Removal of the Pigment Congo Red from Synthetic Wastewater with a Novel and Inexpensive Adsorbent Generated from Powdered Foeniculum Vulgare Seeds

Abstract

In this research, powdered Foeniculum vulgare seed (FVSP) was treated separately with H2C2O4, ZnCl2, and a mixture of ZnCl2-CuS. The characteristics of the treated and untreated FVSP samples, as well as their abilities to eliminate Congo red (CR) from solutions, were investigated. The influences of the empirical circumstances on CR adsorption by the ideal adsorbent were studied. The thermodynamic, isothermal, and dynamic constants of this adsorption were also inspected. The ideal adsorbent was found to be the FVSP sample treated with a ZnCl2-CuS mixture, which eliminated 96.80% of the CR dye. The empirical outcomes proved that this adsorption was significantly affected by the empirical circumstances, and the second-order dynamic model as well as the Langmuir isotherm model fit the empirical data better than the first-order model and the Freundlich model. The values of Ea (15.3 kJ/mol) and ∆Ho (32.767 kJ/mol ≤ ∆Ho ≤ 35.495 kJ/mol) evidence that CR anions were endothermally adsorbed on Zn/Cu-FVSP via the ionic exchange mechanism. The superior Qmax values (434.78, 625.00, 833.33 mg/g), along with the cheapness and stability of the adsorbent used in this work, are evidence to confirm that this adsorbent will receive special interest in the field of contaminated water purification.