Modeling and optimization of reactive extraction equilibria and kinetic study of gallic acid using tributyl phosphate in isoamyl alcohol

ABSTRACT

Equilibrium and kinetic experiments were performed for gallic acid recovery using tributyl phosphate dissolved in isoamyl alcohol as a diluent. Employing an extractive-reaction system results in significantly higher acid recovery in comparison to physical extraction. Overall equilibrium extraction complexation constant K_E was found to be in the range 4.325–6.896. 1:1 acid: extractant complexes are proposed from the results obtained from mass action law model. Adsorption isotherm models (Langmuir, Freundlich, Temkin) and Response Surface Methodology was used, Mass transfer coefficient (k_L) and diffusivity coefficient were also calculated. Extraction kinetics was observed to be very slow based on the Hatta number.

KEYWORDS:

• Gallic acid
• tributyl phosphate
• isoamyl alcohol
• reactive extraction

Conflict of interest

The authors have declared no conflict of interest.

Abbreviations

TBP Tributyl phosphate

Symbols Used

[HA]₀ [kmol.m⁻³] Initial Gallic acid concentration

[HA]_org [kmol.m⁻³] Equilibrium Gallic acid in organic phase

[HA]_aq [kmol.m⁻³] Equilibrium Gallic acid in aqueous phase

K_{HA -} ionization constant

P Partition Coefficient

D [m³.kmol⁻¹] Dimerization Coefficient

K_D-Distribution Coefficient

Ha - Hatta Number

D_HC [m²s⁻¹] Diffusivity

k_L physical mass transfer coefficient

k s⁻¹ first order forward rate constant

k₋₁ s⁻¹ first order backward rate constant

R_HA0 [kmol.m⁻²s⁻¹] Initial rate of reaction

pK_a Acid Dissociation Constant

K_E Overall equilibrium extraction complexation constant

Z loading ratio

E_e Extraction Efficiency

[E]₀ [kmol.m⁻³]Initial Extractant Concentration of TBP

Subscript

org organic

aq aqueous

Novelity statement

The equilibrium for the reactive extraction of gallic acid with isoamyl alcohol is presented for the first time. Literature review reveals that although some equilibrium studies have been carried out, iso amyl alcohol have never been used.

Kinetic study is also presented for the first time. Results obtained from equilibrium and kinetic studies can be useful for design of extraction column.

Adsorption Isotherm Modeling has also been carried out for the extraction process of gallic acid.

Optimization by response surface methodology is also carried out for finding out the optimum operating parameters for the process.