Research Article
Mahamadi C, Mupa M and Jackson
Abstract
The adsorption of Pb (II), Cu (II) and Cd (II) on immobilized water pennywort-Hydrocotyle ranunculoides was investigated in batch and continuous flow systems. Physical characterization of adsorbent was performed using fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). Analysis of batch sorption data using single component and competitive Langmuir models showed that maximum equilibrium sorption capacities for single-metal systems followed the trend (mg/g): Pb(II) (22.25)>Cu(II) (12.55)>Cd(II) (11.45). Mutual interference was probed using normalised equilibrium adsorption capacities, qe'/qe, where the prime indicates the presence of the other metal ion. The results showed that removal of Cu (II) and Cd(II) ions was severely suppressed in the presence of Pb(II) whereas the removal of Pb(II) in the presence of Cu(II) and Cd(II) ions was still effective. Adams-Bohart and Thomas models were used to study the effect of important parameters: bed depth (1.5-2.5 cm), flow rate (2-20 ml/min) and initial metal concentration (10-100 mg/l). It was shown that the Thomas model provided a better fit to the experimental data indicating that mass transfer, i.e. external diffusion was not the rate limiting steps. In conclusion, immobilised H. ranunculoides proved to be a potential biosorbent for the removal of heavy metal ions from aquatic environments.