The Micropore Volume Filling Theory (TVFM) was postulated by Dubinin-Radushkevich for adsorption from gas phase. This equation is based on the Polanyi’s potential theory of the adsorption. Detailed explanation of equations and references related to these theories (Polanyi and Dubinin-Radushkevich) can be found from fundamental text books and some papers written on adsorption and porosity (Gregg and Sing, 1967; Hobson, 1969; Dabrowski, 2001). The theory of Dubinin-Radushkevich is applied to adsorption data to find out adsorption mechanism. The theory also gives some parameters such as adsorption capacity and adsorption energy. In the following is one of the commonly used version of the equation in adsorption studies from aqueous solution (Fu et al. 2008);
where Thus, linear form of equation (1) is given as:
On the other hand, when the literature is taken into consideration, below versions can also be found as follows:
In the equations (2-4),
where In equation 2-4;
When the subtitle of Dubinin-Radushkevich isotherm of the paper reported by Igwe and Abia (2007) is examined, it appears that although the equation [Eq. (4) of Igwe and Abia (2007)] is correct, its linear form [Eq. (5) of Igwe and Abia (2007)] is not correct:
Correct version of the equation [Eq. (5) of Igwe and Abia (2007)] should have been written as follows:
Because of the error in the equation [Eq. (5) of Igwe
and Abia (2007)], the authors have drawn the plot of ln e instead of lnq versus _{e}e. Therefore, the calculations related to Dubinin-Radushkevich Equation
in the paper are not correct and the authors should re-calculate their values
by using general accepted and correct version of Dubinin-Radushkevich Equation (Eq.
(6) and (7) of this paper). Specifically, the authors should re-draw the
Figures 8 and 9, and, then, they should re-calculate the Dubinin-Radushkevich
parameters in Table 2. The units of Dubinin-Radushkevich parameters should also
be given in Table 2 by the authors.^{2}It is obvious that this error is caused by wrong citation. Igwe and Abia (2007) cited Horsfall et al. (2004)’s paper for Dubinin-Radushkevich Equation. When the Horsfall et al. (2004)’s paper is examined, their explanation related to linear form of Dubinin-Radushkevich Equation is also not correct:
It is very interesting to note that although Horsfall
et al. (2004) made a mistake in writing of Dubinin-Raduskevich Equation, their
figure (Figure 6 in the paper of Horsfall et al (2004)) seems true inasmuch as
they have a plot of ln ein their paper. However, they should also re-check their data for
accuracy.^{2 }Horsfall et al. (2004) cited Hasany and Chaudhary (1996) for Dubinin-Radushkevich equation. When Hasany and Chaudhary (1996)’s paper is examined, it is obvious that they correctly expressed the Dubinin-Radushkevich Equation as in the following:
DABROWSKI, A. Adsorption-from theory to practice. FU, L.; WANG, J.; LU, H.; SU, Y. and REN, A. Comment on “The removal of phenolic compounds from aqueous solutions by
organophilic bentonite”. GREGG, S.J. and SING, K.S.W. Adsorption, Surface Area and Porosity, Academic Press London and New York, 1967, p. 195-223. HASANY, S.M. and CHAUDHARY, M.H. Sorption Potential
of Haro River Sand for the Removal of Antimony from Acidic Aqueous Solution. HOBSON, J.P. Physical adsorption isotherms extending
from ultrahigh vacuum to vapor pressure. HORSFALL, M. Jnr.; SPIFF, A.I. and ABIA, A.A. Studies
on the influence of mercaptoacetic acid (MAA) modification of cassava ( IGWE, Jude C. and ABIA, Augustin A.
Equilibrium sorption isotherm studies of Cd(II), Pb(II) and Zn(II) ions
detoxification from waste water using unmodified and EDTA-modified maize husk. |

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