Application of Central Composite Design in the Adsorption of Ca(II)‎ on Metakaolin Zeolite

Abstract EN

Metakaolin zeolite-A was synthesized from thermally activated kaolin clay and characterized by Fourier Transform Infrared Spectroscopy and X-Ray Diffraction Spectroscopy.

The effects of pH (2–10), contact time (10–180 min), initial concentration (5–120 mgL−1), and dosage (0.1–2 g) and their interactions were investigated using response surface methodology following a central composite design.

Optimum removal (87.70%) was obtained at pH 6, contact time 180 min, initial concentration 40.0 mgL−1, and adsorbent dosage 1.0 g by Excel Solver using the GRG solving method.

The adsorption data fitted best to the Langmuir model with correlation coefficient R2=0.993 and Chi-square value χ2=4.76.

The Freundlich isotherm gave a correlation coefficient R2=0.933 and χ2=37.91.

The adsorption process followed the pseudo-second-order model.

The calculated thermodynamic parameters showed that the adsorption process was endothermic and not thermodynamically spontaneous.

The studied zeolite-A can therefore be used as a promising adsorbent for the removal of Ca(II) ions from aqueous solutions.