Effect of the Acid Treatment of Olive Stone on the Biosorption of Lead in a Packed-Bed Column

Biosorption of lead(II) ions from aqueous solutions by untreated, HCl-treated, H 2 SO 4 -treated, HNO 3 -treated, and H 3 PO 4 -treated olive stone was studied in a continuous-upflow packed-bed column. The effect of acid treatment on the lead biosorption capacity of olive stone was determined by evaluating the breakthrough curves obtained at different inlet concentrations of lead, changing from 10 to 150 mg/L. Results indicated that the treatment of olive stone with inorganic acids improves significantly its capacity to removal lead ions from aqueous solution. Finally, the Adams−Bohart, Thomas, Yoon and Nelson, and dose−response models were used to analyze the experimental data to determine the characteristic parameters of the column useful for process design. In particular, the dose−response model was able to simulate breakthrough curves at lower and higher time periods with high correlation coefficients. The maximum column biosorption capacity predicted by this model at an inlet lead concentration of 150 mg/L was 1.31 mg/g for unmodified olive stone and 14.03 mg/g for olive stone treated by H 2 SO 4 . Also, the pH variations during the sorption process have been reported.