Adsorption of 2,4-Xylidine on Granulated Activated Carbon in a Packed Bed Absorber. f f

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1 Proceedings o the 6 th Nordic Syposiu on Petrophysics, 5-6 May, Trondhei, Norway Nordic Energy Research Prograe Norwegian U. o Science and Technology Adsorption o,4-xylidine on Granulated Activated Carbon in a Packed Bed Absorber J. Reinik, J. Kallas Departent o Cheical Engineering, Tallinn Technical University, Ehitajate Str. 5, Tallinn EE-986, jreinik@hot.ee; Departent o Cheical Technology, Lappeenranta University o Technology, P.O. Box, Lappeenranta, FIN-5385, jkallas@lut.i. Introduction A reoval o carcinogenic,4-xylidine ro aueous solution using packed bed adsorber was carried out. The coponent has been detected in the groundwater o the abandoned Soviet issile bases in Eastern Europe. The pollutant originates ro the Xylidine-based issile uel, SAMIN. The purpose o the work was to predict, in the irst approxiation, the breakthrough proiles o Xylidine in the packed bed adsorber. The concentration liit or aroatic aines (both aniline and xlidine) in groundwater is. µ according to Estonian legislation. [] So the groundwater ust be puriied below that level. Experients with photocatalytical oxidation shows good puriication eectiveness, [] but the process is tie consuing. Attept to treat the groundwater with the distillation ethod is econoically not easible. [3] Thereore it was decided to investigate another way to treat the groundwater the granulated activated carbon (GAC) adsorption in packed-bed reactor. The design o packed bed adsorber involves ainly the calculation o the breakthrough curve. This reuires availability o the adsorption isothers and the solid phase diusivity. In order to calculate the breakthrough curve o the adsorption, the adsorption euilibriu and kinetic experients were carried out. Distilled water was used as a solute and NORIT RB granulated activated carbon was used as an absorbent.. Adsorption Euilibriu The design o packed bed adsorber involves ainly the calculation o the breakthrough curve. This reuires availability o the adsorption isothers and the solid phase diusivity. Traditional adsorption euilibriu isothers o Languir and Freundlich as well as linear isother were used or itting the experiental data. =, ax n = K c and = Kc [] The adsorption experients were carried out or the coponent xylidine, with dierent initial concentrations ( to 3 ), in -l lasks at the teperature 7 o C, with an euilibriu tie o 48 hours. The TEA is an easily evaporating copound and was not included in the adsorption experients. The dosage o GAC in the lasks varied between The solutions were properly ixed. Water analysis was carried out with a Hewlett-Packard 845A Diode-Array Spectrophotoeter. Euilibriu isothers had the sae constants at given teperatures.

2 Reinik et al., Adsorption o,4-xylidine on Granulated Activated Carbon in a Packed Bed Absorber , g/g. Languir Exp. Freundlich Figure. Coparison o,4-xylidine euilibriu data to Languir and Freundlich isother euations (T=7 o C). Table. Constants or adsorption isothers obtained ro euilibriu data. Isother Isother euation R Languir.45c.45c [ g/g] = =. ax Freundlich /n. [ ] g/g K c = 77.4c.7944 =.949 The euilibriu isother is presented in Figure, and the values o the Languir and Freundlich isothers are presented in Table. The Freundlich isother describes the euilibriu situation better than the Languir isother. 3. Adsorption in the Particle For a well-stirred batch reactor where external ass transer is relatively ast, the governing euation or adsorption can be described by the ollowing ass balance euation: [4] δ = Ds δt r δ r δr δ δr where r is the radial position, D s is the solid phase diusion coeicient and t is tie. In order to solve euation () Crank s ethod [5] was used in this work, assuing that the concentration o the solute at the surace reains constant ( ininite bath ) and the external il resistance is negligible. For sall ties, the euation to deterine D s ay be written as: _ / [ B] [] Ds t = 6 π + [3] R / Proceedings o the 6 th Nordic Syposiu on Petrophysics 5-6 May, NTNU, Trondhei, Norway

3 Reinik et al., Adsorption o,4-xylidine on Granulated Activated Carbon in a Packed Bed Absorber 3 where is the average concentration in the solid at any given tie, is the average concentration in the solid at ininite tie, R is the particle radius and B is a constant. Thus, a plot o / versus the suare root o tie gives a straight line o slope 6(D s /πr ) /. The kinetic experients were carried out in a 6 3 vessel (diaeter.7 ) at the teperature 7 o C during our days. The reactor was properly ixed and saples were analysed with the Hewlett-Packard 845A Diode-Array Spectrophotoeter. The initial concentration o xylidine was 5 and GAC concentration was.67. The result o the kinetic run is shown in Figure. The solid phase diusion coeicient calculated by Crank s ethod [5] is D s = [ /s]. According to Verulen et al. [6] D s =.5 - /s and Huang et al. [7] D s =.3-3 /s. 4. Breakthrough Curves and Conclusion The isother paraeters and diusion coeicients obtained ro euilibriu and kinetic run were included in the breakthrough curve calculation odels o [8] and Thoas. [9] Values o the input paraeters are presented in Table. The breakthrough curves were calculated utilising Thoas and ethods, and proiles were copared with laboratory experiental curves. Breakthrough curve predictions showed a satisactory it in soe cases but ore advanced ethods should be used in order to predict the Xylidine containated groundwater breakthrough proiles in a packed bed adsorber. Dynaic experients were carried out with two separate Pharacia Biothech coluns (D = 6 and 6 ). The results o the dynaic runs with data itting are presented in igures 3 through 8.,75 / h / t,h / Figure. The,4-Xylidine kinetic run at a teperature o 7 o C. The plot o _ / versus the suare root o tie. Proceedings o the 6 th Nordic Syposiu on Petrophysics 5-6 May, NTNU, Trondhei, Norway

4 Reinik et al., Adsorption o,4-xylidine on Granulated Activated Carbon in a Packed Bed Absorber Thoas exp 5 exp Thoas tie, h tie, h Figure 3. Bed depth is.35, e=.44, u = 6.6 c/s Figure 4. Bed depth is.45, e=.36, u = 4.4 c/s g/ l 8 6 Thoas Experiental 5 Thoas Experiental tie, h 5 5 tie, h Figure 5. Bed depth is.3, e=. 46, u =.5 c/s Figure 6. Bed depth is.4, e=.44, u =.6 c/s Thoas Experiental 5 g/ l Experiental Thoas tie, h tie, h Figure 7. Bed depth is.8, e=.46, u = 4.4 c/s Figure 8. Bed depth is.38, e=.38, u =.4 c/s Proceedings o the 6 th Nordic Syposiu on Petrophysics 5-6 May, NTNU, Trondhei, Norway

5 Reinik et al., Adsorption o,4-xylidine on Granulated Activated Carbon in a Packed Bed Absorber 5 Table. Input paraeters or the Thoas and calculation ethods. Paraeter Unit Value Average linear isother constant (or the ethod), K [ 3 li / 3 solid] 9 (initial concentration 5 ) Maxiu adsorbable concentration on solid adsorbent (or [kg/ 3 ] 45 the Thoas ethod), ax Languir isother constant (or the Thoas ethod), b [ 3 /kg] 45 Solid phase diusion coeicient, [4] D s [ /s] Liuid phase diusion, [] D [ /s] Liuid phase viscosity, [] µ [Pa*s] Liuid density,? [kg/ 3 ] 988 Epty colun supericial velocity, u [/s] Initial concentration, c [kg/ 3 ].9.3 Height o the bed, L []..6 Void raction in the bed, e [ 3 l/ 3 bed].3.4 Reerences. Regulation no. 74 on coniring the liit concentrations o pollutants in surace and ground water, Estonian Governent, Krichevskaya, M.: Diploa Work, TTU, Reinik, J.: Presentation in Nordic Energy Foru,, Gothenburg, - June. 4. Do D.D.: Sorption Rate o Biodal Microporous Solids with an Irreversible Isother, Che. Eng. Sci., 44, No. 8, 989, pp Cooney, D. O.: Adsorption Design or Wastewater Treatent, CRC Press LLC, 999, p Perry, R. H., Chilton, C. H.: Cheical Engineers Handbook, 5 th Ed., McGraw-Hill Book Copany, New York, Huang, T. C., Li, K. Y.: Ion-Exchange Kinetics or Calciu Radiotracer in a Batch Syste, Ind. Eng. Che. Fund.,, No., 973, p , R.G.: Approxiate solutions or batch, packed bed tube, and radial low adsorbers Coparison with experients, Che. Eng. Sci., 37, 83, Thoas, H.: Heterogeneous Ion Exchange in a Flowing Syste, J. Aer. Che. Soc., 66, 944, pp Reid, R.C., J.M. Prausnitz,. Poling, B.E.: The Properties o Gases and Liuids, 4 th Ed., McGraw-Hill Book Copany, 986, p Keskinen, K. I, Aittaaa, J.: Flowbat General Flowsheet Progra, Neste, 997. Proceedings o the 6 th Nordic Syposiu on Petrophysics 5-6 May, NTNU, Trondhei, Norway