Purification Of Aniline And Nitro Substituted Aniline -Books Download

PURIFICATION OF ANILINE AND NITRO SUBSTITUTED ANILINE

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PURIFICATION OF ANILINE AND NITRO-SUBSTITUTED ANILINE CONTAMINANTS FROM AQUEOUS SOLUTION USING BETA ZEOLITE 1Talib M. Albayati, 2Aidan M. Doyle 1University of Technology, Baghdad, IRAQ 2Manchester Metropolitan University, Manchester, UK Abstract. Aniline and 2-, 3- and 4-nitro substituted anilines were readily adsorbed



T M Albayati A M Doyle
Fig 1 Chemical structures of adsorbates a aniline b 2 nitroaniline
c 3 nitroaniline and d 4 nitroaniline
zeolite Fig 2 has been used to remove aniline from aqueous solution which was then
decomposed by heating in the presence of a copper catalyst O Brien et al 2004 2008
Aqueous solutions of 2 NA and 4 NA were purified by treatment with dealuminated
Faujasite zeolite Koubaissy et al 2011 We have recently reported the use of zeolite
ZSM 5 as an adsorbent of substituted aniline compounds Albayati Doyle 2013
Although each compound adsorbed on ZSM 5 the amount of material removed from
solution varied greatly between adsorbates due to their shape selective adsorption Here
we report the adsorption properties of aniline 2 NA 3 NA and 4 NA on Beta zeolite
Each molecule was successfully removed from solution using Beta zeolite while the
amounts adsorbed at low concentrations were due to differences in the adsorbates
affinity for the zeolite
Experimental
Adsorption isotherms were measured at room temperature by allowing Beta zeolite
Zeolyst Si Al 25 to reach equilibrium with each of the adsorbates over a range of
Purification of Aniline and Nitro Substituted
Fig 2 Schematic diagram of Beta zeolite viewed along 100 axis
initial solution concentrations Stock solutions of aniline 99 Fluka 2 NA 3 NA and
4 NA 99 Aldrich were first prepared by dissolving 0 2 g in 1 dm3 distilled water
which were then used to prepare solutions in the range 4 60 mg dm 3 for the adsorption
experiments 100 cm3 of solution was added to 0 01 g Beta zeolite in a glass beaker which
was stirred continuously for 1 hour at ambient temperature At the end of the adsorption
the solution was extracted from the suspension by centrifuge Hermle Z 200 A at 3500
rpm for 5 mins allowing for the analysis of solution by UV Visible spectroscopy HP
8453 at the following wavelengths 280 282 278 and 381 nm for aniline 2 NA 3 NA
and 4 NA respectively The masses adsorbed were calculated from the differences
between initial and final solution concentrations
Aniline 2 NA 3 NA and 4 NA loaded zeolite were isolated by centrifuge after
adsorption and then redispersed in 100 cm3 of deionised water to determine whether
desorption occurs The suspension was stirred for 1 hour at room temperature and the
solution was extracted and analysed identically to that described above for the adsorption
experiments The extent of desorption was calculated by expressing the amount of ad
T M Albayati A M Doyle
sorbate present in solution after desorption as a percentage of the amount of adsorbate
that was contained in Beta zeolite before desorption
Results and discussion
Equilibrium time
Initial experiments were conducted to determine the time period required to reach
equilibrium This was done by measuring the quantity adsorbed on Beta zeolite and
that remaining in solution as a function of adsorption time The results not shown
demonstrated that equilibrium was reached within ten minutes The actual time required
to reach equilibrium may be shorter in duration but an accurate determination of this
time period was not achievable using the method described here due to the five minutes
of centrifuge during which adsorption can still occur In any case an exact value of
equilibrium time is not needed only that the time period is exceeded during experiments
Therefore adsorption was allowed to proceed for 1 hr in all experiments
Adsorption isotherms
Fig 3 shows the adsorption isotherms of the four compounds where qe is the mass
of adsorbate adsorbed per gram of zeolite and Ce is the equilibrium concentration of
adsorbate in solution at equilibrium Overall each molecule was successfully adsorbed
over the full range of solution concentrations The profiles of the isotherms are consistent
with Type I Langmuir adsorption Brunauer et al 1940 for all four compounds the
amount adsorbed increased progressively until the adsorption isotherms reached values
in the range 80 100 mg g 1 These results agree very well with previous studies that show
aniline adsorption from aqueous solution corresponds to Type I Langmuir adsorption on
Beta zeolite O Brien et al 2004 2008
Fig 4 shows the Removal Eq 1 of each compound as a function of initial con
centration C0
Removal c0 cc x 100 1
For an initial concentration of 4 mg dm 3 approximately 70 of aniline and 3 NA
and 45 of 2 NA and 4 NA are removed from solution At higher concentrations the
Removal values decrease and become approximately similar for all four compounds
The decrease of Removal with increasing concentration is consistent with the use of
a fixed mass of zeolite which limits the amount of material that may be adsorbed from
solution as concentration progressively increases As the maximum uptake of the zeolite
pores is approached any further increase in concentration reduces the amount that may
adsorb into the pores which is recorded as a decrease in Removal
Purification of Aniline and Nitro Substituted
Fig 3 Adsorption isotherms on Beta zeolite u aniline 2 nitroaniline
p 3 nitroaniline l 4 nitroaniline
Fig 4 Removal on Beta zeolite u aniline 2 nitroaniline p 3 nitroaniline
l 4 nitroaniline
T M Albayati A M Doyle
The adsorption data were next tested to assess their fit to the Langmuir model in Eq
2 Langmuir 1918
Type 1 adsorption was confirmed by plotting the linear form of Eq 1 i e Ce qe vs
Ce which was used to calculate the Langmuir constants KL intercept AL from the
gradient AL KL and maximum uptake KL AL The Langmuir plots Fig 5 are all straight
lines confirming Type I adsorption for each of the 4 compounds with R2 values of 0 993
to 0 999 Table 1
Fig 5 Langmuir adsorption plots on Beta zeolite u aniline 2 nitroaniline p
3 nitroaniline l 4 nitroaniline
Aniline 2 NA and 3 NA have almost identical maximum uptake values of approx
imately 100 mg g 1 Table 1 which is close to the maximum uptake of approximately
110 mg g 1 reported for aniline on Beta zeolite O Brien et al 2008 A value of 144
mg g 1 is calculated for 4 NA inspection of the adsorption isotherms in Fig 3 suggests
that the true maximum uptake of 4 NA is more likely to be closer to those of the other
molecules The discrepancy may be a result of the maximum uptake KL AL being calcu
lated by extrapolation of results from the limited concentration range employed here
Purification of Aniline and Nitro Substituted
Table 1 Langmuir constants and adsorption properties of aniline
and substituted aniline compounds on zeolite Beta
Although the adsorption isotherms are Type I for all compounds studied here the
profiles in the lower concentration range 0 30 mg dm 3 diverge in two separate direc
tions aniline and 3 NA adsorb in much greater quantities than 2 NA and 4 NA This is
also evident from the differences in KL Table 1 where the values for aniline and 3 NA
are significantly higher 53 2 and 45 5 dm3 g 1 than 2 NA and 4 NA 11 4 and 7 24 dm3
g 1 The changes in the amounts adsorbed at low concentrations on Beta zeolite can be
explained by the pKa values of the adsorbates In solution it is easy to predict whether
a given molecule acts as an acid or base given its pKa value All four compounds used
in this study have pKa values Table 1 below the pH of deionised water 5 0 7 0 and
therefore exist in their non ionised form in free solution However it is their interaction
with Beta zeolite that is relevant to the adsorption reaction Unfortunately a universally
accepted scale of solid acidity directly comparable to pKa in aqueous solution is lacking
Therefore it is less straightforward to predict exactly how an alkaline molecule behaves in
contact with a solid acid than in solution Nonetheless knowledge about the strength and
number of acid sites on the zeolite surface makes it possible to explore this interaction
Zeolite acid strength is typically measured by the adsorption of a probe molecule and
subsequent analysis by UV Vis including Hammett method IR NMR and temperature
programmed desorption TPD Farneth Gorte 1995 Haw 2002 These techniques
have provided valuable information about the acid strength of zeolites that has contributed
to deducing the mechanisms of numerous solid acid catalysed reactions Experiments
on Beta zeolite show that it contains a mixture of strong and weak acid sites Smirniotis
Ruckenstein 1995 Camiloti 1999 Miyamoto et al 2000 For the results presented
here molecules with relatively high pKa values interact more readily with Beta zeolite
T M Albayati A M Doyle
which facilitates their adsorption The pKa values of aniline and 3 NA are 4 63 and 2 47
respectively which show increased adsorption at lower concentrations because of their
interaction with both weak and strong acid sites on the underlying zeolite In contrast
2 NA and 4 NA have lower pKa values 0 26 and 1 0 and are more likely to interact
with a relatively small number of strong acid sites only which reduces their adsorption
The adsorption of 2 NA and 4 NA on Beta zeolite is still a favourable exothermic process
at low concentrations despite the lower pKa value As a result the adsorption reaction
continues to proceed albeit to a lower extent At adsorbate concentrations 30 mg dm 3
and above the increased presence of the molecules in solution becomes the dominant
driving force pushing the reaction towards adsorption The adsorption profiles of the
four compounds become more similar to each other at higher concentrations used in this
study The method described here of adsorbing molecules with different pKa values on
zeolites has further significance in that it could potentially be used to achieve a semi em
pirical measure of acid strength using only basic wet chemistry laboratory facilities
Desorption studies were conducted to confirm that the zeolite could be regenerated
by removal of the adsorbates It is important to confirm that desorption occurs if the
zeolite is to be reused The experiments showed that all four molecules were success
fully desorbed into deionised water with over 90 efficiency in a single cycle A more
in depth study could of course be conducted to explore desorption in more detail i e
effects of adsorbate loading solution concentration temperature etc but this is beyond
the scope of this paper
Conclusions
Aniline 2 NA 3 NA and 4 NA were readily adsorbed from aqueous solution us
ing Beta zeolite All four molecules obeyed Type I Langmuir adsorption which was
confirmed by linear analysis with R2 values of 0 993 or greater At low concentrations
aniline and 3 NA adsorbed in greater quantities than 2 NA and 4 NA due to their greater
interaction with Beta zeolite resulting from differences in pKa
Acknowledgements T M Albayati is grateful to the University of Technology
Iraq for allowing postdoctoral leave and to Manchester Metropolitan University for
financial support
REFERENCES
Albayati T M Doyle A M 2013 Shape selective adsorption of substituted aniline pollutants
from wastewater Adsorption Sci Technol 31 459 468
Bhunia F Saha N C Kaviraj A 2003 Effects of aniline an aromatic amine to some
freshwater organisms Ecotoxicology 12 397 403
Purification of Aniline and Nitro Substituted
Bibby A Mercier L 2003 Adsorption and separation of water soluble aromatic molecules
by cyclodextrin functionalised mesoporous silica Green Chem 5 15 19
Brunauer S Deming L S Deming W E Teller E 1940 On a theory of the van der Waals
adsorption of gases J Am Chem Soc 62 1723 1732
Camiloti A M Jahn S L Velasco N D Moura L F Cardoso D 1999 Acidity of Beta
zeolite determined by TPD of ammonia and ethylbenzene disproportionation Appl Catal
A Gen 182 107 113
Derylo Marczewska A Marczewski A W 2002 Effect of adsorbate structure on adsorption
from solutions Appl Surf Sci 196 264 272
El Safty S A Shahat A Ismael M 2012 Mesoporous aluminosilica monoliths for the
adsorptive removal of small organic pollutants J Hazard Mater 201 202 23 32
Farneth W E Gorte R J 1995 Methods for characterising zeolite acidity Chem Rev 95
Gautam S Kamble S P Sawant S B Pangarkar V G 2005 Photocatalytic degradation of
4 nitroaniline using solar and artificial UV radiation Chem Eng J 110 129 137
Haw J F 2002 Zeolite acid strength and reaction mechanisms in catalysis Phys Chem Chem
Phys 4 5431 5441
Judd S Jefferson B 2003 Membranes for industrial wastewater recovery and re use
Oxford Elsevier
Ko C H Fan C Chiang P N Chiang M K Wang M K Lin K C 2007 p nitrophenol
phenol and aniline sorption by organo clays J Hazard Mater 149 275 282
Koubaissy B Joly G Batonneau Gener I Magoux P 2011 Adsorptive removal of aro
matic compounds present in wastewater by using dealuminated Faujasite zeolite Ind Eng
Chem Res 50 5705 5713
Langmuir I 1918 The adsorption of gases on plane surfaces of glass mica and platinum J
Am Chem Soc 40 1361 1403
Lee D S Park K S Nam Y W Kim Y C Lee C H 1997 Hydrothermal decomposition
and oxidation of p nitroaniline in supercritical water J Hazard Mater 56 247 256
Li K Zheng Z Huang X Zhao G Feng J Zhang J 2009a Equilibrium kinetic and
thermodynamic studies on the adsorption of 2 nitroaniline on activated carbon prepared from
cotton stalk fibre J Hazard Mater 166 213 226
Li K Zheng Z Feng J Zhang J Luo X Zhao G Huang X 2009b Adsorption of
p nitroaniline from aqueous solution onto activated carbon fibre prepared from cotton stalk
J Hazard Mater 166 1180 1185
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as measured by temperature programmed desorption of ammonia Micropor Mesopor Mater
40 271 281
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copper exchanged ZSM 5 and unmodified H ZSM 5 Adsorption Sci Technol 22 743 754
O Brien J O Dwyer T F Curtin T 2008 A novel process for the removal of aniline from
wastewaters J Hazard Mater 159 476 482
T M Albayati A M Doyle
Qureshi A Verma V Kapley A Purohit H J 2007 Degradation of 4 nitroaniline by
Stenotrophomonas strain HPC 135 Intern Biodeterioration Biodegradation 60 215 218
Saupe A 1999 High rate biodegradation of 3 and 4 nitroaniline Chemosphere 39 2325 2346
Smirniotis P G Ruckenstein E 1995 Alkylation of benzene or toluene with MeOH or
C2H4 over ZSM 5 or Beta zeolite effect of the zeolite pore openings and of the hydrocarbons
involved on the mechanism of alkylation Ind Eng Chem Res 34 1517 1528
Sun J H Sun S P Fan M H 2007 A kinetic study on the degradation of p nitroaniline by
Fenton oxidation process J Hazard Mater 158 172 177
Wang C Lu G Tang Z Guo X 2008 Quantitative structure activity relationships for
joint toxicity of substituted phenols and anilines to Scenedesmus obliquus J Environ Sci
20 115 119
Weitkamp J 2000 Zeolites and catalysis Solid State Ionics 131 175 188
Williams M E Hestekin J A Smothers C N Bhattacharyya D 1999 Separation of
organic pollutants by reverse osmosis and nanofiltration membranes mathematical models
and experimental verification Ind Eng Chem Res 38 3683 3695
Zheng K Pan B C Zhang Q J 2007 Enhanced adsorption of p nitroaniline from water
by a carboxylated polymeric adsorbent Sep Purif Technol 57 250 256
Dr Talib M Albayati
Department of Chemical Engineerring
University of Technology
52 Alsinaa Str PO Box 35010
Baghdad Iraq
Dr Aidan M Doyle corresponding author
Division of Chemistry and Environmental Science
Manchester Metropolitan University
Chester Street
Manchester M1 5GD United Kingdom
E mail a m doyle mmu ac uk


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