Analytical modeling of adsorption isotherms for pristine and functionalized carbon nanotubes as gas sensors

The modeling of experimental data for adsorption is a very important means of predicting the mechanism of various adsorption systems. The experimental data for variation of conductivity of pristine and SnO2 functionalized single walled carbon nanotubes with concentration of nitrogen dioxide and ammonia gases (2 ppm-20 ppm) has been correlated with theoretical isotherm models. Studies are done with a one parameter model: Henry's isotherm and two parameter models: Langmuir isotherm, Freundlich isotherm and Temkin models. Regression analysis is used to see the compatibility of theoretical models with the experimental data. The Freundlich isotherm shows the maximum compatibility with the experimental results with maximum value of regression coefficient and minimum value of average relative error suggesting the heterogenous nature of the surface. The calculated values of different constants for the four models indicate the increased adsorption capacity in case of functionalized single walled carbon nanotubes. This may be attributed to increase in heterogeneity and enhanced surface area.

Automated summary

The modeling of experimental data is important for predicting the mechanism of adsorption systems. Experimental data of pristine and SnO2 functionalized single walled carbon nanotubes with nitrogen dioxide and ammonia gases at varying concentrations were compared with theoretical isotherm models. The Freundlich isotherm showed the best compatibility with the experimental results, indicating the heterogeneous nature of the surface. The calculated constants for the models suggested an increased adsorption capacity in the case of functionalized single walled carbon nanotubes, likely due to increased heterogeneity and enhanced surface area.