Journal of Industrial and Engineering Chemistry xxx (2014) xxx–xxx

G Model

JIEC-1756; No. of Pages 8

Adsorptive removal of nitrate from synthetic and commerciallyavailable bottled water samples using De-Acidite FF-IP resin

Mu. Naushad, Moonis Ali Khan *, Zeid Abdullah ALOthman, Mohammad Rizwan Khan

Advanced Materials Research Chair, Department of Chemistry, College of Science, Building #5, King Saud University, Riyadh, Saudi Arabia

A R T I C L E I N F O

Article history:

Received 26 August 2013

Accepted 2 December 2013

Available online xxx

Keywords:

Nitrate

Anion exchange resin

UPLC–MS

Bottled water sample

A B S T R A C T

The adsorptive potential of De-Acidite FF-IP resin for the removal of nitrate (NO3�) from synthetic as well

as commercially available bottled water samples was testified. Ultra-performance liquid chromatogra-

phy–mass spectrometry (UPLC–MS) was utilized for detection and determination of NO3�. Optimum

NO3� adsorption was observed at pH range 2 to 6. Kinetic studies revealed the applicability of pseudo-

first-order kinetic model for analyzed concentration range (100–300 mg/L) while, the equilibration time

(25 min) was independent of initial NO3� concentration. The breakthrough capacities in Milli-Q and tap

water were 35 and 30 mg/g, respectively.

� 2013 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights

reserved.

Contents lists available at ScienceDirect

Journal of Industrial and Engineering Chemistry

jou r n al h o mep ag e: w ww .e lsev ier . co m / loc ate / j iec

1. Introduction

Agricultural water runoffs and sewage disposal are the majorcontributors for overwhelming increase in nitrate (NO3

�) concen-tration in hydrologic networks. The excessive NO3

� content inwater systems results in growth of aquatic plants, includingharmful algal blooms as well as depletion of dissolved oxygen thatsubsequently results in declination of aquatic life. On humans,excessive NO3

� consumption results methemoglobinemia ininfants, cancer, brain tumors, leukemia and nasopharyngeal tumor[1]. Considering the toxic effects of NO3

� on both flora and fauna,stringent regulations have been imposed by various countries andenvironmental protection agencies to limit NO3

� in waterdischarges and supplies. The regulation set by United StatesEnvironmental Protection Agency (US EPA) [2] and Bureau of IndiaStandards (BIS) [3] for NO3

� in drinking water is 45 mg/L while,World Health Organization (WHO) sets 10 mg/L NO3

�–N as apermissible limit in drinking water [4]. Various treatmenttechniques such as chemical reduction [5], reverse osmosis [6],electrodialysis [7], and biological treatment [8] have beenengineered to remove or to minimize NO3

� in water systems.Chemical reduction using zero valent iron showed extensively highpotentiality for NO3

� removal but production of ammonia is anissue of concern [9]. While, regular membrane replacement, highoperating pressure and voltage makes reverse osmosis and

* Corresponding author. Tel.: +96614674198.

E-mail addresses: moonisalikhan@gmail.com, mokhan@ksu.edu.sa (M.A. Khan).

Please cite this article in press as: M. Naushad, et al., J. Ind. Eng. Ch

1226-086X/$ – see front matter � 2013 The Korean Society of Industrial and Engineer

http://dx.doi.org/10.1016/j.jiec.2013.12.026

electrodialysis processes as economically non-feasible. Though,biological denitrification is relatively economical but it requireslarge size reactor and is ineffective in cold climatic zones due to thereduction in microbial activity [10]. Adsorption is a widelyacclaimed water decontamination technique. Low operationalcost and performance reliability are the major merits of adsorptionprocess. Rapid adsorptive interactions often enable instantaneousremoval of contaminants from source water on a continuous-flowbasis and high production rates can be achieved with good systemhydrodynamics [11]. Activated carbon (AC), a most widely usedcommercial adsorbent, is well known for NO3

� removal [12,13].Disposal or regeneration of exhausted AC is often an issue ofconcern. Land fill sites are commonly used for the disposal of AC.Besides disposal, thermal or steam regeneration processes arecarried out in well specialized plants. On economics ground, ACregeneration is a costly process specifically for small scaleindustrial units [14].

The use of resins as adsorbent for water decontamination isincreasing as they are chemically stable and have the ability tocontrol surface chemistry [15]. Structurally resins are granularresulting less pressure drop in column operations and they couldbe regenerated economically. Previous studies reported use ofpolymeric resins such as amberlite IRA 400 [15], amberlite IRA 410[16], amberlite1 IRN 9766 [17], Purolite [18], AMP16-FeCl3 [19],D417 [20], nano sized zero valent iron polymeric resin [21],Purolite A-520E resin [22], Indion NSSR resin [23] for the removalof NO3

�. The NO3� adsorption capacity on AMP16-FeCl3 resin was

285.8 mg/g [19] while, maximum monolayer adsorption capacityfor NO3

� on Indion NSSR resin was 119 mg/g at 308 K [23]. Though,

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ing Chemistry. Published by Elsevier B.V. All rights reserved.

M. Naushad et al. / Journal of Industrial and Engineering Chemistry xxx (2014) xxx–xxx2

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these works reported appreciable NO3� removal from aqueous

phase but did not test the application of resin on commerciallyavailable water samples. Owing to aforementioned merits of resinsas adsorbents, in this study, we have utilized cross linkedpolystyrene based strongly basic anion exchange resin (De-AciditeFF-IP) for the removal of NO3

�. Kinetics, thermodynamics,isotherm, breakthrough and desorption studies were carried out.The practical applicability of De-Acidite FF-IP for NO3

� removalwas testified on commercially available bottled water samples.

2. Experimental

2.1. Chemicals and materials

Cross linked polystyrene based strongly basic anion exchangeresin De-Acidite FF-IP (OH� form, SRA 70, 52–100 mesh size) waspurchased from Permutit Company Ltd. (London, England). Sodiumnitrate (NaNO3, Reagent Plus1; assay purity �99.0%) waspurchased from Sigma-Aldrich, Germany. Water was purifiedwith a Milli-Q water purification system (Millipore, Bedford, MA,USA). All solvents, chemicals and reagents were of analytical orHPLC grade or as specified. Glassware used were supplied by Schott(Duran, Germany), cleaned with distilled water followed by Milli-Q

water and dried at 313 K. The stock solution of NO3� (1000 mg/L)

was prepared in Milli-Q water and was further diluted to preparesynthetic NO3

� samples and instrumental calibration solutions.Standards and samples were filtered through 0.22 mm PVDFsyringe filters (Membrane Solutions, Texas, USA) before beinginjected into the UPLC–MS system for their analysis. To remove theadhered impurities from the resin surface, it was washed withMilli-Q water for five times followed by drying at 313 K for 10 h.The dried resin was stored in sealed poly bags and was kept in adesiccator until used.

2.2. Quantitative NO3� determination

2.2.1. Analytical technique

Ultra-performance liquid chromatography (UPLC1) system,equipped with a quaternary pump system (Waters, Milford, MA,USA), using an Acquity BEH C18 column (50 mm � 2.1 mm i.d.,1.7 mm particle size) (Waters, Milford, MA, USA) at roomtemperature was used to quantify NO3

� in synthetic and bottledwater samples [1]. The Optimum chromatographic separation ofNO3

� was achieved at pH: 7 in isocratic mode with methanol:water (40:60, v/v) at 200 mL/min flow rate. The sample injectionvolume was 5 mL. An Acquity UPLC1 system, from Waters, wascoupled to a Quattro PremierTM triple quadrupole mass spectrom-eter (Micromass, Milford, MA, USA) with an electrospray ionization(ESI) source (Z-spray) operating in negative ionization mode. Theacquisition was performed in Selected Ion Recording (SIR) modemonitoring the trace m/z 62.0 that corresponded to [NO3

�]. Theworking parameters were as follows: capillary voltage, �3.5 kV;cone voltage, �30 V; source temperature, 393 K; desolvationtemperature, 623 K; desolvation gas flow rate, 600 L/h; cone gasflow rate, 60 L/h. Nitrogen (99.99% purity), produced with a PeakScientific nitrogen generator model NM30LA (Inchinann, UK), andargon (99.99% purity), obtained from Speciality Gas Centre (Jeddah,Saudi Arabia), were used as cone and collision gases, respectively.An Oerlikon rotary pump, model SOGEVAC SV40 BI (Paris, France)provided the primary vacuum for the mass spectrometer.MassLynx V4.1 software (Waters, Milford, MA, USA) was usedfor data acquisition and processing.

2.2.2. Quality assurance and quality control

The qualitative parameters of the UPLC–MS method wereevaluated [1]. The linearity of the method was investigated over a

Please cite this article in press as: M. Naushad, et al., J. Ind. Eng. Ch

concentration range between 0.01 and 10 mg/mL. The correlationcoefficient (R2) obtained, R2 > 0.999, confirmed that the responsewas linear over 3 orders of magnitude. The limits of detection(LOD) (signal-to-noise ratio, 3:1) and limit of quantification (LOQ)(signal-to-noise ratio, 10:1) were 0.1 and 0.4 ng/mL, respectively.These values were calculated analyzing two replicates of a blanksample (Milli-Q water) spiked with NaNO3 at low concentration(10 ng/mL).

2.3. Resin characterization

The surface physical morphology of De-Acidite FF-IP resin(before and after NO3

� adsorption) observed by using scanningelectron microscope (SEM; JSM-6380 LA, Japan). Energy-dispersiveX-ray spectroscopy (EDS or EDX) is an analytical technique whichutilizes X-rays that are emitted from the specimen whenbombarded by the electron beam to identify the elementalanalysis or chemical characterization of a sample. The EDS ofDe-Acidite FF-IP resin before and after NO3

� adsorption wasrecorded.

Surface functional groups actively involved during NO3�

adsorption, were detected by Fourier Transform Infrared (Nicolet6700 FTIR Thermo Scientific) analysis. Dried resin sample (10 mg)was thoroughly mixed with KBr (100 mg) and was ground to a finepowder. A transparent disc was made by applying a pressure of 80psi in a moisture free atmosphere. The FTIR absorption spectrawere recorded from 450 to 4000 cm�1 with an average of 32 scansat �4.0 cm�1 resolution.

2.4. Batch adsorption and desorption studies

The adsorption of NO3� onto De-Acidite FF-IP resin was carried

out by batch mode. Synthetic NO3� sample (20 mL) in aqueous

phase of specified concentrations was treated with De-Acidite FF-IP resin (0.1 g) in a stopper cork conical flask in temperaturecontrolled water bath shaker (SW22/9550322, Julabo, Germany).After attaining equilibrium, sample was withdrawn and filteredthrough 0.22 mm PVDF filter and injected into UPLC–MS system todetermine the residual NO3

� concentration. The amount of NO3�

adsorbed, qe (mg/g), was calculated by mass balance relationshipwhich can be expressed as:

qe ¼ðCo � CeÞV

m(1)

where, Co and Ce are the initial and equilibrium NO3� concentra-

tions in solution (mg/L), respectively, V is the volume of solution(L), and m is the mass of the adsorbent (g). During thermodynam-ics, kinetics, and pH studies, reaction temperature (293–323 K),time (0–60 min) and solution pH (2–10) were varied followingaforementioned experimental protocol.

For batch mode desorption studies, De-Acidite FF-IP resin wasinitially saturated with NO3

� solution of specified concentration.The saturated De-Acidite FF-IP resin was washed several timeswith Milli-Q water to remove unadsorbed NO3

� traces. The eluentsviz. hydrochloric acid (HCl), sulfuric acid (H2SO4), citric acid (CA),oxalic acid (OA) and sodium hydroxide (NaOH) were used to elutethe adsorbed NO3

� from De-Acidite FF-IP resin.

2.5. Breakthrough studies

The breakthrough studies were carried out in a glass column(0.6 cm internal diameter) with a glass wool support. One gram ofDe-Acidite FF-IP resin was taken in the column and 1 L of NO3

�

solution of 100 mg/L initial concentration (Co), prepared in Milli-Q

water and tap water (TW), were passed through the column with aflow rate of 1 mL/min. The samples were collected in 50 mL

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M. Naushad et al. / Journal of Industrial and Engineering Chemistry xxx (2014) xxx–xxx 3

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JIEC-1756; No. of Pages 8

fractions and the amount of NO3� (C) was determined in each

fraction by UPLC–MS. The breakthrough curve was obtained byplotting C/Co versus volume of the effluent.

2.6. Real sample applications

The commercially available bottled water of different brandswas purchased from local supermarket, Riyadh, Kingdom ofSaudi Arabia and was stored at 277 K until analysis. The NO3

�

concentration in each bottled water was labelled (<10 ng/mL)by the respective companies. Each water sample (20 mL) wastaken in capped conical flask and treated with 100 mg of De-Acidite FF-IP resin under optimum experimental conditions (pH:3, time—25 min temperature—318 K and speed of shaker—100 rpm) in a water bath shaker. After equilibration time, thewater samples were withdrawn from the shaker and filteredthrough 0.22 mm PVDF filter before being injected into UPLC–MSsystem. Blanks and quality controls were analyzed in everybatch to ensure contamination of the samples did not happenand sensitivity of the detection was constant during theanalysis.

3. Results and discussion

3.1. De-Acidite FF-IP resin characterization

Surface morphological studies of De-Acidite FF-IP resin werecarried before and after NO3

� adsorption. Micrographs showedspherical and smooth resin granules before NO3

� adsorption(Fig. 1a). However, after adsorption, a non-uniform multilayercovering over De-Acidite FF-IP resin surface was observed. This isdue to the adherence/binding of NO3

� ions over De-Acidite FF-IPresin surface (Fig. 1b). The elemental analysis revealed thepresence of appreciable amount of C, Cl, N and traces of O andAl on the virgin resin surface. It was noted that Cl elementdisappeared after NO3

� adsorption which revealed the occurrence

Fig. 1. SEM image of resin before (130� magnification) (a), after (160� magnificat

Please cite this article in press as: M. Naushad, et al., J. Ind. Eng. Ch

of ion-exchange process (Fig. 1c). It was also interesting to notehere that the weight percentage of N increased from 0.41% to44.45% after NO3

� adsorption confirmed the adherence of NO3�

ions over resin surface.The FT-IR spectra of De-Acidite FF-IP resin before and after

NO3� adsorption revealed a broad peak between 3200 and

3500 cm�1 corresponded to the presence of interstitial waterand hydroxyl groups [24] (Fig. 1d). A weak peak at 2920 cm�1 wasaroused due to –CH2 asymmetric stretching vibration of the methylgroup [25]. A sharp peak at around 1470 cm�1 was due to thestretching vibration of C–N [26]. After NO3

� adsorption, a newsharp peak was developed at 1380 cm�1 (circled) (Fig. 1d) whichwas a characteristic peak of NO3

� [25] confirmed the adherence ofNO3

� ions onto the resin surface.

3.2. Effect of pH

The pH of aqueous phase is an essential parameter to beoptimized during adsorption studies as it affects the degree ofadsorbate ionization and surface properties of adsorbent [27]. Inthis work, pH studies were carried out in pH range 2 to 10 byvarying the concentration of NO3

� solution from 100 to 300 mg/L(Fig. S1). The optimum adsorption on De-Acidite FF-IP resin forvarious NO3

� concentrations was observed at pH: 2. As seen fromchromatograms (Fig. 2a and b), 93% drop in relative intensity wasobserved after NO3

� adsorption at pH: 2. The adsorption of NO3�

was decreased slowly up to pH: 6 but a drastic decrease inadsorption was observed at higher pH (between 6 and 8). Athigher pH, the concentration of negatively charged hydroxyl ions(�OH) increased which competed with NO3

� ions to occupy De-Acidite FF-IP resin surface in turn decreased NO3

� ionsadsorption. Further increase in pH from 8 to 10 showed nosignificant change in adsorption. These results were in goodagreement with previously report on NO3

� ions adsorption onzinc chloride modified granular activated carbon with lignite as aprecursor material [13].

ion) (b) NO3� adsorption, EDX plot of resin (c), and FT-IR spectra of resin (d).

em. (2014), http://dx.doi.org/10.1016/j.jiec.2013.12.026

Time (min)

SIR of 1 Channel ES-TIC (Nitrate)

Intensit y: 6.84e7

0 1 20

1001.28

Inte

nsity

(%

)

01 20

100

1.28

Time (min)

SIR of 1 Channel ES -TIC (Nitrate)

Intensit y: 4.79e6

Inte

nsity

(%

)

01 20

100

1.28

Time (min)

SIR of 1 Channel ES-TIC (Nit rate )

Intensit y: 4.12e6

Inte

nsity

(%

)0

1 20

100

1.28

Time (min)

SIR of 1 Chann el ES-TIC (Nitr ate)

Intensity: 6.87e6

Inte

nsity

(%

)

(a)

(b) )d()c(

Fig. 2. UPLC–MS chromatograms of NO3� standard 100 mg/mL (a), time 25 min (b), pH: 2 (c), and temperature 318 K (d).

M. Naushad et al. / Journal of Industrial and Engineering Chemistry xxx (2014) xxx–xxx4

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JIEC-1756; No. of Pages 8

3.3. Effect of concentration, temperature and isotherm studies

The adsorption of NO3� on De-Acidite FF-IP resin was studied by

varying NO3� concentration from 50 to 300 mg/L and reaction

temperature from 293 to 323 K. As depicted from chromatogram(Fig. 2a and c), relative intensity dropped to 90% after NO3

�

adsorption at 318 K. The increase in NO3� adsorption on De-Acidite

FF-IP resin was observed with the increase in NO3� concentration

and reaction temperature (Fig. S2). This is due to the increase in thedriving force concentration gradient with the increase in adsorbateconcentration. Likewise, increase in reaction temperature provideda driving force to overcome mass transfer resistance betweensolid/solution interfaces in turn increased NO3

� adsorption onDe-Acidite FF-IP resin which indicated endothermic nature ofadsorption.

Non-linearized Langmuir, Freundlich, Redlich–Petersonand Koble–Corrigan models were applied to data. Langmuirmodel assumes that adsorption takes place at specific homoge-neous sites within the adsorbent. Langmuir model is given as[28]:

qe ¼qmKLCe

1 þ KLCe(2)

where Ce is the concentration of NO3� at equilibrium (mg/L); qe is

the adsorption capacity of NO3� on De-Acidite FF-IP resin at

equilibrium (mg/g); KL and qm are Langmuir constants related tocomplete monolayer coverage (mg/g) and affinity of the bindingsites and energy of adsorption (L/mg), respectively.

Table S3 shows the comparison of the maximum monolayeradsorption capacities of De-Acidite FF-IP resin with other resinsused by several workers [14–16,18,20,23] for the removal of NO3

�.

Please cite this article in press as: M. Naushad, et al., J. Ind. Eng. Ch

The essential feature of Langmuir isotherm can be expressed bya dimensionless constant termed as separation factor (RL), given as

RL ¼1

1 þ KLCo(3)

The values of separation factor reflect the nature of adsorptionprocess. The adsorption process is unfavorable if RL > 1, favorable ifRL is in between 0 and 1, linear if RL is 1 and irreversible if RL is 0.

Freundlich model assumes the occurrence of adsorption ontothe heterogeneous surface sites with exponential decrease inadsorption energy with adsorption sites saturation on adsorbent.Freundlich model is given as [29]:

qe ¼ KF � C1=ne (4)

where, KF [(mg/g) (L/mg)1/n] and n are Freundlich constants relatedto bonding energy and measure of deviation from linearity,respectively. If n = 1 (linear), n < 1 (chemical adsorption), n > 1(physical adsorption).

Redlich–Peterson (R–P), a hybrid model featuring both Lang-muir and Freundlich isotherms [30]. The R–P model has a lineardependence on the concentration in the numerator and anexponential function in the denominator to represent adsorptionequilibrium over a wide range of concentration. This model can beapplied in homogeneous or heterogeneous systems. Mathemati-cally, R–P model is expressed as:

qe ¼ACe

1 þ BCge

(5)

where, A (mg/g); B (mg/gg); are R–P constants and g is the isothermexponent. The value of g lies in between 0 and 1. If g = 1, Eq. (5)converts to the Langmuir form.

em. (2014), http://dx.doi.org/10.1016/j.jiec.2013.12.026

Ta

ble

1K

ine

tics

pa

ram

ete

rsfo

rN

O3�

ad

sorp

tio

no

nto

De

-Aci

dit

eFF

-IP

resi

n.

Co

(mg

/L)

qe,e

xp

(mg

/g)

Kin

eti

cm

od

els

Pse

ud

o-fi

rst-

ord

er

Pse

ud

o-s

eco

nd

-ord

er

Elo

vic

h

qe,t

he

o

(mg

/g)

k1

(1/m

in)

R2

SSE

x2q

e,t

he

o

(mg

/g)

k2

(g/m

g/m

in)

R2

SSE

x2q

e,t

he

o

(mg

/g)

A (mg

/g/m

in)

B (g/m

g)

R2

SSE

x2

10

01

8.9

61

8.9

50

.12

50

.99

74

0.5

82

0.0

57

17

.70

0.0

12

0.9

39

12

.42

30

.21

92

.40

81

.28

21

0.2

34

0.4

17

91

55

.83

67

.08

7

20

03

7.8

93

7.8

00

.10

10

.99

19

1.6

83

0.1

23

34

.79

0.0

05

0.9

24

81

1.9

74

0.4

95

2.0

51

1.7

85

11

.62

30

.41

71

68

9.9

23

48

.44

1

30

05

6.7

25

6.5

00

.09

30

.98

30

7.8

62

0.6

37

51

.74

0.0

03

0.9

19

22

8.7

75

0.7

47

6.8

98

0.3

62

32

.00

00

.40

45

12

29

.05

17

8.7

64

M. Naushad et al. / Journal of Industrial and Engineering Chemistry xxx (2014) xxx–xxx 5

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JIEC-1756; No. of Pages 8

Koble–Corrigan (K–C), an empirical three parameter model. It isa combination of the Langmuir and Freundlich isotherm models. Itis expressed as [31]:

qe ¼ACn

e

1 þ BCne

(6)

where, A, B and n are the K–C parameters.Microsoft Excel software was used to evaluate the non-linear

isotherm models. The optimization procedure requires an errorfunction to be defined in order to evaluate fit of a model toexperimental data. The residual or sum of square error (SSE) wasused as an error function to measure the goodness of fit which isdefined as:

SSE ¼Xn

i¼1

ðqe;cat � qe;expÞ2 (7)

To check out the accuracy of applied models Chi-square (x2) ofdetermination test was used as a statistical error function. It isexpressed as:

x2 ¼X ðqe;exp � qe;calÞ

2

qe;cal

(8)

where, qe,exp and qe,cal are the experimental and calculatedadsorption capacities at equilibrium, respectively. For best fittedmodel x2 value will be smaller.

Non-linear plots showed applicability of Freundlich model (Fig.S2). This was also confirmed by higher values of correlationcoefficient for Freundlich model (Table S4). Further, lower values ofx2, an error function also justified the applicability of modelrevealed that NO3

� adsorption on De-Acidite FF-IP resin occurredby exponential distribution of active sites on the heterogeneousresin surface exhibited multilayer adsorption properties whichwas in accordance with Freundlich energy hypothesis. The valuesof separation factor (RL) at various temperatures (293–323 K) werein between 0 and 1 confirmed the favorable adsorption process.The values of Freundlich constant n at various temperatures were>1 confirmed the physical nature of NO3

� adsorption onto the De-Acidite FF-IP resin. The values of g and n, R–P and K–C constant,respectively were too low to unity confirmed these models are toofar to approach Langmuir model.

3.4. Effect of contact time and kinetics studies

The efficiency of adsorption process was testified by kineticsstudies. The studies were carried out by varying the NO3

�

concentration from 100 to 300 mg/L. It was clear from chromato-gram (Fig. 2a and d) that the relative intensity decreased to 94% atequilibrium. The observed equilibration time for various NO3

�

concentrations was 25 min which showed that the adsorption ofNO3

� onto De-Acidite FF-IP resin was independent of initialconcentration of NO3

�. The adsorption took place in three phases.Initially, the adsorption was very fast which was due to theavailability of larger number of unsaturated adsorption sites (Fig.S5). It was slowed down in second phase due to the saturation ofactive sites over the adsorbent surface and finally equilibrium wasestablished in third phase. The equilibrium adsorption capacity (qe,mg/g) was increased from 18.96 to 56.72 mg/g with the increase ininitial NO3

� concentration (Co) from 100 to 300 mg/L.Pseudo-first-order kinetics, pseudo-second-order kinetics and

Elovich models in non-linearized forms were applied to thekinetics data. Pseudo-first-order model is given as [32]:

qt ¼ qeð1 � e�kk1 tÞ (9)

where, qt and qe are the adsorption capacities at time t andequilibrium, mg/g, respectively; k1 is pseudo-first-order rateconstant, 1/min.

Please cite this article in press as: M. Naushad, et al., J. Ind. Eng. Chem. (2014), http://dx.doi.org/10.1016/j.jiec.2013.12.026

M. Naushad et al. / Journal of Industrial and Engineering Chemistry xxx (2014) xxx–xxx6

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JIEC-1756; No. of Pages 8

Pseudo-second-order model is given as [33]:

qt ¼q2

e k2t

1 þ qek2t(10)

where, k2 is a pseudo-second-order rate constant, g/mg/min.Elovich model is given as [34]:

qt ¼1

AlnðBAÞ þ 1

BlnðtÞ (11)

where, A and B are Elovich constants.Results showed the applicability of pseudo-first-order kinetics

model as indicated by higher R2 values (Table 1) and non-linearplot (Fig. S5) at various NO3

� concentrations. Also, SSE and x2

values favored the applicability of pseudo-first-order kineticsmodel. The experimental, qe,exp. and theoretical, qe,theo adsorptioncapacities at equilibrium were in good agreement for pseudo-first-order kinetics model. It was also found that the rate constantdecreased with the increase in initial NO3

� concentration whichindicated slower adsorption rate at higher concentration.

3.5. Thermodynamics studies

Thermodynamics studies were carried out in the temperaturerange 293 to 323 K by varying initial NO3

� concentration from 50to 300 mg/L. Standard enthalpy change, DH8; standard entropychange, DS8; standard Gibb’s free energy change, DG8 wereevaluated.

Van’t Hoff plot (lnKc vs. 1/T) was used to calculate DH8 and DS8values is given as:

lnKc ¼DS�

R�DH�

RT(12)

where, universal gas constant, R (J/mol K); temperature, T (K);equilibrium constant, Kc.

The equilibrium constant, Kc is given as

Kc ¼CAe

Ce(13)

Gibb’s free energy, DG8, was calculated as

DG� ¼ �RT lnKc (14)

It is clear from Table 2 that the values of DH8 were positivewhich indicating endothermic process and the values of DS8 werepositive which illustrating that NO3

� adsorption caused disorder-ness in the system. The value of DG8 indicating the degree ofspontaneity of the adsorption process and a more negative valueshowed an adsorption process which was favorable energetically.The increase in DG8 with increasing temperature showed that theadsorption was more favorable at high temperature.

3.6. Breakthrough studies

Breakthrough studies were carried out in Milli-Q and tap watersince industrial, agricultural and domestic wastewater discharges

Table 2Thermodynamics parameters for NO3

� adsorption onto De-Acidite FF-IP resin.

Co (mg/L) Thermodynamics parameters

DS8 (J/mol K) DH8 (kJ/mol)

50 131.19 34.68

100 121.16 31.83

150 107.49 27.88

200 101.27 26.15

250 110.00 28.91

300 105.27 27.45

Please cite this article in press as: M. Naushad, et al., J. Ind. Eng. Ch

contain Ca2+, Mg2+, HCO3-, SO4

2�, Cl� ions similar to the tap water[35]. The breakthrough and exhaustive capacities were calculatedby a plot of C/Co vs. volume of effluent (Fig. S6). Nitrate solution(1000 mL) of 100 mg/L initial concentration (Co) was passedthrough a column at 1 mL/min flow rate. It was observed that350 mL Milli-Q and 300 mL tap water was passed through thecolumns without detecting the traceable amount of NO3

� ions ineffluent. The breakthrough capacities with Milli-Q and tap waterwere 35 and 30 mg/g, respectively. While, exhaustive capacity was95 mg/g with both Milli-Q and tap water. The presence of counterions in tap water might be a possible reason for slight drop inbreakthrough capacity when using tap water as matrix.

3.7. Desorption studies

Batch mode desorption studies were carried out. De-Acidite FF-IP resin was first saturated with 50 mg/L NO3

� solution. To removeunadsorbed NO3

� traces, saturated De-Acidite FF-IP resin waswashed several times with demineralized water. It was thentreated with eluents (acids and base) of various concentrations toelute NO3

� ions. Results showed the increase in desorption from56% to 72% with the increase in HCl concentration from 0.1 to 5 Mwhile, 63% desorption was observed with 0.1 M H2SO4. OptimumNO3

� ions recovery (93%) was achieved when 0.1 M NaOH solutionwas used as eluent (Fig. S7), showed the occurrence of ion-exchange mechanism due to which NO3

� ions were exchanged byOH� ions.

3.8. Applications

The practical utility of De-Acidite FF-IP resin was testified byremoving NO3

� from commercially available bottled watersamples. Ten different brands (Mawared, Qassim, Safa, Hayat,Nova, Hana, Hail, Hada, Fayha and Berain) of locally availablebottled water were taken for the study. The bottled water source,NO3

� level claimed by company, NO3� level detected by UPLC–

MS before adsorption, and residual NO3� concentration in

bottled water samples after adsorption are tabulated (Table 3).It is evident from Table 3 that the NO3

� level in bottled watersamples was less than 10 mg/L before adsorption. But, after theadsorption process, the NO3

� was not found in Mawared, Novaand Safa bottled water samples while in rest of the studiedbottled water samples, the NO3

� level was found <LOD to <LOQ.Fig. 3 shows, as an example, the chromatograms obtained by theUPLC–MS method for Hayat and Nova bottled water before andafter adsorption. It is apparent from figure that before adsorptionNO3

� peak was appeared at 1.28 min form both water samples.After the adsorption process, the NO3

� peak was completelydiminished at the retention time of 1.28 min for Nova. However,for Hayat water sample the NO3

� peak appeared at the sameretention time but not quantified due to low signal-to-noise ratio(10:1). No interference before and after NO3

� adsorption was

�DG8 (J/mol)

293 K 303 K 313 K 323 K

3862.6 4572.3 7069.4 7389.0

3777.3 4409.4 6731.3 7030.0

3532.2 4573.0 6285.8 6510.4

3532.2 4291.5 6020.7 6313.0

3316.6 4177.3 6020.7 6346.9

3377.0 4272.2 5957.8 6301.7

em. (2014), http://dx.doi.org/10.1016/j.jiec.2013.12.026

Time (min)

SIR of 1 Chann el ES-TIC (N itrate)

Inte nsit y: 4.45 e6

0 1 20

1001.28

Inte

nsity

(%

)

Hayat (Before adsorptio n)

Time (min)

SIR of 1 Chann el ES-TIC (N itrate)

Inte nsit y: 1.35 e6

0 1 20

1001.28

Inte

nsity

(%

)

Nova (Before ad sorptio n)

Time (min)

SIR of 1 Chann el ES-TIC (N itrate)

Inte nsit y: 2.45 e5

0 1 20

1001.28

Inte

nsity

(%

)

Hayat (Afte r adsorpti on)

Time (min)

SIR of 1 Chann el ES-TIC (N itrate)

0 1 20

100

Inte

nsity

(%

)

Nova (After ad sorptio n)

Fig. 3. UPLC–MS chromatograms of NO3� in drinking water (Hayat and Nova) before and after adsorption onto De-Acidite FF-IP resin.

Table 3Nitrate adsorption from bottled drinking water onto De-Acidite FF-IP resin.

Commercial bottled water* Water source NO3� level claimed

in the label (mg/L)

NO3� level before adsorption

(mg/L � SD) [1]

NO3� level after

adsorption (mg/L)

Mawared Well water 2.00 2.14 � 0.02 nd

Qassim – <10 4.21 � 0.01 <LOQ

Safa – 1.00 1.44 � 0.03 nd

Hayat Well water 6.00 6.49 � 0.01 <LOQ

Nova Well water 3.08 1.93 � 0.02 nd

Hana Well water 3.00 3.00 � 0.01 <LOD

Hail Well water 7.90 2.83 � 0.02 <LOD

Hada – 5.00 4.82 � 0.01 <LOQ

Fayha Well water 4.00 3.74 � 0.02 <LOQ

Berain – 4.00 4.15 � 0.01 <LOQ

* Sterilized by ozone; –not defined; SD = standard deviation (n = 3); nd = not detected.

<LOQ = below limit of quantification; <LOD = below limit of detection.

M. Naushad et al. / Journal of Industrial and Engineering Chemistry xxx (2014) xxx–xxx 7

G Model

JIEC-1756; No. of Pages 8

observed in chromatogram as no detectable matrix peak waseluted in the retention time of the targeted analyte.

4. Conclusions

The toxicological effects of NO3� are well-known therefore,

it is essential to remove or minimize it to permissible limitsin municipal and drinking water supplies. In this research,we have tested fate of De-Acidite FF-IP anion exchange resinfor adsorptive removal of NO3

� removal from synthetic andcommercially available bottled water samples. The morphological,

Please cite this article in press as: M. Naushad, et al., J. Ind. Eng. Ch

elemental and spectroscopic analysis revealed binding of NO3� on

resin surface confirming occurrence of NO3� adsorption. Break-

through studies showed effectiveness of resin in both Milli-Q andtap water without much interference of counter ions usuallypresent in tap water matrix while, optimum NO3

� recovery (93%)was observed with 0.1 M NaOH. The application of resin wasestablished for NO3

� removal from ten commercially availablebottled water samples. The resin treated water samples showedNO3

-level from not detected to below of quantification. Thus, De-Acidite FF-IP resin could be aid for NO3

� removal form bottledwater.

em. (2014), http://dx.doi.org/10.1016/j.jiec.2013.12.026

M. Naushad et al. / Journal of Industrial and Engineering Chemistry xxx (2014) xxx–xxx8

G Model

JIEC-1756; No. of Pages 8

Acknowledgement

The authors extend their appreciation to the Deanship ofScientific Research at King Saud University for funding the workthrough the research group project No. RGP-VPP-043.

Appendix A. Supplementary data

Supplementary material related to this article can be found, in the

online version, at doi:10.1016/j.jiec.2013.12.026.

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