Catalpa speciosa tree leave was used to remove Pb(II) from aqueous solutions. Doehlert design applied to find an appropriate model which leads to determination of the optimum conditions. The multi-response optimization of Pb(II) removal process has been carried out using desirability function approach. The optimum conditions of Pb(II) removal process have been found as: pH=4.43, s=0.07 g and Cm=104 mg L-1 and respectively the confirmed responses by experiment were R%= 86 and q= 14.7 mg g-1. The potentiometric titration, pHPZC , FT-IR spectroscopy, X-ray diffraction and scanning electron microscopy (SEM) techniques were used to characterize the biosorbent active sites.
