2,4-Dinitrophenol의 흡착거동에 관한 연구

김 태 영, 조 형 열, 이 대 로, 김 숙 진, *양 재 호, 김 승 재, 조 성 용

전남대학교 환경공학과, *화학공학과

A Study on Adsorption behavior of 2,4-dinitrophenol

T. Y. Kim, H. Y. Cho, D. R. Lee, S. J. Kim, J. H. Yang, S. J. Kim, S. Y. Cho

Dept. of Env. Eng., Chonnam Nat'l. Unv., Kwangju 500-757, Korea

*Dept. of Chem. Eng., Chonnam Nat'l. Unv., Kwangju 500-757, Korea

1. Introduction.

The present of phenol and phenolic compounds in water and wastewater has been of great public concern. Phenol is one of the most frequent contaminants at hazardous-waste site. 2,4-Dinitrophenols are a class of manufactured chemicals that do not occur naturally in the environment. 2,4-dinitrophenol is used in making dyes, wood preservatives, explosives, insect control substances, and other chemicals, and as a photographic developer. 2,4-Dinitrophenol enters the air, water, and soil during its manufacture and use. It may be formed from reaction of other chemicals in the air. It may also enter the environment through landfill and storage tank leaks, or accidental spills during manufacture or transport. As per the World Health Organization regulation, 0.002mg/L is the permissible limit for phenol concentration in portable water. Among the several currently known physical, chemical, and biological methods used for wasted water reuse, adsorption is a well known established and powerful technique for treating domestic and industrial effluent. Adsorption from solution of pollution by microporous carbons is of great interest, because the increasing need for efficient removal of organic and inorganic substances from water in the purification of industrial effluents. In this study, we have deal with the equilibrium studies, sorption dynamics, and adsorption columns for removal of 2,4-dinitrophenol from the aqueous phase.

2. Theory

The mathematical model of a dynamic-column adsorption process basically requires transient material balances. In this regard, both the adsorption equilibrium and kinetic aspects of the process must be accounted. The model adopted here utilizes the Sips isotherm equation and a linear driving force (LDF) rate model to simplify the diffusion mass transfer inside adsorbent particles. The LDF model is a lumped parameter model for particle adsorption. In packed bed, the main parameters of transport of adsorbates are axial dispersion coefficient and the fluid-to-particle mass transfer coefficient. Axial dispersion contributes to the broadening of the adsorption front due to flow in the void spaces between particles. Dispersion effect in the bed is expressed in terms of the following model.

[eqn: -D_L {partial^2 C_i}over{partialz^2} ~+~ {partialv` C_i}over{partialz} ~+~ {partialC_i}over{partialt} ~+~ {1 `-` epsilon_b}over{epsilon_b} {partialq_i}over{partialt} ~=~ 0]

[eqn: C_i `(z,t=0)`=`0]

[eqn: D_L {partialC_i}over{partialz} right|_{z=0} ~=~ -v`({C_i `right|_{z=0^-}} ~-~ {C_i `right|_{z=0^+}})]

[eqn: partialC_i over partialz right|_z=L ~=~0]

Pore diffusion model

Based on the assumptions of a spherical particle, dilute solution, and local equilibrium, the adsorbate mass transfer equations are as follows

3. Materials and methods.

The reagent was purchased first grade from Yakuri pure chemicals co. The concentration of 2,4-dinitrophenol was measured with a Shimadzu ultraviolet-visible spectrophotometer, model 1601 (double beam). The wavelength, corresponding to a maximum absorbance of 2,4-diｒitrophenol, was found to be 350nm with an accuracy of □0.3 nm. Granular activated carbon with a specific surface area of 1050m2/g (according to the manufacture, Calgon co, F400) was used in this study. The fraction used in this work passed through the 30 mesh sieve but was retained on the 40 mesh sieve.

4. Results and discussion.

The adsorption capacity depends on the property of the adsorbates, furthermore, it is also influenced by other factor such as pH of the solution to be treated and the amount of impurities contained in the solution. Therefore the effect of pH on adsorption amounts was carried out in a equilibrium adsorber. In general, the adsorption capacity was increased with decreasing pH. Equilibrium data for 2,4-dinitrophenol on GAC are shown in Fig. 1 for the range of about 4∼10 pH values. The adsorption amount greatly increased with decreasing solution pH. Fig. 2. represents the experimental and simulated data for 2,4-dinitrophenol on GAC in batch adsorber. The diffusion models show satisfactory prediction of concentration decay curves. The estimated values of kf , Dp and Ds are listed in Table 1. And compared with the film mass transfer coefficient, the effective diffusion coefficients are a very small. This presumes that the diffusion inside a particle is a rate-controlling step. Figs. 3 and ８ show that the breakthrough time was shorter when a higher flow rate was employed on fixed bed. Usually, the intraparticle diffusivity is believed to be independent of flow rate. However, the breakthrough curves were found to be steeper at higher flow rate as shown in Fig. 3. This phenomenon is attributed to external film mass transfer resistance. This resistance is smaller when flow rate is higher, so that the length of mass transfer zone (MTZ)  is reduced  and a sharper breakthrough curve is generated.

Table 1. Effective diffusion coefficients and film mass transfer coefficient

Adsorbate Species	pH	kf [m/s] x105	Dp [m/s2] x 1010	Ds [m/s2] x 1014
DNP	2.25 4.3 6.0 10	3.95 4.29 2.79 2.51	119.2 74.85 3.93 4.36	415.7 47.92 2.82 4.50

5. Reference

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Yoshihide Kawamura, et. al., Ind. Eng. Chem. Res., 32, 386 (1993)

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Moon, H. and Tien, C., Chem. Eng. Sci., 43, 1269 (1988)

D.M. Clark and A.F. Smith, □Principles of adsorption and adsorption processes□ New York (1984)