Comments on “Biosorption of nickel from aqueous solution onto Liagora viscida: Kinetics, isotherm, and thermodynamics”

Abstract

In 2020, Komarabathina and colleagues published the paper above (the original paper). They used the Liagora viscida‐based biosorbent for adsorbing nickel ions from water. Kinetics, isotherm, and thermodynamics are three important components for the correct description of an adsorption process. However, the authors of the original paper introduced several fundamental errors in these three parts. Other important problems in the original paper are inconsistencies between the experimental data and their modeling results, as well as errors in units. Therefore, we present detailed analyses of these mistakes, hoping that this “comment” paper will also be useful to other researchers (especially beginners) to avoid finding such mistakes elsewhere in the future.

Improper Estimation of Thermodynamic Parameters in Adsorption Studies with Distribution Coefficient KD (qe/Ce) or Freundlich Constant (KF): Considerations from the Derivation of Dimensionless Thermodynamic Equilibrium Constant and Suggestions

“…Therefore, it cannot be directly applied as the constant K o Eq for calculating the thermodynamic parameters. This problem has been intensively discussed in the literature [2,7,[18][19][20][21][84][85][86].…”

“…From Equation ( 43), the unit of the Freundlich constant K F that is (mol/kg)/(mol/L) n is correctly obtained in Equation (58). Some authors made a mistake in presenting the unit of K F as L/mol (or L/mg) or even mol/g (or mg/g [77,85]) without considering the magnitude of its exponent. This mistake has been discussed elsewhere [94,95].…”