Elimination of Phenol By Adsorption Onto Mineral

Available online at www.sciencedirect.com

Energy Procedia 18 (2012) 1254 – 1260

ELIMINATION OF PHENOL BY ADSORPTION ONTO MINERAL / POLYANILINE COMPOSITE SOLID SUPPORT F.BELAIB, A.H.MENIAI*, M. BENCHEIKH LEHOCINE. Laboratoire De L’ingénierie Des Procèdes D’environnement (LIPE) : Institut De Chimie Industrielle ; Université Mentouri de Constantine ; Algérie.

Abstract The present study deals with the elimination of phenol by adsorption onto polyaniline coated silica gel, from synthesized aqueous solutions. The silica gel was coated by the polyaniline, a conducting and an electroactive polymer in order to modify its surface structure to improve its adsorption capacity. The study was carried out batchwise and the effect of important operating parameters like the contacting time, the initial concentration, the temperature and the pH was also investigated. The obtained results showed that the polyaniline coating of the silica gel surface did in fact improve the adsorption capacity of phenol. Key words : Silica gel , polyaniline, composites, adsorption, phenol.

1. Introduction The water pollution is one of the major concern in term of environment and hence the quality of life. Among the various pollutants in industrial waste water effluents from different industries such as pharmaceutical, oil, paper and others, Phenol can be present at important concentrations and is regarded as among the most toxic compounds [1]. In fact its concentration in air, water or ground can vary from few ppm to 4g/l, in severe systematic pollution cases [2], whereas according to the E.P.A (Environmental protection Agency) regulations, the maximum allowed phenol concentration is 5 ppm ( 19 mg/m 3 ) [3]. Phenol can be a very harmful compound to living organisms even at very low concentrations. For instance, ingestion of phenol contamined water in human body may cause protein degeneration, erosion of tissues, paralysis of central nervous system, damages to the kidneys, the liver, pancreas, etc. [4]. Therefore one can see the necessity for removing phenol from industrial wastewaters where different techniques do exist one can cite biological degradation, chemical oxidation, liquid-liquid extraction and adsorption which is the main interest of the present study. The performance of this technique depends upon the adsorbent to be used, a fact which has motivated the test of different solid support such as silica gel coated with polymer such as polyaniline to * Corresponding author

1876-6102 © 2012 Published by Elsevier Ltd. Selection and/or peer review under responsibility of The TerraGreen Society. Open access under CC BY-NC-ND license. doi:10.1016/j.egypro.2012.05.141

F. Belaib et al. / Energy Procedia 18 (2012) 1254 – 1260

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remove an organic pollutant such as phenol, despite the fact that Polyaniline has been used for the coating of various solid supports for mainly removing heavy metal cations, since it is a conducting and an electroactive compound. 2. Experimental Commercial porous silica gel was supplied by PROLABO as spherical particles with diameters ranging from 63 to 200 um, specific area of 500 m2/g and a porous volume of 75 cm3 /g. Due to the presence of some trace impurities, mainly carbon and chlorine, a washing of the silica gel with hydrochloric acid, was required and followed by a rinsing in distilled water. The product was dried and stored in a desiccator, ready for further use. Aniline (C6H7N) was obtained from ACROS ORGANICS (France), 99.8% pure with a molecular weight of 93.13 and a specific gravity of 1.021 whereas Ammonium persulfate (NH4)2 S2O8 was supplied by LABOSI (France) with a molecular weight of 228.2 and Phenol C6H5OH an aromatic organic compound, by PROLABO, with a molecular weight of 94 g/l. Bidistilled water was prepared locally using a GFL 2001/4 distillation unit. 2.1. Experimental Procedure 2.2. Synthesis of silica – polyaniline support The chemical synthesis of the polyaniline used as the coating polymer was based on the chemical reaction as shown in Figure 1. It was directly performed on the silica particles by injecting freshly distilled aniline in sealed beaker containing Ammonium persulfate (NH4)2 S2O8 and silica gel. The mixture was continuously stirred at constant temperature of 25° C for 2 hours. The resulting product was filtrated and then washed with hydrochloric acid and then dried at 95°C producing a fine green powder. This confirmed the fact that polyaniline was the only organic conducting polymer which was stable enough in the air in the form of a green powder as presented in Figure 2. It can be seen that polyaniline acted as a binding agent for the silica particles. Therefore the preparation of the composite colloidal conducting polymer was achieved by means of an in situ deposition of a thin polyaniline film on the silica particles.

Fig 1: General scheme of the silica gel polyaniline composite.

2.3. Elemental analysis This analysis was made for samples consisting of polyaniline coated silica gel and of just polyaniline and the results are shown in the following table1: Table1: Elemental analysis Sample Silica gel Polyaniline

Carbone 0,106 23,958

Hydrogen 1,36 3,605

Nitrogen 0,46 5,03


1256 Si-polyanilin

9,18

2 ,08

2,27

When the rate of nitrogen present in the solid support, one can calculate the mass of polymer expressed in mg per gram of solid support as follows: ( mg/g = % Nsup. 1000% Npoly with Nsup and Npoly are the percentages of nitrogen in the support and in the polymer, respectively [6]. The value of expresses the mass of polymer adsorbed in mg for 1g of coated silica gel. Therefore the mass of adsorbed polymer A in mg for 1m2 of silica coated is given as follows: A= (mg/m2) = / Ssp with Sspe specific surface area of coated silica gel. The thickness of the adsorbed polymer layer can also be calculated from the following expression: H(A) = .100/Ssp Table 2: Specific surface area of silica gel/polyaniline and polyaniline. Bare silica gel (m2/g) Silica/ polyaniline (m2/g) 448,16

344,32

Polyaniline (m2/g) 46,89

2.4. Phenol elimination The adsorption of the phenol in aqueous solution onto the polyaniline coated silica gel was considered batchwise, investigating the effect of different parameters like the contacting time, the initial concentration, the pH, etc.

2.5. Preparation of the phenol solutions Aqueous phenol solutions of were prepared fixing the pH at 6. A mass of 0.1g of the solid support silica gel /polyaniline were mixed to in a beaker to a volume of 30ml of the prepared 400mg /l phenol solution at 25° C. The solid support and the liquid are separated by filtration and a sample of the filtrate was analyzed by means of U.V spectroscopic using a visible spectroscopic (Shimadzu160) with a wavelength of 269 nm. 3. Results and Discussion 3.1 Adsorption kinetics The adsorption process was a transfer of the pollutant from the liquid phase to the solid one. The contacting time between the two phases had an effect on the mass transfer rate and Figure 2 shows the kinetic of adsorption expressed in terms of the adsorbed phenol amount. A very rapid phase was exhibited at the beginning, followed by saturation after about just 30mn. The rapid phenol adsorption kinetic step can be explained by the porous structure of the solid support and the corresponding results are in agreement with the values reported in the literature [7], [8], [4]. In the next step, equilibrium was reached and hence it can be noted that the adsorption phenomena is mainly governed by these two steps. Therefore the polyaniline coating of the silica gel had in fact favorably induced a modification of its surface properties, improving the retention capacity.


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Q(mg phenol/g adsorbent)

1,0

0,8

0,6

Run Run Run Run

0,4

1 2 3 4

0,2

0,0 0

50

100

150

200

250

Contacting tim e(m in)

Figure 2: Effect of contacting time on adsorption of phénol by silica gel ccoated by polyaniline (Conditions : contacting times =240min,Co=400mg/l,pH=6,T=25±1°C,m=0,1g,v=30ml,V=600tr/min)

3.2. Effect of pH The elimination of Phenol by adsorption depends greatly on the pH. At a strongly acidic pH (pH=2), the support did not adsorb whereas at pH values of 4, 5 and 6, the adsorption rate increased reaching its maximum values. Therefore the considered adsorbent was suitable for the decontamination of the solution. 10

Q(mg phenol/g adsorbent)

1 ,0

Run 1 Run 2 Run 3

8 0 ,8

6 0 ,6

0 ,4 4

0 ,2 2 0 ,0 0 0

0

21

2

4

3

6

4

58

6

10

pH

Fig 3: Effect of pH on retention of phenol by silica gel coated by polyaniline (Conditions : contacting time =120min,Co=400mg/l,T=25±1°C,m= 0.1g,v=30ml,V=600tr/min)

3.3. Effect of the initial concentration


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In order to assess the effect of the initial concentration on the adsorption capacity of Phenol onto silica gel coated by the polyaniline, different concentrations of phenol ranging from 30 to 400mg/l, were tested. The results show that the coated solid support capacity for eliminating phenol increased with initial concentration phenol increase. R un R un R un R un R un R un

Q(mg de phénol /g d'adsorbant)

1 ,0

0 ,8

1 2 3 4 5 6

(C o = 3 0 m g /l) (C o = 6 0 m g /l) (C o = 1 2 0 m g /l) (C o = 2 0 0 m g /l) (C o = 3 0 0 m g /l) (C o = 4 0 0 m g /l)

0 ,6

0 ,4

0 ,2

0 ,0 0

20

40

60

80

100

120

T e m p s d e c o n ta c t(m in )

Figure 4 : Effect of concentration on the retention of phenol by silica gel coated by polyaniline (Conditions :contacting time =120min,pH=6,T=25±1°C,m=0,1g,v=30ml,V=600tr/min)

3.4. Effect of the temperature In order to study the effect of temperature on the adsorption capacity of phenol onto polyaniline coated silica gel, the temperatures of 30°C , 40°C and 60°C were considered. The results presented in Figure 5 shows that the kinetic process of adsorption of phenol is enhanced at low temperature, confirming the results reported in [7].

R un R un R un R un

Q(mg de phenol/g adsorbent)

1 ,0

1 2 3 4

(T = 2 5 ° C ) (T = 3 0 ° C ) (T = 4 0 ° C ) (T = 6 0 ° C )

0 ,8

0 ,6

0 ,4

0 ,2

0 ,0 0

20

40

60

80

100

120

C o n ta c tin g tim e (m in )

Figure 5: Effect of the temperature on retention of phenol onto silica gel coated by polyaniline (Conditions :contacting time =120 min, pH= 6,Co=400mg/l, m=0,1g,v=30ml,V=600tr/min)


3.5. Isotherm of adsorption The study of the adsorption isotherm was also considered according to the previous experimental procedure and with the following characteristics: The concentration of the aqueous solutions of phenol varied as 30, 60, 120, 200, 300 and 400 mg/ l The contacting time was fixed at 120 min. The PH = 6 ± 1 The curve of Figure 6 shows that the solid support presented a good affinity for phenol and the capacity of adsorption increased with the initial concentration.

Qe(mg de phenol/g adsorbent)

1 ,0

0 ,8

0 ,6

0 ,4

L e s v a le u rs e x p é rim e n ta le s

0 ,2

0 ,0 0

1 00

200

300

40 0

C e (m g d e p h e n o l/l)

Figure6 : Adsorption isotherm of phenol onto silica coated by polyaniline Conditions :contacting time=120min,pH=6,V=600tr/min,T=25°C)]

4. Conclusion The obtained results confirm that the silica gel coated with the polyaniline could in fact adsorb phenol in aqueous solutions. The performance of adsorption was affected by certain parameters such the initial concentration, the contacting time, the temperature and the pH. The obtained results show also that the adsorption onto materials like silica gel coated by polyaniline was efficient and proved to be a suitable method for the treatment of industrial effluents. Therefore basing on these results, it can be concluded that the silica gel coated with polyaniline provides a good adsorbent for the elimination of an organic pollutant like Phenol from aqueous solutions.

References [1] J .w .Patterson. « Wastwater Treatment technologie »Am Arbor Science Pub .Inc, U.S.A.,199-215(1985) [2] R.G .Bond, C.P .Straub “Handbook of Environmental Control “Vol .IV, CRC .Press.USA(1974) [3] E.L Barkeer, E.B.Peter .F.Petricia,S.K.Grant “Phenol poisoning due to contaminated drinking Water” arch .Env.Health.Vol 33.89-94(1978)

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[4] R.Quadeer,a.h.Rehan ,”A study of the adsorption of phenol by activated carbon from aqueous solutions “ Turk .J .Chem .Vol 26 .357-361(2002 ) [5] F.belaib ,”Etude expérimentale de l’effet de l’enrobage de supports osolides par des polymères conducteurs sur leur retention de cations métalliques en solution aqueuse 0.Application à la silice et à certains matériaux naturels .Thèse de doctorat en Sciences .Université de Mntouri .Constantine .(2006) [6] M.Ghoul « Silice polyethyleneinine modifiés,élaboration ,caractérisation et applicaton à la dépollution métallique dans les eaux »Thèse de doctorat .Université des sciences et technologie de lille (2003) [7] H.Hadjar,Elaboration et caractérisation de matériaux composites minéraux à base d’un kieselguhr et d’un produit carbone .Application à la retention du plomb et du phénol » Mémoire de Magister .Univerité des Scizences et de la Technologie .Houari Boumediene .U.S.T.H.B.Alger(2003) [8] E.Gaillez-Degremont .Thèse de doctorat .Université des sciences de Technologie de Lille (1996)