Use and Misuse of Sorption Kinetic Data: A Common Mistake that Should be Avoided

Numerical simulation of sorption dynamics showed that the use of data recorded at (or very close to) equilibrium in the search for the kinetic equation that best describes the process frequently leads to incorrect conclusions. Notably, it has been demonstrated that the fit of the adsorption data at equilibrium (t/q(t) versus t) is a straight line irrespective of the sorption kinetics. In order to distinguish pseudo-first-order from pseudo-second-order sorption kinetics, the data near the equilibrium should be omitted from the least-squares fit and the result confirmed by a different method. A straightforward method based on Delta(q(t)/q(e))/Delta t versus 1 - q(t)/q(e) and versus (1 - q(t)/q(e))(2) plots is suggested. Some recent papers reporting incorrect sorption kinetic analyses are discussed.