Langmuirizotermák

Langmuirizotermák, often translated as Langmuir isotherms, are a fundamental concept in surface chemistry that describes the adsorption of gas molecules onto a solid surface at a constant temperature. Developed by Irving Langmuir in 1918, this model is based on several key assumptions. It assumes that the adsorption process is localized, meaning gas molecules only adsorb onto specific sites on the surface and do not move around. It also assumes that each adsorption site can only hold one molecule, and that the adsorption and desorption processes are in equilibrium. Furthermore, the model posits that the heat of adsorption is constant and independent of surface coverage, implying that all adsorption sites are energetically equivalent.

The Langmuir isotherm equation mathematically relates the amount of gas adsorbed to the pressure of the gas at a given temperature. It predicts that as pressure increases, the surface coverage will also increase until all available adsorption sites are occupied, at which point the surface becomes saturated. At low pressures, the adsorption is approximately proportional to the pressure. As pressure rises, the rate of adsorption slows down because fewer sites are available. The model is particularly useful for understanding chemisorption, where a chemical bond is formed between the adsorbate and the adsorbent. While a simplification of real-world adsorption phenomena, Langmuir isotherms provide a valuable theoretical framework for interpreting experimental data and understanding the behavior of gas-solid interactions. Deviations from the Langmuir isotherm are often observed and can indicate multilayer adsorption, heterogeneity of the surface, or interactions between adsorbed molecules.