Study of Cr (III) biosorption in a fixed-bed column.

This research analyzes the potential use of the olive stone as a low-cost biosorbent for Cr (III) from aqueous solutions in a continuous system. First, experiments were carried out in fixed-bed column to test the influence of various parameters on breakthrough and saturation time. The breakthrough and saturation time increase with the decrease of the flow rate. The same effect is shown when the bed depth is increased. The olive stone sorption capacity, q(e), increases as the inlet Cr (III) concentration increases until a value close to 0.800 mg/g is reached, then q(e) remains constant. Column data obtained at different conditions were described using the Adams-Bohart, Thomas, Yoon and Nelson, and Dose-Response models. The breakthrough curve prediction by the Adams-Bohart and Dose-Response models were found to be very satisfactory. In particular, the Adams-Bohart model can be used to represent the initial region of breakthrough curve, whereas the Dose-Response model is the one which best reproduces the whole curve for all the inlet Cr (III) concentrations used. Finally, a study of pH evolution was carried out. The pH increases at the beginning, subsequently decreasing as time passes until practically reaching the initial value.