Analytical Sciences

Pb(II), Cu(II) and Cd(II) Removal through Untreated Rice Husk; Thermodynamics and Kinetics

Maria Giovanna GUISO, Giancarla ALBERTI, Giovanni EMMA, Maria PESAVENTO, and Raffaela BIESUZ

Dipartimento di Chimica, Università degli Studi di Pavia, via Taramelli 12-27100 Pavia, Italy

The sorption properties of rice husk towards Cu(II), Cd(II) and Pb(II) were studied. The sorption isotherms are described by the Langmuir equation, and Pb(II) shows a higher affinity for rice husk compared to Cu(II) and Cd(II) under the same conditions. The kinetics of sorption obeys to a pseudo second-order equation for all metals. The sorption profiles as a function of the pH were used to characterize the stoichiometry of the sorption reaction. The competition for metal complexation by any ligand in solution is also accounted for. Upon increasing the ionic strength, the sorption curves of Pb(II) move to basic pH; this shift can be explained by considering the effect of nitrate complexes on the free metal ion concentration, since KNO₃ is used as the ionic medium. An attempt to employ rice husk in a dynamic system is presented.

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