Tunisian date seed for removal of Alizarine Red S contained in wastewater: Box–Behnken design and modeling

Abstract

Tunisian date seed (TDS) powder was selected as a bioadsorbent material for eliminating Alizarin Red S (ARS) from wastewater. The Box–Behnken design (BBD) response surface methodology (RSM) was used to analyze various factors, including ARS concentration, pH, and adsorbent mass, to optimize the adsorption process. The resulting model proved highly effective in determining the optimal conditions for ARS removal, achieving a maximum adsorption capacity of 24.57 mg g⁻¹. The use of TDS as an adsorbent demonstrated excellent efficiency in treating wastewater containing high concentrations of ARS. Thermodynamic analysis revealed that the adsorption process is non-spontaneous, exothermic, and occurs in an organized manner. Additionally, several kinetic models were evaluated to determine the adsorption kinetics, with the pseudo-second-order model showing the best correlation with experimental data. For thermodynamic modeling, various isotherm models were tested, and the Langmuir–Freundlich model was identified as the most suitable for accurately describing the experimental isotherms. The optimal conditions determined using response surface methodology (RSM) were pH = 6.14, ARS concentration of 200 mg L⁻¹, and adsorbent mass of 0.21 g.