This work evaluates the potential of Phyllanthus debilis for the adsorption of Zn2+ and Ni2+ ions using synthetic solutions.
Adsorption experiments were performed in order to examine the effect of pH, contact time, biomass concentration and initial
metal ion concentration in the removal process, in a batch mode. The results revealed that the adsorption is highly pH dependent.
The adsorption of Zn2+ and Ni2+ ions were concentration dependent and increased from 2.446 to 8.688 mg/g for Zn2+ and 2.26 to
7.744 mg/g for Ni2+ with an increase of concentration from 25 to 100 mg/L at pH 5. The adsorption mechanism was examined by
FTIR technique and SEM. Isotherm and kinetic studies were carried out for the adsorption of Zn2+ and Ni2+ ions from aqueous
solution using P. debilis at different initial metal ion concentration. Isotherms results were amply fitted by the Langmuir model,
determining a monolayer maximum adsorption capacity (qm) of P. debilis biomass equal to 8.97 mg g-1 and 11.39 mg g-1 for Zn2+
and Ni2+ ions respectively, and suggesting a functional group limited adsorption process. In order to evaluate kinetic parameters
for Zn2+ and Ni2+ adsorption, Lagergren's first-order, pseudo-second-order, Elovich kinetic model and intra-particle diffusion
models were explored. It was found that the pseudo-second order kinetic model fitted very well the experimental data. The rate
determining step is described by intra-particle diffusion model.