Adsorption of Cd (II) Ions from Aqueous Solution Using Activated Carbon Prepared from Vitellaria paradoxa Shell

摘要

Activated carbon prepared from vitellaria paradoxa shell using ortho-phosphoric acid as activating agent was used for the removal of Cd (II) ions from aqueous solution. The adsorbent was characterized by some physicochemical and spectroscopic methods such as pH, point of zero charge (PZC), moisture content, iodine number, loss on ignition, bulk density, XRF, SEM and TEM. The pH and PZC of the sample were found to be 4.0 and 5.8 respectively. The adsorbent sample has moisture content of 5.22 ± 0.1%, iodine number of 256.50 ± 59%, loss on ignition of 10.71 ± 0.18% and bulk density of 0.84 ± 0.09%. The XRF analysis indicated that Ca, Si and Fe were major constituents in the adsorbent sample. The morphology of the adsorbents as revealed by SEM and TEM analysis results indicated good adsorptive characteristics of the adsorbent. The equilibrium adsorption of Cd (II) ions data were well fitted with Langmuir and Freundlich isotherms with correlation coefficient of 0.996 and 0.998 respectively. The kinetics study revealed that the experimental data fitted pseudo-second order kinetic better when compared to zero-order kinetics. Thermodynamics experiment indicated that the adsorption process was endothermic with ΔH value of +27.84 kJ/mol and ΔS of +0.993 kJ/molK and ΔG is negative at all temperature indicating the feasibility of the adsorption process.