nitrate

Catalytic Hydrogenation of Aqueous Phase NitrateOver Fe/C Catalysts

Anshu Shukla Æ Jayshri V. Pande Æ Amit Bansiwal ÆPetre Osiceanu Æ Rajesh B. Biniwale

Received: 17 December 2008 / Accepted: 6 February 2009 / Published online: 26 February 2009

� Springer Science+Business Media, LLC 2009

Abstract Catalytic hydrogenation of nitrate in water has

been carried out over Fe/C catalysts at ambient temperature

using batch and continuous reactors. In batch reaction

nitrate reduction activity of 2.9 mmol gmetal-1 min-1 with

nearly 100% selectivity towards nitrogen was obtained.

Column study shows nitrate reduction below 5 ppm for an

initial concentration of 100 ppm. Break through capacity, to

reach concentration of 45 mg L-1, is more than 530 bed

volumes. The catalysts were characterized using XRD,

SEM–EDAX and XPS. With high selectivity and activity

the catalytic system in present study could be a potential

option for nitrate removal from water.

Keywords Catalytic hydrogenation � Fe/C catalyst �Water treatment � Nitrate

1 Introduction

High level of nitrate concentration in surface run-off water

has ecological impacts resulting into eutrophication of water

bodies. Nitrates are inorganic pollutants, whose mobility

and stability make them highly dangerous in aerobic sys-

tems such as ground water [1]. High nitrate concentration

causes severe methemoglobinemia (7–27% of Hb) in all age

groups, especially in the age group of less than 1 year and

above 18 years [2]. The conversion of nitrate to nitrite in

digestive system leads to the formation of nitroso com-

pounds, which are potential carcinogens [3]. Several

methods reported for nitrate removal including physico-

chemical processes such as ion exchange, electrodialysis,

reverse osmosis, and microbiological denitrification; have

associated economical and ecological disadvantages [4].

Catalytic hydrogenation of nitrate is ecologically acceptable

solution as aqueous nitrate converts to harmless N2, unlike

adsorption or membrane processes. Further, there is no

sludge formation during catalytic hydrogenation. The

reduction of aqueous nitrate by using hydrogen or formic

acid as reducing agents over a solid catalyst offers an eco-

nomically advantageous alternative process to biological

treatments as a means of purifying drinking water streams

and industrial effluents [5, 6]. In this process, nitrates are

converted via intermediates to nitrogen in a single reactor

system and at near ambient conditions. Palladium based

bimetallic catalysts are most reported catalysts for aqueous

phase hydrogenation of nitrate. Cu and Sn have been

reported as promoters for enhancing the catalytic activity of

Pd [5, 7]. The commonly used supports for these metal

catalysts are alumina, silica, zirconia, titania, activated

carbon and niobia. Similarly unsupported zero valent iron

under acidic condition is found to be effective for nitrate

reduction [8–10]. However, as reported the rate of nitrate

reduction rapidly decreases as the oxidation state of zero

valent iron changes into Fe2? and Fe3? retarding the rate of

reaction [11]. Recently, several monometallic and bimetal-

lic catalysts supported on activated carbon have been

compared for reduction of nitrate and nitrite. Based on the

screening of several monometallic catalysts namely Pt, Pd,

Cu, Sn, Ru, Rh, Ni, Ir, Fe and Zn it is reported that Ru/C

exhibits considerable activity and Fe/C shows relatively low

activity for nitrate reduction. Whereas all other

A. Shukla � J. V. Pande � A. Bansiwal � R. B. Biniwale (&)

National Environmental Engineering Research Institute

(NEERI), CSIR, Nagpur 440020, India

e-mail: [email protected]; [email protected]

P. Osiceanu

Institute of Physical Chemistry, Romanian Academy of Science,

Ile Murgulescu, Spl. Independentei 202, 060021 Bucharest,

Romania

123

Catal Lett (2009) 131:451–457

DOI 10.1007/s10562-009-9899-9

monometallic catalysts supported on carbon are inactive for

nitrate reduction. Most of the catalysts for selective reduc-

tion of nitrate are bimetallic catalysts [12]. The present study

deals with preparation, characterization and evaluation of

monometallic Fe catalyst supported on activated carbon

(Fe/C) for selective reduction of nitrate in water. Although

relatively low activity of conversion of 3% is reported in the

literature results obtained in our present study exhibits rel-

atively better activities for nitrate reduction particularly

under the reaction conditions in this work.

2 Materials and Methods

2.1 Catalyst Preparation

Fe/C catalysts were prepared by adsorption method. Acti-

vated carbon granules (E-Merck Germany, size ca.

1.0 mm) with BET surface area of ca. 800 m2 g-1 were

used as support. The activated carbon granules were stirred

with solution of FeCl3 in acetone for 24 h and subsequently

filtered and dried in oven at 100 �C. The catalysts were

heated at 450 �C in nitrogen flow for 6 h to achieve loading

of metal on activated carbon by decomposition of metal

salt.

2.2 Catalyst Characterization

Powder X-ray diffraction pattern obtained did not show any

peak this may be attributed to high surface area and

amorphous nature of support the metal presence was

unidentified. The scanning electron microscopy–energy

dispersive X-ray analysis (SEM–EDXA) analysis con-

firmed the presence of metal over activated carbon. The

oxidation states of the surface iron were identified by X-ray

photoelectron spectroscopy (XPS) technique. XPS mea-

surements were performed on a Vacuum Generators VG-

ESCALAB 250 photoelectron spectrometer by using

monochromatic AlKa radiation (hm = 1,486.6 eV). The

pressure of the XPS analysis chamber during the mea-

surement was 8 9 10-9 Pa and the energy resolution

measured as FWHM of the Ag 3d5/2 peak was 0.5 eV. All

the spectra were corrected by subtracting a Shirley—type

background and the binding energies (BEs) were practi-

cally uncorrected as the carbon 1 s photoelectron line was

very close to the internal reference value of 284.6 eV.

2.3 Catalytic Hydrogenation

Catalysts were tested using batch and continuous reactors.

Details of batch reactor are shown in Fig. 1a. Batch

experiments were performed using a glass reactor equipped

with a magnetic stirrer, inlet for introducing H2/N2 mixture,

thermocouple for monitoring temperature and arrangement

for withdrawing samples.

The known amount of catalyst was taken in the reactor

containing 250 mL de-ionized water. The content of the

reactor was flushed with nitrogen flow for 45 min to remove

excess oxygen. Hydrogen was used as a reducing agent. The

flow rates of hydrogen and nitrogen were maintained at 25

and 50 mL min-1, respectively by mass flow controllers.

Nitrate solution (100 mL) with 350 ppm concentration has

been added to achieve the concentration in the reactor equal

to 100 ppm and total volume to 350 mL. The column tests

were performed using a glass column (10 mm diameter and,

50 mm length). The schematic diagram of column setup is

shown in Fig. 1b. The catalysts were packed upto 50 mm

height (catalyst weight of 1.68 g). The void volume in the

packed bed was estimated to be 0.125. A peristaltic pump

was used for feeding of nitrate solution in upflow mode. The

Peristalticpump

Nitratecontaminatedwater

Mass flow controller

H2 + N2

Treatedwater

Fe/AC Catalyst

Sampling Port

H2 +N2

Thermocouple

Diffuser

Hot Plate and Magnetic

Stirrer

Magnetic Stirring Bar

Funnel for feeding nitrate solution

(b)

(a)

Fig. 1 Experimental setup for the reaction a batch mode bcontinuous mode

452 A. Shukla et al.

123

co-current upward flow of hydrogen (diluted in N2) and

nitrate solution was provided to avoid flooding condition. In

a separate experiment, to detect the nitrogen in product gas,

feed of hydrogen diluted in helium was used. The product

gas analysis was carried out using TCD-GC (Shimadzu

2014, porapack Q column, 6 ft. length packed column).

Analysis of samples for concentration of nitrate was per-

formed using a Dionex model ICS-3000 ion chromatograph

equipped with Dionex Ionpac AG11-HC guard column and

AS11-HC separation columns, 25 lL sample loop and

conductivity detector. A 30 mM KOH was used as eluent at

flowrate of 1.0 mL min-1. Nitrite was also determined

using the same configuration. For analysis of ammonium in

selective samples, same system was used in combination

with AG5 and AS5 cation exchange guard and separation

column, respectively. A 6 mM methanosulphonic acid was

used as eluent for cation analysis. Hydroxylamine was

detected using a reported spectrophotometer method [13].

Wherein, a 1000 lg mL-1 hydroxylamine stock solution

was prepared by dissolving 0.2106 g of hydroxylamine

hydrochloride (E-Merck) in distilled water. A 0.047 mol

L-1 iodate solution was prepared by dissolving KIO3 (E-

Merck) in distilled water. Similarly, a solution of

3.46 9 10-4 mol L-1 neutral red was also prepared by

diluting 0.1 g of neutral red in 100 ml distilled water.

Sulfuric acid solution of concentration of 3.0 M was pre-

pared by diluting 1.64 mL of H2SO4 (98%, sp. gravity 1.84)

distilled water. An aliquot of 1.0 mL of sample was taken to

which 1.0 ml of iodate solution was added followed by

1.0 mL sulfuric acid solution; the mixture was allowed to

stand for 5 min at room temperature. Then 2 mL of neutral

red solution was added as an indicator and the change in

absorbance was monitored on spectrophotometer at 525 nm

for 0.5–5 min after the addition of neutral red.

3 Result and Discussion

3.1 Catalyst Characterization

Due to the amorphous nature of activated carbon and very

high surface area, powder X-ray diffraction pattern of Fe/C

catalyst does not show any intense peak, which can be

assigned to Fe. The presence of Fe metal over the surface of

catalyst was therefore, confirmed by SEM–EDXA method.

SEM micrograph and EDXA pattern for fresh catalyst are

shown in Fig. 2a, b, respectively. The EDXA result reveals

the presence of chloride, oxide, iron and carbon. For the

given area in the SEM, the atomic % of C, O, Fe, and Cl

were 84.33, 8.87, 1.45 and 3.63, respectively. This indicates

that the metal is well dispersed over the support [6].

Impurities of about 1.72% were observed assigning peaks to

Al and Si which was not expected in the sample.

The survey analysis during XPS confirms the elements

present on the surface as C, O, Fe and Cl only. The surface

elemental composition and the relative concentrations on

fresh catalyst are presented in Table 1. The high resolution

XPS spectrum of iron is shown in Fig. 3. It is well known

that XPS spectra of iron oxides exhibit a characteristic

shake-up satellite structures by accompanying the Fe

(2p3/2, 2p1/2) main peaks on their high binding energies

side. XPS measurements on a standard Fe(III) oxide, grade

99.9995 ? %, (Alfa Aesar) show a quite similar spectrum

in shape and binding energies as that recorded for catalyst

sample. In case of fresh catalysts, the binding energy of

about 711.0 eV for the most intense Fe 2p3/2 peak is

consistent with typical values for the ferric oxides (Fe

3 ? oxidation state) reported in the literature [14]. This

(a)

0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00

keV

001

0

80

160

240

320

400

480

560

640

720

800

Cou

nts

CK

aO

Ka FK

a

AlK

a SiK

a ClK

aC

lKb

FeL

l FeL

a

FeK

esc

FeK

a

FeK

b

(b)

Fig. 2 Characterization data for 5 wt% Fe/C catalyst a SEM bEDXA

Table 1 XPS analysis peak identification and estimated elemental

contents on surface of fresh catalyst

Photoelectron line Peak binding

energy (eV)

Element

concentration (at. %)

Fe2p3/2 711 1.65

O1 s 530 6.67

C1 s 284 88.89

Cl2p3/2 198 2.79

Nitrate Reduction Over Fe/C Catalysts 453

123

confirms that the iron is present in its 3 ? oxidation state

without any contribution from 2 ? oxidation state or ele-

mental Fe for the fresh catalyst sample. In the case of used

catalysts Fe 2p3/2 peaks at the Binding Energy values of

711.0 and 709.4 eV were observed indicating presence of

3 ? and 2 ? oxidation states of Fe on the surface. The

ratio Fe2? to Fe3? species was 1:2.7.

The presence of Cl segregated from the bulk to the top

monolayer is the main reason for observed lower percent-

age of Fe under 2% in comparison with the intended bulk

value of 5%. The presence of chlorine is due to FeCl3 salt

used for synthesis of catalysts. The XPS spectrum of

oxygen exhibits a ‘‘band-like’’ profile instead of the well

known sharp peak at around 530.5 eV characteristic to its

bonding in the ferric oxide as a result of some traces of OH

groups adsorbed and C=O bonds on the surface. The

apparent disagreement between the quantitative element

concentrations (at. %) determined by XPS and EDXA

originates in their different detected volume as the XPS is a

very surface sensitive method.

3.2 Effect of Metal Loading

Effects of variation of metal loading on activated carbon for

catalytic activity towards hydrogenation of nitrate were

conducted in batch experiments. The percentage loading of

Fe was varied as 2, 5, 10, and 20 wt% on activated carbon.

The catalyst dose was kept at 5 g L-1. The nitrate hydro-

genation batch reactions were conducted as described in

materials and methods section. In all these reactions pH was

observed in the range of 3.3–3.4. Flows of H2 and N2 were

maintained at 25 and 50 mL min-1, respectively. A blank

experiment was carried out in similar conditions with bare

activated carbon which shows reduction in nitrate concen-

tration from 100 to 84 ppm (i.e., 0.33 mmol g-1 of

activated carbon), which can be attributed to adsorption on

activated carbon. The net catalytic activity in all subsequent

experiment was estimated as difference between total

activities minus nitrate adsorption on activated carbon.

Blank experiment in the presence of only hydrogen was

conducted and no nitrate reduction was observed. Figure 4

depicts variation in catalytic activity with respect to dif-

ferent metal loadings. In case of 2 wt% Fe/C catalyst the

nitrate concentration reduced from 100 to 65 ppm (net

catalytic activity of nitrate reduction 1.95 mmol gme-

tal-1 min-1). Whereas at Fe loading of 5, 10 and 20 wt% the

final concentrations of nitrate in treated water at 60 min

from start of reaction were observed to be 48, 55, 57 ppm,

respectively. As listed in Table 2 corresponding catalytic

activity (net activity after deducting contribution by

adsorption on activated carbon) were 2.9, 2.8, and

1.2 mmol gmetal-1 min-1, respectively. The catalytic activity

has increased when Fe loading increased from 2 to 5 wt%

due to increase in number of active sites. At higher Fe

loadings, 10 and 20 wt%, probably the dispersion of cata-

lyst was relatively low and therefore activity of catalysts

was low. The optimal loading of Fe is therefore about

Fe 2p

2200

2300

2400

2500

2600

2700

2800

700710720730740

Cou

nts

/ s

Binding Energy (eV)

Fig. 3 The Fe 2p XPS spectrum for 5 wt % Fe/C fresh catalyst

0

0.5

1

1.5

2

2.5

3

3.5

0 10 20 30 40 50 60

Time (min)

Nitr

ate

conv

erte

d (m

mol

g-1

met

al m

in-1

)

2 wt% Fe/AC

5 wt% Fe/AC

10 wt% Fe/AC

20 wt% Fe/AC

Fig. 4 Variation in catalytic activity of Fe/C at different metal

loading

Table 2 Catalytic activity of various Fe/AC catalysts

Catalyst Conversion of

nitrate (%)

Catalytic activity

(mmol gmetal-1 min-1)

2 wt% Fe/AC 35 1.95

5 wt% Fe/AC 52 2.9

10 wt% Fe/AC 45 2.8

20 wt% Fe/AC 43 1.2


123

5 wt% and was used in further experiments. In a recent

study nitrate removal by zero valent iron [15] using CO2 as

a buffer (pressure of CO2 = 300 K Pa) at pH 5.7 with

catalyst dose of 33 g L-1 the nitrate removal of 85 wt% is

reported. Corresponding catalytic activity for nitrate

reduction in this report is 1.4 mmol gmetal-1 min-1. Whereas

in another study the catalytic conversion of 3% (in 5 h

period) of nitrate from initial concentration of 100 ppm in

volume of 800 mL with catalyst dose of 0.5 g L-1 over

1 wt% Fe/C has been reported [12]. This corresponds to

catalytic activity of 0.038 mmol gmetal-1 min-1 at pH of 5.5.

When compared with reported catalytic activity the catalyst

in present study exhibits better nitrate removal activity of

1.5 mmol gmetal-1 min-1 at pH of 5.0 and 2.95 mmol gme-

tal-1 min-1 at pH 3.3 over Fe/C. This indicates that Fe/C

catalyst, prepared in the present study, exhibits excellent

catalytic activity. In the case of Fe, oxidation states Fe3?

and Fe2? are easily interchangeable. A scheme of mecha-

nism of nitrate reduction is shown in Fig. 5. The Fe3? on the

catalysts surface may be changed to Fe2? by oxidation of H2

being bubbled into the reactor. Iron in Fe2? oxidation state

is known to act as reducing agent. This reduces the nitrate to

nitrogen and converts back to Fe3?. The XPS analysis

confirms the presence of only Fe3? species on the surface of

the fresh catalysts. XPS analysis of used catalyst exhibits

the presence of both Fe3? and Fe2? species. Therefore the

reduction of nitrate can be explained by above mechanism

involving reduction of Fe3? to Fe2? within reactor.

3.3 Effect of pH Variation

After adding catalyst (5 wt% Fe/C) to D.I. water the initial

pH was 3.3. Since the hydrogenation reaction for nitrate is

effective at lower pH, all the reactions were performed

under acidic conditions. Figure 6 depicts that at pH of 2.1

and 5.0 the nitrate was reduced from initial concentration

of 100 ppm to final concentration of 77 and 74 ppm (with

corresponding net catalytic activity of 1.2 and

1.5 mmol gmetal-1 min-1). The nitrate conversion at pH 3.3

was found to be 3.0 mmol gmetal-1 min-1 with concentration

reduction to 49 ppm. This indicates the optimal pH for

hydrogenation of nitrate in present system is 3.3.

3.4 Effect of Dose Variation

The dose of catalyst (5 wt% Fe/C) was varied as 1.0, 5.0

and 8.0 g L-1. With the dose of 1.0 g L-1 the nitrate

reduction was relatively low with final concentration of

treated water reducing to 87 ppm from initial concentration

of 100 ppm (catalytic activity 0.6 mmol gmetal-1 min-1).

Similarly, with dose of 5 and 8 g L-1 the nitrate converted

was almost same with final concentration in treated water as

48 and 47 ppm (catalytic activity 2.9 and 2.8 mmol gme-

tal-1 min-1), respectively. Therefore, a dose of 5.0 g L-1

was preferred for further studies.

3.5 Effect of Initial Concentration

The effect of initial concentration on the reaction was

studied using initial nitrate concentrations of 25, 50, 100,

150 ppm. Without adjustment, pH was observed to be 3.3

for all the reactions. At high initial concentrations the

reaction is spontaneous as compared to at lower concen-

trations. The nitrate reduction is therefore a surface

saturation phenomenon wherein with higher initial con-

centration the nitrate removal increases.

3.6 Effect of Hydrogen Flow Rate

The flow rate of hydrogen was varied as 10, 20 and

25 mL min-1 to study the effect on nitrate reduction. From

results obtained with hydrogen flow rate of 10 and

20 mL min-1, the nitrate conversion to final concentration

of 62.3 and 56.2 ppm (catalytic activity 2.0 and

2.5 mmol gmetal-1 min-1) was observed. With 25 mL min-1

the nitrate was effectively removed upto 48 ppm

(2.9 mmol gmetal-1 min-1).The results clearly show that there

is an effect of introducing hydrogen into the reaction media.

The nitrate reduction is directly proportional to hydrogen

flow rate. This can be attributed to efficient reduction of

ad3NO

2N

3Fe

2H

aq3NO

2Fe

Fig. 5 Mechanism of nitrate reduction

0

0.5

1

1.5

2

2.5

3

3.5

pH

Nitr

ate

conv

erte

d (m

mol

g-1

met

al.m

in-1

)

2.1 3.3 5.0

Fig. 6 Effect of pH on catalytic activity with 5 wt% Fe/C catalyst


123

Fe3? to elemental state in presence of excess H2 and

therefore better catalytic reduction of nitrate.

3.7 Kinetics of the Reaction

In order to study long-term catalytic activity a batch study

for 5 h was performed. A 350 mL nitrate solution of

100 ppm concentration was used with catalyst dose of

1.75 g L-1. From the observed phenomena, the catalytic

activity is relatively high in first 1 h and retards with

increase in time. The nitrate conversion after 1 h was

3.47 mmol gmetal-1 min-1. At the end of 5 h the same activity

of 3.47 mmol gmetal-1 min-1 was maintained with final con-

centration of nitrate as 41 ppm. The graph of natural log of

rate of nitrate reduction, ln (-rA) verses natural log of

concentration, ln (con) was plotted. The observed results

reveal that the reaction follows pseudo first order with rate

constant as 1.38 9 10-3 min-1 for nitrate reduction over

5 wt% Fe/C.

3.8 Column Studies

Nitrate solution with 100 pmm concentration was passed

through a packed column containing the 5 wt% Fe/C cata-

lyst (1.68 g) in up flow mode at the rate of 10 mL min-1.

The hydrogen and nitrogen flow rates were maintained as 3

and 6 mL min-1. The reduction in nitrate concentration

with respect to time is shown in Fig. 6. With catalyst bed

volume of 3.85 cm3, the breakthrough, reaching outlet

concentration to 45 mg L-1, was observed at 110 min,

which is equivalent to 490 bed volumes. The nitrate con-

version rate was observed as 0.077 mmol gmetal-1 min-1 at

107 min where concentration of nitrate was observed to be

35.8 ppm. The pH of outlet stream of water throughout the

reaction was constant around 3.0. The pH of treated water

was neutralized by addition of 0.1 N alkali solutions. The

bed was saturated after 220 min. The graph in Fig. 7 also

show the result for 7.7 cm3 of volume of packed column.

For which breakthrough was observed at 150 min, which is

equivalent to 530 bed volumes. The advantage of using

7.7 cm3 columns was that the nitrate concentration was

observed to be less than 5 ppm for first 100 min. The nitrate

conversion rate at 135 min was 0.037 mmol gmetal-1 min-1

with nitrate concentration for treated water as 3 ppm. The

bed was saturated after 255 min. From the results of column

study, it is evident that the nitrate reduction is more effec-

tive when volume of the reactor is 7.7 cm3. This is due to

increased contact time as compare to column of 3.85 cm3

bed volume.

As the system was assumed to be operated as plug flow

column and at steady state condition the following rate

equation has been used:

r ¼ Cin � C

hð1Þ

Where Cin, C is inlet and outlet concentration of nitrate

solution, and h is the hydraulic retention time (HRT). HRT

has been calculated taking into consideration the void vol-

ume of the catalyst bed. With column diameter 10-2 m and

length of 5 9 10-2 m, the rate was observed to be

3,462 mmol m-3 min-1 for HRT of 0.049 min (ca. 3 s).

Similarly, with column diameter of 10-2 m and length of

0.1 m the rate of nitrate removal was found to be

1,927 mmol m-3 min-1 for HRT of 0.083 min. The

observed trend is due to inverse relation between HRT and

rate of nitrate reduction. The empty bed contact time

(EBCT) for the column has been calculated as 0.33 min.

The concentration of nitrate in treated water is well below

WHO guidelines of 45 mg L-1. The pH of outlet water is

relatively low at 3.3–3.5. This indicates the need of a neu-

tralization step downstream to column. With pH

adjustment, a potential catalytic system for nitrate removal

is demonstrated in continuous mode.

3.9 Selectivity of Catalysts

In order to establish the selectivity of the catalysts for

reduction of nitrate to nitrogen product gas was analyzed in

a separate experiment wherein H2 and He mixture was used

as feed to the reactor instead of H2 and N2. The outlet gases

were monitored using GC-TCD, which confirms the pres-

ence of N2 in the outlet stream. During the reaction there

was formation of nitrite (partially reduced product) as an

intermediate only upto first 5 min of reaction during batch

reaction. However, there was no nitrite formation observed

during continuous mode reaction. No ammonium was

detected in the samples. Similarly, no nitrite was observed

after 5 min of reaction in batch reaction. There was no

0

20

40

60

80

100

120

0 50 100 150 200 250 300 350

Time (min)

Nitr

ate

conc

entr

atio

n (m

g L

-1)

Reactor with L = 4.9 cm(5 wt%Fe/AC )

Reactor with L = 10 cm(5 wt% Fe/AC)

Reactor with L = 4.9 cm(bare activated carbon)

Fig. 7 Break through curves for nitrate removal in continuous mode


123

formation of hydroxylamine as determined by spectropho-

tometric method described in experimental section. The

overall selectivity towards the nitrogen was nearly 100%.

3.10 Effect of Other Ions on Catalytic Activity

The presence of hydroxides and carbonates (0.01 M)

increases the pH (10.6 and 8.8, respectively) and force to

precipitate out the iron from the support. Therefore, the

catalyst was not found to be effective in presence of

hydroxides and carbonates. Further modification of the

catalysts, such as designing new stable catalyst using

mixed metal oxide as support, is under progress to over-

come this limitation.

4 Conclusions

Monometallic Fe/C catalyst has been developed for effec-

tive hydrogenation of nitrate. The catalyst in this study

exhibits considerable activity of 1.5 and 2.95 mmol gme-

tal-1 min-1 at pH of 5.0 and 3.3, respectively. The

selectivity towards the formation of nitrogen over Fe/C

catalysts is nearly 100%. There was no formation of nitrite,

ammonium or hydroxylamine. The main feature of this

work is selective reduction of nitrate on monometallic

catalysts.

Acknowledgments Authors would like to gratefully acknowledge

the financial support from Rajiv Gandhi National Drinking Water

Works Mission, Ministry of Rural Development, New Delhi. We also

acknowledge Dr. B. Sreedhar, scientist, Indian Institute of Chemical

Technology, Hyderabad for carrying out XPS analysis.

References

1. Pintar A, Batista J, Levee J, Kajiuchi T (1996) Appl Cat B:

Environ 11:81–98

2. Gupta SK, Gupta RC, Seth AK, Gupta AB, Bassin JK, Gupta A

(2000) Natl Med J India 13:58–61

3. Rocca CD, Belgiorno V, Meric S (2006) Desalination 204:46–62

4. Daub K, Emig G, Chollier M-J, Callant M, Dittmeyer R (2001)

Catal Today 67:257–272

5. Prusse U, Vorlop KD (2001) J Mol Catal A: Chem 173:313–328

6. Barrabe0s N, Just J, Dafinov A, Medina F, Fierro JLG, Sueiras JE,

Salagre P, Cesteros Y (2006) Appl Cat B: Environ 62:77–85

7. Daub K, Emig G, Chollier M-J, Callant M, Dittmeyer R (1999)

Chem Eng Sci 54:1577–1582

8. Cheng F, Muftikian R, Fernando Q, Korte N (1997) Chemosphere

35:2689–2695

9. Huang YH, Zhang TC (2004) Water Res 38:2631–2642

10. Chen YM, Li CW, Chen SS (2005) Chemosphere 59:753–759

11. Huang YH, Zhang TC, Shea PJ, Comfort SD (2003) J Environ

Qual 32:1306–1315

12. Soares OSGP, Orfao JJM, Pereira MFR (2008) Catal Lett

126:253–260

13. Afkhami A, Madrakian T, Maleki A (2006) Anal Sci 22:329–331

14. Fuji T, Groot FM, Sawatzky GA, Voogts FC, Hibma T, Okada K

(1999) Phys Rev B 59:3195–3202

15. Li CW, Chen YM, Yen WS Chemosphere 68:310–316


123

nitrate

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