Analysis of Thermodynamics, Kinetics andEquilibrium Isotherm on Fe3+/Fe2+ Adsorptiononto Palm Kernel Shell Activated Carbon(PKSAC): A Low-cost Adsorbent

摘要

Adsorption of Fe~(3+)/Fe~(2+) from a polluted shallow well water onto a palm kernel shell activated carbon (PKSAC) has been studied. Batch experiment was adopted to study the Removal efficiency of Fe~(3+)/Fe~(2+) on varying contact time, temperature, adsorbent loading and concentrations. Equilibrium isotherm and kinetic were also studied. Removal efficiency progressed with contact time till the peak adsorption time of 100 minutes when the efficiency remained at equilibrium. Also, removal efficiency got to equilibrium at the peak values of 80oC, 4.8g and 12.5mg/l for temperature, adsorbent loading and concentration variations respectively. The adsorption isotherm models fitted the isotherm data got at 25oC, 40oC and 80oC in this order; Langmuir > Temkin>Freunlich. The dimensionless separation factor of 0.012, 0.017 and 0.015 for 25oC, 40oC and 80oC respectively confirmed favorable adsorption of Fe~(3+)/Fe~(2+) on the PKSAC adsorbent. Langmuir adsorption capacity increased from 203.9mg Fe~(3+)/Fe~(2+)/g to 389.3 mg Fe~(3+)/Fe~(2+)/g when the temperature increased from 25oC to 40oC but decreased to 308.1 mg Fe~(3+)/Fe~(2+)/g at temperature of 80oC. The kinetic models described the kinetic study data got at 25oC, 40oC and 80oC as follows; power-function>second-order>Elovick>intra-diffusion>first-order kinetics. Mass transfer through liquid film diffusion controlled the adsorption of Fe~(3+)/Fe~(2+) onto PKSAC. Negative values of the Thermodynamic parameters (a??G^(o ), a??H^o and a??S^o) got at various temperature values showed favorability of adsorption of Fe~(3+)/Fe~(2+) onto PKSAC. It is therefore concluded that PKSAC removed Fe~(3+)/Fe~(2+) from aqueous solution.