Isosteric Heat for Monolayer Adsorption Obtained from Two

for the RO equation could correspond to an unreal situation. LA011361A. 10.1021/la011361a. Published on Web 12/21/2001. Table 2. Absolute Average ...
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Langmuir 2002, 18, 570-570

Additions and Corrections Isosteric Heat for Monolayer Adsorption Obtained from Two-Dimensional Equations of State F. Cuadros,* A. Mulero, L. Morala, and V. Go´mez-Serrano Langmuir 2001, 17, 1576-1581. The equations of state of Cuadros-Mulero (CM) and Reddy-O’Shea (RO) for two-dimensional Lennard-Jones fluids have been used to reproduce available experimental data of isosteric heat of adsorption of simple fluids onto flat surfaces. Results indicate a good behavior of the CM expression and a less good agreement with respect to the RO expression. Unfortunately, the published results for the isosteric heat obtained from equation RO were not fully correct. In particular, the absolute average deviations (AADs) for equation RO shown in Table 2 are erroneous and must be changed by the revised values given in the new Table 2, with all the other data and results the same. Moreover, results displayed in Figures 1-4 for expression

RO were not correct. In any case, the main conclusion remains the same, i.e., equation CM is an excellent model with which to study the physisorption of simple gases onto flat surfaces, being simpler than others. Some remarks must been made in light of the correct results. First, as shown in the new Table 2, the AADs are of the same order for the two equations and for all the selected systems, and hence it is not true that model CM fits significantly better the experimental results. Second, the adequate Lennard-Jones parameter for the adsorbed systems seems to be the same for both equations, whereas in the paper we indicated that the adequate parameters for the RO equation could correspond to an unreal situation. LA011361A 10.1021/la011361a Published on Web 12/21/2001

Table 2. Absolute Average Deviations (in %) of the Values Derived from Equations RO and CM with Respect to Experimental Results adsorbate

adsorbent

T (K)

Ar Kr Xe CH4

Graphite P33(2700) Sterling-FT Grafoil graphite Grafoil

CO

Grafoil

C2H4

Grafoil (MAT)

84 104.49 195.5 84.5 92.5 84.5 119 84 79.3 120 112 108 105 98

σ2D (nm)

(/k)2D (K)

qst(F)0) (kJ/mol)

AAD (%) RO

AAD (%) CM

0.330 0.355 0.390 0.350

94 128 183 112

9.6 12.6 17.3 13.6 13.3

0.355

76

11.0

0.415

150

20.6

1.58 0.93 0.99 0.92 1.39 1.24 1.03 1.94 1.08 1.40 1.99 2.57 2.67 3.71

1.20 1.42 0.58 1.01 1.48 1.16 1.03 1.81 0.84 1.27 2.08 2.28 2.99 2.91

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