Kinetic study of adsorption of copper (II) ion from aqueous solution using rice hull ash

Ash prepared from calcinating rice hull at 500 °C under 20 mL air/s for 50 min was used to remove copper (II) ion from aqueous solution. The rice hull ash (RHA) thus produced was found to be efficient in removing copper (II) ion from aqueous solution. The kinetic study of the adsorption experiment indicated that both the rate of removal and the removal at equilibrium were increased with decreasing RHA dosage or increasing initial copper concentration. The rate of removal and the removal at equilibrium were found to remain unchanged when pH was increased from 2.5 to 5.4 but were increased when pH was increased from 5.4 to 6.2. The stroke speed and adsorption temperature, however, were found to have no effect on the rate of removal and the removal at equilibrium in the range studied. The overall adsorption process was observed to be controlled by the physisorption step and the pseudo-second-order rate equation described the overall process suitably. An empirical relationship between removal of Cu2+ and adsorption time was also determined.