Equilibrium Isotherm Studies for the Multicomponent Adsorption of Lead, Zinc, and Cadmium onto Indonesian Peat

This study evaluates the potential of Indonesian peat to sequester Pb, Cd, and Zn in single-, double-, and triple-solute systems. The adsorption isotherms of Pb, Cd, and Zn onto peat in single-solute and multisolute systems were simulated using the Langmuir two-site model satisfactorily. The model and experimental data of binary and ternary systems demonstrated that the presence of the secondary metal ions in the system resulted in a decrease in the sorption capacity of the primary metal, mainly because of the competitive effects of metals for adsorption sites. The metal adsorption follows the order of sequence Pb > Cd > Zn for both single-solute and multisolute systems. A three-dimensional representation of the total metal uptake in binary systems showed a good agreement with the corresponding experimental data. In addition to ion exchange, a surface adsorption -complexation mechanism must be involved in the sorption mechanism of metal ions. Fourier transform IR results confirm that the carboxyl functional groups participated in metal binding. Desorption experiments revealed that greater than 90% of Pb, Cd, and Zn can be eluted from the peat. In addition, results suggested that the desorption efficiency decreased with an increase in the adsorbed metal concentration.