Abstract
Turbinaria decurrens immobilized in sodium alginate showed increasing intraparticular diffusion of lead, stability of the metal binding, and affinity for lead. Equilibrium lead concentrations were attained after 9 h. The maximum lead uptakes were 1.14, 1.35, and 1.79 mmol g(-1), respectively, for alginate xerogels, free alga, and immobilized alga. The order of maximum lead uptake for different biosorbents was immobilized alga > free alga > alginate xerogels. Scanning electron microscopy (SEM) and energy dispersive X-ray microanalysis showed a uniform distribution of lead on the alginate surface. Fourier transform infrared spectroscopy (FTIR) showed that the main bands modified after lead uptake were those corresponding to hydroxyl and carboxyl stretching. The immobilized beads could be repeatedly used with high efficiency. T. decurrens immobilized in alginate xerogels constitutes an excellent biosorbent for lead, sometimes surpassing the biosorption performance of alginate alone and even the free alga.