Adsorption of Congo Red Dye from Aqueous Solution using ZnO and Al2O3/ZnO Composite: Isotherm, Kinetic and Thermodynamic Data

Abstract

Herein, an adsorption study of congo red (CR) dye onto ZnO and Al2O3/ZnO is reported. ZnO was prepared using conventional chemicals by co-precipitation method and Al2O3 used in the composite was prepared through recycling of aluminium waste. Information about the materials was obtained through spectroscopic techniques. A batch adsorption method was used to obtain the adsorption data from which isotherm, kinetic and thermodynamic parameters were obtained. The result of the adsorbents characterisation revealed the expected properties of the prepared materials. The adsorption capacities at 250 mg/L of CR dye were 24.33 mg/g and 24.57 mg/g for ZnO and Al2O3/ZnO respectively. The isotherm study of the adsorption process revealed that Langmuir model fitted best the adsorption data with monolayer adsorption capacities (qm) of 27.67 mg/g and 33.39 mg/g for ZnO and Al2O3/ZnO respectively. The adsorption was rapid within the first 15 min and the equilibrium was reached at 45 min. The kinetic study followed a pseudo-second-order model with the rate constant of 0.049 and 0.093 g.mg-1.min-1 for ZnO and Al2O3/ZnO respectively. Experimentally, the process was endothermic and was supported by the positive values of enthalpy (ΔH) with positive values of entropy (ΔS). The change in free energy (ΔG) is negative at all temperatures studied, indicating spontaneity but more spontaneous for Al2O3/ZnO than ZnO. The adsorption of CR dye from an aqueous solution onto ZnO as an adsorbent can be slightly improved upon by the introduction of Al2O3 to form Al2O3/ZnO composite.

Adsorptive Performance of Termite Mound Clay for Removal of Eosin Yellow Dye from Aqueous Solution

“…Where C o , C e and C t (mg/L) are the initial concentration, concentrations at equilibrium and concentration at any time (t) respectively; q e and q t (mg/L) are the quantities adsorbed at equilibrium and any time respectively; V (L) is the volume of the dye solution and m (g) is the mass of the adsorbent used (Bello et al, 2022).…”

“…Consequently, dye is one of the major pollutants of great environmental concern (Bello et al, 2022;Iqbal et al, 2021). Since these dyes are extremely harmful to microbial populations and even carcinogenic to mammals, it is vital to remove them from industrial effluents prior to their discharge into water bodies (Kandisa and Saibaba, 2016).…”

Adsorption of lead and chromium ions from electroplating wastewater using plantain stalk modified by amorphous alumina developed from waste cans

“…Banana peel-activated carbon coated with Al 2 O 3 -chitosan was fabricated as an adsorbent for the removal of Pb(II) (99.9% removal), and Cd(II) (99.9% removal) ions from wastewater 27 . Also, the removal of congo red dye from an aqueous solution using Al 2 O 3 /ZnO composite was achieved by the adsorption process at 97.35% removal 28 .…”