Recebido em 13/5/10; aceito em 12/1/11; publicado na web em 29/3/11In this study Ucides cordatus crab shells were utilized as Fe (II) sorbent as material of low cost and simple preparation. Values of pH of standard solution, biosorbent mass, particles size, contact time (t c ) and initial concentration of the standard solution were optimized. The best conditions were pH = 2.00, t c = 840 min and M c = 0.25 g. The kinetic pseudo first-order model displayed the best description of the adsorption process and the equilibrium study showed that the Langmuir model better describes the adsorption of the Fe (II). There is great affinity between the Fe (II) and the biosorbent.
The indirect titration of Fe(III) ion with oxidizing agent is a good example of the application of Gran's method to a redox reaction because the Gran curve doesn't present linearity deviations as other redox systems do. It seems as if previous stages of reduction and rinsing of the reducing column leave the solution to be titrated with a high ionic strength, which does not vary considerably during the titration.
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