stabilizes the ammonium ion by inductive effect. More sta-ble the ammonium ion of reagent, stronger the interactionbetween quartz with reagent. This suggests better adsorption ofTOMAS on the quartz surface.

3.8. Flotation studies

3.8.1. Flotation of pure quartzComparative study on the collective performance of TOMAS and

DDA in pure quartz flotation was carried out (Fig. 9(a)). For both

159.13°, 1.93Å

119.84°, 2.39Å.4Å

Å

N

HH

H

O

O

ylammonium ion and (b) tricaprylmethyl ammonium ion.

40

45

50

55

60

65

70

75

80

85

90

0 1 2 3 4 5

Fe g

rade

& re

cove

ry, %

TOMAS conc*10-5M

Fe grade

Fe recovery

Fig. 10. Effect of reagent concentration on BHQ flotation.

456 7 8 9 10 11

50

55

60

65

70

75

Fe g

rade

& re

cove

ry, %

pH

Fe grade

Fe recovery

Fig. 11. Effect of pH on BHQ.

H. Sahoo et al. / Separation and Purification Technology 136 (2014) 66–73 71

the reagents, collector concentration was varied from 0.5 � 10�5 Mto 20 � 10�5 M. It is observed that 100% quartz recovery could beachieved with only 8 � 10�5 M of TOMAS concentration, whereas20 � 10�5 M of DDA was consumed for achieving the same. Thesevalues are in agreement with the results obtained from CMCmeasurement and molecular modeling, which predict TOMAS asa better collector compared to DDA. Again flotation experimentswere done with pH as a factor while both the reagents wereapplied at a fixed concentration of 2 � 10�5 M. The pH values werevaried from 3.5 to 10.5. Results shown in Fig. 9(b) describe thehigher recovery of quartz using TOMAS at all pH values. At pH7.5, quartz recovery with respect to TOMAS was around 74%,whereas only 22% could be floated with DDA. It was also observedthat at both acidic and basic pH values, the recovery of quartz wasfound to be less than that at natural pH. It is an indication thatTOMAS can be applied as the flotation collector to float the ganguemineral like quartz from a naturally occurring iron ore containingsilica as the major impurity.

3.8.2. Flotation with BHQ oreWith the impressive result of quartz collectivity, in the same

manner, the reagent was applied to the naturally occurring bandedhematite quartzite ore. The XRD studies of BHQ sample carried outearlier indicated the presence of hematite and quartz as the twomajor minerals [46]. It was therefore aimed to remove the quartzcontent from BHQ ore by the use of this ionic liquid as the collec-tor. In the set of experiments, the collector concentration was var-ied from 0.5 � 10�5 M to 4.5 � 10�5 M. Starch dosage of 500 g/tonwas used as the hematite depressant and no frother was used.The results of the flotation studies as a function of TOMAS concen-tration is shown in Fig. 10. Here, an increase in Fe grade could beobserved with the increase in collector concentration with a simul-taneous decrease in Fe recovery. It was observed that, the Fe gradeof 69% which is equivalent to pure hematite could be achieved at acollector concentration of 4.5 � 10�5 M. Even at 3.71 � 10�5 M con-centration of the reagent, the Fe grade of 67% Fe with a satisfactoryrecovery of 66.6% could be achieved.

As pH is an important parameter in any flotation system, theeffect of pH in the flotation of BHQ ore was studied. The effect ofpH was verified from 6 to 11 and the results are shown inFig. 11. In all the experiments, the reagent and the starch concen-tration were fixed at 3.71 � 10�5 M and 500 g/ton respectively. Ithas been observed that maximum Fe grade of 67% was obtainedwith a Fe recovery of 66.6 at pH � 7.0. In all basic pH range, theFe grade was better compared to that in acidic pH range, but therecovery gradually goes down with an increase in the pH value.

In reverse flotation, depressant plays an important role. In allthe experiments, soluble starch was used as the hematite depres-sant. The effect of depressant was estimated by varying the

0102030405060708090

100

Qua

rtz

reco

very

, %

Reagent conc*10-5M

DDA

TOMAS

(a)

0 5 10 15 20

Fig. 9. Flotation studies with quartz (a) reag

soluble starch dosage from 0 to 1500 g/ton. The result of theflotation studies as a function of starch concentration is shownin Fig. 12. It is observed that with the increase in starch dosage,initially Fe grade increases and after a certain limit, it decreasesgradually. A reasonable amount of starch in flotation systemhelps in depressing the iron particles resulting in better selectiv-ity of reagent towards quartz. With excess of starch, iron phasealong with quartz phases gets depressed resulting in lowfloatability of quartz particles.

10

20

30

40

50

60

70

80

Qua

rtz

reco

very

, %

pH

DDA

TOMAS

(b)

3 5 7 9 11

ent concentration and (b) pH variation.

600 300 600 900 1200 1500

62

64

66

68

70

72

74

Fe g

rade

& re

cove

ry, %

Starch conc, g/t

Fe grade

Fe recovery

Fig. 12. Effect of starch concentration on BHQ.

72 H. Sahoo et al. / Separation and Purification Technology 136 (2014) 66–73

4. Conclusion

Flotation behavior of quartz with the ionic liquid tricaprylmeth-yl ammonium salicylate (TOMAS) as a collector has been assessedfor the first time. The zeta potential and contact angle measure-ment studies of quartz have indicated the shift in electrochemicalpotential and increase in hydrophobicity in the presence of TOMASrespectively. In FTIR studies, the extra peaks of CH3 and CH2

stretching frequencies indicate the adsorption of the reagent ontoquartz. Presence of nitrogen peak in the XPS spectra of the TOMAStreated quartz and the curve fitting data of carbon confirm theadsorption. The change in morphology observed in the SEM micro-graph of TOMAS treated quartz particles suggests the reagent coat-ing on quartz surface. CMC calculation indicates lowerconsumption of TOMAS in comparison to DDA. Molecular model-ing of the interaction of quartz with DDA and TOMAS indicatescomparatively stronger adsorption in case of TOMAS. In purequartz flotation, around 100% quartz could be recovered by using8 � 10�5 M of TOMAS, which was found to be much lesser thanthe DDA concentration used to achieve the same floatability. Theflotation of the low grade BHQ ore using TOMAS resulted in a Fegrade of 67.3% with 66.6% Fe recovery.

Acknowledgement

The authors are thankful to the Director, CSIR-IMMTBhubaneswar for his kind consent to publish this paper.

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