Removal of nickel from water using rotating packed bed contactor: Parametric studies and mode of operations

Performance of rotating packed bed (RPB) contactor in the removal of nickel from water was investigated from two aspects: i) effect of operating parameters, and ii) effect of mode of operation. The results showed that the performance of RPB was highly governed by the rotational speed and activated carbon dosage. The increase in centrifugal force generated by the RPB from 200 rpm - 875 rpm was found to displace the activated carbon to the outer side of the RPB, which reduced the liquid flow path length and contact time between the packed bed and nickel solution and this reduced the removal efficiency. Nevertheless, a further increase in rotational speed from 875 rpm to 1200 rpm improved the removal efficiency as the enhancement in mass transfer process had outperformed the effect given by reduced path length. Higher activated carbon dosage also improved RPB performance by providing higher number of adsorption sites, as well as improving the packing density of the packed bed which minimized the reduced path length effect. The study also revealed that the mode of operation for a RPB contactor has crucial impact on the nickel adsorption. The removal efficiency was found to follow the sequence of multiple cycle mode operation batch mode operation > continuous mode operation, as a result of better contact time and consistent contact between the solution and the packed bed.