Kinetics of Hg(II) adsorption and desorption in calcined mussel shells

The potential use of calcined mussel shells to purify water contaminated with mercury was evaluated. The Hg(II) adsorption and desorption kinetics were studied in batch-type and stirred-flow chamber experiments. The adsorption/desorption experiments revealed some differences between the batches of shells used. The batch of shells that displayed the greatest capacity to adsorb Hg(II), via a highly irreversible reaction, also contained more Fe and Al than the other batches. The results of the stirred-flow chamber experiments indicated a high degree of irreversibility in the process of Hg(II) adsorption in the mussel shell, and that Hg(II) was rapidly retained. The results of these experiments also revealed that the efficiency of depuration differed depending on the length of time that the system was used: when the system was operated for 55 min, depurating 162 mL of inflowing water g−1 mussel shell, a 90% reduction in the initial concentration of Hg(II) was obtained; use of the system for 90 min, depurating 265 mL water g−1 mussel shell, produced a 75% reduction in the initial Hg(II), and use of the system for 162.5 min, depurating 487 mL of water g−1 mussel shell, resulted in a 50% reduction in the initial Hg(II).