Removal of Congo Red from Aqueous Solutions Using Fly Ash Modified with Hydrochloric Acid
Ebelegi Newton Augustus
Department of Chemical Sciences, Niger Delta University, Wilberforce Island, Bayelsa State, Nigeria
Angaye Seimokumo Samuel
Department of Chemical Sciences, Niger Delta University, Wilberforce Island, Bayelsa State, Nigeria
Ayawei Nimibofa *
Department of Chemical Sciences, Niger Delta University, Wilberforce Island, Bayelsa State, Nigeria
Wankasi Donbebe
Department of Chemical Sciences, Niger Delta University, Wilberforce Island, Bayelsa State, Nigeria
*Author to whom correspondence should be addressed.
Abstract
The adsorption of Congo Red dye onto fly ash modified with various concentrations of Hydrochloric acid (HCFA-4,HCFA-3,HCFA-2 and HCFA-1)was studied. The effect of contact time and concentration were investigated using a batch adsorption technique. The experimental data fits well with the Freundlich isotherm due to high correlation coefficients and this may be attributed to heterogeneous distribution of active sites and multilayer adsorption, while the dynamic data is best described by the pseudo-second-order kinetic model which suggests that Congo Red adsorption onto fly ash modified with Hydrochloric acid appeared to be controlled by a chemisorption process. Fly ash modified with 2 M Hydrochloric acid HCFA-2 exhibited the highest adsorption capacity (KF=7.82) followed by HCFA-3 (KF = 0.74), HCFA (KF = 0.069) and HCFA-1 had the least adsorption capacity (KF =0.004). Adsorption of Congo Red dye onto fly ash modified with various concentration of Hydrochloric acid was spontaneous since Gibbs free energy of adsorption was negative in all cases.
Keywords: Fly ash, isotherms, hydrochloric acid, Congo Red, adsorption kinetics