Adsorption of Mn(II) and Co(II) ions from aqueous solution using Maize cob activated carbon: Kinetics and Thermodynamics Studies|
ADEBAYO, G. B.; ADEGOKE, H. I.; JAMIU, W.; BALOGUN, B. B. & JIMOH, A. A.
The adsorption of Mn(II) and Co(II) ions from aqueous solution was
investigated using batch adsorption experiment at room temperature. The effect of pH,
contact time, metal ion concentration and temperature were evaluated. The residual
concentrations of the metal ions were determined by atomic absorption spectrophotometer.
The results showed that maximum removal of Mn(II) and Co(II) ions occurred at pH 9.
Some physico-chemical and spectroscopic characterization of the adsorbents were done such
as moisture content, ash content, bulk density, volatile matter, iodine number, point of zero
charge (PZC), XRF, and FTIR. The moisture and ash content of MCAC adsorbent were
found to be 9.85±0.06 and 5.5±0.1% respectively. The bulk density was found to be
0.37±0.01g/m3, iodine number of 367.66±30 mg/g and PZC of 6.8. The SEM micrograph
shows particle grains and jelly like rough surfaces, FTIR analysis results show different
functional group in the MCAB adsorbent such as O-H, C=O, and C=C stretching. Kinetic
study shows that the pseudo-second order kinetic model best described the adsorption of
metal ions. The equilibrium data fitted Langmuir, Freundlich and Temkin adsorption
isotherms, in each case, the Langmuir model appears to have better regression coefficients
than the Freundlich and Temkin. Thermodynamics investigation showed that Gibb’s free
energy change (ΔG) was negative indicating that the adsorption of Mn(II) and Co(II) ions by
maize cob activated carbon were feasible and spontaneous. The positive value of enthalpy
change (ΔH) implies that the reaction was endothermic while positive value of entropy
change (ΔS) implies an irregular increase in the randomness at the solid/solution interface of
the adsorbent during the adsorption process.
Adsorption; Heavy metals; Kinetics; Thermodynamics