A Study Of Nickel And Cadmium Adsorption Using Granulated Charcoal Activated Carbon (Gcac)

Waste stream coming from industries which reaches water resources and soil is
spotted containing various contaminants such as heavy metals. This phenomenon is
potentially hazard to human and the environment as the metals not degrade into
harmless end products and tend to accumulate in living organisms, causing various
diseases and disorders. Adsorption is one of the methods for removing heavy metals
from contaminated effluents and the most effective among all. The present study was
undertaken to investigate ability of granulated charcoal activated carbon (GCAC) as
an adsorbent in adsorption process of removing nickel and cadmium ions from
aqueous solutions. The analyses of heavy metal removal are performed on three
operational parameters which are initial ion concentration, pH and agitation time.
The experiments were carried out at room temperature (25oC) and metal solutions
were agitated on a rotary shaker at constant speed of 240 rpm. BET surface area of
GCAC was found to be 898 m²/g. Batch adsorption test showed that the nickel and
cadmium uptake increase as agitation time increase. As initial metal ion
concentration increase, nickel adsorption percentage decrease and cadmium
adsorption percentage increase. Nickel adsorption percentage decreased as the nickel
ion concentration increases, the higher energy sites are saturated and adsorption
begins on lower energy sites, resulting in decreases in the adsorption
efficiency.Cadmium adsorption percentage increase due to the increase in the driving
force of the concentration gradient produced by the increase in the initial cadmium
concentration. The equilibrium time for both metals uptake were 120 minutes and
optimum initial metal concentration were 100 mg/L and 5 mg/L for cadmium and
nickel, respectively. Adsorption was found to be low at acidic pH and kept increasing
as pH increased. The highest cadmium and metal adsorptions were achieved at pH
10. At low pH, solution has high concentration of H+ ions compared to high pH
solution as it is acidic. Presence of high H+ ions in metal solutions created great
competition between H+ ions and Cd2+ ions for vacant adsorption sites of adsorbent.
The competitive adsorption results in low metal uptake by GCAC. The equilibrium
data fitted is more well fitted to Freundlich isotherm as the R-squared value of
Freundlich were higher than Langmuir’s which were 0.995 and 0.98 for nickel and
cadmium, respectively. This indicates that the cadmium and nickel adsorption are
multilayer adsorption on the GCAC surface.