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Applications and Misapplications of the Langmuir Equation to Soil Adsorption Phenomena
Author(s) -
Harter Robert D.,
Baker Dale E.
Publication year - 1977
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1977.03615995004100060012x
Subject(s) - adsorption , langmuir equation , ion , chemistry , langmuir adsorption model , langmuir , thermodynamics , curvilinear coordinates , constant (computer programming) , physics , organic chemistry , quantum mechanics , computer science , programming language
When the development of the Langmuir adsorption equation is critically examined, it is evident that the equation soil scientists have been using [ C/x/m = C/k + I/kb , where C is concentration of adsorbate, x/m is the amount adsorbed per unit weight adsorbent, k is the adsorption maximum, and b is a constant] is in the wrong form. This error is of no great importance when the equation is merely used to obtain a calculated adsorption maximum for comparison to other adsorbent properties. However, it does become important when attempts are made to understand adsorption dynamics and bonding strengths. The commonly reported curvilinear nature of the C/x/m vs. C plots is simply the result of not considering the effect of desorbed ions in the equilibrium solution, rather than being due to multiple adsorption mechanisms. When the equation is corrected by considering desorbed ions, the isotherm becomes linear. In addition, the constant, b , of the Langmuir equation is not simply related to the bonding energy of the adsorbed ion, but to the ratio of adsorbed and desorbed ion bonding energies.