In my research, I performed batch adsorption experiments of methylene blue on activated carbons. We found the following results:
- Kinetic study showed that the adsorption system followed the pseudo-second-order kinetics model;
- The Freundlich isotherm fits better the experimental data;
the adsorption of methylene blue onto optimal activated carbon was a physisorption process in nature (Thermodynamic study)
Our understanding of adsorption kinetics is much less than theoretical description ofadsorption equilibrium becuse the kinetics depend on the road to equilibrium. In general, in a well stirred solution three steps can be considered with the adsorption process: (1) film or interparticle diffusion, (2) intraparticle diffusion in pores and (3) surface reactions. In most models only limiting situations that assume that one of these steps is rate controling are considered.
In a paper by Douven et al. (2015) three dimensionless numbers are identified that govern the overall adsorption–diffusion process. The standard models are found to be particular cases of the general adsorption–diffusion model for specific values of the dimensionless numbers.
Reviews that discuss the 1st and 2nd order kinetic equations are presented by Tan and Hameed (2017), Liu & Liu (2008) and Azizian (2004).
S. Douven, C. A. Paez and C. J. Gommes, J. Colloid Interface Sci., 2015, 448, 437–450.
Y. Liu and Y. J. Liu, Sep. Purif. Technol., 2008.61, 229–242.
K. L. Tan and B. H. Hameed, J. Taiwan Inst. Chem. Eng., 2017, 74, 25–48.S. Azizian, J. Colloid Interface Sci., 2004, 276, 47–52.
Dear.... you can used the methods of determining the order of reaction, is first or second...
If you plotted 1st kinetic equation and not given linear relation , you must exam the 2nd kinetic order...
Article Modelling heterogeneous phosphate sorption kinetics on iron ...
This one might be of interest.