Abstract:
Chemically prepared activated carbon derived from Gmelina aborea leaves (GALAC) were used as adsorbent for
the removal of Rhodamine B (Rh–B) dye from aqueous solutions. The adsorptive characteristics of activated
carbon (AC) prepared from Gmelina aborea leaves (GAL) were studied using SEM, FTIR, pH point of zero charge
(pHpzc) and Boehm Titration (BT) techniques respectively. The effects of pH, contact time, initial dye concentration
and solution temperature were also examined. Experimental data were analyzed using four different
isotherm models: Langmuir, Freundlich, Temkin and Dubinin-Radushkevich. Four adsorption kinetic models:
Pseudo-first-order (PFO), Pseudo-second-order (PSO), Elovich and Intraparticle diffusion models to establish the
kinetics of adsorption process. The RhB dye adsorption on GALAC was best described by Langmuir isotherm
model with maximum monolayer coverage of 1000 mg g 1 and R2 value of 0. 9999. The EDX analysis revealed
that GALAC contained 82.81% by weight and 91.2% by atom of carbon contents which are requisites for high
adsorption capacity. Adsorption kinetic data best fitted the PSO kinetic model. Thermodynamic parameters obtained
for GALAC are (ΔGo ranged from -22.71 to -18.19 kJmol-1; ΔHo: 1.51 kJmol-1; and ΔSo: 0.39 kJmol-1
K 1respectively) indicating that the RhB dye removal from aqueous solutions by GALAC was spontaneous and
endothermic in nature. The cost analysis established that GALAC is approximately eleven times cheaper than CAC
thereby providing a saving of 351.41USD/kg. Chemically treated GAL was found to be an effective absorbent for
the removal of RhB dye from aqueous solution.
