570
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
ref 26 11 27 28 22 23 24
