On the use of a natural peat for the removal of Cr(VI) from aqueous solutions

A natural peat has been used as an adsorbent for the removal of hexavalent chromium from aqueous solution. The peat was firstly characterized in terms of particle size and chemical composition (ash content, pH of the point of zero charge, FT-IR and thermal analysis). Next, the kinetic and equilibrium aspects of the adsorption of Cr(VI) by this adsorbent were studied. The kinetic data were satisfactorily fitted to a kinetic law of partial order in C equal to one. The specific adsorption rates are around 10−4 s−1, increasing as temperature does. A noticeable influence of diffusion on the global adsorption process has been demonstrated. Finally, the equilibrium isotherms were satisfactorily fitted to a previously proposed model. The adsorption capacity of Cr(VI) was similar to some other previously reported and the affinity of Cr(VI) towards the active sites of the adsorbent increases as temperature rises.

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► A natural peat has been characterized and used for the removal of Cr(VI).
► The adsorption of Cr(VI) has been analyzed from the kinetic and equilibrium standpoints.
► The adsorption kinetics is remarkably influenced by the diffusion of the adsorbate.
► The equilibrium isotherms suggest the occurrence of a two-stage adsorption process.
► Experimental data have been satisfactorily fitted to the proposed adsorption models.