Taguchi design-based enhancement of heavy metals bioremoval by agroindustrial waste biomass from artichoke

The Taguchi method of designing experiments is based on a system of tabulated designs (arrays) that enables the maximum number of variables to be estimated in a neutral (orthogonal) balanced manner with a minimum number of experimental sets. Heavy metals remediation of aqueous streams is of special concern due to its highly toxic and persistent nature. Taguchi approach was used for enhanced bioadsorptive removal of Pb(II), Cu(II) and Cd(II) from aqueous solutions using agroindustrial waste biomass from globe artichoke as inexpensive sorbent. Sorbent biomass was characterized as to its chemical composition by infrared spectroscopy (FTIR), revealing the presence of hydroxyl, carboxyl, sulphonic and amine functional groups. Ranks of four factors (pH, temperature, sorbent dosage and initial metal concentration) at three levels each, in a L9 array were conducted, in batch sorption tests, for the individual metal ions of concern. The sorption capacity (q_e) values were transformed into an accurate signal-to-noise (S/N) ratio for a "higher is better" response. The best conditions for individual heavy metal sorption were determined reaching up to 86.2 mg·g^-1 for Pb, 35.8 mg·g^-1 for Cd and 24.4 mg·g^-1 for Cu. This paper also discusses the equilibria and kinetic aspects of the sorption process. Sorption isotherms were successfully described by the Sips model. In addition, the experimental data showed that the uptake kinetic profiles of the three metal ions closely fitted the pseudo-second order model. Conclusively, the agroindustrial waste biomass from globe artichoke represents a potentially viable sorbent for the bioremoval of Pb(II), Cu(II) and Cd(II) ions from aqueous systems.